- #1
- 7
- 1
... and how were these then able to go on to form atoms?
In the beginning, how did elementary particles form?.........
- B
- Thread starter rogermunns
- Start date
- #2
DaveC426913
Gold Member
- 21,930
- 5,476
Wiki has a basic cosmological timeline of the universe from the 2nd picosecond:
https://en.wikipedia.org/wiki/Chronology_of_the_universe
Give a read, and see if you have any more specific questions.
https://en.wikipedia.org/wiki/Chronology_of_the_universe
Give a read, and see if you have any more specific questions.
- #3
Dale
Mentor
- 34,463
- 12,436
- #4
- 7
- 1
Reading that Wiki article was a bit like reading of the Theory of Evolution. Surely the first question is 'How did life start?' not 'What happened when life got going?'
Again, the question is 'How did elementary particles form? Words like <<Initially, various kinds of subatomic particles are formed in stages>> do not, frankly, cut it.
((I had not seen the second reply when I wrote this)).
Again, the question is 'How did elementary particles form? Words like <<Initially, various kinds of subatomic particles are formed in stages>> do not, frankly, cut it.
((I had not seen the second reply when I wrote this)).
- #5
- 7
- 1
Thanks, but the second reply goes no further than ignoring the question.
- #6
Dale
Mentor
- 34,463
- 12,436
Maybe try asking a better question then. As far as I can tell it is a complete answer to the questions asked
- #7
mathman
Science Advisor
- 8,140
- 571
The formation was in a series of steps. (1)Big bang - soup of photons, quarks, electrons, etc. (including antiparticles). (2) Quarks combine to form protons and neutrons, while pair production and annihilation continue. (3) During this phase light nucleons ##H_2,\ He_3,\ He_4,\ Li_6,\ Li_7## formed (mostly ##He_4##). Everything else was formed in stars .
Atoms formed about 300,000 years later when things coolled down enough.
Atoms formed about 300,000 years later when things coolled down enough.
- #8
vela
Staff Emeritus
Science Advisor
Homework Helper
Education Advisor
- 15,933
- 2,589
Dale pointed you to articles that directly address the question of yours he quoted.
What kind of answer would satisfy you?
- #9
Drakkith
Mentor
2022 Award
- 22,651
- 6,862
Even if we assume the universe has an actual beginning (something that is not known), or that it has some point in time where the very first particles came into existence, the unfortunate answer is that we don't know how these particles would have formed. We can make models back to the very early universe, but the problem is that our understanding of physics at the extreme energy and density scales of the very early universe is very incomplete. There is no known point in time where we can look back and say with confidence that nothing existed prior to this time. Even the big bang singularity isn't really thought to exist. Instead it is likely that the singularity is an artifact of our incomplete knowledge of physics and we cannot be certain that our current theories governing subatomic particles and their interactions are complete either.
And let me point out that your original question consisted of a single sentence with absolutely nothing to elaborate on the question, leaving everyone else here to try to figure out the specifics of what you were asking. It's a bit like asking, "Where do cars come from?" There are a huge number of ways to answer that question. They come from a dealership, they are built at a factory, they come from materials dug up from the ground, they come from elements formed in the cores of stars, etc.
Telling people that have voluntarily given you their time and effort, even if only a little of it, that their answers 'just don't cut it' and are 'ignoring the question' just makes you come across as a jerk.
- #10
- 7
- 1
I am sorry if I have 'come across' as a jerk. Of course. I think the problem is that I am an 'old' Physicist (1966 Hons. Phys. London). In those days we were taught about protons, neutrons, electrons, plus maybe a few vague ideas like quarks. I would call myself a practical Physicist, hence the (I thought quite precise) question 'In the beginning how did the elementary particles form?' The 'answers' I have been pointed to seem too theoretical.
Theoretical Physicists, bless them, have, IMHO, gone a long way to make Physics obscure for an averagely-intelligent person. I have only ever come across one Physicist - Feynman - who could speak to the masses in a way they could understand.
