Why Is Heat Distribution Unequal in the Expanding Universe?

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Discussion Overview

The discussion centers around the unequal distribution of heat in the expanding universe, particularly in relation to the Big Bang and the cosmic microwave background radiation (CMB). Participants explore theoretical explanations, including the horizon problem and inflation, while also addressing misconceptions about the nature of the Big Bang and heat transfer.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions why there are not unequal heat regions in the universe despite the slower spread of heat compared to light during the Big Bang expansion.
  • Another participant introduces the "horizon problem" and suggests that inflation provides a solution, referencing the equal temperatures observed in the CMB despite the lack of common events influencing them.
  • A different viewpoint emphasizes that heat transfer involves kinetic and photonic energy, suggesting that the process is more complex than simply comparing speeds.
  • Another participant clarifies misconceptions about the Big Bang, stating it was not a conventional explosion and did not expand at the speed of light, while also noting observable variations in the CMB.

Areas of Agreement / Disagreement

Participants express differing views on the nature of heat transfer and the implications of the Big Bang, with some supporting the inflationary model as an explanation for the horizon problem, while others challenge the interpretations and clarify misconceptions. No consensus is reached.

Contextual Notes

Participants highlight limitations in understanding the speed of heat transfer and the nature of the Big Bang, as well as the complexities involved in the observations of the CMB. There are unresolved aspects regarding the implications of inflation and the horizon problem.

csrichie
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I ran across this on a website. The problem is, because heat spreads out slower than light, when the big bang explodes and expands at the speed of light then there should be unequal heat regions all over the universe. But this is not true according to observation. Why is this so?
 
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csrichie said:
I ran across this on a website. The problem is, because heat spreads out slower than light, when the big bang explodes and expands at the speed of light then there should be unequal heat regions all over the universe. But this is not true according to observation. Why is this so?

The standard explanation is inflation. The problem is known as "the horizon problem". See for instance http://www.astro.ucla.edu/~wright/cosmoall.htm (I'll provide a short quote to point out the specific applicable section).

Any event that influences the temperature of the CMB that we see on the left side of the sky must be within the left-hand yellow region. Any event that affects the temperature of the CMB on the right side of the sky must be within the right-hand yellow region. These regions have no events in common, but the two temperatures are equal to better than 1 part in 10,000. How is this possible? This is known as the "horizon" problem in cosmology.

Inflation

The "inflationary scenario", developed by Starobinsky and by Guth, offers a solution to the flatness-oldness problem and the horizon problem.

The "flatness-oldness" problem (i.e. why omega is close to one) is also explained by inflation.
 
That does not make any sense to me, csrichie. Heat is transferred by kinetic and photonic energy, according to current theories. The speed of transfer is interrupted by molecules jostling for a more stable position in the grand scheme of things.
 
csrichie said:
... when the big bang explodes and expands at the speed of light ...
Note that the Big Bang was not like a conventional "explosion" (it was, in part, the rapid expansion of all space) Also, it didn't expand at the speed of light (at least, not for more than an instant as you'll see from pervect's info about the inflationary period). Also note that there are observable variations in the cosmic microwave background radiation.
 

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