Number of Particles in Universe: Protons, Neutrons, Electrons

In summary, the conversation discusses the number of atoms in the universe, the balance of protons and electrons, and the creation of electrons and protons during baryogenesis. It also touches on the process of how the sun and stars get their energy through nuclear reactions. The concept of electrically balanced universe is also mentioned.
  • #1
Stephanus
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Dear PF Forum,
I'm just curious about these things.
From what I read, the number of atoms in the universe is 1080 Hydrogen atoms.
And neutrino is a billion times more. 1.2 x 1089
But what it said is actually the number of protons + neutrons, right?
And about this. Is the number of protons and eclectrons in the universe balanced.
If yes, why?
Protons and neutrons, they both are created in Baryongenesis, what about electron? When were they created?
Leptogenesis they say, but it's hipothetical, right?
 
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  • #2
Stephanus said:
what it said is actually the number of protons + neutrons, right?

Basically, yes; it's the number of baryons, of which the only significant ones are protons and neutrons (the other baryons are all unstable and decay eventually into protons and neutrons anyway).

Stephanus said:
Is the number of protons and eclectrons in the universe balanced.
If yes, why?

It probably is, yes, because the universe as a whole is expected to be electrically neutral, and the only significant charged particles are protons and electrons (all other charged particles in the Standard Model are either unstable or they are antimatter and therefore extremely rare).

Stephanus said:
what about electron? When were they created?

At the end of inflation, when the energy stored in the inflaton field was transferred to energy contained in the various Standard Model particles. That would have included both matter and antimatter particles (so electrons and positrons, quarks and antiquarks, neutrinos and antineutrinos, etc.). Later on, as the universe cooled, the matter and antimatter particles annihilated each other, leaving behind a lot of photons and a small excess of matter particles.
 
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  • #3
Stephanus said:
Dear PF Forum,
I'm just curious about these things.
From what I read, the number of atoms in the universe is 1080 Hydrogen atoms.
And neutrino is a billion times more. 1.2 x 1089
But what it said is actually the number of protons + neutrons, right?
At this level of accuracy, it doesn't matter. About 75% of the matter in our universe is Hydrogen, 25% Helium. The remainder that are heavier elements are so few that we can safely ignore them.

In this situation, the hydrogen atoms have a single proton, while the Helium atoms have two protons and two neutrons. If the total number of hydrogen atoms is exactly ##10^{80}##, then the total number of helium atoms is about ##3.3 \times 10^{79}##, which makes for about ##1.3 \times 10^{80}## nucleons (protons and neutrons) in all Helium atoms, for a total of ##2.3 \times 10^{80}## nucleons. That's such a tiny fraction of the neutrino number count that it's pretty much irrelevant when compared against neutrinos.

Electrons have been around since the end of inflation. So have the quarks that make up protons and neutrons. Baryogenesis didn't create the protons/neutrons, but it did create an imbalance between matter and anti-matter. Due to the conservation of electric charge, the imbalance in the number of protons had to be balanced by an equal number of negatively-charged particles. The only negatively-charged particles that are in the standard model and also stable are anti-protons and electrons. But we just said that we've got an imbalance between matter and anti-matter, so anti-protons can't fit the bill, leaving only electrons to retain conservation of charge for the protons.
 
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  • #4
PeterDonis said:
It probably is, yes, because the universe as a whole is expected to be electrically neutral, and the only significant charged particles are protons and electrons (all other charged particles in the Standard Model are either unstable or they are antimatter and therefore extremely rare).

But electrons weren't created at the same time as protons or were they?
If they weren't created at the same time as protons, how the universe "knows" to create the same amount of electrons to at least match protons?
Thanks for any answers.
 
  • #5
Stephanus said:
But electrons weren't created at the same time as protons or were they?

They were created at the same time as quarks. The temperature was too high at that point for quarks to be bound into protons.
 
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  • #6
Stephanus said:
But electrons weren't created at the same time as protons or were they?
If they weren't created at the same time as protons, how the universe "knows" to create the same amount of electrons to at least match protons?
Thanks for any answers.
Charge is conserved, so any process that created a positively-charged particle would necessarily create a negatively-charged particle. The total charge had to remain zero throughout, and electrons and protons are the only stable charged particles (aside from their anti-matter twins).
 
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  • #7
Thank you, thank you for the answers.
Actually I want to know how the sun (and the stars) gets its energy.

If it's proton to proton reaction chain, then...

