How do astronomers know how much dark energy and dark matter in the universe from a radio map?

Take a look at the map folks:

http://antwrp.gsfc.nasa.gov/apod/ap050925.html

How the heck can scientists determine the age and makeup of the universe
from this soup?

JD

On Tue, 04 Oct 2005 11:52:34 -0400, John Deer wrote:

Take a look at the map folks:

http://antwrp.gsfc.nasa.gov/apod/ap050925.html

How the heck can scientists determine the age and makeup of the universe
from this soup?

Do you really want to know the answer or is this a rhetorical question
revealing your own anti-science bias?

Just thought I'd ask before I waste my time trying to point you toward
an answer.

---
Michael McCulloch

Would an anti-science type be here and looking at APOD?
Yes I would like to know.

JD

Michael McCulloch wrote in
:


Do you really want to know the answer or is this a rhetorical question
revealing your own anti-science bias?

Just thought I'd ask before I waste my time trying to point you toward
an answer.

---
Michael McCulloch

John Deer wrote:
Take a look at the map folks:

http://antwrp.gsfc.nasa.gov/apod/ap050925.html

How the heck can scientists determine the age and makeup of the universe
from this soup?

I echo Michael's concern, but I'll give you my answer anyway.

First of all, astronomers do not determine the age and makeup of the
universe by just staring at that map any more than physicists determine
the age of a radioactive sample by listening at the Geiger counter.
Numerical analysis is done on the map, or the radioactive counts (and
accompanying decay products).

Secondly, what are astronomers looking for in the map, numerically?
Even visually, you can see that the map is not random and without
structure, the way a TV screen is on the (increasingly rare) occasions
when the station isn't broadcasting. You can easily tell that there
is a dark patch in the middle, and red patches (indicating, I *think*,
higher density) at right, at lower center, and at far left. You can
do spatial frequency analysis (in much the same way that your radio
does temporal frequency "analysis") to find patches of smaller size.

Now, these patches vary by size in two different ways. Generally, the
smaller ones are more common, and they are less intense. That is to
say, a smaller dark patch will not be as dark, and a smaller bright
patch won't be as bright. The precise manner in which these patches
vary by size (that is, by spatial frequency) tells astronomers much
about the early history of the universe, before it became essentially
transparent.

I should point out that the trend that smaller patches are more common
and less intense is only a general trend: I understand that there are
certain spatial frequencies where that trend does not hold true, and
just like emission lines in spectrographs, these are particular
indicators of cosmological history.

Thirdly, dark matter and dark energy cannot, at the present time, be
detected indirectly (that's why they're called dark) in any event.
There is no way to take this picture, or any other picture, and point
to a certain feature and say, "Aha, there's the dark energy." (Or
matter, for that--uh--matter.) Their effect, as far as we understand
it at present, is only to modulate the expansion of the universe, and
to affect the evolution of galactic clusters and superclusters. Both
of these are reflected to some degree in the WMAP image.

In short, there is much about astronomical work that can't be stuffed
into a single APOD paragraph, and people should be wary of assuming,
just because they can't understand how a conclusion is arrived at,
that there is no understanding to be had at all.

--
Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

John Deer wrote:
Would an anti-science type be here and looking at APOD?

I know your question is rhetorical, but actually the answer is yes.
There are lots of people who would like to see establishment science
get egg on their face, and they are only too willing to apply their
poorly remembered fourth-grade science miseducation to that end.

That's one reason why they say a little knowledge is a dangerous thing.

--
Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

John Deer wrote:
Would an anti-science type be here and looking at APOD?
Yes I would like to know.


Certain characteristics of the universe are put into cosmological
models such as how much dark energy and dark matter are in the universe,
then the models are tweaked and tweaked until there is good agreement
with the observables.

