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Q & A: Moving around in outer space

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Most recent answer: 01/02/2015
Q:
If i were dropped in middle of space with no gravitational field near by then i wouldn't be able to move as internal energy of the system does not effect the state of the system.Then from where does light gain its speed from? That too the same speed every time? Because if it were pushed then it couldnt have had the same speed.
- Shanthika (age 17)
ankola,karnataka,india
A:

Hello Shanthika,

You have an interesting premise.  Not all is lost if you remembered to bring along a few batteries and your handy laser gun.   All you have to do is to fire off a couple of rounds.   The photons from the laser gun start off at the speed of light with respect to you.  They carry off bits of momentum and you will drift off in the opposite direction with equal and opposite momentum, in agreement with the conservation law.  By pointing the laser gun in a direction opposite to that of the earth you could make it back home.  The energy required would be that stored in the batteries.    Re-entry might be a bit of a problem.

 

LeeH

You may want to also look at some old answers on light acceleration: 
http://van.physics.illinois.edu/qa/listing.php?id=14639
http://van.physics.illinois.edu/qa/listing.php?id=2026


 


 


(published on 01/02/2015)

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