Perhaps I can ask the question again, slightly differently; how were atoms of hydrogen first formed? Maybe someone could just slip in a statement about how protons and electrons were formed before hydrogen atoms.
Theoretical Physicists, bless them, have, IMHO, gone a long way to make Physics obscure for an averagely-intelligent person. I have only ever come across one Physicist - Feynman - who could speak to the masses in a way they could understand.
Perhaps I can ask the question again, slightly differently; how were atoms of hydrogen first formed? Maybe someone could just slip in a statement about how protons and electrons were formed before hydrogen atoms.
- #11
Dale
Mentor
- 34,463
- 12,436
You were given precise answers. You didn’t specify anything about how how theoretical you wanted the answer, so there was no possible way for us to know that is what you wanted until now.
The first atoms of hydrogen formed when protons and electrons cooled down enough that they were slow enough that a proton could capture an electron.
- #12
Drakkith
Mentor
2022 Award
- 22,651
- 6,862
How could the answers be anything but 'theoretical'? We're talking about events that took place 13 billion years ago or more, and at energy scales that even the LHC can't reach yet. Despite this, they give remarkably good predictions about the composition and distribution of matter and radiation in the universe.
I don't know what you expect. The body of knowledge science has built up over the centuries is staggeringly massive and trying to connect different pieces together and phrase the explanation in a way that people without a background in science can understand is very difficult. There's a reason why there's only a handful of people widely known for their ability to explain science without simplifying it down to the point of being wrong.
Currently it is believed that hydrogen atoms were first formed during an event called 'recombination'. Prior to this point in time, the universe was far too hot for stable atoms to form and electrons, protons, helium nuclei, and a smattering of other nuclei existed together as a plasma. The expansion of the universe gradually cooled this plasma down until the temperature dropped far enough to allow the first atoms to form.
The origin of nuclei, nucleons, and electrons is earlier, but is intimately related to this plasma. Well before recombination the plasma was much hotter. So hot that subatomic particles and radiation underwent annihilation and creation events constantly. The hotter the plasma, the more energetic these particles and radiation was, and the more massive the particles created, leading to a population of massive but unstable particles. As the universe cooled off (more specifically the plasma filling the universe) less and less massive particles were formed and, combined with the decay of the more massive particles, this led to the universe being filled with only light, stable particles; protons, neutrons, electrons, and a few others. Once the temperature transitioned across this boundary the composition of the universe was essentially 'locked in' as the ratio of each particle to the others.
Here's a few wikipedia links:
https://en.wikipedia.org/wiki/Big_Bang_nucleosynthesis
https://en.wikipedia.org/wiki/Chronology_of_the_universe#Early_universe
- #13
Vanadium 50
Staff Emeritus
Science Advisor
Education Advisor
- 31,161
- 17,302
- #14
Dale
Mentor
- 34,463
- 12,436
Physics Forums is turning into Psychics Forum?I guess these days if you want to teach physics, you need to be a mind reader.
- #15
pinball1970
Gold Member
- 2,234
- 2,986
Theoretical physics IS obscure, counter intuitive and can’t be described in words, as a physics graduate from your 1966 finals, how many of you exam questions/answers were answered in words?
For QM and GR?
Pretty tough describing general relativity in words only and it the attempts I have read were entirely unsatisfying.
“Space tell mass how to move and mass tells space how to bend.” Does that really tell you anything?
Lots of wordy descriptions for the layman on virtual particles that turn out to be wrong because the words just don’t cut it.
Richard Feynman who you said was an exception described the atom like this, (paraphrase) “It is not like a star with orbiting planets it is not like a cloud of electrons encircling the nucleus it is like nothing you can imagine.”
I think that is a pretty unsatisfying explanation of something. What something isn’t.
Where the science/data/research stops (like at T=0) the perfectly good answer is, from what I have read on PF is “We don’t know.” (I am not one of the "we")
Or “We don’t know yet.” (I prefer that one)
- #16
- 7
- 1
Thank you all, I am satiated.
