Do we know what generates neutrinos? Does our sun generate them, I guess?
Also, do you know how we detect them, since they only interact with the weak and gravity forces? I have read a bit about the underground neutrino detector that basically blew up in Japan, and it sounded like they were somehow getting photon readings from passing neutrinos--but if they are truly WIMPs, how is that possible?
I think recent observations indicate that the expansion rate of the universe has been accelerating. This article talks about it. And as the expansion continues, matter gets farther apart, which weakens the gravitational attraction, which means a big crunch is unlikely give currently observable forces.
I am not a particle theoriest, but WIMPs supposedly interact via gravity. They expereince gravitational attraction (which is why they are theorized to explain the missing mass in galaxies) so they should be able to clump together. They don't interact with the EM force, so they don't shed/reflect/interactinanywaywith light. Supposedly.
I am not surprised you haven't heard of an actual study that WIMPs can form large chunks of matter, since WIMPs are still purely theoretical as far as I know. No one has ever detected one, have they? Neutrinos interact with the weak and gravitational force, but they have no mass. . . maybe they are WIMPs? Again, IANAPT.
Re:Um, if it's a star it can't be dark matter....
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"Dark Matter" Observed
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Actually, most MACHOs are thought to be failed stars--white and brown dwarfs and the like. I disagree that this object they found is in the "known" column as far as frequency of occurrence. This article supports me (found on a quick search), as well as many other things I have read. It is not well known how many failed stars populate the universe or even our own galaxy, or even how many white/brown dwarfs may populate the Kuiper Belt and Ort Cloud of our own solar system. This isn't known becuase the objects themselves are very hard to detect, because they don't emit much EM.
I hear what you're saying, I too have thought, "Why the hell are they coming up with WIMPs that we have never observed to explain the fact that we just can't see all the necessary matter? Maybe we just haven't seen it because the universe is a dark place." But some particle theories (e.g., supersymmetry) allow (or even require) that particles like WIMPs exist, and if they do, they are a perfect candidate for dark matter.
But I disagree that they need to change their method of inquiry. This very article shows that, given a bit of evidence, cosmologists are very willing to accept the mundane explanation. And this article also points out that they are in fact pursuing the evidence to support the mundane theories.
You portray the scientists as "assuming" many things but I don't see it. The fact that they come up with wild theories does not mean that they are ignoring the obvious. It's jus that, in the absence of evidence, either the mundane or the exotic explanation could be correct. So they don't throw either theory out. I don't see them "making 'conjectural' observations...that is, assuming that an unobservable activity has been proven simply because something observable has occurred." This article certainly does not imply that, quite the opposite in my opinion.
My current understanding is that dark matter is just normal matter that doesn't emit light. For reference, all matter does 'suck in' light (meaning the energy is absorbed, usually given off as heat).
WIMPs (weakly interacting massive particles) are theorized not to interact with the EM field--no photon coupling--so they (theoretically) do not suck light, or reflect it, or interact with it in any way. This is one of the other candidates for dark matter, the more exotic candidate. What this article shows is that they have found "normal" matter that can account for he apparent gravity in galaxies, "normal" meaning regular old EM interacting matter that we can see if only we shine light on it. MACHOs are such normal matter, which we can't see only because they don't emit or reflect enough EM radiation for us to detect, basically rocks in space.
Re:Um, if it's a star it can't be dark matter....
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"Dark Matter" Observed
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I think the term "dark matter" does not necessarily apply only to non-luminous matter. I think it is used to refer to any unobserved matter that can account for the apparent gravity we see in galaxies. MACHOs have been a candidate for dark matter for a while, because they are mostly failed stars that do not emit light (at least not enough for us to see), though they do interact with the EM field. Other candidates for dark matter are indeed non-luminous, even non EM interacting (WIMPS-weakly interacting massive particles--that only interact with the weak nuclear force and gravity, but not EM so they can't be "seen" using light).
I don't think the argument for dark matter has to do with the expansion/contraction of space-time (i.e., the universe). I think the argument for dark matter is based on gravitational models of galaxies and the idea that, according to current theory, most galaxies do not appear to have enough (visible) matter to create the gravitational force needed to hold that galaxy together.
The expansion of the universe appears to be accelerating. See one article on this here.
Quantum entanglement has been accomplished en masse, and recently (though I can't seem to find the reference right now--try physics news update for the past few months).
And I don't think they would need two different lasers emitting entangled beams. One laser could have its beam split, same as in normal holography.
I agree, work funded by public money should be public domain, but not necessarily in all cases. For one, they might not be funding it completely. NASA might only have put up some of the development cost, and the company maybe put up the rest. In such a case, I have no problem with the company patenting what they make.
If you could build a similar device, without looking at the details of the patented devices, you would probably not even infringe their patent. I would be willing to bet they can only get protection for the particular way they made their devices, and their technique would have to be "non-obvious" in order to get a patent. They couldn't patent a "flying robot" because such already exist or are obvious to build given current technology. Their protection is probably narrower. Of course it depends on the breadth of their patent protection, but if you built your own flying bug, you would probably not come up with the same bug they came up with (unless you looked at their patent...). If not, you would not infringe their patent.
Um, one point you missed--most of the recently passed laws limiting civil liberties have a 5 year life span built right in. How exactly does that fit into your "police state" theory?
I agree that most of the recent changes have potential for gross abuse. But, (and I realize I will get flamed here on/. for this, as well as modded into obscurity) there are mostly good reasons for the changes, at least temporarily. It is a balance of freedom versus security, and the pendulum has understandibly swung toward security recently. So we lost a little freedom for now. How has your life actually changed because of it? I daresay that few people (barring those of middle eastern descent--they are definitely feeling the effects of this) have been affected by the changes in the laws at all. And please don't forget the reason for all this--would you want a suitcase-sized dirty nuke detonated in your home city? It wouldn't be Hiroshima, but no one could live there for 1,000 years just the same. Before we bash the gubbament, maybe we should remember to weigh the loss of rights correctly against the increases in security brought about by these changes.
Maybe it is the Netherlands news that is skewed--I have read many US news accounts that show the volume of criticism for military tribunals. In fact, most news accounts on that subject speak of the intense criticism he is getting.
I agree that we have been getting a lot of patriotic news recently, but criticism of the "war on terror" is easily found in the US media. NPR recently had an article discussing the fact that there have been double the complaints filed by university professors for being reprimanded, etc. for expressing their view on what Bush is doing. In fact, the article said that it was mostly PRO WAR professors that had most often been punished for expressing their views.
Um, no. Constant velocity does not to be explained in Newtonian physics. It is just every bit as "natural" as being at rest. You might have an intuition or a bias that everything "should" have begun at rest and therefore the current state of non-rest must be explained. But that isn't implicit in Newtonian physics. The advance made by Newton was exactly the realization that changes in velocity required agents but that constant velocity does not.
Yes, duh. But since we are talking about the big bang model, and since this model posits that all these particles (i.e., all matter in our universe) are moving away from each other (NOT in the same direction) then you have either swallowed some pretty amazing initial conditions which you have twice implied need no explanation, or else there is a reason for the particular movement of all this matter. Your glib reference that space-time is just that way isn't very satisfying. I also don't think it is correct, with all due respect. You obviously know some physics.
A cosmological constant acts like a pressure density defined everywhere in space and keeps the metric expanding ever faster. But it doesn't exert a "force" in any standard usage of the word. We don't need a repulsive force to accelerate the expansion, because space itself is exapnding and carrying the matter along with it.
Ah, we agree, though not on terminology. You can refer to an added term (the C-constant) and deny that forces exist, but then you have to admit that the added term includes the effects of a force.
And again you say we don't need a "force" to explain the acceleration of expansion. I guess we don't as long as we are using a math model that does not refer to force explicity, though it includes the effects implicitly by another method. But I am not sure you understand this. You have repeatedly stated that no force is needed because space itself is expanding.
Now, let me be clear, I am not talking about mere expansion, but acceleration of the rate of expansion--a different thing by one time differential.
This definitely requires some kind of force to be acting. Particles don't change their velocity without a force (as you correctly pointed out). Neither does space-time. It sounds like you think we cannot inquire into why space-time behaves the way it does--it is just the metric, or the constant. But space-time depends on the matter therein, period. The two (space-time and mattter) are self-referential--they both affect each other, and matter EFFECTS space-time, i.e., brings it about. Space-time does not bring about matter. The only reason we have space-time is to describe how matter (and energy, to be technically correct) acts. If you take away the matter and energy, the idea of space-time is meaningless.
The reason space-time is expanding is, respectfully, not "because it is inherent in space-time" as you have twice stated (that is the original reason I posted--to disagree with this gross oversimplification). It is because the matter in our universe is moving. Move the matter, and your space-time geodesics, etc. change. If you have matter flying apart, away from other matter, then you have a space-time that looks like ours does, i.e., expanding. But to say that matter (and our universe) is expanding because the space-time metric looks the way it does is backward. That implies that the universe is governed by our model of the universe. The metric, the cosmological constant, these are just part of the model. You can't refer to them in order to explain, only to describe.
I'm sorry to repeat myself, but you are in error here. Even in an empty Universe, the Einstein equations lead to a spacetime metric that is either expanding or contracting. (I believe this solution is called a deSitter Universe.) It doesn't take matter at all, so it can't depend on the kinetic energy of matter.
The deSitter Universe is just a model of the universe with zero curvature--one in which there is *exactly* enough energy to keep the matter therein expanding forever (i.e., zero curvature).
I have never heard of a space-time model for a matterless space-time. I couldn't find it under deSitter. I would be very interested to read such, if you can provide a cite.
I agree that the expansion of the universe is not caused by some currently acting force, I believe you may have misunderstood my post on that point. But your statement seems to indicate you do not seek any initial cause for the state of the expansion--that it started expanding for no reason. Even a newtonian particle at constant velocity (to use your example) needs to somehow obtain that velocity. In the case of the matter in our universe, I always thought it was because of the initial energy density and radiative pressure from the big bang, giving an initial impetus to matter. Indeed, other authors seem to think this too, see here for example (just somethign I turned up on a quick search).
Finally, something that may have caused some confusion, I mentioned recent supernova observations and the idea that there *is* a force causing *acceleration* of expansion. What I posted is accurate, do a google search for quintessence or dark energy.
In response to your comments on my post, I think you are getting a bit nitpicky, and not technically accurate. You wrote:
The correct description is as the other poster says: space is expanding, though gravity is slowing down that expansion.
Space expands because matter is expanding or moving. The space-time and matter are not separable, you can't talk about a space-time metric existing without matter existing somewhere, because matter dictates the structure of the metric (as well as the metric dictating the movement of matter).
You also said:
No. The metric changes with time, but there are no forces involved in gravitational phenomena.
I think you are confusing the difference between models and reality. Both Newton and Einstein came up with models. Einstein replaced a gravitational potential (the source of a force) with a space-time metric. You can view the universe as one in which matter causes a gravitational force to be exerted or one in which matter causes the geodesics of space-time to be shaped differently, which causes matter to accelerate. They are one in the same. To say that "there is no force involved in gravitational phenomena" is merely a choice of models. It also totally misses my point.
My point was that if the metric is indeed changing with time, there has to be a reason behind it--the metric does not control the universe, it only models it. The metric changes locally near matter because the matter is there, not because it is "inherent in the metric" (unless you think the metric creates the universe, rather than the metric merely modeling the universe). Likewise, the metric changes with time because of other conditions, namely, the negative vacuum energy density (positive vacuum pressure). This is what caused the initial expansion of the universe--hot radiative pressure when so much matter and energy were confined to a "small" region (though size doesn't have much meaning since it was really the entire universe), creating a really high energy density.
I also wrote:That said, recent supernova observations actually did indicate that the expansion of the universe is *accelerating*, which means that there *is* a force causing expansion of the universe.
You replied:No, that's not true either. The geometry of space obeys field equations, and can change with time. No forces are involved. What you say would be true if gravity were described in Newtonian terms by a force, but general relativity does not describe any gravitational phenomena in terms of forces.
Gravity *is* described in Newtonian terms by a force. You seem to think that because one model (Einsteins) does not refer to the term "force" then force does not exist. The "force" in Einstein is buried in tensor equations, and how they determine the shape of geodesics, which determine how matter moves. But both models describe the same phenomena (though I agree relativity does it more accurately).
And finally, you write:Again, no. The matter in the universe flies apart because the intervening space expands.
Whatever, you desire to contradict literally everything I posted has gotten in the way of your understanding. Your statement indicates that you think space-time's expansion causes matter to move apart. This is exactly the opposite of what is happening. Space-time would not be doing what it is doing if there were no matter. Ultimately, space-time is used to describe the location and effect of matter (via gravity) on other matter. Matter determines the shape of space-time. Movement of matter causes the metric to change over time. I agre the two are self-referential, but without matter, the space-time would not exist. And anywhere you have matter, you will have space-time. Matter is the important quantity.
I see this as being a perfect example of the tragedy of the commons. Individuals who are threatened by major corporations fold rather than fight the battle that would prevent the corp from similarly threatening other individuals. The corp then goes on to threaten other individuals, who behave likewise. One, or a few, who stood up and fought would stop such behavior. Unfortunately, people prefer convenience to honor.
Ouch. How about instead, people aren't willing to sacrifice themselves for the good of the unappreciating masses? In each individual case, it is obviously best for that individual to do what they do (i.e., "fold" as you call it), or else they wouldn't do it. Granted, it might be better for everyone if everyone stood up and fought, but the first guy who does that gets his head blown off. It is therefore (to me) understandible for someone to duck.
