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Dark Matter Measurements
ksp0704 writes: "According to this article at space.com, scientists have finally measured the approximately 90% of the universe we can't see (the dark matter)." I'm sure it will continue to be a topic of debate for years, but two independent measurements agreeing is a good sign.
Pardon me, but we can apparently only see certain bits & pieces of the universe, right? So, how the f*ck is it that we know exactly how much ELSE there is out there? Isn't this like saying "I have 3 Weezer albums, and I just figured out the names of the songs on their 4th, 5th, and 6th albums (even though I have NO IDEA how many more albums they'll make) and I now know the name of every Weezer song.
If you celebrate Xmas, befriend me (538
Figuring that Excite got /.'ed here:
"Astronomers Celebrate Reliable Measure of Dark Matter
By Heather Sparks
Staff Writer
posted: 12:48 pm ET
29 October 2001
Scientists are closer than ever to balancing the
checkbook of cosmic matter. This is because two recent independent measurements of normal matter in the universe are in agreement. The results further strengthen the case for the Big Bang theory and for the nature of the universe as astronomers understand it today.
The universe contains normal atomic matter, what makes you, your dog, the stars, and everything in between. Normal matter is what Carl Sagan was talking about when he said we are all star-stuff.
But in addition to star-stuff, there is invisible dark matter that is known only because the universe is denser than normal matter alone, as evidenced by how structures, like clusters of galaxies, are bound together by gravity. Even individual galaxies don't have enough normal matter in them -- that which can be directly detected -- to keep them from simply flying apart.
Now, through different measurements of conditions existing at the very start of time, astronomers are beginning to see the light.
"There is more than one way of measuring the total amount of matter in the universe," said astronomer Brian Fields from the Center for Theoretical Astrophysics at the University of Illinois, Urbana-Champaign. "And if you have an idea of how much normal stuff there is to all the universe, then you know how much other stuff there is, too." Creation of normal matter
All the "normal stuff" is thought to have been made in two steps, one occurring when the universe was roughly three minutes old, and the other some 300,000 years later.
According to the leading theory, an enormous nuclear explosion called the Big Bang happened 13 billion to 15 billion years ago. From it, the universe appeared in an instant, but as a billion-degree mess of neutrons, protons and electrons. The explosion was so energetic that nothing could come together close enough, for long enough, to form atoms. But the universe expanded and cooled so rapidly that within three minutes protons and neutrons bonded in twos and fours, and formed all the atomic nuclei in the universe. This Big Bang Nucleosynthesis determined how much normal matter would ever exist.
Just how much matter that was can be estimated from observing the most recently formed stars and galaxies, because they are fueled by the hydrogen atoms formed from those original nuclei of twos.
Fields explained that young stars, like our Sun, are just now fusing that original hydrogen into helium whereas older stars fuse helium into oxygen and iron. Because the hydrogen fuel has not been converted, scientists are able to measure the proportion of original normal matter to dark matter.
"Stars change the amount of hydrogen and helium in the universe," he said, "and we want to know what the Big Bang did. So we have to find places where pollution from stars is minimal" to estimate the original amounts of normal and dark matter.
But before any stars could form, hydrogen atoms had to exist. This took 300,000 years after the Big Bang Nucleosynthesis the universe had to cool down enough so that electrons could bind with the nuclei.
Once this happened, there was a curious side effect: the creation of light in the Universe. Unbound electrons scattered the UV radiation from the Big Bang, but once the electrons were bound, the radiation was allowed uniform movement, thus, light was finally released in the young cosmos.
This light has existed since then, travelling along the edge of the universe, stretching and weakening into a still measurable microwave radiation, called the Cosmic Microwave Background, or CMB as astronomers call it.
Weak attraction
At the time of the original release of light, dark matter had congregated in clumps, which created small fields of gravity that eventually pulled in normal matter as well. Images of the CMB are therefore mostly smooth, but have spots, or wiggles, of slight variation, a result of the dark and normal matter pooling together.
"The nature of these 'wiggles' is basically saying how the normal matter was responding to that crazy dark matter," explained Fields, "by amplifying the places where the extra density was."
The CMB, most recently measured by highly sensitive probes in Antarctica, therefore gives a detailed measure of the proportion of normal to dark matter.
Phenomenally, both the measurements of young galaxies and of the cosmic microwave background showed that normal matter makes up just one-tenth of the universe. The rest must be dark matter, researchers say. Fields, who wrote about this astronomical agreement in the Oct. 19 issue of the journal Science, explained why this is causing astronomers to "bring out the bubbly."
"It didn't have to be true," Fields explained, "because they're completely independent things. It's just gorgeous that they agree with each other."
