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.
20 questions from the last 30 days
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A question about interstellar travel [duplicate]
If an observer $O'$, one light-year away, approaches $O$ at a speed close to that of light, the time elapsed for observer $O'$ would be practically zero. If $O$ is the one approaching, the opposite ...
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Application of Reichenbach synchronisation
Suppose I adopt the Reichenbach synchronisation process so that light heading radially away from me- according to my clocks- travels with infinite speed, while light heading directly towards me ...
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Relationship of space-time to energy and momentum [closed]
After reading Noether's theoram and many other examples like objects tendency to follow its geodesics in spacetime makes conserved quantities like momentum etc meaningful so , are energy and momentum ...
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Proper times of two inertial observers. [closed]
According to the Lorentz transformations, if an observer $O'$ moves at a relative velocity $\beta$ with respect to another observer $O$, the proper times $t$ and $t'$ would be related by:
$$ t=\sqrt{1-...
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Invariance of the interval in Schutz - maths error?
Reading Schutz's book on GR: On page 9, there's a derivation that I don't follow.
$\newcommand{\d}{\Delta} \newcommand{\b}[1]{\bar{#1}}$ Then in the
expression for $\d\b{s}^2$, $$\d\b{s}^2 = -(\d\b{...
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Can the Universe stop expanding?
I’m a 7th grader, so I'm not good in physics that much, but I'm just a curious boy which wants to become a cosmologist. Can the amount of energy or particles run out?
For example, pizza dough can be ...
user555744
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What exactly is different about the slice of space and lightcone concept in special relativity?
In Sean Carroll's book on GR, in the very first chapter about SR, he mentions how the difference between Newtonian concepts of space and time, and the view put forward in SR is how there is an "...
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How to define an effective light cone or null direction from discrete arrival times on a lattice?
In several discrete or lattice-based approaches to spacetime (causal sets, Regge-like discretizations, lattice field theory, numerical GR, fast-marching/eikonal methods), one often works with a ...
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Is every symmetric causal isomorphism between distinguishing spacetimes a conformal diffeomorphism?
For this question let us consider spacetimes which are time-oriented and distinguishing (or stronger).
Some bijections between such spacetimes are known to be conformal diffeomorphisms because they ...
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What’s a spacelike geodesic? [duplicate]
Timelike geodesics are the paths taken by particles not subject to gravitational forces. So what’s a spacelike geodesic? You can’t send a particle along a spacelike path.
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Does Spacetime Curvature affect the Higgs Trilinear Self-Coupling by modifying the Vacuum Expectation Value?
I have been studying the Higgs mechanism, and most standard derivations assume flat Minkowski spacetime.However, in the early universe or near compact objects such as black holes, spacetime curvature ...
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Why can't only time dilation alone take place in special relativity, without length contraction? [closed]
An object moving relative to an observer experiences time dilation, as stated in the theory of Special Relativity.
But suppose only time dilation occurred while lengths remained unchanged.
Wouldn’t ...
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Can Spacetime bend itself?
If spacetime can bend due to gravity, could too much energy in one point make it collapse and then expand again like the Big Bang?
Can spacetime bend due to gravity?
user555744
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Clock on a moving rocket
Let's say that there is a clock mounted outside a rocket that is moving at a constant velocity upwards as measured by an adjacent observer looking at the clock from a stationary platform. The clock's ...
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Does the linearity of transformations between inertial coordinate frames follow from the standard postulates of special relativity?
There are often multiple equivalent ways to formalize a physical theory, which may disagree on which propositions are fundamental axioms and which are derived theorems, but which (hopefully!) agree on ...
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