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Boxes
2009-Jan-20, 10:21 PM
This is just a crazy thought that popped into my head. I apologize if this has been asked before, I am tired and my search-foo is weak.:(

If you could accelerate say a Hubble type telescope to near light speed, could you see farther in the direction of its travel due to relativistic effects?

grant hutchison
2009-Jan-20, 11:58 PM
If you could accelerate say a Hubble type telescope to near light speed, could you see farther in the direction of its travel due to relativistic effects?Stuff in the direction of travel would appear brighter, but also smaller.
So I guess it would depend on what you wanted to see.

Grant Hutchison

antoniseb
2009-Jan-21, 12:09 AM
Stuff in the direction of travel would appear brighter, but also smaller. So I guess it would depend on what you wanted to see.

It would also be highly blue-shifted, so what was microwave or deep infrared might be what you'd see as visible, and what was visible would zip through the mirror as xrays.

Boxes
2009-Jan-21, 01:34 AM
I'm pretty sure I understand the blue shifting. I'm guessing the objects in the direction of travel being brighter is caused by the telescope intercepting more photons due to length contraction(please correct me if I'm wrong).

Could you explain why the objects would appear smaller. Please imagine you are talking to someone who knows little about astronomy(because it would be true).

Perhaps I have been reading too much ATM, but I feel I must state that I am not promoting any theory, and I have great faith in mainstream science to explain these strange things to me.

grant hutchison
2009-Jan-21, 09:06 AM
Could you explain why the objects would appear smaller. Please imagine you are talking to someone who knows little about astronomy(because it would be true).It's called stellar aberration: incoming light is displaced a little towards the direction you're travelling in. You can see the same effect classically by running through vertically falling raindrops (your front gets wet, your back stays dry), or by driving through falling snow (when the snow always seems to come from ahead, no matter which way you drive). An analogous (but not identical) effect happens with light.
We can observe this effect from Earth: Earth's velocity around the Sun is enough to produce a measurable displacement in the apparent position of the stars, so that each star describes a tiny ellipse in the sky during the course of a year.

Anyway. If an object is directly ahead of you, all its edges are displaced inwards towards your direction of travel, so it appears smaller. It turns out that objects off to one side are similarly reduced in apparent size, while being displaced towards your direction of travel. Objects behind are enlarged (but grow dim and redshifted). At the extreme, objects that are physically behind you can be displaced so strongly that they appear ahead.

Grant Hutchison

Boxes
2009-Jan-21, 05:30 PM
Thanks Grant and Antoniseb for the illuminating replies. I'm going to look into this more on my own.

grant hutchison
2009-Jan-21, 05:36 PM
I'm pretty sure I understand the blue shifting. I'm guessing the objects in the direction of travel being brighter is caused by the telescope intercepting more photons due to length contraction(please correct me if I'm wrong).Sorry, I meant to address this.
For the travelling telescope, the clocks of the stationary stars run slow under relativity: so that induces a red-shift in the emitted light, which is detectable for stars at right angles to the line of flight. For objects dead ahead, however, the telescope runs into the light and offsets this red-shift so much that a blue-shift is observed. There are lots of ways to imagine how the blue-shift occurs: you can imagine the telescope running into oncoming waves, or waves bunching up ahead of the emitter, for instance.

Grant Hutchison

speedfreek
2009-Jan-21, 06:30 PM
Thanks Grant and Antoniseb for the illuminating replies. I'm going to look into this more on my own.

Have a look at this link (http://www.fourmilab.ch/cship/aberration.html), it is a good illustration of the abberation of light (with pictures!)

Boxes
2009-Jan-21, 08:49 PM
Thanks speedfreek, nice link. And thanks for all the answers guys. I had never heard anything about this before. Very cool!