It's a valid question. The answer is that at one point all the matter in the universe was in one location. The expansion of space pushes every object away from every other object at the same rate (this is called the Hubble flow), so all observers will measure the same proper time from the point in spacetime called the Big Bang. I can also say it another way. The cosmic microwave background radiation implies a rest frame with respect to the Hubble flow. We're moving approximately 300 km/sec with respect to the Hubble flow. The observations of the universe's age, however, is taken to be from the rest frame with respect to the Hubble flow. - Warren
ahh.... I connect the dots too often... Apparently, they determined a great deal about the mass and energy that composes our Universe. They quieted the vessel by using non-motorized cooling and heating systems to reduce the size of the error box. They used the five different bandwidths of frequencies to improve resolution and reduce the error box even further . It ran along an elliptical orbit around the Sun, and back out into our orbital path. They used the Moon to slingshot the scope to this velocity and distance. The Hubble telescope made many of the observations I mentioned. The reason I mentioned the distances and velocities that MUST have been observed by the Hubble to deterimine the Universe is expanding, is because it is relavent to zanket's question, against his postulation that our observations could be invalid due to the slingshot effect on observed light. Now, if I have erred in my layman's interpretation of what WMAP did, so be it. But, the fact that the <b>Hubble</b> observed the entire universe and plotted the changes in position of each body is plainly obvious. I only read one of the pdfs, and I probably confused some of the data from the Hubble with WMAP. The combination of the Hubble's data, noting the expansion of the Universe, further confirmed by WMAP's integration of the Universe as a 'flat' space-time, goes hand in hand with zanket's question. I may have been mistaken about the WMAP recording position and velocity. The Hubble did that. The WMAP used a baseline temperature(s) to determine many things about the energy and mass in our Universe. From the pdf I read, I gleaned they had a very precise map of the mass and energy in our universe, which is apparently against a backdrop of very consistent space composed predominantly of dark matter and energy. What I enjoyed reading most about, was the trajectory of the flight, and the technologies involved in the project. The results are not ambiquous to you, and to me they appear to agree completely with the data collected from the Hubble telescope, which did observe relative velocity and position of the vast majority of bodies in our Universe.
You’re not just toying with me are ya? We had this discussion before. Light falls in a gravitational field and accelerates as it falls. An observer at the top of a building measures light’s velocity along the ground at < c. Everybody measures light’s arrival or departure velocity at c. (I’m assuming a vacuum of course.) An illusion in the respect that we could observe a region of space that is expanding faster than predicted by Hubble’s law, but if we visited that region we’d find space expanding according to Hubble’s law. The cause of the difference would be indicated by the region’s clock, which relatively quickens the further away we observe it. Can you elaborate? It seems to me gravity can be arbitrarily strong. For example, if the light from a distant galaxy skirted a black hole, the light could be accelerated to an arbitrarily large velocity. Again, you would measure the light’s arrival velocity at c, but the acceleration of the light relatively quickened the light’s source clock to an arbitrarily fast rate.
Re: ahh.... Good for you for reading so much! I, for one, am proud of you. I hope you don't take that as condescension, because it's not. You came on here talking about how relativity was wrong, and now you seem to have a fairly good grasp of relativity, and are digesting technical papers on CMBR observatories. Reality really is zanier than anything you could make up, isn't it? If you're interested in reading alllll about the spacecraft and its operations, read the WMAP Explanatory Supplement at http://lambda.gsfc.nasa.gov/product/map/pub_papers/firstyear/supplement/WMAP_supplement.pdf A basic primer on what it's doing is available here: http://www.gsfc.nasa.gov/gsfc/spacesci/pictures/2003/0206mapresults/MAPprimer.pdf Yes, the Hubble key project was to measure Hubble's constant. Many many different people, with many, many different instruments, have helped in identify the distances and velocities to things though -- not just HST. (Of course, WMAP is not the only CMBR observatory -- COBE and other satellites came before.) I do need to correct this too, as you've said it several times. We are nowhere even remotely close to having a precise three-dimensional position for every body in the universe. - Warren
I'm not going to get into another horseshit discussion about whether or not relativity is valid. Remember, this thread is for real science. If you don't like it, get out. - Warren
I do need to correct this too, as you've said it several times. We are nowhere even remotely close to having a precise three-dimensional position for every body in the universe <HR> This makes perfect sense to me, I stand corrected. Thanks for the link, too. Isn't it true, though, that by having a very clear data set for a small subset of the large, we get a good idea about the nature of the whole, as long as there is a substantial cross section? Let me know if the above question needs rephrasing...
Absolutely! All of physics ultimately depends upon this idea -- that we can use our understanding of things in one place and time to describe things in another place and time. There's even a name attached to the concept, as applied to cosmology: it's called the cosmological principle. It is a postulate that space is basically the same everywhere -- the same mass and energy densities -- the same-sized lumps of matter -- the same physical laws, and so on. By understaning a [relatively] small part of the universe in depth, we should be able to extrapolate directly to all of the universe. "Viewed on sufficiently large distance scales, there are no preferred directions or preferred places in the Universe." - Warren
What part of the link I gave from the University of Virginia that says light accelerates, or Einstein’s comment that “A curvature of rays of light can only take place when the velocity of propagation of light varies with position” do you consider horseshit?
The velocity vector changes direction in a gravitational field. The magnitude does not change. Light appears to travel at the same speed, c, to all observers. If you do not agree, this thread is not for you. Find another one. Oh, and the horseshit is your 'arrival,' 'departure,' and 'travel' velocities. - Warren
I have mentioned this multiple times -- "velocity of propagation of light varies" has been misinterpreted (by you) to mean "speed changes". It actually means "the light bends". :bugeye:
GundamWing is quite correct: "Fire" a photon from point A to B and note that deflection between any two points causes light's average velocity to be less than it's absoute speed, as distance between points is greater around a curve.
When measured locally. I challenge you to resolve this paradox: Two observers A & B are one light-microsecond apart on the surface of a planet. Observer B is strapped into an electric chair, for which A holds the switch. Let’s assume an ideal wire between them, where the signal moves at exactly c as measured by A or B. So when A throws the switch, B’s watch stops exactly one microsecond later. You are at the top of a building overlooking A & B such that their clocks run 50% slower than your clock runs (this isn’t Earth). For every microsecond that elapses on your clock, half a microsecond elapses on B’s watch. Now, if you are correct (that light appears to travel at the same speed, c, to all observers), when you see A throw the switch, one microsecond will have elapsed on your clock when you see B’s watch stop. Yet B’s watch will show only half a microsecond elapsed, not one microsecond as B expects. Can you resolve the paradox? My prediction: chroot will evade my challenge or my rebuttals, likely with some abuse thrown in. I’d love to be proven wrong on this. GundamWing and island: I challenge you as well. Nah, I like this one. So everybody does not measure light’s arrival or departure velocity at c in a vacuum? Only you mentioned “travel.”
Resolved: You are at the top of a building overlooking A & B such that their clocks run 50% slower than your clock runs (this isn’t Earth). <HR> This is bull pucky, right here, because if you are not IN the reference frame of light being observed, then light could potentially appear to travel ANY velocity. Light appears to travel at the same velocity IN all reference frames, not oustide that refrence frame(s).
Re: Resolved: You do realize that you just agreed with zanket right? zank: I'm looking at your problem again... I need to organize it before i tryPlease Register or Log in to view the hidden image!
I showed in another thread to you how light’s speed may not be c when measured from afar. And in the challenge above. If you are correct then you should be able to resolve the paradox. The bending may be arbitrarily large. Light can orbit a black hole, for example. An observer hovering at a higher altitude would measure such light’s orbital velocity as < c, otherwise a paradox similar to that in the challenge arises. Nobody would measure slingshotted light’s speed as other than c locally; a blueshift would be observed instead. Thanks for the nice link.
Of course bending can be large near a black hole -- I was referring to planetary bodies and such. For larger objects (i.e., neutron stars, black holes, and so on) you get correspodingly greater bending / curvature -- relativity even tells you how much. My point was that it bends, but does not change speed. Please Register or Log in to view the hidden image!
I just have to say "shit" -- this is another "ge-dinken" experiment where we have to do all the work to prove the guy who is wrong, wrong. Please Register or Log in to view the hidden image! :bugeye: :m: :m: :m: :m:
Re: Resolved: Are you saying that an arbitrary time would elapse on your clock between you seeing A throw the switch and B’s watch stop? Please elaborate.
Your geydinkin experiment makes no sense I think the first (THE FIRST) thing you should understand boys and girls is that you don't need relativity to solve this problem -- you need to learn how to tell time. All your bloody characters in this dinken experiment are stationary with respect to each other -- you don't understand relativity at all do you? What the heck do you mean "top of a building overlooking A & B such that their clocks run 50% slower than your clock runs" -- you'd have to be on top of a 'growing/moving' building at relativistic speeds for that to be true. My advice to the bum on the rooftop of the building would be to get a new watch, possibly not one from KMART! :bugeye: Ge-dinken experiment indeed. Your time would not be 'different' than their time, and their times wouldn't be different either -- nobody is bloody moving anywhere. Time dilation only occurs when someone is moving somewhere. Please Register or Log in to view the hidden image! More irrefutable proof that no one who seems to challenge relativity on these boards, understands what "relativity" implies or requires. Please Register or Log in to view the hidden image! I do give you credit for making up a problem so complex I actually thought it HAD something to do with relativity. Please Register or Log in to view the hidden image! That said, I rest my case. Please Register or Log in to view the hidden image!
zanket: The problem in your thought experiment is simultaneity. Events which are simultaneous for the people on the planet's surface are not simultaneous for the guy on the building. The speed of light is the same, but the time interval between when the signal is sent and when the watch stops is different, because the signal is not sent simultaneously from both points of view.
