"low bandwidth, high quality, low processing power" is completely impossible. Bandwidth+quality equates into space, and processing power equates into time. There's always going to be a trade off between time and space.
Actually, MACHOs are a specific thing, as MACHO is an acronym for MAssive Compact Halo Object. This implies that it has significant mass, is quite compact, and located in the halo of a galaxy. This says quite a bit more than "rocks".
No, it is true that QED is still the most accurately verified physical theory. The binary pulsar set doesn't prove GR to 14 orders of magnitude. It proves -one- prediction from GR to 14 orders of magnitude.
Note that this is *stupid* to say as well, because we don't even have a good measurement of G to more than a few significant digits, I believe (the only one I can see is the freq-shift method from '82, and that was.0128%). GR doesn't agree to 14 decimal places to the perihelion shift of Mercury, for instance.
To be honest, you're splitting hairs here - yes, the Hulse-Taylor Pulsar measurement was one of the most accurate verifications of a physical theory known to date, and that's very impressive. But, that doesn't validate GR to 14 decimal places in every prediction it makes.
QED is valid to 10 decimal places in something like 12 or 14 different independent experiments. That's something that GR can't even come close to yet.
One is, if your theory is REALLY good, you can show why something is from very basic principles. Thus, you don't have any precepts to start on other than a few basic ones. For instance, you can say "particles have spin?" and someone may say "yes, but at some time, spin might not have existed." If your theory is extremely good, you can say what would happen if spin didn't exist. In actuality, relativity already says that - if spin didn't exist at some point in time, then relativity wouldn't have existed - that is, spacetime wouldn't have a 3+1 signature.
Conversely, if we find evidence of spin, that implies that spacetime has (at least) a 3+1 signature, or at least has some symmetry which posesses 2 Casimir invariants.
Physics isn't generating 'laws' that have to be 'obeyed'. We're saying "the universe IS this way, that IMPLIES this", we check it against experiment, and *that* can't change. We know, for instance, that conservation of energy holds because the universe is time-symmetric. If we abandon conservation of energy, we have to assume that the universe is NOT time-symmetric, which disagrees with tons upon tons of experiments (including ones which measure all the way back to 300,000 years after the big bang, so we at least have to assume that conservation of energy has held for ~10 billion years).
This is why astrophysics is important - it tells us "how constant are the 'silly little laws' we come up with?" and trust me, based on what we've seen so far in astrophysics, my God, they're constant.
(Just as an example - it was once thought that gravity's strength changes over time - with the density of the Universe. This is Brans-Dicke theory. We now know that Brans-Dicke theory, if it is correct, contributes very VERY negligibly to gravity's strength. That is, if gravity *has* changed over time, it hasn't changed *much*.)
OK, first simple correction, actually, changing the speed of light changes the *distance* unit, not the time unit. We define time as cycles of a cesium atom, so the correct definition is that one *meter* is the distance light travels in some fraction of a second, per SI definition.
QED is the most well tested consistent theory that physics has ever seen. GR is not NEARLY as well tested as QED is. Blandly stating that QED has only been checked to 10 decimal places is crazy - QED is consistent to 10 decimal places with about 12 (if memory serves) completely different experiments. That's far more impressive than any test GR has undergone.
Alpha is the most well-known physical constant in physics right now, and suggesting that it changes, while it is possible, would not be in the least bit consistent with astrophysical findings. QED is more than consistent over well over several decades of orders of magnitude. GR doesn't win there at all.
QED is very simple, with absolutely *no* ad-hoc rules. The ad-hoc rules only come into play when
a) a physicist asks a meaningless question (What is the sound of one electron clapping?)
b) other forces come into play. You're talking about QED - that is, quantum *electrodynamics* - electromagnetism only, other particles/forces not invited! (Yes, this includes the weak force - otherwise QED would be quantum electroweakdynamics).
b) is to be expected, as a general unified theory doesn't exist yet, and a) is a simple extension of physicists who live in a macroscopic world trying to assign macroscopic ideas to a microscopic system (i.e. the 'location' of an electron). Any of Hund's rules could be seen to be ad-hoc as well, but a bit more theory and it all makes sense.
Now, if you mean the *Standard Model* is filled with ad-hoc rules, you're right. Neutrinos are all left handed... kindof. That sort of thing. That's correct. But QED is quite a solid theory.
GR is also anything but incredibly simple. It's simple only in the limit where you can take the interaction between two objects to be significantly greater than the Planck length, but anything smaller than that, and GR isn't so simple anymore. Simple reasoning: GR is continuous, QED is quantized. We can pull QED out from the quantized limit back to good old electrodynamics easily, but GR isn't nearly as lucky.
And, yes, I am a physicist as well, but I don't work in units where c is one.:)
I never said I agreed with current practices.:)
To be honest, though, prescribing HGH is seriously different than modifiying one's genes to produce more growth hormone. The difference? It's a personal choice, and it doesn't affect one's children. Screwing around with genes is *permanent*, that's why you need to be careful with it. This is why Britain bans alterations of one's germline (DNA passed to children). I don't necessarily agree with the ban, but I can understand it.
There's a clear and simple difference between "natural" variation and "unnatural" variation, and we really need to codify and define those differences.
Genetic modification really should *only* be done in a case where there is a clear and obvious defect in the DNA of a subject. For instance, modifying one gene in an embryo with sickle-cell anemia is perfectly fine. We know what the heterogenous phenotype does, we know what the homogenous recessive does. You don't tweak your DNA. It's not safe, and there's no going back.
Re: learning ability - there is a significant difference between what society considers "genius" and learning ability, believe it or not! Strangely enough, many people who are not that "bright" - that is, they don't learn quickly - can end up making the largest difference in science and engineering, simply because they take longer to understand something, and don't gloss over it like people who learn faster.
What I'm trying to say is that upping someone's IQ doesn't mean they're going to discover how to travel faster than light. We don't *know* what allows people to make those breakthroughs in science and engineering, and it could be that there *is* no 'know', and it has more to do with who the person is and the life they live.
Assuming that upping people's IQ, and making humans immune to disease, and giving everyone 20/20 eyesight will produce a world exactly like our own, only better, is naive and short-sighted. Diversity only *increases* the rate at which humans progress, not *decreases*.
That's not even the real problem, and I find it frightening that no one's touched on the real problem yet.
The real problem is that people "think" they know what's best for certain people - i.e., they 'think' they know that it's best to have 20/20 eyesight, or better than 20/20 eyesight, or immunity against all disease, or massive high IQs.
That's not true. That's not best at all, because society, science, and technology don't work that way.
Technology works in two ways - improvement and innovation. Improvement we understand - you take an existing design and tweak the hell out of it. See also microprocessors, and just about everything else. Now, here's the kicker - nothing that radically changes our lives comes from improvement. Yah. That's a harsh criticism, I know, but it's real, or at least close enough to real to be true.
Now look at innovation, and what causes it. Intelligence doesn't. That's the other harsh criticism, but it's also true. In fact, it's tough to say what DOES cause it. It just happens.
What does all this have to do with the current topic? If you've ever seen ST:TNG's Masterpiece Society, you know where I'm going, but don't discount me quite yet.:) If you eliminate the "weak" humans, you may get a rather bad side effect of a complacent and improvement-focused society. Innovation comes from necessity, and perfect (or somewhat perfect) beings don't need anything. If you don't need to fight diseases, you won't get the random benefits that come with the research. Trust me - getting pure science funded is hard enough!
