Tag Info

New answers tagged

0

Do we know any event (or whatever else) which has no reason? Reasons (causes) are constructions of human mind. There are many things that human mind has not been able to explain with reasons. I like the following example my friend told me. Imagine a man walking down the street that gets hit by a flowerpot falling down from a balcony above. You may ...


0

An answer you might find satisfactory is that our model of spacetime is "larger" than what we observe. Yes, there is a preferred direction which gives us a (1,3) signature, but actual, real objects in spacetime must travel on timelike curves (we normalize the length of their geodesics to -1). These timelike curves only transverse part of the entire ...


0

You've mostly only stumbled upon one fact with your list of paradoxes: a lot of the things presented in the movie Interstellar are not parts of a physical theory. This includes: "The bulk", whatever that's supposed to mean, and especially Arms reaching through "the bulk" (???) True back-in-time communication/time travel, "Tessaracts" (the word "tessaract" ...


0

To understand Brian Cox's actual comment: The minus sign in the metric actually creates a discrepancy which does not exist in Newtonian mechanics: there is a space between light cones. It's a little easier to talk about this in the (+ − − −) convention where particle trajectories have real (not imaginary) lengths. So let the length of a 4-vector $[w, x, y, ...


3

No, because it isn't true. Nothing can move backwards in time because nothing can move forwards in time. Moving in or through time is just a figure of speech. So is “the flow of time”. If you open up a clock you don’t see time flowing through it like it’s some cosmic gas meter. You see little cogs and things, moving. Clocks always feature some kind of ...


2

I'm digging this thread out just to clarify some things for those who might have a similar question. Summary We cannot use $\mathcal T$. Space-like four-vectors are essentially like $(0,x,y,z)$, so we can ignore the time and do three-dimensional rotations to get $(0,-x,-y,-z)=-(0,x,y,z)$. A la Valter Moretti As Valter Moretti already pointed out, you ...



Top 50 recent answers are included