National Geographic
Menu

Nobel Prize in Physics 2011–The Accelerating Universe

Text by J. Richard Gott

The 2011 Nobel Prize in Physics has been awarded to Adam Riess, Brian Schmidt, and Saul Perlmutter for their discovery of the accelerating expansion of the universe.  It is one of the times when astronomers have won the Nobel Prize in Physics.  It is perhaps the most important scientific discovery of the last quarter of the 20th  Century.   (The most important scientific discovery of the previous quarter century? Watson and Crick’s discovery of the structure of DNA.)

What does this discovery mean?  Why is the accelerated expansion of the universe so important? Einstein showed, in his theory of general relativity, that gravity is due to the curvature of spacetime.  His theory has been tested many times.  Most spectacularly, he predicted that the Sun should bend light rays from distant stars passing near it.  This effect was observed in 1919 and Einstein’s prediction was verified, whereas the prediction Newton’s theory would have made was shown to be wrong.  Einstein overturned Newton.  To use a sports analogy, it was the play of the century in physics–Einstein stole the

Galaxies in Every Direction

Map of Galaxies

ball from Newton and sunk the basket.  And the theory of gravity was the most important thing Newton ever did.  This catapulted Einstein to world fame.  He entered the ranks with Newton and Darwin.  In developing his theory, he realized that, for the laws to look the same for all moving observers (i.e., for them to be relativistically invariant), the source of the gravitational field had to include pressure as well as mass-energy density.  This is something Newton wouldn’t have thought of.  Pressure gravitates as well as mass-energy density.  This is encompassed in something called stress-energy.  Einstein postulated that stress-energy causes curvature.  If you knew the amount of stress-energy at a given location at a given time, you could calculate the curvature of spacetime there.  Planets and light beams simply followed the straightest possible trajectories in this curved spacetime–like an airliner follows a straight great-circle route when flying over the curved surface of the Earth from New York to Tokyo.  When Einstein worked out the equations, they showed how stress-energy caused spacetime to curve.  His equations guaranteed local energy conservation (in the same way that Maxwell’s equations of electricity and magnetism guaranteed charge conservation).

Einstein applied his new equations to cosmology.  He liked the idea of a static universe (one that neither expands nor contracts)–but he found that his equations would not produce one.  So he added a term to the curvature side of the equation called the cosmological constant.  This added term was designed to preserve the property of local energy conservation.  This made a static universe possible–the repulsive effects of the cosmological constant exactly balanced the gravitational attraction of the matter, keeping the model static.  However, in 1922 Friedmann published a paper where he used Einstein’s original equations without the cosmological constant term to show that the universe must be dynamical.  It starts with a big bang and expands.  Space itself expands–a remarkable concept.  Galaxies move apart as the space between them expands.  Again, this is something Newton would not have thought of.  In 1929, Hubble discovered the expansion of the universe when he observed that galaxies really were moving apart just as Friedmann had predicted.  Einstein then called the cosmological constant his “biggest blunder.”  If he had never invented it, he might have written Friedmann’s paper and predicted an expanding universe ahead of Hubble.

The Friedmann big bang model was triumphant.  In 1948 Gamow, Herman, and Alpher used it to predict that the early universe should be hot and that the hot radiation present back then should still be batting around today as a microwave background.  In 1965 Penzias and Wilson discovered this cosmic microwave background radiation, for which they later won the Nobel Prize in Physics in 1978.  But there were problems.  The thermal radiation was very uniform and there was not enough time in the early universe for the different parts we see to reach the same temperature.  In 1981, Alan Guth proposed a theory of inflation to explain this.  Move the cosmological constant from the curvature side of Einstein’s equations to the stress-energy side and it becomes a quantum vacuum state that has a positive energy density and a negative pressure.  The negative pressure has a negative gravitational effect–it causes a gravitational repulsion.  Since pressure operates in three directions in space (up-down, left-right, front-back), the gravitational repulsive effects of the negative pressure outweigh the gravitational attraction of the energy density of the vacuum by a factor of three to one, making the overall effect of this vacuum energy density and vacuum pressure repulsive.

