- #1
Comradez
- 12
- 0
Hi all,
I was reading about the history of the early universe today, and there were some things that I did not understand. In particular, I do not understand the concept of "spontaneous symmetry breaking." After reading the Mexican Hat analogy many times, here is my best understanding of it:
At higher temperatures, certain physical processes have multiple possible outcomes. For example, imagine a Uranium-235 nucleus having an equal chance of decaying into two different kinds of nucleus (I know that this particular example is not real; this is just a metaphor). However, once the temperature of the early universe cooled to a certain level, certain physical processes (like the strong and weak forces) became more constrained(?) in how they operated, favoring one type of outcome over another in reaction to some stimulus whereas formerly both or multiple outcomes from that stimulus had been possible.
If that was the situation, then I could fathom it. I still wouldn't understand why exactly the stuff behaved differently at different details, but I'm familiar with other substances behaving differently at different temperatures (like water ice), so it would at least be fathomable. But so far, no presentations that I have watched or read have been able to bridge the gap between metaphors like the Mexican Hat one and a non-trivial explanation of spontaneous symmetry breaking that I can understand.
I understand the concept of a substance's *state* being asymmetrical. For example, if a column is sitting up straight, knocking it over to the right or left (i.e. displacing the position of the head of the column to the right or left) would be equally easy. However, if the column has already started falling over to the left, then suddenly the task of displacing the head of the column to the right or left is asymmetrical; pushing it further to the left is easier than arresting its fall to the left and pushing it to the right. However, to me this example seems to only pertain to the physical state of the system. The underlying forces or laws of motion themselves have not changed their operation or become asymmetrical.
What does it even mean to have several forces "coupled" together? What really happened when the strong force became "uncoupled" from the electroweak force, and please try to explain it like you would to a kindergartner, without math or reference to "gauge symmetries" (unless you can explain those to a kindergartner as well!) I'm looking for a physical metaphor, not a wall of math and symbols please. I have spent about six hours trying to understand what that SU(2)xU(1) stuff is all about, and it has gotten me nowhere! Lie groups? Manifolds? Lagrangians? I'm sorry...
In other words, I'm interested in the following questions:
1. What did matter "look like" during the electroweak epoch? (My guess is that matter would not have "looked like" anything in the electromagnetic spectrum because photons didn't exist yet. So, if "look" is the wrong question, then maybe I can ask: what forms did matter come in at that point? Was it a "quark-gluon plasma"? And, aside from this plasma being very hot and presumably wanting to stick to itself, were there any other notable characteristics of it?) What about even earlier, during the hypothesized "GUT" epoch? I ask these questions not just out of idle philosophizing, but because I am led to understand that our supercolliders are increasingly able to replicate, for short nanoseconds, these temperatures of the early universe, and thus these conditions are in principle reproducible and could have practical applications someday.
2. Did matter exert an attractive force on itself yet? My understanding is that gravity was already a separate force that existed, but apparently matter didn't have mass yet because matter wasn't yet being clamped onto by the Higgs field to give it mass...so presumably there was no tendency yet for the universe's ongoing expansion to decelerate yet even in the slightest due to the lack of matter having mass and thus being affected by gravity or inertia. (And if matter did not yet have inertia, then what was keeping matter from flying apart infinitely fast at that point?
I was reading about the history of the early universe today, and there were some things that I did not understand. In particular, I do not understand the concept of "spontaneous symmetry breaking." After reading the Mexican Hat analogy many times, here is my best understanding of it:
At higher temperatures, certain physical processes have multiple possible outcomes. For example, imagine a Uranium-235 nucleus having an equal chance of decaying into two different kinds of nucleus (I know that this particular example is not real; this is just a metaphor). However, once the temperature of the early universe cooled to a certain level, certain physical processes (like the strong and weak forces) became more constrained(?) in how they operated, favoring one type of outcome over another in reaction to some stimulus whereas formerly both or multiple outcomes from that stimulus had been possible.
If that was the situation, then I could fathom it. I still wouldn't understand why exactly the stuff behaved differently at different details, but I'm familiar with other substances behaving differently at different temperatures (like water ice), so it would at least be fathomable. But so far, no presentations that I have watched or read have been able to bridge the gap between metaphors like the Mexican Hat one and a non-trivial explanation of spontaneous symmetry breaking that I can understand.
I understand the concept of a substance's *state* being asymmetrical. For example, if a column is sitting up straight, knocking it over to the right or left (i.e. displacing the position of the head of the column to the right or left) would be equally easy. However, if the column has already started falling over to the left, then suddenly the task of displacing the head of the column to the right or left is asymmetrical; pushing it further to the left is easier than arresting its fall to the left and pushing it to the right. However, to me this example seems to only pertain to the physical state of the system. The underlying forces or laws of motion themselves have not changed their operation or become asymmetrical.
What does it even mean to have several forces "coupled" together? What really happened when the strong force became "uncoupled" from the electroweak force, and please try to explain it like you would to a kindergartner, without math or reference to "gauge symmetries" (unless you can explain those to a kindergartner as well!) I'm looking for a physical metaphor, not a wall of math and symbols please. I have spent about six hours trying to understand what that SU(2)xU(1) stuff is all about, and it has gotten me nowhere! Lie groups? Manifolds? Lagrangians? I'm sorry...
In other words, I'm interested in the following questions:
1. What did matter "look like" during the electroweak epoch? (My guess is that matter would not have "looked like" anything in the electromagnetic spectrum because photons didn't exist yet. So, if "look" is the wrong question, then maybe I can ask: what forms did matter come in at that point? Was it a "quark-gluon plasma"? And, aside from this plasma being very hot and presumably wanting to stick to itself, were there any other notable characteristics of it?) What about even earlier, during the hypothesized "GUT" epoch? I ask these questions not just out of idle philosophizing, but because I am led to understand that our supercolliders are increasingly able to replicate, for short nanoseconds, these temperatures of the early universe, and thus these conditions are in principle reproducible and could have practical applications someday.
2. Did matter exert an attractive force on itself yet? My understanding is that gravity was already a separate force that existed, but apparently matter didn't have mass yet because matter wasn't yet being clamped onto by the Higgs field to give it mass...so presumably there was no tendency yet for the universe's ongoing expansion to decelerate yet even in the slightest due to the lack of matter having mass and thus being affected by gravity or inertia. (And if matter did not yet have inertia, then what was keeping matter from flying apart infinitely fast at that point?