Question for any Physicists or Astronomers.

[Beelzebud]

Ok, bear with me. I'm not college educated. I'm just a joe-six pack that should have went to college.

It is said that the light we see from stars and galaxies is light that can be millions of years old.

Is it possible to see our own galaxy, in the depths of space, as it was back in time? Or is it because the light emits from our galaxy that we never have a chance of seeing it?

[trotsky]

1. Straightforward answer: No.

Because you'd have to travel faster than light to get ahead of the light going out from our galaxy, and that's impossible.

Caveats: Wormholes, FTL travel, etc. All theoretical at this point, of course, but would make it possible.

[Beelzebud]

3. Ah ok, that makes sense.

Thanks for a non-condescending answer. :)

[htuttle]

2. Light from our own galaxy millions of years ago...

...already passed by us millions of years ago.

I think the Milky Way is about 100,000 light years across. Since we are fairly near the edge on one side, when we look across the center to the other side, we are seeing roughly 100,000 years into the past. But that's as far back as we're going to see as far as our own galaxy goes.

The Andromeda Galaxy, OTOH, is 2,000,000 light years away, so when we see it in the sky, we are seeing light that left Andromeda 2 million years ago.

[Beelzebud]

5. Thanks for the explaining. :)

[GodlessBiker]

4. The only reason they say that light is millions of years old...

is because the objects from which this light is shining are millions of light years away.

We are within our own galaxy, the Milky Way, so the stars we see in it are not nearly as far away as things outside of our galaxy. Therefore, the light from stars in the Milky Way is not as old as light from stars and other objects outside of the Milky Way.

Does that make sense?

[Beelzebud]

6. Makes perfect sense. I had never looked at it like that. Thanks! :)

[cosmik debris]

7. Imagine you are sitting in the front seat of a car

If you wish to see the grill you have to get out of the car and get in front of it. Now imagine that the car is moving at the speed of light. Getting in front of it is problematic. Einstein says you can't out-run the speed of light. So you will not be able to see the grill.

If you want to see the light from earth emitted millions of years ago, you have to out-run that light and get in front of it.

Does that help?

[Beelzebud]

9. Yes that helps. Thanks.

[Beelzebud]

8. mispost

[theoldman]

10. I was pleasantly surprised at the intelligent answers to the

question. Obviously none of you guys vote Republican.

[Beelzebud]

11. Same here. I appreciate it very much. :)

Welcome to DU, BTW. :)

[NNadir]

12. There is a very, very, very very^n slim chance.

Light bends in a gravitational field according to the general theory of relativity.

Theoretically, although probably not practically, light traveling close to a black hole could be bent around and reverse direction, especially after several such refractions. These types of events are known as gravitational lenses. I believe, but am not certain, that such lenses have been detected.

[Dead_Parrot]

16. Several have been found...

This is probably the best so far:



The white 'stars' around the edge are all images of the same quasar, which is actually hidden behind that big orange galaxy.

You'll find better images (ie, ones I haven't cropped!) here, and an annotated version (there's a lot going on in there) here

The chances of light ending up back at it's start-point from lensing are, err, astronomical. Still, it's a big universe... :)

[Nihil]

17. Strange ...

.. that image reminds me of simple "flare" on an imperfect lens
rather than anything particularly cosmic ...

As above, so below ...?

[Klimmer]

13. Thought experiment says - YES.

Those who have answered assumed you meant starting here on Earth first and then getting ahead of the light.

However, if you were say right now, at the focus of the Big Bang looking back to our galaxy the "Milky Way," then yes you would see light from our galaxy that was millions of years old as it once was.

Now, obviously we are not there but here, but theoretically it's true.
It's all about perspective.

This concludes this thought experiment.

[Sialia]

14. Not possible in our universe

The basic reason we can't look into space and see our Galaxy when it was younger is that the light emitted from that earlier time has passed us by. Light travels at the speed of light, which is much faster than any material motions can ever be. Hence light emitted from ourselves always outruns us.

The question is actually no different from "why can't we see the Earth as it was in the past". You don't find it weird that we can't see our own past on Earth, I presume.

The light really is old -- that is, the photons in the light we see from astronomical sources were emitted at some time in the past. Once created, photons exist forever if they do not collide with something. Most of the Universe is vacuum.

In certain types of universes (closed) it *would* be possible for us to eventually look back and see our Galaxy at an earlier time. This is because the light effectively travels all the way around the universe and returns to its starting point. However, our Universe isn't closed, it's open and accelerating.

(The diameter of the Galaxy is irrelevant, by the way.)

-A former astrophysicist

[Geoff R. Casavant]

15. Can I just say how amazing everyone who posted is?

First, person asks question. Not a stupid question by any means, and not one that's likely to be raised by the average American.

Then, all kinds of people post all kinds of answers. Everyone has a polite and informative explanation. Some even point out ambiguities or possible interpretations of the question, and answer based on their interpretations.

Finally, the OP thanks everyone for enlightenment.

This is why I love DU!

So in honor of the occasion, I post my response, tongue firmly in cheek, showing the standard FR response:

"If God wanted us to see it, he'd put up a mirror, moron."