What determined the amounts of hydrogen and helium that were created in the early phase of the Big Bang?
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I think we’d need to know exactly what dark matter was to determine what caused the amount of hydrogen created, which we dont.
The hydrogen was somehow drawn by the gravitational field created by dark matter make the clumps/clouds more and more dense, thus creating helium and the denser these clusters became still, the first stars where created.
In short, nobody knows until we figure out dark matter. Not scientist, but this is the best ELI5 I could come up with, with my limited knowledge on the subject.
I think we’d need to know exactly what dark matter was to determine what caused the amount of hydrogen created, which we dont.
The hydrogen was somehow drawn by the gravitational field created by dark matter make the clumps/clouds more and more dense, thus creating helium and the denser these clusters became still, the first stars where created.
In short, nobody knows until we figure out dark matter. Not scientist, but this is the best ELI5 I could come up with, with my limited knowledge on the subject.
I think we’d need to know exactly what dark matter was to determine what caused the amount of hydrogen created, which we dont.
The hydrogen was somehow drawn by the gravitational field created by dark matter make the clumps/clouds more and more dense, thus creating helium and the denser these clusters became still, the first stars where created.
In short, nobody knows until we figure out dark matter. Not scientist, but this is the best ELI5 I could come up with, with my limited knowledge on the subject.
The key factor is the neutron-proton ratio. In the first second after the Big Bang, the temperature was high enough that protons could convert to neutrons, and vice versa, by reacting with electrons, positrons, and neutrinos, and within this first second, this equilibrium kept the numbers of protons and neutrons about the same. However, as the Universe expands, it cools, and when the temperature drops, this equilibrium changes, and the neutron to proton reaction becomes dominant, because the proton has a slightly lower mass than the neutron. Free neutrons will also decay spontaneously into protons, but this has a half-life of about 15 minutes, and things are still hot enough that a lot can happen in that time. After that first second, you end up with about a 1:6 ratio of neutrons to protons.
To start forming helium, it’s first required that you have deuterium. Two deuterium nuclei can fuse to make a helium nucleus, but this can’t happen yet, because it’s still too hot. Any deuterium nuclei that forms at this point will just be destroyed by all the high energy photons whizzing around the place. It takes about 20 seconds after the Big Bang for things to cool down enough that deuterium nuclei can exist, and then nucleosynthesis can begin. We’ve got a roughly 1:6 ratio of neutrons to protons, so 2 neutrons for every 12 protons. If every neutron wound up inside a helium nucleus, then, we’d end up with 1 helium nucleus (remember that’s 2 protons and 2 neutrons) and then the other 10 protons are left to their own devices, so one helium nucleus per 14 overall nucleons.
However, not every neutron will end up inside a helium nucleus; some will spontaneously decay into protons first, some will fuse into deuterium nuclei but then those deuterium nuclei will fail to fuse into helium nuclei themselves, and a very small percentage of them will actually wind up going beyond helium and ending up inside lithium nuclei. These effects mean that overall it takes about 16 nucleons (2 neutrons and 14 protons) to form one helium nucleus, giving 12 protons (or hydrogen nuclei) for every helium nucleus. After about 20 minutes, the Universe has cooled to the point that fusion is no longer possible, and any neutrons left over will decay into protons.
That gives the overall proportions of hydrogen and helium as being about 12 hydrogen atoms for every helium atom, or about 92% hydrogen to 8% helium. Since a helium atom is 4 times heavier than a hydrogen atom, this gives a mass ratio of 25% helium to 75% hydrogen.
The key factor is the neutron-proton ratio. In the first second after the Big Bang, the temperature was high enough that protons could convert to neutrons, and vice versa, by reacting with electrons, positrons, and neutrinos, and within this first second, this equilibrium kept the numbers of protons and neutrons about the same. However, as the Universe expands, it cools, and when the temperature drops, this equilibrium changes, and the neutron to proton reaction becomes dominant, because the proton has a slightly lower mass than the neutron. Free neutrons will also decay spontaneously into protons, but this has a half-life of about 15 minutes, and things are still hot enough that a lot can happen in that time. After that first second, you end up with about a 1:6 ratio of neutrons to protons.
