# Thread: looking back in time

1. ## looking back in time

im new to all this so please dont cut my down to fiercly in frenzy of intellectual mumbo.

if i was to place a mirror out in space 1 light year away. Would i then be able to sit on earth and 2 years after it appeared there be able to see the past occuring, in real time???
of course this relys on a few impossible aspects, like getting a big enough mirror 2 light years away, but if that is presumed would it be possible to do so??

2. ## Actually Yes

Patty Rick,

Actually you can do that now. Stand 4 feet 11 inches from a mirrow and you see yourself as you were 1/100,000,000 of a sec younger!

3. Why not use a video recorder instead, its cheaper than sending a rocket 1-light year away?

4. wow even better way of looking at it MacM hmmm also another question....

nothing can travel faster than the speed of light correct??? as that is asymtotic on a graph of energy to speed..
speed is all relative to a stationary point therefore

if you have 2 objects travelling towards each other at 0.6 C what is there relative velocity 1.2C i would imagine but how does that work?

5. ## Time

patty-rick,

Per Relativity (Velocity Addition Formula) the collective speed is only 0.88235 c.

Why not use a video recorder instead, its cheaper than sending a rocket 1-light year away?

Yea, you can wait 10 years, watch the video. Not bad ryans.

6. Per Relativity (Velocity Addition Formula) the collective speed is only 0.88235 c.
can u explain???

7. Resultant velocity of two bodies in special relativity is V=(u+v)/(1+u*v/c^2)

V=(.6c+.6c)/(1+.36c/1c)=.88235c

8. y is that so though, how is jsut a formula derived, surely to objects travelling past each other at speed 'x' have a relative velocity of '2x'

9. patty-rick:

The formula is derived from the Lorentz tranformations of special relativity.

10. patty-rick:

If you want more to read on the subject you may go here:
http://theory.uwinnipeg.ca/mod_tech/node137.html

11. i guess its one of those things that im going to have to accept , too fair ahead of me some of that stuff, just doesnt logically work in my mind

12. patty-rick: Could you explain to us why you think that two objects moving toward each other, each having speed x relative to something between them, would be moving toward each other a speed 2x?

In other words, WHY do you think that speeds add in that simple way?

13. Well HallsofIvy it's not a completely unreasonable assumption if you don't know anything about Special Relativity, it's how they add up in Newtonian physics and very good approximation for what happens at non-relativistic speeds.

14. Because that's the way it works if v is small. People just assume that it works at all velocities.

15. exactly , i have read through the time dilation and length contraction and i understand the effect of not reaching 1.2c, but my first observation was by no means unreasonable just a little un educated as you appear to be if you not familiar with those newtonian physics laws

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