From “The Big Think” : “3 new studies indicate a conflict at the heart of cosmology”

From “The Big Think”

2.1.23
Don Lincoln

The Universe isn’t as “clumpy” as we think it should be.

Credit: NASA.

Key Takeaways

Telescopes are essentially time machines. As we examine galaxies that are at greater and greater distances from the Earth, we are looking further and further back in time. A new series of studies that examine the “clumpiness” of the Universe indicates that there might be a conflict at the heart of cosmology. The Big Bang theory is still sound, but it may need to be tweaked.

A series of three scientific papers describing the expansion history of the Universe is telling a confusing tale, with predictions and measurements slightly disagreeing.

While this disagreement isn’t considered a fatal disproof of modern cosmology, it could be a hint that our theories need to be revised.

PRD “Joint analysis of DES Year 3 data and CMB lensing from SPT and Planck I: Construction of CMB Lensing Maps and Modeling Choices”
PRD “Joint analysis of DES Year 3 data and CMB lensing from SPT and Planck II: Cross-correlation measurements and cosmological constraints”
PRD “Joint analysis of DES Year 3 data and CMB lensing from SPT and Planck III: Combined cosmological constraints”

Creation stories, both ancient and modern

Understanding exactly how the world around us came into existence is a question that has bothered humanity for millennia. All around the world, people have devised stories — from the ancient Greek legend of the creation of the Earth and other primordial entities from Chaos (as first written down by Hesiod) to the Hopi creation myth (which describes a series of different kinds of creatures being created, eventually ending up as humans).

In modern times, there are still competing creation stories, but there is one that is grounded in empiricism and the scientific method: the idea that about 13.8 billion years ago, the Universe began in a much smaller and hotter compressed state, and it has been expanding ever since then. This idea is colloquially called the “Big Bang,” although different writers use the term to mean slightly different things. Some use it to refer to the exact moment at which the Universe came into existence and began to expand, while others use it to refer to all moments after the beginning. For those writers, the Big Bang is still ongoing, as the expansion of the Universe continues.

The beauty of this scientific explanation is that it can be tested. Astronomers rely on the fact that light has a finite speed, which means that it takes time for light to cross the cosmos. For example, the light we see as the Sun shining was emitted eight minutes before we see it. Light from the nearest star took about four years to get to Earth, and light from elsewhere in the cosmos can take billions of years to arrive.

The telescope as a time machine

Effectively, this means that telescopes are time machines. By looking at more and more distant galaxies, astronomers are able to see what the Universe looked like in the distant past. By stitching together observations of galaxies at different distances from the Earth, astronomers can unravel the evolution of the cosmos.

The recent measurements use two different telescopes to study the structure of the Universe at different cosmic epochs. One facility, called the South Pole Telescope (SPT), looks at the earliest possible light, emitted a mere 380,000 years after the Universe began.

South Pole Telescope SPTPOL. The SPT collaboration is made up of over a dozen (mostly North American) institutions, including The University of Chicago; The University of California Berkeley; Case Western Reserve University; Harvard/Smithsonian Astrophysical Observatory; The University of Colorado-Boulder; McGill University(CA); The University of Illinois, Urbana-Champaign; The University of California-Davis; Ludwig Maximilians Universität München(DE); DOE’s Argonne National Laboratory; and The National Institute for Standards and Technology. It is funded by the National Science Foundation

At that time, the Universe was 0.003% its current age. If we consider the current cosmos to be equivalent to a 50-year-old person, the SPT looks at the Universe when it was a mere 12 hours old.

The second facility is called the Dark Energy Survey (DES).
___________________________________________________________________
The Dark Energy Survey

Dark Energy Camera [DECam] built at The DOE’s Fermi National Accelerator Laboratory.

NOIRLab National Optical Astronomy Observatory Cerro Tololo Inter-American Observatory (CL) Victor M Blanco 4m Telescope which houses the Dark-Energy-Camera – DECam at Cerro Tololo, Chile at an altitude of 7200 feet.

NOIRLabNSF NOIRLab NOAO Cerro Tololo Inter-American Observatory(CL) approximately 80 km to the East of La Serena, Chile, at an altitude of 2200 meters.

Timeline of the Inflationary Universe NASA WMAP LAMBDA – ΛCDM Model of Cosmology

The Dark Energy Survey is an international, collaborative effort to map hundreds of millions of galaxies, detect thousands of supernovae, and find patterns of cosmic structure that will reveal the nature of the mysterious dark energy that is accelerating the expansion of our Universe. The Dark Energy Survey began searching the Southern skies on August 31, 2013.

According to Albert Einstein’s Theory of General Relativity, gravity should lead to a slowing of the cosmic expansion. Yet, in 1998, two teams of astronomers studying distant supernovae made the remarkable discovery that the expansion of the universe is speeding up.

Nobel Prize in Physics for 2011 Expansion of the Universe

Saul Perlmutter (center) [The Supernova Cosmology Project] shared the 2006 Shaw Prize in Astronomy, the 2011 Nobel Prize in Physics, and the 2015 Breakthrough Prize in Fundamental Physics with Brian P. Schmidt (right) and Adam Riess (left) [The High-z Supernova Search Team] for providing evidence that the expansion of the universe is accelerating.

4 October 2011

The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Physics for 2011

with one half to

Saul Perlmutter
The Supernova Cosmology Project
The DOE’s Lawrence Berkeley National Laboratory and The University of California-Berkeley,

and the other half jointly to

Brian P. Schmidt
The High-z Supernova Search Team, The Australian National University, Weston Creek, Australia.

and

Adam G. Riess
The High-z Supernova Search Team,The Johns Hopkins University and The Space Telescope Science Institute, Baltimore, MD.
Written in the stars

“Some say the world will end in fire, some say in ice…” *

What will be the final destiny of the Universe? Probably it will end in ice, if we are to believe this year’s Nobel Laureates in Physics. They have studied several dozen exploding stars, called supernovae, and discovered that the Universe is expanding at an ever-accelerating rate. The discovery came as a complete surprise even to the Laureates themselves.

In 1998, cosmology was shaken at its foundations as two research teams presented their findings. Headed by Saul Perlmutter, one of the teams had set to work in 1988. Brian Schmidt headed another team, launched at the end of 1994, where Adam Riess was to play a crucial role.

The research teams raced to map the Universe by locating the most distant supernovae. More sophisticated telescopes on the ground and in space, as well as more powerful computers and new digital imaging sensors (CCD, Nobel Prize in Physics in 2009), opened the possibility in the 1990s to add more pieces to the cosmological puzzle.

The teams used a particular kind of supernova, called Type 1a supernova. It is an explosion of an old compact star that is as heavy as the Sun but as small as the Earth. A single such supernova can emit as much light as a whole galaxy. All in all, the two research teams found over 50 distant supernovae whose light was weaker than expected – this was a sign that the expansion of the Universe was accelerating. The potential pitfalls had been numerous, and the scientists found reassurance in the fact that both groups had reached the same astonishing conclusion.

For almost a century, the Universe has been known to be expanding as a consequence of the Big Bang about 14 billion years ago. However, the discovery that this expansion is accelerating is astounding. If the expansion will continue to speed up the Universe will end in ice.

The acceleration is thought to be driven by dark energy, but what that dark energy is remains an enigma – perhaps the greatest in physics today. What is known is that dark energy constitutes about three quarters of the Universe. Therefore the findings of the 2011 Nobel Laureates in Physics have helped to unveil a Universe that to a large extent is unknown to science. And everything is possible again.

*Robert Frost, Fire and Ice, 1920
___________________________________________________________________
To explain cosmic acceleration, cosmologists are faced with two possibilities: either 70% of the universe exists in an exotic form, now called Dark Energy, that exhibits a gravitational force opposite to the attractive gravity of ordinary matter, or Albert Einstein’s Theory of General Relativity must be replaced by a new theory of gravity on cosmic scales.

The Dark Energy Survey is designed to probe the origin of the accelerating universe and help uncover the nature of Dark Energy by measuring the 14-billion-year history of cosmic expansion with high precision. More than 400 scientists from over 25 institutions in the United States, Spain, the United Kingdom, Brazil, Germany, Switzerland, and Australia are working on the project. The collaboration built and is using an extremely sensitive 570-Megapixel digital camera, DECam, mounted on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory, high in the Chilean Andes, to carry out the project.

Over six years (2013-2019), the Dark Energy Survey collaboration used 758 nights of observation to carry out a deep, wide-area survey to record information from 300 million galaxies that are billions of light-years from Earth. The survey imaged 5000 square degrees of the southern sky in five optical filters to obtain detailed information about each galaxy. A fraction of the survey time is used to observe smaller patches of sky roughly once a week to discover and study thousands of supernovae and other astrophysical transients.
___________________________________________________________________
This is a very powerful telescope located on a mountain top in Chile. Over the years, it has surveyed about 1/8 of the sky and photographed over 300 million galaxies, many of which are so dim, they are about one-millionth as bright as the dimmest stars visible to the human eye. This telescope can image galaxies from the current day to as far back as eight billion years ago. Continuing with the analogy of a 50-year-old individual, DES can take pictures of the Universe starting when it was 21 years old up until the present. (Full disclosure: Researchers at Fermilab, where I also work, carried out this study — but I did not participate in this research.)

