Faster than Lightspeed Collision?

Here is something that I placed once upon a time on another board for people to ponder:

If two objects of equal mass were both traveling at just under light speed, and they have a head on collision, What happens?
(Note: This would be the equivalent of a +Lightspeed collision with a stationary object.)

Or if they travel both Faster than light speed and collide head on what happens?

If you can answer it, good

Please Register or Log in to view the hidden image!

If you can't, then answer what you think would happen.

 

Log in or Sign up to hide all adverts.

Log in or Sign up to hide all adverts.

Okay I should rephrase,

You the observer spot two objects of equal mass collide, both objects were travelling at just under light speed (meaning the collision total is faster than light).

I also mention the other also refering to the same, but fast, of course you'll mention that impossible, I would say it's improbable, and that to travel at faster speeds you would suffer a paradoxal problem which can only be speculated through some of Schrodingers Thoughts.

 

Log in or Sign up to hide all adverts.

Hi Stryderunknown,

You're mixing up two things here. You're using a statement from special relativity (lightspeed) and a classical Newtonian addition of speeds (V_total = V₁ + V₂), which is not allowed.

The correct reasoning would be:
1) From a classical Newtonian mechanics stand:
The two particles collide, one with V₁, the other with V₂, so the total collision speed is V₁ + V₂. The particles emerge with their respective velocities. In classical Newtonian mechanics, no particles can be destroyed or created. The collision is determined by the conservation of momentum.

2) From the point of view of special relativity
The two particles collide, with a total velocity V = c²*(V₁ + V₂)/(c² + V₁* V₂). This formula can be deduced from the postulates Einstein formulated to write his theory of SR. In the case of SR, the creation and annihilation of particles is allowed, so here (depending on the exact velocities) you'd probably end up with loads of kinetic energy being converted into streams of particles.

Bye!

Crisp

 

Stryder, I remember when you made this same post at thepark. I wish I could have answered it with the details crisp did but it seems that he answered in escence the same as I did way back when

Please Register or Log in to view the hidden image!

The velocity of the two objects do not add up to faster than light speed just because they are travelling towards each other.

The power of the impact of the objects will be dependent on the velocity combined..

 

Reign,
It was actually the Prophet that brought the topic up at the park, but I couldn't resist reposting it here as it was a kind of fun topic. It wen't along with his whole "If Itravelled faster than light for a year..." kind of post.

I did have some fun with Crisp's calculation though it would see everything is virtually 1 with it.

Please Register or Log in to view the hidden image!

(I tried it with equal velocities.)

 

All I know is that if a ship traveling at one-tenth the speed of light hit one gram of matter, the resulting transfere of energy would be equivlent to many nuclear bombs detonating.

 

Request for elaboration.

Suppose, for example, one observes relatively to him a solid mass moving with the velocity of almost the speed of light in the direction x enters a gas moving with that speed in the direction -x. Would that mean that they would go back in time because as a particle approaches the speed of light, time ceases to exist and they would be going at a speed more than that of light relative to each other?

With this in mind, further suppose a container with a circular hole of area πx² in its front, filled with a gas and containing a solid sphere of volume (πx^3)/6 inside of it (to avoid friction between the object and the hole), is moving through space (no-gravity vacuum) at almost light-speed. Further suppose the solid is accelerated to a large speed before it exits the gas through the hole in the front of the container (for example, like a bullet is accelerated through a gun; more sophisticated acceleration techniques, such as matter-antimatter reaction, are possible). Upon exiting the gas, would the sphere go back in time, because it would be going at a speed greater than that of light (for the same reason as above)?

Now then, I realize that the formula above in this thread tells the resulting speed of the sphere. However, I would think that mass would have to do with it too: because shooting off two objects of mass x each should produce the same effect as shooting off of one object of mass 2x. So what is the formula with the mass included?

 

They do this in particle accelerators. Particles traveling in opposite directions at relativistic speeds are caused to collide.

it is difficult to do it with larger objects.

 

Question.

So have they not collided, say, an electron with a proton, and figured out the formula with the mass included thence?

 

This is pretty much exactly what happens millions of times a day at FermiLab.

No.

 

the same thing would happen as happens when you turn 2 flashlights on eachother.
seeing as light has mass, i dont see a dilemma here.

 

Light does not have mass, The Devil Inside.

The photon is massless.

 

Light doesn't have mass, but it does have momentum.

Actually if you shine two very bright beams of light at each other, there is a chance of a photon/photon collision which would result in the creation of an electron/positron pair;
http://en.wikipedia.org/wiki/Matter_creation

 

seriously?

Yes, as long as the photons both has 511 keV of kinetic energy.

 

You should note that he is wrong to call those gamma ray photons "light" and more gererally, I think they need only total slightly more than 1022Kev in your frame. -The total energy in your frame being the rest mass of two electons plus their "post-creation" kinetic energy. I.e. in some other frame, where the produced electron & positron are at rest, one gamma is downshifted and the other blue shifted to be equal in energy (511KeV each).

I am not sure but think it is possible that other slightly higher still total energy in you frame may be possible if the gammas do not collide "head on."

I think I got that right, but will defer to your corrections, if needed.

 

511 KeV annihilation radiation is routinely produced, on a daily basis, in medicine in hundreds of locations around the globe. Positron emitters are produced in quantity (Curies) in medical cyclotrons worldwide, and shipped to hospitals/clinics for injection into patients, who are placed under PET or PET/CT equipment, which detect with scintillators the two 511 KeV photons produced when the positron emitted collides with an electron, allowing for an ability to locate where the positron emitter was located in the body, visualzing various biochemical activities. You can learn more about that at www.snm.org

The reverse process is not as common, but has been done in laboratory settings, in which high-E photons are forced into producing electron/positron pairs.

And yes, BillyT is correct, the photons need not be head-on collisions, though it would require a higher energy (to conserve momentum). The annihilation photons are at 180 degrees in their rest frame, conserving momentum.

 

No I think you are exactly correct. I have not studied the process in any great detail---I'm more interested in much higher energies

Please Register or Log in to view the hidden image!

 

I believe I have a similar quistion like stryder. Let's say that a single atmos travel at 99,9999999%of c but this time it is aproaching a black hole. Let's say that their is no spin because it's going afther 1 of the poles in a straight line head on collision.
Now at the same time there is artificial wormhole with a enormous event horizon that is going to move our black hole to a save location.

The particle enters the event horizon of the black hole but the black holes singularity is transported before the particle could collide.

Will that particle move fasther then light or would it have been destroyed the second it (or before) enetered the black hole events horizon