# Strange faster than light question

Discussion in 'GD Archive' started by Busby, 30 May 2003.

1. Busby

# Location: Newport

Ok, here's a weird thought I just had about how to beat the theory that according to Einstien no communication can go faster than light.

Now prepare yourself for some pretty stupid threoretical questions

Imagine you had a peice of string going from earth all the way to mars and this string is pulled as tight as it possibly can without snapping.

Now imagine if someone on each end of the peice of string was holding it tight.

For "yes" one of the two would simply pull the string once and for "no" they would tug the string twice.

Would this not be instantanious communication? Obviously overlooking the sheer lunacy of the idea

Same type of thing where imaging you had Billions upon billions of metal balls right next to each other in a tube spread out thousands of miles. if you tapped the first ball, the last ball should move at exactly the same time which means it's beating the speed of light, is it not?

OK, get you head around that lot

2. daz

# Location: Bucks

The movement of the string would be carried by the atoms inside the string, this would take a certain amount of time with a string that long, and most certainly would not be instant or faster than light.

3. Mr Blonde

# Location: Liverpool -> London

I didn't do much in the way of physics but I don't think you would ever be able to pull the string tight enough, ie to the point just before it snaps for it to act like a solid rod. Indeed, a solid rod that long would have give in it anyway. Same for the balls, you'd never be able to get them touching each other perfectly to enable this either. There would also be a miscule amount of 'give' on the point each touched and this would be magnified by the number of balls in the link. That's my guess anyway

4. Ex-RoNiN

# Posts: 12,354

No mate, because the energy you use to hit the second ball with the first ball has to follow Ke=1/2mv^2, BUT Ke <= c, that is a given, a fact, it can't be changed.

On a small scale, when talking about 5 balls it seems as if it was instantaneous, but if you have many balls you can actually see the delay and the energy travelling.

# Location: Abilene, Texas

Ummmm well the string thing has nothing to do with something going faster than the speed of light or not. Communication cannot travel as it is not a thing. The movement of the string has a meaning (yes or no) but communication is not traveling. Nothing is going faster than the speed of light as all of the string is moving at exactly the same time each time it is pulled.

The metal balls thing I dont think works as well when you have billions upon billions. I am not sure but I think when you have one of those desk toys with the hanging balls and you let one go and it drops and make the other one go, it only appears to move the ball on the opposite end at the same time because your eye cant register the very short time they are both still. If you have billions upon billions then the energy from the first ball would have to travel through the billions of other balls to get to the one on the end. If we are assuming that no energy is lost in the travel than it would take time for the energy to get that far.

I dont know if what I said makes sense, if not then Ill retype it.

6. Grrrrr

# Location: Various

Another easier way of asking the same question

Firstly light takes 8mins to travel from the sun to earth. Now imagine you had a metal rod stretching from the sun to earth if you pushed the rod would the other end move instantly i.e. the light from sun would arrive in 8mins however the rod would move instantly therefore move faster than light?

The rod would move in a wave/compression like motion. The energy that each atom passes from each to the next (causing it to move) transfers at a speed slower than light.

Nice try though mate

Pete

OK get your head round this: as speed increases and becomes closer to the speed of light the mass of the object increases therefore more energy is needed to push this object. So in essance to make something move at the speed of light you need an infinate amount of energy. So what if the object has a negative mass? It cannot move at a speed less than light? This is the theory behind tachyons, AFAIK.

Confusing stuff!

7. growse

# Location: Ironing

For starters, you'ld need a distance large enough so you could measure it. Lets say 1 mile. Now you need to find a material, that firstly won't sag under it's own weight, and has a very high Young's modulus. Glass is probably the most suitable thing I can think of, but a mile long glass rod will break if only held at the ends. Also, no matter how stiff the material, when you poke or pull it, it does deform elastically. Therefore the "signal" of you pulling one end will travel down the rod at less than the speed of light and it will just stretch in the time taken for the disturbance to travel down the rod.

8. Raymond Lin

# Location: Wish i was in .Lethal's house

Why is it not possible to travel faster than light ? Light speed is just that, a fixed speed, surely you can go as fast as technologically possible, there shouldn't be any limit. And why can we beat the sound barrier and not the light barrier?

# Location: Abilene, Texas

E=MC^2

C=speed of light
m=mass of object
e=energy

The energy, e, required to move a mass m, is equal to the speed of light squared time the mass.

But as the speed of an object approaches the speed of light it gets heavier, dont ask me why. SO as it gets heavier more energy is required to make it go faster, then it gets heavier which means more energy, heavier more energy, etc but never actually reaching the speed of light because the amount of energy required would be infinite.

10. Grrrrr

# Location: Various

I will quote from 2 posts above yours:

Pete

P.S. waits in anticipation for georges (alphanumeric) post

11. Wainson

# Location: Nottingham

the mass of an object increases by a factor - g, say as you approach the speed of light like this:

M=gm
where M is the mass at speed s,
g is the multiplication factor,
m is the original mass of the object

g = 1/sqrt ( 1- ((v/c)^2))

The more mass the object gets (as it speeds up, that is), the more energy it takes to accelerate it), in other words - this is a vicious circle, which ends up in requiring infinite energy to get to the speed of light...

This is because of general relativity (or is it special relativity?)
In any case, it's because of Einstein's theories of relativity.

Last edited: 30 May 2003
12. pyro

# Posts: 16,167

right, suppose you are in this super-ultra-long tube, which was magnets and inside it a metalic object which is "flying" due to the magnetism. now, if you supply enough electricity to these magnets (suppose they are electromagnets) in order to keep the metalic obect stable, at very high speeds, wont its weight issue be solved?

13. Busby

# Location: Newport

Yea that's what I figured

Thanks for the replies guys.

Back to the shed I go to watch more Science for Dummies by proffesor frink

14. Wainson

# Location: Nottingham

The weight issue will be solved, but the mass is still there (weight is a force acting on the mass, which you'd be solving with the magnets). The weight of an object doesn't affect the equations mentioned - only the mass, unfortunately.

15. daz

# Location: Bucks

As your speed approaches C, your mass increases exponentionally. Thus, it becomes more and more difficult to accelerate further. If you take it to its logical conclusion, to travel @ light speed, a massive object will become infinitely massive and thus will require an infinite amount of energy...

# Location: Abilene, Texas

mass and weight are two seperate things. Weight is a measurement of force that is acting on a mass.

17. Morat

# Location: Versailles

Einstein was a criminal for locking mans thought down.

Fortuantely he is becoming more and mroe discredited.

He was still a great mind, but with all great minds, they generate biased theories.

It was also proven that the Human body would be crushed if it travelled over 60 mph.

Then later it was proven that Travelling at the speed of sound was impossible.

As science advances, thing previously proven impossible by people with an antiquated understanding of physics are disproven.

it is best to keep an open mind, than believe everything you are taught as "fact".

18. daz

# Location: Bucks

I'm sure AlphaNumeric can PROVE that anything with mass cannot travel at the speed of light, or even faster than the speed of light.

Yes, it's good to keep an open mind - but there are certain laws of physics that are pretty much set in stone. A lot of Newton's stuff is still applicable today. His gravitational law may have been found to be not accurate in certain instances, but in 99% of cases, his 400 year old theories on gravity still hold and describe the movements of the earth, the planets, the moon and the sun.

# Location: Abilene, Texas

Thats what I think too. I think eventually we will be able to but we cant yet.

Its funny because I said pretty much the same exact thing in one of my physics lessons and EVERYONE flamed me. It was funny