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Light

Posted: Wed Apr 18, 2007 1:06 pm
by John Russell
When someone turns off a flashlight, does the light that has been sent continue to go out into space? E.G. When a star no longer exist, do we continue to see the star millions of years later, assuming it was millions of light years away?
Thank you for the consideration.

John

Posted: Wed Apr 18, 2007 3:22 pm
by makc
why not? is a flashlight supposed to suck its light back into itself once it's switched off?

light

Posted: Wed Apr 18, 2007 3:41 pm
by John Russell
When I use a hose for water, when the source is cut off, so is the stream of water. What does light use as an energy source once it is cut off?

Re: light

Posted: Wed Apr 18, 2007 6:53 pm
by NoelC
John Russell wrote:When I use a hose for water, when the source is cut off, so is the stream of water. What does light use as an energy source once it is cut off?
Actually, the stream that has already left the nozzle continues after you cut it off. It is traveling under its own kinetic energy, which was imparted at the nozzle when it left the hose.

-Noel

Posted: Wed Apr 18, 2007 9:10 pm
by BMAONE23
Super Nova 1987A or SN1987A became visible to us in 1987 (20 years ago) but the event happened 168,000 years ago. In 1986, the star still looked like a star to us even though its's death had already occured appx. 167,979 years earlier. http://heritage.stsci.edu/1999/04/sn1987anino.html
So even if a star had "winked out", we would continue to see it as is was until the event light reached us.
You're flash light analogy is a good one though. If it were the only light source, it would remain visible until the "turning off" light curtailment event passed by the alternate observation point.

Realistically though, it would be overpowered by other, brighter sources and be lost to their light, like that of the sun or another star.