Even if the universe starts off at rest, this gravitational repulsion starts the universe expanding.  Then it expands faster and faster.  It is an accelerated expansion.  The universe doubles in size every 10-35 seconds.   Inflation causes the big bang explosion and explains why the universe is so large today.  This period of inflation creates a tiny extra amount of time when the universe was very small which allows the different parts we see to come into contact with each other, thereby explaining the isotropy of the universe we observe.  Eventually, the quantum vacuum state decays, dumping its energy into the form of thermal radiation–and the big bang Friedmann model takes over.  Random quantum fluctuations occur, and this leads, through the action of gravity operating over 13.7 billion years, to the formation of the galaxies and clusters of galaxies we see today.

 

Cosmic Microwave Background Radiation

Map of the Cosmic Microwave Background Radiation

Scientists were anxious to determine the energy density of the universe, which according to Friedmann  would determine the future fate of the universe.  If the density were above a critical density, the universe would continue slowing down in its expansion due to the gravitational attraction of the galaxies for each other, and the whole universe would collapse in a big crunch at some future time.  If the universe was below that critical density, it would continue expanding forever.  The fate of the universe could thus be determined today by measuring how fast the expansion of the universe was decelerating–how fast its expansion rate was slowing down.    Two teams set out to measure this using distant supernovae.  Saul Perlmutter led one team at Berkeley.  When Bob Kirshner arrived at Harvard from the University of Michigan, he was already a world expert on supernovae and got people there interested in using supernovae to measure distances. Brian Schmidt formed a team at Harvard, including Bob Kirschner and Adam Riess,  to use large-redshift supernovae to measure the deceleration of the universe, like the Perlmutter team at Berkeley.  They determined the distances to supernovae by measuring their brightness.  They used Type Ia supernovae, which were caused by the collapse of white dwarf stars.  Since such white dwarf stars always collapse when they reach a critical Chandrasekhar mass limit of 1.4 solar masses, all these supernovae were quite alike and could be used as standard candles.  If you know the intrinsic brightness of a supernova, and how bright it appears in the telescope, you can determine how far away it is.  Bill Press came up with an algorithm to further improve these brightness estimates.  If you measure the redshift of lines in the specturm of a supernova, you can find out how big the universe was (relative to today) when the supernova exploded (because wavelengths of light coming from the supernova stretch with space as the universe expands.)  Chart the distances of supernovae as a function of their redshift and you can construct a graph of the expansion history of the universe.  When Adam Riess first looked at the results, he was quite surprised–the expansion of the universe was not decelerating, but accelerating–it was expanding faster and faster!  The most likely explanation was that old cosmological constant term of Einstein!  The two teams came to the same conclusion and reported their results in 1998.   The editors of Science magazine put a cartoon of Einstein on the cover happily blowing bubbles from his pipe to celebrate the event.

 

Sloan Great Wall of Galaxies

Eastern End of Sloan Great Wall

Today, most physicists, influenced by inflation, would put this cosmological constant term over on the stress-energy side of Einstein’s equations and call it dark energy.   It’s called dark because you can’t see it and energy because it is an energy density that fills the vacuum of space.  And it has a negative pressure.

Later Adam Riess used the Hubble Space Telescope to observe very distant supernovae and found that at earlier times the universe was decelerating just as expected.   As the universe expands, dark energy stays at nearly constant energy density and, as the matter in the universe thins out, the dark energy begins to dominate.  Once that occurs, the universe goes from an expansion that is slowing down to an expansion that is becoming faster and faster.  In the future we expect the universe to begin to double in size approximately every 10 billion years.  It will be an exponential expansion, just like we had in the early universe in inflation.  The repulsive effects of dark energy seem to guarantee that the universe will continue to expand forever.  No big crunch.  The Nobel press release emphasized this–saying if things continue this way the world will end not in fire but in ice.  Today dark energy comprises 73% of the universe.  It is most of the stuff in the universe.  To discover most of the stuff in the universe at this late date is quite an amazing accomplishment.

The Nobel committee awarded half the prize to Perlmutter and one quarter of the prize each to Schmidt and Riess.  Perlmutter and Schmidt were the two team leaders. They effectively split the prize equally between the two teams.

