Tagged: NASA/Cobe Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 8:47 am on July 18, 2018 Permalink | Reply
    Tags: , , , , , , , , NASA/Cobe   

    From European Space Agency: “From an almost perfect Universe to the best of both worlds” 

    ESA Space For Europe Banner

    From European Space Agency

    17 July 2018

    Jan Tauber
    ESA Planck Project Scientist
    European Space Agency
    Email: jan.tauber@esa.int

    Markus Bauer
    ESA Science Communication Officer
    Tel: +31 71 565 6799
    Mob: +31 61 594 3 954
    Email: markus.bauer@esa.int

    1
    CMB per Planck

    ESA/Planck 2009 to 2013

    It was 21 March 2013. The world’s scientific press had either gathered in ESA’s Paris headquarters or logged in online, along with a multitude of scientists around the globe, to witness the moment when ESA’s Planck mission revealed its ‘image’ of the cosmos. This image was taken not with visible light but with microwaves.

    Whereas light that our eyes can see is composed of small wavelengths – less than a thousandth of a millimetre in length – the radiation that Planck was detecting spanned longer wavelengths, from a few tenths of a millimetre to a few millimetres. Most importantly, it had been generated at very beginning of the Universe.

    Collectively, this radiation is known as the cosmic microwave background, or CMB. By measuring its tiny differences across the sky, Planck’s image had the ability to tell us about the age, expansion, history, and contents of the Universe. It was nothing less than the cosmic blueprint.

    Astronomers knew what they were hoping to see. Two NASA missions, COBE in the early 1990s and WMAP in the following decade, had already performed an analogous set of sky surveys that resulted in similar images. But those images did not have the precision and sharpness of Planck.

    COBE/CMB

    NASA/COBE 1989 to 1993.

    CMB per NASA/WMAP

    NASA/WMAP 2001 to 2010

    The new view would show the imprint of the early Universe in painstaking detail for the first time. And everything was riding on it.

    If our model of the Universe were correct, then Planck would confirm it to unprecedented levels of accuracy. If our model were wrong, Planck would send scientists back to the drawing board.

    When the image was revealed, the data had confirmed the model. The fit to our expectations was too good to draw any other conclusion: Planck had showed us an ‘almost perfect Universe’. Why almost perfect? Because a few anomalies remained, and these would be the focus of future research.

    Now, five years later, the Planck consortium has made their final data release, known as the legacy data release. The message remains the same, and is even stronger.

    All cosmological models are based upon Albert Einstein’s General Theory of Relativity. To reconcile the general relativistic equations with a wide range of observations, including the cosmic microwave background, the standard model of cosmology includes the action of two unknown components.

    Firstly, an attractive matter component, known as cold dark matter, which unlike ordinary matter does not interact with light. Secondly, a repulsive form of energy, known as dark energy, which is driving the currently accelerated expansion of the Universe. They have been found to be essential components to explain our cosmos in addition to the ordinary matter we know about. But as yet we do not know what these exotic components actually are.

    3
    CMB temperature and polarisation

    Planck was launched in 2009 and collected data until 2013. Its first release – which gave rise to the almost perfect Universe – was made in the spring of that year. It was based solely on the temperature of the cosmic microwave background radiation, and used only the first two sky surveys from the mission.

    The data also provided further evidence for a very early phase of accelerated expansion, called inflation, in the first tiny fraction of a second in the Universe’s history, during which the seeds of all cosmic structures were sown.

    Lambda-Cold Dark Matter, Accelerated Expansion of the Universe, Big Bang-Inflation (timeline of the universe) Date 2010 Credit: Alex Mittelmann Cold creation

    Yielding a quantitative measure of the relative distribution of these primordial fluctuations, Planck provided the best confirmation ever obtained of the inflationary scenario.

