Far out cosmology: fine-tuned universe: (Introduction)

by David Turell , Saturday, May 27, 2023, 18:42 (544 days ago) @ David Turell

Five specific items had to be perfect or the universes would not be here in its current form:

https://bigthink.com/starts-with-a-bang/5-what-ifs-change-cosmic-history/?utm_campaign=...

"1.) What if the Universe were actually perfectly uniform when it was born? This one is not something that’s greatly appreciated: the Universe, as we know it, couldn’t have been born perfectly smooth. If we had possessed an exactly equal amount of matter-and-antimatter-and-radiation everywhere, at all locations in space, going all the way back to the earliest moments of the hot Big Bang, every point in the Universe would experience an equal gravitational force pulling on it in all directions. In other words, the idea of gravitational growth and collapse relies on an initial imperfection to grow from. Without the seed, you can’t get the desired end result, like a star, galaxy, or something even larger.

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"If our Universe were born exactly, perfectly uniform, there would be no structure, no stars, and no interesting chemical reactions to speak of anywhere in the cosmos.

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"2.) What if the expansion rate and the effects of gravitation were less perfectly balanced? This one is a bit tricky. We normally think of the Universe as a fairly stable place, but that’s only because there are two things that have been so well-balanced for so long: the rate at which the Universe expands and the decelerating effects of all the matter and radiation in the Universe. Today, these two effects don’t match, and that’s why we say the expansion of the Universe is accelerating.

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"What’s remarkable is when we consider how perfectly balanced these two quantities must have been. Today, the Universe has a density of about 1 proton per cubic meter of space. But early on, it had a density that was more like quintillions of kilograms per cubic centimeter of space. If you would have increased or decreased that density by just 0.00000000001%, the Universe would have: recollapsed on itself, ending in a Big Crunch after less than 1 second, in the case of an increase, or expanded so quickly that no protons and electrons would ever have found one another to form even a single atom in the Universe, in the case of a decrease.
This incredible balance, along with the need for it, highlights just how precarious our existence in this Universe is.

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"3.) What if there had been exactly equal amounts of matter and antimatter? This is another problematic one for us, and in fact it’s one of the greatest unsolved problems in all of physics: why do we live in a Universe with more matter than antimatter? This puzzle has many possible resolutions, but no definitive answer. What we can say, for certain, is that:

"in the early stages of the hot Big Bang, the Universe should have been perfectly symmetric between matter and antimatter, and that somehow, some process occurred that resulted in the existence of approximately 1,000,000,001 matter particles for every 1,000,000,000 antimatter particles, and when the excess annihilated away, we were left with that tiny bit of matter amidst a leftover bath of radiation. That radiation still survives, as does the matter, which is why we can reconstruct what happened at early times.

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"If our Universe hadn’t created a matter-antimatter asymmetry early on, none of the remarkable steps that came afterward to lead to our existence could have taken place.

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"4.) What if there hadn’t been any dark matter?...Most of us think about dark matter as the “glue” that holds the largest structures in the Universe together: things like the cosmic web and enormous galaxy clusters. But dark matter also does two particularly important things we don’t typically think about: it provides the majority of the gravitational mass that both forms all galaxies in the Universe and continues to hold them together, and it prevents structure from being “washed out” by the interactions that exist between normal matter and radiation.

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'In a Universe with no dark matter, only that first generation of stars would exist, meaning there would be no rocky planets, no biochemistry, and no life.

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"5.) What if dark energy weren’t constant in space or time? This is the one possibility that’s still on the table for our Universe: that dark energy might evolve in some fashion. To the best of our observational limits, it certainly looks and behaves like a cosmological constant — as a form of energy inherent to the fabric of space itself — where the energy density remains constant in time and all throughout space.

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"If dark energy strengthens, the Universe could rip apart. If dark energy weakens or reverses its sign, the Universe could yet recollapse. And if dark energy decays, the Universe as we know it could end. None of these things have happened yet, but if the Universe were only slightly different, any one of them could have taken place in the past, precluding our existence from occurring at all.

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"All of this, when taken together, leads us to a fascinating conclusion: if any of these things were — in any way — substantially different from the way they are, it would have been a physical impossibility for human beings to have arisen as we did within the Universe."

Comment: a different perspective on the fine tuning of the formation of this universe. It was designed.