For the Harvard team the prize was split between the team leader and Riess who made particularly crucial contributions.  For example, he was the first author on the Harvard team’s discovery paper.  The rules say that the Noble Prize can only be split among at most three people.  Since many people work together in large groups today, in many years when the Nobel Prize is awarded there are usually additional people who participate in the discovery and come close to winning as well.  When describing this discovery in our National Geographic book Sizing Up the Universe, co-authored by Bob Vanderbei, we gave credit to “Adam Riess, Saul Perlmutter, Brian Schmidt, Robert Kirshner, Alex Filippenko and their colleagues” for the discovery.  Congratulations to them all!

 

Comments

  1. Karen Otten
    United States
    March 7, 9:34 pm

    Why no response by science guys to Wardell’s arithmetic from July 2012? He just blew you all away or he was blowing bubbles that looked like numbers? I’m not a science guy, so I wouldn’t know. But the math looked awesome in a picturesque kind of way, and I am capable of observing that no one responded.

  2. Jaime F. Soto, EE
    Santiago de Chile
    June 15, 2013, 4:02 pm

    In my opinion the “Big-Bang”, and the “accelerated” universe expansion are optical illusions

    May be that the interaction between photons with gravitational fields and plasma particles after traveling billions of light years since the emission instant at some initial wavelength, makes them go gradually loosing energy by enlarging their wave length, thus making complete collections of spectral peaks to go gradually shifting up in their wavelengths in the same percentage, even after traveling through very weak gravitational fields and plasma particle densities of just a few per cubic kilometer

    This could be proved focusing two radio telescopes to the respective replicated images of a galaxy whose rays arrive us in asymmetrical angles around a gravitational lens, and concentrating the whole radiation of each image through optical fibers towards the inputs of a SIS mixer, and doing spectral analysis of the SIS output, looking for spectral peaks well below the GHz range, as a result of an heterodyning effect between respective spectral peaks of the same collection, with their frequencies shifted down by subtle factors, say 0.9999 and 0.99991, so whole spectral peak collections should appear replicated with their frequencies scaled down by a very small factor, say 0.00001

    See this link

    http://en.wikipedia.org/wiki/Fritz_Zwicky

  3. Virgo Pihlapuu
    Tartu
    September 23, 2012, 4:04 am

    Kevin Wilson is thinking the right way. I also got the same idea about the “illusion” of accelerating expansion of the universe and started to look if really noone sees it through. Whoever approved this theory, did not use the full relativistic picture of the universe. If even I see this and im not alone, then i guess many physicist already have sent this idea to publishers.
    Interesting is to think if there will be 2 nobel prizes for one theory: one for saying that universe expansion is accelerating and otherone that it is not :D

  4. Kevin wilson
    United States
    September 6, 2012, 11:20 am

    Hey I have just proved the universe is in fact decelerating. You see the problem is that all astronomers have been thinking that the movements in distant galaxies is what they are doing now. However in reality the light we are receiving left the most distant galaxies billions of years ago. So we are seeing what they were doing not what they are doing now. So dark energy is a myth, gravity is slowing everything down at a constant rate as indicated by hubbles law.
    I have already sent this theory to several publishers, I hope to win the Nobel prize for this next year. :)

  5. George Davies
    Spring Lake. Mich
    July 20, 2012, 11:54 am

    Excellent description of Dark Energy but our daily movement from one space to another which takes a measurable amount of time along with the fact that initial components of the Big Bang needed space to originate in seems contrary to the thinking that this event created space. If indeed we moving ever faster away from something then we must be moving ever faster through something new.

  6. Wardell
    July 16, 2012, 2:07 pm

    This a very informative article. However, is it conceivable that the Universe is not expanding and in reality it is collapsing?
    Edwin Hubble did not agree with the current interpretation of the redshift, that it indicated expansion. Hubble thought the redshift was “an hitherto unrecognized principle of nature”.
    I have figured iut the redshift and it is related to the mysterious “Dark Energy. The Dark Energy is the momentum energy cmV=cP. This energy is ignored by Newton and Einstein’s Gravity Theories. The proper Theory oif Gravity is
    W= -mGm/r + cmV = m[-u/r, cV]

    This is the Total Energy and is a Quaternion Energy consisting of a scalar energy -mu/r and the vector energy cmV. In Newton’s Gravity model, the motion energy o mass m is not included, adding cmV is just that energy.
    This is the Dark Energy and it is larger than mu/r = mv2.