[itex]{^{1}_{1}H} + {^{1}_{1}H} = {^{1}_{2}D} + p^+[/itex]
[itex]{^{1}_{2}D} + {^{1}_{1}H} = {^{2}_{3}He}[/itex]
[itex]{^{2}_{3}He} + {^{2}_{3}He} = {^{2}_{4}He} + 2{^{1}_{1}H}[/itex]
This reaction seems involve 6 Hydrogens atom. And 6 electrons?
And the result only have 4 electrons?
This belongs to other thread I guess

And the result if neutrally charged only have 4 electrons?
But I'd like to know first before I learn nuclear reaction.
Is the universe (approximately) neutrally balance?
Okay..., I'd like to study your answers first.
Thanks.
 
  • #8
Stephanus said:
Thank you, thank you for the answers.
Actually I want to know how the sun (and the stars) gets its energy.

If it's proton to proton reaction chain, then...

[itex]{^{1}_{1}H} + {^{1}_{1}H} = {^{1}_{2}D} + p^+[/itex]
[itex]{^{1}_{2}D} + {^{1}_{1}H} = {^{2}_{3}He}[/itex]
[itex]{^{2}_{3}He} + {^{2}_{3}He} = {^{2}_{4}He} + 2{^{1}_{1}H}[/itex]
This reaction seems involve 6 Hydrogens atom. And 6 electrons?
And the result only have 4 electrons?
This belongs to other thread I guess

And the result if neutrally charged only have 4 electrons?
But I'd like to know first before I learn nuclear reaction.
Is the universe (approximately) neutrally balance?
Okay..., I'd like to study your answers first.
Thanks.
There's a reaction where a proton and electron can combine to form a neutron and a couple of neutrinos. In this reaction, the helium atom has two neutrons in addition to its two protons.
 
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  • #9
Chalnoth said:
...Baryogenesis didn't create the protons/neutrons, but it did create an imbalance between matter and anti-matter...

Thanks Chalnoth for you invaluable answer. It's not the matter anti-matter balance that I want to know. It's the electrically balance that I want to kno.
Thanks.
 
  • #10
Chalnoth said:
There's a reaction where a proton and electron can combine to form a neutron...
Ahh, of course. How foolish I am!
 
  • #11
Also an addition to the chain you wrote down...
There are no electrons shown in those reactions, but nuclei... The circumstances where these reactions occur don't allow for atoms to exist, instead you are having a plasma state (ionized elements). Rephrasing: the electrons and nuclei are free.
 
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  • #12
And H+H-> D+p doesn't make much sense.
 
  • #13
ChrisVer said:
...instead you are having a plasma state (ionized elements)...
Double foolish I am!. Forgot that also!
Okay..., nucleus' and electrons are free roaming. But the universe is somewhat electrically charge balance, right?
 
  • #14
ChrisVer said:
And H+H-> D+p doesn't make much sense.
But, that's what Wikipedia says
FusionintheSun.jpg
 
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  • #16
Stephanus said:
But the universe is somewhat electrically charge balance, right?

Check post#2, stating that probably it is neutral... altough I'm not sure why would that be the case, and I don't know of anyway we'd measure the charge of the universe.

If you want to see the charge conservation (since it's conserved) then the electrons are free around and they meet a positron (which I mistook as a proton with that notation as Chalnoth said) coming from the 1st line and annihilate.
 
  • #17
During inflation, the universe becomes almost completely empty, to the point that maybe one particle from the pre-inflationary regime made it into our observable universe.

All of the particles that we see around us were produced at the end of inflation, and the net charge of those particles had to be zero. There will be some tiny differences due to the fact that our universe is finite in extent, so that some of the matter/anti-matter particle pairs created in the very early universe may have become separated with only one member of the pair within our observable universe. But this number is going to be so small that it can be safely ignored.
 

FAQ: Number of Particles in Universe: Protons, Neutrons, Electrons

1. How many protons are estimated to exist in the universe?

The estimated number of protons in the observable universe is approximately 1080, which is a very large number.

2. What about neutrons and electrons?

It is believed that there are roughly equal numbers of neutrons and protons in the universe, so the estimated number of neutrons is also around 1080. The number of electrons is thought to be slightly lower at around 1079, due to the presence of positively charged particles such as protons and ions.

3. How do scientists calculate the number of particles in the universe?

Scientists use various methods and data, such as observations of the cosmic microwave background radiation and the density of matter in the universe, to estimate the number of particles in the universe. The estimates are based on mathematical models and assumptions about the composition and evolution of the universe.

4. Are there any other particles besides protons, neutrons, and electrons in the universe?

Yes, there are other particles in the universe, such as photons (particles of light), neutrinos, and various types of subatomic particles. However, they are not as numerous as protons, neutrons, and electrons and may not contribute significantly to the overall number of particles in the universe.

5. Can the number of particles in the universe change?

The number of particles in the universe is not constant, as particles can be created or destroyed in various processes such as nuclear reactions or particle collisions. However, the total number of particles is thought to remain relatively stable over time due to the conservation of matter and energy.

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