As light from distant galaxies travels to Earth, it can be distorted by galaxies that are closer to us. By using these tiny distortions, astronomers have developed a very precise map of the distribution of matter in the cosmos. This map includes both ordinary matter, of which stars and galaxies are the most familiar examples, and dark matter, which is a hypothesized form of matter that neither absorbs nor emits light. Dark matter is only observed through its gravitational effect on other objects and is thought to be five times more prevalent than ordinary matter.
__________________________________
Dark Matter Background
Fritz Zwicky discovered Dark Matter in the 1930s when observing the movement of the Coma Cluster., and Vera Rubin a Woman in STEM, denied the Nobel, some 30 years later, did most of the work on Dark Matter.

Fritz Zwicky.

Coma cluster via NASA/ESA Hubble, the original example of Dark Matter discovered during observations by Fritz Zwicky and confirmed 30 years later by Vera Rubin.

In modern times, it was astronomer Fritz Zwicky, in the 1930s, who made the first observations of what we now call dark matter. His 1933 observations of the Coma Cluster of galaxies seemed to indicated it has a mass 500 times more than that previously calculated by Edwin Hubble. Furthermore, this extra mass seemed to be completely invisible. Although Zwicky’s observations were initially met with much skepticism, they were later confirmed by other groups of astronomers.

Thirty years later, astronomer Vera Rubin provided a huge piece of evidence for the existence of dark matter. She discovered that the centers of galaxies rotate at the same speed as their extremities, whereas, of course, they should rotate faster. Think of a vinyl LP on a record deck: its center rotates faster than its edge. That’s what logic dictates we should see in galaxies too. But we do not. The only way to explain this is if the whole galaxy is only the center of some much larger structure, as if it is only the label on the LP so to speak, causing the galaxy to have a consistent rotation speed from center to edge.

Vera Rubin, following Zwicky, postulated that the missing structure in galaxies is dark matter. Her ideas were met with much resistance from the astronomical community, but her observations have been confirmed and are seen today as pivotal proof of the existence of dark matter.

Astronomer Vera Rubin at the Lowell Observatory in 1965, worked on Dark Matter (The Carnegie Institution for Science).

Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970.

Vera Rubin measuring spectra, worked on Dark Matter(Emilio Segre Visual Archives AIP SPL).

Dark Matter Research

Super Cryogenic Dark Matter Search from DOE’s SLAC National Accelerator Laboratory at Stanford University at SNOLAB (Vale Inco Mine, Sudbury, Canada).

LBNL LZ Dark Matter Experiment xenon detector at Sanford Underground Research Facility Credit: Matt Kapust.

Lambda Cold Dark Matter Expansion ΛCDM of the Universe. Credit Alex Mittelmann Coldcreation.

DAMA at Gran Sasso uses sodium iodide housed in copper to hunt for dark matter LNGS-INFN.

Yale HAYSTAC axion dark matter experiment at Yale’s Wright Lab.

DEAP Dark Matter detector, The DEAP-3600, suspended in the SNOLAB (CA) deep in Sudbury’s Creighton Mine.

The LBNL LZ Dark Matter Experiment Dark Matter project at SURF, Lead, SD.

DAMA-LIBRA Dark Matter experiment at the Italian National Institute for Nuclear Physics’ (INFN’s) Gran Sasso National Laboratories (LNGS) located in the Abruzzo region of central Italy.

DARWIN Dark Matter experiment. A design study for a next-generation, multi-ton dark matter detector in Europe at The University of Zurich [Universität Zürich](CH).

PandaX II Dark Matter experiment at Jin-ping Underground Laboratory (CJPL) in Sichuan, China.

Inside the Axion Dark Matter eXperiment U Washington. Credit: Mark Stone U. of Washington. Axion Dark Matter Experiment.

XENONnT experiment at the Laboratori Nazionali del Gran Sasso (LNGS) underground laboratory in Italy.

The University of Western Australia ORGAN Experiment’s main detector. A small copper cylinder called a “resonant cavity” traps photons generated during dark matter conversion. The cylinder is bolted to a “dilution refrigerator” which cools the experiment to very low temperatures.
__________________________________

Is the Big Bang incomplete?

In order to test the Big Bang, astronomers can use measurements taken by the South Pole Telescope and use the theory to project forward to the present day. They can then take measurements from the Dark Energy Survey and compare them. If the measurements are accurate and the theory describes the cosmos, they should agree.

And, by and large, they do — but not completely. When astronomers look at how “clumpy” the matter of the current Universe should be, purely from SPT measurements and extrapolations of theory, they find that the predictions are “clumpier” than current measurements by DES.

This disagreement is potentially significant and could signal that the theory of the Big Bang is incomplete. Furthermore, this isn’t the first discrepancy that astronomers have encountered when they project measurements of the same primordial light imaged by the SPT to the modern day. Different research groups, using different telescopes, have found that the current Universe is expanding faster than expected from observations of the ancient light seen by the SPT, combined with Big Bang theory. This other discrepancy is called the Hubble Tension, named after American astronomer Edwin Hubble, who first realized that the Universe was expanding.

__________________________________________________________________________________

Edwin Hubble

Edwin Hubble looking through the 100-inch Hooker telescope at Mount Wilson in Southern California(US), 1929 discovers the Universe is Expanding. Credit: Margaret Bourke-White/Time & Life Pictures/Getty Images.

Mount Wilson Hooker 100in Telescope interior.

Mt Wilson 100 inch Hooker Telescope, perched atop the San Gabriel Mountains outside Los Angeles, CA, Altitude 1,742 m (5,715 ft).

Edwin Hubble Cepheid variable with Messier 31 at the 100 inch Hooker telescope on Mt Wilson, California.

Edwin Hubble at Caltech Palomar Samuel Oschin 48 inch Telescope Credit: Emilio Segre Visual Archives/AIP/SPL.

.

Caltech Palomar Samuel Oschin 48 inch Telescope, located in San Diego County, California, altitude 1712 m (5617 ft). Credit: Caltech.

__________________________________________________________________________________

Have astronomers disproved the Big Bang?

While the new discrepancy in predictions and measurements of the clumpiness of the Universe are preliminary, it could be that both this measurement and the Hubble Tension imply that the Big Bang theory might need some tweaking. Mind you, the discrepancies do not rise to the level of scrapping the theory entirely; however, it is the nature of the scientific method to adjust theories to account for new observations.

See the full article here.

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

From “EarthSky” : “What is the Milky Way? It’s our home galaxy”

From “EarthSky”

1.27.23
Andy Briggs

Amr Abdulwahab captured this image of the Milky Way on July 8, 2022, from Sahara el Beyda, the White Desert Protected Area, a national park in Egypt.

Do you think of the Milky Way as a starry band across a dark night sky? Or do you think of it as a great spiral galaxy in space? Both are correct. Both refer to our home galaxy, our local island in the vast ocean of the universe, composed of hundreds of billions of stars, one of which is our sun.

Long ago, it was possible for everybody in the world to see a dark, star-strewn sky when they looked heavenward at night. In those ancient times, humans looked to the starry sky and saw a ghostly band of light arcing from horizon to horizon. This graceful arc of light moved across the sky with the seasons. The most casual sky-watchers could notice that darkness obscured parts of the band, which we now know to be vast clouds of dust.

Myths of the Milky Way

Myths and legends grew up in different cultures around this mysterious apparition in the heavens. Each culture explained this band of light in the sky according to its own beliefs. To the ancient Armenians, it was straw strewn across the sky by the god Vahagn. In eastern Asia, it was the Silvery River of Heaven. The Finns and Estonians saw it as the Pathway of the Birds.

Meanwhile, because ancient Greek and Roman legends and myths came to dominate western culture, it was their interpretations that were passed down to a majority of languages. Both the Greeks and the Romans saw the starry band as a river of milk. The Greek myth said it was milk from the breast of the goddess Hera, divine wife of Zeus. The Romans saw the river of light as milk from their goddess Ops.

Thus it was bequeathed the name by which, today, we know that ghostly arc stretching across the sky: the “Milky Way”.

William Mathe captured this image on August 15, 2020, at the top of Rocky Mountain National Park in Colorado.

Observing the river of stars

When you are standing under a completely dark, starry sky, away from light pollution, the Milky Way appears like a cloud across the cosmos. But that cloud betrays no clue as to what it actually is. Until the invention of the telescope, no human could have known the nature of the Milky Way.

Just point even a small telescope anywhere along its length and you will be rewarded with a beautiful sight. What appears as a cloud to the unaided eye resolves into countless stars. Their distance and close relative proximity to each other do not permit us to pick them out individually with just our eyes.