    The Divergence of cmV is the centrifugal (out seeking) force, f= cmDel.V cos(V), this is the so-called anti-gravity force.
    This force balances the centripetal gravity force mv2/r. Nature seems to want Continuity and the two forces balance.
    mv2/r = cmv/r cos(V) At this balance v/c = cos(V) the redshift is derived. The redshift is like the Fine Structure Constant for gravity.

    Now, if the redshift is increasing, theis indicates increased gravity no less and the the velocity goes up, but the distance to the origin decreases. This is a picture of the Universe collapsing..

    Newton’s gravity simply needs to add the vector energy to account for the astronomy findings. Gravity Energy is a Quaternion Energy: W= -mu/r + cmV

    PS Newton’s Deflection is
    Tan A= s/R = .5gt2/R= .5×9.8x500x500/1500 e-6= 8.1666E-6. This Deflection angle is 1.68″.

  7. Aaqib shah
    New DELHI
    May 12, 2012, 3:30 am

    I surly agree with the statment that”one day the universe will end,but not in fumes of hotness rather in freezing,cold&chilly conitions.Thankfully valve of universe is being analyzed.

  8. SEAN BATEMAN
    south africa.
    May 9, 2012, 9:54 am

    if the universe is accelerating,that means space is accelerating and space has got a mass[10-29 grams per cm cubed] can this mass not increase due to special relativity,and the faster the universe accelerates the heavier it gets.

  9. [...] it gets tougher. Even though astronomers have an a tape measure for the cosmos, the universe is expanding at an accelerating rate. Since space itself is expanding, that means that the astronomers’ ruler also needs to [...]

  10. Karen Sherry Brackett
    Johnson City Tennessee
    April 15, 2012, 2:24 pm

    Mr. Vanderbei,
    Thank you for your response. As well, I agree that 6,000 years is just yesterday on scale with the cosmos. Mainly, I wanted to confirm the state of the planet 6,000 years ago. Moses strikes me as rather knowledgeable for his time. Naturally, he had no way of knowing exactly how his theories worked. Even Darwin after studying to be a priest based his theory of the Origin of Species on Moses’ work in Genesis 1:20. Genesis by the way being the Greek word for Origin is the name of Moses‘ first book in the Bible. Moses accounts for all the time before Adam as not being countable basically. He constructs a situation where time begins when knowledge begins for Adam which is the proverbial apple moment in the Garden of Eden. No one really knows how long Adam lived prior to the creation of Eve or how long man stayed in the garden so to speak before Adam finally bit into the Apple. It is very possible we were colonized here by “God” . I often wondered if Hubble based his theory on the Earth coming before the stars on Genesis as well. Have you studied the Bible and drawn any basis for your work upon it? Given man’s genetic code for nipples there is biological evidence for the possibility of Moses’ work having some insight which today’s biologists seem to over look. Eve might have been God’s inspired mutation to humankind. If any of this is the case I believe we as scientists owe it to ourselves and to the human race to study the Bible with an open mind. More and more I am convinced of Intelligent Design and convinced that histories of the Bible may be far more important than we realize when viewed through science. This statement is meant in no way to take away from the divinity of God but rather to bring more understanding of His wisdom.

  11. Syauqy amin
    Malaysia
    March 22, 2012, 11:57 am

    Very nice article to prove that , we are the Creation not a CREATOR
    It also prove our Holy Quran that said 1400 ago
    “With power and skill did We ( Allah) construct the Firmament: for it is We (Allah )Who create the vastness of pace.”
    [ 51:47]

    And the Big Bang
    Do not the Unbelievers see that the heavens and the earth were joined together (as one unit of creation), before we clove them asunder? We made from water every living thing. Will they not then believe?
    [21:30]

  12. Justin Damian Furness
    South Africa
    January 24, 2012, 5:25 am

    And what happened to Nassim Haramein and the Swarzchild Proton surely a way bigger discovery as it solves Einstein’s field equations and gives us a “Unified Field Theory” one that actually works! A way more deserving and fundamental discovery to our universe and humanity showing that all protons are entangled

  13. parchuri
    Auckland, New Zealand
    January 23, 2012, 3:24 am

    One of the best article I have ever read. It would be even great if you can explain how this will effect the present world following the laws stated by former scientists.

