ask a physicist

[Umbran]

On the other hand, it is possible that some very heavy undiscovered particle and antiparticle decay differently into matter and antimatter. That can happen and can create the imbalance we need. Of course, we've not discovered such a particle yet.

Yes. I left this nuance off - the imbalance would arise in the time when very heavy and energetic particles were far more common - and one of those super-heavy particles could be the culprit that led to the very small imbalance in matter.

This is an interesting idea, though I confess I've not seen any work related to it. I also can't immediately think of a way to implement it, either, since, if it's just a "local" fluctuation, it would have to be created during inflation. Anyway, suffice it to say that I'm not sure if there's a way to get this to work off the top of my head.

The most intriguing idea I saw actually linked it to the inflation-multiverse concept discussed above. That regions of the universe fell out of the inflation mode, and into regions of universe we think of with "normal" rate of expansion *because* they had developed a predominance of matter or antimatter, by mere statistical variation. Regions where matter and antimatter were balanced continued in full inflation mode, giving rise to isolated "bubble" universes of one form of matter or the other, in a sea of vast inflationary universe.

I no longer have the math supporting this suggestion on hand. I'll see if I can find a reference.

 

[freyar]

The most intriguing idea I saw actually linked it to the inflation-multiverse concept discussed above. That regions of the universe fell out of the inflation mode, and into regions of universe we think of with "normal" rate of expansion *because* they had developed a predominance of matter or antimatter, by mere statistical variation. Regions where matter and antimatter were balanced continued in full inflation mode, giving rise to isolated "bubble" universes of one form of matter or the other, in a sea of vast inflationary universe.

I no longer have the math supporting this suggestion on hand. I'll see if I can find a reference.

If you can, that would be great. I've seen some possibilities including inflation but nothing credible that sounds quite like what you say or that uses the anthropic principle in a significant manner.

 

[freyar]

Well, this more-or-less answers my "why isn't the universe composed only of perfectly symmetrical spheres" question. It sounds like a pretty important physics question though: if the universe had/has an asymmetrical anomaly, what caused that anomaly???

I'd like to answer myself, and blame it on the quantum field, which was basically subatomic chaos, pure randomness, if my last reading was interpreted correctly. So...

1) How's quantum field theory coming along, and is the field(s) as chaotic as I've understood?
2) Could the quantum field exist before/during the big bang, and explain why the universe isn't spherically symmetrical?

and just for fun...

3) I've read that time isn't just some simple measurement that keeps going steadily forward. Does Time show up as a variable in current physics math, and how does it vary from the Time that we plug into high school math? Or getting-to-work-on-time math?

Umbran has already addressed the spherical symmetry issues quite well, so I'll just talk about the quantum field theory issue a bit.

One thing I'd like to make clear is that there's not just one "quantum field." Quantum field theory is the name for a framework in physics. This is like how quantum mechanics isn't a single theory (like the theory of the hydrogen atom is) but rather a set of rules that should apply to theories of physics. So when we say that the Standard Model of particle physics is "a" quantum field theory, we mean that it obeys the rules and framework of quantum field theory with a particular set of fields and interactions --- each field corresponds to a type of particle. In any case, this framework is going along very well, thank you. I mean that it's a well-developed framework with lots of very precise results and quite a few Nobel prizes. But most of the developments have been for theories where the interactions between fields are weak, so there is a lot of work right now in trying to understand principles that apply to quantum field theories with strong interactions.

It is true that, as in quantum mechanics (which quantum field theory is part of), the results of measurements are probabilistic. And, in quantum field theories, that applies even to measurements of empty space. So I don't know if I'd actually use the word "chaotic," but it is true that there's "quantum activity" even in empty space (virtual particles, etc). And we definitely don't understand it --- there is a quantum contribution to energy, which should show up as the energy of empty space (the vacuum). I've already talked about that in one of the answers here, but the thing is we certainly don't understand the value of that (though there are ideas).

Quantum fields (or maybe some quantum gravitational generalization) certainly existed back to the Big Bang (Singularity), except that in the true theory of quantum gravity, we don't expect there is actually a singularity at the Big Bang.

If you're interested in this stuff, I recommend the blog "Of Particular Significance" by Matthew Strassler. He has a number of articles up on "what is quantum field theory," including a nice introduction to fields and particles.

