Are there any physisists on the forum?

[TheDoctor]

Apologies for spelling it incorrectly.

Anyway.

The supplimentary is this: The CERN device, the LHC, will be crashing protons or lead ions into each other in an attempt to discover the Higgs Boson.
Two beams will be travelling in opposite directions at 99.99% of the speed of light. 001% shy of the magic 'C'.
Each beam of particles travelling at 99.99% the speed of light

From what you say the closing speed of the particles still be less than the speed of light ?

Will the closing speed be closer to 'C' by 99.99% of the missing .001% ?

Is that tiny, amount of extra velocity important? Could they not simply fire a beam of particles across one accelerated beam at 90 degrees?

Don't ask me why I got to pondering this because I have no ******* idea at all.

The closing speed could indeed be faster than lightspeed - but nothing is actually moving faster than light.
Imagine a couple of 2CV6s, going flat out at 70 mph, towards each other. The closing speed is 140 mph, but we haven't magically doubled the speed of a 2CV6!!! Each one is still only doing 70mph.

 

[661-Pete]

Not quite right, Doctor.

In fact, when you apply relativity accurately, what transpires is that velocities do not just 'add up' in the common sense manner that you might expect. For instance, in your analogy about two 2CVs (or any other cars), if each car is doing exactly 70mph relative to the Earth, their closing speed (the speed of one car, as measured by an observer in the other, will be not quite 140mph.

The actual closing speed (139.99999.... I can't be bothered to figure out how many '9's mph) is so incredibly close to 140mph that on this scale it makes no odds. Think of this as an analogy. Consider the rate at which each driver's toenails are growing. That will be considerably greater, than the difference between the cars' closing speed and 140mph. Therefore, the two sets of toenails are actually closing in on each other at slightly more than 140mph, notwithstanding the relativitistic adjustment.

But when you get to velocities very close to light speed, the discrepancy becomes far more significant (the actual formula is V = (V1 + V2)/(1 + V1*V2/C^2) for those who want to know). So it is possible for two protons to each be travelling at 0.99c relative to the Earth, yet their closing speed is still less than c.

It's all in the equations. Not sure if I've explained this very well, but I'm trying...

 

[colly]

Not quite right, Doctor.

In fact, when you apply relativity accurately, what transpires is that velocities do not just 'add up' in the common sense manner that you might expect. For instance, in your analogy about two 2CVs (or any other cars), if each car is doing exactly 70mph relative to the Earth, their closing speed (the speed of one car, as measured by an observer in the other, will be not quite 140mph.

The actual closing speed (139.99999.... I can't be bothered to figure out how many '9's mph) is so incredibly close to 140mph that on this scale it makes no odds. Think of this as an analogy. Consider the rate at which each driver's toenails are growing. That will be considerably greater, than the difference between the cars' closing speed and 140mph. Therefore, the two sets of toenails are actually closing in on each other at slightly more than 140mph, notwithstanding the relativitistic adjustment.

But when you get to velocities very close to light speed, the discrepancy becomes far more significant (the actual formula is V = (V1 + V2)/(1 + V1*V2/C^2) for those who want to know). So it is possible for two protons to each be travelling at 0.99c relative to the Earth, yet their closing speed is still less than c.

It's all in the equations. Not sure if I've explained this very well, but I'm trying...

So would that go to explain why things actually come in contact with one another?

As in: I throw a dart at the dart board and, in theory at least, it will never arrive, because no matter how close the dart gets to the board there will always be a half way point between the dart and the board.

The half way point will diminish and the time taken to cross that distance will get ever smaller but there will always be a halfway point.

 

[661-Pete]

So would that go to explain why thigs actually come in contact with one another?

As in: I throw a dart at the dart board and, in theory at least, it will never arrive, because no matter how close the dart gets to the board there will always be a half way point between the dart and the board.

The half way point will diminish and the time taken to cross that distance will get ever smaller but there will always be a halfway point.

Well, that's another interesting topic, but not quite the same thing. Yours is another version of the 'hare and the tortoise' paradox ('proving' that the hare never overtakes the tortoise: the hare starts 100m behind the tortoise: the hare runs 100m but the tortoise walks 1m further; the hare runs that 1m but the tortoise is still 1cm ahead ... etc. etc.). Alas! Once you understand converging geometric series properly, the hare has no difficulty in overhauling its reptilian friend...

And your dart will hit the board. Unless of course you are that inept player featured in An American Werewolf in London...

 

[marinyork]

That's a slightly different question though.

I think Einstein's General Theory attempts to answer that, although it's pretty incomprehensible to the lay person.

I'm not sure a theory of quantum gravity has been robustly tested (unlike Einstein's General theory which predicted things which have been proven)

At this point the question is too difficult for me and I'm off to bed

Quantum Gravity as was originally meant just doesn't work. You start with the famous einstein field equations, use CoV on it, get a lagrangian out. Treat it as a field, chuck that lot in to the probability gravity going between two points and you get an integral with a zero in the denominator . What you do about this problem is then what all modern books are about - fiddling around with the wrongly named beta function or symmetries which is where all the wacky brane stuff and screwed up balls of paper come in. Quantum gravity is fairly meaningless as a term thesedays. So anyway nobody really knows what gravity is although you get these speculations about why gravity is weak such as doughnut dimensions, showerheads and gravity off doing its own thing whilst everything else is stuck on a projection.

As for testing QG or a theory of it things tend to general relativity or if you could get those sorts of energies you're then left with the same set of problems.

 

[661-Pete]

From what you say the closing speed of the particles still be less than the speed of light ?

Will the closing speed be closer to 'C' by 99.99% of the missing .001% ?

Using the forumula, I figure out that the closing speed will be:
99.99999949994999750000001250125% of 'c'. Still short of the magic 100%!

 

[661-Pete]

OK, a 'supplementary' of my own, if people will bear with me. It is often blandly asserted that Relativity tells us "nothing-can-travel-faster-than-light". This is not strictly true. So: what can travel faster than light?

OK I already know about the Starship Enterprise, the Millennium Falcon, etc. etc. I'm looking for other examples!

 

[Crackle]

Battlestar Galactica

 

[rich p]

OK, a 'supplementary' of my own, if people will bear with me. It is often blandly asserted that Relativity tells us "nothing-can-travel-faster-than-light". This is not strictly true. So: what can travel faster than light?

OK I already know about the Starship Enterprise, the Millennium Falcon, etc. etc. I'm looking for other examples!

Billy Whizz?

Sorry, Pete, I don't know

 

[Jim]

I have very limited knowledge in this field but came across this the other day...

http://www.sciencedaily.com/releases/2010/01/100126175921.htm

They use the word 'seem' a lot

 

[philipbh]

Is it too late to introduce Cerenkov Radiation - which travels faster through insulating mediums than the speed of light through the same medium.

 

[XmisterIS]

Colly - Pete has answered your supplementary question correctly!

The important algebraic bit is something called the Lorentz Factor, which is typically denoted by the lowercase greek letter Gamma and is given by 1/SQRT(1 - v2/c2) where v2 and c2 are respecively the squares of speeds of the object and light and the function SQRT returns the square root of its arguments.

OK, not wanting to sidetrack from the long-awaited colly supplementary question but surely the answer is only as correct as current thinking and knowledge allows it to be.

Surely 'something' could be faster than the speed of light?

You need a philosopher to answer it properly not a physicist

No. Here's why:

Let the rest mass (i.e. the mass of an object A at rest in an inertial reference frame) be m0 and let the speed of an idential object B relative to A be v, and let the mass of B be m.

By the law of the conservation of momentum, it can be shown that:

m = m0/SQRT(1 - v2/c2)

Hence m becomes infinite as v approaches c and so to accelerate object B such that it reached a speed of c in A's inertial reference frame would required an infinite amount of energy.

So clearly, you can never get to the speed of light if your rest mass is not zero! That being said, 0/0 is a singularity ...

 

[velocidad]

this is great, thought i was the only one interested in this type of stuff . well there's no doubting my interest and enthusiasm for the subject, just a shame i'm not brainy enough to understand it ;-)
good books i've read are....'about time' by paul davies, 'how to build a time machine' same author, 'breaking the time barrier' by jenny randles, 'parallel worlds' by michio kaku, 'the never-ending days of being dead' by marcus chown.

 

[MichaelM]

If any of you geeks are genuinely interested in this stuff, I've got the course materials for the O.U. course "Space, Time, and Cosmology."

Without a doubt the most unrewarding experience I've ever had the misfortune to have to endure - I hated every minute of it - but it does cover mechanics, transformations, Special & General relativity, and Cosmology.

After this course I still don't know anything about relativity or cosmology, but now I don't care that I don't know.

It would cost abot£15 to post the lot if anyone wants it.

 

[marinyork]

OK, a 'supplementary' of my own, if people will bear with me. It is often blandly asserted that Relativity tells us "nothing-can-travel-faster-than-light". This is not strictly true. So: what can travel faster than light?

OK I already know about the Starship Enterprise, the Millennium Falcon, etc. etc. I'm looking for other examples!

If a particle had imaginary rest mass.

Spacetime itself.

If you had some different geometry it might appear so.

But none of these break relativity.