It’s the same way a raincloud looks solid in the sky but actually consists of countless water droplets. The stars of the Milky Way merge together into a single band of light. But through a telescope, we see the Milky Way for what it truly is: a spiral arm of our galaxy.

What is the Milky Way?

Thus we arrive at the second answer to the question of what the Milky Way is. To astronomers, it is the name given to the entire galaxy we live in, not just the part of it we see in the sky. If this seems confusing, we must acknowledge the need for our galaxy to have a name.

Many other galaxies are designated by catalog numbers rather than names, for example the New General Catalogue [NGC+++]. First published in 1888, it merely assigns a sequential number to each. More recent catalog numbers contain information of far more use to astronomers, for example, the galaxy’s location on the sky and during which survey it was discovered. Moreover, a galaxy may appear in more than one catalog and thus possess more than one designation. For example, the galaxy NGC 2470 is also known as 2MFGC 6271.

Other galaxies, particularly those brighter and closer, received names from astronomers of the 17th and 18th centuries. The names reflected their appearance: the Pinwheel, the Sombrero, the Sunflower, the Cartwheel, the cigar and so forth. These names came long before any systematic sky surveys with numerical labeling systems.

In time, the galaxies with descriptive labels received catalog numbers as well. Yet, our own galaxy does not appear in any index of galaxies. So, it needed a name for astronomers to refer to it by. Thus we call it the “Milky Way” instead of the galaxy or our galaxy. That name refers to both that river of light across the sky, which is part of our galaxy, and the galaxy as a whole. When not using the name, astronomers refer to it with a capital G (the Galaxy), and all other galaxies with a lowercase g.

Where is the sun in our galaxy?

Our solar system lies about 2/3 of the way out from the galactic center. We’re 26,000 light-years from the center, or 153,000 trillion miles (246,000 trillion km).

When we look toward the edge of the galaxy, we see the Orion-Cygnus Arm (or the Orion spur). The solar system is just on the inner edge of this spiral arm.

Or we can look toward the center of the galaxy, in the direction of Sagittarius. Vast clouds of dark gas hide the galactic center from us. Only in recent decades have astronomers pierced that dusty fog with infrared telescopes. A study of around 100 stars at the galactic center revealed that those giant clouds of dark dust were hiding a monster: a black hole. This black hole – known as Sagittarius A* – has a mass four million times that of our sun.

This is the first image of Sagittarius A* [SGR A*]- the supermassive black hole at the center of the Milky Way. Credit: The Event Horizon Telescope Collaboration.

In this artist’s concept of the Milky Way, you can see the sun’s location below the central bar, at the inward side of the Orion Arm (called by its slightly dated name, the Orion Spur). The Orion Arm lies between the Sagittarius Arm and the Perseus Arm. Credit: R. Hurt/ NASA-JPL Caltech.

The stats on our galaxy

Our Milky Way galaxy is one of billions in the universe. We do not know exactly how many galaxies exist: a modern estimate vastly increases previous counts to as many as 2 trillion.

The Milky Way is approximately 100,000 light-years across, or 600,000 trillion miles (950,000 trillion km). We do not know its exact age, but we assume it came into being in the very early universe along with most other galaxies: within perhaps a billion years after the Big Bang. Estimates of how many stars live within the Milky Way vary quite considerably, but it seems to be somewhere between 100 billion and double that figure.

Why is there so much variance? Simply because it is so difficult to count the number of stars in the galaxy from our vantage point here on Earth. Imagine being in a banquet room full of people and trying to count everyone without being able to move around the room. From where you are standing, all you can do is make an estimate because people close to you block the view of those farther away. Neither can you see what size and shape the room is. The mass of people hides the edges of the room. It’s exactly the same from our position in the galaxy.

The Milky Way as seen in different wavelengths of light. The most familiar view is optical (or visible) light, which is the 3rd image from the bottom. In optical light, gas clouds darken our view of much of the galaxy. But look in the same direction in infrared light, and you can see through the clouds (4th, 5th and 6th image from the bottom). Read more about these images. Image via NASA.

Seeing the city of stars

It is this inability to see the structure of the Milky Way from our location inside it that meant for most of human history we did not even recognize that we live inside a galaxy in the first place. Indeed, we did not even realize what a galaxy is: a vast city of stars, separated from others by even vaster distances.

[I highly recommend a video, from “NatGeo” Inside the Milky Way available here [ https://www.youtube.com/watch?v=hXFQ0xGfOJU ]

Without telescopes, we couldn’t see most of the other galaxies in the sky. The unaided eye can only see three of them: from the Northern Hemisphere we can see the Andromeda galaxy. Also known as Messier 31, the Andromeda galaxy lies some two million light-years from us.

Andromeda Galaxy (Messier 31). Credit: Adam Evans, University of Virginia.

In fact, it’s the farthest object we can see with our eyes alone, under dark skies. The skies in the Southern Hemisphere also have the Small and Large Magellanic Clouds, two amorphous dwarf galaxies orbiting our own.

Small Magellanic Cloud. 10 November 2005. NASA/ESA Hubble and DSS 2.

The European Southern Observatory [La Observatorio Europeo Austral] [Observatoire européen austral][Europaiche Sûdsternwarte] (EU)(CL)’s VISTA telescope reveals a remarkable image of the Large Magellanic Cloud.

They are far larger and brighter in the sky than Messier 31 simply because they are much closer to us.

The Large and Small Magellanic Clouds over Paranal in Chile. These are satellite galaxies of the Milky Way that you can only see from the Southern Hemisphere. Image via the European Southern Observatory.

Other galaxies in the universe

Until the 1910s, astronomers had not observationally confirmed the existence of other galaxies. Astronomers long believed that those fuzzy patches of light they saw through their telescopes were nebulae, vast clouds of gas and dust in our own galaxy.

But the concept of other galaxies was born earlier, in the early and mid-18th century. Swedish philosopher and scientist Emanuel Swedenborg and English astronomer Thomas Wright apparently conceived the idea independently of each other. Building upon the work of Wright, German philosopher Immanuel Kant referred to galaxies as island universes. The first observational evidence came in 1912 by American astronomer Vesto Slipher, who found that the spectra of the “nebulae” he measured were redshifted and thus much further away than astronomers previously thought.

Edwin Hubble and distant galaxies

And then came Edwin Hubble. Through years of painstaking work at the Mount Wilson Observatory in California, he confirmed in the 1920s that we do not live in a unique location. Our galaxy is just one of perhaps trillions.

Edwin Hubble looking through the 100-inch Hooker telescope at Mount Wilson in Southern California(US), 1929 discovers the Universe is Expanding. Credit: Margaret Bourke-White/Time & Life Pictures/Getty Images.

Edwin Hubble at Caltech Palomar Samuel Oschin 48 inch Telescope Credit: Emilio Segre Visual Archives/AIP/SPL.

Caltech Palomar Samuel Oschin 48 inch Telescope, located in San Diego County, California, altitude 1712 m (5617 ft). Credit: Caltech.

Hubble came to this realization by studying a type of star known as a Cepheid variable, which pulsates with a regular periodicity. The intrinsic brightness of a Cepheid variable is directly related to its pulsation period: by measuring how long it takes for the star to brighten, fade and brighten again you can calculate how bright it is, that is to say, how much light it emits. Consequently, by observing how bright it appears from the Earth, you can calculate its distance.

Edwin Hubble Cepheid variable with Messier 31 at the 100 inch Hooker telescope on Mt Wilson, California.

Mount Wilson Hooker 100 in Telescope interior.

Mt Wilson 100 inch Hooker Telescope, perched atop the San Gabriel Mountains outside Los Angeles, CA, Altitude 1,742 m (5,715 ft).

It’s like seeing distant car headlights at night and estimating how far away the car is from how bright its lights appear. You can judge the distance of the car because you know all car headlights have about the same brightness.

Cepheid variables in Andromeda

One of Edwin Hubble’s great achievements was the discovery of Cepheid variables in Messier 31, the Andromeda galaxy. Hubble repeatedly photographed Andromeda with the Hooker Telescope. Eventually, he found stars that changed in brightness over a regular period. Performing the calculations, Hubble realized that Messier 31 is not astronomically close to us at all. It’s 2 million light-years away, and it’s a galaxy like our own.

Hubble, for whom this discovery must have been a monumental shock, surmised that our galaxy was no different from Messier 31 and the others he observed. Thus, he relegated us to a position of lesser importance in the universe. This was as big a revelation and diminution of our position in the universe. It was like when we learned that Earth is not the center of the universe.

We do not live in a special or privileged location. The universe does not have any vantage points which are superior to others. Wherever you are in the universe and you look up at the stars, you will see the same thing. Your constellations may be different, but no matter in which direction you look, you see galaxies rushing away from you in all directions as the universe expands, carrying the galaxies along with it.

Until the work by Slipher and Hubble (and others), we did not know the universe was expanding. It took a surprisingly long time for the astronomical community to accept this fact. Even Albert Einstein did not believe it, introducing an arbitrary correction into his calculations on relativity to achieve a static, non-expanding universe. However, Einstein later called this correction his greatest error.