Earlier studies had showed that dark matter made up anywhere from 85 to 95 percent of the universe. Only now do the two different measures of dark matter agree. Now, 90 percent of everything is known to be virtually nothing."
forget it.
that's fucking funny!
What makes the size of dark matter so important is that it will decide whether the universe continues to expand outward from the big bang, or eventually begins to shrink back to a singularity. Considering the universe started as a singularity, having it end that way may be indicative of another universe after this one. If everything continues to spread out, entropy will come out the clear winner.
Okay, I just read the article, and I'm down with it. There is nothing illogical about it, assuming their methods actually work, and I have no evidence that they don't. But, after re-reading the section on the "Creation of normal matter", I have one complex question that I hope can spark a bit of discussion: And how on earth (pun intended) did we get here from all of that?
All the "normal stuff" is thought to have been made in two steps, one occurring when the universe was roughly three minutes old, and the other some 300,000 years later.
:0)
See? Even "God" needs to get it in production, then issue a revision some time later before it's really running right.
(P.S.- My first thought was of "Dork Matter", but then I saw the StarWars DVD ad on the page. *sigh* Too easy...)
Soko
"Depression is merely anger without enthusiasm." - Anonymous
We can now measure stuff we cannot see, nor use, and has no real purpose other then keeping our planets apart and giving us something to theorize?
Astronomers Celebrate Reliable Measure of Dark Matter
By Heather Sparks
Scientists are closer than ever to balancing the checkbook of cosmic matter. This is because two recent independent measurements of normal matter in the universe are in agreement. The results further strengthen the case for the Big Bang theory and for the nature of the universe as astronomers understand it today.
The universe contains normal atomic matter, what makes you, your dog, the stars, and everything in between. Normal matter is what Carl Sagan was talking about when he said we are all star-stuff.
But in addition to star-stuff, there is invisible dark matter that is known only because the universe is denser than normal matter alone, as evidenced by how structures, like clusters of galaxies, are bound together by gravity. Even individual galaxies don't have enough normal matter in them -- that which can be directly detected -- to keep them from simply flying apart.
Now, through different measurements of conditions existing at the very start of time, astronomers are beginning to see the light.
"There is more than one way of measuring the total amount of matter in the universe," said astronomer Brian Fields from the Center for Theoretical Astrophysics at the University of Illinois, Urbana-Champaign. "And if you have an idea of how much normal stuff there is to all the universe, then you know how much other stuff there is, too."
Creation of normal matter
All the "normal stuff" is thought to have been made in two steps, one occurring when the universe was roughly three minutes old, and the other some 300,000 years later.
According to the leading theory, an enormous nuclear explosion called the Big Bang happened 13 billion to 15 billion years ago. From it, the universe appeared in an instant, but as a billion-degree mess of neutrons, protons and electrons. The explosion was so energetic that nothing could come together close enough, for long enough, to form atoms. But the universe expanded and cooled so rapidly that within three minutes protons and neutrons bonded in twos and fours, and formed all the atomic nuclei in the universe. This Big Bang Nucleosynthesis determined how much normal matter would ever exist.
Just how much matter that was can be estimated from observing the most recently formed stars and galaxies, because they are fueled by the hydrogen atoms formed from those original nuclei of twos.
Fields explained that young stars, like our Sun, are just now fusing that original hydrogen into helium whereas older stars fuse helium into oxygen and iron. Because the hydrogen fuel has not been converted, scientists are able to measure the proportion of original normal matter to dark matter.
"Stars change the amount of hydrogen and helium in the universe," he said, "and we want to know what the Big Bang did. So we have to find places where pollution from stars is minimal" to estimate the original amounts of normal and dark matter.
But before any stars could form, hydrogen atoms had to exist. This took 300,000 years after the Big Bang Nucleosynthesis the universe had to cool down enough so that electrons could bind with the nuclei.
Once this happened, there was a curious side effect: the creation of light in the Universe. Unbound electrons scattered the UV radiation from the Big Bang, but once the electrons were bound, the radiation was allowed uniform movement, thus, light was finally released in the young cosmos.
This light has existed since then, travelling along the edge of the universe, stretching and weakening into a still measurable microwave radiation, called the Cosmic Microwave Background, or CMB as astronomers call it.
Weak attraction
At the time of the original release of light, dark matter had congregated in clumps, which created small fields of gravity that eventually pulled in normal matter as well. Images of the CMB are therefore mostly smooth, but have spots, or wiggles, of slight variation, a result of the dark and normal matter pooling together.
"The nature of these 'wiggles' is basically saying how the normal matter was responding to that crazy dark matter," explained Fields, "by amplifying the places where the extra density was."
The CMB, most recently measured by highly sensitive probes in Antarctica, therefore gives a detailed measure of the proportion of normal to dark matter.
