Most people are aware of the twin paradox, schrodinger's cat, and the double slit experiment. What are some of your favorite, lesser known, counter intuitive facts or thought experiments about physcis?
A compressed spring weighs more than an uncompressed on.
An otherwise empty volume with a radio signal warps space and dilates time the same as mass and matter.
Since we've proved the dual slit experiment works with photons, electrons, atoms, molecules, and chunky molecules, there's no reason to think it wouldn't scale up to boxes with cats or people inside. People understand that inside the box, the cat exists as a waveform, being both alive and dead in a probabilistic way. But from the cat's perspective, does the rest of the universe exist only as a waveform?
In addition to time dilation, space compresses at relativistic speeds. You can't have a test with two clocks synced to start ticking "once you cross a startline" because distances in space are also warped.
If velocity dilates time, shouldn't there be an absolute 0 for velocity? Where you experience the most time.
Spaghettification is horrifically fun.
If hawking radiation is the casimir effect sending in anti-matter into a black hole, reducing it's mass.... doesn't normal-matter fall in half the time balancing it out? Why would black holes radiate away without their mass depleting?
Time is a directional dimension. We can't go backwards. We do have another example of that when things fall into a black hole there is no longer any going out. The cone of causality is tilted past 90 degrees, and our 3 dimensions and time really gets reduced to 2 dimension and "going in". Likewise, they say the math works out nice and symmetrically if there were 13 dimensions (or whatever) and these other dimensions are tightly looped on themselves or we otherwise can't see any change in them.
If velocity dilates time, shouldn't there be an absolute 0 for velocity? Where you experience the most time.
No, velocity's fully relative.
If hawking radiation is the casimir effect sending in anti-matter into a black hole, reducing it's mass.... doesn't normal-matter fall in half the time balancing it out? Why would black holes radiate away without their mass depleting?
That formulation of Hawking radiation - which is a misleading simplification anyway - has nothing to do with matter vs. anti-matter (both have positive mass). It "works" (though again, it's not an accurate depiction of reality) because the distortion of spacetime is so great that the in-falling particle is always considered to have negative mass from the point of view of an outside observer.
and our 3 dimensions and time really gets reduced to 2 dimension and "going in"
There are still three space dimensions inside a black hole. There's no sense in which there is a reduction.
There's still 3 dimension, but one is now directional, like time. The reduction is that you can no longer move to the left. Time is still there too, but it's hard to detect since you're moving at a good clip and next to a massive object. Like those "hard to see" 9 other missing dimensions ala that kooky M-theory or whatever.
You can sort of argue that that is the case from an outside perspective, but the person inside the black hole is still free, for example, to wave their arm in any direction they like, locally.
The singularity becomes a moment in future rather than a location in space. In that sense, time is the unidirectional dimension, which is the same as it always was.