You don't "improve" on kids, because genetics don't do diddly when it comes to making kids 'smart', if you think 'smart' means they'll win a Nobel prize someday. What makes kids 'smart' is an environment that constantly fosters growth and curiosity (curiosity being the big one right there) and THAT you're not going to fix with any combination of base pairs. Twins are the perfect example here, as just because one twin does something groundbreaking doesn't mean the other will.
You're not trying to make "arbitrary" categories. They're not arbitrary, I can define them rather quickly - anything that causes a human to die prematurely (normal lifespan) and (this is the tough one) anything that hampers a person's ability to live his or her life as anyone else. This DOES exclude futzing with IQ, messing with strength, or slightly abnormal eyesight, or anything like that. There's no reason to do anything like that, because there's no problem. The slippery slope is deciding what hampers a person's ability to live. I agree with that. However, why in God's name would you want a) immunity to 'diseases' (assuming that was even POSSIBLE, which it isn't) or b) everyone to have better than 20/20 eyesight? Getting sick is necessary - you don't want immunity from disease, you want to be able to cure them all (and to keep getting better at curing them). And the eyesight thing is just pointless. After all, not all blind people want sight.
So, what am I saying? OK. I agree that we should try to fix defective genes, because we know what they do. That's simple enough - if someone's going to die, or need constant medical supplement, you need to fix that. But you need to strictly, strictly avoid trying to fix something that isn't broken. The idea of genetic engineering is to throw more humans into the potluck called life, not to try to tip the pot over.
LinuxBIOS requires a Disk-On-Chip. I don't think it's possible without it. In addition, I don't think a Disk-On-Chip solution is possible without LinuxBIOS, as the only place you can typically install Flash is in the BIOS slot, and without a BIOS, well, you have to have LinuxBIOS.
I can't believe people are abandoning support for RS-232 serial ports. I can't connect two computers using three wires and two USB ports. They're useless.
I fully believe if we ever make contact with an alien race, we will connect our computers via RS-232.
I'm really confused. I'm hoping not to get flamed by this, but honestly, why was the portion of the law which said "free software doesn't need a warranty" changed to "Open Source software doesn't need a warranty"? There's plenty of "free as in beer" software out there that for some reason, they didn't (or couldn't) release the source code. Why should they have to provide a warranty? They're releasing it simply because they think it would be of use to the community - they might not have the time or money to support it.
Or did they just change it to "free as in beer" and "free as in speech" are both exempt now?
Electrons don't have width. They are fundamental point particles (to our best knowledge).
Tunneling will become an issue roughly when you're within a couple of angstroms of the surface (~ radius of a hydrogen atom or so).
It's highly unlikely that electron tunneling will ever be a problem - if you ever build a chip that electron tunneling might be a concern on, I guarantee you're going to have defects in that chip that short two of the wires, rather than needing to worry about electron tunneling. Without major overhauls in process control, this just won't happen.
On topic: AMD *has* had massive screwups with their processors - it just isn't advertised as it doesn't affect most people. Except me, of course - I have an old AMD-K6 200 with the bug that causes it to be unstable with >32MB of RAM. Happy day.
Though it should be noted that AMD did offer to replace these processors- I just didn't know about it till I got Linux, and it told me.
Wow. That link is by far the worst example of idiot math I've ever seen in my life. Has the author ever *read* a relativity textbook?
What is claimed in the link:
Motion is impossible because a component of the "4-velocity" created by "dx/dt" is a "unitless" number.
OK, so why is this stupid?
The position of a particle, x, is defined as
x = (ct, x, y, z) in some reference frame - it is NOT (t,x,y,z): that's *stupid*: space is space, time is time. But when you consider that there is a common velocity throughout all space and reference frames - the speed of light in vacuum - then 'time' has to be linked to 'space' somehow - and it's linked through the speed of light in vacuum, c. You can work this out on a sheet of paper using the Pythagorean theorem.
OK. So even the 'simple' 4-velocity dx/dt now looks like dx/dt = (c, dx/dt, dy/dt, dz/dt). Nothing's unitless - everything has dimensions of distance/time. Thus, we have already disproven the statement in the above link. So, we can stop here.
Motion in spacetime is simple - it works exactly as it does in Euclidean space/time. Want to create motion? Just shift to a reference frame that is moving at a different 3-velocity using Lorentz transformations. Boom. You've got motion in spacetime - you can then follow the object's position as it moves through spacetime.
This is a very weak interpretation of the EPR experiment: there is no reason to believe that "physics is fundamentally nonlocal" in the sense that you're talking about - especially when it comes to the interpretation that it will produce "instant" anything.
The hardest part of quantum entanglement to understand is the fact that Nature is both fundamentally local and nonlocal at the same time. Yes. You heard me. That's exactly what I meant.
Interactions are local: a particle at point B ten light years away from a particle at point A can only interact with an on-mass-shell particle intermediating the two. That is, for an electron which emits a photon which is reabsorbed by a particle ten light years away, the photon is on-shell - or VERY nearly on-shell: q^2 = 0. They can't exchange an off-mass-shell particle, because it would need to live too long. What does this mean? It means that space essentially determines the momentum scale of an interaction - i.e., interactions are fundamentally *local*.
Particles, however, are fundamentally *nonlocal*. As D. Griffiths might have put it in his wonderful QM text, "Even God doesn't know the exact location of an electron" - because the concept of an "exact location of an electron" doesn't exist. Yes. That's right. It's not an inherent limitation in humans, or the Universe, or God in this case. It's the way electrons are. If you asked God what the exact location of an electron was, he'd look at you as if you were stupid, because you'd be asking a complete nonsense question. Asking "where is an electron?" is nonsense. The concept of "where" doesn't exist quite as firmly for an electron as we think it does for us.
So, how do you reconcile the concept of the EPR experiment? It's because the concept of the "location of the photon" is not real. The photon is located along the entire spread of its worldline, as is its pair photon with opposite polarization - or at least, the photon's polarization is (talking about the "location of a photon" is, as I said, meaningless). Same for an electron/positron pair in the classic EPR experiment. When you measure the polarization (or spin) of the photon (electron), you're measuring the polarization of one part of the *combined pair*.
Of course, once you do that, you localize each portion of the state: interactions are fundamentally local, after all.
You said it yourself. All that exists are particles and their interactions. Particles don't provide the structure of spacetime - their interactions do. You can't have instantaneous changes in position because that would suddenly cause all the interactions that those particles were undergoing to become nonlocal.
The only way you can have "instantaneous changes in position" is if you physically make the space close - i.e., a wormhole - then all the interactions stay local. They're then in a multiply connected topology, but there's nothing wrong with that. However, good luck actually predicting the dynamics of creating a wormhole. We don't have math for 'breaking' a continous object and then 'reforming' it again (see also waves crashing). Might be possible, might not.
But in any case, "instant" communication is insane without invoking the concept of a multiply connected universe.
See my parallel post. Build a machine yourself, or try to find a different machine like this, but don't buy this one. PC Chips motherboards are horribly unreliable and just all around trash.
Don't bother buying this unless you plan on throwing the rest of your money away.
Notes: avoid this vendor like the plague. They're well known in the hardware industry as being the absolute worst (and I do mean the worst) motherboard manufacturer in the industry. I have bought or obtained 3 motherboards from this company, and those're the only 3 I'll ever have. 2 never worked in the first place, and the 3rd has serious BIOS problems (which I worked around, but it still can't keep the system clock on power off).
Dimensions are only orthogonal if the metric is trivial (i.e., diagonal).
