0
votes
1answer
112 views

Problem in Grandfather paradox

I am very confused about a paradox and a recent research on Quantum particles. I have read an article which states that time travel is possible for quantum particles. If it is possible then why does ...
2
votes
4answers
132 views

Principle of locality

Why does the principle of locality have so such great importance in physics that theory should be consistent with it?
4
votes
2answers
157 views

What does “causally connected” or “causes” really mean?

In a different thread, a user stated the following in respect of events preceding or following other events: However, if the two events are causally connected ("event A causes event B"), the ...
1
vote
0answers
74 views

Big Bang, Heat Death, and cause and effect

If the Universe has two 'end points', one being the Big Bang, and the other being heat death, is there anything in the laws of physics which forbid a random fluctuation in the heat death state from ...
0
votes
1answer
51 views

A meaningful distinction between determinism and causality

Causality is generally accepted to be a fundamental physical principle. But quantum mechanics is acausal (e.g. there is no 'why' as to the result of a measurement of the position of a particle in an ...
1
vote
0answers
82 views

Does nonlocal theory violate causality?

Let's talk about two kinds of nonlocal theories. The first one frequently derives from integrating out part of the degrees of freedom to obtain a kind of effective theory. Probably, we get an integral ...
3
votes
2answers
233 views

Why does the Dopfer EPR experiment require coincidence counting?

Dopfer Momentum-EPR experiment (1998) seems to provide a interesting tweak in the EPR experiment. To read more details on this experiment, see: ...
2
votes
2answers
758 views

Are random quantum phenomena happening without a cause?

In everyday life, most of us assumes every event and object has a cause in some sense. I am wondering if the same is true for quantum physics. Does the random nature of quantum phenomena mean they ...
0
votes
0answers
179 views

Quantum Entanglement and Causality [duplicate]

How does Quantum Entanglement not violate the principle of relativity? Alice and Bob are working on an entangled system of electrons which is spaced long apart. Now if Alice measures one electron to ...
0
votes
1answer
97 views

Is this hypo-theoretical model of future prediction feasible? [closed]

First let me state that I am not, nor ever have I been, a physics student. I am working on an idea for a book I'm writing. This is a thought experiment that posits the existence of a computer system ...
3
votes
1answer
158 views

Going through a ring of black holes

Mathematician here with a speculative physical question -- feel free to boot me if the level isn't right. Suppose one finds, or builds, a constellation of several black holes arranged in a circle. ...
12
votes
1answer
547 views

How is quantum mechanics compatible with the speed of light limit?

Consider a free electron in space. Let us suppose we measure its position to be at point A with a high degree of accuracy at time 0. If I recall my QM correctly, as time passes the wave function ...
0
votes
1answer
182 views

Information faster-than-light and GR vs. QM

What is meant by the statement that information cannot travel faster than light? If I write down something on a paper, isn't there according to QM a non-zero probability that an identical paper can ...
-1
votes
3answers
740 views

Using quantum entanglement to send messages back to the past [duplicate]

Possible Duplicate: Entanglement in time I heard that there is an experiment that uses quantum entanglement to try to send messages back to the past. I am having a hard time understanding ...
8
votes
8answers
691 views

Is “Causality” the equivalent of a claim that the future is predictable based on the present and the past?

In classical (Newtonian) mechanics, every observer had the same past and the same future and if you had perfect knowledge about the current state of all particles in the universe, you could ...
16
votes
2answers
2k views

Definitions: 'locality' vs 'causality'

I'm having trouble unambiguously interpreting many answers here due to the fact that the terms locality and causality are sometimes used interchangeably, while other times seem to mean very different ...
0
votes
0answers
226 views

Hardy's Theorem

https://perimeterinstitute.ca/psi_portal/sites/perimeterinstitute.ca.psi_portal/files/hardyphysrevlett.68.2981.pdf Some researchers in Bohmian Mechanics have hoped to make the theory Lorentz ...
12
votes
1answer
514 views

Backward causality: A question/extension to Ma et al.'s “Experimental delayed-choice entanglement swapping”

In a philosophically rather interesting experiment, Ma et al. show that backward causality exists in quantum physics. An Ars Technnica-article gives a less technical account. From Ars Technica: ...
14
votes
5answers
2k views

The transactional interpretation of quantum mechanics

John Cramer’s transactional interpretation of quantum mechanics (TIQM) is billed as resolving the fuzzy agnosticism of the Copenhagen interpretation while avoiding the alleged ontological excesses of ...
40
votes
8answers
7k views

Why quantum entanglement is considered to be active link between particles?

From everything I've read about quantum mechanics and quantum entanglement phenomena it's unobvious for me, why quantum entanglement is considered to be active link. I.e. it's stated every time that ...
14
votes
5answers
877 views

Is there such a thing as “Action at a distance”?

What ever happened to "action at a distance" in entangled quantum states, i.e. the Einstein-Rosen-Podolsky (EPR) paradox? I thought they argued that in principle one could communicate faster than ...