The First Detailed Full Sky Picture of the Oldest Light in the Universe
http://map.gsfc.nasa.gov/m_mm.html

Also see Ned Wright's Cosmology Tutorial
http://www.astro.ucla.edu/~wright/cosmolog.htm
http://www.astro.ucla.edu/~wright/cosmology_faq.html

WMAP: Foundations of the Big Bang theory
http://map.gsfc.nasa.gov/m_uni.html

WMAP: Tests of Big Bang Cosmology
http://map.gsfc.nasa.gov/m_uni/uni_101bbtest.html


PHYSICS NEWS UPDATE
The American Institute of Physics Bulletin of Physics News
Number 624 February 13, 2003 by Phillip F. Schewe, Ben Stein, James
Riordon

A PINPOINT PRECISION MAP of the cosmic microwave background, reported this
week at a press conference by scientists associated with the orbiting
Wilkinson Microwave Anisotropy Probe (WMAP), brings the early universe into
sharper focus. The credibility of WMAP's pronouncement rests on three
things: its angular resolution is some 40 times better than that of its
microwave predecessor, the Cosmic Background Explorer (COBE); it
comprehensively surveyed the entire sky for a whole year (3 more years of
data is yet to come); and it measures the polarization of the microwave
radiation; the orientation of the radiation arises partly from the last
scattering of light at the time of "recombination," when stable atoms
formed for the first time, and partly from the time when ultraviolet
radiation strewn by the first generation of stars ionized once again a lot
of atoms in space. Here are a few of the salient numbers coming out of the
WMAP analysis: the time of recombination was 380,000 years after the big
bang; the era of the first stars was about 200 million years along
(surprisingly early); the age of the universe is 13.7 billion years; and the
accounting of matter in the universe is as follows: atomic matter makes up
about 4%, dark matter about 23%, and dark energy 73%. (Websites:
http://map.gsfc.nasa.gov/;
http://www.gsfc.nasa.gov/topstory/20...apresults.html)

Ref: http://www.astro.ucla.edu/~wright/cosmolog.htm#News

MAP Data Released!

11 Feb 2003 - The results from the first year of observing by the
Wilkinson Microwave Anisotropy Probe were announced today at a Space
Science Update in the auditorium of NASA HQ. Important results
include:

o The satellite has been renamed in honor of the late David T.
Wilkinson of Princeton University, a key member of the project from
its conception.

o The polarization of the microwave background anisotropy coming
from scattering by electrons 200 million years after the Big Bang
has been detected. This is evidence for an early generation of
stars existing 4 to 5 times earlier than any object yet observed.

o The WMAP data agree with previous work showing the Universe is
flat and in an accelerating expansion.

o The WMAP data give the most precise values for the density of
ordinary [baryonic] matter made of protons and neutrons and for the
dark matter: 0.4 and 2.5 yoctograms per cubic meter. These
correspond to omega_b = 0.0224 +/- 0.0009 and omega_m = 0.135 +/-
0.009.

o The WMAP data give the most precise value for the age of the
Universe: 13.7 +/- 0.2 Gyr. The Hubble constant is Ho = 71 +/- 4
km/sec/Mpc, and the vacuum energy density corresponds to lambda =
0.73 +/- 0.04. 13 papers by the science team and the maps and
power spectra are available by clicking on the image above.

See: http://www.astro.ucla.edu/~wright/cosmolog.htm#News

Ref: http://www.aip.org/enews/physnews/2003/659.html
Physics News Update Update #659 (October 28, 2003)

A Map of the Universe

A map of the universe produced by the Sloan Digital Sky Survey contains
200,000 galaxies at distances of up to two billion light years, and
spread out across 2400 square degrees of sky. According to Sloan
astronomer Michael Blanton (NYU), this is "the best three-dimensional
map of the universe to date." The Sloan effort uses a telescope in New
Mexico optimized to record spectra from many galaxies at the same time.
One of the standout features of the map is the Sloan Great Wall of
galaxies, some 1.37 billion light years long and the "largest observed
structure in the universe" (preprint:astro-ph 0310/0310571) Combined
with data from other telescopes, such as the Wilkinson Microwave
Anisotropy Probe (WMAP), the new Sloan observations help tamp down
uncertainties in several pivotal astronomical numbers. The new best
value for the Hubble constant is 0.70 with an uncertainty of about
0.04; the amount of energy in the universe vested in matter is 30% with
an uncertainty of 4%; the upper limit on neutrino mass is 0.6 eV; and
the age of the universe is 14.1 billion years with an uncertainty of 1
billion (Preprint astro-ph/0310/0310723; visit Sloan website).