    Thank you.

  14. MeekLoverOfGod
    Olympia Washington
    December 31, 2011, 3:24 pm

    In reference to the comments about space travel, read my posting under the Space picture on this website Titled Rebel Angel and consider the molecule just discovered that travels faster than the speed of light. It is my strong belief that If these brilliant minds study the inner workings of this particular molecule, I truly believe by inspiration from God that this is the key to getting god’s meek ones to the Also Newly Discovered Livable Planet that resembles the comment by John Leonard on this page. Also, the thoughts of the user by the name of First Last is very interesting to me because it goes right along with exactly what I am commenting myself on. It is also my thought that Global warming will be the demise of this planet ending all life on this planet to time indefinate with the heat of our sun cooking Earth to a barren waste land. Causing the sea to dry up as fortold by Jehovah, the title of god and his son our reigning King, Jesus Chirst. If you would like to see a picture of the image that was fortold in Revelation just simply study the image of Rebel Angel. There is on his right wing the images of the face of a lion and the figure of a man. On his left wing you will find the image of the face of a young bull and all the way to the edge the head like that of an eagle. Last but certainly not least, if you look just below Jesus’s face you will see the sword as fortold as well in the book of life. It was written by his prophets by his command and now I tell you by his command. He is coming with the clouds. Jehovah has revealed these things to me and it is my duty as his slave to tell the world. Start reading the whole bible but to save your life, start in the book of revelation. I have told King 5 news in this region of this information and I hear nothing on the news, so I must assume they do not air the information for fear of what is also fortold beginning. This is not the End, it is only the beginning of everlasting life on our newly found planet in a newly found galaxy perhaps. I will post more information as it is revealed to me.

  15. ali
    LIBYA
    December 29, 2011, 10:27 am

    Thanks for your excellent explanations of this discovery. The theory of accelerating universe agree will with what is mentioned in the quran in the vers(47) from saurat aldharyat :
    “And the heaven We constructed with strength, and indeed, We are [its] expander.” http://quran.com/51

  16. saiher iqbal
    pakisatan
    December 23, 2011, 1:30 pm

    AOA. 1s of all congratulaionz to all scientist whz awarded by noble priz, its a good job , cary on……….

  17. Saiher Iqbal
    Pakistan
    December 22, 2011, 2:44 am

    AOA. 1st of all,congratulations to all scientist, its a good job, carry on, and discovere smthng new more…….lolz

  18. Mohd Rehan
    New delhi, India
    December 15, 2011, 4:06 am

    Albert Einstin would LIKE it

  19. First Last
    December 11, 2011, 4:08 pm

    What we see is not distant in SPACE but distant in TIME. Only thing they can prove is deceleration.

  20. Justine C. Magdadaro
    Digos City, Philippines
    November 23, 2011, 10:59 pm

    Great Job! I hope Albert Einstein would recommend a “LIKE” :D LOL.

  21. john leonard
    tanzania.
    November 21, 2011, 6:18 pm

    guys these things comes each at a time!lets think of these catastrophies when water rain affected planet as bible says of noah and a time when the planet was all joined with no continets divisions,i believe there was great volcanic reactions occoured,but what disturbed our mother planet to that point was there anything introduced to planet,thanks to these scientists exploring our galaxy with approval of expansions,coz till to the freezing globe we think of we will hit globa warming we dont know to what degrees,then will go to under water cities and towns a coz of melting arctic,there will be discovering to coming year where people will discover a living of human to some depth of sea while the human exodus migration proceeds.as we find skeleton of dinors in anbelievable dag sea floors.this will pass to other comming ones.then do this expansion of galaxy affect the planet in any different past covers will it still affect planet to comming layers of covers and covers?some said fire and some say freezing and what after these covers.

