Chandra Provides Support For Dark Energy 350
starannihilator writes "The Chandra X-Ray Observatory has provided new evidence supporting the existence of dark energy, the force causing the acceleration of universal expansion. The new findings support the theory that the universe will expand forever, provided there is enough dark matter. CNN and Newsday are running the story, originally reported by NASA. Chandra's site has some good images and information on the three galaxies clusters studied (Abell 2029, MS2137.3-2353, and MS1137.5+6625)."
Dark matters (Score:5, Funny)
I am eagerly awaiting the next annoncement where someone again finds evidence to refute the dark matter claims. It seems like the science; "Dark Matter is like this" - "No, it can't be, actually it's like that". Is not going to end soon.
Join me. Come to the dark side, and together, we will expand the universe.
Re:Dark matters (Score:2, Funny)
Re:Dark matters (Score:3, Informative)
Re:Dark matters (Score:5, Informative)
The only articles I've seen that make statements like that are the commentaries on the commentaries on the dumbed-down press releases on the actual publications.
What's actually been happening is more along the lines of:
"There's a discrepency between galactic models and observations. What did we get wrong in the model/what needs to be added?"
"Maybe A? B? C? D?" "Let's try to test them and see."
"Not A, not D, but maybe B, maybe C." "What kind of B or C? B1? B2? B3?" "Let's try to test them and see."
"Our models only work if we have B _and_ C, and we've ruled out C1 and C2, but C3 still works."
"What kind of C3?"
"New observations show a new effect in addition to the old one. How do we explain it?"
"Maybe E? Maybe F?"
[Etc.]
This is a process of examining many possible explanations, and weeding out the ones that don't work until we have reasonable confidence that the ones left _do_ work.
We've gone from "galactic rotation doesn't match models based on stars alone, what could be causing this?" to "we know that there's about X amount of normal matter we aren't seeing, Y amount of abnormal matter that we aren't seeing, and that the properties of the abnormal matter fall somewhere in this range (that's wide but being narrowed)". There's surprisingly little backtracking. Tests that detect or fail to produce evidence for dark matter of various types all help to increase our understanding of what dark matter's actual properties are.
As for dark energy, if anything, it would be surprising if something like it _didn't_ exist. We already knew that a scalar field with similar properties was likely present in the early universe, and several models proposed universes where the _absence_ of the field was only a local effect. Even relativity contained a similar type of effect that was set to zero a priori as opposed to forced to zero through a mechanism inherent in the model.
We're still sifting through the myriad of possibilities, but we certainly are learning something each step of the way.
Re:Dark matters (Score:4, Interesting)
So does anybody have a good,cheap,quick (pick two) primer on Quantum Physics? Something that can explain what we do know, along with the outstanding issues that we don't know?
Re:Dark matters (Score:3, Informative)
Not offhand, but a couple of good places to look would be to check the various online bookstores for quantum mechanics textbooks to see what are recent/available and get good reviews, and course pages at various universities to see what textbooks they use and what online resources they have available. Expect to pay $100 or so for a g
Re:Dark matters (Score:2, Informative)
Now, with this story, it's back again.
Re:Dark matters (Score:5, Insightful)
Anyway, since it's not very likely that the knowledge of dark matter will have a significant impact on the daily life anytime soon, relax and enjoy the (slow-moving) show.
"Dark matter" != "Dark energy" (Score:5, Informative)
Re:"Dark matter" != "Dark energy" (Score:3, Funny)
(dark)E=(dark)m*c^2
Re:"Dark matter" != "Dark energy" (Score:5, Funny)
That's not quite right, it should be:
(dark)E = (dark)m * (dark)c^2
where (dark)c is the "speed of dark", and we all know the speed of dark is faster than the speed of light [msu.edu]. Therefore, (dark)c > (light)c and therefore dark matter holds more (dark) energy than normal matter hold in (light) energy.
Re:"Dark matter" != "Dark energy" (Score:5, Funny)
Re:"Dark matter" != "Dark energy" (Score:3, Funny)
Re:"Dark matter" != "Dark energy" (Score:5, Informative)
Dark matter is normal matter. "Cold dark matter" has a pressure of 0 (or very low in relativistic terms), just like all regular gas, stars, planets, etc.
Dark energy is freaky. It has *negative* pressure.
The two are extremely different things.
-Rob
Re:"Dark matter" != "Dark energy" (Score:5, Insightful)
Depends on which theory of dark matter you subscribe to. I don't think WIMPs [eclipse.net] could be considered "normal" matter.
Re:"Dark matter" != "Dark energy" (Score:3, Interesting)
Photons are normally considered to have zero mass, and to be the smallest possible unit of energy.
Yet, they are also "negative", are they not? That is, they move away from their source.
Yet, if a photon will be absorbed by some types of objects, bounce off of others, and simply pass through others - it must have some sort of mass. Where does a photon go when it's energy is spent?
There must be a near infinate supply of photons that hav
Re:"Dark matter" != "Dark energy" (Score:5, Informative)
Some responses...
Check... although photons can have almost any energy. Low-frequency photons (think IR) have low energy, and high-frequency photons (think gamma rays) have high energy.
I have no idea what you're saying here. Photons have no charge and no mass. They are not "negative" in any sense of the word I'm familiar with. One of the fundamental properties of photons is that they are always moving at the speed of light - that's why they move away from their source.
Why must it? If you begin to study physics seriously, one of the first pre-conceptions you'll have to let go of is that your "common sense" can be trusted to tell you how things behave in the quantum world. Photons have no mass.
A typical fate for a photon would be for it to be absorbed by an atom. In the process, the photon's energy is put into raising one of the atom's electrons from a lower energy state to a higher energy state.
No. All photons have a non-zero energy which equals something like h * f, where h = Planck's constant and f = the photon's frequency. I may be off by a factor of 2 pi... it's been a long time since I took Modern Physics!
Hope this helps.
Sean
Re:"Dark matter" != "Dark energy" (Score:5, Informative)
Dark matter, on the other hand, is the name confusingly given to a number of unsolved phenomena. By looking at how the outer parts of galaxies rotate, we get a sense of how much matter is in a given galaxy, as well as its distribution. It seems that there is a great deal of matter in the outer regions of galaxies that does not 'glow' like stars do. In addition, by studying how galaxies move in clusters, we strengthen the case for lots of matter existing between galaxies that is invisible to us. The candidates for this dark matter are many and varied, from innumerable Jupiter-sized objects to cold white dwarfs to small black holes. Current observations are undertaken to rule in or out some of these. Even so, standard Big Bang theory predicts an upper limit to the amount of "ordinary" (baryonic) matter present, so it is possible that some of this dark matter might be weird stuff.
Re:"Dark matter" != "Dark energy" (Score:4, Insightful)
It also means that photons do act as a source of gravity, with a strength equal to something with a mass of E/c^2. But in the current universe, their gravitational effect is tiny compared to the gravity of the mass... as a little exercise, try calculating the equivalent rest mass of the entire luminosity of the Milky Way and compare it to the mass of the moon.
[TMB]
Re:Dark matters (Score:5, Insightful)
When we can't explain something we are sometimes better off makeing something up that fills the gap until we can find the more correct answer. There is no such thing as exact science. Only reproduceable observation which eventually becomes accepted fact. Although there is no reason for it to always stay fact if someone says, "Hey, I tried to do the experiment and used this method to test it and I got a diffrent observation!" Well, now it's time to re think that scientific fact.
What happens typically is that the person is downplayed as doing something wrong, adding some new variable to the mix, or something that would throw off the observation in some way. Politics in science is as complicated and painful as anywhere.
Re:Dark matters (Score:5, Funny)
Re:Dark matters (Score:4, Funny)
Actually, a step function would more annoying to scientists -- no trends to follow. Plus it would be more consistent with religious beliefs, particularly if there is a step down function coming up.
Re:Dark matters (Score:4, Insightful)
Because if they did, they'd be theologians, not scientists.
Re:Dark matters (Score:4, Funny)
Re:Dark matters (Score:3, Funny)
Re:Dark matters (Score:3, Insightful)
Because, by their very nature, they need proof?
Hmm that name sounds familiar (Score:4, Funny)
Re:Chandra == Moon (Score:3, Informative)
Dakr Matter (Score:4, Interesting)
Re:Dark Matter (Score:4, Insightful)
Or at the very least it would be awfully hard to see some of those distant galaxies.
the universe was expanding at the speed of light (Score:5, Funny)
Whenever life get's you down, Mrs. Brown
and things seem hard and tough,
and people are stupid, obnoxious or daft,
and it feels that you've had quite enough---
Just remember that your standing on a planet that's evolving,
revolving at 900 miles per hour.
It's orbiting at 19 miles per second, so it's reckoned,
a sun that is the source of all our power.
The sun, and you and me and all the stars that we can see
are moving at a million miles a day,
in an outer spiral arm at 40,000 miles an hour,
in this galaxy we call the milky way.
The galaxy itself contains 100 million stars,
it's 40 thousand light years side-to-side.
It bulges in the middle 30 thousand light years thick,
but out by us it's just 3000 light years wide.
We're 30 thousand light years from galactic central point,
we go round every two hundred million years
And our galaxy is only one of millions and billions
in this amazing and expanding universe.
Musical interlude
The Universe itself keeps on expanding and expanding
in all of the directions it can whizz.
As fast as it can go, the speed of light, you know
A million miles a minute and that's the fastest speed there is.
So remember when your feeling very small and in-secure,
how amazingly unlikely is your birth.
And prey that there's intelligent life, somewhere out in space,
'cause there's bugger-all down here on Earth.
Attribution for the above lyrics to Eric Idle.
But seriously... (Score:3, Interesting)
I should point out here that it's also been theorized that the center is in fact pulling things back in - but this is an old theory, that hasn't gotten much press lately.
The accelleration of the expansion is about the inner layers of the universe accelerating to match (more closely) the speed of the outer edge.
So,
Re:But seriously... (Score:3, Informative)
The balloon surface analogy is a 2D example. Yes, there's a center and edge to the balloon, but that's in 3D. The surface doesn't have an edge. Similarly in 4D, the universe can have a center and edge, and does when time is the fourth dimension, but that is measured in time and not in 3D space. In that case, current time is t
Re:Dark Matter (Score:3, Informative)
The reason for this provide in the sibling response.
Re:Dark Matter (Score:5, Interesting)
Now blow the balloon up a little more such that P0 and P1 are 1mm further apart, and thus P1 and P2 are also 1mm further apart (P0 and P2 are 2mm further apart). Then (D=distance, dD=change in distance):
dD01/D01 = 1mm/10mm=0.1
dD12/D12 = 1mm/10mm=0.1
dD02/D02 = 2mm/20mm=0.1
i.e., dD/D = constant. Since the dD occured over the same time for the two distances, you can also write this as
(dD/dt)/D = V/D = constant = K
(This is the Hubble equation, where K=H.)
So, in theory, you could blow up a balloon such that two points are moving faster than c relative to each other (V=c=D*K). Let's see how to do this. The distance between any two points on the surface is D = r*Q (r=balloon radius, Q = angle between the points in radians which stays constant as the balloon expands). The change in distance over time is
dD/dt = V = dr/dt*Q.
The furthest two points can get apart is Q=pi (opposite points on the balloon), hence the fastest relative velocity will be between these points. Let V = c and solve:
dr/dt = V/Q = c/pi
In other words, if the radius of the balloon was expanding at a rate of just under 1/3 the speed of light, two points on the balloon would be moving relative to each other at the speed of light. (This would not only take a lot of air, but the rate of air required would go up with the cube of the radius, so you'd want to do this when the radius is very small.)
Applying this 2D analogy to the 3D universe, it doesn't have to be expanding at the speed of light for two distant points to be moving greater than c relative to each other. But it does have to be expanding above a certain rate to achieve this. If it's expanding slower than this critical rate, no two points can be moving faster than light relative to each other. If it's expanding faster, they can. Since the expansion seems to be accelerating, it seems inevitable that it will happen at some point if it hasn't already.
We should also be able to figure out if it has already happened or when it will. We know the constant H (from the Hubble equation H = V/D). (It's easy to calculate anyway, given the distance to any star and it's measured relative velocity.) If we know the history of the expansion rate we know how big the universe is, i.e., this furthest distance Dmax between any two points. We can then solve the Hubble equation V = H*Dmax and see if it is less than or greater than c.
By the way, I don't think this violates relativity, it doesn't say anything about the rate of expansion of the universe. I think this falls into the "warp" concept of traveling faster than the speed of light, i.e., if you can locally expand the universe fast enough, it appears you are moving away faster than the speed of light, and vice-versa if you can contract it fast enough locally it appears that you are approaching faster than the speed of light. I could be wrong about that though.
Re:Dark Matter (Score:3, Interesting)
Tachyons do it all the time. Literally. Just as us tardyons with real rest mass have the speed of light as the upper limit of our velocities and luxons with no rest mass are always moving at the speed of light, tachyons with imaginary rest mass have the speed of light as the lower limit to their velocities.
Nobody's found any yet, but the math says they should be there and nobody's figured out how to disprove them, either.
Re:Dakr Matter (Score:3, Interesting)
Re:Dakr Matter (Score:3, Insightful)
Re:Dakr Matter (Score:3, Interesting)
Re:Dakr Matter (Score:2, Insightful)
Re:Dakr Matter (Score:5, Informative)
There are quite a number of valid GR metrics which describe space which expands faster than the speed of light, and in fact, it's thought that it did expand faster than the speed of light during the inflationary period.
Those same metrics are the basis of the Alcubierre metric, one of many ways to generate faster-than-light travel without multiply-connected spacetimes (wormholes). Like most "violate the speed of light" metrics, it requires negative energy density matter, though variations on the metric allow for very tiny amounts of negative energy matter to generate it.
Re:Dakr Matter (Score:3, Interesting)
True, but irrelevant. Within the Swartzchild radius, nothing can escape a black hole's gravity. Period. Doesn't matter if it is travelling at 99% the speed of light or 99.999999999999999999999999999% the speed of light relative to the black hole, it still can't escape.
The entire universe crammed into a small space would have one hell of a Swartzchild radius, and no
Re:Dakr Matter (Score:5, Informative)
No offense, but that's not how relativity works. The thoery of Relativity posits that all measurements are taken from some frame of reference, and it is impossible for an object to go faster than light for any frame of reference.
So, if I'm on a spaceship going 99.9999999% the speed of light from the frame of reference of the earth. However, from the frame of reference of my spaceship, I'm stationary. Now, I can run as fast as I want in any direction, I can even sit in the back of my space ship with a super-powerful gun that shoots bullets at 99.9999999% the speed of light, and fire a couple rounds towards the front of the ship. From the frame of reference in the ship, the bullets will travel at 99.9999999% the speed of light, even when the ship is travelling at 99.9999999% the speed of light in reference to the earth.
But here is where it gets wierd: an observer on earth will not measure the speed of the bullets to be travelling 199.9999996% (99.9999999%x2) the speed of light, they will be measuring the bullet to be travelling just over 99.9999999% the speed of light.
This is because, from the viewpoint of someone on earth, the space ship will be very short, which means even if it still traverses the length of the ship in the same amount of time as it does from the viewpoint of me on the spaceship, it will not have travelled the same distance, which (since v=d/t) means the bullet didn't travel as fast relative to the spaceship (from the viewpoint of earth) as it did from the viewpoint of someone on the spaceship.
Additionally, from the viewpoint of Earth, time is travelling more slowly on the spaceship, which enhances the effect even more.
It's confusing if you don't have a handle on it, but none the less, this is how the theory of relativity works.
Re:Dakr Matter (Score:4, Informative)
I don't, but "Brief history of Time" [amazon.com] by Hawking or "The Elegant Universe" [amazon.com] by Green have pretty good explanations of relativity.
Actually, I'd recommend trying a book written by Einstein called "Relativity" [amazon.com]. I've also heard it referred to as "the short book" because apparently he wrote two, one in laymen's terms, and one filled with math/equations. If you really want to go hard-core, you can read his original papers, but takes a bit of work to get through, and it helps if you have a big physics background and are familiar with Maxwell. "Relativity" isn't too hard to understand, though. Plus, it's generally true that you'll never get such a dead-on explanation of a theory as when you get an explanation from the guy who came up with it. I've met a lot of modern physicists whose grasp on Relativity has been corrupted by hearing poor explanations. No risk of that if you go to the source (Einstein).
Re:Dakr Matter (Score:3, Informative)
Yes, and that 4th dimension would be called time. The "center" of the balloon would be the equivalent of the big bang, but as you say there is no "center" in the normal dimensions, i.e.,
Re:Dakr Matter (Score:4, Informative)
> speed of light
I don't think the acceleration in on the order of c^2, if that's what you mean. What they mean is that due to acceleration, some space (the stuff that's furthest away) is expanding at close to c.
Re:Dakr Matter (Score:3, Informative)
This is effectively how the Alcubierre warp drive works.
Re:Dakr Matter (Score:2, Informative)
Expansion of universe (Score:5, Informative)
No. The expansion of the universe refers to the fact that distant galaxies are moving away from us, and that the farther they are, the faster they are moving. This is expressed by the Hubble constant [utk.edu], which has a value of about 50 km/s/Mpc.
The acceleration of the expansion is reflected as this "constant" increasing with increasing distance.
The acceleration is caused by Dark Energy, not Dark Matter.
Dark Matter is either normal matter or subnuclear matter that makes its presence felt as increased gravity, but is not directly observable.
Dark Energy is not well understood at all.
Re:Dakr Matter (Score:5, Informative)
I should also point out that "Dark Matter" and "Dark Energy" are COMPLETELY DIFFERENT THINGS (as far as we know). Astronomers have just named them both "Dark" because they don't know what they are. They both also affect the expansion of the universe, but dark matter is slowing down the expansion of the universe (presumably via gravity) and dark energy is accelerating the expansion of the universe (by some yet-unknown force). Dark Matter is weird, but at least it seems to sortta obey the rules of the universe (i.e. gravity); dark energy is completely unlike anything we've seen before.
Dark energy (Score:3, Insightful)
Well, except that Einstein had already predicted it in his original formulation for the theory of relativity.
Re:Dakr Matter (Score:3, Informative)
(2) the space-time fabric of the universe is not an object anyway, so FTL rules do not apply
It is actually possible for 2 objects to move apart faster than the speed of light even though neither is moving FTL compared to the other. This statement seems to be nonsensical, until you realize that the expansion is a 4D effect. Think of the galaxies (in 2D) as though they were on the surface of a balloon (2D). Now imagine the
Re:Dakr Matter (Score:3, Informative)
Re:Dakr Matter (Score:3, Informative)
Re:Dakr Matter (Score:2)
Re:Dakr Matter (Score:5, Interesting)
This isn't even strictly true. You can violate global speed-of-light travel times without violating local speed-of-light travel times by making space itself move - see the inflationary period, or the Alcubierre metric for more info.
You can imagine it as a speed limit placed on people walking, but there is no such speed limit on moving walkways (like in airports).
And the problem with particles traveling faster than light (tachyonic) is the fact that as they *lose* energy, they go faster, which makes them lose more energy, so they spiral out to infinite speed. Tachyonic modes are unstable, so a theory containing them typically undergoes tachyonic condensation (spontaneous symmetry breaking) and the tachyons gain a positive mass squared.
Re:Dakr Matter (Score:2)
> already traveling at the speed of light to begin with.
I've never heard of the possibility for a photon to travel faster than c, where c is speed of light in vacuum. What is the basis for this? Also, does a photon ever really accelerate anyway? Do bosons and fermions really have the same relativistic physics?
Re:Dakr[sic] Matter (Score:4, Funny)
Re:Dakr Matter (Score:3, Informative)
perspective problem (Score:5, Funny)
I'd like to think we live on an electron in orbit around the proton of a molecule as part of a giant coffee mug -- our universe is expanding due to some even bigger geek having just poured hot coffee in our universal mug.
It's "dark" cuz that's how this geek likes his coffee.
Re:perspective problem (Score:2, Interesting)
Apparently the astrophysics bunch had evidence about the expanding universe already, I think this helps corroborate other evidence.
But I guess we'll never know for sure until it happens, so I guess we'll have to wait and see.
Re:perspective problem (Score:4, Funny)
Is he related to Jerry Seinfeld?
Goofy gravity (Score:4, Interesting)
Gravitation is a shadowing effect. (Yes, all the formulae still work, except when you get out towards the edges of space)
--Mike--
Re:Goofy gravity (Score:3, Interesting)
Re:Goofy gravity (Score:3, Funny)
This only works for however long the LSD lasts.
Re:Goofy gravity (Score:3, Insightful)
I hope there's enough. . . (Score:3, Funny)
3000 Gil (Score:2, Funny)
Ptolemy's back! (Score:5, Interesting)
Increasingly complex adjustments [utk.edu](e.g. epicycles) were made to Ptolemy's system to explain the observed motions of the heavenly bodies. Then along comes Copernicus and tells us that we've been looking at it inside out all along, things are simple after all, we just have to adjust our viewpoint.
I think physics is overdue another Copernicus.
Re:Ptolemy's back! (Score:3, Insightful)
Re:Ptolemy's back! (Score:5, Informative)
You are quite right.
Here is a synopsis of signs that things are due for a big shakeup:
The last two are probably not mandatory, but most people feel like any general theory should account for those two things.
Re:Ptolemy's back! (Score:3, Informative)
Actually, Ptolemy may be one of the great under-appreciated physicists in history. Everyone's always making him out to be the poor fool, but in another view, his work is really astounding.
Ptolemy had successfully been able to plot the motions of the stars, planets, sun, moon, etc. If I remember correctly he even guages the distances pretty well.
He had also correctly calculated variables for all the motions, only thought they were different things. What I mean by that is that he had calculated the value
Re:Ptolemy's back! (Score:3, Informative)
This model had been rejected by other philosophers at the time, but the meme was out there even then.
Re:Ptolemy's back! (Score:3, Interesting)
The universe is expanding right near the minim
Headline is an Exaggeration (Score:5, Insightful)
So what, we have more evidence the universe is expanding at an accelerating rate. WE ALREADY KNEW THAT! This is just another indication that it's happening. This doesn't "prove" the existence of dark energy. It's still entirely possible (and I would suggest probable) that we just don't know the entire story about gravity. Physicists have gotten gravity wrong before after all.
My general theory of exansion..... (Score:2)
In fact my general theory states that any container will keep expanding as long as you keep stuffing enougth material into it.
Can I have my Nobel prize now please?
Dark Energy not Dark Matter (Score:5, Interesting)
Disappointment (Score:3, Funny)
What, no pictures of "dark matter"?! That I'd call an announcement!!
Dark Energy was proven before (Score:4, Funny)
Big Rip vs. Black Holes (Score:4, Interesting)
Would this apply to black holes, as well? If black holes aren't ripped apart, would they continue to provide areas of gravity strong enough that particles in the vicinity don't undergo the rip?
Welcome to Cosmology Update. (Score:3, Funny)
Hey, I rubbished Micro$oft and the whole of modern cosmology in one post. Cool.
Left over matter/energy from another dimmension (Score:5, Interesting)
The relief (Score:3, Funny)
>The new findings support the theory that the >universe will expand forever
I was afraid that the universe would stop expanding and start collapsing and that would kill us all!
Why not oscillation rather than expansion? (Score:3, Insightful)
Re:Why not oscillation rather than expansion? (Score:5, Interesting)
Re:Why not oscillation rather than expansion? (Score:3, Interesting)
When all the stars burn out, space will start collapsing again as energy falls into black holes.
No. This is not how gravity, according to general relativity, works. The curvature of spacetime is, roughly speaking, proportional to its local mass/energy content. In fact, converting things into black holes doesn't change the curvature of spacetime to any substantial degree once you are more than a few Schwar
Re:Why not oscillation rather than expansion? (Score:4, Insightful)
dark energy and energy conservation (Score:5, Interesting)
Re:dark energy and energy conservation (Score:5, Informative)
Just a quick reply to this. I'm a graduate student doing computational astrophysics - in particular, cosmological structure formation (galaxies and such). The law of conservation of energy is only valid in closed systems. If the universe isn't a closed system - if there's something 'outside the universe' which is adding/subtracting energy - then energy doesn't necessarily have to be conserved. Also, there are some cosmologists that believe that energy is not conserved on cosmological scales, so the law of conservation of energy is not valid on all scales. I suppose it's fair to say that as of right now, dark energy appears to result in the non-conservation of energy on very large scales, given our current understanding of particle physics. However, there is almost certainly a lot going on that we don't really understand, so it's an open problem.
I hope that helps!
Could we be seeing the vascilation of branes?... (Score:4, Insightful)
It may be possible to have a universe that is expanding and contracting at different times based on variables we have no ability to measure, hence never be able to know which way we are going to go, only where we seem to have gone.
For some great educational sources for the non-astro-physicist, see The Elegant Universe [pbs.org] excellent program (my six and ten year olds understood most of it). A few other articales are at Sky and Telescope [skyandtelescope.com] and Scientific American [sciam.com]
InnerWeb
Universal Catapult (Score:4, Insightful)
Not that I have an a fraction the knowledge or mathematical skills of these scientists; but correct me if I'm wrong.
Doesn't gravity effecct objects regardless of the distance between them? Meaning to say, that gravity, however weak, will always have this attractive force.
so, won't this energy causing this accelerating expansion eventually burn up/out?
couldn't the universe be Like the release of a stretched-out, very long rubber band (played back in slow motion). At first release starting from a velocity of 0 and then accelerating. but after expending it's energy, slowing? heck, then even retracting?
in other words, what evidence supports that this thing is going to expand at an accelerating rate forever? seems like gravity is going to get a little upset about that eventually.
Re:Universal Catapult (Score:4, Informative)
Doesn't gravity effecct objects regardless of the distance between them? Meaning to say, that gravity, however weak, will always have this attractive force.
so, won't this energy causing this accelerating expansion eventually burn up/out?
The amount of gravitational energy between two objects is a static amount that can be determined. The amount of energy in kenetic motion can also be determined. As two objects move apart the gravetational potential grows while the speed they are traveling away from eachother decreases. If the kenetic energy is greater than the gravatational energy, then the two objects will continue to move apart. If the gravetational energy is greater than the kenetic energy causing them to separate, then their realative motion away from eachother will slow, stop and then they will begin to come back together. This is basically an explantion of escape velocity that you always hear about in rocket launches.
A condensed explantion of what would take too long to describe here in full basically says that the average kentic energy that the obejcts in the universe has been determined as well as the average gravatational energy. If the gravetatinal energy was greater then everything would eventually come back together in what is known as a "big crunch", but the kenetic energy is greater and thus the universe will continue to expand.
Now part of this probelms comes not from actual kenetic energy, but due to that space itself is increasing. So the distance between two objects is increasing proportional to the distance between them. the rate at which this is occuring also seems to be growing. This is the acceleration of the universe you are reading about here. Reasons for this are nt well known, but one theory is that there are something like 11 total dimentions and the other 7 after three spacial and time are shrinking, causing the others to expand. These other seven are already so small that they haven't been detected yet (we're way off in string theory territory here).
If this acceleration continues to increase, then eventually the rate at which space is expanding might grow so large that it will overcome not only gravity but even the other forces that hold atoms or particles together. This senario where everything is torn apart into component parts is called the "big rip".
Re:Universal Catapult (Score:4, Informative)
Which is exacly why scientists have postulated the existance of dark energy. You see, you're correct, the effect of gravity does suggest that the universe's expansion should be decelerating. But it's not. All of our observations say that it's accelerating. Most cosmologists would say that's it's pretty much a confirmed fact at this point. The cause of this acceleration is unknown. They're postulaing the existance of this 'dark enery' which exerts some sort of repulsive force.
Enistien actually came up with the idea first, but for a completely different reason. He didn't call it dark enegry though (I don't think), it was just a variable that he added to his equations to force the overall 'shape' of the universe's space-time to be flat. He later took it out because he thought it was stupid; it was much more logical to assume the universe wasn't flat, in which case it wasn't needed. However modern day measurements of the Cosmic Background Radiation [uchicago.edu] have given very strong evidence that the universe is actually flat. So now they've put the variable back into his equations, and they're working on trying to prove it's existence.
Summary of technique (Score:5, Informative)
Here's a quick summary of the technique:
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MNRAS article (Score:3, Informative)
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Re:Summary of technique (Score:3, Informative)
My favorite Abell object (Score:3, Interesting)
Er, I mean Nibbler. Oh never mind... (Score:2, Informative)
Not understanding science (Score:3, Informative)
>everything it states about ratios and measurements involves assumptions. This isn't science.
Yes, it is science. There are observations made that are attempting to confirm or disprove predicitons made consistent with their hypotesis. As for your distaste for the choice of language, particularly the weasle words; that's the way scientists write.
"Recent observations of a massive shockwave, intense gamma, beta, and alpha radiation, together with so far unrepeated visual observations of what is thou
Re:Serves the Palestinian rabble right (Score:3, Insightful)
Heh, and you still wonder why people hate fundamentalist nutters like you. It's weird that fundamentalist muslims and orthodox jews are at each others' throats... You have more in common then you are different