# WMAP year 7: We Know What We’re Doing!

The New Age? It’s just the old age stuck in a microwave oven for fifteen seconds. -James Randi

About two weeks ago, the WMAP (Wilkinson Microwave Anisotropy Probe) team released their seven-year results, and I’m finally ready to tell you all about it. WMAP, remember, is this guy.

By looking at two different points in the sky simultaneously, and looking at the proper frequencies of microwave light (it looks at five different frequencies every time it looks at the sky), it can measure the differences in the intensity of light left over from the big bang everywhere in the sky. Why is this so important? Because the Universe is so uniform, and it was even moreso in the past. When we look back at the leftover glow from the Big Bang, this is what we see. (This is the entire sky shown in a Mollweide projection.)

That’s right; we find that the Universe is 2.725 Kelvin in temperature everywhere. There’s about a 0.003 Kelvin difference in the hottest part of the sky as compared with the coldest part of the sky, and that’s it. But these differences can tell us something. So if we subtract out the 2.725 Kelvin average, we’re left with temperature differences. What does that look like?

One part of the sky looks slightly hotter than average, and another part looks slightly colder than average. This is really, really interesting, because the hot part is exactly 180 degrees in the opposite direction from the cold part! This would be exactly what we would see if we were in motion!

What if we subtracted that motion out? Well, for the first time in the high resolution, that’s what WMAP allowed us to see. What do these tiny temperature fluctuations look like?

There are spots that are a few hundred-thousandths of a degree warmer (yellow and red), and there are spots that are a few hundred-thousandths cooler (green and blue). These correspond to regions where there’s slight less matter and energy (red) and slightly more matter and energy (blue). Why are the denser spots colder? Because your light loses energy when it has to climb out of a gravitational field, making it cooler.

So we’ve got this incredibly detailed, intricate map of hot and cold spots in the Universe, which tells us how the matter and energy was distributed when the Universe was only 380,000 years old! (This is, by far, the earliest picture of the Universe we’ve ever taken.) There were no stars, no galaxies, and it’s only at this time that we are forming neutral atoms for the first time. So what can we possibly learn from this picture after 7 years? Practically everything, including:

1. The composition of the Universe: about 4.5% normal matter, 22% dark matter, and 73.5% dark energy.
2. They strongly announce that there is no evidence for any deviation from this model.
3. The age of the Universe: about 13.7 billion years.
4. The curvature of the Universe: if there is any, it is less than 1% on the scale of our Universe. (This is like walking outside, looking at 100 miles of land around you, and concluding that the Earth is at least 10,000 miles in size if it’s curved.)
5. Dark energy behaves like a cosmological constant. This new measurement tells us that if dark energy deviates from a cosmological constant, it does so by less than 14%, the most stringent constraint ever!
6. For the first time ever, they have directly detected helium atoms formed before the first stars, confirming Big Bang Nucleosynthesis in a brand new way!
7. And finally, simulations of the simplest cosmological models line up almost exactly with what WMAP observes!

There are other mission results that you can find here, but the big conclusion that you can draw from this is that all of the standard cosmology, including dark energy, dark matter, inflation, a flat Universe, and a hot big bang, are confirmed.

This could mean that there will be no new surprises, and that the only major challenges left for the largest endeavors in cosmology are to figure out what dark matter, dark energy, and inflation actually are! (Although, each of those are Nobel-worthy puzzles.) The one thing people were worried about? These big features that appear to be in the Cosmic Microwave Background?

(Affectionately referred to as “Fingers of God” by some, a name that is also used to refer to something else in cosmology.) They show up in simulations often enough that we shouldn’t be worried that our Universe has them, according to the latest results. Just apply inflation to starts off a hot big bang, and what you should get lines up perfectly consistent with what we see. So get out there and enjoy your Universe!

1. #1 Alex Besogonov
February 10, 2010

8) Don’t forget the most important feature: signature of Stephen Hawking!

2. #2 NewEnglandBob
February 10, 2010

Wow, three more puzzles to figure out then physics closes up shop! Haven’t physicists learned ANYTHING from public employees about job longevity? 😉

(Thanks Ethan, educational and enjoyable, as usual)

3. #3 Siamang
February 10, 2010

I wish scientists would learn to stop naming things after aspects of religions.