The "metric" as I stated above is a 4-dimensional tensor (matrix, essentially) which (basically) provides the coefficients in the distance measure.
i.e., in 3-space, we have a distance measure of
ds^2 = dx^2 + dy^2 +dz^2
Here, the metric has a 1 in the dx-dx term, a 1 in the dy-dy term, and a 1 in the dz-dz term: in terms of a matrix, this would be just the three-dimensional unit matrix.
General relativity says that the metric is affected by the presence of matter and energy, so therefore, depending on the spacetime configuration, the dimensions may not be orthogonal. Near a black hole, this is actually distinctly not true - there is significant radial/temporal mixing in certain coordinate systems. Granted, you can always define a coordinate system with orthogonal coordinates.
In any case, you were mainly talking about special, rather than general, relativity here. The 4-dimensional metric being talked about is a Minkowski space - time is distinctly separate from any others, because in the Minkowski metric, we have
ds^2 = dx^2 +dy^2 +dz^2 - c^2 dt^2
note that time has a changed sign. We call this 3+1 spacetime.
All special relativity does is define exactly how you transform from one coordinate system to the next - in this case, via Lorentz boosts. Lorentz boosts in one direction have both a spatial boost and a temporal dilation, which is what you are talking about. It doesn't mean the coordinates aren't orthogonal - it just means that when you boost from one frame to a faster-moving frame, both the boost direction and the temporal direction are affected.
Short answer: you answered your question yourself - you said "rate of movement", but above you said "movement" - there's no reason to expect that "moving" is the same as "steady motion" - or, that a simple translation is the same as a velocity shift. In truth, it isn't.
Think about it this way. It's true, time and space are orthogonal. If I do a time translation (i.e., in my coordinate system I redefine t = t + t0) it doesn't affect the x, y, or z coordinates. Likewise for spatial coordinates.
But there's no a priori reason to expect that when you start talking about another frame of reference that is in constant motion with another that it shouldn't affect the other coordinates. After all, you're already mixing things: you have to talk about z = z0 + vt, for instance. Here, instead of the boost simply being z = z0 + vt, there's a Lorentz factor as well.
Re:A lesson in collaborative science
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Excess Heat
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· Score: 2
Hey!
Go fig, this is exactly what all of us reading the NYT's article from last Tuesday are wondering re: "we have demonstrated the existence of a repulsive dark energy via supernovae observations."
What the hell were they thinking making such a bold claim? I definitely agree with you. You never - ever - ever claim something until you have one hell of a mountain of data behind you.
Otherwise you end up looking like an ass, just like P&F, the Weber bar experiment, and California's monopole - all great examples of why physics works best as a peer reviewed process.
I could be wrong, you know. If I am, I'll join you over in California tomorrow using a maglev utilizing monopoles where we can solve their power problems using cold fusion and worry about how we're going to survive in a few days when the black hole at the center of the galaxy finishes consuming all the stars in the known universe. Of course, the cosmological constant will come and fix all of our problems. No tongue in cheek here...
Re:According the CF guys it's not the neutrons
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Excess Heat
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· Score: 2
Which is half the reason the physics community thinks P&F are idiots.
One: they didn't have the equipment to detect neutrons. They claimed it because they knew they had to.
Two: Someone right friggin' beside them in the physics department with a running neutron detector at the time when their experiment was running didn't see any excess neutrons.
The smoking gun, IMHO, is the fact that P&F aren't dead. Regardless of what reaction is occurring, you're going to produce high energy reactants that are going to do severe genetic damage. They're not dead - therefore, they didn't produce squat.
Argh. I replied to this before, but Slashdot ate it. What a pain.
I don't agree with your first argument - it's very weak, considering that GR is not a QFT. There's no reason to believe that the vacuum has anything but zero energy, and Mach's principle makes you want to believe that it is zero (Einstein was quite distressed to find out that an empty (Friedmann) universe was a solvable solution of the equations) since in this case you don't have a global matter field to define any of the physical parameters such as mass, etc, and you're essentially defining them in this case via an external field, which is exactly what Mach's principle tries to avoid.
In some sense, you expect the GR limit to have a zero vacuum, since GR should be a 'smoothed over' limit of whatever a QFT of gravity is, if one exists - in some sense, you expect quantum fluctuations to not strongly affect the GR limit (although it very well might). This argument is weak, granted, but GR deals with stress-energy density, not with the gravity of spacetime itself, which is a distinctly quantum process. My gut reaction is still that using vacuum energy to justify a cosmological constant isn't proper, as you're stretching the bounds of where GR is valid.
The second argument is perfectly valid - kindof. The whole idea of "it's going through several phase transitions, so it should be absolutely huge!" is weak, especially with the whole idea of renormalizability. I have little doubt that a final QFT of gravity (again: if there is one) will have an infinite bare cosmological constant.
To be honest, I don't know. My instinct re: the cosmological constant is the same as it is re: dark matter. I don't think we understand gravity at these scales - I really don't. Galaxies look like they have too much mass, galaxy clusters look like they have even more excess mass, all makes me wonder whether or not it's a scaling effect rather than a 'missing mass' effect. With the cosmological constant, it could be the same sort of thing. Again, I could be wrong, but I've always tended towards "the universe is simple" rather than "the universe is bizarre".
Again, I'm not saying that the result isn't real. I'm saying that a good experimentalist can always come up with reasons that the experiment might not have worked.
You're using "invalidate" a little too strongly - I didn't say he would be able to invalidate it - I said he would be able to come up with reasons that would invalidate it. Whether or not any of those reasons pan out to be true is another question.
As for whether or not the presence of a cosmological constant is bizarre, it is bizarre. It's not what we've seen on a smaller scale, though granted our evidence on a smaller scale was much weaker. It's not what was expected - it implies significantly new physics.
As for the final comment, that's just plain wrong - flat out. The flaws in an experiment don't widen error bars - error bars come mainly from statistical considerations and uncertainties in known quantities. They provide a measure of precision, not a measure of accuracy. Going back to the cosmic ray example, for instance, those experiments were way off - but they had great precision. Their error bars were extremely tiny - it just happened that their experiments weren't measuring the right thing, though they didn't know it right at the time (they guessed it afterwards). Depending on the flaw in the experiment, it could be fatal - there are plenty, honestly plenty of those.
Considering the astro data, I know one group was using SN 1a's, which, when you look at the data, are not wonderfully consistent. In fact, there are several astronomers who are beginning to say we don't really know what SN 1a's are (conventional knowledge says that they're white dwarves that exceeded the Chandra limit). Several possibilities jump to mind, including evolutionary concerns and not understanding the physics quite right. These can all be checked, and in the few papers I've read, I haven't seen enough checking to convince me. Again, that could be just me - I'm notoriously hard to convince.
So maybe what I am suggesting is that the teams actually look and see what would have to be true in order for lambda=0 to be within error bounds. Is this bad science, since you're shooting for a specific value? Not really - it's a sanity check. You're just making sure that what you're saying is *guaranteedly* true, and if you have a detractor - someone who insists lambda=0, for instance - you can tell them "well, if lambda=0, then such and such would have to be true."
Weber's measurement of gravitational waves wasn't within two sigma of zero either. I personally don't think that the mass of a few thousand stars is being turned into gravitational waves at the center of the galaxy, though.
I'm beginning to think that this is simple miscommunication, but...
