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what happens when 2 objects collide at the speed of light?
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PostPosted: Thu Jul 22, 2004 4:13 pm    Post subject: what happens when 2 objects collide at the speed of light? Reply with quote

Shocked has anyone ever wondered i feel that if you was in a car traveling at the speed of light . and you hit say a telephone pole would explode at an atomic level or would you pass right threw it....
or would you simple be absorbed or merge with thAT object?

i realize this might not intrest some or it might just be an old topic but it has made me ponder.....the pure nature of it all
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lg
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PostPosted: Sun Aug 01, 2004 6:41 am    Post subject: speed of light collision Reply with quote

I've been watching this topic, and noone's replied. I don't know the 'scientific' answer, but would there be much more than a puff of smoke and total disintergration?
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Hotrod



Joined: 22 Dec 2002
Posts: 74

PostPosted: Sun Aug 01, 2004 1:35 pm    Post subject: Reply with quote

I don't think you'll ever find pieces of those objects again.....
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PostPosted: Sun Aug 01, 2004 4:28 pm    Post subject: Light and matter collide Reply with quote

Guest,

This event happens more often then most people consider.
When matter is accelerated to light speed it becomes light by giving up it's latent energy into kinetic energy. There are particles of matter that travel close to light speed but because they are not quite to that speed yet they still posess mass and occupy space. Light on the other hand has no appreciable mass and does not occupy space as matter does.

So if a car accelerates to the speed of light (turns into light) and smacks into a telephone pole... some of the light(car) energy will be absorbed by the pole (in the form of heat) but most of it will be reflected off in different directions as visible and invisible light.
If this happened at night you would see the area around the pole light up as daylight, if it happened during the day you may not see anything.

The amount of light hitting the pole during the day by the sun would more than exceed the latent energy of any car mass at light speed.

So you see... you are observing that very event every second of every day and we only get to see a small fraction of the total output of our sun as it lights our way through a typical, boring day.

K
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Fred C.
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PostPosted: Tue Aug 03, 2004 5:22 pm    Post subject: Re: what happens when 2 objects collide at the speed of ligh Reply with quote

Anonymous wrote:
Shocked has anyone ever wondered i feel that if you was in a car traveling at the speed of light . and you hit say a telephone pole would explode at an atomic level or would you pass right threw it....
or would you simple be absorbed or merge with thAT object?

i realize this might not intrest some or it might just be an old topic but it has made me ponder.....the pure nature of it all


I have a problem with the "nature of it all". First off, wouldn't a car (as I understand them to be) burn up and disintegrate long before it ever approaches the speed of light (friction)? And even if the car could attain light status, what are the odds that it could hit the telephone pole without hitting something else first? I've hit a telephone pole before, going about 45 mph (0.0125 mps), and got away with just a bruised shin and a smashed fender. I would think that a car strong enough to go that speed (186,000 mps) would simply sheer the pole from it's foundation (at point of impact, snapping it like a toothpick) without much other damage to either party. If the car was strong enough to attain light speed, I doubt there would be any damage to the car at all. Explode? I doubt there would be any explosion, much less at an atomic level.
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PostPosted: Tue Aug 03, 2004 6:43 pm    Post subject: light car Reply with quote

Fred C.

Your quite right, at any integer of light speed the mass of the car would be menacing indeed. If the car achieved even %1 of light speed in the atmosphere it would burn like a falling star and fall into heaps of liquid metal.
But something very special happens to matter when light speed is reached, it must become light. It's mass and momentum must be converted to velocity, when that happens we observe it as light.

Do you feel the impact of sunlight on your face? The substance that made that light weighs hundreds of tons but was efficently converted from matter to light by atomic processes.

Re:Collision effects
At the point of impact equal damage would be done to both bodies, I think it's called a non-elastic collision. The higher mass object would pass through the pole but not unscathed. If the pole were more massive the car would take all the damage... which proves out your experiment nicely.

Glad to hear all is well after that one!

K
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rick1776



Joined: 20 Apr 2004
Posts: 17

PostPosted: Wed Aug 04, 2004 8:38 pm    Post subject: Errrr, help needed Reply with quote

I think the question was posed as a thought experiment rather than a real do-able experiment.

It has been many years since I did any relativity (or any real physics) but I still remember the odd bit here and there. Doing all those thought experiments used to hurt my brain and I let the really smart kids do all that stuff, while I was just happy to get the correct answers to non-relativistic physics questions.

Matter + energy can not be created or destroyed. One may convert from one to the other, but Matter+energy is conserved. Otherwise we're all in trouble and God doesnt exist, or He chooses to not obey the laws of physics which I suppose He must have created, but thats another story.

Lorentz transformations (heaps of stufff on the web if youre really interested) would tend to indicate that for an object possesing mass to achieve the speed of light you would need an infinite amount of Force to do so. In short, if you collected up all the energy in the universe and applied it to the object (having mass) you still couldnt get it to travel at the speed of light. (And thats a good thing I think, as it keeps the road toll down.)

What would happen as you collided with the pole. Well you would crash and die. Now if youre an accountant you would do an audit of the amount of energy and mass before the collision and then you would collect all the pieces after the accident. Remember the amount of enery + matter after the collision must equal the amount of energy + matter before the collision. By way of example you may end up with less matter after the collision, but then you would have more energy. Its a ying and yang thing.


"At the point of impact equal damage would be done to both bodies, I think it's called a non-elastic collision".

Youve lost me on this one?? Ok sorry I got you.

There are three types of collisions. Non-elastic, elastic and super-elastic.

You measure the kinetic energy before the collision, E = 1/2mv^2 and the kinetic energy after the collision and both are the same. This is an elastic collision. Example two hard ice pucks collide with each other.

