I know matter can become energy by things like nuclear reactions or matter antimatter collisions.
So how did energy become matter after the big bang? I heard the energy ‘cooled off’ and became matter but two questions.
isn’t the universe adiabatic? if so there’s nowhere for the energy to go. is it more that the energy remained stable but the volume of the universe grew, resulting in less energy per cubic meter for example?
how does energy transition to matter? what kind of energy was there at first? there were no stars so I assume no photons. what energy existed and how does that energy become quarks and hydrogen atoms?
It’s not just a matter of energy per volume. The energy per volume of the Universe has decreased by a greater factor than the factor by which the volume has increased. Conservation of energy is a local property, not a global one.
Originally, most of the energy was in photons. You don’t need stars to have photons.
The big puzzle is how we ended up with the familiar sort of matter, with positive protons and negative electrons, without a corresponding amount of antimatter. There’s some handwaving about that, but nobody really knows the answer.
It seems some think this can be done in a laboratory:
Breit and Wheeler suggested that it should be possible to turn light into matter by smashing together only two particles of light (photons), to create an electron and a positron – the simplest method of turning light into matter ever predicted. The calculation was found to be theoretically sound but Breit and Wheeler said that they never expected anybody to physically demonstrate their prediction. It has never been observed in the laboratory and past experiments to test it have required the addition of massive high-energy particles.
The new research, published in Nature Photonics, shows for the first time how Breit and Wheeler’s theory could be proven in practice. This ‘photon-photon collider’, which would convert light directly into matter using technology that is already available, would be a new type of high-energy physics experiment. This experiment would recreate a process that was important in the first 100 seconds of the universe and that is also seen in gamma ray bursts, which are the biggest explosions in the universe and one of physics’ greatest unsolved mysteries. SOURCE
Even if you expect a 50:50 distribution you never really get an exact 50:50 distribution. Flip coins forever and you narrow in on that 50:50 but it is almost never exactly even. You will almost always have more heads than tails (or vice-versa).
Can the lack of antimatter be nothing more than the vast majority of stuff annihilating itself and the universe we have is what’s left because it was not a perfect 1:1 annihilation?
Also important to remember had the balance been the other way and we lived in an antimatter universe nothing changes. What we call antimatter now would be matter in that alternate universe. Just flip things around…it all works the same.
Ok so a wide range of follow up questions, and keep in mind I don’t understand physics well.
Why were the energy particles photons at the big bang? When you say photons do you mean photons in the visible light spectrum?
Is all energy in the universe electromagnetic? Is it all visible light, x rays, gamma rays, radio waves, etc, is all energy just waves along the electromagnetic spectrum?
Why would the energy at the big big be electromagnetic waves then?
If a photon has no mass, how does two photons colliding result in particles with mass like electrons?
If a proton has ~1800x the mass of an electron, does it take the equivalent of 1800 photons colliding to make 1 proton? How much energy does it take to make an up or down quark? Is the mass of a particle unrelated to how much energy it took to make the particle?
I’m still not sure how the universe cooled down when it started.
If the universe started as an area of uniform heat and energy in all directions, but now we live in a universe with very disperse pockets of energy (a sun may have a ton of energy, empty space very little) is that going against entropy where energy used to be dispersed and even across space, but is now concentrated into pockets?
Does that fact that particles are constantly being created and destroyed by their antimatter particles in any way related to how at the beginning there were expected to be equal amounts of matter and anti-matter? Where does the energy from all the particles constantly coming into being and being destroyed by their pair come from, or is it zero energy since they destroy each other?
Is there a know recipe book for how to make subatomic particles? Do physicists know how much energy or what kind of energy to make a down quark or a lepton or a boson?
Yes, it only takes a very slight asymmetry to end up with all matter or all antimatter. The problem is, nobody’s ever actually found that slight asymmetry. Every process that we’ve ever found that produces (say) protons and antiprotons, always produces exactly the same number of protons and antiprotons, to within the quite good limits that we’ve ever been able to measure.
does the edge of a black hole sometimes absorb the anti proton when a proton is created, creating an imbalance and hawking radiation?