Yes. I am saying that a sufficiently good experimentalist can always invalidate his own experiment (at least initially), because a good experimentalist knows the weak points and what can be improved. If you don't, you're lying to yourself. A good experimentalist, faced with a result that is way the hell away from expectations, will immediately go back to the experiment and stare at it for hours and come up with a dozen reasons of what might've gone wrong. Then, after all of those have been checked, he'll go to colleagues and ask for assistance. Then, after THEY'VE checked, and confirmed that's what's going on, then they might publish a quiet paper (or more likely, give a talk at a conference) to see if anyone can come up with an intelligent answer that they've missed. Then they'll go to press. That's what I'm talking about. If you can't do that, don't bother going into the field, as you'll end up ruining your reputation. Monopoles in California (it was California, right?) and the Weber bar experiment. Both classic examples of "what the hell??" experiments that should guaranteedly have been checked more thoroughly before going to press.
I think you're talking about an experimentalist in the last stage of the game, where they've run out of every answer other than the "new physics" answer. But still, at least some of those questions will be unanswerable without a new experiment (or should be. Maybe it was a perfectly designed experiment. But every experiment I've seen always has compromises inside it) and that's what I mean.
And no, I'm *definitely* not suggesting that every repeatedly tested experimental effect can be explained away. I'm suggesting that any questionable result in an experiment can be explained away right after performing the experiment. Now, if the results stand after testing as many of the limitations of the experiment as you can think of, then it's real. But no experimentalist in his right mind would ever believe a bizarre result right away.
Let me put it another way. I'm working on an experiment right now that is designed to look at high energy cosmic rays. We have a guess at what their flux should be. If it's orders of magnitude above that, I can immediately give a dozen things to check. Without hesitation - those are mainly instrument failure things, however. If everything seems to be working, I'll go out and check things myself manually. And if everything still seems to be working, I'll run another experiment to check to see if I can confirm my results. Then, if everything's still wacko, I'll ask colleagues for help.
I'm confused, actually, as you seem to be supporting my point - you admit that a good experimentalist will be able to think of more problems with the experiment. That's what I'm trying to say - that a good experimentalist can explain a bizarre result without automatically resorting to new physics, and then in the same breath suggest an experiment to check that problem. His explanation might be totally wrong - maybe the new physics is there - but he'll always be able to come up with something that should be tested first. Compare this to the amount of time it took experimentalists to believe the Solar Neutrino Problem. It took years before anyone believed that, and experimenters were always saying "maybe there's a problem, but we need more statistics" (the cheapest out, but still an out). This is taking far less time - maybe a year - and I just don't buy it.
As for the semantics argument, that's my personal preference, because repetition is what makes things true in people's heads, not truth - and even scientists fall prey to this. You hear something over and over, and it becomes true. If you hear "there is now significant evidence for a cosmological constant", you begin to believe there's a cosmological constant. If you hear "there is now significant evidence suggesting that our understanding of the expansion of the universe is incorrect" you begin to believe that there's a problem in our current understanding.
It's not silly to explain it away - if the explanation is testable, then it's a valid concern. If you're a good experimentalist, you can *always* come up with a better explanation than "bad physics" - especially because you know the portions of your research that were hacks - and there are *ALWAYS* hacks.:) So if you can't find a problem with your experiment that might explain something, honestly, you're fooling yourself. It might be that all of the explanations you can come up with are crap - I'm not suggesting that any experimental effect can be explained away - I'm just saying any good experimentalist can come up with problems with their own experiment, even if they're not real.
Anyway, take something from my field: in the 80s and 90s, a bunch of experiments all seemed to confirm that the positron fraction in cosmic rays increased at high energies. This made no sense - and fundamentally you don't want to believe it at all. But they all confirmed it, until the next class of experiments came along and showed "oh, wait, you didn't have good enough rejection."
The fact is that in a good experiment, they should've immediately guessed "um, we might not have good enough rejection" and in fact, some of them did suggest that, and that's what led to the better experiments. It might've been that what they saw was real, and their concerns were baseless, but they came up with the concerns, which is the important part.
I agree that the fact that several groups got consistent answers is suggestive, but far space astrophysics relies on far too many assumptions to suggest redefining physics on a small scale until you get a huge swath of data to back it up. Everyone nowadays seems to be hinting in every talk and paper that I read that "evidence is mounting for a cosmological constant": no. Evidence is mounting for a systematic problem in our data regarding the expansion of the universe. The fact that it MAY be explained by a cosmological constant is unimportant. The cosmological constant is a 'fudge factor' in these cases: you can't disprove it because you can fit it to the data. The fact that you can fit it to all the data just says that the experiments are all measuring the same thing precisely - not necessarily accurately.
You're assuming that there exist no anti-entropic processes, which, while likely, may be not true, thanks to Hawking radiation. Not my belief, though, because I don't belief that one quantum process in the presence of a unique macroscopic object can fundamentally change the way the universe works. (Anti-entropic meaning they destroy information, which means they lower entropy, breaking the Second Law. This may be possible. Imagine a black hole sweeping through a cloud of lowest-energy state electrons and photons, and then in a large amount of time (10^100 yrs) turning those lowest-energy state electrons into a massive burst of high energy particles)
That, and I don't like the idea that the fate of the universe depends on whether or not enough black holes are created to constantly redistribute the amount of energy in the universe. This would mean that there is a 'critical black hole density', as of course, white dwarves don't have any antientropic process. Some sense of aesthetics prevents me from believing that the fate of the universe is affected by something as random (and affectable!) as star formation. This is just my indication that there are no real antientropic processes, and black holes do not 'consume' information.
I'm not sure I buy the reasoning on bounded dimensions including time: time is on a different footing than space altogether, and it's fully believable that we live in a universe with three bounded dimensions and one unbounded - I honestly wish I understood more about mixed-signature geometries, because it may be that you could determine this answer from something other than the energy content of the universe.
That's just me, however - I don't like the universe having *any* input parameters at all: after all, energy itself is just a manifestation of the fact that the universe is time-translation symmetric, and if the concept of "time" isn't well defined outside the universe, then the concept of "energy" isn't well defined outside the universe either. Therefore, the fate of our universe must be determinable from some basic property of the physics of the universe in which we live.
I digress: all I meant to point out is that while aesthetics may be a guide in this case, since 3+1 dimensional spacetime has some 'quirky' properties, it may be that 4 bounded dimensions may not be possible considering the symmetries that the 3+1 dim spacetime has to obey.
It was a psuedo-mistake. It was thrown in because it *can* exist.
Historically it was set to zero because it doesn't look pretty in the equations, but there's no reason it should be zero, and in fact, current astronomical observations say that it's probably not zero.
Of course, I'll state my opinion flat out and say that I think the astronomical observations are flawed in the first place, for many fundamental reasons (especially the supernova observations. Trust me. Supernovae are anything *but* reliable observations). I've seen too much duplicity in reporting of astronomical data (see also the Hubble Constant war) to believe anything 'surprising' like this.
It's possible, but the researchers IMHO are trusting their own data too much to suggest something like this. Start from the assumption that the cosmological constant is zero, then try to see if there's anything in your data that would explain the problem OTHER than a cosmological constant. If you can't find anything, you're a bad scientist - talk to some other ones and get some ideas. Check those ideas, check your instruments, run the experiment again. Repeat. Only when you've exhausted everything you can think of can you say "well... we might want to consider a cosmological constant."
The "bad scientist" comment up there implied that a good scientist can always come up with a problem in his/her experiment that will cause a systematic error, not that a cosmological constant is inherently bad.
I don't know. IMHO they haven't done enough checking yet to convince me. Supernova data doesn't convince me - they're way too variable, and they are NOT standard candles, regardless of what anyone tells you.