______________________________________________________________________________

Nobel Prize in Physics for 2011 Expansion of the Universe

Saul Perlmutter (center) [The Supernova Cosmology Project] shared the 2006 Shaw Prize in Astronomy, the 2011 Nobel Prize in Physics, and the 2015 Breakthrough Prize in Fundamental Physics with Brian P. Schmidt (right) and Adam Riess (left) [The High-z Supernova Search Team] for providing evidence that the expansion of the universe is accelerating.

4 October 2011

The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Physics for 2011

with one half to

Saul Perlmutter
The Supernova Cosmology Project
The DOE’s Lawrence Berkeley National Laboratory and The University of California-Berkeley,

and the other half jointly to

Brian P. SchmidtThe High-z Supernova Search Team, The Australian National University, Weston Creek, Australia.

and

Adam G. Riess

The High-z Supernova Search Team,The Johns Hopkins University and The Space Telescope Science Institute, Baltimore, MD.

Written in the stars

“Some say the world will end in fire, some say in ice…” *

What will be the final destiny of the Universe? Probably it will end in ice, if we are to believe this year’s Nobel Laureates in Physics. They have studied several dozen exploding stars, called supernovae, and discovered that the Universe is expanding at an ever-accelerating rate. The discovery came as a complete surprise even to the Laureates themselves.

In 1998, cosmology was shaken at its foundations as two research teams presented their findings. Headed by Saul Perlmutter, one of the teams had set to work in 1988. Brian Schmidt headed another team, launched at the end of 1994, where Adam Riess was to play a crucial role.

The research teams raced to map the Universe by locating the most distant supernovae. More sophisticated telescopes on the ground and in space, as well as more powerful computers and new digital imaging sensors (CCD, Nobel Prize in Physics in 2009), opened the possibility in the 1990s to add more pieces to the cosmological puzzle.

The teams used a particular kind of supernova, called Type 1a supernova. It is an explosion of an old compact star that is as heavy as the Sun but as small as the Earth. A single such supernova can emit as much light as a whole galaxy. All in all, the two research teams found over 50 distant supernovae whose light was weaker than expected – this was a sign that the expansion of the Universe was accelerating. The potential pitfalls had been numerous, and the scientists found reassurance in the fact that both groups had reached the same astonishing conclusion.

For almost a century, the Universe has been known to be expanding as a consequence of the Big Bang about 14 billion years ago. However, the discovery that this expansion is accelerating is astounding. If the expansion will continue to speed up the Universe will end in ice.

The acceleration is thought to be driven by dark energy, but what that dark energy is remains an enigma – perhaps the greatest in physics today. What is known is that dark energy constitutes about three quarters of the Universe. Therefore the findings of the 2011 Nobel Laureates in Physics have helped to unveil a Universe that to a large extent is unknown to science. And everything is possible again.

*Robert Frost, Fire and Ice, 1920
______________________________________________________________________________

The Milky Way from a distance

So, what does the Milky Way would look like from the outside? How many spiral arms there are? How big is the galaxy and how many stars does it hold? These were questions still unanswered in the 1920s. It took most of the 20th century after Hubble’s discoveries to piece together those answers through a combination of painstaking work with both Earth- and space-based telescopes.

So, if you could travel outside our galaxy, what would it look like? A standard analogy compares it to two fried eggs stuck together back-to-back. The yolk of the egg is known as the Galactic Bulge, a huge globe of stars at the center extending above and below the plane of the galaxy.

Astronomers now think the Milky Way has four spiral arms winding out from its center like the arms of a Catherine wheel. But these arms do not actually meet at the center. A few years ago astronomers discovered that the Milky Way is a barred spiral galaxy. This means a “bar” of stars runs across its center, and the spiral arms extend from either end. Barred spiral galaxies are not uncommon in the universe. But we do not yet understand how that central bar forms.

New discoveries in the Milky Way

Only a few years ago, astronomers made another major discovery. The Milky Way is not a flat disk of stars but has a kink running across it like an extended S. Something has warped the disk. At the moment, the finger points at the gravitational influence of the astronomically close Sagittarius dwarf galaxy.

Sagittarius dwarf galaxy. Credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA)

It’s one of perhaps twenty small galaxies that orbit the Milky Way, like moths around a flame. As the Sagittarius galaxy slowly orbits around us, its gravity has pulled on our galaxy’s stars, eventually creating the warp.

Other objects are also bound to the Milky Way. A halo of globular clusters surrounds our galaxy. Globular clusters are concentrations of stars that look like fuzzy golf balls. They contain perhaps a million or so extremely ancient stars.

Discoveries about the Milky Way continue. The study of its nature and origin is accelerating as new astronomical tools become available, such as the European Space Agency’s orbiting Gaia telescope.

European Space Agency [La Agencia Espacial Europea][Agence spatiale européenne][Europäische Weltraumorganization](EU) GAIA satellite.

Gaia is making a three-dimensional map of our galaxy’s stars with exquisite and quite unprecedented accuracy. Read more about Gaia’s 3rd data release.

Gaia Early Data Release 3. This is not an image of the Milky Way. Each dot of light is a source that has been documented and analyzed as part of the Gaia mission. Put each source in its proper position in the sky, and give it the color that was measured by Gaia through red and blue filters, and the catalogue of 1.7 billion sources coalesces into a faithful rendition of the Milky Way, of our two closest galactic neighbors, the Magellanic clouds, and of many more distant cosmic objects, as seen from Earth. © ESA/Gaia/DPAC unter Lizenz CC BY-SA 3.0 IGO.

It’s an extremely exciting time for the study of our galaxy. It is all a far cry from when, thousands of years ago, our ancestors ascribed fantastic beasts and gods to that mysterious band of light they saw as they stood in awe under the starry sky.

See the full article here .

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

five-ways-keep-your-child-safe-school-shootings
Please help promote STEM in your local schools.

Stem Education Coalition

Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. “Being an EarthSky editor is like hosting a big global party for cool nature-lovers,” she says.

From University of Chicago (US): “The Hubble constant explained”

From University of Chicago (US)

Jun 29, 2021
Sasha Warren

Prof. Daniel Holz discusses a new way to calculate the Hubble constant, a crucial number that measures the expansion rate of the universe and holds answers to questions about the universe’s size, age and history.
Video by UChicago Creative.

The Hubble constant is one of the most important numbers in cosmology because it tells us how fast the universe is expanding, which can be used to determine the age of the universe and its history. It gets its name from UChicago alum Edwin Hubble, who was first to calculate the constant from his measurements of stars in 1929.

Edwin Hubble at Caltech Palomar Samuel Oschin 48 inch Telescope(US) Credit: Emilio Segre Visual Archives/AIP/SPL.

Edwin Hubble looking through the 100-inch Hooker telescope at Mount Wilson in Southern California(US), 1929 discovers the Universe is Expanding.Credit: Margaret Bourke-White/Time & Life Pictures/Getty Images.

Despite nearly a hundred years of astronomical measurements and calculations scientists still can’t agree on the exact value of the Hubble constant. The true number could reveal missing pieces in our understanding of physics like new particles or a new form of Dark Energy.

What is the Hubble constant?

Figuring out the true value of the Hubble constant is one of the greatest challenges in modern astronomy and could revolutionize our understanding of the universe—so scientists at the University of Chicago and many other institutions around the world are trying to pin down the number using multiple methods.

For an astronomical object (e.g. a star or a galaxy) at a known distance from the Earth, the Hubble constant can be used to predict how fast it should be moving away from us.

However, the true value of the Hubble constant remains up for debate. Based on the fundamental physics that scientists believe has driven the evolution of the universe, the Hubble constant should be around 68 km/s/Mpc—but this doesn’t match up to observations of the actual stars and galaxies astronomers see around us. UChicago astronomer Wendy Freedman led a team that made a landmark measurement in 2001 which found a value of 72. The most recent precise measurements of the distances and movements of distant exploding stars suggest a Hubble constant of 69.8 km/s/Mpc but other reports have pushed the value as high as 74 km/s/Mpc.

Although these differences seem small, even a 2 km/s/Mpc discrepancy between predictions from physics and observations implies there could be something major missing from our current understanding of the universe.

How was the Hubble constant discovered?

In the early 1920s mathematicians used Einstein’s equations for general relativity to predict that the universe should be expanding but scientists had not yet proven this through observations. At the time, astronomers didn’t even have the observations to settle the Great Debate about the size of the universe; some even argued that the universe did not extend beyond the Milky Way.

Edwin Hubble entered the world of astronomy at this exciting time. He graduated from the University of Chicago in 1910 with a bachelor’s degree in mathematics, physics and philosophy, and later returned to the Yerkes Observatory of the University of Chicago as a graduate student. While working at California’s Mount Wilson Observatory, Hubble used his extensive telescope experience to make measurements of Cepheid variable stars.

