# Tag Info

## New answers tagged causality

1

Let's clarify the concepts: Determinism: for a given experimental set up, every experiment will yield the same results. QM are not deterministic, if you measure a superposition of states, you could get one or the other, with certain probability, and there is nothing you can do about it. Causality: causes happen before its effects. QM is causal, because if ...

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The causal structure of spacetime is determined by the lightcones at every point of it, basically. From this you can construct such things as the chronological past (all events that influenced this point), the chronological future (all events that will be influenced by this point), the Cauchy horizon (the limits of what you can predict in the future from a ...

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Partial answer: In the context of general relativity, it is conventional to make use of conformal diagrams (a.k.a. Penrose diagrams to enable us to visualize a spacetime. These bring the boundaries of the spacetime (at infinitey) to a finite coordinate value, and keep lightlike worldlines at 45 degrees. As such, they're the generalization of Minkowski ...

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As you have discovered proper time, $\Delta\tau$, can be either real or imaginary. However, this means that it does not necessarily reflect something measurable with a clock. When it is imaginary, as in the case of a space-like relation of two events, then there is no single clock that can be present at both events. To do so would require having a velocity ...

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Because of quantum mechanics (random chance)nothing is certain. So it is possible to work out the chance that one thing will happen, but cannot be certain of the actual outcome. Also, another way to show the impossibility of predicting the universes future precisely is this: Suppose there was a machine that predicted the future of the universe. It would need ...

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The simplest idea is that the collapse of the previous universe caused the big bang. I imagine it as black holes smashing into each other at great speed, immediately causing a nuclear reaction. There are some unproven theories that need to be adjusted, such as the idea that dark energy density remains constant as space expands. Black hole radiation has ...

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if you consider a rigid rod and apply a torque at one end, by definition of being rigid, the whole body must start rotating at the same instant. But [...] I'm wondering if one can even define a rigid body in a relativistically correct manner In the strict sense indicated: one can not. An important clue in the argument has been stated by J. L. ...

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