I’ve heard one theory is our universe is in the black hole of another universe, is there a theory on how a black hole may create imbalances in atomic materials and their counterparts?
True; I shouldn’t have said every process. Hawking radiation makes no distinction between matter and antimatter, and so could randomly result in an imbalance. But so far as I know, nobody’s ever come up with a cosmological model that would use that to get the asymmetry that we see.
They weren’t. If you peel the onion back far enough, you get to where you need some form of potential energy that will, through quantum fluctuations that bump it out of a metastable state, decay to produce more normal stuff. That “bump” is the Big Bang, and the precursor energy is hypothesized to have come via the unstable “inflaton” field. Upon the transition out of that very early stage (10-32 seconds in), the universe was a hot, hot soup of basically everything.
It doesn’t actually make sense to talk about photons at this point because at the temperatures present many of your familiar particles – including photons – don’t exist. These temperatures are above a phase transition where the weak and electromagnetic forces are unified. The W boson, Z boson, and photon are not physical particles. There are different particles filling their roles. And before even that (at higher temperatures) it is hypothesized that the strong force is also unified with the electroweak force, so at that earlier point it wouldn’t make sense to talk about quarks and gluons either. Suffice it to say – it’s all a hot, hot soup of basically everything, but the everything is very different from today’s everything. I can dive into these weeds more as desired.
If you skip ahead to 10-12 seconds after the Big Bang, then you reach cool enough temperatures (1015 K) that a chart of the Standard Model particles becomes relevant. As the universe cools, it will continue to be a mix of all the particles that can freely be made and destroyed, subject to energy considerations (Is it hot enough that average particle energies are high enough to supply the mass of the things being made, like W or Higgs particles, say?) and subject to reaction rate considerations (e.g., Are things coming into contact fast enough given the ever decreasing density due to expansion of the universe?)
In time (roughly 10-10 s), you can’t spontaneously create heavy bosons anymore. A bit later, it’s too cold for hadrons to be created, so you are stuck with just the leftover stable ones (protons and, on these time scales, neutrons). Then it becomes too cold for neutrinos to do much, so they become free to stream on nearly forever. Then a very long time later (370,000 years) it’s too cold to maintain a plasma of electrons and protons and photons, so neutral hydrogen forms and the photons become free to stream on nearly forever. These last photons are the very same that make up today’s “cosmic microwave background radiation”.
The above hopefully suggests the answer – no. In the early universe, the energy would be a mix of the masses and kinetic energies of a zoo of particles.
The kinetic energy of colliding particles – photons or otherwise – can be converted into the mass of particles after the collision. (To be fully accurate: it’s not technically the kinetic energy that is relevant but rather a certain combination of kinetic energy and momentum.)
This sentence has somehow connected the mass of electrons with the number of photons. No such connection exists. To make (the mass of) a proton, you need at least that much energy coming into the system. Protons are a sort of complicated case, though, since they are made up of other particles and also since there are conservation laws related to baryons (which protons are the lightest type of).
The mass is directly related to how much energy it takes to make the particle.
Due to quantum fluctuations in the earliest moments, the density of the universe wasn’t perfectly uniform. Those nonuniformities were amplified over time thanks to gravity, and they were the seeds of the clumpy structure of matter we have today.
Yeah, it’s all well understood within the energy ranges accessible to experiment or to reasonable extrapolation beyond that using the underlying theory.
On the matter/antimatter asymmetry point…
There are certainly known processes that violate matter/antimatter symmetry, so it isn’t that they don’t exist. It’s that their rates in the early universe are expected to fall short of what’s needed. However, there are excellent candidate processes at very high energies that can fill the role. It is an experimental task to measure low-energy (accessible) processes that give a glimpse into the verity of those high-energy (inaccessible) processes.
Someone also asked somewhere whether just raw fluctuations could be enough. This can be worked out, and no, they are far, far off from enough.