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Do we actually know that the fields are infinite? I thought it was just the easiest way to model what we know and can observe.

by bdamm 3y ago

rapjr9 3y ago
I think the question would be, what happens at the edge of the universe? If the universe is finite, though expanding, then the waves can not be infinite unless they reflect at the edge, although one definition of the size of the universe might be that it extends as far as gravity and EM waves have traveled since the big bang. In which case I think the answer would be that if waves define fields then fields are not currently infinite nor will they ever be infinite, but they will always define the edge of the universe and keep traveling forever and over infinite time they will keep traveling infinitely. Which means they are essentially infinite, but not actually currently infinite, but that difference might not be much of a difference, even mathematically. It would suggest that EM radiation and gravity become more dilute in any one place over time though, as the universe gets bigger and the waves spread out more. There is also the speed of light problem. If EM radiation and gravity can only travel at the speed of light, then when new fields are created they do not propagate to infinity instantly, it takes time. So there is a kind of localness to EM/gravity but given the age of the universe a huge number of waves have propagated very far, which may be close enough to infinite we can't tell the difference. Matter can be created and destroyed so there can be new gravity fields created? Although I believe current thinking is that energy also exhibits gravity so maybe all the gravity that will ever exist is already here. That would be a difference in the nature of gravity versus EM waves since new EM radiation can be created while perhaps new gravity can not. Is a wave a perturbance that travels at the speed of light in a field that propagates instantly? Or is a field the propagation of a wave that travels at the speed of light? The idea of infinite fields suggests instant propagation, but gravity waves and EM waves certainly do not seem to propagate instantly. Maybe the idea of fields makes no sense and there are only waves?

Do we actually know that the fields are infinite? I thought it was just the easiest way to model what we know and can observe.

by bdamm 3y ago

Do we actually know that the fields are infinite? I thought it was just the easiest way to model what we know and can observe.

rapjr9 3y ago

I think the question would be, what happens at the edge of the universe? If the universe is finite, though expanding, then the waves can not be infinite unless they reflect at the edge, although one definition of the size of the universe might be that it extends as far as gravity and EM waves have traveled since the big bang. In which case I think the answer would be that if waves define fields then fields are not currently infinite nor will they ever be infinite, but they will always define the edge of the universe and keep traveling forever and over infinite time they will keep traveling infinitely. Which means they are essentially infinite, but not actually currently infinite, but that difference might not be much of a difference, even mathematically. It would suggest that EM radiation and gravity become more dilute in any one place over time though, as the universe gets bigger and the waves spread out more. There is also the speed of light problem. If EM radiation and gravity can only travel at the speed of light, then when new fields are created they do not propagate to infinity instantly, it takes time. So there is a kind of localness to EM/gravity but given the age of the universe a huge number of waves have propagated very far, which may be close enough to infinite we can't tell the difference. Matter can be created and destroyed so there can be new gravity fields created? Although I believe current thinking is that energy also exhibits gravity so maybe all the gravity that will ever exist is already here. That would be a difference in the nature of gravity versus EM waves since new EM radiation can be created while perhaps new gravity can not. Is a wave a perturbance that travels at the speed of light in a field that propagates instantly? Or is a field the propagation of a wave that travels at the speed of light? The idea of infinite fields suggests instant propagation, but gravity waves and EM waves certainly do not seem to propagate instantly. Maybe the idea of fields makes no sense and there are only waves?