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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."
So, when I look at the sun, I am actually looking back in time 8 minutes?
Yes, and apparently, 8 minutes ago hurts like a motherfucker.
The theory of relativity doesn't work right in Arkansas.
When you read Slashdot, you are looking back in time approx. 1.7e-9 seconds*, assuming you sit about 50cm from your screen.
* May be more if you're reading a dupe.
...following the principles of Heisenburger's Uncertain Cat...
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).
John Maynard Keynes: "When the facts change, I change my mind. What do you do?"
Yea the visible universe is some 46 billions light years. They are referring to detecting individual starts a billion light years away whereby normally you would only see a galaxy with non identifiable individuals stars at such a distance.
For a complete vacuum, it certainly has a lot of stuff in it to look at.
Someone forgot to clean out the filter? My vacuum filter always gets full of gunk after a while...
Seven puppies were harmed during the making of this post.
As an astronomy graduate student, I would like to offer a correction or an explanation of this statement:
From the article:
"That's because the older a star gets, the redder it gets, he says. Younger stars are bluer."
Kinda true, but the point is something else. A young *cluster* of stars will look blue because brightest stars in a young cluster are blue, massive stars. These blue bright stars burn their fuel (Hydrogen) very fast and have short lives (~100 Million years). When blue bright stars go away, more numerous, but much fainter, red stars start to dominate the color of the cluster. Therefore, as the *cluster* gets older, it gets redder.
For galaxies out to about 100 million light years, we can use a well-known relation between the pulsations of bright stars and their luminosities to get a pretty accurate distance. Beyond that, the simplest measure is the cosmological redshift of the light. If the redshift is, say, 10%, then we use the Hubble relation (speed / Hubble constant = distance), where (speed = redshift * speed of light) to get an estimate. We can then independently calibrate this with Type 1a supernovae, which all go off with roughly the same brightness. This is only really useful for smaller redshifts and distances, since asking for the distance of an object with a significant redshift is sort of ambiguous. Do you mean how far is it "now"? How far away was it when it emitted the radiation? But the above is the simplest answer to your question.
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. That includes all the pretty things out there to look at...
...in a vacuum. When not in a vacuum, light can travel at a fraction of the speed of light.
Well no, not exactly. When not in a vacuum it takes rest stops which reduce its average speed, but when not taking rest stops it travels at the designated finite speed; because that's the only speed at which light can travel. There was this Maxwell guy who 'splained it.
You know about the pony express? Well, they had posts along the way to change horses. Let's say, for the sake of simplicity, that these posts were 15 miles apart and that the horses traveled at a finite speed of 15 miles per hour. When the horse is moving it is always going 15 miles per hour, but the average speed of the horses over a full day is 13 miles per hour because of the time it takes for the rider to change them on an hourly basis.
Light is like the Pony Express, only without the horses, which wouldn't be like the Pony Express at all, would it? That would just be some guy taking a walk.
Nevermind.
KFG
From the article:
"Astronomers further said that they had decoded part of a computer signal from the star systems in question, possibly a signal 1,000,000,000 years old! It said, 'Please wait, Java loading.'"
And you know what's really weird? If the Sun just winked out of existence right this minute, the Earth would continue in it's orbit for 8 minutes before flying off into space. Why? Because gravity also propagates at the speed of light.
Anyone who has ever watched a Roadrunner vs. Wyle E. Coyote cartoon knows this.
I may twist orthodoxy to partly justify a tyrant. But I can easily make up a German philosophy to justify him entirely.
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
--
make install -not war
From the bottom of the linked page:
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.
SIGSEGV caught, terminating
wait... not that kind of sig.