  22. Ankita Vashishtha
    Gujarat,India
    November 21, 2011, 9:03 am

    This article is indeed very nice.First of all congratulations to all these scientists for winning Nobel Prize. Moreover it’s first time that astronomers have won the prize. Well as far as newton’s concepts are concerned then we can say that at his time even his ideas were thought provoking! Science is all about exploring the new dimensions of knowledge. Still many new concepts are about to come. For example: particles traveling with speed more than light which can really change even existing norms of physics. So let’s wait for some more thought provoking ideas in the coming future! Good Luck!

  23. Timothy Nichols
    United States of America
    November 18, 2011, 10:07 pm

    Great article, however I am very surprised there is no mention of Dr. Sheldon Cooper. Just joking, very good article and a great explanation of dark energy.

    • rjvanderbei
      November 20, 2011, 9:54 am

      I tried to interview Sheldon for the article but he was busy arguing with Leonard over their roommate’s agreement. Then Penny came in and I knew it was hopeless.

  24. saeed Arabo
    November 16, 2011, 1:45 pm

    Thank you sir for this nice article,but ,frankly speaking,I did’nt like the way you spoke about the Giant scientist …. Newton. Don’t forget he did all what he did 300 years ago.
    300 years ago.And may be Giant Einstein’s theory will face the same in coming 250 years.Development never stops.

  25. Hahaha
    next to you
    November 9, 2011, 8:22 pm

    stop thinking about adam….. ! does not exist.

  26. Gilbert Carmelia
    Nederland
    November 5, 2011, 7:54 am

    I too want to know more.

  27. [...] that I found very interesting. First, The 2011 Nobel Prize in Physics went to three astronomers who discovered the universe is expanding at an accelerated rate. I found this so interesting because the description resembles some of the classic descriptions of [...]

  28. Robert
    CA, USA
    October 21, 2011, 2:20 am

    Having just finished A Brief History of Time, I found this quite interesting, and easy to understand, well written. References to other more detailed writeups would be most welcome!

    I believe Hawkings will be quite surprised. Most expected a big crunch, this discovery will strengthen the case for a designed universe with so many just-right values for cosmological values.

  29. W G Kilgore
    Dallas TX
    October 18, 2011, 3:38 pm

    Very nice article. The best explanation of dark energy and expansion I have read.

    I would like to read discussion on the topic of expansion moving distant objects away from each other at faster then the speed of light?

  30. [...] Nobel Prize in Physics 2011–The Accelerating Universe The 2011 Nobel Prize in Physics has been awarded to Adam Riess, Brian Schmidt, and Saul Perlmutter for their discovery of the accelerating expansion of the universe. It is one of the times when astronomers have won the Nobel Prize in Physics. … Read more on National Geographic [...]

  31. [...] The universe is getting bigger much faster than anybody thought before. Read the story from National Geographic. Share this:TwitterFacebookLike this:LikeBe the first to like this [...]

  32. Ruth P.
    SF Bay Area
    October 16, 2011, 9:09 pm

    On the whole a very well written and articulated article. Thanks — I enjoyed it so much and it has left me hungry for more.

    To Robert Vanderbei – You exercised an incredible amount of restraint in your response to Ms. Brackett above — kudos to you! I would not have been so generous. Thank you for being one of those rational pioneers in science that is helping us to better understand our universe and moving human knowledge out of the narrow confines of Bronze Age thinking.

  33. Karen Sherry Brackett
    United States of America
    October 16, 2011, 4:50 pm

    Given the climate change we are facing today, it might be interesting and useful to take the data points of time and age recorded in the Bible and compare them to geological records we have today and see if the rate of acceleration can be estimated. Genesis records Adam lived to be over eight hundred years old. So, the question comes to mind was that possible because the Earth’s rotation was faster? It would have to take into account as well that the Earth’s surface has not expanded but in fact has decreased. So, there would be several variables to consider. If the Earth were closer to the Sun but the Earth was larger in those days, then a year could have cycled faster even though a day might have been longer. Naturally, one would assume that the Sun would have been larger but perhaps it was smaller and cooler? The Bible records not no man has lived to be older than 1,000 years. So, 999 could be one reference with the average global age of man today being 45 the other end of the pole. Actually, that makes for a surprisingly simple equation and entirely note worthy if one approaches the Bible as historical records rather than “folklore” and “conspicuous” thinking.