Hubble used the work of fellow astronomer Henrietta Leavitt to predict the brightness of these stars, which enabled him to calculate their distances from Earth. Not only did these measurements confirm that the universe extends far beyond the Milky Way, Hubble noticed that more distant stars seemed to be moving away faster.

In 1929, Hubble and colleague Milton Humason used their observations to calculate the mathematical relationship between the distance to a star and the speed at which it is traveling away from the Earth—and thus, the Hubble constant was born. Hubble’s original estimate was 500 km/s/Mpc, or about seven times the value astronomers think it is today.

Generations of astronomers have improved upon Hubble’s original methods and developed new ones, bringing down the Hubble constant to around 70 km/s/Mpc, but there’s still a long way to go. Even though astronomers can now make incredibly precise measurements of many more galaxies and stars, different methods for measuring the Hubble constant still produce disparate results.

How does it work?

Imagine a blueberry muffin. As the muffin bakes and rises, the batter expands, moving all the blueberries apart. If two blueberries enter the oven half an inch away from each other and the batter doubles in size, the distance between them will increase to a full inch. If two blueberries are an inch away from each other before the batter expands, they will be two inches apart once the muffin is baked.

Likewise, distant galaxies moving away faster than nearby galaxies is exactly what we would expect to see in a universe that is expanding everywhere. The Hubble constant tells us the rate at which this is happening.

Image courtesy of UChicago Creative.

The expansion of the universe is driven by all the mass, radiation and energy contained within it. The Friedmann equation, derived from Einstein’s famous equations for general relativity, can be used to predict how quickly the universe is expanding mathematically. These equations state that a denser universe expands more quickly, so expansion was fastest when all of the particles in the universe were packed closely together after the Big Bang. Over the past 14 billion years, these particles—and their accompanying energy and radiation—have spread out to vast distances.

We can use the Hubble constant to make a first guess at the age of the universe simply using the equation: speed = distance divided by time. The Hubble constant tells us the speed of an object at any distance, and since the distance between all objects in the universe before any expansion must have been zero, the time in this equation must be the age of the universe. Depending on the value of the Hubble constant, this gives an age of about 14 billion years—not far off the current best-estimate of 13.8 billion years.

However, there’s a slight complication. The speeds of the farthest stars and galaxies that we can observe don’t match what the Hubble constant predicts. Because light from a distant object has traveled for billions of years to reach us, our observations are not only affected by the present-day value of the Hubble constant, but also what it was when the universe was expanding more slowly. In other words, the Hubble constant isn’t a constant at all!

How is the Hubble constant measured?

Currently, there are three main ways to measure the Hubble constant: by using astronomical measurements to look at objects nearby and see how fast they are moving; by using gravitational waves from collisions of black holes or neutron stars; or by measuring the light left over from the Big Bang, known as the cosmic microwave background.

Astronomical Measurements

To measure the Hubble constant by observing the universe, astronomers need to be able to measure two things:

The distance to astronomical objects
The “recession velocity” of each object (i.e., how fast it is moving away from the observer)

The recession velocity can be measured by taking advantage of a phenomenon called the Doppler effect. A classic example of the Doppler effect is how the sound of a siren changes as an ambulance passes by. This is because the sound waves moving between you and the ambulance are compressed as the ambulance approaches (essentially catching up on its own sound waves), and stretched as it races away.

The same thing can happen to light: The light from stars and galaxies moving away from the Earth is stretched out in the same way as the siren sound from the ambulance, increasing the wavelength of the light. Astronomers call this “redshift.”

The South Pole Telescope and Dark Energy Camera provided key data for scientists to create a new method to weigh galaxy clusters. Photo by Robert Schwarz.

South Pole Telescope SPTPOL. The SPT collaboration is made up of over a dozen (mostly North American) institutions, including The University of Chicago (US); The University of California Berkeley (US); Case Western Reserve University (US); Harvard/Smithsonian Astrophysical Observatory (US); The University of Colorado-Boulder (US); McGill University(CA); The University of Illinois, Urbana-Champaign (US); The University of California-Davis (US); Ludwig Maximilians Universität München(DE); DOE’s Argonne National Laboratory (US); and The National Institute for Standards and Technology (US). It is funded by the National Science Foundation(US)

Dark Energy Camera [DECam] built at DOE’s Fermi National Accelerator Laboratory(US)

To measure the redshift, and therefore the object’s velocity, astronomers look for patterns in the light emitted by stars known as absorption lines. These always occur at the same wavelengths because they are created by the elements in stars’ atmospheres. When redshift changes the wavelength of all the light and absorption lines coming from a distant star, astronomers can measure how much it has shifted to calculate how fast the star is travelling away from us.

Distance to an object is often much more challenging to calculate. For anything beyond our own galaxy, scientists need to know the inherent brightness of the object and compare that to its brightness as viewed from Earth.

“The principle is simple,” said Wendy Freedman, the John and Marion Sullivan University Professor in Astronomy & Astrophysics at UChicago. “Imagine that you are standing near a street light that you know is 10 feet away. At regular intervals down the street you can see more street lights, which get progressively dimmer the further away that they are.

“Knowing how far away and how bright the lamp is beside you, and then measuring how much fainter the more distant lamps appear to be, allows you to estimate the distances to each of the other lamps all down the road.”

This means astronomers can calculate the distance to any objects whose brightness can be predicted; light sources that have been reliably measured are known as “standard candles.”

Standard Candles to measure age and distance of the universe

As part of the Hubble Space Telescope Key Project team, Freedman used detailed observations of Cepheid stars to find a value of 72-73 km/s/Mpc, where the best star-based estimates of the constant have stayed for the past two decades.

However, to make an independent estimate of the Hubble constant, Freedman has also pioneered the use of an entirely different kind of star: red giants. Red giants are stars at the end of their lives. Part of their death sequence includes a sudden jump to 100 million degree temperatures in the core of the star, accompanied by a dramatic drop in brightness. From studying nearby red giant stars at known distances, astronomers can measure the maximum brightness of these dying stars. Freedman used this maximum red giant brightness to calculate distances to far galaxies.

Using this new red giant method, Freedman’s new measurement of the Hubble constant was 69.8 km/s/Mpc— between the previously observed value and the value predicted by mathematical models of the universe’s evolution.

Gravitational waves

Gravitational waves. Credit:MPG Institute for Gravitational Physics [Max-Planck-Institut für Gravitationsphysik] (Albert Einstein Institute) (DE)/W.Benger-Zib.

Artist’s by now iconic conception of two merging black holes similar to those detected by LIGO. Credit: Aurore Simonnet /Caltech MIT Advanced aLIGO(US)/Sonoma State University (US).

Gravitational waves are ripples in the fabric of space-time, and they are produced during highly energetic events like neutron star collisions.

Merging neutron stars. Image Credit: Mark Garlick, University of Warwick (UK).

Scientists can now pick up these waves on Earth using the Laser Interferometer Gravitational-Wave Observatory (LIGO).

LIGO–VIRGO–KAGRA

MIT /Caltech Advanced aLigo .

Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA.

Caltech/MIT Advanced aLigo Hanford, WA, USA installation.

VIRGO Gravitational Wave interferometer, near Pisa, Italy

KAGRA Large-scale Cryogenic Gravitational Wave Telescope Project (JP)

UChicago Prof. Daniel Holz was the first to suggest that gravitational waves could offer a new way to calculate cosmic distances, coining the term “standard sirens” in a play on “standard candles.”

Astronomers can use the shape of arriving gravitational wave signals to calculate how much energy was released when the two neutron stars collided, and compare this to how much energy the signals are carrying by the time they reach Earth to calculate distance. Holz’s method gives a preliminary value of 70 km/s/Mpc for the Hubble constant, in agreement with Freedman’s most recent work.

Cosmic Microwave Background Radiation modelling

Cosmic microwave background radiation. Stephen Hawking Center for Theoretical Cosmology U, Cambridge (UK).

After the Big Bang, the superheating of all the matter in the universe released enormous amounts of radiation as photons. As the universe expanded, this radiation got more and more redshifted. The record of this radiation and redshifting is in the cosmic microwave background, or CMB.

CMB per European Space Agency(EU) Planck.

However, the cosmic microwave background is not uniform; it’s made up of hotter and colder patches that record the “clumpiness” of matter and energy in the very early universe. By combining fundamental physics with estimates of the amount of mass and energy contained within the universe, cosmologists can model the expansion of the universe from its initial state to the present day and reproduce the observed clumpiness in the cosmic microwave background. Cosmologists have repeated this procedure hundreds of thousands of times to find the combinations of conditions that match observations. That includes a measurement of the Hubble constant.

Initial model results seemed to line up with astronomical measurements at around 73 km/s/Mpc, but as observations of the cosmic microwave background got more and more detailed, their estimate has been inching downwards. The European Space Agency’s Planck mission produced the most detailed map of the cosmic microwave background to date, which has been used to calculate a most-likely Hubble constant of only 67.8 km/s/Mpc.

European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU) Planck 2009 to 2013

What are possible explanations for the discrepancy?

