All Questions
Tagged with spacetime spacetime-dimensions
238
questions
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54
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What happens if we differentiate spacetime with respect to time? [closed]
Essentially, what would differentiating space-time with respect to time provide us with? What are the constraints associated with such operations? Is it possible to obtain a useful physical quantity ...
0
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0
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38
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How many dimensions are in string theory? [duplicate]
How many dimensions are in string theroy? I heard that there are 11 but to my understanding, there is an infinite, also can strings be on a 2D plane?
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2
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58
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How small can we measure space? [closed]
I got this question after looking into transcendental numbers and I noticed how there are some distinctions that should be made from numbers and reality especially in measurement of length for example ...
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2
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1
answer
718
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How many null directions are there?
The metric signature of spacetime is usually given as ($3,1$), but spaces can also be ($3,n,1$). Null surfaces include photons and event horizons, which exist, so is $n$ actually $ > 1$ in the ...
- 255
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What is the problem with two time dimensions? [duplicate]
I am reading a book "General relativity: The theoretical minimum" by Leonard Suskind.
In page 168-169, the author explains the reason why we don't consider the case with two time dimensions ...
- 311
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0
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32
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Still having trouble understanding gravitational lensing [duplicate]
The normal diagram used to explain gravitational lensing shows a two-dimensional plane that is deflected by a heavy weight. This is a two dimensional description that requires an extra dimension to ...
- 319
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Do we live in a 4-dimensional space, i.e. a 5-dimensional spacetime? [duplicate]
As far as we know:
If two one-dimensional lines are placed parallel, they need to be on a two-dimensional plane.
If two 2-dimensional planes are placed parallel, they need to be in a 3-dimensional ...
1
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0
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74
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Why can't the metric have more than one timelike coordinate? [duplicate]
In one of his lectures, L Susskind stated that he cannot make sense of a metric with more than one timelike dimension. I also have trouble imagining it, but is there a good mathematical or physical ...
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106
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Another dimensions [closed]
Just a science ponderer, and pretty much interested in physics. Please guide me if I am wrong.
There have been many statements made by the physicists about the existence of other dimensions (...
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54
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Are branes topological defects? How else could they be physical?
As far as I understand, the branes of brane cosmology are lower-dimensional "sub-manifolds" of some space. It was hard to imagine for me how such structure could exist and be physical. But ...
- 531
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82
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Could the universe be a topological defect in a higher space?
I am a mathematician with an undergrad understanding of physics. I recently learned of topological defects in quantum fields. It is an intriguing idea that there could be regions in our universe that, ...
- 531
9
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3
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Why is Spacetime described as flat even though we live in 3 dimensions of space?
I’ve always heard and seen diagrams that show spacetime as being “flat” or in 2 dimensions with curvature. How does this correspond to the 3 spacial dimensions that we perceive to exist in?
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In relativity, is the fourth spacetime dimension spatial or nonspatial?
In "An Introduction to Modern Astrophysics" Carroll and Ostlie describe the curvature of space by mass as:
curving in a fourth spatial dimension perpendicular to the usual three of "...
- 13
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1
answer
120
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Dimensionality problem in special relativity
Suppose $A$ is a null $4$-vector in Minkowski space-time, $M$. Then the vector space spanned by $A$: $\operatorname{span}(A)$ is unidimensional. The orthogonal complement of this vector space $\...
- 51
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2
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148
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Dimension of a vector space of all tensors of rank $(k,l)$ in 4D
Dual vector space is the set of all linear functionals defined on a given vector space. The vector space and dual vector space is isomorphic and hence have the same dimension. A rank $(k,l)$ tensor is ...
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