Hey, I’m here to serve 
We can, almost. The problem in this instance is, the universe hasn’t always been transparent. Read this page for a good explanation as to why.
The 2d paragraph produced a paradox a few years ago when cosmologists found space bodies apparently older than the believed age of the Universe. IIRC, the Universe was believed to be about 15 billion years old, but the red shift indicated some objects were older. I am not clear as to how this dilemma was resolved. I read now that they think the Universe is only around 12 billion years old, making it even more of a paradox. Perhaps Chronos or someone else can answer that.
As to the 1st paragraph, I don’t believe there ever was a center to the Universe.
So at the present, we can only look back to when it was opaque; do you foresee being able to look through that opaqueness?
The age problem was with globular clusters, groups of stars which orbit our Galaxy (and other galaxies, as well). The cosmological theories were giving one value for the age of the Universe, and the completely independent stellar evolution theories were giving a larger number for the age of the globs. Since then, both cosmological and stellar theories have been revised, fixing the dilemma, but most of the modification has been with the Universe: This accelerating force, among other implications, means that the Universe is older than we thought. In fact, the age paradox was the first thing that led scientists to believe there might be an accelerating force, but when that was the only piece of evidence, most cosmologists didn’t consider it to be enough.
We can never have any hope of seeing anything earlier than about 300,000 years after t=0… with light. Neutrinoes can take us back a little earlier than that, but the real promise is with gravitational-wave observatories. Gravity waves are still reaching us from the first few seconds of the Universe, and we have the technology to detect them, if only we had the funding. Write to your local Congresspersons and tell them to increase funding to NASA to build the LISA observatory and its successors.
Just so there’s no confusion, I would like to say that MrDeath is talking about the same thing that I was about 13 posts up. The so-called last scattering surface for the light of the Universe is the same as the point where the Universe became transparent. I said that it was 300,000 years after the Big Bang, and MrDeath said 500,000. That’s just the kind of discrepancy you get in numbers when you do Cosmology.
“Do we need light in order for something to be observed?”
Unless I’m mistaken, the answer is a pretty firm yes. Remember that light (or photons) includes everything from visible light to microwaves to gamma rays to radio waves. Uh, I guess we could observe neutrinoes, but I’ve never heard of this being done in practice, or even proposed as a good idea. So, no, I don’t think anyone foresees being able to observe directly anything prior to the last scattering surface.
“So if the Universe is expanding at speed n, then an object fixed in space (having its own orbit) will recede from us at a speed 1/n?”
Eeeeyeah. I’m going to have to say I’m not totally sure about this. Cosmologists have managed to confuse me by saying that the Universe is expanding at the speed of light, and has been for a really long time, and also saying that the expansion rate of the Universe is changing. But I can say that that’s not quite what I meant. If the Universe is expanding at speed n, an object a distance d away from us will recede from us at a speed k×n×d, where k is just some constant. k×n is taken to be a value called H[sub]0[/sub], the Hubble Constant (or Hubble Parameter, since n actually is supposed to change).
Thanks a lot, Chronos! Make that 13 a 14 now…
As for gravity waves, yes! I forgot about those. That’s so crazy that it just might work. Write today!
If you want NASA to have some money, why don’t you just send them some? I bet you could talk people like Bill Gates into helping NASA easier than you could talk Jesse Helms or Strom Thurmond into it, especially now that DOJ has unhooked its jaws from his ankles. Don’t be lazy. Build a grass-roots voluntary funding campaign. Put your money where your mouth is today!
We talk about the age of the Universe, being x number of years old (15,000,000,000?), but how can we talk about years before there was anything upon which time could be measured? Before condensation of the plasma into particles, how could there be time? We may say that we’re not sure what time is, but we sure know how to measure it now: stellar time, etc. We can measure the events happening in the Universe, which is measuring time. One rotation of the Earth is one day, one revolution of the moon around Earth is ca 28 days, and one revolution of Earth around the Sun is one year. But before there were these “things” that could be measured, how can we talk about x years, etc?
Everything in the universe is moving away from everything else because space-time is expanding. Space-time expansion is accelerating and therefore the relative mass of the matter is increases owing to:
m = Mo / 1 - (v² / c²)
Therefore the gravitational force between the masses is increasing due to:
F = G.m1.m2 / d²
The distance is increasing due to Ho:
d = Ho.v.t
Time between them is changing due to:
t = to / 1 - (v² / c²)
Put 'em all together…
F = (G(Mo / 1 - (v² / c²)²) / Ho(v)(to / 1 - (v² / c²)
What does this all mean??
Umm… That’s right… Doesn’t this mean that the expansion of the universe will accelerate to a point where the gravity pulling it back together is equal to the expansion rate? Can someone better at math then I work out what that constant expansion is relative to (a. the mass of the universe, b. the speed of time/light).
Another Question to add:
Do gravity waves have a maximum velocity? They are the consistancy of space-time aren’t they? Is the expansion of the universe having any effect on the consistancy of the universe and therefore the speed of gravity waves and time?
PerfectDark
That’s not quite the way it works, PerfectDark. The problem isn’t that the mass increases due to moving at high speeds, since mass doesn’t increase at high speeds, and most things in the Universe aren’t moving much, anyway. The problem is similar to escape speed: If I had a universe with nothing in it but one planet, myself, and a baseball, and I throw the ball up off the planet, then it will always be pulled towards the planet, by gravity, and so as it’s going up, its speed will be decreasing relative to the planet’s surface. However, if I throw it fast enough, then the speed will asymptotically approach zero, or if I throw it faster yet, it’ll approach some value greater than zero, so it’ll never fall back.
Similarly, even if gravity were the dominant or only force in the Universe, then it’d still be possible for it to expand forever, but at an ever-decreasing rate, depending on the rate of expansion and density at some time. It seems, though, that the dominant force in the Universe is not gravity, but lambda (or whatever you want to call it), and unlike gravity, lambda seems to have a stronger effect the farther apart two objects are, so barring any changes in the field’s strength, it’ll continue to get even more dominant.
To answer your other question, gravitational waves travel at exactly c, just like light. The benefit to using them isn’t that they’re faster, it’s just that they’ll pass through almost anything, including the plasma that filled the early Universe.
Finally, while I think that private support for NASA is a great idea, I don’t think it would work. There’s all sorts of bureaucrats involved in the process, who seem determined to keep money away from anything remotely useful. We could learn a lot about capitalism from the Russians, who recently accepted a contract from Pizza Hut to deliver a salami-and-cheese to the Space Station (really!).
I couldn’t even get them to save the Pluto mission! (something more “concrete” in the eyes of a politician than detecting faint gravity waves) 
By the expansion of space. Roll it back until it’s all crunched into a point. Measure time from that. Also, (maybe Chronos can help us out again here) physics has some understanding of that period and can make predictions about the expansion/temperature of the universe (i.e., how long it would take for the Big Bang energy to cool into “normal” matter).
Err, i had just read that gravity waves travel at the speed of light in a Roger Penrose book. Has something changed here? If they do travel at the speed of light then how could they just be reaching us?
Because the speed of light is finite. If something is x light years away, then it takes x years for newly generated photons or gravity waves to reach us.
So, depending on the distance from us and the time when the event happened, the information may not have reached us yet (this is along the same lines as the realization that some of the stars you are seeing in the sky may no longer be there*).
- self nit-pick…the stars visible to the naked eye are all nearby & probably are as they seem to be.
Just to unpick your nit, Phobos: Betelgeuse (which is certainly one of the stars folks see in the sky) has probably already died. As we see it now, it appears to be rather less than a millenium short of supernova, and it’s 800 lightyears away. In formal logic, “one” qualifies as “some”, and your “might” accounts for any error in the measurements, so your statement was exactly correct as written.
Gravity waves are still reaching us, and light’s still reaching us. The only difference is that the light kept getting distracted up until a certain point, so we can’t get any information from it before that time.
But I liked that nit!
Anyway Betelgeuse may only be 400 or so light years away so the odds may be a little better that it has yet to go supernova. But I agree that it’s within a millennium (or a few millenniums) away from that event. Maybe it’s already gone and done it…I’ll be watching for sure (not that it will be hard to miss!)
That’s for sure. By my back-of-the-envelope calculations, it’ll be brighter than the full moon, which is especially noticeable for a point source. My figure of 800 Ly was just from memory, so your cite is probably more accurate: I can’t imagine that there’s any significant error in ol’ Armpit’s measured distance.
They do go together. More mass, stronger gravity. umm assuming same distance.
Although thinking about my earlier post I think I could now pick it apart. sigh.
While originally our idea of time was relted to these things, that is no longer the case. Time is … blast can’t find the post … defined as the exact number of rotations or a particular atom that is nicely regular.
[Mary Poppins]aH ha HA HA ha[/Mary Poppins]
got it. 1 second is exactly 9,192,631,770 vibrations of the radiation for a specific wavelength of a cecium atom.
That was posted before, and as I said before there was transparency there were no atoms with nuclei. As Chronos pointed out, there were hydrogen atoms (protons) even from the beginning, in the ionic plasma. He said there were also helium and lithium atoms, so I’ll take his word for it.
This stuff is WAY out of my league but it’s fasinating.
Here’s a link to the BBC Horizon programme about how a group of supernova hunters stumbled onto the idea that the universe was expanding at a increasing rate.
If you can observe, you can measure time. You might not be able to do it with caesium atoms if you’re in the primordial plasma, but there are surely ways to do it (help me here, Chronos). We can talk about years before the Earth even existed, because a year is just a certain number of seconds, which was picked because it does coincide with the amount of time it takes our fair planet to swing around our fair sun, right now. It’s a convenient handle for us, nothing more or less. But numbers have always existed, and so have seconds; ipsos factos so have years, even before we defined what a year was, even before there was an Earth to define them. I could define a ‘Sun-life’ as the number of seconds from the first sustained nuclear reaction in the core of our Sun until the moment said reaction ceases. I have no method of measuring a ‘Sun-life’ at the moment, but it’s just a certain number of seconds, once I know what the number is.