# Interesting thought...

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#1
After reading a post by somone in the Maths Further Maths topic, I wondered what would happen if two things were travelling in opposite directions, but both at a velocity of 2x10^8 m/s. The relative velocity of one of the objects to the other would be 4x10^8 m/s. Because this is faster than the speed of light, what would be visible from one of the objects? Sorry if this i a stupid idea and there is no way it is possible, but if you think about it, its quite an interesting little idea...... at least I think it is anyway. Discuss.
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16 years ago
#2
Originally posted by TS2Master
After reading a post by somone in the Maths Further Maths topic, I wondered what would happen if two things were travelling in opposite directions, but both at a velocity of 2x10^8 m/s. The relative velocity of one of the objects to the other would be 4x10^8 m/s. Because this is faster than the speed of light, what would be visible from one of the objects? Sorry if this i a stupid idea and there is no way it is possible, but if you think about it, its quite an interesting little idea...... at least I think it is anyway. Discuss.
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16 years ago
#3
i guess that as neither is moving faster than the speed of light its self, each would see a delayed version of the other- very interesting!
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16 years ago
#4
how do you do yhat line think?
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16 years ago
#5
what?
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16 years ago
#6
that ----------------------------

blablabla
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16 years ago
#7
the

--------------------------------------

.......dont mix drinks
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16 years ago
#8
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16 years ago
#9
I don't think you'd be able to see it. This is probably wrong, but....

Assume the other craft-thing is just visible. Surely by the time the light reaches you so that you can tell that it's just visible then it will have gone beyond the point at which it is just visible.

*after more thought*

Yes, you'd be travelling away from the craft at 4 x 10^8 ms-1 but the light from it can only travel at 3 x 10^8 ms-1, so it would never reach you.

However, in this unusual world, time dilation probably does something infinately weird to it.

So basically my reasoned answer is - I haven't got a clue.
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16 years ago
#10
Indeed, quite interesting.
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16 years ago
#11
Since the relative velocity is greater than the speed of light, the craft wouldn't see the other craft.

Phil
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#12
Thanks for the answers guys. Even though I posted this over 8 months ago. Time-dilation sounds interesting though.
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16 years ago
#13
(Original post by TS2Master)
After reading a post by somone in the Maths Further Maths topic, I wondered what would happen if two things were travelling in opposite directions, but both at a velocity of 2x10^8 m/s. The relative velocity of one of the objects to the other would be 4x10^8 m/s. Because this is faster than the speed of light, what would be visible from one of the objects? Sorry if this i a stupid idea and there is no way it is possible, but if you think about it, its quite an interesting little idea...... at least I think it is anyway. Discuss.
I read this once, I think the solution mentioned ir true: velocity is irrelevant because there is no point you coud refer to. The two travellers would never know about each other.
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16 years ago
#14
(Original post by TS2Master)
Thanks for the answers guys. Even though I posted this over 8 months ago. Time-dilation sounds interesting though.
Isn't that nice - an oldie returns. Welcome back, oldie.
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16 years ago
#15
hm okay so T = t(1 - v^2/c^2)^-1/2

so the time dilation factor is a complex number? interesting, I don't think it could happen?

*waits to be bashed by all those who actually do know how to apply relativity*
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16 years ago
#16
(Original post by ben2111)
I read this once, I think the solution mentioned ir true: velocity is irrelevant because there is no point you coud refer to. The two travellers would never know about each other.
There's still a displacement of one ship from the other though, surely?
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16 years ago
#17
(Original post by fishpaste)
hm okay so T = t(1 - v^2/c^2)^-1/2

so the time dilation factor is a complex number? interesting, I don't think it could happen?

*waits to be bashed by all those who actually do know how to apply relativity*
Time dilation won't be complex, cos you can't travel greater than the speed of light. As v -> c, v^2/c^2 -> 1, obviously.
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16 years ago
#18
Not possible, the only thing that can move at the speed of light is light itself. It has been suggested that anything moving close to that velocity, would change to pure energy itself.
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16 years ago
#19
(Original post by Nylex)
Time dilation won't be complex, cos you can't travel greater than the speed of light. As v -> c, v^2/c^2 -> 1, obviously.
Yeah I know, and time dilation -> infinity, but I don't quite understand the condition. So the relative velocity between them is v, then as I understand, the mass increases. But what mass increases, is there such thing as relative mass? Which mass increases? Because it's like:

Say you have a point O, and a mass A moving away from O at v ms^-1, and another mass B moving away from O at -v ms^-1. A is going to have one mass relative to O, and a different one relative to B?
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16 years ago
#20
(Original post by Woodsy)
Not possible, the only thing that can move at the speed of light is light itself. It has been suggested that anything moving close to that velocity, would change to pure energy itself.
See the example above though, it's moving less than the speed of light relative to one object but faster relative to an other. I'm guessing this is where the "the concept of a velocity between them is non existant" comes in. This seems very interesting.
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