/sci/ - Science & Math

>>11650730

But all of this only gets us back to 400,000 years after the Big Bang. We can rewind further. At an age of a few seconds, we predict that all of the universe was much hotter than the very center of a star and remained so for around 20 minutes. During this time, nuclear fusion raged across the cosmos, baking some of the existing protons into heavier elements in a process that we call primordial nucleosynthesis. The Big Bang theory tells us how long these elements were baked and at what temperature, and so predicts the proportions of deuterium, helium, and lithium that should have been produced. It's in startling agreement with what we see when we look out there. The Big Bang theory has powerful, direct evidence, almost down to the first second. Although we don't have direct evidence for what the universe looks like in its very first second, our understanding of physics is still good down to a crazily early age of 10^32 seconds, when the entire current observable universe was around the size of a grain of sand, give or take. How can we be so confident? Because we've recreated the conditions of the universe at this time. We've recreated those insane energies in our particle accelerators. We can check that our physics works in these conditions, and so we have a lot of confidence in the predictions of that physics.

However, this is where our certainty ends. Earlier than 10 to the power of minus 32 seconds, we just can't produce the energies needed to test our understanding of physics in those conditions. But there are clues to that earliest of times. Some are also imprinted in the cosmic microwave background, and they may lead us back to the instant of the Big Bang itself.