    • rjvanderbei
      October 16, 2011, 6:56 pm

      The number of years a person lives could change if the length of a year changes. Hence, Adam living 800 years could be explained if the Earth’s orbit around the Sun took 1/10-th as long then as it does today. This can be easily checked by doing a simulation starting with today’s coordinates and running time backwards. I have made such a computer simulation. If you have Java installed on your computer and enabled in your browser, then you can go to

      http://www.princeton.edu/~rvdb/JAVA/astro/galaxy/SolarSystem.html,

      change dt from 0.0030 to -0.0030 and click “Start”. You will quickly get to a simulated time that is about 6000 years in the past. When you get there, click “Pause”, set “warp” to “1″, and click “play”. You will then be able to check that the Earth orbited the Sun about once every year even back then. Of course, this simulation assumes non-relativistic Newtonian mechanics. If you are suggesting that maybe 6000 years ago, the universe was smaller and hence maybe the orbit could have been faster due to such a “cosmological” effect, let me point out that 6000 years ago was just yesterday on cosmological scales. Six billion years was a long time ago for cosmological effects such as the expansion of the universe to be significant. Six thousand years is only one millionth of that amount of time. Over the last 6000 years, the universe has changed very little from a cosmological standpoint.

      –Robert Vanderbei

  34. Georges Spyrou
    Belgium
    October 15, 2011, 8:36 am

    And hopefully in -say – a 100 years (or even before) we will have another model for the Universe without “Dark energies” , “Big bangs” and all this folklore.

  35. [...] Nobel Prize in Physics 2011–The Accelerating Universe Posted on October 15, 2011 by admin Nobel Prize in Physics 2011–The Accelerating Universe The 2011 Nobel Prize in Physics has been awarded to Adam Riess, Brian Schmidt, and Saul Perlmutter for their discovery of the accelerating expansion of the universe. It is one of the times when astronomers have won the Nobel Prize in Physics. … Read more on National Geographic [...]

  36. Sheikh Jafrul Hassan
    Dhaka, Bangladesh
    October 14, 2011, 11:35 pm

    Definitely this is a conspicuous article.

  37. satish gaikwad
    mumbai,india
    October 14, 2011, 12:54 pm

    superb…. i like this article..

  38. Anirban Chowdhury
    Kolkata(INDIA)
    October 14, 2011, 2:50 am

    The article had a clear picture about the discovery but I am hungry to know more.

  39. Rough Cibernus
    Sirte, Libya
    October 13, 2011, 9:02 pm

    I like the explanation of the article, after this, The books will change once more .. XD

  40. Ofek
    No
    October 13, 2011, 8:00 pm

    CLEAR THAT THE VATICAN IS UPDATING THEIR KNOWLEDGE …. THE HELL IS NOT FIRE, BUT ICE.

  41. iman
    iran
    October 13, 2011, 4:20 pm

    That was fantastic explanation about background science related to new nobel prize.

  42. José Trinidad Torres Reyes
    Ciudad de México
    October 13, 2011, 3:51 pm

    Tremendo articulo, el descubrimiento paulatino de nuestro Universo nos ofrece la esperanza de un mejor futuro y nos anima a seguir estudiando sus maravillas. Gracias por la difusión de estos artículos, que de otra forma, no estarían a nuestro alcance. Felicidades.

  43. Tyler Hernandez
    azusa, CA
    October 13, 2011, 1:03 pm

    Im only 17 and a senior in high school. This article answered many questions i myself never thought to ask. Beautifully written.

  44. swathi
    kakinada
    October 13, 2011, 8:25 am

    really the article had a clear picture about the discovery.

  45. Abhinav Aggarwal
    chennai,india
    October 13, 2011, 1:14 am

    much more than I know about it. completed from all aspects

  46. Emma Kigar
    Ridgway, Colorado
    October 12, 2011, 6:43 pm

    Fantastic and clear article on a fascinating discovery.