The simple folks get confused. “I heard that even science accepts a might-of-Condrial Eve!”

People still think that the big bang happened in Genesis 1:3 because of some old tv show where the announcer said “Let there be light” right before an animation of the big bang.

It harms science education, I think, to tie scientific concepts to religious ones.

4. #4 Paulino
February 10, 2010

So Stephen Hawkins IS god! And he even signed his work…

5. #5 fpilot
February 10, 2010

Something that has always puzzled me is how do they take into account the heat/temperature of the stars and galaxies in working out the temperature of the background radiation?

6. #6 Wayne Robinson
February 10, 2010

Does John Moffat’s Modified Gravity theory also explain the latest findings? http://en.wikipedia.org/wiki/MOdified_Gravity
So far, it agrees with observations, without the need for dark matter.

7. #7 Ethan Siegel
February 10, 2010

Wayne,

MOG’s biggest obstacle is collisions of galaxy clusters, like the Bullet Cluster, which it cannot explain at all.

Dark matter successfully explains phenomena like that, so to say that Moffat’s Modified Gravity “agrees with observations, without the need for dark matter” is not really true.

February 10, 2010

Amazing – so we routinely cool things to a temperature below what would be obtained by putting an object deep in space.

9. #9 Chuck
February 10, 2010

Looking at the second temperature plot (the one which looks a bit like the ying-yang symbol). If this comes about from our motion, then does the microwave background define a universal inertial frame of reference?

10. #10 DB
February 10, 2010

Isn’t the surprising lack of antimatter also requiring an explanation, or is it just assumed that we’re in a pocket of regular matter that’s the result of random variation in a much larger Universe than our observable one?

11. #11 Ethan Siegel
February 10, 2010

DB,

That is actually a standard part of cosmology, known as baryogenesis. It will be part 5 of my “The Greatest Story Ever Told” series.

Chuck,

It isn’t Universal (because it depends on your location), but you can always pick a frame of reference at any location where the “yin-yang” patter is removed from the CMB. The reason it isn’t Universal is because if I stand at Andromeda and pick a frame where that pattern is removed and you stand at the Milky Way and choose a frame where that pattern is removed, we will still be moving away from each other. That’s Hubble’s Law.

Yup.

12. #12 Anonymous
February 10, 2010

So the universe is just a big Yin-Yang. That’ll make some people happy.

13. #13 DB
February 10, 2010

Awesome, looking forward to it Ethan.

14. #14 Sphere Coupler
February 10, 2010

Nice…Very nice,Great Science!Great post!

Look forward to more WMAP updates…in time.

So get out there and enjoy your Universe!

*now where did I put my ship?*

February 11, 2010

Ethan, I am very confused about the geometry of the universe – maybe you or someone else can help explain.

What are we looking at in the WMAP picture with the Fingers Of god? How can we make sense of a 2D picture of CMB if the universe is expanding in 3 spatial dimensions and EM waves are approaching us from everywhere? Shouldn’t they have to look at a “picture” that is shaped similar to the inside of a spherical shell?

Furthermore, how is the universe “flat?” I understand how the SURFACE of the earth appears flat locally, and I also understand that surface of earth is actually a 3-manifold of omega > 1. However, I can not grasp the concept of “flatness” for space. I am having trouble visualizing the universe as a surface. Maybe I’m getting a little out of my league here with advanced topology topics, but I have always imagined the universe as a typical R^3 Euclidean space with distortions appearing in the areas around galaxies and galaxy clusters containing lots of matter.

I tried to fill you in with some of my thoughts so you could possibly correct my misconceptions, but if I confused you much just read this:
1) How can a 3D space be flat?
2) How does the WMAP data, when viewed as a 2D ellipse, help us learn about our 3D universe?

16. #16 Chuck
February 11, 2010

Chuck,

It isn’t Universal (because it depends on your location), but you can always pick a frame of reference at any location where the “yin-yang” patter is removed from the CMB. The reason it isn’t Universal is because if I stand at Andromeda and pick a frame where that pattern is removed and you stand at the Milky Way and choose a frame where that pattern is removed, we will still be moving away from each other. That’s Hubble’s Law.

