Questions tagged [spacetime]
Within relativity (both special and general), changes of reference frames can change both the notions of space and of time, with one depending on the other as well. As a consequence, it is necessary to treat both concepts in a unified manner. Hence the term spacetime.
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Is 3+1 spacetime as privileged as is claimed?
I've often heard the argument that having 3 spatial dimensions is very special. Such arguments are invariably based on certain assumptions that do not appear to be justifiable at all, at least to me. ...
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Is spacetime discrete or continuous?
Is the spacetime continuous or discrete?
Or better, is the 4-dimensional spacetime of general-relativity discrete or continuous? What if we consider additional dimensions like string theory ...
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Is spacetime flat inside a spherical shell?
In a perfectly symmetrical spherical hollow shell, there is a null net gravitational force according to Newton, since in his theory the force is exactly inversely proportional to the square of the ...
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Do photons bend spacetime or not?
I have read this question:
Electromagnetic gravity
where Safesphere says in a comment:
Actually, photons themselves don't bend spacetime. Intuitively, this is because photons can't emit ...
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Does the universe have a center? [duplicate]
If the big bang was the birth of everything, and the big bang was an event in the sense that it had a location and a time (time 0), wouldn't that mean that our universe has a center?
Where was the ...
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Is spacetime wholly a mathematical construct and not a real thing? [closed]
Speaking of what I understood, spacetime is three dimensions of space and one of time. Now, if we look at general relativity, spacetime is generally reckoned as a 'fabric'. So my question is, whether ...
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Why should the Planck constant be a constant throughout all space?
Our value for the Planck constant $h$ can be found on experiments on Earth, but how do we know that the Planck constant doesn't change throughout space, for instance it depends weakly upon the ...
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GR and my journey to the centre of the Earth
[General Relativity] basically says that the reason you are sticking to the floor right now is that the shortest distance between today and tomorrow is through the center of the Earth.
I love ...
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What is a Lorentz boost and how to calculate it?
I know very little about special relativity. I never learnt it properly, but every time I read someone saying
If you boost in the $x$-direction, you get such and such
my mind goes blank! I tried ...
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Why is the gravitational force always attractive?
Why is the gravitational force always attractive? Is there another way to explain this without the curvature of space time?
PS: If the simple answer to this question is that mass makes space-time ...
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Why does the speed of an object affect its path if gravity is warped spacetime?
I think I understand the idea of thinking about gravity not as a force pulling an object towards another object but instead a warping of space so that an object moving in a straight line ends up ...
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If spacetime is curved, how would anyone know? If anyone could tell, would that really be spacetime curving?
I never had a problem accepting that spacetime is curved as a result of matter, until I learned the LIGO experiments showed that evidently the curvature of spacetime can be measured. This, to me, is ...
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How does classical GR concept of space-time emerge from string theory?
First, I'll state some background that lead me to the question.
I was thinking about quantization of space-time on and off for a long time but I never really looked into it any deeper (mainly because ...
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Rotate an object about the time axis
Is there a notion of rotating an object about its time axis? I'm not sure if this question totally makes sense, but it seems intuitive to me that an object with dimensions in the three spatial ...
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Can light exist in $2+1$ or $1+1$ spacetime dimensions?
Spacetime of special relativity is frequently illustrated with its spatial part reduced to one or two spatial dimension (with light sector or cone, respectively). Taken literally, is it possible for $...
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