Tuesday, 4 July 2017

energy conservation - When they say that the universe cooled after the big bang, where did the heat go?


Layman here,


Stumbling through some physics stack posts and started reading the Wikipedia for the chronology of the big bang. In it, it states



The very earliest universe was so hot, or energetic, that initially no matter particles existed or could exist except perhaps fleetingly, and the forces we see around us today were believed to be merged into one unified force. Space-time itself expanded during an inflationary epoch due to the immensity of the energies involved. Gradually the immense energies cooled – still to a temperature inconceivably hot compared to any we see around us now, but sufficiently to allow forces to gradually undergo symmetry breaking, a kind of repeated condensation from one status quo to another, leading finally to the separation of the strong force from the electroweak force and the first particles.




Where is the "immense energy" going to when it is "cooled"? Is there now no "immense energy"?



Answer



Temperature means energy. The heat energy is still here. It's just that the "object" (the Universe) grown bigger so this energy had to spread through it. The more energy in a single point, the hotter it is. That's why they say it got cooler. It's like the expanding gas from your spray deodorant is cold when it leaves the can, but it was at room temperature inside the can. The energy is still the same.


Please note that this is just a simple analogy and it should be aknowledged that there are much more complex processes involved. It was asked for an Layman's answer.


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