Slashdot Mirror
"low bandwidth, high quality, low processing power" is completely impossible. Bandwidth+quality equates into space, and processing power equates into time. There's always going to be a trade off between time and space.
Actually, MACHOs are a specific thing, as MACHO is an acronym for MAssive Compact Halo Object. This implies that it has significant mass, is quite compact, and located in the halo of a galaxy. This says quite a bit more than "rocks".
No, it is true that QED is still the most accurately verified physical theory. The binary pulsar set doesn't prove GR to 14 orders of magnitude. It proves -one- prediction from GR to 14 orders of magnitude.
.0128%). GR doesn't agree to 14 decimal places to the perihelion shift of Mercury, for instance.
Note that this is *stupid* to say as well, because we don't even have a good measurement of G to more than a few significant digits, I believe (the only one I can see is the freq-shift method from '82, and that was
To be honest, you're splitting hairs here - yes, the Hulse-Taylor Pulsar measurement was one of the most accurate verifications of a physical theory known to date, and that's very impressive. But, that doesn't validate GR to 14 decimal places in every prediction it makes.
QED is valid to 10 decimal places in something like 12 or 14 different independent experiments. That's something that GR can't even come close to yet.
There are two problems that you need to remember:
One is, if your theory is REALLY good, you can show why something is from very basic principles. Thus, you don't have any precepts to start on other than a few basic ones. For instance, you can say "particles have spin?" and someone may say "yes, but at some time, spin might not have existed." If your theory is extremely good, you can say what would happen if spin didn't exist. In actuality, relativity already says that - if spin didn't exist at some point in time, then relativity wouldn't have existed - that is, spacetime wouldn't have a 3+1 signature.
Conversely, if we find evidence of spin, that implies that spacetime has (at least) a 3+1 signature, or at least has some symmetry which posesses 2 Casimir invariants.
Physics isn't generating 'laws' that have to be 'obeyed'. We're saying "the universe IS this way, that IMPLIES this", we check it against experiment, and *that* can't change. We know, for instance, that conservation of energy holds because the universe is time-symmetric. If we abandon conservation of energy, we have to assume that the universe is NOT time-symmetric, which disagrees with tons upon tons of experiments (including ones which measure all the way back to 300,000 years after the big bang, so we at least have to assume that conservation of energy has held for ~10 billion years).
This is why astrophysics is important - it tells us "how constant are the 'silly little laws' we come up with?" and trust me, based on what we've seen so far in astrophysics, my God, they're constant.
(Just as an example - it was once thought that gravity's strength changes over time - with the density of the Universe. This is Brans-Dicke theory. We now know that Brans-Dicke theory, if it is correct, contributes very VERY negligibly to gravity's strength. That is, if gravity *has* changed over time, it hasn't changed *much*.)
What??
:)
OK, first simple correction, actually, changing the speed of light changes the *distance* unit, not the time unit. We define time as cycles of a cesium atom, so the correct definition is that one *meter* is the distance light travels in some fraction of a second, per SI definition.
QED is the most well tested consistent theory that physics has ever seen. GR is not NEARLY as well tested as QED is. Blandly stating that QED has only been checked to 10 decimal places is crazy - QED is consistent to 10 decimal places with about 12 (if memory serves) completely different experiments. That's far more impressive than any test GR has undergone.
Alpha is the most well-known physical constant in physics right now, and suggesting that it changes, while it is possible, would not be in the least bit consistent with astrophysical findings. QED is more than consistent over well over several decades of orders of magnitude. GR doesn't win there at all.
QED is very simple, with absolutely *no* ad-hoc rules. The ad-hoc rules only come into play when
a) a physicist asks a meaningless question (What is the sound of one electron clapping?)
b) other forces come into play. You're talking about QED - that is, quantum *electrodynamics* - electromagnetism only, other particles/forces not invited! (Yes, this includes the weak force - otherwise QED would be quantum electroweakdynamics).
b) is to be expected, as a general unified theory doesn't exist yet, and a) is a simple extension of physicists who live in a macroscopic world trying to assign macroscopic ideas to a microscopic system (i.e. the 'location' of an electron). Any of Hund's rules could be seen to be ad-hoc as well, but a bit more theory and it all makes sense.
Now, if you mean the *Standard Model* is filled with ad-hoc rules, you're right. Neutrinos are all left handed... kindof. That sort of thing. That's correct. But QED is quite a solid theory.
GR is also anything but incredibly simple. It's simple only in the limit where you can take the interaction between two objects to be significantly greater than the Planck length, but anything smaller than that, and GR isn't so simple anymore. Simple reasoning: GR is continuous, QED is quantized. We can pull QED out from the quantized limit back to good old electrodynamics easily, but GR isn't nearly as lucky.
And, yes, I am a physicist as well, but I don't work in units where c is one.
I never said I agreed with current practices. :)
To be honest, though, prescribing HGH is seriously different than modifiying one's genes to produce more growth hormone. The difference? It's a personal choice, and it doesn't affect one's children. Screwing around with genes is *permanent*, that's why you need to be careful with it. This is why Britain bans alterations of one's germline (DNA passed to children). I don't necessarily agree with the ban, but I can understand it.
There's a clear and simple difference between "natural" variation and "unnatural" variation, and we really need to codify and define those differences.
Genetic modification really should *only* be done in a case where there is a clear and obvious defect in the DNA of a subject. For instance, modifying one gene in an embryo with sickle-cell anemia is perfectly fine. We know what the heterogenous phenotype does, we know what the homogenous recessive does. You don't tweak your DNA. It's not safe, and there's no going back.
Re: learning ability - there is a significant difference between what society considers "genius" and learning ability, believe it or not! Strangely enough, many people who are not that "bright" - that is, they don't learn quickly - can end up making the largest difference in science and engineering, simply because they take longer to understand something, and don't gloss over it like people who learn faster.
What I'm trying to say is that upping someone's IQ doesn't mean they're going to discover how to travel faster than light. We don't *know* what allows people to make those breakthroughs in science and engineering, and it could be that there *is* no 'know', and it has more to do with who the person is and the life they live.
Assuming that upping people's IQ, and making humans immune to disease, and giving everyone 20/20 eyesight will produce a world exactly like our own, only better, is naive and short-sighted. Diversity only *increases* the rate at which humans progress, not *decreases*.
That's not even the real problem, and I find it frightening that no one's touched on the real problem yet.
:) If you eliminate the "weak" humans, you may get a rather bad side effect of a complacent and improvement-focused society. Innovation comes from necessity, and perfect (or somewhat perfect) beings don't need anything. If you don't need to fight diseases, you won't get the random benefits that come with the research. Trust me - getting pure science funded is hard enough!
The real problem is that people "think" they know what's best for certain people - i.e., they 'think' they know that it's best to have 20/20 eyesight, or better than 20/20 eyesight, or immunity against all disease, or massive high IQs.
That's not true. That's not best at all, because society, science, and technology don't work that way.
Technology works in two ways - improvement and innovation. Improvement we understand - you take an existing design and tweak the hell out of it. See also microprocessors, and just about everything else. Now, here's the kicker - nothing that radically changes our lives comes from improvement. Yah. That's a harsh criticism, I know, but it's real, or at least close enough to real to be true.
Now look at innovation, and what causes it. Intelligence doesn't. That's the other harsh criticism, but it's also true. In fact, it's tough to say what DOES cause it. It just happens.
What does all this have to do with the current topic? If you've ever seen ST:TNG's Masterpiece Society, you know where I'm going, but don't discount me quite yet.