    Inflation

    4
    Alan Guth, from Highland Park High School and M.I.T., who first proposed cosmic inflation

    HPHS Owls

    Lambda-Cold Dark Matter, Accelerated Expansion of the Universe, Big Bang-Inflation (timeline of the universe) Date 2010 Credit: Alex MittelmannColdcreation

    Alan Guth’s notes:
    5

    Besides mapping the temperature of the cosmic microwave background across the sky with unprecedented accuracy, Planck also measured its polarisation, which indicates if light is vibrating in a preferred direction. The polarisation of the cosmic microwave background carries an imprint of the last interaction between the radiation and matter particles in the early Universe, and as such contains additional, all-important information about the history of the cosmos. But it could also contain information about the very first instants of our Universe, and give us clues to understand its birth.

    In 2015, a second data release folded together all data collected by the mission, which amounted to eight sky surveys. It gave temperature and polarisation but came with a caution.

    5
    5 February 2015 New maps from ESA’s Planck satellite uncover the ‘polarised’ light from the early Universe across the entire sky, revealing that the first stars formed much later than previously thought.

    “We felt the quality of some of the polarisation data was not good enough to be used for cosmology,” says Jan. He adds that – of course – it didn’t prevent them from doing cosmology with it but that some conclusions drawn at that time needed further confirmation and should therefore be treated with caution.

    And that’s the big change for this 2018 Legacy data release. The Planck consortium has completed a new processing of the data. Most of the early signs that called for caution have disappeared. The scientists are now certain that both temperature and polarisation are accurately determined.

    “Now we really are confident that we can retrieve a cosmological model based on solely on temperature, solely on polarisation, and based on both temperature and polarisation. And they all match,” says Reno Mandolesi, principal investigator of the LFI instrument on Planck at the University of Ferrara, Italy.

    6

    The history of the Universe

    “Since 2015, more astrophysical data has been gathered by other experiments, and new cosmological analyses have also been performed, combining observations of the CMB at small scales with those of galaxies, clusters of galaxies, and supernovae, which most of the time improved the consistency with Planck data and the cosmological model supported by Planck,” says Jean-Loup Puget, principal investigator of the HFI instrument on Planck at the Institut d’Astrophysique Spatiale in Orsay, France.

    This is an impressive feat and means that cosmologists can be assured that their description of the Universe as a place containing ordinary matter, cold dark matter and dark energy, populated by structures that had been seeded during an early phase of inflationary expansion, is largely correct.

    But there are some oddities that need explaining – or tensions as cosmologists call them. One in particular is related to the expansion of the Universe. The rate of this expansion is given by the so-called Hubble Constant.

    To measure the Hubble constant astronomers have traditionally relied on gauging distances across the cosmos. They can only do this for the relatively local Universe by measuring the apparent brightness of certain types of nearby variable stars and exploding stars, whose actual brightness can be estimated independently. It is a well-honed technique that has been developed over the course of the last century, pioneered by Henrietta Leavitt and later applied, in the late 1920s, by Edwin Hubble and collaborators, who used variable stars in distant galaxies and other observations to reveal that the Universe was expanding.

    7
    Measurements of the Hubble constant
    Released 17/07/2018 3:00 pm
    Copyright ESA/Planck Collaboration

    The evolution of measurements of the rate of the Universe’s expansion, given by the so-called Hubble Constant, over the past two decades. The slightly esoteric units give the velocity of the expansion in km/s for every million parsecs (Mpc) of separation in space, where a parsec is equivalent to 3.26 light-years.
    In recent years, the figure astronomers derive for the Hubble Constant using a wide variety of cutting-edge observations to gauge distances across the cosmos is 73.5 km/s/Mpc, with an uncertainty of only two percent. These measurements are shown in blue.
    Alternatively, the Hubble Constant can also be estimated from the cosmological model that fits observations of the cosmic microwave background, which represents the very young Universe, and calculate a prediction for what the Hubble Constant should be today. Measurements based on this method using data from NASA’s WMAP satellite are shown in green, and those obtained using data from ESA’s Planck mission are shown in red.
    When applied to Planck data, this method gives a lower value of 67.4 km/s/Mpc, with a tiny uncertainty of less than a percent.