Thanks for the explanation. Now I’m puzzled about something else. Why is it a “yin-yang” shape? The two colors are blueshift and redshift arising from our motion, right? But why isn’t the boundary between them a straight line, instead of an s-shape? Is there a simple way to understand this?

Cheers.

17. #17 Wayne Robinson
February 11, 2010

“MOG’s biggest obstacle is collisions of galaxy clusters, like the Bullet Cluster, which it cannot explain at all. Dark matter successfully explains phenomena like that, so to say that Moffat’s Modified Gravity “agrees with observations, without the need for dark matter” is not really true”.

John Moffat claims that MOG does explain the Bullet Cluster. He also says that MOG explains Abell 520, whereas standard theory with dark matter doesn’t. The Bullet Cluster just disproves MOND.

What is your response? Until we actually find dark matter, using theories of gravity (which are still not definite) to prove its existence seems futile.

18. #18 JayVee
February 11, 2010

Chuck,

I think the S shape is an artifact of the projection. If you wrap this picture around a sphere, the S would curve nicely around it in a straight line (like the equator on earth).

19. #19 TBRP
February 11, 2010

Wayne, if you want Ethan’s response, try his third post on dark matter. He doesn’t discuss Abell 520, but does show good reason to be skeptical of MOG wrt the Bullet Cluster.

20. #20 TBRP
February 11, 2010

Oh, it looks like Abell 520 is discussed here.

21. #21 Bjoern
February 11, 2010

How can we make sense of a 2D picture of CMB if the universe is expanding in 3 spatial dimensions and EM waves are approaching us from everywhere? Shouldn’t they have to look at a “picture” that is shaped similar to the inside of a spherical shell?

The original picture *is* indeed a spherical shell – but in the projection used here, it looks like an ellipse. The WMAP team also had compiled maps which show the true spherical shape some years ago; unfortunately, I seem not to be able to find them again… 🙁

Furthermore, how is the universe “flat?” … I have always imagined the universe as a typical R^3 Euclidean space …

Well, that’s exactly what “the universe is spatially flat” means! 🙂

22. #22 Bjoern
February 11, 2010

@dhomstad: I found it again! Look here:
Strangely, I can’t find any such images on the web site of the WMAP team itself…

23. #23 Lloyd Hargrove
February 11, 2010

The gif on Einstein’s Gravitional Redshift is another “keeper”, thanks! Do people tend to believe that the net results of that particular effect works uniformly as to all points being observed? Some well entrenched assumptions/”laws” appear to assume this is the case and while that provides us with a massive integration, a “flattening out” factor which proves convenient to various existing theories moreso than that which the chaotic nature of the latest evidence might support, it may also continue to represent a huge stumbling block.

24. #24 Diablo
February 11, 2010

Um…I got some questions about black holes and if they are stupid, I apologize.

I understand that as a star ages, more and more lighter elements are converted into iron. Eventually it collapses or whatever on itself, and if there is enough mass, it creates a black hole right? So if a black hole continues to collect more and more matter, will it convert the iron in it initially contained and other elements it sucks up into even more and more heavier elements? Is this how Uranium formed? I’ve always been confused by where exactly Uranium and Radon come from. (You would think I would know this since I worked at a Naval Nuclear facility). Are black holes really hot? They are like stars except the energy and matter cannot escape or is that a gross misunderstanding?

I guess my main question is, should there be completely new, undiscovered elements inside of a black hole?

Also, and I am sure I am seriously messing things together in a rather retarded (oops sorry Mrs Palin) fashion, but could you look at the state of being right before the big bang as a massive black hole except it also contains all of our reality and physical laws?

Thanks to anyone trying to fill in my clueless ass and I apologize for bringing this up when it doesn’t pertain to the topic at hand.

February 11, 2010

@Bjoern: that is EXACTLY what I wanted to see. Thank you so much for posting that link.

I have another question regarding the flatness of the universe. If we look around and see that omega = 1 (although, from some of the graphs that Ethan has posted, I’m not exactly positive that the omega = 1 line fits all the data inconclusively), wouldn’t it be an EXTRAPOLATION to say the entire universe is flat?

