New answers tagged

0

You are thinking of the entangled state as two objects, one of which is stationary With respect to us and one of which is moving at near $c$ With respect to us. Viewed this way it is natural to think that one object must be time dilated With respect to the other. However the entangled state is not two objects - it is a single extended object described by a ...


0

As far as I know, no notion of time travel before Herman Weyl's 1922 book "Space, time, matter", where he vaguely discusses the notion that the metric of spacetime could become so twisted as to allow time travel. I recall a 1917 special relativity book discussing the classical problem of a particle going faster than light going backward in time, but only to ...


0

Note that when you travel by any mean, and even when you stay in a chair, you do travel towards the future, right ? At 99.99% of c you would arrive very fast in your frame, because for everybody else looking you, you were almost frozen during the 4.22 times. But it's not different to the first case above concerning the "pre-existence" of the future. PS: ...


2

just try an online calculator like Wolfam : 13.65 billion years after the big bang redshift = 0.00474 time ago (lookback time) = 65.6 million years distance (comoving) = 65.7 million ly (light years) = 20.2 Mpc (megaparsecs) = 6.22×10^20 km (kilometers) = 3.86×10^20 miles fraction of total observable radius = 0.00141 scale factor = 0.995 × current ...


3

I think I should go from another direction. Yes, obviously the Hubble constant refers to intergalactic motion, and cannot be properly applied to intragalactic effects. That does not necessarily mean that such effects do not exist (it just means that they are too minor to measure, and/or usually overshadowed by other effects; that said, I believe that GPS is ...


13

Shortly, no, this is not correct. Here's why. Hubble's law gives us that for a distance of one megaparsec, that space expands by approximately 70 km/s (the data varies, but it's somewhere between 60-80 km/s - it doesn't matter, and you'll see why). Now, how tall is your average human? Let's be generous and say your time traveler is 2m tall. Now, how many ...


14

No, because Hubble expansion has negligible effects on very small systems (such as human beings). Here is an answer which explains the maths behind it : Can the Hubble constant be measured locally??


0

The Ellis-Bronnikov wormhole, with topology $\mathbb{R}^2 \times S^2$ and metric \begin{equation} ds^2 = - dt^2 + dl^2 + (b^2 + l^2) d\Omega^2 \end{equation} violates the ANEC and possesses no closed timelike curves (nor can it be made to develop any since the topological handle is between two different spacetimes and not the same one), as can be seen by ...



Top 50 recent answers are included