Posted on 01/09/2002 5:24:37 AM PST by Darth Reagan
Actually, if you stick out a thermometer into the intergalactic medium, you'd get a reading of nearly absolute zero. There would be very few photons or massive particles contacting the surface of the thermometer. Whatever heat it originally had would simply radiate in the infrared out into the vacuum with very little input to balance the loss.
The same thermometer, anywhere in the universe a few seconds after the big bang, would have been vaporized. In fact, the nucleons would have flown apart into sub-atomic particles, which would have themselves become a quark-gluon like the rest of the universe.
So I guess it depends on what you mean by "temperature."
A little background: Radio astronomers use temperature to describe the strength of detected radiation. Any body with a temperature above -273 deg C (approximately absolute 0) emits electromagnetic radiation (EM). This thermal radiation isn’t just in the infrared but is exhibited across the entire electromagnetic spectrum. (Note: it will have a greater intensity (peak) at a specific area of the EM spectrum depending on its temperature). For example, bodies at 2000 K (Kelvin), the radiation is primarily in the infrared region and at 10000 K, the radiation is primarily in the visible light region. There is also a direct correlation between temperature and the amount of energy emitted, which is described by Planck’s law.
When the temperature of a body is lowered, two things happen. First, the peak shifts in the direction towards the longer wavelengths and second, it emits less radiation at all wavelengths.
This turns out to be extremely useful. When a radio astronomer looks at a particular point of the sky and says that it has a noise temperature of 1500 K, he/she isn’t declaring how hot the body (nebulae, etc) really is, but is providing a measurement of the strength of the radiation from the source at the observed frequency. For example, radiation from an extra solar body may be heated from a nearby source such as a star. If this body is radiating at a temperature of 500 K, it exhibits the same emissions across all frequencies that a local test source does. The calculated noise figure will be the same across all frequencies. (Note: this does not take into account other sources of radiation such as synchrotron radiation).
So, here’s the rub. Not only does the source that is of interest to the radio astronomer emit thermal radiation but also both the local environment (ground, atmosphere, etc) and the equipment (antenna, amplifiers, cables, receiver, etc) being used to make the measurements. To accurately observe and measure the distant sources, the radio astronomer must subtract all of the local environment and detection equipment noise additions.
In 1963, Arno Penzias and Robert Wilson were working with a horn antenna trying to make it work with as high efficiency as possible for the Telstar project. This antenna was also going to be used for radio astronomy at a later date. They pointed it to a quiet part of the sky and took measurements. When they subtracted all of the known sources of noise, they found approximately 3 K left over. They worked very diligently to eliminate/describe this noise source and were unable to. This mysterious source of noise seemed to be there no matter where they pointed the antenna. What they had discovered was the microwave background produced from the Big Bang. This 3 (closer to 2.7) K microwave background originated approximately 300,000 years after the Big Bang itself had occurred. It has been determined that when these signals originated, the universe had already cooled down to around 3000 K.
As far as the Lyman Alpha Forest statement, here is a web site that may answer your questions better than I can without taking up two pages :)
A currently popular variation of the big bang theory is that there was a brief, initial spurt of incredibly rapid expansion. This is the "inflationary" scenario, and I understand that there are actually several versions of it. Inflation solves some problems that "classic" big bang theory left in its wake ("smoothness" among them) but I have my doubts that inflation theory is well developed yet. Everyone has doubts about something, but we plunge ahead anyway. Anyway, FTL expansion is considered a possibility at this very early stage. It seems to be theoretically permissible, at least in the sense that no causality paradoxes could have occured. And as a result, some things may appear to be farther away than the age of the universe would seem to allow. Of course, their light wouldn't have had time to get to us yet, so it's not something we're going to worry about today. Everyone confused? Fine. Class dismissed.
I do not.
If not, I would be very interested to understand why you do not?
To me, it isn't a question of how the universe, after the Big Bang, would lose its perfect uniformity, but how could possibly be maintained? The uniformity isn't stable, on any level. At the crude level of matter distribution, you have quantum fluctuations that are intrinsically random, and these are constantly being magnified exponentially by the "butterfly effect" (deterministic chaos).
But there are deeper levels of non-uniformity having to do with the structure of the vacuum that must be avoided when "growing" a universe. Early cosmological models were plagued by an unsupportable density of "flaws" in the vacuum: magnetic monopoles (analogous to point dislocations in the growing of a crystal), cosmic strings (analogous to screw dislocations), and domain walls (analogous to fractures). We do not observe any of these structures in the universe. At the level of quantum field theory, the universe is far more uniform than we would naively expect it to be.
Inflationary models solved this problem by starting with a tiny region of space containing a small number of flaws and stretching it to gigantic size; the number of flaws remains constant for topological reasons, so the density goes rapidly to something close to zero.
" . . . become a quark-gluon plasma . . ."
http://nedwww.ipac.caltech.edu/level5/March01/Carroll3/Carroll_contents.html
I am not a particle physicist but the "flaws" are a result of the CP mirror?
You know this is incomprehensible, don't you?
Assuming this small point was in the middle of nowhere and now it isn't in the middle of anywhere and the expansion is ongoing at an indeterminate rate, any manner of suppositions could and will be made regarding its origin, makeup and future.
The human mind isn't large enough for such a notion.
Not at all. Think of dots on the surface of an expanding balloon. They appear to be rushing away from each other as the balloon expands. The further the dots are apart, the faster they separate. At the beginning, they were all at the same point. The universe can be looked at in the same way. An expansion of space-time fron a single point. Everywhere was at that point in the beginning.
No! No! It used to not be in the middle of anywhere! Now it's in the middle of nowhere.
;)
Of course it is. Cosmologists know that. They don't usually talk about that aspect except when they are having coffee away from prying ears.
The Big Crunch. (Maybe)
There does not appear to be enough mass in the universe to cause a "Big Crunch". Basically the universe as a whole appears to be extremely "flat" cosmologically.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.
