Jeffrey Bennett is an astronomer at Colorado who is a freind of mine. He sends out infrequent emails about astronomy, and sent this one last week. I think folks here will like it. Note that he sent a followup a few days later as well:

Dear Friends,

You'll probably be seeing it in the news tomorrow, but today was a major
milestone in the history of astronomy. Thanks to just-released results
from a satellite called MAP (Microwave Anisotropy Probe), it appears that
we now know the age of the universe and several other fundamental
properties of the cosmos. Since I know you are all dying of curiosity,
let's start with some of the apparent answers:

* age of the universe: 13.7 billion years, with an uncertainty of 0.2 billion years.
* composition of the universe:

* 4.4% ordinary matter consisting of atoms (more
technically, this is the baryon content)

* 23% non-ordinary matter consisting of
as-yet-undiscovered particles that we refer to
generically as "dark matter" (more technically,
this is the density of nonbaryonic cold dark
matter)

* all the rest: the mysterious "dark energy" that
is apparently causing the expansion of the
universe to accelerate with time.

* In science, we can never be 100% sure of anything. However, the new
results dramatically raise our confidence in two key theories: (1)
that there really was a Big Bang; and (2) that it really did have an
epoch of inflation when the universe was a mere billion trillion
trillionth of a second (10^-33 second) old. Confidence in these ideas
was already high - probably at the 90-95% level - but now we can
probably place them at the 99.9% level...

How can we claim to know these things? MAP has been meticulously mapping
the cosmic microwave background - radiation that represents the remnant
heat of the Big Bang. The existence of this radiation, discovered in the
early 1960s, was the first solid observational confirmation of the Big
Bang theory, since the theory correctly predicts the radiation's
existence and basic characteristics. No competing theory has been able to
explain this radiation. The theory also predicts that fundamental
characteristics of the universe should have been imprinted on this
radiation in a way that should still be observable today. It is this
imprint that MAP has observed, and its precise signature tells us the
fundamental properties listed above. The details of how the radiation
tells us these things are a bit complex, and I won't try to go into them
now. NASA science news has a bit about it in their article at
http://science.nasa.gov/headlines/y2...htm?list146819. I
should be able to send you a more in-depth description soon: two of my
co-authors of The Cosmic Perspective, Mark Voit and Megan Donahue, are
already at work writing it up for the next edition of this textbook
(coming out this summer). I will try to remember to send this description
out to you once it is completed. Meanwhile, for further background
reading about the issues involved, I'll point you to Mysteries #4 and #3
in my book for the general public, On the Cosmic Horizon. (For more info
on these books, see my web page http://www.jeffreybennett.com.)

How significant are these new results? Of course, it depends on your
perspective. Scientifically, they pin down numbers that we had been
honing in on for decades. Philosophically, they represent an incredible
triumph for the painstaking methods of science, answering basic questions
about the nature of the universe. But my favorite perspective so far
comes from my co-author Megan Donahue, who upon seeing them said:
"MINDBOGGLING. It's the kind of list I would have wanted St. Peter
to hand to me, y'know? But now I get it early..."

Following on the heels of the Columbia tragedy, it is nice to have
something that reminds us that the human race is capable of discovering
truly incredible things.

Best,

Jeff

*****

A few follow-up comments on my e-mail of yesterday about answers to
fundamental questions...

1. If you want to read more: Perhaps the best source is the MAP project
web site: http://map.gsfc.nasa.gov/
There's also a nice article in the New York Times today, which you can
see at http://www.nytimes.com/2003/02/12/science/12COSM.html. (One
quibble I have with the NYT article: it makes it sound like scientists
have two ideas about the nature of the dark energy, one of which goes by
the name "cosmological constant" and the other of which goes by the name
"quintessence." These terms should not be taken to indicate that anyone
has any real clue as to nature of the dark energy - it remains a major
mystery. The new data offer strong support to the idea that dark energy
really does exist, but do not tell us what it is or how it works.)



2. In my list of the key new answers, I neglected to mention that the
evidence also supports the idea of a "flat" universe over a geometrically
curved universe. If you've never heard about alternate geometries for the
universe, they won't make much sense here (you'll have to read Mystery #4
of On the Cosmic Horizon, or something similar). The important point is
that the idea of inflation (a dramatic expansion occurring when the
universe was a fraction of a second old) predicts a flat universe, so
this discovery lends support to that idea.

3. A few of you responded to ask about my "levels of confidence" in the
Big Bang and inflation. I should have been a little more clear about what
I meant, and should have distinguished between the Big Bang and
inflation, because the former is much more strongly supported than the
latter. By a level of confidence, I meant my own personal view of how
likely it is that an idea will stand the test of time rather than
eventually being discarded. Let's start with the Big Bang.
We already had two key lines of evidence supporting the theory
that the universe began in what we call the Big Bang. (It really
shouldn't be thought of as an explosion, but that's another story...)
Line 1 is the existence and spectrum of the cosmic microwave background
(the radiation studied by MAP), which matches what the Big Bang theory
predicts. Line 2 is the observed chemical composition of the universe
(not to be confused with the compositional breakdown of ordinary matter
vs. dark matter vs. dark energy), which also matches the prediction of
the Big Bang theory. The new data give us much more precise information
about Line 1 of evidence, and the match with theory is excellent. Any
theory that might someday replace the Big Bang theory would also have to
be consistent with these same two lines of evidence to the same (or better) level of precision. Thus, while we can't rule out the possibility
that we'll someday favor a different theory over the Big Bang, it seems
rather unlikely to me. Yesterday, I put my confidence in the Big Bang at
99.9%, but I'll back off a bit and call it 99%. In other words, I think
there's about a 1 in 100 chance that we'll someday conclude that there
was no Big Bang, and a 99 in 100 chance that the idea of a Big Bang will
stand the test of time. Remember, this is my personal opinion today, not
the result of any calculations or even of polls of other astronomers
(though I suspect the poll results would be close to this).
Now let's turn to inflation. The idea of inflation explains a lot
of observed characteristics of the universe quite nicely, which is why it
is popular among astronomers. However, until now, it did not have any
really solid evidence to back it up. The fact that the universe appears
to be "flat," as inflation predicts it should be, gives the idea some
observational support. But until we have much more definitive tests of
this idea, I'd personally give it about a 1 in 10 chance that we'll
someday have an alternative explanation for the characteristics of the
cosmos that inflation seems to explain so nicely. Thus, my level of
confidence in inflation is about 90%. Again, remember that this is
personal opinion, not objective data.

4. A couple people also asked what it means when the MAP scientists claim
that the age of the universe is 13.7 billion years, with an "uncertainty
of 0.2 billion years." Here's the basic idea (the specifics may differ
slightly, as I have not studied the MAP experiments in detail):
If we take the MAP results at face value, they tell us that the
universe is 13.7 billion years old. However, any set of observations or
experiments always has some built-in randomness or "noise." By studying their data carefully, the MAP scientists can estimate how such randomness
might have affected their conclusion. They can then calculate the
probability that their result lies within various ranges of the true age
of the universe. The stated uncertainty of 0.2 billion years means that,
according to their calculations, there is a 95% chance that their value
of 13.7 billion years lies within 0.2 billion years of the true age of
the universe. Of course, this means there is still a 5% chance that their
age estimate is farther off the mark. In addition, all of this assumes
that the result is affected only by randomness and not by any fundamental
flaws in the experimental design or in the assumptions that underlie it.
For example, if a different theory someday replaces the Big Bang, then
the entire meaning of the data might have to be reevaluated.

The bottom line of all this is that science is an ongoing process. That
is what makes it so exciting and so fun. We may never be certain that any
of our science is revealing absolute truth, but it gives us a way for all
of us to work together to explore the universe, and to see where the
evidence may take us. It's a great journey in which everyone can
participate and enjoy the fruits of discovery - and it should not
conflict with anyone's personal beliefs about why the universe exists or
who or what created it.

**********

__________________
Phil Plait
The Bad Astronomer
http://www.badastronomy.com
badastro@badastronomy.com

The results look really good when comparing them to COBE. But there are a few things I don't understand.

An animation shows how they used a cooler area to identify a cluster of newly forming stars and determined that these formed 200 million years after the Big Bang. How can they use the data to determine that?

The idea of discovering that the universe is at critical density is pretty darn cool, but how did they work that out?

__________________
Freedom For Fission A breath of fresh Iodine-131

There's a misconception here. The WMAP team did NOT determine the universe to be flat. They ASSUMED it was flat. From this assumption, the values of the Hubble constant, omega, lambda, and the age of the universe followed. If you don't assume a flat universe, the WMAP data barely constrain most of these quantities.

The reionization epoch can be determined using mostly low angular polarization data. The detailed physics is actually rather drawn-out, but basically it relies on the fact that there is some probability that radiation will be rescattered off these newly ionized regions in different ways than in the unionized regions. The anisotropy of the two sides of reionization (known as the optical depth of reionization) is a parameter value in most fitted models for polarization. As the WMAP results proport to give new and better constraints on polarization, we therefore have better constraints on the epoch of reionization.

Also, it isn't quite right to say that flatnesses was assumed. We can actually get at flatness independently using one other cosmological measure. This could be either in the form of a correlation function from redshift surveys, from mass measurements from lensing, or any number of other "parameter degeneracy breaking" measurements that can be made. Once this is done, the Omega_total (the overall "flatness" parameter) is measured to be 1.02 +/- 0.02 or nearly flat. Since it is shown to be so close to flat assuming flatness and going from there is the best way to fit the data. There are games that are played assuming the universe to be as far from flat as possible and, though the fits aren't quite as good, they are still in the same area for the other parameter measurements.

So basically, they're making it up as they go...

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Well, inasmuch as anybody speaking their native tongue is making up the language as they go.

This proves the point, that in the absence of other data and/or the flatness assumption, the WMAP data don't constrain things much. In particular, Crimson wonders whether Allan Sandage, who firmly believes the Hubble constant is in the 50s, will now advocate a slightly closed universe, which the WMAP data say yields a Hubble constant that he would like.

Two results from WMAP that do NOT depend on any assumption of flatness are:

(omega in baryons)h**2 = 0.0224
(omega)h**2 = 0.135

where omega is the total matter density (NOT including lambda) and h is the Hubble constant divided by 100 (e.g., h = 0.65 if the Hubble constant is 65).

http://www.hep.upenn.edu/%7Emax/cmb/movies.html

at the above link are Max Tegmark's movies of how the microwave anisotropy spectrum would change by changing various cosmological and other parameters.

I have an amusing thought about the inflationary-universe scenario.

That is represents a revival of the Bondi-Gold-Hoyle steady-state theory.

The inflationary phase featured approximately-exponential expansion -- which was exactly exponential for the steady-state theory.

The inflationary phase features quantum fluctuations seemingly coming out of nowhere, while the steady-state theory featured matter coming out of empty space.

You aren't the first person to notice the parallels, lpetrich. At AAS this January I attended a talk about Brane theory that made the very same point you did about spontaneous matter creation.

I have to admit not knowing enough about steady state "exponential" expansion to be able to comment in that area.