Since we are looking back in time when looking at distant stars.....?

Question

is it possible there are no galaxies in our line of sight, anymore? That the accelerating expansion of the universe puts us in an empty space, with just our galaxy at "reach"...
better still, that we're on the verge of the "great rip"?......

yes, but when we say nearby, I say line of sight. Cause thats all that matters AND the rest of the universe is not visible to us cause its light has not reached us yet. If the expansion out runs the speed of light in the long term, we'll just have the milky way to gaze at....

thanks eric. And space's expansion is ACCELERATING...ain't it?

orichalc, its the space-time continuum itself that's expanding....the speed of light is getting greater. Not so much anymore, but still. The constant c remains but space itself is getting more "elastic".....

Michael, didn't know that....wanted to know what the speed was like......
one of my many irrationnal wonderings......;-)

Answer 1

Astronomers are proposing a large telescope to be installed on the far side of the Moon the mirror consisting of a pool of liquid metal. It is thought that this will be that ultimate telescope that will finally allow us to be able to see just what you are talking about. The "edge" of space.

Answer 2

It is not correct to say that we "look back in time" when we look into deep space. We are looking at the images of stars in the present moment.

We may be looking at the (August 6, 2007) image of a star that is now much older than it was when the light by which we see it started its journey toward us; the point is that we still don't see the star in the past.

Consider this image. I am standing on the observation deck at JFK airport in New York City and see an Airbus arriving from Los Angeles. Can I say I am looking into the past because the airliner left LA seven hours ago?

No. I am seeing the airplane as it is. If I see the light from Betelgeuse tonight through my telescope, I am similarly not seeing into the past. I am seeing an old family portrait of Betelgeuse, but I am in the present, Betelgeuse is in the present, and the light from Betelgeuse is in the present.

And the main way we observe the positions and effects of other galaxies is by their gravitational effects on other galaxies, which give us a wide spread of time over which to observe their histories.

You can be sure we are nearer the beginning than the end of this whole drama. There are plenty of galaxies, and more to come.

Answer 3

We are still very far from the time when there will be no receding galaxies to see (tens of billions of years). When that happens, then any astronomers left in our neck of the woods will only see the local Group which will have changed quite a bit by then -- for example, the Milky Way and the Andromeda galaxy will have collided (6 billion years from now) and will have formed a giant elliptical galaxy.

The Local Group members are bound to each other by gravity; therefore, they are not pulled apart by the expansion.

That will still leave "us" a dozen galaxies to look at.

As for the galaxies that we "now" see (as they were when the light we see left them), there are many of them that are now the age of our own galaxy. They may be a lot further from us in reality, compared to what we see, but still they would be in our line of sight -- if we could see their light instantaneously.

Galaxies that are presently at less than 4 billion light years from us (then), are now no more than 12 billion light years so that they are not receding at speeds above c.

Answer 4

Your idea is basically correct - there is a point where galaxies cannot be seen because their speed of recession (due to the expansion of the universe) is greater than the speed of light - so the light from them can never reach us.
WIth expansion, over time we will be able to see fewer and fewer galaxies as more of them reach that critical "speed of light" recession speed.

Answer 5

I think what you are asking is it possible that there are no galaxies nearby us anymore? Probably not - the rate f expansion is not that fast. The light travel time, as long as it is from our galaxy to the nearest neighbor would sort of rule out anything cataclysmic being imminent.

Answer 6

i think the rate of expansion in the universe is accelerating and i believe that eventually, if the Earth existed long enough, which it won't because of the Sun burning out [with an expansion phase that will fry the Earth], but if it did last long enough, we would eventually not see anything in the sky.
i think most theoretical physicists think that the universe will continue to expand.
entropy will continue to increase until the universe is homogeneous. right now, there are extreme fluctuations in matter and energy densities.

Answer 7

No, remember that nothing with mass can travel faster than light no matter how much energy you gave to it, but it is true that we will not be able to see some galaxy anymore, their light will be so red-shifted that we will need a very long time to get one complete phase of its wave.
Just imagine if a galaxy move from us very fast, the light wave will be greatly red-shifted that one wave is millions light years long. This means that we will need one million years to get a period of that light wave.

Answer 8

The galaxies are NOT moving at the speed of light. If they were, we would NEVER be able to see them.

The other thing to consider is that new stars, and new galaxies continue to be formed, and some of them are bound to be in our line of sight, now, and in the future.

Answer 9

This is possible but unlikely. Some galaxies are moving toward us so it's even less likely that those have suddenly receded from us.

Answer 10

It is possible if the galxys move very fast but at the current rate of expansion it is impossible