You don't "improve" on kids, because genetics don't do diddly when it comes to making kids 'smart', if you think 'smart' means they'll win a Nobel prize someday. What makes kids 'smart' is an environment that constantly fosters growth and curiosity (curiosity being the big one right there) and THAT you're not going to fix with any combination of base pairs. Twins are the perfect example here, as just because one twin does something groundbreaking doesn't mean the other will.
You're not trying to make "arbitrary" categories. They're not arbitrary, I can define them rather quickly - anything that causes a human to die prematurely (normal lifespan) and (this is the tough one) anything that hampers a person's ability to live his or her life as anyone else. This DOES exclude futzing with IQ, messing with strength, or slightly abnormal eyesight, or anything like that. There's no reason to do anything like that, because there's no problem. The slippery slope is deciding what hampers a person's ability to live. I agree with that. However, why in God's name would you want a) immunity to 'diseases' (assuming that was even POSSIBLE, which it isn't) or b) everyone to have better than 20/20 eyesight? Getting sick is necessary - you don't want immunity from disease, you want to be able to cure them all (and to keep getting better at curing them). And the eyesight thing is just pointless. After all, not all blind people want sight.
So, what am I saying? OK. I agree that we should try to fix defective genes, because we know what they do. That's simple enough - if someone's going to die, or need constant medical supplement, you need to fix that. But you need to strictly, strictly avoid trying to fix something that isn't broken. The idea of genetic engineering is to throw more humans into the potluck called life, not to try to tip the pot over.
LinuxBIOS requires a Disk-On-Chip. I don't think it's possible without it. In addition, I don't think a Disk-On-Chip solution is possible without LinuxBIOS, as the only place you can typically install Flash is in the BIOS slot, and without a BIOS, well, you have to have LinuxBIOS.
Ah... RS232 ports.
I can't believe people are abandoning support for RS-232 serial ports. I can't connect two computers using three wires and two USB ports. They're useless.
I fully believe if we ever make contact with an alien race, we will connect our computers via RS-232.
I'm really confused. I'm hoping not to get flamed by this, but honestly, why was the portion of the law which said "free software doesn't need a warranty" changed to "Open Source software doesn't need a warranty"? There's plenty of "free as in beer" software out there that for some reason, they didn't (or couldn't) release the source code. Why should they have to provide a warranty? They're releasing it simply because they think it would be of use to the community - they might not have the time or money to support it.
Or did they just change it to "free as in beer" and "free as in speech" are both exempt now?
Electrons don't have width. They are fundamental point particles (to our best knowledge).
Tunneling will become an issue roughly when you're within a couple of angstroms of the surface (~ radius of a hydrogen atom or so).
It's highly unlikely that electron tunneling will ever be a problem - if you ever build a chip that electron tunneling might be a concern on, I guarantee you're going to have defects in that chip that short two of the wires, rather than needing to worry about electron tunneling. Without major overhauls in process control, this just won't happen.
On topic: AMD *has* had massive screwups with their processors - it just isn't advertised as it doesn't affect most people. Except me, of course - I have an old AMD-K6 200 with the bug that causes it to be unstable with >32MB of RAM. Happy day.
Though it should be noted that AMD did offer to replace these processors- I just didn't know about it till I got Linux, and it told me.
Wow. That link is by far the worst example of idiot math I've ever seen in my life. Has the author ever *read* a relativity textbook?
What is claimed in the link:
Motion is impossible because a component of the "4-velocity" created by "dx/dt" is a "unitless" number.
OK, so why is this stupid?
The position of a particle, x, is defined as
x = (ct, x, y, z) in some reference frame - it is NOT (t,x,y,z): that's *stupid*: space is space, time is time. But when you consider that there is a common velocity throughout all space and reference frames - the speed of light in vacuum - then 'time' has to be linked to 'space' somehow - and it's linked through the speed of light in vacuum, c. You can work this out on a sheet of paper using the Pythagorean theorem.
OK. So even the 'simple' 4-velocity dx/dt now looks like dx/dt = (c, dx/dt, dy/dt, dz/dt). Nothing's unitless - everything has dimensions of distance/time. Thus, we have already disproven the statement in the above link. So, we can stop here.
Motion in spacetime is simple - it works exactly as it does in Euclidean space/time. Want to create motion? Just shift to a reference frame that is moving at a different 3-velocity using Lorentz transformations. Boom. You've got motion in spacetime - you can then follow the object's position as it moves through spacetime.
This is a very weak interpretation of the EPR experiment: there is no reason to believe that "physics is fundamentally nonlocal" in the sense that you're talking about - especially when it comes to the interpretation that it will produce "instant" anything.
The hardest part of quantum entanglement to understand is the fact that Nature is both fundamentally local and nonlocal at the same time. Yes. You heard me. That's exactly what I meant.
Interactions are local: a particle at point B ten light years away from a particle at point A can only interact with an on-mass-shell particle intermediating the two. That is, for an electron which emits a photon which is reabsorbed by a particle ten light years away, the photon is on-shell - or VERY nearly on-shell: q^2 = 0. They can't exchange an off-mass-shell particle, because it would need to live too long. What does this mean? It means that space essentially determines the momentum scale of an interaction - i.e., interactions are fundamentally *local*.
Particles, however, are fundamentally *nonlocal*. As D. Griffiths might have put it in his wonderful QM text, "Even God doesn't know the exact location of an electron" - because the concept of an "exact location of an electron" doesn't exist. Yes. That's right. It's not an inherent limitation in humans, or the Universe, or God in this case. It's the way electrons are. If you asked God what the exact location of an electron was, he'd look at you as if you were stupid, because you'd be asking a complete nonsense question. Asking "where is an electron?" is nonsense. The concept of "where" doesn't exist quite as firmly for an electron as we think it does for us.
So, how do you reconcile the concept of the EPR experiment? It's because the concept of the "location of the photon" is not real. The photon is located along the entire spread of its worldline, as is its pair photon with opposite polarization - or at least, the photon's polarization is (talking about the "location of a photon" is, as I said, meaningless). Same for an electron/positron pair in the classic EPR experiment. When you measure the polarization (or spin) of the photon (electron), you're measuring the polarization of one part of the *combined pair*.
Of course, once you do that, you localize each portion of the state: interactions are fundamentally local, after all.
You said it yourself. All that exists are particles and their interactions. Particles don't provide the structure of spacetime - their interactions do. You can't have instantaneous changes in position because that would suddenly cause all the interactions that those particles were undergoing to become nonlocal.
The only way you can have "instantaneous changes in position" is if you physically make the space close - i.e., a wormhole - then all the interactions stay local. They're then in a multiply connected topology, but there's nothing wrong with that. However, good luck actually predicting the dynamics of creating a wormhole. We don't have math for 'breaking' a continous object and then 'reforming' it again (see also waves crashing). Might be possible, might not.
But in any case, "instant" communication is insane without invoking the concept of a multiply connected universe.
See my parallel post. Build a machine yourself, or try to find a different machine like this, but don't buy this one. PC Chips motherboards are horribly unreliable and just all around trash.
Don't bother buying this unless you plan on throwing the rest of your money away.
Aah! PC Chips! Aah!
p s/ usage.html
Notes: avoid this vendor like the plague. They're well known in the hardware industry as being the absolute worst (and I do mean the worst) motherboard manufacturer in the industry. I have bought or obtained 3 motherboards from this company, and those're the only 3 I'll ever have. 2 never worked in the first place, and the 3rd has serious BIOS problems (which I worked around, but it still can't keep the system clock on power off).
