Why is faster-than-light travel 'impossible'?

[Quick_Nick]

Gravity has been measured to propagate at the speed of light. (just saying )

 

[Keatah]

Do you mean that the water will move frictionlessly against the sides of the container (or whatever), so that relative to something outside your rotating object, the water is stationary?

Basically, you need some sort of friction. Something to "scoop" it along its path. Something to ensure the water or subject matter gets pressed against the inner part of the outer edge of the wheel.

Just like a paddle-wheel on the Queen Mary or some other boat!

hahah! Just imagine jumping up in one of these things. Assuming the ceiling was high enough. You'd get hit with a blast of air! Now, for bonus points, If you were facing spinward, or along the direction of apparent linear rotation where would you land? And would the wind hit you in the front or back?

AND imagine if the while was huge, like the BigWheel Station for Orbiter, and you spun it up real fast, you could get horizontal tornadoes and hurricanes and cyclones and stuff. There could be lots of aerial stunt possibilities! Or you could turn the thing into a giant wind tunnel and get jet-like speeds from airplanes without engines!:thumbup:

---------- Post added at 09:55 PM ---------- Previous post was at 09:41 PM ----------

Gravity has been measured to propagate at the speed of light. (just saying )

Even considering quantum entanglement? I understand that sometimes particles are split apart at the event horizon of a black hole. Like that Hawking radiation thing or something. Part is left behind and sucked up, the other is left free to roam the universe, but if you blow up one of the splitted-up particles the other one knows about it instantaneously, with total disregard of time and distance.

At any rate. I know that relativity is all wrong and will figure out how to explain the fuge raging inside my head. I have little doubt the world of physics will be shocked and totally blown away. All this funk we know today is gibberish, the universe is far stranger than you can imagine.

---------- Post added at 09:56 PM ---------- Previous post was at 09:55 PM ----------

For starters, you tell me what the shortest length of time is. Whether it be micro-seconds or atto-seconds.. Just tell me..

 

[tblaxland]

For starters, you tell me what the shortest length of time is. Whether it be micro-seconds or atto-seconds.. Just tell me..

5.39124e-44 s. [ame="http://en.wikipedia.org/wiki/Planck_time"]Planck time - Wikipedia, the free encyclopedia[/ame]

 

[Keatah]

thats in an atmosphere. centrifugal force does move things outward, but it first needs another force to make things stay on whatever is generating centrifugal force.

Usually that's surface tension, air friction, molecular stiction, stuff like that. Yeah baby! If you get the right-sized wheel and speed going, you'd have to run and jump at a "sideways" angle in order to go straight up to the hub.

To get to escape velocity, you'd need to decelerate and float to the center of your world.. Hubbward. You would be Orbiting without moving!

Or, you could mechanically climb the walls and chop your way out with an axe, then jump into the 5th dimension, never to return. Not knowing what force is sucking you away from the station.

Elevators moving from hub to rim would need swiveling seats otherwise passengers would get smashed against the anti-spinward wall as the elevator tube "scooped" them along and brought them "up-to-speed". Sort of like a never-ending slingatron!! Wheeeee....

Garbage disposal would never be a problem, you could have some super long tubes sticking out out of the habitat. And you'd dump your garbage into a hole in the floor. At the end of the tubes would be a bunch of thermocouples, As your garbage "falls" down the hole(tube), it generates enormous speed as it gets whipped around by the rotating station. And on impact at the farside/bottom it explodes like a meteor bomb. All that heat is fed to the thermocouples which in contrast with the -273c of space, creates huge electrical potential which powers some ion thrusters to make up for some of the angular velocity lost in accelerating the garbage along the way!

Now, what if we make the wheel 1 AU in diameter, for argument's sake, And we spin it up with a big motor. And what if we get 50% lightspeed linear velocity at the inside part. And say for argument's sake at the outer edge, we're supposed to get 2c or 3c linear velocity. What happens at the 1c "barrier" Does the monster-sized disc suddenly vanish into thin air? OR does it become incredibly dense? And thereby becoming super strong and perhaps even using it's own gravity to hold it together?? And if we slow it down, do the "disappeared" discs re-appear?

Now if we put two spinning parallel discs, each running in reverse, one spinning clockwise, and the other spinning anti-clockwise can we make a gravity field? Can we vary the strength and direction of the field by varying the disc rotation velocity? Can we phase and project gravity along the axis? Sure can!