- #17
- 23,720
- 14,399
To the contrary! Theoretical physics is concerned with making physics simpler and easier to understand than a collection of empirical facts. You are right when you say that theoretical physics cannot be described by words, because the adequate language is mathematics, and accepting this and learning the actual mathematics you need to do modern physics provides great intuition about things far beyond our everyday experience, extending it into the realm of the very small (down to sub-atomic particle scales and up to huge scales of the entire universe).
Feynman was obviously an honest guy, much more honest than people who tell you you can understand physics by avoiding all mathematics, which is the only adequate language to formulate physics to begin with, and indeed if it comes to quantum physics there's no way to describe it in everyday pictures, because our everyday experience is indeed formed by interacting with macroscopic objects which behave according to the laws of classical physics, which however are indeed nothing else than a coarse-grained view of many-body quantum systems.
If you now look at a single atom, the coarse-grained picture is too coarse grained and the quantum description has to be used. Take a hydogen atom, consisting of a proton and an electron. Neither the proton nor the electron can be described as a classical particle in this case, but you have to use quantum theory to describe it. I do not agree with the last part of his sentence, because the hydrogen atom is among the few things we really can imagine to an astonishing degree of accuracy (the energy levels of hydrogen are indeed among the most accurately understood properties of any real-world system known today). It's right that it's not an imagination in intuitive every-day-experience terms but it's a very accurate imagination in mathematical terms of quantum theory.
- #18
ohwilleke
Gold Member
- 2,288
- 1,268
It is appropriate to note that Big Bang nucleosynthesis (how did atoms form from elementary particles) a.k.a. BBN is solidly consensus cosmology whose predictions, which are derived from plain vanilla nuclear physics observed on Earth with precision, are confirmed with only minor deviation from astronomy observations that themselves have hard to quantify error bars for systemic and theoretical error. BBN is almost as far back as clear consensus on all the details of cosmology goes. You can go back to the recombination of quarks and leptons out of a quark-gluon plasma that has not yet hadronized and into protons and neutrons and still remain on solid ground with a wide consensus. You can even go back to electroweak symmetry breaking from one trillionth of a second after the Big Bang to one millionth of a second after the Big Bang. Temperatures in this consensus part of the time line are more than 100 MeV but much less than the 10 TeV needed to give rise to Standard Model sphaleron processes.
But, before that, as you get closer to the Big Bang, there is controversy and lack of consensus. This line is roughly around 10−12 to 10-11 seconds after the Big Bang in the standard cosmology timeline. It's not bad to be quite sure about pretty much everything that happened in the 13.8 billion years history of the universe, except the first trillionth of a second or so of creation. But, the very first little bit is beyond the range of what our well established physical laws can explain.
Unlike BBN, baryogenesis and leptogenesis require beyond the Standard Model physics (upon which there is not a consensus) and wild speculation. There is no consensus on how this happened, even though there is consensus that it had to happen prior to BBN. "When" these things happened turns out to be a much easier to answer question than "how" these things happened.
The only Standard Model process which theoretically could be involved is the sphaleron process (which in theory can violate baryon number and lepton number conservation, but have never been observed), but that process only operates at temperatures in excess of about 10 TeV. But, the universe shouldn't have been at temperatures that high for a long enough time period to produce the particle content of the universe that we see today without beyond the Standard Model physics (if as most cosmologists assume simply because it is a beautiful assumption, the Big Bang started from a pure energy state, rather than one with non-zero baryon number or lepton number). As Wikipedia explains (without explicitly stating the pure energy at time zero assumption):
The truth of the matter is that we (meaning mainstream physics) really have no idea how baryogenesis and leptogenesis happened, and there are many competing theories, none of which has widespread support in the community of the relevant subfields of physics.
Similarly, while there is widespread support among cosmologists for cosmological inflation as a general paradigm, there are many hundreds of variations on inflation theory, many of which were wiped out by the most recent Planck cosmic microwave background observations, but many of which are still viable theories that are in the running.
Last edited: