Speed of light and small distances

[masteri]

Hi,
i have tought of a something that i don't know if is it true. As far as i know speed of ligh is 300,000 km/s and it is about 8 minutes to reach the earth. Now when we look ate the other planets we are looking at sort of a delayed picture because of the time light needes to travel from that planet to earth. Am i right about this? If i am does this also means that we on Earth alos have a dlayed picture becouse of time light needs to travel from object that we are looking at(on earth) to us. So for example, let's say that i am in a hugh room and it is total dark. 100 metes from me is another man that i can't see. So someone comses along and turns on a light. Light travels form source of light to that men, bounces back to me and i can see the guy. Am i right about this too? Does this mean that there is also a small delay of picture because of the distance? So when ever a guy moves i see it delayed becaous of a distance?

Thank you

 

[Drakkith]

You are 100% correct. For distances on Earth the delay is so small that isn't even close to noticeable for people.

 

[Bloodthunder]

If you want to look at yourself in the past, look in a mirror. =)

 

[Jack_O]

Human perception is too slow to notice the effect but it is in total agreement with the best measurements so far. GPS for instance relies on it.

If you want to bring the huge number (3x10⁸ms^-1) down to human scales then think of a modern cpu, operating at 3GHz light travels only 10cm in the time it takes for said cpu to complete one cycle.

 

[Ryan_m_b]

If you want to look at yourself in the past, look in a mirror. =)

Indeed, about two nanoseconds in the past!

 

[pallidin]

Indeed, about two nanoseconds in the past!

Wow that's kind of neat. Never thought about it that way but your right.

 

[robinson]

Curses! This thread has caused my mind to ponder the speed of light and time and everything! I realized that to exceed the speed of light actually would be time travel!

"What?" you might say? Well, if you can travel faster than light you can see go someplace where what has happened in the past hasn't "happened" yet, because the information usually is limited by the speed of light, but if you can travel faster than light (which is illegal of course) you could know about something before it happened. You would actually be able to see yourself doing something that happened in the past, but as it happens, because you are now in the future.

OH sure you probably think that is crazy talk, and it is, because you can't travel faster than light. But the analogy of the speed of sound will serve. And since a bullet can travel faster than sound, the bullet does indeed outrun the event of it's source.

You can shout, then race faster than your own voice, so that the event hasn't happened yet, meaning you went backwards in time. Now you are someplace waiting for an event that already happened to happen. If you could do the same thing with the speed of light, you could outrace the light of an event, and be back in time before it actually "happened" yet.

You see why I started with "Curses!". Faster than light travel would be time travel. Not very practical, you might think. But in our fantasy world of of faster than light travel you could outrace light and "go back" in time and watch the creation of the Universe, because somewhere far far away it hasn't happened yet.

OK that is stretching things a lot. Especially since the topic is about "small distances", not really big ones. But it's the same principle.

I think. OK ignore all that. I just had to get it out of my head. And it really was all this thread's fault.