Mar 12, 2025 06:08 PM
https://bigthink.com/starts-with-a-bang/...-big-bang/
EXCERPTS: Instead of beginning with a hot Big Bang, inflation states that an earlier state preceded it: one where all the energy in the Universe was bound up in a different form, inherent to the fabric of space itself. This causes space to expand relentlessly and exponentially — doubling and redoubling in size again with each brief instant that elapses — for as long as inflation endures. This means that:
That’s very compelling, but remember: to overthrow an old scientific theory and replace it with a new one, we need to make novel predictions that we can go out and test! Fortunately, inflation has these in spades, largely because of quantum physics! If the Universe is quantum in nature, then inflation must be a quantum field, and quantum fields fluctuate. During inflation, these fluctuations get stretched across the Universe, becoming the seeds for both density fluctuations and gravitational wave fluctuations that our Universe gets “born” with once inflation ends and the hot Big Bang begins. This leads to seven unique predictions.
[...] Of those seven predictions, we’ve sufficiently tested the first four. Inflation is four-for-four, and the non-inflationary hot Big Bang is zero-for-four. That’s a slam dunk, a smoking gun for inflation, and an overwhelmingly convincing scientific test all at once.
[...] The level of profundity of the implications of all of this cannot be overstated. It means that the Big Bang wasn’t the beginning of the Universe, but rather was preceded and set up by cosmic inflation. Inflation isn’t some speculative idea that hasn’t been tested; it’s cleared all three of the major scientific hurdles that any new theory must clear to become accepted.
[...] Meanwhile, future experiments can continue to probe the remaining, insufficiently tested predictions.
[...] The goal now isn’t to confirm inflation; we’ve done that. The goal at present is to learn more about what the properties were of the inflation that occurred in the Universe, to investigate what preceded and set up inflation, and to find out whether our Universe truly did have a beginning way back before our observations can give us any meaningful information, and what that initial state was like. The Big Bang still plays a major role in cosmic history, but it wasn’t our ultimate beginning... (MORE - missing details)
EXCERPTS: Instead of beginning with a hot Big Bang, inflation states that an earlier state preceded it: one where all the energy in the Universe was bound up in a different form, inherent to the fabric of space itself. This causes space to expand relentlessly and exponentially — doubling and redoubling in size again with each brief instant that elapses — for as long as inflation endures. This means that:
- all different regions of space, even apparently causally disconnected ones, would have the same properties everywhere, as they originated from the same inflationary region,
- the expansion rate and the energy density of the Universe perfectly match, because the energy density during inflation determines the expansion rate,
- and there are no leftover high-energy relics because the Big Bang never got infinitely hot, but rather only got as hot as the energy density during inflation would have allowed.
That’s very compelling, but remember: to overthrow an old scientific theory and replace it with a new one, we need to make novel predictions that we can go out and test! Fortunately, inflation has these in spades, largely because of quantum physics! If the Universe is quantum in nature, then inflation must be a quantum field, and quantum fields fluctuate. During inflation, these fluctuations get stretched across the Universe, becoming the seeds for both density fluctuations and gravitational wave fluctuations that our Universe gets “born” with once inflation ends and the hot Big Bang begins. This leads to seven unique predictions.
[...] Of those seven predictions, we’ve sufficiently tested the first four. Inflation is four-for-four, and the non-inflationary hot Big Bang is zero-for-four. That’s a slam dunk, a smoking gun for inflation, and an overwhelmingly convincing scientific test all at once.
[...] The level of profundity of the implications of all of this cannot be overstated. It means that the Big Bang wasn’t the beginning of the Universe, but rather was preceded and set up by cosmic inflation. Inflation isn’t some speculative idea that hasn’t been tested; it’s cleared all three of the major scientific hurdles that any new theory must clear to become accepted.
[...] Meanwhile, future experiments can continue to probe the remaining, insufficiently tested predictions.
[...] The goal now isn’t to confirm inflation; we’ve done that. The goal at present is to learn more about what the properties were of the inflation that occurred in the Universe, to investigate what preceded and set up inflation, and to find out whether our Universe truly did have a beginning way back before our observations can give us any meaningful information, and what that initial state was like. The Big Bang still plays a major role in cosmic history, but it wasn’t our ultimate beginning... (MORE - missing details)