To draw an analogy, my linear algebra professor mentioned many times that making a prediction within the boundary conditions of your function is an “interpolation” – a relatively safe conclusion – and making a prediction outside of your boundary conditions classifies as a extrapolation – not a safe conclusion. Couldn’t the universe be very distorted or even contain discontinuities outside of our visible portion?

26. #26 Morgan
February 12, 2010

I understand that as a star ages, more and more lighter elements are converted into iron. Eventually it collapses or whatever on itself, and if there is enough mass, it creates a black hole right? So if a black hole continues to collect more and more matter, will it convert the iron in it initially contained and other elements it sucks up into even more and more heavier elements? Is this how Uranium formed? I’ve always been confused by where exactly Uranium and Radon come from.

When a star starts producing iron as its fusion product, its fusion is reaching a dead end, because you can’t produce energy by fusing iron – it takes more energy than it releases. This means it doesn’t have the outward pressure of the fusion to balance its own mass, which is why it collapses.

All the elements heavier than iron are produced in supernovae, where the explosion of the outer layers of the star pumps enough energy in to them to fuse iron and beyond.

As to what happens inside a black hole – I think you’d see degeneration rather than fusion (in to neutronium etc., until what you’ve got can’t even be usefully thought of as atomic matter any more), but well, it’s in a black hole by that point, so it doesn’t make much difference…

27. #27 Bjoern
February 12, 2010

I have another question regarding the flatness of the universe. If we look around and see that omega = 1 (although, from some of the graphs that Ethan has posted, I’m not exactly positive that the omega = 1 line fits all the data inconclusively), wouldn’t it be an EXTRAPOLATION to say the entire universe is flat?

First, we can’t say that Omega = 1 exactly, and won’t ever be able to say that – because we’ll always have a measurement error. If Omega is e.g. 1.01, we could some day perhaps measure Omega = 1.01 plus or minus 0.001, and then we could be sure that the universe is closed and not flat. Same argument if Omega is e.g. 0.99 – then we could one day be quite sure that the universe is open. But if Omega is exactly 1, we could measure e. g. Omega = 1.00 plus or minus 0.001 and still not be sure if the universe is closed, flat or open!

Second, this is indeed an extrapolation – but that extrapolation is based on the basis of all cosmology, the cosmological principle. That principle says essentially that the universe is the same everywhere, hence if we measure Omega = 1 in our “vicinity”, we conclude (or more accurately, assume) that Omega = 1 everywhere. This is obviously the most simple assumption – but AFAIK, there are also several models in which the cosmological principle isn’t actually used, and the universe “far away” can be very different from our “vicinity”. (e. g. eternal inflation, IIRC)

28. #28 Eugene S
February 12, 2010

OK, here’s my pet peeve about the use of color to denote temperature.

In the “yin yang” picture and in the WMAP image right below it, “hotter” is painted yellow/orange/red and “cooler” is painted green/blue.

This is in line with the public’s idea of temperature vs. color. A hotplate left on too long glows red. The ocean (“cool water”) is blue. A glacier (cold) is blueish white. Incandescent light bulbs are warm to the touch and emit a yellowish-orangeish light, whereas (efficient) fluorescent lights are cool to the touch and emit a white-ish-blue-ish light.

However, the picture of “Einstein’s gravitational redshift” correctly shows the longer-wavelength light (which is “cooler”, because less energetic) as red, and shorter wave-length (“hotter”, because more energetic) blue.

Same for stars: ignoring shifted wavelengths due to relative motion, the hottest stars emit more short-wavelength light (blue-ish) and the coldest stars are red (giants like Beteigeuze).

This can be confusing to some. Sorry for being such a pedant but I believe it would be more educational to be consistent and start using blue for “hot” and red for “cold”.

29. #29 Gary
February 14, 2010

Very interesting, just been watching a show on Infinity and it makes me think about a few things.

Are we measuring the age of the universe based on the red-shift in light that we can observe ? what I don’t understand is based on inflation, wouldn’t that light already have passed us a long time before we were ever created ?

If the universe was created at big bang (x) and the earth created at point y, the “time” between point X and y being say 10 billion years, then the light from point x would have already escaped beyond earth into point x+ ?

