Don't even know which question to ask first

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37 replies · 5K views
GreatBigBore said:
Ok, but "out to the limits of our vision" brings me back to the question: what do we think might be there, or what might I experience if I tried to get "there"?
We would arrive back at our departure point.
 
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GreatBigBore said:
Ok, but "out to the limits of our vision" brings me back to the question: what do we think might be there, or what might I experience if I tried to get "there"? I don't mean unicorns. I mean what are the things being considered plausible by the larger community?
Different low-energy laws of physics.

Let's see if I can explain this. Basically, in our current physical theories, there are certain symmetries that are respected at high energies, but at low energies are broken.

One way that this is often illustrated is this: imagine that you have a large field of pencils, all evenly spaced. Once end of each pencil is anchored in the ground, and the pencil is free to move around. Now, we're also going to connected the other ends of the pencils with springs to one another, so the nearby pencils will tend to want to be in the same direction.

What happens at high temperatures for such a configuration is that these springs have a lot of random energy, so the pencils are bouncing around every which direction: the system as a whole has no preferred direction.

But as you lower the temperature, the pencils start to fall. And when they do start to fall, the neighboring pencils all want to fall in the same direction. So the pencils in one region may fall and point east. The pencils in another region may fall and point northwest. And so on. The size of the regions of the pencils pointing in anyone direction will depend upon how rapidly they froze.

We expect that with our current theories, there are direct analogs of this process that went on: fields that want to take on the same value at neighboring points in space, but don't care (much) what value that is. And things like the strengths of forces and masses of fundamental particles may depend critically upon the particular value of this field.
 
DaveC426913 said:
We would arrive back at our departure point.

And your basis for this is?

DaveC426913 said:
And the sign said / Anybody caught trespassin' / Will be shot on sight.
So I jumped on the fence / And I yelled at the house / "Hey! What gives y* -=>BLAM<=-
*thud*
(Dude! Didn't you see the sign? Jeez!)

Oh. Dude. I can't stop laughing.
 
Chalnoth said:
Let's see if I can explain this.

You have a fan. Thanks. Could you name a book or two along these lines? Or a URL?
 
GreatBigBore said:
You have a fan. Thanks. Could you name a book or two along these lines? Or a URL?
Well, this is mostly information I remember from classes, and I'm not entirely sure I want to suggest our textbook. But the phenomenon I described is known as "spontaneous symmetry breaking." The linked Wikipedia article will get you some more in-depth information. This sort of phenomenon is seen in all sorts of physical systems here on Earth, and seems to be an integral component of the standard model of particle physics (for electroweak symmetry breaking).

Also, spontaneous symmetry breaking has another interesting aspect: depending upon the dimensionality of the space, you tend to get what are called defects. For the pencil example above, for instance, a stable configuration is one where one pencil is standing up on end, and the neighboring pencils are all pointing away from that one. This "defect" would manifest itself as a point of very high energy.

For three dimensional space, a similar thing happens, but due to the extra dimension, instead of a point, you have a string: a long region where the field takes on a high-energy value and isn't allowed to "fall" due to the neighboring field values. These are called cosmic strings, and so far we haven't yet detected any. We know now that they must be quite rare, but the search for such direct signatures of spontaneous symmetry breaking is ongoing.
 
Chalnoth said:
Different low-energy laws of physics.

Wait a second. The low-energy laws of physics is *us* isn't it? I mean, the laws that govern our everyday lives?
 
GreatBigBore said:
Wait a second. The low-energy laws of physics is *us* isn't it? I mean, the laws that govern our everyday lives?
Yup, precisely. So it's conceivable, for instance, that a different region far away could have different decay rates for radioactive atoms, perhaps a different strength of the electromagnetic force. Stuff like that.
 
GreatBigBore said:
DaveC426913 said:
GreatBigBore said:
Ok, but "out to the limits of our vision" brings me back to the question: what do we think might be there, or what might I experience if I tried to get "there"?
We would arrive back at our departure point.
And your basis for this is?
If the universe is curved and closed, it may be in the form of a 4-dimensional spheroid. Just like on a 3-dimensional sphere, if you head in one direction long enough, you will arrive back at your starting point.