One possibility is that one or more of the methods to calculate the Hubble constant is flawed. However, the measurements of stars, galaxies, and the cosmic microwave background are incredibly detailed—which means the differences are most likely the result of something much more fundamental than imprecision.

The Bullet Galaxy (RXC J2359.3-6042 CC).Courtesy of National Aeronautics Space Agency (US).

One solution to this conundrum could be Dark Energy—a mysterious, constant and as yet unobservable background energy that doesn’t spread out even when the universe is expanding.

_____________________________________________________________________________________
Dark Energy Survey

Dark Energy Camera [DECam] built at DOE’s Fermi National Accelerator Laboratory(US),

NOIRLab National Optical Astronomy Observatory(US) Cerro Tololo Inter-American Observatory(CL) Victor M Blanco 4m Telescope which houses the Dark-Energy-Camera – DECam at Cerro Tololo, Chile at an altitude of 7200 feet

Timeline of the Inflationary Universe WMAP

The Dark Energy Survey (DES) is an international, collaborative effort to map hundreds of millions of galaxies, detect thousands of supernovae, and find patterns of cosmic structure that will reveal the nature of the mysterious dark energy that is accelerating the expansion of our Universe. DES began searching the Southern skies on August 31, 2013.

According to Einstein’s theory of General Relativity, gravity should lead to a slowing of the cosmic expansion. Yet, in 1998, two teams of astronomers studying distant supernovae made the remarkable discovery that the expansion of the universe is speeding up. To explain cosmic acceleration, cosmologists are faced with two possibilities: either 70% of the universe exists in an exotic form, now called dark energy, that exhibits a gravitational force opposite to the attractive gravity of ordinary matter, or General Relativity must be replaced by a new theory of gravity on cosmic scales.

DES is designed to probe the origin of the accelerating universe and help uncover the nature of dark energy by measuring the 14-billion-year history of cosmic expansion with high precision. More than 400 scientists from over 25 institutions in the United States, Spain, the United Kingdom, Brazil, Germany, Switzerland, and Australia are working on the project. The collaboration built and is using an extremely sensitive 570-Megapixel digital camera, DECam, mounted on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory, high in the Chilean Andes, to carry out the project.

Over six years (2013-2019), the DES collaboration used 758 nights of observation to carry out a deep, wide-area survey to record information from 300 million galaxies that are billions of light-years from Earth. The survey imaged 5000 square degrees of the southern sky in five optical filters to obtain detailed information about each galaxy. A fraction of the survey time is used to observe smaller patches of sky roughly once a week to discover and study thousands of supernovae and other astrophysical transients.
_____________________________________________________________________________________

The true value of the Hubble constant could indicate that more dark energy needs to be added to the models of the very young universe to drive its early expansion. This could give scientists new information about the fundamental nature of dark energy and how it has behaved throughout the universe’s history.

Yet another mysterious character that could account for the discrepancy is “dark radiation.” This theory proposes the existence of a new class of subatomic particles (like electrons, neutrinos, and photons), which travel close to the speed of light and zip around the universe, driving its expansion.

To make matters even more complicated, there may not be any extra energy or radiation at all. Dark matter might just interact with the universe in a way that hasn’t yet been built into scientists’ understanding of physics.

What are scientists doing to resolve it?

Scientists are trying to collect more solid evidence to improve each method of calculating the Hubble constant.

Some, including UChicago scientists John Carlstrom, Brad Benson and Jeff McMahon, are working on the next generation of CMB telescopes in Antarctica and Chile’s Atacama Desert to check the Planck data and hopefully help calculate an even more precise value for the Hubble constant.

Meanwhile in the astronomers’ corner, Freedman and others are working to take new measurements with different kinds of stars and a technique called gravitational lensing that takes advantage of the enormous mass of galaxies to focus light from celestial objects too far away to see with previous observation methods. And Holz and his colleagues are hoping for more distance measurements from gravitational waves born in neutron star collisions.

Either way, converging on the true value of the Hubble constant is vital for our understanding of the age of the universe and its history.

See the full article here .

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

The University of Chicago (US) is an urban research university that has driven new ways of thinking since 1890. Our commitment to free and open inquiry draws inspired scholars to our global campuses, where ideas are born that challenge and change the world.

We empower individuals to challenge conventional thinking in pursuit of original ideas. Students in the College develop critical, analytic, and writing skills in our rigorous, interdisciplinary core curriculum. Through graduate programs, students test their ideas with UChicago scholars, and become the next generation of leaders in academia, industry, nonprofits, and government.

UChicago research has led to such breakthroughs as discovering the link between cancer and genetics, establishing revolutionary theories of economics, and developing tools to produce reliably excellent urban schooling. We generate new insights for the benefit of present and future generations with our national and affiliated laboratories: DOE’s Argonne National Laboratory (US), DOE’s Fermi National Accelerator Laboratory (US), and the Marine Biological Laboratory in Woods Hole, Massachusetts.
The University of Chicago is enriched by the city we call home. In partnership with our neighbors, we invest in Chicago’s mid-South Side across such areas as health, education, economic growth, and the arts. Together with our medical center, we are the largest private employer on the South Side.

In all we do, we are driven to dig deeper, push further, and ask bigger questions—and to leverage our knowledge to enrich all human life. Our diverse and creative students and alumni drive innovation, lead international conversations, and make masterpieces. Alumni and faculty, lecturers and postdocs go on to become Nobel laureates, CEOs, university presidents, attorneys general, literary giants, and astronauts. The University of Chicago is a private research university in Chicago, Illinois. Founded in 1890, its main campus is located in Chicago’s Hyde Park neighborhood. It enrolled 16,445 students in Fall 2019, including 6,286 undergraduates and 10,159 graduate students. The University of Chicago is ranked among the top universities in the world by major education publications, and it is among the most selective in the United States.

The university is composed of one undergraduate college and five graduate research divisions, which contain all of the university’s graduate programs and interdisciplinary committees. Chicago has eight professional schools: the Law School, the Booth School of Business, the Pritzker School of Medicine, the School of Social Service Administration, the Harris School of Public Policy, the Divinity School, the Graham School of Continuing Liberal and Professional Studies, and the Pritzker School of Molecular Engineering. The university has additional campuses and centers in London, Paris, Beijing, Delhi, and Hong Kong, as well as in downtown Chicago.

University of Chicago scholars have played a major role in the development of many academic disciplines, including economics, law, literary criticism, mathematics, religion, sociology, and the behavioralism school of political science, establishing the Chicago schools in various fields. Chicago’s Metallurgical Laboratory produced the world’s first man-made, self-sustaining nuclear reaction in Chicago Pile-1 beneath the viewing stands of the university’s Stagg Field. Advances in chemistry led to the “radiocarbon revolution” in the carbon-14 dating of ancient life and objects. The university research efforts include administration of DOE’s Fermi National Accelerator Laboratory(US) and DOE’s Argonne National Laboratory(US), as well as the U Chicago Marine Biological Laboratory in Woods Hole, Massachusetts (MBL)(US). The university is also home to the University of Chicago Press, the largest university press in the United States. The Barack Obama Presidential Center is expected to be housed at the university and will include both the Obama presidential library and offices of the Obama Foundation.

The University of Chicago’s students, faculty, and staff have included 100 Nobel laureates as of 2020, giving it the fourth-most affiliated Nobel laureates of any university in the world. The university’s faculty members and alumni also include 10 Fields Medalists, 4 Turing Award winners, 52 MacArthur Fellows, 26 Marshall Scholars, 27 Pulitzer Prize winners, 20 National Humanities Medalists, 29 living billionaire graduates, and have won eight Olympic medals.

UChicago research has led to such breakthroughs as discovering the link between cancer and genetics; establishing revolutionary theories of economics; and developing tools to produce reliably excellent urban schooling. We generate new insights for the benefit of present and future generations.

The University of Chicago is enriched by the city we call home. In partnership with our neighbors, we invest in Chicago’s mid-South Side across such areas as health, education, economic growth, and the arts. Together with our medical center, we are the largest private employer on the South Side.

In all we do, we are driven to dig deeper, push further, and ask bigger questions—and to leverage our knowledge to enrich all human life. Our diverse and creative students and alumni drive innovation, lead international conversations, and make masterpieces. Alumni and faculty, lecturers and postdocs go on to become Nobel laureates, CEOs, university presidents, attorneys general, literary giants, and astronauts.

Research

According to the National Science Foundation (US), University of Chicago spent $423.9 million on research and development in 2018, ranking it 60th in the nation. It is classified among “R1: Doctoral Universities – Very high research activity” and is a founding member of the Association of American Universities (US) and was a member of the Committee on Institutional Cooperation from 1946 through June 29, 2016, when the group’s name was changed to the Big Ten Academic Alliance. The University of Chicago is not a member of the rebranded consortium, but will continue to be a collaborator.