Also, another puzzling thing, if the universe is “infinite” why is the sky not infinitely bright at night, there are infinite stars stretched out over billions of years shining their light – some of that light will take a billion years to reach us, some only a million – but at some point both amounts of light will reach us at the same time..
I read about cosmic dust interfering in the light, but surely if we could measure the “non-visible” light at night then we should see an infinitely bright sky (albeit it at non visible wavelengths?)

30. #30 Bjoern
February 15, 2010

@Gary: The error you are making is simple: the Big Bang didn’t happen “at point x”. The Big Bang was not an explosion in space, it was the birth of space itself; it happened, in a sense, at every point at once. Do you know the usual balloon analogy?

And the sky is not infinitely bright (1) because the light of most stars didn’t have enough time to reach us so far, as you yourself already argue, and (2) due to the expansion of the universe, the light gets more and more redshifted, until you can’t see it anymore.

31. #31 Thomas Neil Neubert
February 17, 2010

“the only major challenges left for the largest endeavors in cosmology are to figure out what dark matter, dark energy, and inflation actually are!”

Another way of saying that is that the three extraordinary assumptions (some would say “solutions”) of dark matter, dark energy and inflation (i.e.? a new 5th force of nature) are necessary to continue propping up the various big bang theories.

And how can we believe in the big bang theory if essential assumptions are seriously problematic. e.g. if dark energy is the cosmological constant (“dark energy deviates from a cosmological constant, it does so by less than 14%”); then we must remember how difficult a problem it is. Wiki say “This is the cosmological constant problem, the worst problem of fine-tuning in physics: there is no known natural way to derive the tiny cosmological constant used in cosmology from particle physics.”

But personally, I think that baryogenesis is the biggest remaining problem for the big bang theories. as Wiki says, “While particle physics suggests asymmetries under which these conditions are met, these asymmetries are too small empirically to account for the observed baryon-antibaryon asymmetry of the universe.” And if we can’t get rid of the hypothetical antimatter in the early universe of Ethan’s hypothetical big bang (which occurred after inflation); then there is no plausible big bang theory.

Well enough of my skepticism. And despite my continued skepticism of the various big bang theories, kudoos to the excellent scientist of WMAP for their excellent work! Seriously, kudoos!

One small question to highlight my ignornace; what exactly is the motion that is being eliminated from the ying yang diagram? Thank you.

32. #32 Bjoern
February 17, 2010

@Thomas:

Another way of saying that is that the three extraordinary assumptions (some would say “solutions”) of dark matter, dark energy and inflation (i.e.? a new 5th force of nature) are necessary to continue propping up the various big bang theories.

One could argue that inflation is an extraordinary assumption (note that there are still respected cosmologists like Steinhardt who work on alternative explanations), and perhaps even dark energy (although the existence of that is quite natural, IMO) – but why on Earth do you call dark matter an extraordinary assumption? What’s so extraordinary about the “assumption” that there could be non-baryonic matter out there – especially in light of the fact that essentially all extensions of the Standard Model of Particle Physics also predict that?

“This is the cosmological constant problem, the worst problem of fine-tuning in physics: there is no known natural way to derive the tiny cosmological constant used in cosmology from particle physics.”

There are many other fine-tuning problems in physics, why do you pick this one? If this is the “worst problem” is very debatable, I’d disagree with that assessment. E. g. it is quite clear both to cosmologists and particle physicist that obviously, we can’t derive the value of the constant as long as we don’t have a working quantum theory of gravity. When we have that theory and still the value comes out wrong, *then* you’ll have a point.

And if we can’t get rid of the hypothetical antimatter in the early universe of Ethan’s hypothetical big bang (which occurred after inflation); then there is no plausible big bang theory.

I’d say that’s more a problem of particle physics, not of the Big Bang theory. But let’s wait what Ethan has to say about this in the next installment of his series, o.k.?

One small question to highlight my ignornace; what exactly is the motion that is being eliminated from the ying yang diagram?

