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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What's the point of Pauli's Exclusion Principle if time and space are continuous?
What does the Pauli Exclusion Principle mean if time and space are continuous?
Assuming time and space are continuous, identical quantum states seem impossible even without the principle. I guess ...
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Why is spacetime curved by mass but not charge?
It is written everywhere that gravity is curvature of spacetime caused by the mass of the objects or something to the same effect. This raises a question with me: why isn't spacetime curved due to ...
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Interval preserving transformations are linear in special relativity
In almost all proofs I've seen of the Lorentz transformations one starts on the assumption that the required transformations are linear. I'm wondering if there is a way to prove the linearity:
Prove ...
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Is there a frame of reference in which I was born before I was conceived?
I'm struggling to understand the relativity of simultaneity and position.
If my conception and birth are separated by time but not space, a frame of reference in which my birth and conception are ...
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Does the curvature of spacetime theory assume gravity?
Whenever I read about the curvature of spacetime as an explanation for gravity, I see pictures of a sheet (spacetime) with various masses indenting the sheet to form "gravity wells." Objects ...
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What is the definition of a timelike and spacelike singularity?
What is the definition of a timelike and spacelike singularity?
Trying to find, but haven't yet, what the definitions are.
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Swimming in Spacetime - apparent conserved quantity violation
My question is about the article Swimming in Spacetime.
My gut reaction on first reading it was "this violates conservation of momentum, doesn't it?". I now realize, however, that this doesn'...
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Intuition for multiple temporal dimensions
It’s easy, relatively speaking, to develop an intuition for higher spatial dimensions, usually by induction on familiar lower-dimensional spaces. But I’m having difficulty envisioning a universe with ...
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Is String Theory formulated in flat or curved spacetime?
String Theory is formulated in 10 or 11 (or 26?) dimensions where it is assumed that all of the space dimensions except for 3 (large) space dimensions and 1 time dimension are a compact manifold with ...
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Is an atomic nucleus dense enough to cause significant bending of the spacetime?
We know that an atomic nucleus is very dense, but is it dense enough to create some interesting relativistic effects?
Obviously, in the classic limit, where we just assume that nucleons are little ...
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Is the "spacetime" the same thing as the mathematical 4th dimension?
Is the "spacetime" the same thing as the mathematical 4th dimension?
We often say that time is the fourth dimension, but I am wondering if it's means that time is like the fourth geometrical axis, or ...
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Ether vs. Quantum Field Theory
We were asked a question to differentiate the difference between the idea of an Ether and the idea of Quantum Fields. When I really began to think about it I concluded that the ideas are the same. The ...
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Is space really expanding?
In a book called "Einstein, Relativity and Absolute Simultaneity" there was this sentence by Smith:
There is no observational evidence for a space expansion hypothesis. What is observed are ...
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Why do objects follow geodesics in spacetime?
Trying to teach myself general relativity. I sort of understand the derivation of the geodesic equation $$\frac{d^{2}x^{\alpha}}{d\tau^{2}}+\Gamma_{\gamma\beta}^{\alpha}\frac{dx^{\beta}}{d\tau}\frac{...
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Understanding time crystals
In very recent publications, two groups in Maryland (paper: "Observation of a Discrete Time Crystal") and Harvard (paper: "Observation of discrete time-crystalline order in a disordered dipolar many-...
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