The university operates more than 140 research centers and institutes on campus. Among these are the Oriental Institute—a museum and research center for Near Eastern studies owned and operated by the university—and a number of National Resource Centers, including the Center for Middle Eastern Studies. Chicago also operates or is affiliated with several research institutions apart from the university proper. The university manages Argonne National Laboratory, part of the United States Department of Energy’s national laboratory system, and co-manages Fermi National Accelerator Laboratory (Fermilab), a nearby particle physics laboratory, as well as a stake in the Apache Point Observatory (US) in Sunspot, New Mexico. Faculty and students at the adjacent Toyota Technological Institute at Chicago collaborate with the university. In 2013, the university formed an affiliation with the formerly independent Marine Biological Laboratory in Woods Hole, Mass. Although formally unrelated, the National Opinion Research Center (US) is located on Chicago’s campus.

From Astronomy Magazine: “The Steady State: When astronomers tried to overthrow the Big Bang”

From Astronomy Magazine

January 6, 2020
Mara Johnson-Groh

Some astronomers didn’t like the religious implications of a universe with a beginning. Their alternative was the so-called “steady state model.”

NASA/ESA/S. Beckwith(STScI) and The HUDF Team

It all started with a Big Bang. Or maybe it didn’t. In the mid-20th century, most physicists were split on how the universe began — or if it even had a beginning at all. Today, scientists agree that the Big Bang theory best describes the birth of our universe nearly 14 billion years ago. The idea now has a lot of observational evidence, but in the 1940s and ’50s it was still widely debated.

The Big Bang theory roused the public and religious realms perhaps even more than the scientific community, which had previously accepted an idea called the steady state model. “It was not only a scientific controversy, it also included some broader aspects, ideological and religious aspects. And that was one reason why it was so publicly controversial,” says Helge Kragh, a science historian and professor emeritus at the Niels Bohr Institute. “The steady state theory was, especially in England, often associated with atheism, and the Big Bang theory with Christian theism.” If the universe had a creation point, then it probably had a creator, the thinking went.

Beginnings of Cosmology

Humans have always held ideas about how the universe originated. But it wasn’t until advances in the 20th century, including Albert Einstein’s theories of relativity, that astronomers could really form educated ideas about how the universe formed.

Alexander Friedmann, a Russian physicist, was the first to realize that applying the rules of relativity across large scales described a universe that changed over time. With a mathematical approach, he showed the universe could have started small before expanding over enormous distances and, in some cases, eventually collapsing back in on itself.

Observations carried outby Lowell Observatory’s V.M. Slipher and, later, Edwin Hubble, showed that the universe was in fact expanding.

Edwin Hubble looking through a 100-inch Hooker telescope at Mount Wilson in Southern California, 1929 discovers the Universe is Expanding

Edwin Hubble at Caltech Palomar Samuel Oschin 48 inch Telescope, (credit: Emilio Segre Visual Archives/AIP/SPL)

And this helped confirm these initial ideas of the Big Bang. Two years later, the Belgian physicist Georges Lemaître published a paper describing how the expanding universe had started as a tiny, hot, dense speck, which he called the “primeval atom.” Ordained as a Catholic priest, Lemaître reported the finding as a happy coincidence of cosmology and theology in an early draft of the paper, though the comment was removed for the final publication of the paper.

Two decades later, George Gamow would develop theories on the fallout of a hot-birthed universe — namely, how it would create neutrons and protons — and published a popular book on the subject. It even caught the eye of Pope Pius XII, who was taken by the parallels between the scripture of Genesis and the scientific theory.

Unlike the church, Einstein wasn’t initially happy with the idea of a changing universe, preferring one invariable on large scales. British astronomer Fred Hoyle wasn’t happy, either. Along with two other scientists, he developed a counter-theory — the steady state model. The steady state model suggested that the universe had no beginning and had always been expanding. To explain why the universe looks identical in all directions, it proposed tiny traces of matter, too small to be experimentally measured, were continually being created.

This model initially garnered support of around half of the scientific community — albeit one that was very small at the time — and became the Big Bang theory’s biggest rival.

“This [debate between theories] was not in the mainstream of physics research,” says David Kaiser, science historian and physics professor at MIT. “Basically no one paid attention or very little attention, even among professional physicists and astronomers.”

But as evidence started gathering, that would change.

New Evidence

Observations of distant ultra-bright galaxies in the 1950s suggested the universe was changing, and measurements of the helium content in the universe didn’t match the steady state model’s predictions. In 1964, the monumental discovery of the cosmic microwave background radiation [CMB] — direct evidence of a young, hot universe — would deal the final deathblow to the steady state model.

CMB per ESA/Planck

ESA/Planck 2009 to 2013

Cosmic Background Radiation per Planck

“It really seems to suggest … the universe had very different conditions in early times than today,” Kaiser says. “And that was just not what the steady state model suggests.”

In an ironic twist, Hoyle used the term “Big Bang” in an attempt to dismiss the theory in a BBC interview. Though his own theory would be largely lost to history, the irreverent name would stick.

To his death, Hoyle would never submit to the Big Bang theory. A small subset of cosmologists still work on resurrecting a steady state model; but, on the whole, the community overwhelmingly supports the Big Bang theory.

“There are a couple of other puzzles, so cosmologists don’t think we’re done, but they’re now kind of patching or filling in some holes to the original Big Bang models — certainly not replacing it,” Kaiser says.

Saul Perlmutter [The Supernova Cosmology Project] shared the 2006 Shaw Prize in Astronomy, the 2011 Nobel Prize in Physics, and the 2015 Breakthrough Prize in Fundamental Physics with Brian P. Schmidt and Adam Riess [The High-z Supernova Search Team] for providing evidence that the expansion of the universe is accelerating.

See the full article here .

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

Astronomy is a magazine about the science and hobby of astronomy. Based near Milwaukee in Waukesha, Wisconsin, it is produced by Kalmbach Publishing. Astronomy’s readers include those interested in astronomy and those who want to know about sky events, observing techniques, astrophotography, and amateur astronomy in general.

Astronomy was founded in 1973 by Stephen A. Walther, a graduate of the University of Wisconsin–Stevens Point and amateur astronomer. The first issue, August 1973, consisted of 48 pages with five feature articles and information about what to see in the sky that month. Issues contained astrophotos and illustrations created by astronomical artists. Walther had worked part time as a planetarium lecturer at the University of Wisconsin–Milwaukee and developed an interest in photographing constellations at an early age. Although even in childhood he was interested to obsession in Astronomy, he did so poorly in mathematics that his mother despaired that he would ever be able to earn a living. However he graduated in Journalism from the University of Wisconsin Stevens Point, and as a senior class project he created a business plan for a magazine for amateur astronomers. With the help of his brother David, he was able to bring the magazine to fruition.[citation needed]. He died in 1977.

From Astronomy Magazine: Women in STEM- “Meet Henrietta Leavitt, the woman who gave us a universal ruler”

From Astronomy Magazine

February 4, 2019
Korey Haynes

Henrietta Swan Leavitt (1868 – 1921) No image credit

Cepheid variable stars act as signposts to help astronomers build a 3D picture of the sky. Here’s the story of the woman who unlocked these stars’ secrets.

Henrietta Swan Leavitt’s work revealed the true size of the universe. A. Fujii NASA/ESA Hubble

Gazing up at the sky, it’s hard not to imagine the Sun, Moon, stars, and planets as part of an inverted bowl over our heads, even if we know that’s an antiquated way of viewing the heavens. These days, we understand it’s Earth that’s spinning daily like a ballerina, while also circling the Sun on its yearly journey. But the bowl imagery was and remains a reasonable way of envisioning how the skies appear to revolve around us, and why certain stars appear or disappear with the changing hour or season.

But to understand the universe as it really is, we need a three-dimensional picture of the skies. The Copernican revolution started this change in perspective, but it took until the 20th century for a true understanding of the universe’s scale and layout to evolve. The researcher who provided one of the biggest keys was a deaf woman who earned 30 cents an hour.

Changing Stars Unlock a Map

Leavitt’s work on variable stars allowed Edwin Hubble to deduce the distance to the Andromeda galaxy.

Using the Hooker Telescope at Mt. Wilson, Hubble identified Cepheid variables (a kind of star that is used as a means to determine the distance from the galaxy in several spiral nebulae, including the Andromeda Nebula and Triangulum).

Andromeda Nebula Clean by Rah2005 on DeviantArt

The Triangulum Galaxy via The VLT Survey Telescope (VST) at ESO’s Paranal Observatory in Chile. This beautifully detailed image of the galaxy Messier 33. This nearby spiral, the second closest large galaxy to our own galaxy, the Milky Way, is packed with bright star clusters, and clouds of gas and dust. This picture is amongst the most detailed wide-field views of this object ever taken and shows the many glowing red gas clouds in the spiral arms with particular clarity.

His observations, made in 1924, proved conclusively that these nebulae were much too distant to be part of the Milky Way and were, in fact, entire galaxies outside our own, suspected by researchers at least as early as 1755 when Immanuel Kant’s General History of Nature and Theory of the Heavens appeared.