I think I'll come back to your question on time tomorrow.

 

[Scott DeWar]

I am going to fork this as I seem to have a few more questions

 

[freyar]

3) I've read that time isn't just some simple measurement that keeps going steadily forward. Does Time show up as a variable in current physics math, and how does it vary from the Time that we plug into high school math? Or getting-to-work-on-time math?

Well, getting to work on time and the time you'd use in high school physics are pretty well the same. The way we think of time in our daily lives and the way physicists did until Einstein is as an absolute quantity that passes at a fixed rate. But Einstein changed that. First, the theory of special relativity showed that time passes at different rates for objects moving with respect to each other. Generally, we don't move very fast, so this doesn't impact us much. But if, say in the future, future you wanted to do your daily commute from earth to mars in half an hour, you'd need to move at a significant fraction of the speed of light, and the amount of time that passes in the clock on your space ship would be noticeably different than the time that passes on a clock that stays on earth while you make your round trip. Then, the theory of general relativity says time is affected also by gravity. So, for example, for every one second measured by a clock on earth, a clock in space ticks a bit more than one second. The extreme example is that, while a clock on the event horizon of a black hole ticks one second, an infinite amount of time passes on a clock far away from the black hole.

This does have some practical impact. If you have a smart phone, it most likely has a GPS unit, which you might use to track your location. GPS works by figuring distances from a set of satellites orbiting earth, and it figures distances by finding the length of time a radio signal takes to travel from the satellites to your phone. That takes very accurate time-keeping, and it actually has to be accurate enough to notice both of those "time dilation" effects I just mentioned.

This "flexibility" in the behavior of time is a very important and fundamental part of gravitational physics. It also causes some complications in our calculations, though the details are a bit complex.

Of course, there are lots of other speculative theoretical ideas about the role of time in a quantum theory of gravity. A popular thought is that time (and space) is not really a fundamental concept but emerges from something else. So maybe time is just an approximate notion altogether.

 

[Scott DeWar]

The way we think of time . . .passes at a fixed rate. But Einstein changed that. First, the theory of special relativity showed that time passes at different rates for objects moving with respect to each other. . . . . Then, the theory of general relativity says time is affected also by gravity. So, for example, for every one second measured by a clock on earth, a clock in space ticks a bit more than one second. The extreme example is that, while a clock on the event horizon of a black hole ticks one second, an infinite amount of time passes on a clock far away from the black hole.

This does have some practical impact. If you have a smart phone, it most likely has a GPS unit, which you might use to track your location. GPS works by figuring distances from a set of satellites orbiting earth, and it figures distances by finding the length of time a radio signal takes to travel from the satellites to your phone. That takes very accurate time-keeping, and it actually has to be accurate enough to notice both of those "time dilation" effects I just mentioned.

This "flexibility" in the behavior of time is a very important and fundamental part of gravitational physics. It also causes some complications in our calculations, though the details are a bit complex.

Of course, there are lots of other speculative theoretical ideas about the role of time in a quantum theory of gravity. A popular thought is that time (and space) is not really a fundamental concept but emerges from something else. So maybe time is just an approximate notion altogether.

first, edits are for saving tie and space. [heh heh heh]

second, regarding the effects of gravity on tme

are you suggesting that perhaps the very gravity of 'big blue' earth can effectually alter the time it takes for a signal to traverse in a round trip, moving a velocity of 'C' from a gps to a satellite and back to the gps? if so, then would it be possible, but not necessarily plausible, that gravity has an affect on RF signals of any frequency? Is there a way to test this, olor has it already been tested?

 

[Scott DeWar]

The way we think of time . . .passes at a fixed rate. But Einstein changed that. First, the theory of special relativity showed that time passes at different rates for objects moving with respect to each other. . . . . Then, the theory of general relativity says time is affected also by gravity. So, for example, for every one second measured by a clock on earth, a clock in space ticks a bit more than one second. The extreme example is that, while a clock on the event horizon of a black hole ticks one second, an infinite amount of time passes on a clock far away from the black hole.

This does have some practical impact. If you have a smart phone, it most likely has a GPS unit, which you might use to track your location. GPS works by figuring distances from a set of satellites orbiting earth, and it figures distances by finding the length of time a radio signal takes to travel from the satellites to your phone. That takes very accurate time-keeping, and it actually has to be accurate enough to notice both of those "time dilation" effects I just mentioned.

This "flexibility" in the behavior of time is a very important and fundamental part of gravitational physics. It also causes some complications in our calculations, though the details are a bit complex.

Of course, there are lots of other speculative theoretical ideas about the role of time in a quantum theory of gravity. A popular thought is that time (and space) is not really a fundamental concept but emerges from something else. So maybe time is just an approximate notion altogether.

first, edits are for saving tie and space. [heh heh heh]

second, regarding the effects of gravity on tme

are you suggesting that perhaps the very gravity of 'big blue' earth can effectually alter the time it takes for a signal to traverse in a round trip, moving a velocity of 'C' from a gps to a satellite and back to the gps? if so, then would it be possible, but not necessarily plausible, that gravity has an affect on RF signals of any frequency? Is there a way to test this, or has it already been tested?

 

[Scott DeWar]

The way we think of time . . .passes at a fixed rate. But Einstein changed that. First, the theory of special relativity showed that time passes at different rates for objects moving with respect to each other. . . . . Then, the theory of general relativity says time is affected also by gravity. So, for example, for every one second measured by a clock on earth, a clock in space ticks a bit more than one second. The extreme example is that, while a clock on the event horizon of a black hole ticks one second, an infinite amount of time passes on a clock far away from the black hole. This does have some practical impact. If you have a smart phone, it most likely has a GPS unit, which you might use to track your location. GPS works by figuring distances from a set of satellites orbiting earth, and it figures distances by finding the length of time a radio signal takes to travel from the satellites to your phone. That takes very accurate time-keeping, and it actually has to be accurate enough to notice both of those "time dilation" effects I just mentioned. This "flexibility" in the behavior of time is a very important and fundamental part of gravitational physics. It also causes some complications in our calculations, though the details are a bit complex. Of course, there are lots of other speculative theoretical ideas about the role of time in a quantum theory of gravity. A popular thought is that time (and space) is not really a fundamental concept but emerges from something else. So maybe time is just an approximate notion altogether.

first, edits are for saving time and space. [heh heh heh]

second, regarding the effects of gravity on time are you suggesting that perhaps the very gravity of 'big blue' earth can effectually alter the time it takes for a signal to traverse in a round trip, moving a velocity of 'C' from a gps to a satellite and back to the gps?

if so, then would it be possible, but not necessarily plausible, that gravity has an affect on RF signals of any frequency? Is there a way to test this, or has it already been tested?

 

[AbdulAlhazred]

are you suggesting that perhaps the very gravity of 'big blue' earth can effectually alter the time it takes for a signal to traverse in a round trip, moving a velocity of 'C' from a gps to a satellite and back to the gps? if so, then would it be possible, but not necessarily plausible, that gravity has an affect on RF signals of any frequency? Is there a way to test this, olor has it already been tested?

Depends on what you mean by 'alter the time', from every frame of reference that photon always moves at the speed of light. However, a photon emitted by a GPS satellite will cover a different amount of distance and take a different amount of time to arrive at its destination on the surface from the viewpoint of the satellite and from that of the ground-based receiver.

Gravity does have an effect on ALL RF signals, it doppler-shifts them. A photon coming down to Earth will, relativistically, be received by a receiver with a slower clock, making its frequency appear higher, so it will be blue shifted. A classical interpretation would be that the photon gained energy, but classical pre-relativistic mechanics doesn't really have a way to deal with the fixed speed of light...

 

[Scott DeWar]

Depends on what you mean by 'alter the time', from every frame of reference that photon always moves at the speed of light. However, a photon emitted by a GPS satellite will cover a different amount of distance and take a different amount of time to arrive at its destination on the surface from the viewpoint of the satellite and from that of the ground-based receiver.

Gravity does have an effect on ALL RF signals, it doppler-shifts them. A photon coming down to Earth will, relativistically, be received by a receiver with a slower clock, making its frequency appear higher, so it will be blue shifted. A classical interpretation would be that the photon gained energy, but classical ore-relativistic mechanics doesn't really have a way to deal with the fixed speed of light...

as for Doppler shifts, I know of Doppler radar shifting for radio navigation of aircraft, I guess it works for gravity force as easily as magnetic.