• A hypothetical physics conundrum (You are required to think to enter this thread)
    79 replies, posted
Ok, so we all hopefully know about Einstein's E = mc^2 and all that, and how you supposedly can't travel faster than the speed of light (I think there's a thread about just this in the first few pages of GD). So, I was thinking about this in the shower, where I think a lot, and I came up with this ridiculous scenario in which I couldn't picture why that theory would hold true. Please bear with me here, I have an extremely limited understanding of this theory and why it works, so if I'm missing something obvious please just explain it. So, let's say you have this perfectly straight bar, made of some imaginary un-bendable material (might not even be necessary), floating out in space, where there would be no resistance to movement, that's absolutely infeasible in length; spanning a galaxy or two, we'll say (But it has it's own space where it could complete a full rotation without encountering a single atom along the way). Now, you're at the exact center of this monstrous bar, with this little device that is somehow, I don't know how, but by some means, locked into it's current location and completely unmovable, that is in some way attached to this bar. When turned on, this device will spin the bar, completing one rotation in ~1 minute. Now, at your location, this will seem like a slow pace, maybe a few inches every ten seconds where the device connects with the bar. But, the ends of the bar will be moving at the same [i]relative[/i] speed to the center of the bar, completing one rotation in the same amount of time, but it would be an enormously larger rotation, hundreds of thousands of light years in a minute. Now, what would stop it? While typing this I came up with the possibility of the bar's own gravity possibly affecting it, but if there was absolutely nothing in the way of it's rotation to give resistance wouldn't it still complete it in the minute-long period? I know that the mass increases with speed, but with absolute zero resistance I would think this wouldn't matter. And yeah, I know this exact scenario is impossible, but the fundamentals behind it are slightly plausible. Alright, well everyone seems to think I'm dumb, so I'm sorry. I wont delete this post because that'd just look like I was trying to cover for myself. I also don't want to bump it so Imma just edit this. Feel free to rate whatever, I guess a mod can lock this now.
I am rebel. I am not think
"What if the laws of physics didn't apply, then there would be some CRAZY shit man!"
Its speed wouldn't surpass the speed of light.
Think of the bar as being composed of atoms whose individual tangential speeds cannot exceed the speed of light.
I remember Hawking talking about this a bit in one of his books, I think it was either "A brief history of the universe" or "the universe in a nutshell". I can't exactly remember what he said and my copy of the book is long lost, but you can read up about it there if you're an astrophysics buff like me. [editline]3rd April 2011[/editline] Oh, and your answer as I see it: yes, it would pass the speed of light, but it would be breaking the laws of physics as no object composed of more than three atoms/molecules is unbendable. EDIT: dear fuck I was tired last night this is wrong as hell
Physics will win. It always wins. Always.
if your going the same speed, time is the same for you. If someone light years away traveled 100km/h in space and I traveled 100km/h in space we'd both be travel a 100km in space in 1 earth hour. [editline]4th April 2011[/editline] [QUOTE=cagafuego88;28977818]Physics will win. It always wins. Always.[/QUOTE] *cough* Gravity will win. It always wins. Always
if you are so smart op why didn't you paragraph it, hard to read half a page of a block of words
The movement of the bar propagates as a phonon. It can't travel at or faster than the speed of light. Once the center of the bar starts moving, it still takes time for this movement to spread out to the edges, and no place along the bar will be traveling at or above the speed of light.
If it were unbendable, the motor in the center would need to accelerate the outer edges first, in layman's terms. So the edges of the bar would reach max. tangential velocity of [i]c[/i] and not be able to accelerate any more, limiting the tangential velocity of the inner portions of the bar. All sections would have the same angular velocity, but tangential velocity would decrease as you got closer to the center. All force travels through objects in waves; force does not instantaneously act on all particles of an object. This holds true for a motor which rotates a bar from the center; if it were unbendable, the inner sections of the bar would have to "wait" for the outer edges to "receive" the force from the motor and begin to rotate. Unfortunately, nothing of significant mass can be completely unbendable. So the inner portions would begin to accelerate as the outer edges "waited" to begin to rotate, causing a bend. The physics hold firm though; the inner portion's tangential velocity will be stuck at a much lower value than the edges, which will reach the speed of light.
Well, no, they won't reach the speed of light, no matter how much angular momentum you put into them.
Sorry, that is, the closest to the speed of light it could possibly achieve.