You measure the kinetic energy before collision and then after collision. If you have less kinetic energy after the collision this is non-elastic. Example most car accidents. Or throwing putty against a wall. Kinetic energy is converted into a different form of energy and radiated. Usually as heat or light etc.

You measure the kinetic energy before collision and you have more kinetic energy after the collision. This is super elastic collisions. Thats the kind of experiments the smart kids used to do in our lab by shooting electrons into Lithium. Me, i was a lot more practically minded and designed the frequency doubler apparatus for the laser so that the smart kids could do their experiments.


cheers
rick1776
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PostPosted: Fri Aug 06, 2004 5:07 am    Post subject: Collision problem Reply with quote

Rick 1776,

Quite right, I'm glad to hear your professor's time was not wasted on you.
The problem with accelerating matter to a higher level of velocity is that it requires more and more energy (in whatever form) to get it to move any faster than what it is currently.
I'm sure you remember Newton's 1st law of motion.
As velocity builds so does momentum which acts like extra mass when you try to move it or accelerate it.

The E=mc^2 formula gives us the available energy in a given mass should it be fully liberated but it also infers that matter and energy are interchangable. Should light slow down it has no choice but to become matter, should matter be accelerated to light speed it must become light regardless of the energy used.
As I pointed out in a previous post the sun performs this majic trick of converting matter to energy constantly yet the sun does not posses infinite energy.
We have been told there is no such thing as perpetual motion but where do the electrons get there energy to orbit their nucleus endlessly?
My point being nature and it's wonders are greater than our ability to describe them and our understanding of math is not good enough to be able to even model them properly.

You may find Dr. Bearden's website of some interest.
http://www.cheniere.org/toc.html

cheers
K
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K.C.



Joined: 25 Jan 2003
Posts: 109
Location: Tucson, Arizona

PostPosted: Fri Aug 06, 2004 9:22 pm    Post subject: Reply with quote

I asked my spouse, who is a engineer for Raytheon, about this; he tells me that depending on the objects that are heading toward each other, his best guess is that there wouldn't be enough left after the crash to worth anyone's time.
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Klatu
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PostPosted: Sat Aug 07, 2004 5:56 am    Post subject: Just thinking Reply with quote

Kc,
Gotta love them engineers... for their practicality alone!

As Fred C. said this is a mental exercise not a practical experiment.

Another way to look at this is two sub-light objects travling at each other from opposite points... then as Fred C. describes one of three possible collisions would occur.

So what would happen if two idential lasers were pointed at each other. Would they pass through each other or cancel at the point of interference?

What would be effect if the laser light was in phase and then tested out of phase, two different effects?.

Since we know energy cannot be destroyed only translated to a different form, what would be the different form when they appear to cancel?

K
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Klatu
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PostPosted: Sun Aug 08, 2004 6:36 am    Post subject: Light collision Reply with quote

Hey Fred C.!

Since you have some laser experience, could you speculate on this conundrum?

My last post got me thinking about what would happen, under ideal conditions when two lasers beams intersected.

I would think that one of two things would happen:

If both lasers are of same frequency and set far enough apart so as to cause the beams to be in phase with each other that should create a place of interference where they meet, perhaps at the half distance point. At that point the waves would cancel but not being able to destroy energy, what would the applied energy turn into? radio waves?, longitudinal waves?

If both lasers are of same frequency and set far enough apart so as to cause the beams to be out of phase with each other, both lasers beams should travel back to the point of origin and create an interference zone within each other's mirror casing.
At that point although the lasers are working at full capacity both their outputs should appear to diminish.

Do you think diode lasers would serve as a good experiement? I know they don't work the same as chemical lasers but the interference zone at midpoint might be acheivable if the positioning precision can be performed.

Any ideas or actual results?

K


Last edited by Klatu on Mon Aug 09, 2004 8:16 am; edited 1 time in total
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guest
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PostPosted: Sun Aug 08, 2004 2:30 pm    Post subject: lasers Reply with quote

might they simply spread light, as if mashed against a barrier, to flow outward? like.......splat?
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Klatu
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PostPosted: Mon Aug 09, 2004 8:22 am    Post subject: Light collision Reply with quote

guest,

Yes, that is what would happen at the point of interference but the question is, where and under what circumstance would be the point of interference?
Whether they are in phase or out of phase may make all the difference at to where that point is.
Something totally unthought of may occur. Theory may predict what might happen but one experiment is worth ten thousand theories.... to me.

Please sign your comment so I know who to address.

K
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eddiet03
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PostPosted: Mon Nov 15, 2004 1:49 pm    Post subject: Re: what happens when 2 objects collide at the speed of ligh Reply with quote

i say if your car could travel the speed of light, you have a really fast car.. don't hit the pole, enter it into the NHRA... [/quote]
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Klatu
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PostPosted: Sun Nov 28, 2004 7:22 am    Post subject: Re: what happens when 2 objects collide at the speed of ligh Reply with quote

After some careful consideration of the intersecting laser experiment.

I came to the conclusion that should two objects collide (head on) at light speed a certain amount of interference would occur with waves of the same frequency and are in phase with each other, this would have the effect of cancellation. When the waves are out of phase (and at the same freq.), the opposing waves would travel back alone the same path their opposite originally took.
A majority of the waves (from both objects) would continue on their original trajectory.

When any physical object reaches light speed, it is light, not nessasarily coherent light (all one frequency) but many different frequencies because of its atomic makeup.

The angle of collision has alot to due the successful outcome of a collision at this speed.

Light does not propagate in a sinusoidal fashion (when viewed as a frequency), it does have a cork screw structure to it (3D).

You could say light is all screwed up, but that's a different topic entirely.

eddie03: I see the shock therapy is working... up the voltage!
Don't be embarrassed, I had shock therapy... it felt good when they stopped.... just kidding with ya eddie.

K
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