Now shrink the solar-system-sized proto-type down into a box that fits on your desk. And has 6 sets of spinning discs. All with variable speed super-turbo motors making the edges of the discs run at light-speed.

With 6 sets of discs placed along each side of a regular box shaped box, we would project a force in any direction. That is called a spin-grav drive. That is how artificial gravity is made, or shielded against.

---------- Post added at 10:36 PM ---------- Previous post was at 10:07 PM ----------

Now imagine a Superluminal Slingatron! The only way to blast FTL ships out of the sky..

---------- Post added at 10:51 PM ---------- Previous post was at 10:36 PM ----------

5.39124e-44 s. Planck time - Wikipedia, the free encyclopedia

Ahh yes of course. I wonder, if the shortest unit of time measurable(or not) would simply be the time that occurs between the two states of an object. In this context "state" means a stationary object or particle and the other "state" would be motion of that particle.

A particle may be moving one moment, and the next moment it may be stopped, the time difference that occurs between starting and stopping would be far far smaller than PlanckTime. Thousands of magnitudes smaller.

 

[tblaxland]

A particle may be moving one moment, and the next moment it may be stopped, the time difference that occurs between starting and stopping would be far far smaller than PlanckTime. Thousands of magnitudes smaller.

:shrug: It doesn't matter, you won't be able to observe it, ergo it won't have any greater physical effect than if it slowed gradually down over 1 t_p. Contrast to the proverbial "tree falls in a forest" scenario, where the effects can be observed if not the event.

 

[ZombiezuRFER]

The whole water thing was just a very basic analogy. You could replace it with beads. By simply spinning the tube in space, do the beads stay on the inner surface of the tube? Friction wouldn't help much, as it cannot keep something "down." Even with air friction, just means the air is spinning. That does not generate the sensation of actual gravity.

 

[Artlav]

The whole water thing was just a very basic analogy. You could replace it with beads. By simply spinning the tube in space, do the beads stay on the inner surface of the tube? Friction wouldn't help much, as it cannot keep something "down." Even with air friction, just means the air is spinning. That does not generate the sensation of actual gravity.

Let's say you have a tube with a bead in it, and the bead is nudged towards the outer surface.
At some moment it would touch it, and would be sent flying spinwards.
Try to imagine what would it like seeing from the top - a bead going in straight line cutting across the tube.
The fact is, it would imminently touch the tube again, speeding up spinwards even more, and again, and again.
Eventually, it will come to rest relative to the tube, lying on the outer surface.

Then it's just like the water in the bucket you spin over your head and down.

 

[Keatah]

The whole water thing was just a very basic analogy. You could replace it with beads. By simply spinning the tube in space, do the beads stay on the inner surface of the tube? Friction wouldn't help much, as it cannot keep something "down." Even with air friction, just means the air is spinning. That does not generate the sensation of actual gravity.

Yep, And to prove it take apart a high-quality cd-rom drive that is vibration-less and plays discs with no mechanical noise.

On start-up these drives make a rumbly swishing noise that quickly becomes silent. That is a series of ball bearings being whipped around in a mini-centrifuge. The ball bearings even defy gravity, they crawl up the edge of the circular tube and "stick" themselves to the outermost possible edge or a toroidal shaped circular tube. Plenty of air friction and surface friction.

If you have a loud drive, it is of the cheapest possible mfg.

---------- Post added 02-28-11 at 12:03 AM ---------- Previous post was 02-27-11 at 11:58 PM ----------

Let's say you have a tube with a bead in it, and the bead is nudged towards the outer surface.
At some moment it would touch it, and would be sent flying spinwards.
Try to imagine what would it like seeing from the top - a bead going in straight line cutting across the tube.
The fact is, it would imminently touch the tube again, speeding up spinwards even more, and again, and again.
Eventually, it will come to rest relative to the tube, lying on the outer surface.

Then it's just like the water in the bucket you spin over your head and down.

What he said.. Or better yet! Go play with the washing machine in spin cycle. You can put some toy boats and subs in it to better visualize what is happening. The side-load horizontal ones with the clear window are cool.

You will see all the model ships bounce around and everything, simulating the high seas. But when spin cycle comes around. LOOK OUT! The high seas get all strange and soon enough you got a mini-RAMA going! The ships can sail upside down on land that automagically appears in the sky. Especially as the rpms build up!

 

[Carmen A]

Omg, more washing machine fun.

