physics question

Hi,
Im not very familiar with physics or relativity. According to relativity:

mass=mass(atRest)/squareRoot(1-(velocity^2/speedOfLight^2)

So does this mean that a particle will have infinite mass if it attains light speed?

I'm no physicist but from my understanding it means that a particle which has mass (at rest) cannot reach light speed.

mass = mass(atRest) / squareRoot(1-1)
<=> mass = mass(atRest) / squareRoot(0)
<=> mass = mass(atRest) / 0
=> not defined (division through zero)

Thanks Xarthor,

"cannot reach light speed" seems more likely than "reaches infinite mass" so I guess I would agree. I am still sort of confused why a particle couldn't reach light speed, it seems that anything could reach light speed if it gets enough force. The fact that it is at rest or not at rest just seems to alter the amount of force needed. Do you know what I mean?

Also from a limits perspective,
limit of mass, as velocity approaches light is infinity. So thats where I came up with the idea of infinite mass.

Yep, theoretically, if mass could reach speed of light, its mass would become infinite. Well, if it could.

The reason why mass never can reach speed of light is that its mass is increasing if it becomes faster. The heavier it gets, the more energy you need to make it faster. So, if you want to make mass reach speed of light, you need an infinite energy.

mass=mass(atRest)/squareRoot(1-(velocity^2/speedOfLight^2)

when the velocity reaches the speed of light,
you get a division by 0.
The universe would crash and throw an exception

AFAIK sometimes you can say 1/0 = infinite, although it' mathematically wrong. At least I often read that the mass of an object becomes inifinte if it reaches speed of light.
But it doesn't really matter, because it never happens anyway :P

ahh yes, thats the key which helps me understand it and it makes sense: mass can never reach an infinite size because it would need an infinite force.

Well you can do it in certain aspects of math, like when looking at graphs of things, and for finding limits.

I don't know how they make compilers or the real technical reasons behind why you cannot divide by zero. Is anything even being attempted? In other words, say I write some code which divides 5 by zero, does the computer even attempt it?

If 20 / 2 is 10, you can safely say that "2 * 10 = 20".

Now you say 20 / 0 = X. Therefore 0 * X = 20. What value of X will satisfy this statement.

None as 0 times anything = 0. Therefore X cannot exist. Dividing by zero does not exist or mathematically undefined.

Another practical example is thinking that division is basically just a set of subtraction operations.
Eg, 20 / 10 means start with 20, then subtract 2, and again, again until you reach 0. How many operations did it take? >> 10.

Now think about 20 / 0. Start with 20, then subtract 0, and again, and again. You now see why some people refer to dividing by 0 as infinity.

Not sure how a compiler goes about dealing with divisions by 0. BTW what is a compilers take on roots of negative numbers? In maths we can define imaginary numbers this way easily, but how would you in a programming language?

From what I understand light speed is not exactly synonimous to 'infinitely fast', so travelling at light speed (or faster) should in fact be possible even in theory.

Obviously it would cost a tremendous amount of energy making it questionable if even trying to reach such speeds makes sense (with current day propulsion).

Perhaps in a practical sense it's even impossible to a. carry enough energy/fuel onboard needed to reach those kinds of speeds and b. have a space ship strong enough to withstand forces involved and carry the entire mass (energy today isn't exactly mass free). Perhaps travelling at such speeds is as problematic as conquering supersonic speeds in the old days (e.g. bending/deforming metal at highest speeds, old propulsion systems aren't able to reach supersonic speed and so on).

Don't forget a lot of the 'we can't do that' kind of thinking only makes sense with current day propulsions in mind.



True, but it remains a somewhat philosophical question whether it makes sense to agree upon the 'fact' that 0 times anything is 0. By the time science has discovered that nothing can produce something, the whole mathematical idea becomes a bit untrue, wouldn't you agree?

Cheers

For reaching the speed of light, you need an infinite amount of energy, so you CAN'T reach speed of light in theory.

AFAIK, if some object reaches speed of light, from the viewpoint of the object, the space between it and its destination becomes 0, and time is passing infinitely fast. So travelling in speed of time is like travelling in infinite speed. And if it was faster than light, it would travel back in time.

An other problem of travelling in speed of light is that the mass would become infinite. So the force of its gravitation would also become infinite and it would suck in the whole universe in 0 seconds.

Then what about the light itself?
AFAIK photons have mass, and they DO travel with speed of light. No division-by-zero and universe-sucking-cataclysms occur. Or probably it's possible because of the dual nature of light?

Photons have mass when traveling in speed of light (what they always do), but they don't have a rest mass. If they had one, they indeed would become infintely heavy, but they haven't

Photons can travel faster than light in Caesium gas.
But cant transmit the information Pulse faster.

But another question: if
something cant move faster than light,
you need to be shure, that lenght is fixed.
(1 meter = 1 meter)
But quantum physics state that there is no
definite values before you measure them.

So the distance to by travelled (speed = distance / time)
could at the case of your measuremnt be larger
than 1 meter, thus making the object
move effectively faster than you thought.

Thanks for the explanation. Quantum physics is illogical at a first glance, and this makes it even more intetersting.