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General Time Travel Discussion > Time Travel Thought Experiment

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message 1: by Lincoln, Temporal Jester (new)

Lincoln | 1290 comments Mod
A friend of mine explained this to me, so I will attempt to do it justice.

Imagine yourself holding a stick...a good long stick. One that is worthy for sword fighting on a campout stick. You swing it about making lashes and lunges. You even grab the stick in the middle and spin it above your head imagining it as a double bladed light saber.

Simple physics lesson time...The ends of your stick spin faster then the quick movements of your hands and wrists. So if you have a very long stick the ends move all the more fast compared to the center.

Thought experiment time...The Universal speed limit of the galaxy...The Speed of light...The closest we can come to it...Let's call it near the speed of light. So make the stick huge....and spin the stick at near the speed of light...The ends of your stick would therefore reach and or exceed the speed of light?

Never mind your stick might need to be so big as to not fit on planet Earth but that is just technicality.


message 2: by Robert (new)

Robert Italia (robert-italia) | 132 comments "So if you have a very long stick the ends move all the more fast compared to the center."

Faster or same speed (RPM)? Just asking . . .


message 3: by Howard (new)

Howard Loring (howardloringgoodreadscom) | 1174 comments Wrong premise.

Area covered in the spin is less nearer the center not at the edge, which encompasses a wider (longer) arc & so the fastest speed would occur near your hand, which can only approach the universal constant.

This is the same flaw as driving at the speed of light & then turning on the headlights, which by the way don't go any faster than your car, just now shining from a position ahead of it.

Everything's still Relative, just as your stick.


message 4: by Lincoln, Temporal Jester (new)

Lincoln | 1290 comments Mod
hmm..so the edges travel slower then the middle? Perhaps this whole experiment is flawed?


message 5: by Robert (new)

Robert Italia (robert-italia) | 132 comments Lincoln wrote: "hmm..so the edges travel slower then the middle? Perhaps this whole experiment is flawed?"

Depends on your definition of "speed."

http://en.wikipedia.org/wiki/Speed#Ta...

Still an interesting thought experiment (depends on the length of that stick; the longer it is, the more intriguing this experiment becomes). Where's a theoretical physicist when you need one?


message 6: by [deleted user] (last edited May 07, 2014 01:22PM) (new)

I am not a physicist, but I think the answer is this:

Like any physical object, the far end of the stick would increase in mass (relative to you as observer) as it approached the speed of light. At the speed of light, the mass would become infinite. To move an infinite mass, you need an infinite amount of energy. This is a finite universe, and there is therefore not an infinite amount of energy available.

Therefore you cannot move any part of the stick at the speed of light, let alone faster. What would actually happen is that you would have to pump more and more energy into moving the stick faster, with less and less effect, until you eventually used up all the energy in the universe, at which point the end of the stick still wouldn't have reached light speed.

If I am wrong, perhaps a physicist will put me right.


message 7: by Robert (new)

Robert Italia (robert-italia) | 132 comments See what you started, Lincoln?


message 8: by Lincoln, Temporal Jester (new)

Lincoln | 1290 comments Mod
No wrong answers Chris...and perhaps the premise is wrong as Howard points out...creating something long enough and then spinning it at super sonic speeds would it allow for the ends of the stick to reach light speed? It would take a lot of energy for sure...another technicality in this experiment.


message 9: by Robert (new)

Robert Italia (robert-italia) | 132 comments Lincoln wrote: "No wrong answers Chris...and perhaps the premise is wrong as Howard points out...creating something long enough and then spinning it at super sonic speeds would it allow for the ends of the stick t..."

Would the end of that stick turn to "light"? Howard?


message 10: by Mark (new)

Mark Speed (markspeed) | 131 comments Chris wrote: "I am not a physicist, but I think the answer is this:

Like any physical object, the far end of the stick would increase in mass (relative to you as observer) as it approached the speed of light. A..."


Chris, I think your hypothesis is right. I touched on this in Philosophy of Science at college more years ago than I care to remember and I've an interest in Astronomy. Yes, the mass of the stick would increase the further out from the centre of rotation, and you'd need oodles (standard unit of measurement!) of energy to increase the speed of rotation fractionally, until you'd consume all the energy in the universe. I'm happy to check with one of the two theoretical physicists in my office...


message 11: by Mark (new)

Mark Speed (markspeed) | 131 comments Hi everyone, here's the answer from one of our theoretical physicists:

Just because you have a really long stick, doesn’t mean you get to violate the laws of physics. A maxim to live your life by, if ever I heard one. It matters not for an individual lump of stick whether the driving force is coming from a rocket, an ion drive or the next bit of stick along; it just doesn’t get to go faster than light.


message 12: by C.J. (new)

C.J. Moseley (cjmoseley) | 15 comments As a former physicist I can safely say Chris is right, the energy required to accelerate the stick rises to infinity. Unless the stick is across the accretion disc of a black hole, in which case it will convert to Gamma radiation & X-rays and no longer be twirl-able. Not that rotational velocities and sheer velocities cannot exceed the speed of light, as they aren't necessarily real velocities. e.g. The end of a light house beam can rotate faster than the speed of light and the connection between the blades of scissors can move faster than light...


message 13: by [deleted user] (new)

C.J. wrote: As a former physicist I can safely say Chris is right...

It's nice to know that the time I spent reading about relativity in the school library when I was supposed to be studying A-level economics was not entirely wasted. :)


message 14: by Mark (new)

Mark Speed (markspeed) | 131 comments Wasn't economics labelled 'the dismal science' by Thomas Carlyle? Relativity and quantum physics are endlessly fascinating. I think it showed you had a very healthy mind, Chris!


message 15: by [deleted user] (new)

On the other hand, it was Einstein who said, 'Compound interest is the eighth wonder of the world.' So not all economics is dismal. Just most of it.


message 16: by Timothy (new)

Timothy Michael Lewis (timothymichaellewis) | 101 comments Economics is a tremendously important subject, the trouble is that it is at the level of development that medicine was in the 17th century' e.g let's drill a hole in that patient's head to let the evil spirits out...


message 17: by [deleted user] (new)

Didn't Pratchett interpret 'economics' as 'reflected sound of underground spirits'? Maybe he was making a point.


message 18: by Mark (new)

Mark Speed (markspeed) | 131 comments Behavioural economics is an interesting area. However, traditional macro-economics isn't much of a science. It's impossible to conduct conclusive empirical experiments with major economies because there are too many variables outside of anyone's control.


message 19: by Timothy (new)

Timothy Michael Lewis (timothymichaellewis) | 101 comments Ironically there are lots of very profound economic theories, but as you say most macro-economic theory is bad assumption built on bad assumption. Anyway this thread is supposed to be about time travel and not in case of me travelling back in time to when I did my economics degree!


message 20: by MK (new)

MK (wisny) | 188 comments I dig geek talk, may I just say :D


message 21: by Lincoln, Temporal Jester (new)

Lincoln | 1290 comments Mod
Oh yeah MK. I always attract the ladies with my profound geek talk! LOL!


message 22: by MK (new)

MK (wisny) | 188 comments heheh :D :D :D

Hey, it worked for my husband ;-)


message 23: by [deleted user] (new)

Mika wrote: Wasn't this the premise of H.G. Wells' time machine?

You're saying that a time machine is a geek's chick magnet? Where can I get one?


message 24: by Timothy (new)

Timothy Michael Lewis (timothymichaellewis) | 101 comments All the time machines are back in 1963 in Dallas...


message 25: by [deleted user] (new)

That's a bootstrap problem, then.


message 26: by Garrett (last edited May 16, 2014 07:27AM) (new)

Garrett Smith (garrettsmith) | 246 comments Chris wrote: "Mika wrote: Wasn't this the premise of H.G. Wells' time machine?

You're saying that a time machine is a geek's chick magnet? Where can I get one?"


Well, think about it, has Dr. Who ever had a problem attracting women? No.

But, wouldn't it go the other way too. If a chick had a time machine, wouldn't it be a geek magnet.


message 27: by Lincoln, Temporal Jester (new)

Lincoln | 1290 comments Mod
But, wouldn't it go the other way to. If a chick had a time machine, wouldn't it be a geek magnet.

Yes a girl who appreciates science fiction, is tech savvy, and yes if she had a time machine as a geek I would be attracted. LOL


message 28: by Timothy (new)

Timothy Michael Lewis (timothymichaellewis) | 101 comments Two words : River Song


Justanotherbiblophile | 11 comments Timothy wrote: "Two words : River Song"

Would bang.

Bring on the geekettes.


message 30: by Timothy (new)

Timothy Michael Lewis (timothymichaellewis) | 101 comments Just don't wear a Fez!


Justanotherbiblophile | 11 comments Chris, are you saying she doesn't like men?

If she blows away every man who's attracted to her, then she's going to have a tough time getting any. :)

And if she just attempts to randomly murder anyone who's attracted to her, then she's going to have enough enemies that she won't be blowing away all of us.


message 32: by Howard (new)

Howard Loring (howardloringgoodreadscom) | 1174 comments Chris #35 mentions women Time Travelers:

Perhaps they have a man already


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