    On the one hand, it is extraordinary that two such radically different ways of deriving the Hubble constant – one using the local, mature Universe, and one based on the distant, infant Universe – are so close to each other. On the other hand, in principle these two figures should agree to within their respective uncertainties, causing what cosmologists call a ‘tension’ – an oddity that still needs explaining.

    The single purple point is a measurement obtained through yet another method, using data from the first simultaneous observation of light and gravitational waves emitted by the same source – a pair of coalescing neutron stars.

    The figure astronomers derive for the Hubble Constant using a wide variety of cutting-edge observations, including some from Hubble’s namesake observatory, the NASA/ESA Hubble Space Telescope, and most recently from ESA’s Gaia mission, is 73.5 km/s/Mpc, with an uncertainty of only two percent. The slightly esoteric units give the velocity of the expansion in km/s for every million parsecs (Mpc) of separation in space, where a parsec is equivalent to 3.26 light-years.

    NASA/ESA Hubble Telescope

    ESA/GAIA satellite

    A second way to estimate the Hubble Constant is to use the cosmological model that fits the cosmic microwave background image, which represents the very young Universe, and calculate a prediction for what the Hubble Constant should be today. When applied to Planck data, this method gives a lower value of 67.4 km/s/Mpc, with a tiny uncertainty of less than a percent.

    On the one hand, it is extraordinary that two such radically different ways of deriving the Hubble constant – one using the local, mature Universe, and one based on the distant, infant Universe – are so close to each other. On the other hand, in principle these two figures should agree to within their respective uncertainties. This is the tension, and the question is how can they be reconciled?

    Both sides are convinced that any remaining errors in their measurement methodologies are now too small to cause the discrepancy. So could it be that there is something slightly peculiar about our local cosmic environment that makes the nearby measurement somewhat anomalous? We know for example that our Galaxy sits in a slightly under-dense region of the Universe, which could affect the local value of the Hubble constant. Unfortunately, most astronomers think that such deviations are not large enough to resolve this problem.

    “There is no single, satisfactory astrophysical solution that can explain the discrepancy. So, perhaps there is some new physics to be found,” says Marco Bersanelli, deputy principal investigator of the LFI instrument at the University of Milan, Italy.

    ‘New physics’ means that exotic particles or forces could be influencing the results. Yet, as exciting as this prospect feels, the Planck results place severe constraints on this train of thought because it fits so well with the majority of observations.

    “It is very hard to add new physics alleviating the tension and still keep the standard model’s precise description of everything else that already fits,” says François Bouchet, deputy principal investigator of the HFI instrument at the Institut d’Astrophysique de Paris, France.

    As a result, no one has been able to come up with a satisfactory explanation for the differences between the two measurements, and the question remains to be resolved.

    “For the moment, we shouldn’t get too excited about finding new physics: it could well be that the relatively small discrepancy can be explained by a combination of small errors and local effects. But we need to keep improving our measurements and thinking about better ways to explain it,” says Jan.

    This is the legacy of Planck: with its almost perfect Universe, the mission has given researchers confirmation of their models but with a few details to puzzle over. In other words: the best of both worlds.

    Notes for Editors
    A series of scientific papers describing the new results was published on 17 July and can be downloaded here.

    The Planck Legacy Archive
    More about Planck

    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 European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

    ESA50 Logo large

     
  • richardmitnick 4:29 pm on October 15, 2017 Permalink | Reply
    Tags: , , , , , NASA/Cobe,   

    From Goddard: “NASA’s James Webb Space Telescope and the Big Bang: A Short Q&A with Nobel Laureate Dr. John Mather” 

    NASA Goddard Banner
    NASA Goddard Space Flight Center

    Oct. 11, 2017
    Maggie Masetti
    NASA’s Goddard Space Flight Center

    1
    Dr. John Mather, a Nobel laureate and the senior project scientist for NASA’s James Webb Space Telescope. Credits: NASA/Chris Gunn

    Q: What is the Big Bang?