That’s the motion of the WMAP satellite relative to a coordinate system which would be co-moving with the cosmic expansion; you can think of it as the center-of-mass system of the stuff which emitted the CMBR (although that doesn’t really work well in an expanding universe). In the balloon analogy: one can rest with respect to the surface of the balloon, or one can move with respect to it; and the “yin-yang” showed that we move with respect to it.

Oh, BTW: the age of the universe (13.7 billion years) is the age as measured in such a co-moving coordinate system; that should help clearing up the “problem” you present in the second chapter of your book.

33. #33 Morgan
February 17, 2010

I was under the impression that, even if one thought the current consensus model in cosmology was incorrect in this or that respect (no inflation, no dark energy, etc.), you were still dealing with a “Big Bang” model so long as you say that, yes, galactic red shift says that, yeah, the universe used to be much, much smaller and much, much hotter.

I’m curious as to whether Thomas’ skepticism is of the form:
– I disagree with the notion of inflation, dark energy etc., but agree that the universe used to be small and hot;
– I disagree that the universe used to be small and hot enough to justify calling it a Big Bang at all; or
– I disagree that the universe used to be small and hot enough to justify calling it a Big Bang, and here’s what I think explains galactic red shift instead.

34. #34 Bjoern
February 17, 2010

@morgan: Judging from what he wrote elsewhere (we have also exchanged several e-mails already), he suggests a steady-state model… but has no actual explanation how that is supposed to work. *sigh*

35. #35 Thomas Neil Neubert
February 19, 2010

Regarding point 4 above, the “curvature of the Universe: if there is any, it is less than 1%”

Oct 8, 2003 physics world dot com says:
…..”Data from the first year of the WMAP satellite – unveiled in February – agreed with the predictions of the standard big bang plus inflation model of cosmology for regions of space separated by small angles. However, on larger angular scales – greater than 60° – the WMAP observations were significantly lower than this model predicted.
…..”Jean-Pierre Luminet of the Observatoire de Paris and colleagues believe that the finite size of the universe itself is responsible for this behaviour. Moreover, they show that the predictions of a model in which space consists of 12 curved pentagons joined together in a sphere agrees with the WMAP observations. Their ‘small’, closed universe should be about 30 billion light years across.”

As well, Wikipedia currently states,
…..”A positively curved universe is described by spherical geometry, and can be thought of as a three-dimensional hypersphere, or some other spherical 3-manifold (such as the Poincaré dodecahedral space), all of which are quotients of the 3-sphere… Based on analyses of the WMAP data, cosmologists during 2004–2006 focused on the Poincaré dodecahedral space (PDS), but horn topologies (which are hyperbolic) were also deemed compatible with the data.”
By the way the Poincare dodecahedral space is the name for a soccer ball approximation to a 3-sphere spherical universe.

So unless the WMAP data in year 7 (2009) is seriously different than it was in year 1 -4 (2003-2006), it appears that the WMAP data does not rule out a spherical universe of “about 30 billion light years across.”

36. #36 Thomas Neil Neubert
February 19, 2010

Bjoern
As always, I thank you for your excellent clarifications and explanations.

Regarding dark matter as an extraordinary assumption. I refer you to Fred I. Cooperstock’s book General Relativistic Dynamics (Extending Einstein’s Legacy throughout the Universe), 2009, pg 154-156 ,
….”We have shown that general relativity could accomodate typical galactic rotation curves with relatively small amounts of dark matter and hence not of the exotic variety that the description “dark matter” generally connotes… While Newtonian gravity demands the extra matter from the limited data, general relativity declares that this data is insuffiecient to determine the full extent of the matter… After all, if nature should present us with systems of mass distributions as presently generally believed to exist, general relativity as the premier theory of gravity should be brought to bear as the best indicator of such distribution…. Working against the presence of dark matter, however, is the dark matter theory of galaxy formation. The theory predicts that 10 to 100 times the number of small galaxies than that which are observed are permitted… What this indicates to us is that the state of the dark matter theory is extremely fragile.”
….Fred I. Cooperstock is a general relativity emeritus professor at the University of Victoria, Canada. He has written an excellent book that I believe is important for every professional physicist and astronomer to read and yet one that is largely readable to the persistant and curious layman.

The quote on the fine tuning problem of the cosmological constant that you object to is not mine; it is a peer reviewed quote from Wikipedia. Argue with wikipedia to change their view if you believe that it is not accurate.

37. #37 Thomas Neil Neubert
February 19, 2010

Morgan

In my view the big bang model is the best cosmological explanation that brings together all of the physical data and observations. And Ethan’s explanation is as good as any of the varieties of the big bang model.

And yes as Bjoern suggests, I prefer some type of steady state model (even a steady state with aspects of the big bang).

In my view a responsible scientific statement about the universe is still Steven Weinberg’s, 1992, “The original version of the steady-state cosmology has been pretty much ruled out by various astronomical observations… It is possible that the steady-state idea may be revived on a grander scale… Quantum cosmology is right now a matter of active controvery among theorists; the conceptual and mathematical problems are very difficult, and we do not seem to be moving toward any definite conclusion.”

My big problem with the big bang model is the hubris with which it is usually presented. In my view, the big bang model has so many problems and extraordinary assumptions; that it should always be described as hypothetical or tentative or apparent; but not as a fait accompli.

Furthermore, consider Ethan’s rather ordinary big bang statement, “That’s right, the Big Bang is a time back when the Universe was squished into a region that made it about 10^70 times denser than you are right now. Or rather, the most conservative estimate of the Big Bang involves that. If you want to go to the other extreme, the most fantastic estimate is that all of that matter and energy is concentrated into a volume the size of a single proton.”

I consider Ethan’s unqualified statement as scientificly irresponsible. In my mind, it is unqualified statements like this that make science a laughingstock in important places (e.g. for funding as in Congress). If you don’t care about funding the next generation of big science then continue defending scientific statements about fitting the universe “into a volume the size of (a thumbnail or) a single proton.” In my mind physicists and astronomers will have a lot more credibility (but less halo) if like biologists they say “we really don’t know.” Science whether physics (e.g. cold fusion)or economics (e.g. the perfect economy)looks very foolish when they have been certain they knew.

Big physics and astronomy Hubble, SSC, WMAP, LIGO cost big money; hubris doesn’t help either big science or small science. When Congress didn’t fund the SSC; I don’t think small science benefited either.

38. #38 Bjoern
February 19, 2010

@Thomas: With respect to the dodecahedral space, see “A twelve-sided Universe? – Probably not.” at
http://www.astro.ucla.edu/~wright/old_new_cosmo.html

I don’t know much about Cooperstock, but IIRC, he is a lone voice, and other cosmologists don’t agree with his conclusions. Ethan – if you read this, could you help out with your knowledge?

Weinberg’s statement is a bit outdated; there have been revival attempts of the steady state model, but even the most ardent adherents of that model (Hoyle, Burbidge, Narlikar) admitted that only a “quasi-steady state model” is compatible with the data, i. e. a model which has periodic oscillations of the size of the universe. But even that model failed; for more, see here:
http://www.astro.ucla.edu/~wright/stdystat.htm#QSSC

My big problem with the big bang model is the hubris with which it is usually presented. In my view, the big bang model has so many problems and extraordinary assumptions; that it should always be described as hypothetical or tentative or apparent; but not as a fait accompli.

I agree partly with you. I think that the very earliest stages, especially inflation, should not be presented as fact, since there are still respected cosmologists out there (like Steinhardt) who have alternative proposals which have not yet been ruled out. But in contrast to you, I think that the later stages (approximately since the electroweak symmetry breaking) are very well established and *can* be presented as fact.

In my mind, it is unqualified statements like this that make science a laughingstock in important places (e.g. for funding as in Congress).

Do you have any evidence that Congress is really laughing about cosmology?

In my mind physicists and astronomers will have a lot more credibility (but less halo) if like biologists they say “we really don’t know.”

But biologists also make very confident statements about a lot of things in the past.

Science whether physics (e.g. cold fusion)… looks very foolish when they have been certain they knew.

Err, when have physicists ever been certain that they knew about cold fusion?

39. #39 Douglas Watts
February 20, 2010

For anyone to answer:

Does the inflationary model allow or disallow the existence of an “edge” to the inflation, in the sense that there is, or is not, some place in the Universe where a WMAP would show some sense of direction?

Thanks.

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