Check out
http://www.stud.fernuni-hagen.de/q3998142/pcchi
You're using "trivial" to mean "identity", or "Minkowski". I'm using it to mean "simple", that is, non-complicated, straightforward.
Granted, bad choice of words, but that's why I specified what I meant by trivial.
Dimensions are only orthogonal if the metric is trivial (i.e., diagonal).
The "metric" as I stated above is a 4-dimensional tensor (matrix, essentially) which (basically) provides the coefficients in the distance measure.
i.e., in 3-space, we have a distance measure of
ds^2 = dx^2 + dy^2 +dz^2
Here, the metric has a 1 in the dx-dx term, a 1 in the dy-dy term, and a 1 in the dz-dz term: in terms of a matrix, this would be just the three-dimensional unit matrix.
General relativity says that the metric is affected by the presence of matter and energy, so therefore, depending on the spacetime configuration, the dimensions may not be orthogonal. Near a black hole, this is actually distinctly not true - there is significant radial/temporal mixing in certain coordinate systems. Granted, you can always define a coordinate system with orthogonal coordinates.
In any case, you were mainly talking about special, rather than general, relativity here. The 4-dimensional metric being talked about is a Minkowski space - time is distinctly separate from any others, because in the Minkowski metric, we have
ds^2 = dx^2 +dy^2 +dz^2 - c^2 dt^2
note that time has a changed sign. We call this 3+1 spacetime.
All special relativity does is define exactly how you transform from one coordinate system to the next - in this case, via Lorentz boosts. Lorentz boosts in one direction have both a spatial boost and a temporal dilation, which is what you are talking about. It doesn't mean the coordinates aren't orthogonal - it just means that when you boost from one frame to a faster-moving frame, both the boost direction and the temporal direction are affected.
Short answer: you answered your question yourself - you said "rate of movement", but above you said "movement" - there's no reason to expect that "moving" is the same as "steady motion" - or, that a simple translation is the same as a velocity shift. In truth, it isn't.
Think about it this way. It's true, time and space are orthogonal. If I do a time translation (i.e., in my coordinate system I redefine t = t + t0) it doesn't affect the x, y, or z coordinates. Likewise for spatial coordinates.
But there's no a priori reason to expect that when you start talking about another frame of reference that is in constant motion with another that it shouldn't affect the other coordinates. After all, you're already mixing things: you have to talk about z = z0 + vt, for instance. Here, instead of the boost simply being z = z0 + vt, there's a Lorentz factor as well.
Hey!
Go fig, this is exactly what all of us reading the NYT's article from last Tuesday are wondering re: "we have demonstrated the existence of a repulsive dark energy via supernovae observations."
What the hell were they thinking making such a bold claim? I definitely agree with you. You never - ever - ever claim something until you have one hell of a mountain of data behind you.
Otherwise you end up looking like an ass, just like P&F, the Weber bar experiment, and California's monopole - all great examples of why physics works best as a peer reviewed process.
I could be wrong, you know. If I am, I'll join you over in California tomorrow using a maglev utilizing monopoles where we can solve their power problems using cold fusion and worry about how we're going to survive in a few days when the black hole at the center of the galaxy finishes consuming all the stars in the known universe. Of course, the cosmological constant will come and fix all of our problems. No tongue in cheek here...
Which is half the reason the physics community thinks P&F are idiots.
One: they didn't have the equipment to detect neutrons. They claimed it because they knew they had to.
Two: Someone right friggin' beside them in the physics department with a running neutron detector at the time when their experiment was running didn't see any excess neutrons.
The smoking gun, IMHO, is the fact that P&F aren't dead. Regardless of what reaction is occurring, you're going to produce high energy reactants that are going to do severe genetic damage. They're not dead - therefore, they didn't produce squat.
Argh. I replied to this before, but Slashdot ate it. What a pain.
I don't agree with your first argument - it's very weak, considering that GR is not a QFT. There's no reason to believe that the vacuum has anything but zero energy, and Mach's principle makes you want to believe that it is zero (Einstein was quite distressed to find out that an empty (Friedmann) universe was a solvable solution of the equations) since in this case you don't have a global matter field to define any of the physical parameters such as mass, etc, and you're essentially defining them in this case via an external field, which is exactly what Mach's principle tries to avoid.
In some sense, you expect the GR limit to have a zero vacuum, since GR should be a 'smoothed over' limit of whatever a QFT of gravity is, if one exists - in some sense, you expect quantum fluctuations to not strongly affect the GR limit (although it very well might). This argument is weak, granted, but GR deals with stress-energy density, not with the gravity of spacetime itself, which is a distinctly quantum process. My gut reaction is still that using vacuum energy to justify a cosmological constant isn't proper, as you're stretching the bounds of where GR is valid.
The second argument is perfectly valid - kindof. The whole idea of "it's going through several phase transitions, so it should be absolutely huge!" is weak, especially with the whole idea of renormalizability. I have little doubt that a final QFT of gravity (again: if there is one) will have an infinite bare cosmological constant.
To be honest, I don't know. My instinct re: the cosmological constant is the same as it is re: dark matter. I don't think we understand gravity at these scales - I really don't. Galaxies look like they have too much mass, galaxy clusters look like they have even more excess mass, all makes me wonder whether or not it's a scaling effect rather than a 'missing mass' effect. With the cosmological constant, it could be the same sort of thing. Again, I could be wrong, but I've always tended towards "the universe is simple" rather than "the universe is bizarre".
Again, I'm not saying that the result isn't real. I'm saying that a good experimentalist can always come up with reasons that the experiment might not have worked.
You're using "invalidate" a little too strongly - I didn't say he would be able to invalidate it - I said he would be able to come up with reasons that would invalidate it. Whether or not any of those reasons pan out to be true is another question.
As for whether or not the presence of a cosmological constant is bizarre, it is bizarre. It's not what we've seen on a smaller scale, though granted our evidence on a smaller scale was much weaker. It's not what was expected - it implies significantly new physics.
As for the final comment, that's just plain wrong - flat out. The flaws in an experiment don't widen error bars - error bars come mainly from statistical considerations and uncertainties in known quantities. They provide a measure of precision, not a measure of accuracy. Going back to the cosmic ray example, for instance, those experiments were way off - but they had great precision. Their error bars were extremely tiny - it just happened that their experiments weren't measuring the right thing, though they didn't know it right at the time (they guessed it afterwards). Depending on the flaw in the experiment, it could be fatal - there are plenty, honestly plenty of those.
Considering the astro data, I know one group was using SN 1a's, which, when you look at the data, are not wonderfully consistent. In fact, there are several astronomers who are beginning to say we don't really know what SN 1a's are (conventional knowledge says that they're white dwarves that exceeded the Chandra limit). Several possibilities jump to mind, including evolutionary concerns and not understanding the physics quite right. These can all be checked, and in the few papers I've read, I haven't seen enough checking to convince me. Again, that could be just me - I'm notoriously hard to convince.
So maybe what I am suggesting is that the teams actually look and see what would have to be true in order for lambda=0 to be within error bounds. Is this bad science, since you're shooting for a specific value? Not really - it's a sanity check. You're just making sure that what you're saying is *guaranteedly* true, and if you have a detractor - someone who insists lambda=0, for instance - you can tell them "well, if lambda=0, then such and such would have to be true."
Weber's measurement of gravitational waves wasn't within two sigma of zero either. I personally don't think that the mass of a few thousand stars is being turned into gravitational waves at the center of the galaxy, though.
I'm beginning to think that this is simple miscommunication, but...
