OT: Faster than the speed of light?

Submitted by MeanJoe07 on

So I found this question and it really interested me especially after watching Interstellar. Can someone answer this for me?  I'd like to build a time machine by going faster than the speed of light.  

If I built a railroad track that circled the earth in a straight line, then put a train on that track so long that the first car could connect to the last car (making a full circle around the world). This train can go 100 mph. This train also has a set of tracks on top of it with another train (that circles the world) riding on them, this other train can go 100 mph, so relative to the ground it is going 200mph. This 2nd train also has a set of tracks on top of it with another train on them that can go 100mph, and so on and so on...

when we get thousands of trains out one of the trains eventually reaches the speed of light and it can no longer go faster, but the train that is on top of that one would just be standing still? It would only have to be able to move itself at 1mph to be going faster than the speed of light. Each train relative the the one below it only needs to move incrementally faster, what happens to train above the one that reaches the universal speed limit?

DISCUSS & HARBAUGH

 

EDIT: Let's assume the trains are powered by Dilithium extracted from Denard. Sorry Denard.

Gameboy

May 14th, 2015 at 5:10 PM ^

No, that does not matter.

The bottom train has to spend more and more energy as you add more trains on top. Just because you keep adding trains to the top does not mean that there is no effect on the lower trains.

Even if you were to build trains of infinite strength, the amount of energy required to move with each additional train would be so much (it would approach infinity as you get closer to the speed of light) that the top train will never be able to go as fast as the speed of light.

Mgoscottie

May 14th, 2015 at 6:03 PM ^

I'm a high school physics (chemistry really) teacher.  You could get things to travel 100 mph relative to one another 3 million times, they would just still not be going faster than the speed of light.  If you have a planet traveling .6c away from us one way, and another planet going .6c the other direction, they are not traveling 1.2 c from each other.  I don't remember the math on how fast they'd be but it's not additive in the traditional sense.  

Gameboy

May 14th, 2015 at 7:46 PM ^

That is because they are travelling at speed of light from all respective reference.

The third party will observe that both objects are travelling at .6c.

The first object will observe the second object as travelling at less than c relatively and vice versa. Theory of Relativity governs all this.

icactus

May 14th, 2015 at 12:26 PM ^

I am not qualified to talk about this in any way shape or form.

HOWEVA,

The stacking of trains idea sounds to me like a red herring.  If the trains are building off each others' speed then the bottom train is going to have to work harder each time you stack a train to carry the extra weight. You might as well just skip the stacking part and make an engine that will go 100mph and then keep adding engines to that one train until it is going faster than the speed of light. At that point I believe you hit a limit where you cannot make the train go any faster no matter how many engines you add.

Space Coyote

May 14th, 2015 at 3:54 PM ^

And I guess you could say I made that pun on PORPOISE, whether you find it a-MOOSE-ing or not.

But really, I was just PANDA-ing the "Koala" and "Bear" jokes. I know it's the POLAR opposite of funny. I'm sure the demise of this topic will come to a GRIZZLY end. SUN of a gun, if I could, I'd GOBI someone else with better jokes. But I can't get Kodiak into a joke, so sorry.

thatonekid

May 14th, 2015 at 12:29 PM ^

Just to give an example, if you have a train going at .8 times the speed of light, and then relative to that train there is another one going at .6 times the speed of light faster, then the speed of the faster train is calculated as (.8+.6)/(1+.8*.6) the speed of light, , which is 1.4/1.48 times the speed of light, and no matter what numbers you plug in the result is always less than 1 times the speed of light.  The reason that at low speeds if you are going at 10 mph and someone is going at 20 mph relative to you, then there final speed ends up being 30 mph because the denominator is practically exactly equal to the speed of light.

Source: modern physics class

Kalamablue

May 14th, 2015 at 12:30 PM ^

i'm gonna answer this.