Edwin Hubble at Caltech Palomar Samuel Oschin 48 inch Telescope, (credit: Emilio Segre Visual Archives/AIP/SPL)

Edwin Hubble looking through a 100-inch Hooker telescope at Mount Wilson in Southern California

Mt Wilson 100 inch Hooker Telescope Interior

Mt Wilson 100 inch Hooker Telescope, perched atop the San Gabriel Mountains outside Los Angeles, CA, USA, Mount Wilson, California, US, Altitude 1,742 m (5,715 ft)

Henrietta Swan Leavitt was one of many women “computers” who worked at Harvard University, cataloging stars around the turn of the last century. Women could be paid less than men, and were generally seen as detail-oriented and suited for the often boring and rote work of data analysis. They were also barred from operating Harvard’s telescopes, limiting their other astronomical options. Leavitt’s particular assignment was Cepheid variable stars. These stars change how bright they are from day to day or week to week. And she noticed that, in general, the brighter stars had longer periods – the brighter the star, the longer it took to cycle through its variability.

At first, this was nothing more than a curiosity. It didn’t mean anything to anyone. But Leavitt made it very meaningful with her follow-up work. She looked at a sample of variable stars that were all near the same location, in the Small Magellanic Cloud.

Small Magellanic Cloud. NASA/ESA Hubble and ESO/Digitized Sky Survey 2

This is a tiny dwarf galaxy very near to our own Milky Way. Here, with a smaller sample, her trend was even clearer. Brighter stars had longer periods.

Leavitt realized something very important here, though it’s not clear many others did at the time. Because the stars in her second study were all in the same place, they were all essentially the same distance from Earth. So her discovery was telling her something intrinsic to the stars themselves: the longer a star took to change brightness, the brighter it actually was. So, if another star took a long time to change brightness but didn’t appear brighter, then she concluded it must be farther away, thus dimming its true brightness. With this simple relationship, Leavitt turned a two-dimensional picture of the sky into a 3D one.

Finishing the Scale

Leavitt herself pointed out that someone merely needed to work out the parallax (a way of calculating distance that works only on very nearby stars) of a tiny handful of her variable stars to calibrate the system, and turn her rough picture of “near or far” into an accurate map complete with marked distances. Within a year, another astronomer named Ejnar Hertzsprung had done so.

Perhaps Leavitt was a few years too early for her brilliant observation. Perhaps it was overlooked because she was a woman, and not allowed the status of a full researcher (though her name is on her own published work). Whatever the cause, this observation sat quietly for over a decade, until after Leavitt had suffered an early death due to cancer. It was only then that Edwin Hubble used her work to show how large the universe was, and that many of the fuzzy “nebulae” astronomers had observed for so long were actually far more distant than the stars in the Milky Way, and were in fact entire galaxies themselves.

Leavitt never earned fame in her own lifetime, nor a fancy telescope namesake afterward. But when looking up at the night skies, it’s worth remembering that she is part of the reason we have a three-dimensional map of the skies, instead of the flat picture that sustained humans for so much of our history.

See the full article here .

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

From Discover Magazine: “Big Bang Vote: IAU Debates Who Gets Credit For Expanding Universe”

From Discover Magazine

August 31, 2018
Krzysztof Bolejko

Captured: approximately 15,000 galaxies (12,000 of which are star-forming) widely distributed in time and space. (Credit: NASA, ESA, P. Oesch (University of Geneva), and M. Montes (University of New South Wales))

Astronomers are engaged in a lively debate over plans to rename one of the laws of physics.

It emerged overnight in Vienna at the 30th Meeting of the International Astronomical Union (IAU), in Vienna, where members of the general assembly considered a resolution on amending the name of the Hubble Law to the Hubble-Lemaître Law.

The resolution aims to credit the work of the Belgian astronomer Georges Lemaître and his contribution – along with the American astronomer Edwin Hubble – to our understanding of the expansion of the universe.

While most (but not all) members at the meeting were in favor of the resolution, it was decided to give all members of the International Astronomical Union a chance to vote. Subsequently, voting was downgraded to a straw vote and the resolution will formally be voted on by an electronic vote at a later date.

Giving all members a say via electronic voting was introduced following criticism of the IAU’s 2006 general assembly when a resolution to define a planet – that saw Pluto relegated to a dwarf-planet – was approved.

But changing the name of the Hubble Law raises the questions of who should be honored in the naming of the laws of physics, and whether the IAU should be involved in any decision.

Discovering The Big Bang

The expansion of the universe was one of the most mind-blowing discoveries of the 20th century.

Expansion here means that the distance between galaxies in general increases with time, and it increases uniformly. It does not matter where you are and in which direction you look at, you still see a universe that is expanding.

When you really try to imagine all of this, you may end up with a headspin or even worse, as satirically depicted by Woody Allen in his movie Annie Hall.

The rate at which the universe is currently expanding is described by the Hubble Law, named after Edwin Hubble who in 1929 published an article reporting that astronomical data signify the expansion of the universe.

Arno Penzias and Robert Wilson, AT&T, Holmdel, NJ USA, with the Holmdel horn antenna, first caught the faint echo of the Big Bang

Saul Perlmutter shared the 2006 Shaw Prize in Astronomy, the 2011 Nobel Prize in Physics, and the 2015 Breakthrough Prize in Fundamental Physics with Brian P. Schmidt and Adam Riess for providing evidence that the expansion of the universe is accelerating.

Hubble Was Not The First

In 1927, Georges Lemaître had already published an article on the expansion of the universe. His article was written in French and published in a Belgian journal.

Lemaître presented a theoretical foundation for the expansion of the universe, and used the astronomical data (the very same data that Hubble used in his 1929 article) to infer the rate at which the universe is expanding.

In 1928 the American mathematician and physicist Howard Robertson published an article in Philosophical Magazine and Journal of Science, where he derived the formula for the expansion of the universe and inferred the rate of expansion from the same data that were used by Lemaître (a year before) and Hubble (a year after).

Robertson did not know about Lemaître’s work. Given the limited popularity of the Belgian journal in which Lemaître’s paper appeared and the French language used, it is argued his remarkable discovery went largely unnoticed at the time by the astronomical community.

But the findings published by Hubble in 1929 were most likely influenced by Lemaître. In July 1928, Lemaître and Hubble met at the 3rd meeting of the International Astronomical Union, in Leiden. During the meeting they discussed the astronomical evidence suggesting the expansion of the universe.

The Expanding Universe

In January 1930 at the meeting of the Royal Astronomical Society in London, the English astronomer, physicist and mathematician Arthur Eddington raised the problem of the expansion of the universe and the lack of any theory that would satisfactory explain this phenomenon.

When Lemaître found about this, he wrote to Eddington to remind him about his 1927 paper, where he laid theoretical foundation for the expansion of the universe. Eddington invited Lemaître to republish the translation of the paper in Monthly Notices of the Royal Astronomical Society.

In the meantime, Hubble and the American astronomer Milton Humason published new results on the expansion of the universe in The Astrophysical Journal. This time the sample was larger and reaching regions more than ten times greater than before.

These new measurements made prior measurements of the expansion of the universe obsolete. Thus, when working on the translation, Lemaître removed from his article the paragraphs where he estimated the rate of the expansion of the universe.

As a result of this change, for people not familiar with the previous papers by Lemaître or Robertson, it looked like it was Hubble who was the first one to discover the expansion of the universe.

Lemaître was apparently not concerned with with establishing priority for his original discovery. Consequently, the formula that describes the present-day expansion rate bears the name of Hubble.

The resolution of the executive committee of the IAU wants to change the name to the Hubble-Lemaître Law, to honour Lemaître and acknowledge his part in the discovery.

Who Names The Stars?

The IAU was founded in 1919 and one of its activities is to standardise the naming of celestial objects and their definitions: from small asteroids, to planets and constellations.

The IAU comprises of Individual Members (more than 12,000 people from 101 countries) and National Members (79 different academies of science or national astronomical societies). The decisions made by IAU do not have any legislative power, but it does say:

The names approved by the IAU represent the consensus of professional astronomers around the world and national science academies, who as “Individual Members” and “National Members”, respectively, adhere to the guidelines of the International Astronomical Union.

It is thus reasonable to expect that if the resolution is passed then with time the new name will become more widely used.

IAU Vote

This resolution has serious implications. It seeks to acknowledge Lemaître for his involvement in one of the most fundamental discoveries on the behavior of our universe. At the same time, the resolution may set a precedent for future actions.

Will this initiate further changes? Will other disciplines follow the example set by astronomers?

Science is full of laws, effects, equations and constants that in many cases do not bear the name of their rightful discoverers. Some people worry that giving the due credit in all of such cases will cost a lot of effort and time.

Others will welcome this precedent and eagerly await when, for example, Henrietta Swan Leavitt will finally be properly acknowledged for the discovery of the period-luminosity relation.

For now, we have to wait for the result of the electronic voting.

See the full article here .

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition