All Questions
Tagged with cosmology special-relativity
128
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Are the optical medium of 10.1007/BF00758153 and the Lorentz Ether of 10.1007/s00006-011-0303-7 the same thing? [closed]
On the gravitational field acting as an optical medium
A Generalization of the Lorentz Ether to Gravity with General-Relativistic Limit
The first paper seems to be facing a question: whether there ...
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1
answer
185
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Somewhat silly special relativity and cosmology thought experiment [closed]
Edit: I have already tried to delete this several times. I have already posted that I would delete this if I could and it was deleted. I have three very legitimate masters degrees in physics and more ...
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1
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Is the equation of state of the cosmological vacuum $P=-(1/3)\rho$?
I understand that the equation of state of the vacuum is assumed to be $P = -\rho$ due to the Lorentz invariance of its stress-energy tensor. But this argument assumes flat spacetime. We know at ...
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Expansion of the universe and superluminal speeds - an analogy
To illustrate, let's imagine the whole universe having a coordinate grid. Essentially a great big mesh grid of interlocking meter sticks.
Now... Einstein's theory of relativity tells us that nothing ...
- 41
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3
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One-Way Speed of Light and the Big Bang
Variations on this question have been asked a few times (e.g. here, here, and a few YouTube videos here and here). The claim seems to be that because we can only measure the round-trip speed of light, ...
- 106
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2
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Why does the light intensity of stars distribute almost uniformly across the night sky, if earth is not special?
According to special relativity, the direction of light should change when a reference frame is moving at near-light speed. There was a question on stack exchange about this topic before: Light in ...
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What exists in the world according to the special relativity? [closed]
Before I learned about special relativity, I thought that only one 3-dimensional state of the world exists. Then, like in game of chess, in one "turn" previous state is destroyed - and the ...
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2
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130
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The twin paradox in a Finite Dark energy less universe
Let's imagine we have a universe that is finite and curves back on iself. So if you go far enough in one direction you end up back where you started. (e.g. 3-Sphere/3-torus) Then lets imagine that it ...
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Does strongly gravitating object travel along geodesic of a background field？ [closed]
That test particles travel along the geodesic is assumed in the context of GR. But does it apply to strongly gravitating object, such as black hole in an expanding universe, binary neutron star, etc.? ...
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Are cosmological Black Holes superluminal FTL phenomena? [closed]
What does it mean, "gravity is so strong that not even light can escape from a BH..."?
This can physically interpreted IMHO that beyond the event horizon of the BH, light is phase ...
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Is it important to understand the concept of a universal 'now'? [closed]
Is it important to understand the concept of a universal 'now', to explain that time is a local phenomenon, and the rate of time varies throughout the universe, always dependent on the local ...
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Could inhomogeneties and/or topological defects break the fundamental symmetries of the universe?
I have heard that some types of inhomogeneties and topological defects (like cosmic strings) in cosmology have been proposed to be able to break fundamental symmetries of nature such as the Poincaré, ...
- 2,466
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2
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97
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Mass matter, energy and "massless matter"
This is perhaps a rather silly question, or rather a matter of convention, but I would like to hear arguments about the appropriateness of certain definitions.
Traditionally, in chemistry and in pre-...
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How to include the effect of cosmological expansion in the close to speed of light calculations of a relativistic rocket?
I calculated time ago as undergraduated and post it at my blog the calculations for traveling through the Universe in a (special) relativist way. At what level and how should we include the effect of ...
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How to rule out that the speed of light was different in the past?
The constancy of the speed of light is a fundamental principle in modern physics, and it is supported by a wide range of current experimental evidence.
There is no evidence to suggest that the speed ...
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