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An Impact at a Relativistic Speed


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2 minutes ago, Alien 13 said:

The online calculators I saw wont let you input C the best I could get was 0.9999999999999999 C, the energy released compared to 0.99999999999999 C was huge.

Alan

Yes, it increases more dramatically as you get closer to c

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4 minutes ago, Corkeyno2 said:

Yes, it increases more dramatically as you get closer to c

'Dramatically' mght be the understatement of the year...

Olly

Edit: Even in dramas like Macbeth and Hamlet  not everyone is dead at the end. :D

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6 minutes ago, ollypenrice said:

 no massive body can get anywhere near 0.999C

Ummmm, I dont wish to nit pick (do I, harhar !) but any body with a non-zero rest mass is in fact massive, by definition, soooo many massive particles do regular get well up into the 0.99999etc region many places including CERN.

 

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Just now, Alien 13 said:

I you could achieve C would the energy from a gram of matter or even a single neutron be infinite? that was the feeling I got using the calculator.

Alan

it would be, but at the speed of light, the entire length of the universe would be decreased to zero. so hitting a particle would be the least of your problems XD

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I know that any particle with mass cant accelerate to C but isn't there the possibility that if by what ever means in the early universe some particle were already in excess of that speed then it wouldn't break any rules.

Alan

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1 minute ago, Corkeyno2 said:

its because of mass increase isn't it? you'd need infinite energy to move when you have infinite mass

Yes sort of in the vernacular I suppose, but one should not talk about if,  when and needing, at, etc. because you cant ever. To be rigorous you need to approach it in little bits and talk asymptotically.

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3 minutes ago, SilverAstro said:

Ummmm, I dont wish to nit pick (do I, harhar !) but any body with a non-zero rest mass is in fact massive, by definition, soooo many massive particles do regular get well up into the 0.99999etc region many places including CERN.

 

I meant ( well I didn't but harhar :D:blob6:) a human body. Or at least a 'body' such as might be sojourning in the OP's hypothetical spacecraft. One wth more pointed ears, that kind of thing. The body that is, not the spacecraft...

Having suffered the consequences (permanet) of hitting the tarmac while falling off my bike at an entirely non-relativistic velocity I firmly counsel the spacecraft pilot to slow down.

:confused2:lly

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1 minute ago, ollypenrice said:

I meant

:D  yes I knew well what you meant, massive in the English sense, you being, in a previous life, a being, a species even, that I used to hate ( an English teacher for the info of everyone else :) )

Oh what jolly fun :thumbsup:

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On this vexed matter ( did I just say matter !) of E and mc^2 just to illustrate the enormity of c^2 it is interesting to estimate how much mass LittleBoy ( the Hiroshima bomb) lost. I say 'estimate' cos no one actually measured the energy released.

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some authorities suggest only 0.6 of a gram of matter was consumed :(

 

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5 minutes ago, SilverAstro said:

:D  yes I knew well what you meant, massive in the English sense, you being, in a previous life, a being, a species even, that I used to hate ( an English teacher for the info of everyone else :) )

Oh what jolly fun :thumbsup:

How can you possibly hate English teachers? Let me tell you about J.... She was gorgeo- oh damn that C of C!!!

Olly

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8 minutes ago, SilverAstro said:

On this vexed matter ( did I just say matter !) of E and mc^2 just to illustrate the enormity of c^2 it is interesting to estimate how much mass LittleBoy ( the Hiroshima bomb) lost. I say 'estimate' cos no one actually measured the energy released.

,

,

,

,

some authorities suggest only 0.6 of a gram of matter was consumed :(

 

This puzzles me because even 0.6 grams at the speed of light the energy would have been infinite consuming the solar system but it didn't so the actual speed must have been a lot slower.

Alan

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29 minutes ago, ollypenrice said:

How can you possibly hate English teachers? Let me tell you about J.... She was gorgeo- oh damn that C of C!!!

Olly you are a genius, finally I now know why I never enjoyed Eng.lit and Eng.lang , , , wrong type of teacher !

 

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29 minutes ago, Alien 13 said:

This puzzles me because even 0.6 grams at the speed of light the energy would have been infinite consuming the solar system but it didn't so the actual speed must have been a lot slower.

Only the energy released was travelling at the speed of light.

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3 hours ago, ollypenrice said:

Yes, but since no massive body can get anywhere near 0.999C the question is rather academic!

Olly

Your forgetting this is all relative Olly. if say a cosmic ray is approaching you at 0.999c the from it's perspective you are approaching it (along with the earth and everything on it) at 0.999c.

Kinetic energy is not conserved when swapping views between inertial frames.

Regards Andrew

 

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10 hours ago, andrew s said:

Your forgetting this is all relative Olly. if say a cosmic ray is approaching you at 0.999c the from it's perspective you are approaching it (along with the earth and everything on it) at 0.999c.

Kinetic energy is not conserved when swapping views between inertial frames.

Regards Andrew

 

Yes, but in the OP's scenario a rock 'of a few kilograms' and a spacecraft are approaching each other. How could two such massive bodies find themselves with a relative velocity approaching C?

Olly

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2 hours ago, ollypenrice said:

 scenario  =

= a gedanken experiment in the style of the master himself ? And anyway "spaceship" "c" and "relativity" when appearing in the same post on a popular forum are, errrr, ummmm.

But it is a good vehicle device with which to pick up some hints about the workings of the great thinkers :) like what happens with kinetic energy :) Thank you Andrew I hadnt considered it that way round.

A gedanken, not an engineering blueprint.

Did you hear about the Bussard Ram thast scoops up interstellar hydrogen as fuel. Goes faster and faster and gets relativistically bigger and bigger and scoops more and more hydrogen till it starts scooping up whole stars and then star clusters - -  more and more hydrogen - - it goes so fast and grows so big that it starts gulping up intergalactic hydrogen - - and then whole galaxies - - and gets really really big and fast.

continued after the big crunch , , ,

 

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8 hours ago, ollypenrice said:

Yes, but in the OP's scenario a rock 'of a few kilograms' and a spacecraft are approaching each other. How could two such massive bodies find themselves with a relative velocity approaching C?

Olly

You can go as near to c as you want, but never c itself. Obviously, humans will never be able to do this, as due to mass increase, the ship would require a crazily humongous wacky vast amount of energy to move.

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10 minutes ago, Corkeyno2 said:

You can go as near to c as you want, but never c itself. Obviously, humans will never be able to do this, as due to mass increase, the ship would require a crazily humongous wacky vast amount of energy to move.

What your scenario needs, though, is a mechanism by which the craft would reach O.5C and the rock the same, minus the infinity-dodging digit. If we interpreted your initial description of the rock as 'stationary' as its having a history without acceleration then the acceleration history would need to belong to the craft and be almost C.

Olly

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