To start forming helium, it’s first required that you have deuterium. Two deuterium nuclei can fuse to make a helium nucleus, but this can’t happen yet, because it’s still too hot. Any deuterium nuclei that forms at this point will just be destroyed by all the high energy photons whizzing around the place. It takes about 20 seconds after the Big Bang for things to cool down enough that deuterium nuclei can exist, and then nucleosynthesis can begin. We’ve got a roughly 1:6 ratio of neutrons to protons, so 2 neutrons for every 12 protons. If every neutron wound up inside a helium nucleus, then, we’d end up with 1 helium nucleus (remember that’s 2 protons and 2 neutrons) and then the other 10 protons are left to their own devices, so one helium nucleus per 14 overall nucleons.
However, not every neutron will end up inside a helium nucleus; some will spontaneously decay into protons first, some will fuse into deuterium nuclei but then those deuterium nuclei will fail to fuse into helium nuclei themselves, and a very small percentage of them will actually wind up going beyond helium and ending up inside lithium nuclei. These effects mean that overall it takes about 16 nucleons (2 neutrons and 14 protons) to form one helium nucleus, giving 12 protons (or hydrogen nuclei) for every helium nucleus. After about 20 minutes, the Universe has cooled to the point that fusion is no longer possible, and any neutrons left over will decay into protons.
That gives the overall proportions of hydrogen and helium as being about 12 hydrogen atoms for every helium atom, or about 92% hydrogen to 8% helium. Since a helium atom is 4 times heavier than a hydrogen atom, this gives a mass ratio of 25% helium to 75% hydrogen.
The key factor is the neutron-proton ratio. In the first second after the Big Bang, the temperature was high enough that protons could convert to neutrons, and vice versa, by reacting with electrons, positrons, and neutrinos, and within this first second, this equilibrium kept the numbers of protons and neutrons about the same. However, as the Universe expands, it cools, and when the temperature drops, this equilibrium changes, and the neutron to proton reaction becomes dominant, because the proton has a slightly lower mass than the neutron. Free neutrons will also decay spontaneously into protons, but this has a half-life of about 15 minutes, and things are still hot enough that a lot can happen in that time. After that first second, you end up with about a 1:6 ratio of neutrons to protons.
To start forming helium, it’s first required that you have deuterium. Two deuterium nuclei can fuse to make a helium nucleus, but this can’t happen yet, because it’s still too hot. Any deuterium nuclei that forms at this point will just be destroyed by all the high energy photons whizzing around the place. It takes about 20 seconds after the Big Bang for things to cool down enough that deuterium nuclei can exist, and then nucleosynthesis can begin. We’ve got a roughly 1:6 ratio of neutrons to protons, so 2 neutrons for every 12 protons. If every neutron wound up inside a helium nucleus, then, we’d end up with 1 helium nucleus (remember that’s 2 protons and 2 neutrons) and then the other 10 protons are left to their own devices, so one helium nucleus per 14 overall nucleons.
However, not every neutron will end up inside a helium nucleus; some will spontaneously decay into protons first, some will fuse into deuterium nuclei but then those deuterium nuclei will fail to fuse into helium nuclei themselves, and a very small percentage of them will actually wind up going beyond helium and ending up inside lithium nuclei. These effects mean that overall it takes about 16 nucleons (2 neutrons and 14 protons) to form one helium nucleus, giving 12 protons (or hydrogen nuclei) for every helium nucleus. After about 20 minutes, the Universe has cooled to the point that fusion is no longer possible, and any neutrons left over will decay into protons.
That gives the overall proportions of hydrogen and helium as being about 12 hydrogen atoms for every helium atom, or about 92% hydrogen to 8% helium. Since a helium atom is 4 times heavier than a hydrogen atom, this gives a mass ratio of 25% helium to 75% hydrogen.
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