Phenomenally, both the measurements of young galaxies and of the cosmic microwave background showed that normal matter makes up just one-tenth of the universe. The rest must be dark matter, researchers say. Fields, who wrote about this astronomical agreement in the Oct. 19 issue of the journal Science, explained why this is causing astronomers to "bring out the bubbly."
"It didn't have to be true," Fields explained, "because they're completely independent things. It's just gorgeous that they agree with each other."
Earlier studies had showed that dark matter made up anywhere from 85 to 95 percent of the universe. Only now do the two different measures of dark matter agree. Now, 90 percent of everything is known to be virtually nothing.
"If he thinks he can hide and run from the United States and our allies, he's sorely mistaken." Bush on bin Laden
So apparently they think that the part of the universe we can't see is dark matter or something? And they seem to be able to guess how much of it there is. I believe that the universe has always existed, and will continue to exist forever. It is also infinitely large in every direction. The only reason we can't see the rest is because the light hasn't gotten here.
When you shine a flashlight at a wall you can see that light spreads out as you move farther away. The stars are so far away that the light does not reach the little tiny tiny earth.
Even better. Maybe the universe wasn't always here, and it had a "creation" date. We think the universe is "expanding". Maybe it's because that light from that far away takes a certain amount of time to get here. So light from farther away places is arriving here for the first time ever. if we can figure out how many light years the farthest away thing we can see is, then we can figure out how old the universe is.
I still think it's amazing that when you look at the stars in the sky that you are looking billions of years into the past. Those stars you see where there before dinosaurs were here, and they might not even be up there anymore.
The GeekNights podcast is going strong. Listen!
There is no dark matter of the universe.
It's all dark.
-nb
I'm only in high school physics, maybe someone more familiar with the field could provide an explanation and how it relates to the facts presented in this article?
Is your company running tools written by ma
Gack. How do they figure an explosion of spacetime is nuclear? There were no nuclei to fuse or split. My cynicism is telling me that the author just though "nuclear" sounded big and bang-y.
This has bothered me since I took a basic cosmology class a few years ago. If modern astrophysics says that the universe should have 900% more matter than we can actually observe, shouldn't that cause us to majorly reevaluate the equations that give us our expected mass?
"But in addition to star-stuff, there is invisible
dark matter that is known only because the universe is denser than normal matter alone, as evidenced by how structures, like clusters of galaxies, are bound together by gravity. Even individual galaxies don't have enough normal matter in them -- that which can be directly detected -- to keep them from simply flying apart."
that sounds pretty bible-like to me...
If 10 percent of all matter in the universe is made of "stardust" and the other 90 percent of the matter is made up of dark matter, we've got a pretty serious problem. There may yet be some other sort of matter out there that we don't know about yet, since the 10% of all regular matter occupies only a tiny fraction of the actual space available and dark matter is ,by the accounts in the article, clumped together into pockets. So what about all the rest of that space? Is is occupied by purple matter?
For instance, say that the universe does go on forever. The concept of infinite space is easy enough to grasp, I think, but wouldn't that mean that there is a point somewhere were matter just doesn't reach? I mean, is matter infinite too? How cuold that be possible? Unless, of course, space is directly proportional to matter in the same incomprehensible manner - space is infinite just as matter is infinite, and neither can be explained by our extremely limited scope.
4th actually ;-)
The results further strengthen the case for the Big Bang theory and for the nature of the universe as astronomers understand it today.
Astronomers *don't* understand the nature of the universe -- they're just guessing and in most cases are the first to admit it. That's why the Big Bang theory is just that -- a theory. It's not as if astronomers know with 100% certainty that the Big Bang occured and they're just ironing out the details, contrary to what you may have been told in high school. There are a *lot* of theories about the creation of the universe out there (including the "it's always been here, it'll always be here" theory) -- the Big Bang theory is just the most popular (despite the obvious glaring holes -- such as "why did it happen in the first place?")
Slant-Six
april's fool?
Still, it's all very confusing. I don't think it's a "serious problem", because the assumption seems to me to be that much of the dark matter has not materialized into what we recognize as matter yet. This means that the universe is young yet... When we reach the point when normal matter and dark matter are split 50/50, then my guess is that the universe will begin to shrink back toward its state before the big bang, only to explode all over again. Of course our planet will be long gone by that time (but that doesn't mean we have to go with it)... "In the beginning, there was nothing. Then it exploded."
Sanders : Kapteyn Astronomical Institute
Finzi : Dunno
Bekenstein : Weizmann Institute, IL
Milgrom : visiting Cambridge/Oxford/England
Mode (3) smart-aleck mode. Press * to return to main menu.
Of course, it had to fuse into all those other tiny particles that make up the protons and neutrons first, but why would they want to bore us by explaining all of that too? My question in relation to that: How small was this "stuff" before the explosion? Would it be fair to wonder if it had been rapidly exploding outward from a much smaller size than we could possibly imagine for much longer than we think?
It's blazingly easy to keep from getting tracked - don't post. (Or read..)
Indie rock lives! b-side!
Oh yeah, Bekenstein is of the Hawking-Bekenstein Fame. He is the guy who suggested the Entropy/Area correspondance. So I think he's smarter than Hawking (who set out to prove it wrong but ended up proving it right).
Modified Dynamics that you talked about have no covariant formulation (i.e. the theories are all coordinate-system dependent, which is bad since physics should not care about coordinates).
(I spent a year looking around for a covariant formulation...with no success of course.)
Mode (3) smart-aleck mode. Press * to return to main menu.
Beautiful work sir. Keep it up!
Scientists can measure ALL the dark matter in the universe, but can't build a fortune-telling weight machine that can get my weight right.
Pfft.
-Kasreyn
Kasreyn: Cheerfully playing the part of Devil's Advocate to hairtrigger
Only further testing will be able to prove that this match is not simply coincidence. They're right, this doesn't "have to be the answer", so let's not jump to conclusions from two friendly tests. (But certainly get excited for the potential! Heh.)
You can have whatever creationist theories you like, but you can't contradict what we *know*.
That's a very humbling thought. Not enough of humanity gets put in their place by the sight of millions of stars anymore. Gives me hope.
Dark matter is the packing material the Universe came in...
No theory of everything could ever be complete without allowing for this.
Creating protons isn't really nuclear as it's usually thought of. And the formation of atoms didn't occur for quite some time after the Big Bang. In any event, the term 'nuclear' completely fails to encompass the nature of the Big Bang, since 'nuclear' has nothing to do with the creation of spacetime.
I sure hope you're Ross Tessien, who posted this article to Usenet!
==braces for karma hit==
My theory, after watching Stephen Hawking's A Brief History of Time, and based on an extremely limited understanding of all this crap, is that time is circular rather than linear as we commonly depict it. At a certain point in that circle or loop or whatever. is the Big Bang. After the Big Bang, the universe expands until it runs out of steam, then it slowly starts to contract again, bringing all the matter and anti-matter together where they annhilate each other and turn into energy, which is compressed further and further into an itty-bitty little space, then BOOM, it starts all over again. So basically, in nerdspeak, I think the universe/time is an endless loop.
But, you know, I could be wrong. It has happened once or twice...
an enormous nuclear explosion called the Big Bang happened 13 billion to 15 billion years ago. From it, the universe appeared in an instant, but as a billion-degree mess of neutrons, protons and electrons.
If ever Big Bang there was, it was not a giant nuclear explosion! Damn at those temperatures there are no nucleus (as they themselves state a few sentences afterwards). It is rather a very FAT release of energy, which later congregated into quarks and antiquarks, neutrinos, etc. definitly not nuclear. And what a hell is "dark matter". They state that "dark matter" congregated and formed gravity pools...
At the time of the original release of light, dark matter had congregated in clumps, which created small fields of gravity that eventually pulled in normal matter as well.
Dark matter does not emit radiation by definition. It thus has to have enough gravitational pull to keep all EM radiation in. That is a freakin big chunk of matter, not small gravity fields! And what do they mean normal and not normal matter... it's all the same stuff, energy. The energy is just "stored" differently.
"The nature of these 'wiggles' is basically saying how the normal matter was responding to that crazy dark matter," explained Fields, "by amplifying the places where the extra density was."
Errhhmmm... that is called matter falling in the black hole to make it larger and thus increase the gravity....
Imperium et libertas
Autocracy and freedom
..sabers in a scientific site? This is just another perversion from the dumbed down culture we're in. Well anyway back to the topic, I was wondering what kind of a gravitational effect light has on the universe. As we all know, there are ALOT more photons in the universe than any other (non virtual) particle. Perhaps if light, or rather the energy contained in the photons, had a gravitational effect then it may plug up the discrepancy that dark matter is supposed to explain. Just my 6.02*10^23 cents.
This slashdot comment also looks like this Usenet post.
This slashdot comment also looks like this Usenet post.
How about I speculate; we discover that dark matter exists, and that it outnumbers regular matter 9:1
Knowing it exists, we can start trying to find, create, and control it.
N years later we have dark constructs.
Without even having the theories about the universe showing there is dark matter, we don't find it or about it's properties, capabilities, and uses.
GPL Deconstructed
You mean they've finally measured all the matter that's inside CowboyNeal's belly?
Now if they could just record its evil laugh...
Democracy. Whiskey. Sexy. Pick any two.
