been pointed here by another site. Grateful for any responses i receive. I'm an author not a scientist. For an article I'm writing I'm trying to describe the Big Bang in layman's terms. Specifically I would like to know what visible light there would be during and after BB and what was producing it and what colour it would be. Further, I imagine a big bang is somewhat hot, how would cooling down affect the colour the visible light? Cheers everyone, stay safe.
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1There are two tricky points: 1) It really depends on what you mean by the word "during" in the phrase "during the Big Bang". We understand what the universe was like very shortly after the Big Bang. Depending on who you ask, we understand essentially what the universe was like starting at somewhere between $10^{-32}$ seconds and $10^{-12}$ seconds after the Big Bang. Going any earlier than that involves physics that hasn't been discovered yet. – probably_someone Mar 31 '20 at 02:21
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- The very early universe was essentially opaque (the technical term is optically thick) to basically everything but very high-energy gamma rays. Visible light couldn't travel very far at all before interacting with something else. This continued until hundreds of thousands of years afterward, when the universe finally cooled off enough for atoms to be stable; at that point, the dense, ambient light pervading the universe was suddenly able to travel. That light still persists today, redshifted into what we now know as the cosmic microwave background.
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Thank you for that. I have read about opaque light and it is most interesting. Also aware you're talking about Planck time. But are you saying there would have been no visible light at all, forget during but after. If so, can word picture it for me, ie what would that look like or what otherwise what do you think you would see after 10-12 ? Any clues or insights would be greatly appreciated! – Chess Wade Mar 31 '20 at 02:53
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As probably_someone said, the universe was originally a bright opaque fog. After about 379,000 years it cooled enough to start becoming transparent, and at that time its colour was orange, as shown here: https://physics.stackexchange.com/a/133943/123208 – PM 2Ring Mar 31 '20 at 06:58
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Assuming we're in an era of the universe that is describable using known physics:
If you were somehow able to be suspended inside the early universe, in a suit that somehow prevented you from getting cooked or instantly, fatally radiation-poisoned in the multi-trillion-degree plasma you were immersed in, and with a filter that blocked out all light except for visible light so you wouldn't fry your eyeballs instantly just from looking at the plasma: it would be incredibly, indescribably bright, no matter where you were standing. The light that reached your eyes would be generated by the plasma directly in front of them, and that's all you would see. You would likely go blind unless you only let in a tiny fraction of the visible light incident on your visor.
The spectrum of radiation would be very close to blackbody radiation, with a peak far, far higher in frequency than visible light. Filtering just for visible light, as far as color, it would be basically white (the blackbody radiation peak is so far away from visible light in this case that all colors would be at basically the same intensity).
probably_someone
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Thank you very much i was already homing in on black body radiation. And advice concerning surviving in the midst of all that is understood. Thank you for making it clearer to me, I now have to try and do the same for my readers! Cheers probably_someone, love the handle. – Chess Wade Mar 31 '20 at 06:11