something that has really confused me

if say 2 cars ar tarvelling at 70mph and crash into each other then the combined speed is quoted as 140MPH a combination of the speed of both vehicles.

what will happen in CERN at the LHC when photon particles crash into each other at close to the speed of light. the combined crash speed cannot be double as nothing can travel faster than the speed of light?

cheers

Alan

But nothing is travelling faster than the speed of light, even though the effective crash speed is greater. Effective isn't the same as actual.

Tachyons FTW.

The speed of light c is fixed.

even relatively c is the maximum.

i.e. particle a is travelling at 0.99c clockwise and particle b is travelling at 0.99c anti clockwise.

When they collide they should impact with a relative speed of 1.98c (i.e. nearly 2 times the speed of light).

However, c is the maximum.

To get around this theorists suggest that space and time is therefore not constant. i.e. the protons will actually be travelling twice the distance (or double the time) relative to each other and there the c maximum is restored.

It's all a bit freaky if you ask me though.

Is the English language something else which confuses you?

Mark

He also has Cheeseburger .

I blame it on old age!!!!!!!!!!!!!!!!!!!!

Imagine the two particles are travelling in the same direction, is there anything confusing about their speed?

Isn't it just one of those 'mysteries' which is really just an illogical problem. Like saying what would happen if an unstoppable force crashed into an immovable object?

It's Einstein's Special theory of Relativity.

For a body approach the speed of light, time runs slowly compared to a body at "rest" and distances appear contracted. Space and time are warped, which may be why they call it "warp speed". From the point of view of either particle, the other is not moving very fast at all relative to environment.

Here's the maths:

http://en.wikipedia.org/wiki/Special_re ... velocities

Marvel Comics letter's pages cleared this up for me some time ago - the unstoppable force - it's apparently able to be deflected and redirected by the immovable object. (Juggernaut vs. Blob.)



Dependant upon where you are in the universe. The speed of light is not a universal constant.

Ahhhhhhhh That's completely clear now JJ

me too

I remember all this. Time dilations. Lorenz' contraction.

Special relativity was awesome to learn.

But remind me. What is the mass of these particles? Given that they are travelling close to the speed of light, their mass should approach infinity, right?

This is very compelling. Like MMGW, where we fixate on CO2 emissions and ignore the other greenhouse gases, the mantra that the speed of light is a constant needs looking at.

It may well be a constant in our local part of the universe, but we don't know if it can vary elsewhere. The assumption is it's a universal constant, but there appears to be a school of thought that says the speed of light can vary depending on where you are, and where you observe it. A variable speed of light might help answer many of the most awkward and frustrating questions about our cosmos.

(Sorry, went all Carl Sagan there for a minute. I'll be better after breakfast.)

The "two cars at 70" thing is a red herring - if you're in one of the cars, you still go from 70 to 0 - however the energy involved is greater than if you'd hit a stationary car - E= 1/2 mv2, plus the added effect of two crumple zones instead of one.

So, with the LHC, neither of the particles involved exceeds the speed of light but the energy involved in the collision is....a lot.