"Brian Tung" wrote in message
snip
In short, there is much about astronomical work that can't be stuffed
into a single APOD paragraph, and people should be wary of assuming,
just because they can't understand how a conclusion is arrived at,
that there is no understanding to be had at all.

That's a good point but there's a counter point: even though a cosmologist
says it, it might be erroneous. g

As a non-physicist, I am often left with the *impression* that dark matter
and dark energy are concepts that have arisen as fudge-factors to preserve
current theories. In other words, their existence is postulated to "make the
math work" within the current cosmological paradigm. It leaves me
wondering whether the underlying theory is in need of this patch because it
is flawed.

I'm not disputing their existence, only relaying my *impressions*. It is
likely, as Brian points out, the advocates of dark matter/dark energy theory
have formed their ideas with the help of a superior understanding.

Ed T.

On Tue, 04 Oct 2005 17:55:58 GMT, "Ed T" wrote:

As a non-physicist, I am often left with the *impression* that dark matter
and dark energy are concepts that have arisen as fudge-factors to preserve
current theories. In other words, their existence is postulated to "make the
math work" within the current cosmological paradigm. It leaves me
wondering whether the underlying theory is in need of this patch because it
is flawed.

In spite of similar sounding names, dark matter and dark energy are
totally different things. While the existence of dark matter has
cosmological implications, its observation is much less cosmological. We
can observe the effects of dark matter locally- in the motion of our own
galaxy and in galaxies nearby. We also have some fair understanding of
the sort of particles that could constitute dark matter. Because of
this, its existence is pretty widely accepted. Dark matter doesn't
necessarily require a lot of new physics.

Dark energy, on the other hand, is only inferred from the motion of the
Universe on a cosmological scale, and the underlying physics is almost
completely undeveloped. Dark energy is much more a "fudge factor" than
dark matter. The existence of dark energy is much more uncertain- there
are cosmological theories that can potentially explain the way the
Universe is expanding without requiring dark energy.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

John Deer wrote:
Would an anti-science type be here and looking at APOD?
Yes I would like to know.

Actually, we have anti-science trolls here all the time.

That said, the simplest answer is to say that there are
different theories about the makeup of the universe. Think of
them as different recipes to make a universe. You take each
recipe and project the kind of universe it would produce. With
the photo you mentioned, they project each theory (recipe) to
see how uniform a universe it would form at the point in time
when light was able to travel through the universe. You are
looking not only at how uniform it is, but the size and
distribution of various clumps of matter.

So imagine we have theories A,B and C. Each is a different
recipe for creating a universe. You work each recipe to see
what kind of distribution it produces. Then you look at the
map and see which theory matches the reality.

Hope this helps.

Chuck Taylor
*********************************************
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http://groups.yahoo.com/group/lunar-observing/

If you enjoy optics, try
http://groups.yahoo.com/group/ATM_Optics_Software/
*********************************************

Chris L Peterson wrote:
In spite of similar sounding names, dark matter and dark energy are
totally different things. While the existence of dark matter has
cosmological implications, its observation is much less cosmological. We
can observe the effects of dark matter locally- in the motion of our own
galaxy and in galaxies nearby. We also have some fair understanding of
the sort of particles that could constitute dark matter. Because of
this, its existence is pretty widely accepted. Dark matter doesn't
necessarily require a lot of new physics.

Right--the distribution of dark matter isn't what's mysterious. By
observing cluster dynamics, we can tell it hangs around ordinary matter.
The only thing about it that's dark is that we can't see it; it doesn't
interact very strongly with electromagnetic radiation the way that
ordinary matter does.

Dark energy, on the other hand, is only inferred from the motion of the
Universe on a cosmological scale, and the underlying physics is almost
completely undeveloped. Dark energy is much more a "fudge factor" than
dark matter. The existence of dark energy is much more uncertain- there
are cosmological theories that can potentially explain the way the
Universe is expanding without requiring dark energy.

I point out, however, that although it's a fudge factor, it's not wholly
arbitrary. It's sort of like precession, which was observed long before
it was explained by Newton. It wasn't a random, aimless wandering; it
was systematic change, with a smooth trend over time. So, in a way, is
dark energy.

--
Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt