New Study Shows Universe Still Expanding On Schedule 173
The Bad Astronomer writes "A century ago, astronomers (including Edwin Hubble) discovered the Universe was expanding. Using the same methods — but this time with observations from an orbiting infrared space telescope — a new study confirms this expansion, and nails the rate with higher precision than done before. If you're curious, the expansion rate found was 74.3 +/- 2.1 kilometers per second per megaparsec — almost precisely in line with previous measurements."
Obligatory Spelling Comment (Score:5, Funny)
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Not to be pedantic, but that is an impressive way to misspell 'messureents'.
The part of the universe covering that word hasn't fully expanded yet..
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that is an impressive way to misspell 'messureents'
Wrong. 'messureents' is how you spell 'messureents'.
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that is an impressive way to misspell 'messureents'
Wrong. 'messureents' is how you spell 'messureents'.
The summary now says "measurements", so I guess the above is correct now?
Re:Obligatory Spelling Comment (Score:4, Insightful)
Not to be pedantic
Sorry to be pedantic, but you are being pedantic.
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sory to be pedantic but it's "ditto".
It's... (Score:3)
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Not to be pedantic, but that is an impressive way to misspell 'messureents'.
And yet they calculated the speed of light modified by the expansion of available space to travel through at a potentially non-static rate. I'm sure they didn't make a mistake there either, lol. Okay, here's my amateur astronomer opposition theory: the rest of the universe is gone! IT'S JUST GONE! But we're still receiving light from when it was there. Prove me wrong, lol. See, anyone can make anything up that's unprovable with modern technology.
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8 year old's question (Score:5, Insightful)
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Re:8 year old's question (Score:5, Funny)
Re:8 year old's question (Score:5, Informative)
Unless you have a generic curiosity, don't try to hard to read that, as it is not related to the universe's expansion. The grandparent was just being random or joking. A Hilbert space is just what you get when you treat the set of all continuous functions as a vector space. It has several different possible basis sets of functions you can add up to make any other function, e.g. sine waves via Fourier analysis. Instead of having unit vectors like x, y, and z, you would have unit vectors like sin(x), sin(2x), sin(3x), etc. (which makes it infinite dimensional). The concept is really important to physics, especially quantum mechanics and any where else things like Fourier analysis would be done with some mathematical rigor. But it is not what the universe is expanding into.
The typical analogy used for what the universe is expanding into is like a balloon being inflated, with that being a 2D universe on the surface of the balloon. You could ask about the third dimension it is expanding into, but that is not really relevant (at the moment at least). The only thing that really matters is the curvature of local space (how non-flat any given spot on the balloon is). Short of discovering some new theories unlike what we've seen before or something like brane theory, the equivalent of the 3D dimension in the balloon analogy would be unreachable and meaningless, as it would not be able to affect things in anyway beyond the curvature of the surface.
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I like the loaf of raisin bread [wikipedia.org] analogy better.
The rest of the this [wikipedia.org] wikipedia article explains things in more understandable terms.
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Re:8 year old's question (Score:4, Informative)
Nothingness. There is no space & time outside the physical universe. If that doesn't bake your noodle, I don't know what will.
The nice thing about Religion^H^H^^H^H^ science is that it advances one funeral at a time. (With apologies to Max Planck :)
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Question 2
There is no space & time outside the physical universe.
Are you sure? How do you know?
Etc. etc. ad infinitum. It's a good answer though, even I can understand it and it's helpful. Thanks!
Re:8 year old's question (Score:5, Informative)
"There is no space & time outside the physical universe.
Are you sure? How do you know?"
He doesn't need to know: that's a per-definition fact.
A different question would be if the physical universe is composed of four dimensions or there are more.
Re:8 year old's question (Score:5, Insightful)
Re:8 year old's question (Score:4, Insightful)
Correction: There is no space and time that we can determine with any certainty outside our physical universe.
This is imprecise at best. There is no "outside our physical universe", because dimensions becomes meaningless at the border of the universe, so there is nowhere "outside" for other universes to be. If they exist, they don't exist "outside" our universe, at least not in a dimensional sense.
As for time, that is a purely local phenomenon, and we can not determine it even inside our universe, except right here. Every "here" will have its own rate of time.
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"In the beginning, God created the heavens and the earth. The earth was without form and void, and darkness was over the face of the deep. And the Spirit of God was hovering over the face of the waters."
Flame away. <BFG>
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This is imprecise at best.
Really, you have to admit that for something purely theoretical with a high likelyhood of never being proven at all, "imprecise at best" is a moot statement -- at best. :-)
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I'm also disturbed by your use of the phrase "rate of time." What does that mean, if anything?
For a local observer observing itself, nothing.
Time itself bends in the presence of gravity or velocity.
If you sit at A, which is equidistant from B and C, and observe a spaceship close to the speed of light going from B to C, you may observe that the trip took five years. However, the spacefarers aboard the vessel will swear up and down that it only took two years. And you're both right.
The travelers who are in a different time frame has a different "rate of time" -- by your clock. Just like you have by
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Limits of the human mind (Score:2)
I think it just means our concept of time is wrong.
Black and white thinking meets the limits of conception. *every* concept is wrong. It is a trivial statement. Both the concept, and its black & white categorization as right/wrong, are artefacts of the human brain. And the GP is wrong. From a photons point of view, it has zero lifetime only if it travels through a perfect vacuum. Light travels more slowly otherwise, and then observes "time" and "distance".
Another way of saying is, if a photon was generated in a distance star, and it intersected with
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Until we can test our models experimentally (highly unlikely for this particular case), I'd say that "uncertain" is a very precise way to describe it.
being an outside to be uncertain about.
You can't go five feet past the edge of the universe, because there is no space to measure five feet in. There isn't a void outside the universe where other universes can be, because that presupposes that there is a void with spatial coordinates, while those are attributes that belong to our universe.
Yes, we want to think of what's beyond, and our intuitive thinking doesn't deal well with models that doesn't represent space as we think of it.
The background radiation o
Re:8 year old's question (Score:4, Interesting)
The universe could be a compact manifold, in which case it isn't expanding into anything. That would fit with the essential notion that it is space itself that is expanding.
Re:8 year old's question (Score:4, Insightful)
The problem with what you're saying is the word "into". It still suggests that there is some medium into which the universe expands. It's another form of the famous Hawking problem "What's north of the north pole?" If there is nothing, then the universe is not expanding into it. It is simply expanding.
As much as anything, it is a problem that while expressable mathematically, is, at least to most peoples' brains (mine included) something impossible to imagine. It is just another way in which our common every day perceptions of the world around us don't model every aspect of reality well.
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There is a large amount of neurological heavy lifting that goes into interpreting sensory input.
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is thinking that "our common every day perceptions of the world" are somehow not reality. Model, indeed.
--
That really depends on how you define reality.
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"The universe could be a compact manifold, in which case it isn't expanding into anything. That would fit with the essential notion that it is space itself that is expanding."
Just as easy to say that it is expanding into nothing.
It's even easier to say the universe is self-contained, which bypasses the need to explain that the "nothing" you're using in your expression is not the same thing as empty space.
Re:8 year old's question (Score:5, Funny)
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Hera (Score:2)
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Milk. The universe is surrounded by milk.
Unlikely. Turtles don't have milk.
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Other universes. It's that whole 'obesity' thing, which is why the kid should be outside running around and getting exercise rather than sitting inside and asking questions.
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Hey man, I just work here, OK?
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Good point, are we measuring distance, or the speed of light?
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Units (Score:1)
So, I'm probably laying out my lack of knowledge on this one, but can someone who knows about that which they speak explain kilometres per second per megaparsec?
Re:Units (Score:5, Informative)
Due to expansion, the speed of objects accelerating away from us is proportional to the distance from us. So according to this, an object at 1 megaparsec from us will be receding at 74.3 km/s, while an object at twice the distance will be moving twice as fast.
Re:Units (Score:5, Interesting)
Re:Units (Score:5, Informative)
Re:Units Space FTL, but information thru space? (Score:4, Interesting)
Something I've been wondering about, but never knew quite where to ask. (Maybe this isn't the place either, but I'll give it a shot.)
i understand (or at least parse the semantic meaning) that the speed of light through space is fixed, and space can expand fasterthan that. Normally, it seems that the speed of information transmission is also tied to the speed of light, mainly I presume, because paradoxes would arise if it weren't. But can information travel across space at an effective speed uninfluenced by the expansion of space without causing paradoxes? Is it possible that information could still reach us even if light could not?
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i understand (or at least parse the semantic meaning) that the speed of light through space is fixed, and space can expand fasterthan that. Normally, it seems that the speed of information transmission is also tied to the speed of light, mainly I presume, because paradoxes would arise if it weren't. But can information travel across space at an effective speed uninfluenced by the expansion of space without causing paradoxes? Is it possible that information could still reach us even if light could not?
FIrst off, don't worry about paradoxes, because physics doesn't. As much as it may hurt our brains, according to Tippler's solution for an infinitely long cylinder, Feynman diagrams and other solutions for Einstein's equations for general relativity, it seems that the physics doesn't bear out paradoxes. However, many of these cases are so extreme that we doubt we'll ever see them and its a safe bet to even say they are not actually possible (although nothing prohibits them according to the physics I have se
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Hold on there.
If I recall, one of the principles around c is that two things may not move apart faster than c, either. So if you have an observer with a lantern on a train moving 60mph, the light moves away from the observer at c. But! It also moves away from the train platform at c, not c + 60mph
Now as I see it, what is being described is that the universe (spacetime) is the train in my scenario. How could you then account for the rate of expansion from the perspective of two individuals, one at each "e
Re:Units (Score:5, Informative)
Space itself can expand such that the objects (events?) within it are moving apart at faster than c. Any two objects separating faster than c can't measure that -- they cannot pass any signal between them. Any light (or other signal) which leaves one will be redshifted away to nothing before it gets to the other. They are outside each other's observable universe. I'm pretty sure this has to handled using General Relativity, I don't think Special Relativity has any concept of expanding or contracting space-time. Space-time described by Special Relativity is flat and static.
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I'm open to discussion, but I'd say there is a flaw in your example -- if points A and B are truly 'at rest' relative to each other then by definition the distance between them is not growing (no velocity induced redshift). I think you are trying to use the definition of 'rest' as meaning no "peculiar motion" (astronomical term) on top of the motion imparted up on them by the expansion of space between them. A concrete example would be galaxies observed at a large distance -- they all have a redshift due t
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Dang, now I have to go review some GR stuff to go any further. When you get deep into GR, either on cosmological distances or strong gravity fields things get badly non-intuitive. In this particular case I think we will run into the problem of what exactly is meant by "areas of space receding from each other at faster than c". I'll leave with this one question -- if you postulate two objects separating from each other at faster than c due to the cosmological distance between them, and further assert tha
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Yes, the paradox more commonly known as:
http://en.wikipedia.org/wiki/Ant_on_a_rubber_rope [wikipedia.org] (the expansion of space is explicitly referenced at the end of the article).
It has to be said however, that the 'finite amount of time' can easily be ridiculously large.
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The Universe has no center (Score:2)
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The center of the observable universe is exactly where I am at this moment. Beyond the observable universe, we have no idea, so we might as well assume that the center of the universe is the same as the observable universe. Me.
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You're the center of the universe? And people say that I have a big head...
Light years please (Score:2)
"The universe is about 14,000 megaparsecs in radius"
A parsec is about 3.26 light years therefore a MegaParsec is 3.26 million light years
Say if you have velocity per distance thats distance per distance per time, the distances cancel out so the value would be a per time in other words a frequency
a very small frequency of course, but still could be expressed in hertz
Re:Units (Score:4, Interesting)
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I think you got your final result messed up:
(74.3 km / s / mparsec) * (1 / 3x10^19 mparsec / km) = 74.3 ? / s * 3.3x10^-20 ~ 2.4 x 10^-18 cycles per second ~ 403768506056527590 seconds per cycle ~ 12.7 billion years per cycle.
It helps to actually include the units in your math as "unsolvable variables" that cancel each other out in your conversions. It's a fairly easy way to make sure the math comes out correct. Granted, this extremely rough number is kinda interesting because it is less than 10% off from
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You did the math wrong. 74.3 / 3.08567758e19 is approximately 2.4e-18 Hz.
This is how frequently the universe doubles it current size at the current rate of growth.
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From my understanding, speed is relative, so the terms the relation of the two objects, the one being measured from and the one being measured to. As those speeds (relative) approach Light, that is when we can start seeing other interesting effects, like space curving. Space curving is what really boggles the mind, because it is, and isn't curving, depending on what you are looking at, because the "speed" is what bends our perception.
Re:Units (Score:5, Interesting)
Interestingly, some back of the envelope calculations (using rough numbers ... 300000km/s for c, 75km/s/mpc for Hubble's Constant, and 3.25 ly/pc) gives a value of roughly 13 billion light years for the recession velocity to approach c. 13 billion years is also *ROUGHLY* the age of the visible universe.
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Oops... that' 75km/s/Mpc, not mpc.
Re:Units (Score:4, Informative)
No, a *parsec* is 3.26 light years. A Megaparsec is 3.26 MILLION light years.
Gem Secretes as Superman (Score:3, Funny)
Ok. Now what is it in hogsheads per fortnight? (Score:2)
ha
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You're units are incompatible. I think the units you wanted were football field lengths per fortnight per furlong.
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hmm...
Partially right. but the universe expands in 3d, not just linearly.
What is the answer for hogsheads per fortnight per displacement of Archimedes in a bathtub.
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Hogshead per fortnight (equivalent to m^3/s) is the wrong unit of measurement for expressing the expansion of the universe. I'd go with 2.4 +/- 0.068 exaHz for a whimsical and opaque way of expressing it.
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If you want the expansion as a volume you could use m^3/(s*m^3), i.e., rate of volumetric expansion per volume of space. m^3/s just gives you a rate of volumetric expansion, it doesn't say anything about the volumetric expansion being faster if you look at a larger volume, or equivalently, things move faster away from you the further away from you they are, i.e., m/(s*m), which is what Hubble's Law is all about.
You can of course calculate the expansion of af known volume of space e.g. the entire universe* o
Not to be pedantic (Score:3, Insightful)
The visible part of the universe is expanding. We have no clue what's happening to the infinitely large part we can't see.
Re:Not to be pedantic (Score:5, Insightful)
Well, to be pedantic, its a stretch to say "we have no clue". We can make some pretty damned good guesses.
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Well, there is the dark [slashdot.org] flow [wikipedia.org], a mysterious influence on the motion of distant galaxies whose cause can no longer be observed because it has presumably passed beyond the visible universe. However, we can still see the results of its effect on stuff that is still in the visible universe.
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Its things like this that we've confirmed as accurate as much as we can that makes me think the universe isn't expanding at all, we're just able to see more of it all the time. The current size of the universe closely correlates with the speed of light and the time it would have taken that light to reach us... coincidence?
Space itself is supposedly able to expand faster than the speed of light, however I'd like someone to point me to the evidence that this is happening at all.
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Doppler shift. Seriously.
Light can experience doppler shift like sound can (well, really any wave can see a doppler shift). So if two objects are moving away from each other, light from one to the other will be red shifted. If two objects are moving closer together, the light will be blue shifted.
Since chemicals have known spectral emission/absorption lines, you use that data compared with your observational data of distant objects to figure out the actual shift. Add in some math and you can even figure out
what's in a name? (Score:2)
It's not called "expansion rate". It's called "the Hubble constant".
Sorry for sounding stupid... (Score:2)
Someone enlighten me please.
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If you shine a laser pointer at the sky (not airplane), the beam leaves earth, and about 14 billion years the beam will reach the farthest galaxies we can see. What happens after another 1000 billion years? Will the beam curve back on itself? Will it slow down and go only at the rate of expansion? But, if the beam just keeps on going at c---it would be beyond the ``visible edge'' of the universe, no? Wouldn't that imply that the `non-visible' real edge of the universe has to expand at least at 'c' or else y
Sure, but ... (Score:2)
the expansion rate found was 74.3 +/- 2.1 kilometers per second per megaparsec
... what is that in something useful, like Library of Congresses?
Megaparsec? (Score:2)
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Nope. Edwin Hubble didn't believed in Big Bang (Score:2)
Edwin Hubble was very sceptical about, so called "Big Bang" theory and claimed that there might be different explanation of redshift effect which he observed.
``Astronomer Edwin P. Hubble says that after a six-year study, evidence does not support what we now call the Big Bang theory, according to the Associated Press. “The universe probably is not exploding but is a quiet, peaceful place and possibly just about infinite in size.''''
Check this paper too:
http://arxiv.org/PS_cache/arxiv/pdf/1107/1107.248 [arxiv.org]
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Seeing as.... (Score:2)
Seeing as we can not see the edge of the universe from where we are....
how can we really tell if yesterday the edge was 1.2 km less then it is today?
Are we saying that all objects are moving away from each other at that rate?
Of course not, they have gravity and orbits and all that....
so what are they using to gauge the edge of the universe has extended from yesterday?
Seriously! I want to know
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I am not sure about that, who is to say how much further out the edge of the universe is from the very first galaxy that we may record, or maybe we still have yet to actually be able to see the first galaxy seeing as it is so far away, so we could be way off if we just use the distances between us and the galaxies, vs. the actual measurement of the edge to us...no?
I am no mathematician, but it seems that everything is theoretical at this point in terms of what we THINK we know and what is fact, hence my ori
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I know about this, and am very aware that this practice is used, however, I also know they estimate that the distance betwen the earth and say star 1 is at xx km per second, but 2 things pop into question.... can we use the same formula for something that does not behave the same as stars, we are not talking about an actual object moving in space, but we are talking about a virtual(is it really?) edge of the universe, from which we assume on the other is nothingness, therefor could we really say this object
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In terms of only km, each second the distance 415,299,808,882,907,133 km expands by 1 more km.
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That frequency is 1/13billion years.
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I don't know. It corresponds roughly with the age of the universe, and also with the limit at which the recession velocity approaches c.
I'm just a dilletante. You'd have to ask an astrophysicist what the significance of that value is, if any.