The best way to get rid of the DMCA and a bunch of other BS that gets passed through congress is to pass one single law. The law would state: "Machine readable encodings are legaly equivalent to human readable text."
As a direct consequence the DMCA would be in violation of the 1st ammendment. Any patents on software would be voided because text to the best of my knowlage is only copywritable, not patentable. The headache of stupid digital legislation would hopefully be behind us.
I am not sure I understand your post. First, most software is copyrighted, not patented. And I also thought the DMCA was the Digital Millennium Copyright Act. DOesn't deal with patents.
Why would the DMCA be in violation of the First Amendment if machine readable code were considered human readable text?
"Of course, it is a flaw in our government that the legislature creates the laws, and the courts interpret them, "_____
A flaw? I think separation of powers is one of the main strengths of our government. Imagine if the same set of people were in charge of creating *and* interpreting the laws. Goodbye constitutional protection. Every law would be constitutional, no matter what it said.
One distinction for your example: Razor blades have legitimate, non-terrorist uses. Hacking software (or whatever it was exactly) is *designed* to do something "illegal." Are there other legitimate purposes to what Felton did besides violate copyright? Maybe so, but it sounds like it was designed to be "misused."
_____"The problem here is that it's perfectly legal for large corporations to strong-arm the little guy with threatening letters, and subsequently fail to follow through with the threat. "_____
This is true. You can't get into trouble for threatening to sue someone. You sound like this is a bad thing. While I think bullying with threatened lawsuits is a bad thing, I have two points to make.
First, the lawyer who wrote that threatening letter could, if he misrepresented his client's legal position (or anything else in the letter) be subject to sanctions. It isn't technically "illegal", but a lawyer cannot lie about things like thatunder most states' ethics rules. If the lawyer could not make a straight face argument that he had a viable suit, then he can't threaten someone that he has a viable suit. (Note a caveat here--making a straight face argument is very easy to do, so this isn't much of a hurdle.)
Second, think of what would have to happen to prevent a corporate entity from sending threatening letters like this. What exactly was the plaintiff asking the judge to do? I don't know, I only read the excellent summary of the hearing, but I do think that any remedy against the corporation would be onerous under those facts. To say that they did something actionable could mean that anyone who sends a letter claiming a legal right (and threatening to sue) will be forced to follow through. That would apply not only to the corporation, but also to me and you when we write to Orbitz saying, "You breached our contract for the ticket I purchased...." Orbitz can tell us we are wrong, then sue us if we don't sue them because we "threatened" them. That is essentially what it sounds like the plaintiff was asking for: punish them for threatening to enforce what they think are their legal rights against me.
Again, I have not read the papers. IIAL.
"Actually, the Universe expands because, well, the Universe expands... it's in the nature of the spacetime metric, as one of the solutions to Einstein's equations. It doesn't (necessarily) have anything to do with kinetic energy... it's not that planets, stars, etc., are flying into empty space. It's that space itself is growing larger with time."
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I have read that it is basically kinetic energy that causes the expansion of the universe--leftover outward-moving energy from the big bang itself. This outward momentum (maybe not exactly the right term) is countered by gravity. To imply that it is "inherent in the space-time metric" means that there is some force causing expansion.
That said, recent supernova observations actually did indicate that the expansion of the universe is *accelerating*, which means that there *is* a force causing expansion of the universe. But this acceleration to the expansion is different than the initial expansion itself, which is basically kinetic energy. I realize that space itself is also expanding, but that is a *result* of matter expanding, not the *cause* of matter expanding.
_____"That being said, the study mentioned in the story focuses primarily on brain structures. This pisses me off. One of the lamest things about current cognitive neuroscience is the common misunderstanding of the difference between structure and process. Given the little we know about how the brain works (yeah, we're getting good info about the molecular level, and we know in general what larger regions like Broca's area are responsible for, but we have woefully little info about how these structures actually work), idiot PR people take brain findings and blow them out of proportion.
The fact is, if you want to talk about intelligence, you have to talk about behavioral measurements. Looking at structures can, at best, tell you if something is wrong. So, yeah big deal, major structures are heritable, given the fact that environment has been shown in better studies to play a key role in intelligence, we shouldn't rely too much on these findings."
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I agree that intelligence must be measured by behavioral measurements, but that does not mean that structure is irrelevant. Granted, we do not yet know much about brain structure, and even less about how those structures comprise intelligence. However, I am surprised that a cognitive psychologist would discount study of structure as pissing him/her off. Studying behavior will only give us a sort of "black box" model of intelligence--what comes out of the black box (i.e., behavior). If we want to understand behavior more fully, and the causes of the behavior, we MUST try to look inside the black box, the structure of the brain, to figure out what is going on in there. We have input (environment, previous mental states) and we have output (behavior). Inbetween is the structure and biology of the brain. To discount study in this area is to ignore a difficult but promising avenue of research, and the only avenue of research that can answer some fundamental questions that behavior studies cannot answer--like how decisions are made, how memories are formed, etc. Behavior tells us nothing about these, and never will, because it does not attempt to inquire into the mechanism that controls or brings about the behavior. Behavoir study only looks at the results of intelligence, not the source of intelligence.
I don't know much about Clarke's satellite idea, but I do know that you have to actually be able to BUILD your idea before you can get a patent (it's caled reduction to practice). If there were technical hurdles that had not yet been overcome at the time he submitted it, he cannot fulfill the requirements of the statute to get a patent. (For example, if there were no way to launch such a device at the time....) I can't patent "Lightspeed travel" without knowing how to accomplish it. If I could, then when someone actually did figure out how to travel at c, I could claim I owned it without ever having invented it. And that would just be wrong. Wrong I say.
Didn't they put an eel brain inside a little go cart like device already? The eel, which in real life oriented itself relative to light from above, followed light sources around inside its little go cart using its own brain to "control" the circuitry of the go cart. Maybe this is something different. eels have neurons that are much larger than human neurons. Maybe it is no trick to attach big neurons to electrical circuits. Anyone hear about the cyborg-eel?
Slashdot Mirror
Also, do you know how we detect them, since they only interact with the weak and gravity forces? I have read a bit about the underground neutrino detector that basically blew up in Japan, and it sounded like they were somehow getting photon readings from passing neutrinos--but if they are truly WIMPs, how is that possible?
Man, I love cosmology.
I am not surprised you haven't heard of an actual study that WIMPs can form large chunks of matter, since WIMPs are still purely theoretical as far as I know. No one has ever detected one, have they? Neutrinos interact with the weak and gravitational force, but they have no mass. . . maybe they are WIMPs? Again, IANAPT.
Actually, most MACHOs are thought to be failed stars--white and brown dwarfs and the like. I disagree that this object they found is in the "known" column as far as frequency of occurrence. This article supports me (found on a quick search), as well as many other things I have read. It is not well known how many failed stars populate the universe or even our own galaxy, or even how many white/brown dwarfs may populate the Kuiper Belt and Ort Cloud of our own solar system. This isn't known becuase the objects themselves are very hard to detect, because they don't emit much EM.
But I disagree that they need to change their method of inquiry. This very article shows that, given a bit of evidence, cosmologists are very willing to accept the mundane explanation. And this article also points out that they are in fact pursuing the evidence to support the mundane theories.
You portray the scientists as "assuming" many things but I don't see it. The fact that they come up with wild theories does not mean that they are ignoring the obvious. It's jus that, in the absence of evidence, either the mundane or the exotic explanation could be correct. So they don't throw either theory out. I don't see them "making 'conjectural' observations...that is, assuming that an unobservable activity has been proven simply because something observable has occurred." This article certainly does not imply that, quite the opposite in my opinion.
My current understanding is that dark matter is just normal matter that doesn't emit light. For reference, all matter does 'suck in' light (meaning the energy is absorbed, usually given off as heat). WIMPs (weakly interacting massive particles) are theorized not to interact with the EM field--no photon coupling--so they (theoretically) do not suck light, or reflect it, or interact with it in any way. This is one of the other candidates for dark matter, the more exotic candidate. What this article shows is that they have found "normal" matter that can account for he apparent gravity in galaxies, "normal" meaning regular old EM interacting matter that we can see if only we shine light on it. MACHOs are such normal matter, which we can't see only because they don't emit or reflect enough EM radiation for us to detect, basically rocks in space.
I think the term "dark matter" does not necessarily apply only to non-luminous matter. I think it is used to refer to any unobserved matter that can account for the apparent gravity we see in galaxies. MACHOs have been a candidate for dark matter for a while, because they are mostly failed stars that do not emit light (at least not enough for us to see), though they do interact with the EM field. Other candidates for dark matter are indeed non-luminous, even non EM interacting (WIMPS-weakly interacting massive particles--that only interact with the weak nuclear force and gravity, but not EM so they can't be "seen" using light).
I don't think the argument for dark matter has to do with the expansion/contraction of space-time (i.e., the universe). I think the argument for dark matter is based on gravitational models of galaxies and the idea that, according to current theory, most galaxies do not appear to have enough (visible) matter to create the gravitational force needed to hold that galaxy together. The expansion of the universe appears to be accelerating. See one article on this here.
That is the spookiness of quantum mechanics. See here for a summary of quantum teleportation using entangled particles.
And I don't think they would need two different lasers emitting entangled beams. One laser could have its beam split, same as in normal holography.
If you could build a similar device, without looking at the details of the patented devices, you would probably not even infringe their patent. I would be willing to bet they can only get protection for the particular way they made their devices, and their technique would have to be "non-obvious" in order to get a patent. They couldn't patent a "flying robot" because such already exist or are obvious to build given current technology. Their protection is probably narrower. Of course it depends on the breadth of their patent protection, but if you built your own flying bug, you would probably not come up with the same bug they came up with (unless you looked at their patent...). If not, you would not infringe their patent.
I agree that most of the recent changes have potential for gross abuse. But, (and I realize I will get flamed here on /. for this, as well as modded into obscurity) there are mostly good reasons for the changes, at least temporarily. It is a balance of freedom versus security, and the pendulum has understandibly swung toward security recently. So we lost a little freedom for now. How has your life actually changed because of it? I daresay that few people (barring those of middle eastern descent--they are definitely feeling the effects of this) have been affected by the changes in the laws at all. And please don't forget the reason for all this--would you want a suitcase-sized dirty nuke detonated in your home city? It wouldn't be Hiroshima, but no one could live there for 1,000 years just the same. Before we bash the gubbament, maybe we should remember to weigh the loss of rights correctly against the increases in security brought about by these changes.
I agree that we have been getting a lot of patriotic news recently, but criticism of the "war on terror" is easily found in the US media. NPR recently had an article discussing the fact that there have been double the complaints filed by university professors for being reprimanded, etc. for expressing their view on what Bush is doing. In fact, the article said that it was mostly PRO WAR professors that had most often been punished for expressing their views.
Yes, duh. But since we are talking about the big bang model, and since this model posits that all these particles (i.e., all matter in our universe) are moving away from each other (NOT in the same direction) then you have either swallowed some pretty amazing initial conditions which you have twice implied need no explanation, or else there is a reason for the particular movement of all this matter. Your glib reference that space-time is just that way isn't very satisfying. I also don't think it is correct, with all due respect. You obviously know some physics.
A cosmological constant acts like a pressure density defined everywhere in space and keeps the metric expanding ever faster. But it doesn't exert a "force" in any standard usage of the word. We don't need a repulsive force to accelerate the expansion, because space itself is exapnding and carrying the matter along with it.
Ah, we agree, though not on terminology. You can refer to an added term (the C-constant) and deny that forces exist, but then you have to admit that the added term includes the effects of a force.
And again you say we don't need a "force" to explain the acceleration of expansion. I guess we don't as long as we are using a math model that does not refer to force explicity, though it includes the effects implicitly by another method. But I am not sure you understand this. You have repeatedly stated that no force is needed because space itself is expanding.
Now, let me be clear, I am not talking about mere expansion, but acceleration of the rate of expansion--a different thing by one time differential.
This definitely requires some kind of force to be acting. Particles don't change their velocity without a force (as you correctly pointed out). Neither does space-time. It sounds like you think we cannot inquire into why space-time behaves the way it does--it is just the metric, or the constant. But space-time depends on the matter therein, period. The two (space-time and mattter) are self-referential--they both affect each other, and matter EFFECTS space-time, i.e., brings it about. Space-time does not bring about matter. The only reason we have space-time is to describe how matter (and energy, to be technically correct) acts. If you take away the matter and energy, the idea of space-time is meaningless.
The reason space-time is expanding is, respectfully, not "because it is inherent in space-time" as you have twice stated (that is the original reason I posted--to disagree with this gross oversimplification). It is because the matter in our universe is moving. Move the matter, and your space-time geodesics, etc. change. If you have matter flying apart, away from other matter, then you have a space-time that looks like ours does, i.e., expanding. But to say that matter (and our universe) is expanding because the space-time metric looks the way it does is backward. That implies that the universe is governed by our model of the universe. The metric, the cosmological constant, these are just part of the model. You can't refer to them in order to explain, only to describe.
The deSitter Universe is just a model of the universe with zero curvature--one in which there is *exactly* enough energy to keep the matter therein expanding forever (i.e., zero curvature).
I have never heard of a space-time model for a matterless space-time. I couldn't find it under deSitter. I would be very interested to read such, if you can provide a cite.
I agree that the expansion of the universe is not caused by some currently acting force, I believe you may have misunderstood my post on that point. But your statement seems to indicate you do not seek any initial cause for the state of the expansion--that it started expanding for no reason. Even a newtonian particle at constant velocity (to use your example) needs to somehow obtain that velocity. In the case of the matter in our universe, I always thought it was because of the initial energy density and radiative pressure from the big bang, giving an initial impetus to matter. Indeed, other authors seem to think this too, see here for example (just somethign I turned up on a quick search).
Finally, something that may have caused some confusion, I mentioned recent supernova observations and the idea that there *is* a force causing *acceleration* of expansion. What I posted is accurate, do a google search for quintessence or dark energy.
The correct description is as the other poster says: space is expanding, though gravity is slowing down that expansion.
Space expands because matter is expanding or moving. The space-time and matter are not separable, you can't talk about a space-time metric existing without matter existing somewhere, because matter dictates the structure of the metric (as well as the metric dictating the movement of matter).
You also said:
No. The metric changes with time, but there are no forces involved in gravitational phenomena.
I think you are confusing the difference between models and reality. Both Newton and Einstein came up with models. Einstein replaced a gravitational potential (the source of a force) with a space-time metric. You can view the universe as one in which matter causes a gravitational force to be exerted or one in which matter causes the geodesics of space-time to be shaped differently, which causes matter to accelerate. They are one in the same. To say that "there is no force involved in gravitational phenomena" is merely a choice of models. It also totally misses my point.
My point was that if the metric is indeed changing with time, there has to be a reason behind it--the metric does not control the universe, it only models it. The metric changes locally near matter because the matter is there, not because it is "inherent in the metric" (unless you think the metric creates the universe, rather than the metric merely modeling the universe). Likewise, the metric changes with time because of other conditions, namely, the negative vacuum energy density (positive vacuum pressure). This is what caused the initial expansion of the universe--hot radiative pressure when so much matter and energy were confined to a "small" region (though size doesn't have much meaning since it was really the entire universe), creating a really high energy density.
I also wrote:That said, recent supernova observations actually did indicate that the expansion of the universe is *accelerating*, which means that there *is* a force causing expansion of the universe.
You replied:No, that's not true either. The geometry of space obeys field equations, and can change with time. No forces are involved. What you say would be true if gravity were described in Newtonian terms by a force, but general relativity does not describe any gravitational phenomena in terms of forces.
Gravity *is* described in Newtonian terms by a force. You seem to think that because one model (Einsteins) does not refer to the term "force" then force does not exist. The "force" in Einstein is buried in tensor equations, and how they determine the shape of geodesics, which determine how matter moves. But both models describe the same phenomena (though I agree relativity does it more accurately).
And finally, you write:Again, no. The matter in the universe flies apart because the intervening space expands.
Whatever, you desire to contradict literally everything I posted has gotten in the way of your understanding. Your statement indicates that you think space-time's expansion causes matter to move apart. This is exactly the opposite of what is happening. Space-time would not be doing what it is doing if there were no matter. Ultimately, space-time is used to describe the location and effect of matter (via gravity) on other matter. Matter determines the shape of space-time. Movement of matter causes the metric to change over time. I agre the two are self-referential, but without matter, the space-time would not exist. And anywhere you have matter, you will have space-time. Matter is the important quantity.
Ouch. How about instead, people aren't willing to sacrifice themselves for the good of the unappreciating masses? In each individual case, it is obviously best for that individual to do what they do (i.e., "fold" as you call it), or else they wouldn't do it. Granted, it might be better for everyone if everyone stood up and fought, but the first guy who does that gets his head blown off. It is therefore (to me) understandible for someone to duck.
As a direct consequence the DMCA would be in violation of the 1st ammendment. Any patents on software would be voided because text to the best of my knowlage is only copywritable, not patentable. The headache of stupid digital legislation would hopefully be behind us.
I am not sure I understand your post. First, most software is copyrighted, not patented. And I also thought the DMCA was the Digital Millennium Copyright Act. DOesn't deal with patents. Why would the DMCA be in violation of the First Amendment if machine readable code were considered human readable text?
A flaw? I think separation of powers is one of the main strengths of our government. Imagine if the same set of people were in charge of creating *and* interpreting the laws. Goodbye constitutional protection. Every law would be constitutional, no matter what it said.
One distinction for your example: Razor blades have legitimate, non-terrorist uses. Hacking software (or whatever it was exactly) is *designed* to do something "illegal." Are there other legitimate purposes to what Felton did besides violate copyright? Maybe so, but it sounds like it was designed to be "misused."
_____"The problem here is that it's perfectly legal for large corporations to strong-arm the little guy with threatening letters, and subsequently fail to follow through with the threat. "_____ This is true. You can't get into trouble for threatening to sue someone. You sound like this is a bad thing. While I think bullying with threatened lawsuits is a bad thing, I have two points to make. First, the lawyer who wrote that threatening letter could, if he misrepresented his client's legal position (or anything else in the letter) be subject to sanctions. It isn't technically "illegal", but a lawyer cannot lie about things like thatunder most states' ethics rules. If the lawyer could not make a straight face argument that he had a viable suit, then he can't threaten someone that he has a viable suit. (Note a caveat here--making a straight face argument is very easy to do, so this isn't much of a hurdle.) Second, think of what would have to happen to prevent a corporate entity from sending threatening letters like this. What exactly was the plaintiff asking the judge to do? I don't know, I only read the excellent summary of the hearing, but I do think that any remedy against the corporation would be onerous under those facts. To say that they did something actionable could mean that anyone who sends a letter claiming a legal right (and threatening to sue) will be forced to follow through. That would apply not only to the corporation, but also to me and you when we write to Orbitz saying, "You breached our contract for the ticket I purchased...." Orbitz can tell us we are wrong, then sue us if we don't sue them because we "threatened" them. That is essentially what it sounds like the plaintiff was asking for: punish them for threatening to enforce what they think are their legal rights against me. Again, I have not read the papers. IIAL.
"Actually, the Universe expands because, well, the Universe expands... it's in the nature of the spacetime metric, as one of the solutions to Einstein's equations. It doesn't (necessarily) have anything to do with kinetic energy... it's not that planets, stars, etc., are flying into empty space. It's that space itself is growing larger with time." _____ I have read that it is basically kinetic energy that causes the expansion of the universe--leftover outward-moving energy from the big bang itself. This outward momentum (maybe not exactly the right term) is countered by gravity. To imply that it is "inherent in the space-time metric" means that there is some force causing expansion. That said, recent supernova observations actually did indicate that the expansion of the universe is *accelerating*, which means that there *is* a force causing expansion of the universe. But this acceleration to the expansion is different than the initial expansion itself, which is basically kinetic energy. I realize that space itself is also expanding, but that is a *result* of matter expanding, not the *cause* of matter expanding.
_____"That being said, the study mentioned in the story focuses primarily on brain structures. This pisses me off. One of the lamest things about current cognitive neuroscience is the common misunderstanding of the difference between structure and process. Given the little we know about how the brain works (yeah, we're getting good info about the molecular level, and we know in general what larger regions like Broca's area are responsible for, but we have woefully little info about how these structures actually work), idiot PR people take brain findings and blow them out of proportion. The fact is, if you want to talk about intelligence, you have to talk about behavioral measurements. Looking at structures can, at best, tell you if something is wrong. So, yeah big deal, major structures are heritable, given the fact that environment has been shown in better studies to play a key role in intelligence, we shouldn't rely too much on these findings." _____ I agree that intelligence must be measured by behavioral measurements, but that does not mean that structure is irrelevant. Granted, we do not yet know much about brain structure, and even less about how those structures comprise intelligence. However, I am surprised that a cognitive psychologist would discount study of structure as pissing him/her off. Studying behavior will only give us a sort of "black box" model of intelligence--what comes out of the black box (i.e., behavior). If we want to understand behavior more fully, and the causes of the behavior, we MUST try to look inside the black box, the structure of the brain, to figure out what is going on in there. We have input (environment, previous mental states) and we have output (behavior). Inbetween is the structure and biology of the brain. To discount study in this area is to ignore a difficult but promising avenue of research, and the only avenue of research that can answer some fundamental questions that behavior studies cannot answer--like how decisions are made, how memories are formed, etc. Behavior tells us nothing about these, and never will, because it does not attempt to inquire into the mechanism that controls or brings about the behavior. Behavoir study only looks at the results of intelligence, not the source of intelligence.
I don't know much about Clarke's satellite idea, but I do know that you have to actually be able to BUILD your idea before you can get a patent (it's caled reduction to practice). If there were technical hurdles that had not yet been overcome at the time he submitted it, he cannot fulfill the requirements of the statute to get a patent. (For example, if there were no way to launch such a device at the time....) I can't patent "Lightspeed travel" without knowing how to accomplish it. If I could, then when someone actually did figure out how to travel at c, I could claim I owned it without ever having invented it. And that would just be wrong. Wrong I say.
Didn't they put an eel brain inside a little go cart like device already? The eel, which in real life oriented itself relative to light from above, followed light sources around inside its little go cart using its own brain to "control" the circuitry of the go cart. Maybe this is something different. eels have neurons that are much larger than human neurons. Maybe it is no trick to attach big neurons to electrical circuits. Anyone hear about the cyborg-eel?