This is basically like saying "I can make a cup of water turn into a cup of boiling water with ice cubes in it, given that the applicable laws of physics don't apply" There's a bunch of situations similar to this, like the laser on a ship moving just under the speed of light
Now I've started to wonder myself about something. Assume you have an infinite amount of space to extend the length of the bars. We know that the farther out you stand on the bar (from the center), the faster you go when it rotates. Despite this, is there a limit as to how fast you can possibly go? Unless there is a law I'm not aware about (we know that friction and whatnot isn't in play in the OP's theory), doesn't this bar have a "speed limit" of infinity? Just think, the longer it is, the faster the end is moving. Remember, we'd have infinite room for expansion of the bar's length. Interesting.
Whenever I ask various questions in physics the teacher replies with a cruel laugh and his fascination with lasers greatly worries me. Asking this would be bound to cause problems.
[QUOTE=Andokool12;28978588]Now I've started to wonder myself about something. Assume you have an infinite amount of space to extend the length of the bars. We know that the farther out you stand on the bar (from the center), the faster you go when it rotates. Despite this, is there a limit as to how fast you can possibly go? Unless there is a law I'm not aware about (we know that friction and whatnot isn't in play in the OP's theory), doesn't this bar have a "speed limit" of infinity? Just think, the longer it is, the faster the end is moving. Remember, we'd have infinite room for expansion of the bar's length. Interesting.[/QUOTE] No. Read my post up above. Or if you don't want to: When a bar rotates, the inner portions must comply with the outer portions. The outer portions are limited to the speed of light, restricting the speed of the inner portions.
I remember feeling the same way when I fucked my last physics test.
[QUOTE=Andokool12;28978588]Now I've started to wonder myself about something. Assume you have an infinite amount of space to extend the length of the bars. We know that the farther out you stand on the bar (from the center), the faster you go when it rotates. Despite this, is there a limit as to how fast you can possibly go? Unless there is a law I'm not aware about (we know that friction and whatnot isn't in play in the OP's theory), doesn't this bar have a "speed limit" of infinity? Just think, the longer it is, the faster the end is moving. Remember, we'd have infinite room for expansion of the bar's length. Interesting.[/QUOTE] The speed of light is the limit. Matter can not possibly achieve anything faster than 99.9(add however many 9's you want) percent of lightspeed.
[QUOTE=DChapsfield;28978279]If it were unbendable, the motor in the center would need to accelerate the outer edges first, in layman's terms. So the edges of the bar would reach max. tangential velocity of [i]c[/i] and not be able to accelerate any more, limiting the tangential velocity of the inner portions of the bar. All sections would have the same angular velocity, but tangential velocity would decrease as you got closer to the center.[/QUOTE] [img]http://img651.imageshack.us/img651/4607/cubertfarnsworth.jpg[/img] [i]I understand how the engines work now. It came to me in a dream. The engines don't move the ship at all. The ship stays where it is, and the engines move the universe around it.[/i]
The problem is the energy needed. If a 1-kilogram mass was attached to the end of a 1-meter bar, it would take about 10 joules to accelerate it. However, at the end of a 10-meter bar, the same mass would take 100 joules. This means, effectively, that levers do not change the amount of energy necessary to achieve a given velocity. That linear scale only holds at low speeds. Once you start getting into relativistic speeds (about .1 c), it becomes increasingly difficult to accelerate any mass, eventually reaching a point where it takes infinite energy to accelerate further (this point is the speed of light in a vacuum). The Large Hadron Collider can accelerate objects to 0.999999991c, but that takes over 200 megawatts of power, and only accelerates tiny nanoscopic particles.
It would hit God in the dick
@op: shut up
Have you heard of fucking indents, jesus christ man
You're taking a situation that is physically impossible and trying to apply physics to it. It's really a quiet useless thought.
The amount of energy needed to revolve the bar around any axis at the speed of light entails the energy encased in all matter in the universe, including the bar itself. Thus, impossible to achieve.(Including within frictionless space.)
Maybe the only reason he said that there was nothing that can go beyond the spend of light was simply because we could never measure something going faster than the speed of light. We wouldn't even know it was there because it moves so fast.
I asked my science teacher a very similar question, he told me that at the edges of the bar where the speed would surpass the speed of light, it would simply turn into energy.
[QUOTE=Dr. Fishtastic;28979899]Have you heard of fucking indents, jesus christ man[/QUOTE] A not-so-hypothetical posting conundrum, starring: the op. (you are required to indent in order to create this thread)
What if you repeated the same experiment, but this time, the bar has negative mass?
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