I believe I've got some under my couch. A rather more important discovery will be, I suspect, that all that dark matter is all the socks of every culture ever to evolve clothes dryer technology. Clothes dryers create minature wormholes which teleport your socks to random points in the universe. This revelation will ultimately lead to a faster than light drive with a clothes dryer at its core. Its mission will not be to explore new planets yadda yadda. Its mission will be to retrieve all those socks.
I'm trying to teach myself to set people on fire with my mind... Is it hot in here?
They look at the galaxies, and estimate how many stars and stuff there is in the galaxy. Any rotating galaxy. And They figure out how fast the galaxy is rotating.
They notice a problem. For any rotating galaxy there is not enough star stuff to hold the galaxy together. The spiral arms should never be there.
The star stuff in the galaxies do not have have enough gravity to hold galaxies together. Galaxcies should not exist at all. Stars should be all flying about because that is how weak the gravity is.
Just how much too weak? The Star stuff has one tenth the gravity needed to do the job. so something has to be doing the other 90%.
That is what the dark matter is. It is a term to label what the other 90% is. The don't know what it is yet. but they are working on it.
"It is a greater offense to steal men's labor, than their clothes"
What caused the big bang? How was it initiated? What were the bounds of the "universe" as it were before the big bang?
While it hasn't quite graduated to being "accepted wisdom" yet, an increasing number of those who look at such questions are persuaded by the idea that a big bang can occur when a black hole collapses, with the rebound from the (almost) singularity creating a new space-time manifold shifted slightly away from the space-time manifold which produced that black hole.
One site I found has more extensive discussion of this scenario.
how on earth (pun intended) did we get here from all of that?
It seems like you might actually need the physice of our cosmos to be tuned to the production of carbon, oxygen, etc. by nucleosythesis of the original hydrogen and helium for the black hole-big bang production cycle to work, so the earth and indeed us are just incidental byproducts of these cosmic requirements.
"Why?" doesn't always have an answer.
-- Our systemic servants do not good masters make.
I call blatant matterism!
It's not dark matter you unenlightened cretins!
It's matter of color!
Heathens.
Hilary Rosen's speech was about her love of money and her desire to roll around naked in a pile of money.
You can have whatever creationist theories you like, but you can't contradict what we *know*.
I am a creationist but I agree with everything that science has proven. It still hasn't disproven, God.
One guess out of million is that God slapped his hands together and between the palms of his hands was all the matter of the universe. When he pulled his hands apart he alowed the big bang to happen. And thus our Universe was born.
With that I can be a creationist and still believe everything that I have learned to be *true*.
Yes and I also agree with you that not enough humanity is put in their place by the sight of millions of stars.
Something very odd just happened...
I clicked the link to space.com to read the article. When the page loaded, the big central advertisement was for "Star Wars: Phantom Menace" videos... Kinda threw me off for a moment. Perhaps I haven't recovered yet beause I'm posting this here. hmmm
Skiers and Riders -- http://www.snowjournal.com
If bright matter truly makes 10% of the universe, then by definition the remaining 90% of the universe must be dark matter.
The reason is that neither the terms "bright matter" nor "dark matter" specify a single type of matter. Rather, they define two values of a single common characteristic of all matter. The characteristic in question is how the matter interacts with photons. If you shine a light on something and you can see it, then it's bright matter. If you heat something up and you can see it, then it's bright matter. If you energize something then let its energy level drop and you can see it, then it's bright matter. Otherwise it's dark matter.
Therefore we can't measure dark matter directly merely because we can't see it. All astronomical observations depend on photons. Radio. Light. X-Ray. Gamma. Just different frequencies of photons. Since dark matter neither reflects nor emits photons, astrophysicists can't observe it. Or perhaps it does emit photons, but then immediately reabsorbs them (as in the case of black holes). Either mechanism comes down to the same thing. They can observe its effects indirectly by watching, for instance, the effect that its gravity has on surrounding bright matter, but no direct observation is even theoretically possible.
But there really aren't any theories about the nature of dark matter, because it's fundamentally impossible to observe remotely. Maybe it's some truly strange substance. Maybe its just a whole bunch of black holes. No one knows. The only reason that we know about black holes is that some brilliant physicist who'd been downing a few too many beers one night did a thought experiment about the implications of gravity's inverse square strength. So we had a theoretical phenomenon that astrophysicists could later go and look for. But that's not true of other forms of dark matter.
All that's important is that "dark" matter is every piece of matter that isn't "bright" matter. It's still matter, and will still behave exactly the same as bright matter behaves. But it may come to be discovered that some characteristic that we thought was endemic to all matter is, in fact, only endemic to bright matter. We have no comparison yet, so we can't make that determination.
I don't think that anyone believes that all dark matter is in the form of black holes. Who knows, maybe so. I'm certainly not an astrophysicist (though I know a number of them who are on the bleeding edge), so someone can easily have come up with some theories about all this of which I'm unaware.
But this is my current understanding, and with the rate that astrophysics moves, I'm probably at least 5 years out of date.
Oh, explaining this caused me to remember a theory about dark matter that I heard from my undergraduate adviser back in my college days (Dr. Douglas Lin: he was and is a big shot in the astrophysics circles). The idea is that there actually isn't any special dark matter. It's all bright matter. But some matter might be in locations where so few photons fall on them that we just never get a chance to observe that matter. For instance, it's known that all the galaxies of the universe exist on the surfaces of voids in the universe (that observation is what gave rise to superstring theory). Think of soap suds. We've got complex surfaces, where all the soap is, each surrounding a small void with no soap. Small from our perspective, but from the point of view of a technological civilization living in one of the "galaxies" within the soap film, those voids are huge. The universe has the same structure. And these voids are just monstrously huge. In the center of one of these voids, there would be very little light, because all the light sources are very far away. So you could stick a whole lot of matter there and no one would ever see it. These voids are so huge that you could easily fit 90% of the universe's mass in them and still have a very low density of matter. It's normal "bright" matter, but insufficient light reaches it for us to observe it. The problem with the theory is that if you have 90% of the universe stuck in these voids, then the voids should collapse from gravity and make the galaxy distribution homogenous. And we don't see that. Perhaps this problem has been resolved by now. I don't know. And, of course, there are other locations where matter can be hidden, where we wouldn't be able to observe it. Those voids are just a single example.
-- Nolite audere delere orbiculum rigidum meum.
This just goes to prove Sturgeon's law:
Ninety percent of everything is crap.
Could this have something to do with the discrepancy in the position of the Pioneer spacecraft? There was a story on CNN in May about them.
It's not very technical since it's "mass media" but the essence of the story is quite clear:
"Something is slowing down the spacecraft. And we have not been successful
in finding the source of that. There is more slowing than you would expect
from Newtonian gravity," said John Anderson, a senior scientist at NASA's
Jet Propulsion Laboratory in Pasadena, California.
This idea about gravity being slightly stronger as distance increases might be a good thing to try to research in regard to this 'mystery' of the Pioneer spacecraft.
We can't detect it. That's the key. An advanced civilization has perfected Dyson Spheres , and is enclosing the stars to capture the energy. They are able to capture every possible piece of energy, so that we detect nothing.
I suppose that's a side effect of perfecting your energy capture -- it's undetectable. We're in a race. A race to enclose the universe; whoever get the most energy wins.
Seriously, I think about these things. ;-)
I feel fantastic, and I'm still alive.
It is generally accepted that the Big Bang created almost exactly equal amounts of matter and antimatter... it is only the chance that slightly more matter than anti-matter was created that lets us all sit here and ponder about it. So in a way what they are saying is true, but it's a stupid way of saying it; it's a matter of meaning, not fact. It makes you go "ooh" but it tells you nothing.
Imagine if they had said "The creation of the Universe did not determine how much matter would be in the Universe" (i.e. the opposite of what they said). It wouldn't make any sense!
And as other people have mentioned, they rave on about a 'nuclear' explosion... and they say the first step in the Universe took three minutes? Have they never heard of Planck Time?
Now, 90 percent of everything is known to be virtually nothing.
Ha, what a wonderful way to end an essay. Gosh, I wonder if they were appealing to science or sensationalism there? I sure can't tell.
Suddenly space.com is not a reliable resource for me.
Security through promiscuity is no better than security through obscurity.
1) Get Jon Katz to write a book full of book reviews and post a topic about it on Slashdot.
2) The amount of trolls accumulating around that single topic on Slashdot will be so intense that it creates a giant gravity field that sucks everything in the universe together.
3) The universe is saved from flickering out into nothingness due to endlesss expansion! No dark matter required, yay!
Men believe what they want. - Caesar
I'd say, given the diet the Al-Qaeda seems to be giving him, that would be 98 pounds added to the universe, give or take.
Well spotted, dude. And from 1996 too!
For many Slashdotters, Kantor's central idea of basing physics on information, rather than things like matter and energy, might seem inherently appealing.
We have three methods to calculate the mass of the universe. Two are based on electromagnetic interactions. Those two agree. The other is based on observations of gravitational interactions. It gives a result 10X as large for the total amount of matter. Therefore 90% of the universe is made of particles that interact gravitationally but not electromagnetically. The only way to observe them is to observe their gravitational effects. Like, duh. Why is this such a difficult concept to grasp? It's an empirical observation.
Keep in mind that if something only couples gravitationally, it's going to be extremely hard to see. You're prejudiced by your own experience with the world, which is mostly based on electromagnetism- meaning interactions with photons (real and virtual). Get rid of electrodynamics, and most concepts and phenomena you're familiar with- atomic physics, chemistry, biology, optics, materials science, friction, pressure, radiation, viscosity, resistance, reflection, transparency, iridescence, impenetrability- all this stuff goes out the window! Your ass would sink through your chair, right through the ground, until you reached the center of the earth with everything else. Don't underestimate the importance of photon-mediated interactions. Everything else is gravitation, beta decay, and the strong nuclear force. Of those three, only gravitation operates over non-microscopic distances. And it is very weak. There could be up to several tons of dark matter in the room with you right now. You would never know it's there.
Of course, the mass could be ordinary matter that we're just not seeing. Many people like the idea of lots of Jupiter-sized objects. Lots of black holes might also work (although a black hole can feed off either kind of matter).
Nah, that would get out of hand...
I like that
In the latest Scientific American (which is unfortunately becoming a clone of Discover or Omni these days) there was an article about membranes floating around in higher dimensional space. Two of these membranes happened to collide, and that was the big bang. It impressed me as being total off-the-cuff speculation, though.
Universe.
Alot of this big bang cosmological constant mumbo jumbo requires ALOT of faith. There is just too much complexity(even in our own bodies, gender differences as well, etc etc) for this to be random happenings leading to 'evolution'.
I'm waiting for proof please.
lilmacumd@yahoo.com
exist
Thermodynamics.
No machine (even a dyson sphere) can possibly capture all the energy.
Remember the laws of thermodynamics: You can't win, you can't break even, you can't even quit the game.
-- Nolite audere delere orbiculum rigidum meum.
I am a creationist but I agree with everything that science has proven
science has proven nothing.
You don't need to disprove god, just open your eyes.
Also, does anyone know where Sanders, Finzi, Milgrom, and/or Bekenstein are working today, I would like to get in contact with them regarding their models. Locations and or email addresses would be great.
Milgrom - the Weizmann Institute of Science, Rehovoth, Israel. Bekenstein - the Hebrew University, Jerusalem, Israel. Professional publications such as The Astrophysical Journal should list their email addresses in the headers of their papers, and most if not all are online. Last time I checked ApJ had a 100+ years [sic!] worth of issues online, so you can update yourself on the post-Newtonian developments yourself.
How do they figure an explosion of spacetime is nuclear? There were no nuclei to fuse or split.
Of course there were. For most of the famous "first three minutes" the matter consisted of electrons and protons (hydrogen nuclei), too hot to maintain compound nuclei or neutral matter. The hydrogen nuclei fused into heavier ones, such as deuterium, tritium, helium, some Li. Up until now most of the (ordinary) matter in the Universe is hydrogen, the rest of the elements are much less abundant.
The heavier stuff (O,N,C, what astronomers call "metals" and what constitute the basis of our life) formed much later in stellar interiors, but that's another story.
The first three minutes were not unlike a hydrogen bomb at all.
...Which would be obvious to even the most dimwitted individual- who holds an advanced degree in hyperbolic topology, mmm,glaven.
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Send lawyers, guns, and money!
[sarcasm]You're quite right. Zeus created the universe.[/sarcasm]
Seriously, just because the big bang theory is a bit lacking is no reason to go believing in some god. And there's REALLY no reason to think that tha christian/jewish/muslim god is the correct god to beleive in. My money's on Thong, God of Pants.
If the universe is an evenly distributed thin soup of cold dark mass, would it not then be in a state similiar to the one that precipitated the Big Bang? What I mean is, if the universe was an evenly distributed pinpoint-sized ball of hot mass (relative to it's "surroundings")that "exploded", then wouldn't the massivly-large ball of cold mass not be the same thing at a larger scale/perspective?
No, because space and time were also created at the instant of the Big Bang and in the event of an open Universe we already have these things, plus an energy density quite ridiculously low - one electron/positron pair for every trillion cubic light years is not enough to make any kind of explosion!
Unless superstring theory comes up with some better explaination of what happened before the Big Bang (which I believe it explains as the decoupling of our 4-dimensional macrospace from the other 6 dimensions that are curled up real small), then something like Linde's chaotic inflation seems to be the best bet - an unstable "false" vacuum within which quantum fluctuations can cause a Big Bang-like event at any time...
I must agree with that, it is the only logical thing.....
Alternatively we should expect a new universe to be created in Afganistan next month?
What happens when black holes get hold of other black holes? Does the bigger suck in the smaller? Do they combine into a super black hole? Are they the force behind my theory that the universe will recompress itself for another bang?
You get stuff like this when someone spends most of their adult life studying a theory they believe to be true. Then they find out that it doesn't add up, so they set out to find facts that support their theory instead of using facts to guide them to the proper conclusion. In other words, they already know in their mind what the outcome of the experiment is going to be. If it doesn't come out that way they, they ignore it or attack its conclusions.
...wasn't it discovered that the expansion of the universe is actually accelerating?
We don't know enough to even theorize what is going to happen. If the expansion is actually accelerating, there are other factors at work that we don't understand in the faintest.
My question about this theory would be:
If this was before the universe was created, what was He/She sitting on?
Ha!
When I were your age, all round here were fields...
A troll is worth a thousand words :-)
Big Bang nucleosynthesis determines the amount of baryonic ("normal") matter because it allows us to predict the primordial abundances of light elements as a function of that amount, most dramatically the He/H ratio, which is known from observation and inference to have been about 1:3.
It works like this: early in the Big Bang, everything was so hot that quarks were essentially free, forming a big, hot slurry called a quark-gluon plasma. As the primordial fireball expanded and cooled, protons and neutrons condensed out of the quark-gluon plasma like drops of mist forming in wet, cooling air.
The temperature of the universe at this time was still very high, which means the average energy of these protons and neutrons was much higher than the binding energy of light nuclei, so no sooner would a proton and neutron bind to form a deuterium nucleus than they would get knocked apart by another particle wacking into them.
The universe cooled further, and eventually reached a temperature where the average particle energy was low enough that light nuclei could form and not get disrupted. Originally, roughly equal numbers of neutrons and protons were formed, but free neutrons decay with a lifetime of about 15 minutes, so by the time the universe cooled enough for neutrons to bind permanently, there were a lot fewer of them.
The fraction of neutrons and the total density of neutrons and protons at the time the universe reached this temperature determines the amount of helium in the early universe, which we can measure by correcting for the subsequent production of helium in stars. Thus, we can determine the density of the universe when the light nuclei were being formed. We also know the radius of the universe at that time by various chains of inference. Knowing the radius and the density gives us the mass: that is, the total amount of normal matter.
The details of Big Bang nucleosythesis are one of the great triumphs of 20th century physics, for which Fowler got the Nobel Prize back in the '60's. There have been anomalies detected (lithium is particularly difficult to deal with) but the theory has so far stood up to a lot of critical examination.
Dark matter (or modified gravitational potentials, which I find kind of appealing) get invoked as explanations for anomalies in galactic dynamics precisely because Big Bang nucleosynthesis stands on such solid foundations.
--Tom
Blasphemy is a human right. Blasphemophobia kills.
How about this. What if everything is preordained, but because of its complexity our minds cannot possibly, no matter the scope of our computing and math, understand it all. Therefore, because it is defined but unknowable (i.e., just like quantum mechanics, that electron certainly is somewhere, but we are not able to know where it is by a law of nature) we can ACT like we have free will.
I think there is some kind of interaction between knowing the truth and the truth being true. So, okay, your entire fate is preordained, but you cannot get at that info, therefore, why live your life like you have no free will? The absence of the knowledge yields effects similar to true free will. Effects similar enough that you can get on with life.
Maybe. IMHO.
I'm not saying this moderation is not fair; the comment IS offtopic (but has a good point, though), but when moderating comments offtopic, please consider their context first.
When scientis finally decide what light is, waves or photons, they will realize that it is neither.
Everybody already knows that photons (and leptons, hadrons, etc.) are neither particles nor waves. They're entities that exhibit characteristics of both. Particles and waves are only the closest analogues we have from ordinary everyday experience.
When you live anywhere near the city, the most you can see is oh, about three stars. It's very difficult to be humbled by that. In fact, i pretty much forgot all about stars, space, and how small earth really is. Then, about a year ago, i took a trip to maui, and we went up mount haleakala (sp?), to see the sunrise. The sunrise is really hyped, but all i can remember about that morning are my freezing feet and looking up to see the ISS moving across the background of all those stars. It had been so long since i had seen anything like that. It's too bad that people cant see those sights on a regular basis. Our cities have enabled us to fulfill our self-serving philosophies.
"To save the planet, I had to go to the worst spot on Earth, and that was Philadelphia." -- Sun Ra
Layman as I am, something I sometimes wonder when reading about this stuff is, does "vacuum energy density", which is supposedly very high, equate to mass through matter-energy equivalence, and hence cause gravitational warping of spacetime? Haven't seen the idea proposed anywhere, which is probably because it's totally stupid, but can someone enlighten me why? :)
Don't underestimate the importance of photon-mediated interactions.
This is the sig I've been waiting for!
Did I miss something, or does everyone seem to assume that gravity is the only force by which heavenly bodies may interact?
What happened to eletrical charges? Can't those hold things together or repulse them apart?
Well that's a really interesting idea. But I think it's pretty easily testable. Is all of the gravity that we experience here on Earth's surface accounted for by the known "bright" matter that comprises the earth?
That that is is that that that that is not is not.
So, what is outside the balloon? Anti-space?