In this hebdomad ’s “ Ask a Physicist ” we undertake the question of whether you could spin yourself nauseous if the macrocosm really were empty , and why so many scifi author get artificial sombreness wrong .
receive to the first of our raw bimestrial “ Ask a Physicist ” column . All told , I ’ve received over 150questionsfrom singular readers on everything from spook and the afterlife to atoms and black holes . I make up one’s mind to bow out of religious questions and focus on ones about aperient . Today ’s question comes from Professor Andrew Higgins who require :
Is there an absolute reference frame for rotation ? … Imagine a blank place in deep infinite ( interstellar ) . Let ’s say it spins to generate stilted gravity , a la the quad station in 2001 . What is it spinning relative to ? The hotshot ? Which stars ? What if they are in a dust swarm and ca n’t see any sensation ?
I ’ve get somegrief in the pastfor turning an too serious eye to review the science of skill fabrication , but in your gloomy hour , you know you ’ve been guilty of far more rank nit - picking . Questions like “ Why do virtually all aliens look just like us ( albeit with forehead composition ) ? ” or “ How do I construct a warp drive ? ” haunt your dream . They ’re also harmless enough because after all , we do n’t really know those things might really work .
https://gizmodo.com/to-the-writers-and-director-of-hot-tub-time-machine-5504813
There are others , like unreal gravity , that we live how to make piece of work , and nearly every show and film become incorrect . There ’s plainly no excuse . 2001 got it right , and that was over forty years ago . Babylon 5 catch it right , and they were broadcast on TNT , for good saki .
You make contrived gravity by spinning your ship . It ’s as onetime as Newton ’s laws . The natural state of motion for a atom is to move in a straight line of descent and at a perpetual fastness . By spinning the ship , and acquire that the radius of the ship is with child enough so that your fountainhead and feet are moving at roughly the same speed , you ’ll sense a well-off stilted gravity where the “ out ” is “ down , ” and everything behaves like earth normal .
Newton could have designed contrived gravity ship , but he was plagued by a interrogation that would n’t be answered until the early 20th one C . One of the cardinal composition in Newtonian auto-mechanic ( and Einstein ’s particular relativity theory , by the way ) is the idea that there ’s no path that you could recite if you are moving at a constant speed and focusing or whether you are stand still . As a result of this , you get somepretty confusing results . But should n’t that apply to all motion , not just motion in a square line ?
https://gizmodo.com/what-happens-if-youre-traveling-at-the-speed-of-light-a-5527521
Supposing there was a bucket in deep space with nothing around it , and we fill the bucket with water system and start the bucket spinning around the vertical bloc . As it spins , the water will rise up the sides of the bucket , and act like a centrifuge , just like Clarke ’s Discovery One or one of those gravitron rides at the amusement green .
How do the bucket and the water know they ’re spinning if there ’s nothing to equate the movement to ? As an added bonus , try answering this interrogative sentence without using the word of honor “ space . ”
The philosopher Ernst Mach picked up this question in the nineteenth century and concluded :
[ The ] investigator must feel the penury of … knowledge of the contiguous connections , say , of the Mass of the macrocosm . There will brood before him as an idealistic brainwave into the principles of the whole matter , from which accelerate and inertial motions will lead in the same direction .
Or , more simply , “ Mass there influences inertia here . ”
The impression is a lilliputian more sophisticated than it seems at first . Of course distant deal affects objects here . That ’s just a trivial thing called gravity . But that ’s not what Mach was saying . What he was saying was that if you were to somehow average out over all of the stuff in the universe , we could discover some sort of absolute rest frame and then Newton ’s bucketful would rotate compared to that .
We probably would have forgotten about Mach in this context ( although he would still , of course , be remember by the shaving arrangement that bears his name ) , were it not for the fact that Einstein was haunt with Mach ’s principle . Does Mach ’s principle holds up in theory of relativity ?
In special relativity – the theory of mechanics in the absence seizure of gravity – no gravity means no distant lead and thus no fixed frame . And yet , even in an ( otherwise ) empty creation , special relativity enunciate that you would feel stilted gravity in a gravitron . When we do particle natural philosophy calculations , for example , we never admit somberness , but we always include centripetal force and angulate momentum , and everything comes out fine . The problem is that it ’s not unclouded whether we ’ve just gotten lucky or whether there ’s something deeper . We do n’t really know whether these calculations would work in a truly empty universe .
Fortunately , both for our existence and for answering this puzzle , ours is not an empty universe , and general relativity theory tells us just how to deal with the masses in the universe . John Wheeler gave a summary ( and widely quoted ) summary : “ Space enjoin weigh how to move , and issue tells space how to curve . ” What ’s more ( and as a freebie answer to the three or four folks who asked it ) the gravitational waves travel through distance at the speed of light . In other words , so long as there are things other than the pail in the universe , the overall gravitational field has to take account of all of everything self systematically .
In other words :
1 . universal relativity seems to obey Mach ’s principle in population with stuff in them .
2 . Our universe has stuff in it .
3 . 2001 would work in even the darkest , loneliest corner of the cosmos . Except for the weird psychodelic part . I never quite understood that .
Now that we ’ve got that worked out , there ’s no exculpation for phony artificial gravity devices in your sci - fi anymore . you’re able to concentrate on more pressing issues like FTL drive or why near all aliens mouth the same speech .
Dave Goldbergis the generator , with Jeff Blomquist , of“A User ’s Guide to the Universe : endure the Perils of Black Holes , Time Paradoxes , and Quantum Uncertainty . ”(Become a devotee onfacebook ! ) He is an associate professor of Physics at Drexel University . Feel free tosend him your questionsabout the universe .
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