Calculations show that everything we see today, from atoms to galaxies,
exists because just one extra particle of matter survived for every billion
matter–antimatter pairs.
* The early universe produced slightly more matter than antimatter, and they annihilated until matter and energy remained.
* The early universe produced overwhelmingly normal matter and energy, and almost no antimatter.
With increasing temperature, the thresholds of generation for various particle-antiparticle pairs are exceeded, so those kinds of particles and antiparticles are generated in collisions and become a component of the matter of that temperature.
At very high temperatures, matter is composed of almost equal quantities of particles and antiparticles, of a very large number of kinds.
With cooling, some particle-antiparticle pairs are no longer generated and the existing are annihilated, so they cease to be a component of matter.
When the temperature diminishes to a few tens of MeV, then the only particle-antiparticle pairs that remain are of electrons and positrons, while the rest of the matter consists only of free protons, free neutrons, photons and various kinds of neutrinos.
With further cooling, protons and neutrons begin to bind into nuclei, i.e. nuclei of isotopes of hydrogen, helium and lithium.
Then, with even further cooling, the temperature becomes insufficient for generating positrons, so the huge number of existing electrons and positrons annihilate with each other, leaving a much smaller number of electrons, which is equal to the number of protons (free or bound in nuclei of deuterium, He isotopes and Li isotopes), and the amount of charged antiparticles becomes negligible.
At the stage when the temperature is a few tens of MeV and the variety of the particles composing matter is minimal, any memory of what may have happened at other temperatures is erased.
Thus, we cannot extrapolate the Big Bang towards higher temperatures, because there is no evidence of what may have happened before, e.g. of whether higher temperatures have ever existed. The existing evidence could also be matched by a cooler earlier Universe, which has been heated somehow up to a temperature of a few tens of MeV, decomposing any previous matter.
Our astronomical data is consistent with the visible Universe starting at a temperature of a few tens of MeV and high concentration, then cooling and expanding from that state, e.g. this explains the observed chemical composition of the celestial objects.
It can be fun to speculate about what may have happened before that, but it must be kept in mind that for now there is no way to verify any theory that attempts to model earlier stages, e.g. there is no way to verify if the Universe had ever been hotter than a few tens of MeV, i.e. if there have ever been any other abundant antiparticles except positrons (and antineutrinos, which remain abundant even at the present low temperatures, but the nature of antineutrinos is not well understood even today, as anything else that are named antiparticles participate in electromagnetic generation/annihilation reactions with their particle correspondent, while the exact differences between neutrinos and antineutrinos are not clear).
Like I have said, one can hypothesize that before that state when the temperature was in the range of tens of MeV the matter had been even hotter, or on the contrary, that it was cooler, but either way there is no evidence for any earlier conditions and whichever extrapolation is chosen it eventually reaches things that cannot be explained, e.g. if the evolution had been cyclical, why it has reversed, or if the matter was hotter, why it was surrounded by an empty space, allowing expansion and adiabatic cooling, or if it was cooler either whence the extra energy came or what could have caused an adiabatic compression.
So my opinion is that for now any discussion about what could have happened before the moment of time when the temperature was in the range of tens of MeV and there were no other antiparticles besides positrons and antineutrinos and no other abundant hadrons except free protons and free neutrons is a waste of time, because being unverifiable any theory about that time is non-scientific, unless someone would discover a really new theory about the structure of matter, significantly better than anything that has been proposed during the last century, which could offer additional insight.
If we agree that everything we see is described by physics, then everything including us is simply a computation. And in principle someone can build a machine to carry out such a computation.
People in such a machine will be more or less like us, and the creator of that machine will be exactly like god, outside of space and time, omnipotent, omniscient but having to run the simulation to see what everyone does.
From this point of view creating universe 6000 years ago and making it look billions of years old does not look that insane, just a workaround for finite machine time.
So the main disagreement is not about existence of god, or materialism vs idealism, but whether a human is equivalent to a computation or not.
All of these situations are quite convoluted if you want to fit a designer in there.
But then I realized… whenever I create fake people for unit tests I give them names that correspond to what they do. Could this be a sign that the universe is a simulation? And, that God is just a QA running some tests on it?
So maybe we’re living in an edge case!
I had never heard of this before, and I find the idea absolutely delightful. As I understand it, the "knots" are stable vortices in the aether. It was popular from 1870 - 1890, and it blows my mind that only a few years later the electron was discovered (1897), and less than 50 years later (1938), the scanning electron microscope was invented! 1955 was when the atom was first imaged.
https://webhomes.maths.ed.ac.uk/~v1ranick/papers/mfaknot.pdf ("Geometry and Physics of Knots" by Atiyah)
It's interesting that the mathematical theory of knots was initially developed in response to Kelvin's proposal (i.e. Tait's work), because people were motivated trying to work out its implications for atomic theory. A branch of mathematics created by wrong physics.
A pure, single Gaussian hump is the soliton for homogenous linear media. If you create an audible with the spectral shape of a Gaussian (and therefore also the time shape), it might get quieter as it moves across the room, and longer, but will still "sound" the same.
Fun fact: it's very easy to rule out a multiverse theory where travel between universes is possible.
If the multiverse theory is correct, every possible combination of universe is out there. This means there is a universe which formed in exactly the right way such that the citizens all decided to leave their universe and invade our specific one. They formed 10 billion years ago and completely annihilated all matter in our universe.
Since we are still here, either the multiverse is false, or travel between universes is impossible.
Says who? There are an infinite number of real numbers that have only 1s and 0s in their decimal expansion.
Only the ones in which we all didn't get murdered are having this conversation.
This reminds me of Stephen Hawking telling John Oliver that the latter dating Charlize Theron is beyond the bounds of scientific possibility in any of the infinite parallel universes.
The key to why the universe exists may lie in an 1800s knot idea
When I first read the existing title I was also very confused
Edit: The mention of Kelvin's original idea does make the article more interesting though!