    A: The Big Bang is a really misleading name for the expanding universe that we see. We see an infinite universe with distant galaxies all rushing away from each other.

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    The name Big Bang conveys the idea of a firecracker exploding at a time and a place — with a center. The universe doesn’t have a center, at least not one we can find. The Big Bang happened everywhere at once and was a process happening in time, not a point in time. We know this because 1) we see galaxies rushing away from each other, not from a central point; 2) we see the heat that was left over from early times, and that heat uniformly fills the universe; and 3) we can calculate and imagine what the universe was like when the parts were much closer together, and the calculations match everything we can see.

    Q: Can we see the Big Bang?

    A: No, the Big Bang itself is not something we can see.

    Q: What can we see?

    A: We can see the heat radiation that was there when the universe was young. We see this heat as it was about 380,000 years after the expansion of the universe began 13.8 billion years ago (which is what we refer to as the Big Bang). This heat covers the entire sky and fills the universe. (In fact it still does.) We were able to map it with satellites we (NASA and ESA) built called the Cosmic Background Explorer (COBE), the Wilkinson Microwave Anisotropy Probe (WMAP), and Planck. The universe at this point was extremely smooth, with only tiny ripples in temperature.

    Cosmic Infrared Background, Credit: Michael Hauser (Space Telescope Science Institute), the COBE/DIRBE Science Team, and NASA

    NASA/COBE

    1
    All-sky image of the infant universe, created from nine years of data from the Wilkinson Microwave Anisotropy Probe (WMAP).
    Credits: NASA/WMAP Science Team

    NASA/WMAP

    CMB per ESA/Planck


    ESA/Planck

    Q: I heard the James Webb Space Telescope will see back further than ever before. What will Webb see?

    NASA/ESA/CSA Webb Telescope annotated

    A: COBE, WMAP, and Planck all saw further back than Webb, though it’s true that Webb will see farther back than Hubble.

    NASA/ESA Hubble Telescope

    Webb was designed not to see the beginnings of the universe, but to see a period of the universe’s history that we have not seen yet.

    Lambda-Cold Dark Matter, Accelerated Expansion of the Universe, Big Bang-Inflation (timeline of the universe) Date 2010 Credit: Alex MittelmannColdcreation

    Specifically, we want to see the first objects that formed as the universe cooled down after the Big Bang. That time period is perhaps hundreds of millions of years later than the one COBE, WMAP, and Planck were built to see. We think that the tiny ripples of temperature they observed were the seeds that eventually grew into galaxies. We don’t know exactly when the universe made the first stars and galaxies — or how for that matter. That is what we are building Webb to help answer.

    Q: Why can’t Hubble see the first stars and galaxies forming?

    A: The only way we can see back to the time when these objects were forming is to look very far away. Hubble isn’t big enough or cold enough to see the faint heat signals of these objects that are so far away.

    Q: Why do we want to see the first stars and galaxies forming?

    A: The chemical elements of life were first produced in the first generation of stars after the Big Bang. We are here today because of them — and we want to better understand how that came to be! We have ideas, we have predictions, but we don’t know. One way or another the first stars must have influenced our own history, beginning with stirring up everything and producing the other chemical elements besides hydrogen and helium. So if we really want to know where our atoms came from, and how the little planet Earth came to be capable of supporting life, we need to measure what happened at the beginning.

    Dr. John Mather is the senior project scientist for the James Webb Space Telescope. Dr. Mather shares the 2006 Nobel Prize for Physics with George F. Smoot of the University of California for their work using the COBE satellite to measure the heat radiation from the Big Bang.

    The James Webb Space Telescope, the scientific complement to NASA’s Hubble Space Telescope, will be the premier space observatory of the next decade. Webb is an international project led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).

    For more information about the Webb telescope, visit: http://www.webb.nasa.gov or http://www.nasa.gov/webb

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    NASA’s Goddard Space Flight Center is home to the nation’s largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe.

