Astronomer Discovers the Most Distant Stars Ever Observed From Earth

Cryolithic writes to tell us The Vancouver Sun is reporting that a University of B.C. astronomer recently used NASA's Hubble telescope to see a cluster of stars one billion light-years from Earth, the farthest stars ever observed from Earth. From the article: "That's interesting, he explains, because given that light travels at a finite speed -- 300,000 km a second -- the light emitted from the star cluster he and Kalirai saw was emitted one billion years ago. That means the cluster as it appeared to them two months ago was the way it looked one billion years ago. In other words, they were looking one billion years back in time."

paraphrasing Douglas Adams

[Ubergrendle]

Yet more evidenence that mankind cannot truly comprehend the vastness of space. Travelling 1 billion years at the fastest possible speed known to science doesn't even get us to the edge of the universe.

I remember a highschool experience. A teacher had a record, put it on the table. "Ok, see the hole in the middle? That's the sun. Track 1 is approximately where the earth is located. The outer edge might be pluto's orbit. Heliopause? That's probably in the teacher's parking lot. Ok, so the next closest galaxy is Alpha Centauri, so that is approximately...well, Hamilton." (We were in Toronto, Hamilton is 100km+ away).

Re:paraphrasing Douglas Adams

[Dunbal]

Travelling 1 billion years at the fastest possible speed known to science doesn't even get us to the edge of the universe.

      Ahh, but the beauty of it is that if you _DID_ travel at or near the speed of light, one billion years would not seem like such a long time at all - certainly doable within a lifetime! So if you asked those photons how old they thought they were, you'd be surprised at the answer... so the photons aren't really that old at all! Confused yet?

And conversely...

[singingjim]

...any alien civ that might be looking for us from that star cluster is looking at the earth 1 billion years ago. Guess they won't be finding us for a while. =\

Re:it travels as fast as it travels

[honkycat]

It's pretty darn close to a perfect vacuum... according to Wikipedia (and my recollection), the average density of the universe is less than 1 atom per cubic meter [wikipedia.org]. That includes all the pretty things out there to look at...

Assuming the Speed of Light is Constant

[Khomar]

This article has taken great and repetitive pains to explain something that may in fact not be true. A previous ./ story [slashdot.org] talked about indications that the speed of light may in fact be slowing down. Depending on the rate of change, they could be witnessing events significantly closer to the current time -- especially when we are talking billions of years.

speed of light in Pb

[cohomology]

The index of refraction of lead is 2.6, so the
speed of light in lead is c / 2.6 = 1.1E8 m/sec.
Of course, light is absorbed pretty strongly by lead.

The index of refraction is still an important
quantity - it determines how much light is reflected
from the surface, for example.

Re:Looking back in time.

[Doc Ruby]

I'm not sure that the "gravitons" postulated to execute that lightspeed limited coupling have been proven to exist. I know it was a subject of much speculation late at night while I was in college in the late 1980s.

If gravity also travels at lightspeed, I wonder whether space would "unwarp" around the Sun instantly. Or whether there's some "viscosity", with the Sun's gravity well taking some time to "snap" into an undeformed, thereby gravityless, shape in 3D (4D) around the Sun. Probably it's instantaneous, but we don't know that much about the "void medium" in which these fundamental forces act. At least I don't know that much :).

Re:Looking back in time.

[The_Wilschon]

Because gravity also propagates at the speed of light.

We don't know this. Sure, it is predicted to be the case by GR (I think. High energy physicists don't have to know much about GR, and I don't.), but we have not measured the speed of gravity in any sort of reasonable experiment. Clifford Will [wustl.edu], at Washington University in St. Louis, says [wustl.edu] that we need to detect gravity waves before we have any sort of reasonable measurement of gravity's propagation velocity.

From the bottom of the linked page:

The real way to measure the speed of gravity is to detect and study gravitational waves. By comparing the arrival of a gravitational-wave signal with that of an electromagnetic signal from an astrophysical source, one could compare the speed of gravity to that of light to parts in 10^(17).

Of course, I don't know Dr. Will personally. I merely turned up his page via Google, but WashU is certainly a respectable physics school, and I am inclined to trust what their faculty say about matters which are in their particular area of expertise and out of mine.