Question involving light speed & distance from non-physics person

[danieleWrites]

That planet flying out in the dark, the one that's been in the news these days, got me a bit curious. Well, the news articles mentioning ligh-years did.

 

So, question. If Guy 1 is standing 10 meters away from Guy 2, approximately how long does it take for the reflected light on Guy 2 to reach Guy 1? In human terms, it's pretty much instantaneous; however, it seems to me that in mathematical terms, that number is not 0. I don't have the first clue how to calculate that or even hazard a guess, other than something like a trillionth of a microsecond. Which seems wrong.

[GeoDUDE!]

The speed of light = 3 * 10^ 8 m/s.

 

Since Time = Distance/speed, we get on the order of 10^-7 seconds. which would make it on the order of a 10 millionth of a second. Though, the speed of light is different on earth than it is out in space; light moves faster or slower in different mediums. This really isn't a big deal though.

[danieleWrites]

That's actually longer than I thought it would be. Thanks for answering! There's this story called The Garden of Forking Paths by Jorge Luis Borges. It's very Many-Worlds Interpretation. It always got me to thinking about how we understand time and how people understand how we really see things. When someone sees something, they aren't seeing the thing as it is now; they're seeing the thing as it was in the past. No news to physicists, right?

[GeoDUDE!]

Absolutely, its often why many refer to telescopes as time machines. And by many, meaning only me.

[TakeruK]

I sometimes call them time machines too We actually have to account for this in some of the work I do! The light from the Sun takes about 8 minutes to reach the Earth. i.e. if the Sun were to just switch off, we would still see light for 8 more minutes. But, this means light coming from objects like Pluto can take hours before they actually arrive on Earth! So, if you need to measure positions accurately, astronomers have to take this time delay in account

[Guest |||]

Do not forget, even if light was instantanous, processing time is still required for the visual system to turn the "raw light" into a coherent meaningful representation which we call "Vision".  Each of us then is not only biased by the speed of light from an image, but also by our own personal machinary in processing this light.

[danieleWrites]

I am delighted by the telescope-time machine idea. I will be babbling no doubt flawed physics for the next month at this rate.

 

On a completely random note, someone put Nic's face on Miley's body for 8 seconds of Wrecking Ball. Nic rocks it better than she did.