    Named for American rocketry pioneer Dr. Robert H. Goddard, the center was established in 1959 as NASA’s first space flight complex. Goddard and its several facilities are critical in carrying out NASA’s missions of space exploration and scientific discovery.


    NASA/Goddard Campus

     
  • richardmitnick 1:01 pm on July 17, 2017 Permalink | Reply
    Tags: , , , , , , , How big is the universe?, , NASA/Cobe   

    From COSMOS: “How big is the universe?” 

    Cosmos Magazine bloc

    COSMOS

    17 July 2017
    Cathal O’Connell

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    “Space is big. You just won’t believe how vastly, hugely, mind- bogglingly big it is. I mean, you may think it’s a long way down the road to the chemist’s, but that’s just peanuts to space.” – Douglas Adams, Hitchhikers Guide to the Galaxy.

    In one sense the edge of the universe is easy to mark out: it’s the distance a beam of light could have travelled since the beginning of time. Anything beyond is impossible for us to observe, and so outside our so-called ‘observable universe’. You might guess that the distance from the centre of the universe to the edge is simply the age of the universe (13.8 billion years) multiplied by the speed of light: 13.8 billion light years.

    But space has been stretching all this time; and just as an airport walkway extends the stride of a walking passenger, the moving walkway of space extends the stride of light beams. It turns out that in the 13.8 billion years since the beginning of time, a light beam could have travelled 46.3 billion light years from its point of origin in the Big Bang. If you imagine this beam tracing a radius, the observable universe is a sphere whose diameter is double that: 92.6 billion light years.

    “Since nothing is faster than light, absolutely anything could in principle happen outside the observable universe,” says Andrew Liddle, an astronomer at the University of Edinburgh. “It could end and we’d have no way of knowing.”

    But we have good reasons to suspect the entire Universe (capitalised now to distinguish from the merely observable universe) goes on a lot further than the part we can observe – and that it is possibly infinite. So how can we know what goes on beyond the observable universe?

    Imagine a bacterium swimming in a fishbowl. How could it know the true extent of its seemingly infinite world? Well, distortions of light from the curvature of the glass might give it a clue. In the same way, the curvature of the universe tells us about its ultimate size.

    “The geometry of the universe can be of three different kinds,” says Robert Trotta, an astrophysicist at Imperial College London. It could be closed (like a sphere), open (like a saddle) or flat (like a table).

    2
    Universal geometry: the universe could be closed like sphere, open like a saddle or flat like a table. The first option would make it finite; the other two, infinite.
    Cosmos Magazine.

    The key to measuring its curvature is the cosmic microwave background (CMB) radiation – a wash of light given out by the fireball of plasma that pervaded the universe 400,000 years after the Big Bang. It’s our snapshot of the universe when it was very young and about 1,000 times smaller than it is today.

    Cosmic Infrared Background, Credit: Michael Hauser (Space Telescope Science Institute), the COBE/DIRBE Science Team, and NASA

    NASA/COBE

    Cosmic Microwave Background NASA/WMAP

    NASA/WMAP satellite

    CMB per ESA/Planck

    ESA/Planck

    Just as ancient geographers once used the curviness of the Earth’s horizon to work out the size of our planet, astronomers are using the curvinesss of the CMB at our cosmic horizon to estimate the size of the universe.

    The key is to use satellites to measure the temperature of different features in the CMB. The way these features distort across the CMB landscape is used to calculate its geometry. “So determining the size and geometry, of the Universe helps us determine what happened right after its birth,” Trotta says.

    Since the late 1980s, three generations of satellites have mapped the CMB with ever improving resolution, generating better and better estimates of the universe’s curvature. The latest data, released in March 2013, came from the European Space Agency’s Planck telescope. It estimated the curvature to be completely flat, at least to within a measurement certainty of plus or minus 0.4%.

    The extreme flatness of the universe supports the theory of cosmic inflation. This theory holds that in a fraction of a second (10−36 second to be precise) just after its birth, the universe inflated like a balloon, expanding many orders of magnitude while stretching and flattening its surface features.