And I thought going past the lightspeed barrier was all about giving the Arrow freighter insane thrust levels and installing Goa'uld inertial dampers to compensate for the 1,200G acceleration

 

[Stoat]

There's always this footage which shows astronauts making their own 2001 flywheel. Another little oddity is zero g cookery It seems that a low rev rotating oven is best for roasting stuff. The sunday joint doesn't cook properly unless you can give the air a little g .

 

[marooder86]

For starters, you tell me what the shortest length of time is. Whether it be micro-seconds or atto-seconds.. Just tell me..

I think the question for start should not be, what's the shortest lenght of time, but what time as itself is or does time really exists at all? What if time is only some sort of abstracion created for purpose of perception by inteligent mind(us) and in reality does not occure in processes which rule the universe. Many so called paradoxes that we hear about have something to do with time violation which lead also to causality violation or at least it seems so to us, but mind can be tricky and people can be wrong about time. Errare humanum est.

 

[Keatah]

I completely support the notion that time is a human-invented concept to help us observe the universe around us.

To a physical object, time really has no effect on it. I tried explaining this to my 3rd grade teacher and kept getting in trouble for it.

 

[liber]

Only light travel faster than itself,light fired from one star and light from another star when their light path cross,I think speed encounter is double of speed of light. :blink:

 

[T.Neo]

If I was in a spacecraft travelling at 0.92 c, and I crossed paths with another spacecraft travelling at 0.92, the other spacecraft would appear to be heading for me at 1.84 c.

This is only apparent FTL. Just like how on Earth, the stars appear to be moving at many times the speed of light, while it is actually Earth rotating far slower than c and the stars are far away.

 

[Urwumpe]

Even considering quantum entanglement? I understand that sometimes particles are split apart at the event horizon of a black hole.

Even that. Quantum entanglement is actually some sort of gambling trick, not a real phenomena, in the sense that information is exchanged between the two particles. The information has to be exchanged between the observers for the experiment to make sense.

To stay with twins: if you and your perfectly equal looking twin enter two aircraft without ever saying who is who (Mr Keatah is enough), and one of both is then tested by asking for his passport, an observer at the other airport could with this information (Who was at airport A) tell, who arrived at his airport.

The whole complexity and magic of entanglement comes from the large number of particles that are exchanged, and the small size of the particles: you can't ask an particle for its passport, and if you want to do that with millions, it gets much harder.

The important difference: In that small scale, you can have this "If this particle is A+, the other particle has to be A-" relation. In classical physics, that wouldn't be the case.

 

[orbekler]

From our point of view, Light takes 8 minutes to come from the Sun, 4.2 yrs from Proxima Centauri and so on. By the Lorentz transformation, at the very speed of light the time dilation becomes 0, so, from the point of view of a photon, any trip to whatever distance takes time=0?

 

[Urwumpe]

From our point of view, Light takes 8 minutes to come from the Sun, 4.2 yrs from Proxima Centauri and so on. By the Lorentz transformation, at the very speed of light the time dilation becomes 0, so, from the point of view of a photon, any trip to whatever distance takes time=0?

Yes.

You could also say: From the point of view of the photon, we don't exist until it collides with us. The universe looks pretty dull at the speed of light. All you can see is an infinitesimal thin ray in front of you.

 

[orbekler]

Yes.

You could also say: From the point of view of the photon, we don't exist until it collides with us. The universe looks pretty dull at the speed of light. All you can see is an infinitesimal thin ray in front of you.

:hmm: So, light seems to be a kind of barrier that prevents that anything could happen at the same time...

 

[Urwumpe]

:hmm: So, light seems to be a kind of barrier that prevents that anything could happen at the same time...

Not light - but the vacuum speed of light. Gravity also propagate at this speed, it is the only speed at which a resting mass free particle (something that has only momentum) can travel. So, this includes everything that has no mass for propagating an event.

But to quote a wise man: Nothing travels faster than the speed of light with the possible exception of bad news, which obey their own special laws.

 

[Rtyh-12]

This is only apparent FTL. Just like how on Earth, the stars appear to be moving at many times the speed of light, while it is actually Earth rotating far slower than c and the stars are far away.

Only light travel faster than itself,light fired from one star and light from another star when their light path cross,I think speed encounter is double of speed of light. :blink:

Wrong. The speed addition at those speeds is different. You don't add them, but you use a weird formula. Basically you could have a train speeding at 99.99 % of the speed of light and another one going at 99.99 % too. If they both head towards each other, when they go next to each other they won't move at almost 2 c, but at a speed a little smaller than c (but greater than 99.99 % of c)