Update on dark energy

MarkF
MarkF
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ChipperQ I don't have any

ChipperQ
I don't have any problem with your most recent post. It seems to be fairly standard except for:

Quote:
(summation of the 'stress energy tensor'?)


In field theories what happens at single point and instant is less important than how the components vary over space and time.

Chipper Q
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RE: I don't have any

Quote:
I don't have any problem with your most recent post. It seems to be fairly standard ...


Thanks, Mark.

Can I then extend this line of reasoning and say that such a region has a boundary that has no discernible instantaneous location at any point in time? That is, can I say that the boundary has no specific beginning/end to it? And if so, does this mean that the boundary maintains its integrity indefinitely? Or phrased another way, does this mean it's in a state of continuous resolution of events (with similar adjacent regions, and with anything happening to be propagating through the region, including GW and EM radiation)? If so, then might such regions be the virtual sea of particles that curve or warp in a gravitational field?

MarkF
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ChipperQ No, not exacty. As I

ChipperQ
No, not exacty. As I understand it you must always precisely define at least the value of each component at the boundries in all dimenstions and frequently the components first derivatives as well.

Chipper Q
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RE: As I understand it you

Quote:
As I understand it you must always precisely define at least the value of each component at the boundries in all dimenstions and frequently the components first derivatives as well.


Yes, to do meaningful calculations, right? But can I impose this same condition on nature, and conclude that spacetime is necessarily a discrete structure, packed with quantized regions of probabilities? I guess I'm proposing in part that nature has its own coordinate basis, and it's on this scale of Planck-sized spheres, in continuous resolution of propagating energies. I'm not suggesting that nature has to calculate anything; I'm saying that not even light passes through a single one of these regions instantaneously, and if the region is curved or warped in a gravitational field, then so also is the path of the light similarly skewed. It's a region where energy is curved or warped to an extent, at some threshold in the interaction, even into matter, and then transformed back to energy in some neighboring region. I realize it's tempting to think that laws of physics can be temporarily violated in such a region, and maybe they are, but what experiment has been performed at this scale that wasn't also being subjected to a shower of neutrinos and GW radiation (just to name a couple factors)?

MarkF
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ChipperQ This all seems ok to

ChipperQ
This all seems ok to me. I definitely would not presume to say how nature works or why it is the way it is. I simply try to find the best way to model it.

MarkF
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RE: I realize it's tempting

Quote:
I realize it's tempting to think that laws of physics can be temporarily violated in such a region, and maybe they are


Actually the events which create virtual particles do violate classical conservation laws (such as conservation of energy and momentum). The region of space-time over which this occurs is inversly proportional to the magnatude of the violation. Such violations are the reason QFT insists virtual particles are unobservable.

ECR
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You guys were having such an

Message 19757 in response to message 19756

You guys were having such an intelligent conversation and I hate to but in, especially 3 days after the last post. I am in no way in the same league as you all seem to be so forgive me for my simple question. Im not even sure if i should ask it here but you all seem like the types that can give me an intelligent answer.

Question: Is the speed of light constant or can it be influenced by gravity and/or mass? In other words, can it speed up/slow down as it passes a celestial body and then continue at its regular speed?

(Thanks for entertaining my question)

tullio
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RE: You guys were having

Message 19758 in response to message 19757

Quote:

You guys were having such an intelligent conversation and I hate to but in, especially 3 days after the last post. I am in no way in the same league as you all seem to be so forgive me for my simple question. Im not even sure if i should ask it here but you all seem like the types that can give me an intelligent answer.

Question: Is the speed of light constant or can it be influenced by gravity and/or mass? In other words, can it speed up/slow down as it passes a celestial body and then continue at its regular speed?

(Thanks for entertaining my question)


Afaik light can be deflected near a massive object, giving as result a gravitational lens, but its speed in a vacuum remains constant.
Tullio

MarkF
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ECR Ask questions and feel

ECR
Ask questions and feel free to challange the answers when ever the spirit moves you.
And expect to be challanged.

Chipper Q
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Mark, thanks again for your

Mark, thanks again for your help. Just found an article that echoes your answers when I've been able to frame my questions well enough, and it also covers a fair amount of additional aspects regarding GR and QM. I think it's the kind of overview of gravity I've been looking for, and hopefully everyone will find it interesting...
Testing the gravitational inverse-square law

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