    Perfect flatness would mean the universe is infinite, though the plus or minus 0.4% margin of error means we can’t be sure. It might still be finite but very big. Using the Planck data, Trotta and his colleagues worked out the minimum size of the actual Universe would have to be at least 250 times greater than the observable universe.

    The next generation of telescopes should improve on the data from the Planck telescope. Whether they will give us a definitive answer about the size of the universe remains to be seen. “I imagine that we will still treat the universe as very nearly flat and still not know well enough to rule out open or closed for a long time to come,” says Charles Bennet, head of the new CLASS array of microwave telescopes in Chile.

    As it turns out, owing to background noise there are fundamental limits to how well we can ever measure the curvature, no matter how good the telescopes get. In July 2016, physicists at Oxford worked out we cannot possibly measure a curvature below about 0.01%. So we still have a ways to go, though measurements so far, and the evidence from inflation theory, has most physicists weighing toward the view the universe is probably infinite. An impassioned minority, however, have had a serious problem with that.

    Getting rid of infinity, the great British physicist Paul Dirac said, is the most important challenge in physics. “No infinity has ever been observed in nature,” notes Columbia University astrophysicist Janna Levin in her 2001 memoir How the Universe got its Spots. “Nor is infinity tolerated in a scientific theory.”

    So how come physicists keep allowing that the universe itself may be infinite? The idea goes back to the founding fathers of physics. Newton, for example, reasoned that the universe must be infinite based on his law of gravitation. It held that everything in the universe attracted everything else. But if that were so, eventually the universe would be pulled towards a single point, in the way that a star eventually collapses under its own weight. This was at odds with his firm belief the universe had always existed. So, he figured, the only explanation was infinity – the equal pull in all directions would keep the universe static, and eternal.

    Albert Einstein, 250 years later at the start of the 20th century, similarly envisioned an eternal and infinite universe. General relativity, his theory of the universe on the grandest scales, plays out on an infinite landscape of spacetime.

    Mathematically speaking, it is easier to propose a universe that goes on forever than to have to deal with the edges. Yet to be infinite is to be unreal – a hyperbole, an absurdity.

    In his short story The Library of Babel, Argentinian writer Jorge Luis Borges imagines an infinite library containing every possible book of exactly 410 pages: “…for every sensible line of straightforward statement, there are leagues of senseless cacophonies, verbal jumbles and incoherences.” Because there are only so many possible arrangements of letters, the possible number of books is limited, and so the library is destined to repeat itself.

    An infinite Universe leads to similar conclusions. Because there are only so many ways that atoms can be arranged in space (even within a region 93 billion light years across), an infinite Universe requires that there must be, out there, another huge region of space identical to ours in every respect. That means another Milky Way, another Earth, another version of you and another of me.

    Physicist Max Tegmark, of the Massachusetts Institute of Technology, has run the numbers. He estimates that, in an infinite Universe, patches of space identical to ours would tend to come along about every 1010115 metres (an insanely huge number, one with more zeroes after it than there are atoms in the observable universe). So no danger of bumping into your twin self down at the shops; but still Levin does not accept it: “Is it arrogance or logic that makes me believe this is wrong? There’s just one me, one you. The universe can’t be infinite.”

    Levin was one of the first theorists to approach general relativity from a new perspective. Rather than thinking about geometry, which describes the shape of space, she looked at its topology: the way it was connected.

    All those assumptions about flat, closed or open universes were only valid for huge, spherical universes, she argued. Other shapes could be topologically ‘flat’ and still finite.

    “Your idea of a donut-shaped universe is intriguing, Homer,” says Stephen Hawking in a 1999 episode of The Simpsons. “I may have to steal it.” Actually, the show’s writers had already stolen the idea from Levin—who published her analysis of a donut-shaped universe in 1998.

    A donut, she noted, actually had – “topologically speaking” – zero curvature because the negative curvature on the inside is balanced by the positive curvature on the outside. The (near) zero curvature measured in the CMB was therefore as consistent with a donut as with a flat surface.

