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xkcd #3317: Gravitational Square Wave
Title text:
Depending on the energy deposition I can manage, it might also be a fun prank on the rest of the Earth.
Transcript:
Transcript will show once it’s been added to explainxkcd.com
Source: https://xkcd.com/3317/
I thought my hobbies are expensive.
Those cartoon artists really are raking in big money.
I knew I should have been a cartoon artist.
My mama begged me to get into cartooning but I thought corporate law was the path to financial independence how could I be so foolish
Follow your heart… bah! Obey your mum is the correct answer.
Randall has been banned from fourteen type 3 civilizations so far
So I guess Randall is Q?
We'd be doomed, but it'd be funny the whole time
And informative!
Also feels like something a Culture GSV might find amusing.
I'm waiting for the day when this will be the "relevant XKCD"!
Ok, that’s a nice one from XKCD.
Thoigh I’m not sure I appreciate the hover over joke - it seems to imply a square gravity wave would have noticeable physical effects?
Depending on the energy deposition I can manage, it might also be a fun prank on the rest of the Earth.
If you did this near enough to earth with supermassive blackholes (had high enough “energy deposition” to the spacetime around earth), there would absolutely be noticeable physical effects.
Yes, likely the radius of this ripple would be massive enough to coat most of earth simultaneously, but if you’re looking away from or directly towards it, you’d probably notice some odd stuff going on.
Sure, you would need to make sure the oscillation frequency is low enough to be easily noticed and many many orders of magnitude stronger than the waves we typically detect, but if you can manage a period on the order of a second or more and just enough strength to bend light a little across the falling and rising edge of the wave, people on earth would likely be able to see the warping of space around them. Like imagine the stars or the moon looking like they are stuttering, jumping back and forth in the sky every-time a wave passes.
That would probably be an effective prank as it may cause various emotional effects on the inhabitants of earth who didn’t know what the hell was going on
Awesome, thank you!
I was wondering, as a completely naive person, if a large enough square gravity wave would be capable of “moving” objects faster than the sites of light, where this is permissible because it wouldn’t be movement but space time bending.
Wouldn't the magnitude of forces involved make it impossible to keep the oscillation frequency "low enough to be easily noticed"? Like, to not collapse into each other you're going to need some pretty high speeds, and conservation of angular momentum is gonna only make it faster as you "Square" the wave.
Maybe, I don’t know. I mean for a single cycle, you could probably do low frequencies easily.
Two black holes 1ly apart would take at least pi ly to complete a full circular arc around their barycenter. That would give you a frequency of one full cycle of the gravitational wave every 3years. (Actually it might be 1.5 years since I think the peaks of the wave are caused by either body and the troughs are the gaps between them so a half circle is a full cycle of the wave assuming both holes are the same size). Point is, thats a really low frequency which is “easy” to setup.
But yes, trying to prevent the decay of the spiral long enough to get a few good pulses at roughly the same frequency would require some work and might not be possible past a certain high frequency.
However, this might only limit how many of the increasingly higher frequencies you can get before it’s not really feasible. But hey you only really need the biggest one to cause weird visual effects. It just wont be as sharp of an effect since the geodesics light takes will smoothly change their relative angles to you rather than doing so almost instantly.
So if you can get a pair of supermassive blackholes to orbit with a period of ~1sec without immediately spiraling faster and colliding, your prank on earthlings would still mostly succeed. (Your prank would likely succeed even with the collision since as the frequency increased, it would eventually hit the audible range and that would honestly be more distressing in some ways (to be audible would of course require your ears to be oriented such that the spatial disturbances happen along the right axis and are strong enough to move your inner ear bones without being strong enough to cook you from the induced vibration in your whole body))
But what a way to go ..
It's all fun and games until you snag your favourite sweater on a Gibbs spike.