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Astrophysics/What temperature is assumed there was at the time of the big bang?


Greetings to you all,
I could clarify one thing (assuming they can clarify it?)

What temperature is assumed that there has been during the big bang or singularity? I mean in the beginning, not after 1 second or less.
I ask this because sometimes I read that in the beginning the temperature was infinite. But my opinion is that this idea is a logical fallacy, because if we start from an infinite number (the number that represents the temperature), we could never reach the temperature of the universe we have today (although the big bang to date have passed 15 billion years).
You taught me that if we start from an infinite number and then subtract from this number the degree of which we assume has cooled the universe, as a result we will have another infinite number ....
But then (always starting from the assumption that at the beginning the temperature was <infinite>, and then after 15 billion years that we have the current temperature is about 3 degrees Kelvin ..... how do you explain that?
Even if the universe had cooled down (random numbers) of 10 billion degrees from the big bang to the present, I should do (infinite - 10000000000 = 3 degrees), but this as you know,we can not do .. .



You ask a very good question! Technically speaking, given that the concept of 'temperature' implies an *averaged* macroscopic property - i.e. implying two systems have been in thermal contact (e.g. a thermometric medium with another body) then there is no temperature that can be registered at the exact Big Bang singularity.

Another aspect to that: given this singularity is presumed to be 'atom-sized' there can be no temperature since one cannot take the temperature of an atom (or a molecule) for that matter.

A plasma in space, or the outer corona of the Sun would be a different matter, since the kinetic energies of the particles will yield what we call a 'kinetic temperature' (for the corona it's roughly 2 million Kelvin).

But this makes no sense applied to the exact instant of the Big Bang.

Alas, too many astronomy texts are guilty of claiming absurd magnitudes - like "infinite" temperature - even when this is only a metaphor and ought to be stated as such.  


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Philip A. Stahl


I specialize in stellar and solar astrophysics. Can answer questions pertaining to these areas, including: stellar structure and evolution, HR diagrams, binary systems, collapsars (black holes, neutron stars) stellar atmospheres and the spectroscopic analysis of stars as well as the magnetohydrodynamics of sunspots and solar flares. Sorry No homework problems done or research projects! I will provide hints on solutions. No nonsense questions accepted, i.e. pertaining to astrology, or 'UFOs' or overly speculative questions: 'traveling through or near black holes, worm holes, time travel etc. Absolutely NO questions based on the twaddle at this Canadian site: purporting to show a "new physics". Do not waste my time or yours by wasting bandwidith with reference to such bunkum.


Have constructed computerized stellar models; MHD research. Gave workshops in astrophysics (stellar spectroscopy, analysis) at Harry Bayley Observatory, Barbados. More than twenty years spent in solar physics research, including discovery of SID flares. Developed first ever consistent magnetic arcade model for solar flares incorporating energy dissipation and accumulation. Developed first ever loop-based solar flare model using double layers and incorporating cavity resonators. (Paper presented at Joint AGU/AAS Meeting in Baltimore, MD, May 1994)

American Astronomical Society (Solar physics and Dynamical astronomy divisions), American Geophysical Union, American Mathematical Society, Intertel.

Papers appearing in Solar Physics, Journal of the Royal Astronomical Society of Canada, Journal of the Barbados Astronomical Society, Meudon Solar Flare Proceedings (Meudon, France). Books: 'Fundamentals of Solar Physics', 'Selected Analyses in Solar Flare Plasma Dynamics', 'Physics Notes for Advanced Level', 'Astronomy & Astrophysics: Notes, Problems and Solutions', 'Modern Physics: Notes, Problems and Solutions'

B.A. degree in Astronomy; M.Phil. degree in Physics - specializing in solar physics.

Awards and Honors
Postgraduate research award- Barbados government; Studentship Award in Solar Physics - American Astronomical Society. Barbados Astronomical Society award for service (1977-91) as Journal editor.

Past/Present Clients
Caribbean Examinations Council (as advisor, examiner), Barbados Astronomical Society (as Journal Editor 1977-91), Trinidad & Tobago Astronomical Society (as consultant on courses, methods of instruction, and guest speaker).

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