    5
    One ring theory to rule them all: CMB data doesn’t rule out a donut-shape, but it would be an awfully big one. Mehau Kulyk / Getty Images.

    In such a universe, Levin realised, you might cross the cosmos in a spaceship, the way sailors crossed the globe, and find yourself back where you started. This idea inspired Australian physicist Neil Cornish, now based at Montana State University, to think about how the very oldest light, from the CMB, might have circumnavigated the cosmos. If the donut universe were below a threshold size, that would create a telltale signature, which Cornish called “circles in the sky”. Alas, when CMB data came back from the Wilkinson Microwave Anisotropy Probe (WMAP) in 2001, no such signatures were found. That doesn’t rule out the donut theory entirely; but it does mean that the universe, if it is a donut, is an awfully big one.

    Attempts to directly prove or disprove the infinity of the universe seem to lead us to a dead-end, at least with current technology. But we might do it by inference, Cornish believes. Inflation theory does a compelling job of explaining the key features of our universe; and one of the offshoots of inflation is the multiverse theory.

    It’s the kind of theory that, when you first hear it, seems to have sprung from the mind of a science-fiction author indulging in mind-expanding substances. Actually it was first proposed by influential Stanford physicist Andrei Linde in the 1980s. Linde – together with Alan Guth at MIT and Alexei Starobinsky at Russia’s Landau Institute for Theoretical Physics – was one of the architects of inflation theory.

    Guth and Starobinsky’s original ideas had inflation petering out in the first split second after the big bang; Linde, however, had it going on and on, with new universes sprouting off like an everlasting ginger root.

    Linde has since showed that “eternal inflation” is probably an inevitable part of any inflation model. This eternal inflation, or multiverse, model is attractive to Linde because it solves the greatest mystery of all: why the laws of physics seem fine-tuned to allow our existence.

    The strength of gravity is just enough to allow stable stars to form and burn, the electromagnetic and nuclear forces are just the right strength to allow atoms to form, for complex molecules to evolve, and for us to come to be.

    In each newly sprouted universe these constants get assigned randomly. In some, gravity might be so strong that the universe recollapses immediately after its big bang. In others, gravity would be so weak that atoms of hydrogen would never condense into stars or galaxies. With an infinite number of new universes sprouting into and out of existence, by chance one will pop up that is fit for life to evolve.

    6
    Infinite variety: in the the eternal inflation model, new universes sprout off like an everlasting ginger root. Andrei Linde.

    The multiverse theory has its critics, notably another co-founder of inflation theory, Paul Steinhardt. who told Scientific American in 2014: “Scientific ideas should be simple, explanatory, predictive. The inflationary multiverse as currently understood appears to have none of those properties.” Meanwhile Paul Davies at the University of Arizona wrote in The New York Times that “invoking an infinity of unseen universes to explain the unusual features of the one we do see is just as ad hoc as invoking an unseen creator”.

    But in another sense the multiverse is the simpler of the two inflation models. In a few lines of equations, or just a few sentences of speech, the multiverse gives us a mechanism to explain the origin of our universe, just as Charles Darwin’s theory of natural selection explained the origin of species. As Max Tegmark puts it: “Our judgment therefore comes down to which we find more wasteful and inelegant: many worlds or many words.”

    To settle the issue, we will need to know more about what went down in the first split-second of the universe. Perhaps gravitational waves will be the answer, a way to ‘hear’ the vibrations of the big bang itself.

    Whether infinite or finite, stand-alone or one of an endless multitude, the universe is surely a mindbending place. Which brings us back to The Hitchhiker’s Guide to the Galaxy: “If there’s any real truth, it’s that the entire multidimensional infinity of the Universe is almost certainly being run by a bunch of maniacs.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
c
Compose new post
j
Next post/Next comment
k
Previous post/Previous comment
r
Reply
e
Edit
o
Show/Hide comments
t
Go to top
l
Go to login
h
Show/Hide help
shift + esc
Cancel
%d bloggers like this: