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Questions tagged [speed-of-light]

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3
votes
3answers
258 views

Overcoming the speed of light thanks to ion thrusters

I am wondering if I could build an ion thruster, that is capable of exit velocity bigger that the speed of light. If I start with the equation for calculating exit velocity $v_e$ of a particle of ...
0
votes
1answer
74 views

Is the universe already colonized or are the Drake equation coefficients a much stronger filter: what are the cosmology issues with this paper?

http://www.fhi.ox.ac.uk/wp-content/uploads/intergalactic-spreading.pdf This paper posits a path to colonizing/probing the universe with lightweight (30g) or heavyweight (500t) probes based on 3 ...
7
votes
0answers
147 views

What percentage of the universe's galaxies are within our reply-lightcone before they're Hubble-flow expanded away too far to reply? [duplicate]

Because of the Hubble constant, how far can we now send a signal and still be in range to hear an immediately-issued (the moment they receive a signal) reply? And what percentage of today's visible ...
0
votes
2answers
85 views

Time when traveling around the speed of light [closed]

I heard that if you travel at the speed of light or faster (say, to the Kelper systems ) and come back, thousands of years may have passed but you haven't experienced more than a few. How is this ...
4
votes
1answer
660 views

Have we done any research trying to reach the speed of light? [closed]

Have we tried in the past to run tests or do research to reach the speed of light ?