 

While I am by no means an astrophysicist, I did use a telescope once.  The overall theory of your question isn't dumb, although your application of it could be refined.  The challenge you have posed is a matter of energy generation and element friction.  

 

To simplify your question, let's say your question is the following:  "If I have a rocket in space, can't I just keep accelerating it till we hit light speed?" .  Two problems with that:

 

1)  Where do you draw the energy from?  Purely on paper, and only using inputs of energy source input and ouput, sure you could get it going pretty fast.  But what about the actual mechanics of the engine?  How could we prevent it from overheating and falling apart? 

 

2) Friction.  Even in space, there are minute particles that when traveling fast enough will encounter friction.  The mass of an object traveling the speed of light would most likely encounter enough friction to have it disintgrated along with everything in side of it.  

 

 

Toasted Yosties

May 14th, 2015 at 12:29 PM ^

Except it was a giant windmill with windmill blades that extended millions of miles in space. At some point down each  rotating blade you'd have to be going faster than the speed of light. Part of the blade would be going slower, part at, and part faster than the speed of light. I'm sure it'd be impossible to create a blade strong enough to do so, but just sayin'.

iPhone

May 14th, 2015 at 12:34 PM ^

I wish traveling at the speed of light or faster is possible (or will be possible), but it isn't and never will be. Star Trek is great, don't get me wrong, but I just don't ever believe that kind of technology will be created.

saveferris

May 14th, 2015 at 12:56 PM ^

That's a pretty short-sighted comment.  100 years ago people would've said the technology behind your username would've been impossible.  Humans civilization has only existed for about 8,000 years and see the progress that has been made.  Imagine what could be achieved if human civilization endures on a timescale of epochs (i.e. tens of millions of years).

Also, FTL travel is theoretically possible within Relativistic Physics.  You can't travel faster than light through space, but there is no limit on how fast spacetime itself can move, which is the basic idea behind a warp drive.

RGard

May 14th, 2015 at 3:09 PM ^

We've had homo sapiens on this planet for 120,000 years and we only get around to making civilization after 112,000 years?

Also, we have Göbekli Tepe in Turkey that has been dated back to 10,000 BC (12,000 years ago) and that place needed civilization to get built.

gpsimms not to…

May 14th, 2015 at 6:18 PM ^

The universe has been around for almost 14 billion years. The Earth has been around 4.5 billion years. The sun has another approximately 5 billion good years left in it.

Considering how far life has come on Earth (from not existing to literally teeming with unbelievable biological diversity) and moreover considering how far life has come in the past ~100,000 years, it is not absurd to think that sometime in the next 5 billion years humans could figure out how to master the entire energy of our galaxy and be traveling throughout the entire universe in ways you or I never imagined.

FreddieMercuryHayes

May 14th, 2015 at 12:58 PM ^

Eh, it probably will be possible, we just have to figure out how to fold space efficiently. I mean, yeah, that's a tall task, but at least that would make it theoretically possible to travel faster than the speed of light (relatively) unlike the scenario in the OP that would be impossible by math and physics.




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MGoneBlue

May 14th, 2015 at 1:00 PM ^

Gravity can affect time (relativity links space and time together.)  For instance, the clock in GPS sattelites have to slightly correct themselves because they're much farther from the center of the Earth than we are.  Now multiply that factor by a huge number (black holes are really massive,) and you have the time dilation of being near a black hole.

Michael

May 14th, 2015 at 2:03 PM ^

If I'm not mistaken that correction has to do with the speed of the satellite in orbit being faster than the speed of someone standing on the surface. The same principle would apply if you placed a clock on an extremely tall tower - the top is rotating faster than the base.

These are two different principles at work here. Says that guy who's never taken physics, anyway (me).

Zarniwoop

May 14th, 2015 at 1:17 PM ^

http://physics.stackexchange.com/questions/25759/how-exactly-does-time-…

Basically, the curvature of space-time is so great near a black hole, that the distance between three-dimentional points in space is actually much larger than in an area where there are no massive gravitational anomolies. This is because space isn't really three dimensional when relativistic effects come into play.

Never

May 14th, 2015 at 1:18 PM ^

"Understand how a black hole warps/curves space time.Taking this into consideration, a beam of light has to travel a greater distance the closer it is to a black hole. On the other hand, light will continue to travel at speeds of 300,000 km/sec to an observer within that gravitational field - so time will go more slowly for that individual as compared to someone outside that gravitational field (per the time/distance relationship of speed)."
 
That applied to Brand and Cooper from Interstellar, who returned to The Endurance to find that Romilly had aged 23 years. Time for them slowed down relative Romilly who was outside of the gravitational influence of Gargantua.
 
Have heard that it may be easier to visualize space as a blanket, and planets/planetoids/stars as dropped objects on the blanket. The heavier the object, the stronger the "influence" it will have on say...a penny rolled towards it. Same effect on a beam of light.

Dix

May 14th, 2015 at 12:38 PM ^

I don't think the second train will be moving two hundred miles per hour relative to the ground. The track underneath the second train is moving backwards relative to the second train at 100 mph. Wouldn't it have to accelerate to 100 mph just to stay in one place relative to the ground?




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DualThreat

May 14th, 2015 at 12:46 PM ^

Time would slow down more and more for each successively faster train, also preventing a train from reaching the speed of light as viewed from any reference frame.

Nitro

May 14th, 2015 at 12:47 PM ^

I haven't taken a physics class in decades, but it seems like, if there's no track friction, the 2nd train would have to be able to go 200 mph on it's own.  And if there's enough friction for the 2nd train to be moving with the track at 100 mph when it's standing, that would seem to require that much more for the 2nd train to go 100 mph relative to the track.

Wisconsin Wolverine

May 14th, 2015 at 12:56 PM ^

I don't know much about light-speed travel, but I can think of one reason why the trains couldn't get us there.  

Each higher level of train that's moving faster in a circle would need to keep a firm hold of the rails below it to continue moving in a circle and not go flying off into space.  I think this friction would prevent a high train from reacing light speed, and also the whole setup would probably get ripped apart by the extreme force.

There are probably more fundamental reasons why the trains would fail to reach light speed even in theory, and others in this thread have generalized the problem to other, simpler settings (like a rocket in space).

This is not my area of expertise, but it sounds like there's a trade-off between mass and energy with regards to reaching really high speeds - as we approach the speed of light in a ship that has mass, each equivalent increase in speed (say, 1% of the speed of light) requires a much greater investment of energy to attain.  So, going from 10 to 11% requires far less energy than going from 95 to 96%.  Apparently, the physicists say, this energy investment per unit mass reaches infinity at light speed, such that no mass-ful object could do it.  Therefore, the only way to travel at the speed of light is to shed all your mass and become a photon.

Physicists, what say you?  If I'm gravely mistaken, please let me know.  I only just read about this today.  And I haven't seen Interstellar or stayed at a Holiday Inn Express recently.

 

Zarniwoop

May 14th, 2015 at 3:12 PM ^

That won't work.

As an engineer and a physics buff, this is very inspired, but your assumption that you can keep adding 100 mile per hour differences is flawed.

Also, even if it did work, your train would go shooting off into space at best. The heat from a train going the speed of light (assuming it didn't instantly incinerate) in the atmosphere, would be... large.

Large as in render the planet lifeless.

aratman

May 14th, 2015 at 1:01 PM ^

This is how a large scale accelerator works.  They have a loop that the particles move in and smaller energy loops.  It is not a train, as the energy to move something that large is currently unavailable. But we can move electrons and even some ions close to the speed of light,  It takes alot of evergy to change a little bit, a tube TV set is an accelerator that moves electrons close to the speed of light, the LHC at CERN in Europe that is LARGE gets the material closer to the speed of light, but even then doesn't break it.