Yes. I am saying that a sufficiently good experimentalist can always invalidate his own experiment (at least initially), because a good experimentalist knows the weak points and what can be improved. If you don't, you're lying to yourself. A good experimentalist, faced with a result that is way the hell away from expectations, will immediately go back to the experiment and stare at it for hours and come up with a dozen reasons of what might've gone wrong. Then, after all of those have been checked, he'll go to colleagues and ask for assistance. Then, after THEY'VE checked, and confirmed that's what's going on, then they might publish a quiet paper (or more likely, give a talk at a conference) to see if anyone can come up with an intelligent answer that they've missed. Then they'll go to press. That's what I'm talking about. If you can't do that, don't bother going into the field, as you'll end up ruining your reputation. Monopoles in California (it was California, right?) and the Weber bar experiment. Both classic examples of "what the hell??" experiments that should guaranteedly have been checked more thoroughly before going to press.
I think you're talking about an experimentalist in the last stage of the game, where they've run out of every answer other than the "new physics" answer. But still, at least some of those questions will be unanswerable without a new experiment (or should be. Maybe it was a perfectly designed experiment. But every experiment I've seen always has compromises inside it) and that's what I mean.
And no, I'm *definitely* not suggesting that every repeatedly tested experimental effect can be explained away. I'm suggesting that any questionable result in an experiment can be explained away right after performing the experiment. Now, if the results stand after testing as many of the limitations of the experiment as you can think of, then it's real. But no experimentalist in his right mind would ever believe a bizarre result right away.
Let me put it another way. I'm working on an experiment right now that is designed to look at high energy cosmic rays. We have a guess at what their flux should be. If it's orders of magnitude above that, I can immediately give a dozen things to check. Without hesitation - those are mainly instrument failure things, however. If everything seems to be working, I'll go out and check things myself manually. And if everything still seems to be working, I'll run another experiment to check to see if I can confirm my results. Then, if everything's still wacko, I'll ask colleagues for help.
I'm confused, actually, as you seem to be supporting my point - you admit that a good experimentalist will be able to think of more problems with the experiment. That's what I'm trying to say - that a good experimentalist can explain a bizarre result without automatically resorting to new physics, and then in the same breath suggest an experiment to check that problem. His explanation might be totally wrong - maybe the new physics is there - but he'll always be able to come up with something that should be tested first. Compare this to the amount of time it took experimentalists to believe the Solar Neutrino Problem. It took years before anyone believed that, and experimenters were always saying "maybe there's a problem, but we need more statistics" (the cheapest out, but still an out). This is taking far less time - maybe a year - and I just don't buy it.
As for the semantics argument, that's my personal preference, because repetition is what makes things true in people's heads, not truth - and even scientists fall prey to this. You hear something over and over, and it becomes true. If you hear "there is now significant evidence for a cosmological constant", you begin to believe there's a cosmological constant. If you hear "there is now significant evidence suggesting that our understanding of the expansion of the universe is incorrect" you begin to believe that there's a problem in our current understanding.
It's not silly to explain it away - if the explanation is testable, then it's a valid concern. If you're a good experimentalist, you can *always* come up with a better explanation than "bad physics" - especially because you know the portions of your research that were hacks - and there are *ALWAYS* hacks. :) So if you can't find a problem with your experiment that might explain something, honestly, you're fooling yourself. It might be that all of the explanations you can come up with are crap - I'm not suggesting that any experimental effect can be explained away - I'm just saying any good experimentalist can come up with problems with their own experiment, even if they're not real.
Anyway, take something from my field: in the 80s and 90s, a bunch of experiments all seemed to confirm that the positron fraction in cosmic rays increased at high energies. This made no sense - and fundamentally you don't want to believe it at all. But they all confirmed it, until the next class of experiments came along and showed "oh, wait, you didn't have good enough rejection."
The fact is that in a good experiment, they should've immediately guessed "um, we might not have good enough rejection" and in fact, some of them did suggest that, and that's what led to the better experiments. It might've been that what they saw was real, and their concerns were baseless, but they came up with the concerns, which is the important part.
I agree that the fact that several groups got consistent answers is suggestive, but far space astrophysics relies on far too many assumptions to suggest redefining physics on a small scale until you get a huge swath of data to back it up. Everyone nowadays seems to be hinting in every talk and paper that I read that "evidence is mounting for a cosmological constant": no. Evidence is mounting for a systematic problem in our data regarding the expansion of the universe. The fact that it MAY be explained by a cosmological constant is unimportant. The cosmological constant is a 'fudge factor' in these cases: you can't disprove it because you can fit it to the data. The fact that you can fit it to all the data just says that the experiments are all measuring the same thing precisely - not necessarily accurately.
You're assuming that there exist no anti-entropic processes, which, while likely, may be not true, thanks to Hawking radiation. Not my belief, though, because I don't belief that one quantum process in the presence of a unique macroscopic object can fundamentally change the way the universe works. (Anti-entropic meaning they destroy information, which means they lower entropy, breaking the Second Law. This may be possible. Imagine a black hole sweeping through a cloud of lowest-energy state electrons and photons, and then in a large amount of time (10^100 yrs) turning those lowest-energy state electrons into a massive burst of high energy particles)
That, and I don't like the idea that the fate of the universe depends on whether or not enough black holes are created to constantly redistribute the amount of energy in the universe. This would mean that there is a 'critical black hole density', as of course, white dwarves don't have any antientropic process. Some sense of aesthetics prevents me from believing that the fate of the universe is affected by something as random (and affectable!) as star formation. This is just my indication that there are no real antientropic processes, and black holes do not 'consume' information.
I'm not sure I buy the reasoning on bounded dimensions including time: time is on a different footing than space altogether, and it's fully believable that we live in a universe with three bounded dimensions and one unbounded - I honestly wish I understood more about mixed-signature geometries, because it may be that you could determine this answer from something other than the energy content of the universe.
That's just me, however - I don't like the universe having *any* input parameters at all: after all, energy itself is just a manifestation of the fact that the universe is time-translation symmetric, and if the concept of "time" isn't well defined outside the universe, then the concept of "energy" isn't well defined outside the universe either. Therefore, the fate of our universe must be determinable from some basic property of the physics of the universe in which we live.
I digress: all I meant to point out is that while aesthetics may be a guide in this case, since 3+1 dimensional spacetime has some 'quirky' properties, it may be that 4 bounded dimensions may not be possible considering the symmetries that the 3+1 dim spacetime has to obey.
It was a psuedo-mistake. It was thrown in because it *can* exist.
Historically it was set to zero because it doesn't look pretty in the equations, but there's no reason it should be zero, and in fact, current astronomical observations say that it's probably not zero.
Of course, I'll state my opinion flat out and say that I think the astronomical observations are flawed in the first place, for many fundamental reasons (especially the supernova observations. Trust me. Supernovae are anything *but* reliable observations). I've seen too much duplicity in reporting of astronomical data (see also the Hubble Constant war) to believe anything 'surprising' like this.
It's possible, but the researchers IMHO are trusting their own data too much to suggest something like this. Start from the assumption that the cosmological constant is zero, then try to see if there's anything in your data that would explain the problem OTHER than a cosmological constant. If you can't find anything, you're a bad scientist - talk to some other ones and get some ideas. Check those ideas, check your instruments, run the experiment again. Repeat. Only when you've exhausted everything you can think of can you say "well... we might want to consider a cosmological constant."
The "bad scientist" comment up there implied that a good scientist can always come up with a problem in his/her experiment that will cause a systematic error, not that a cosmological constant is inherently bad.
I don't know. IMHO they haven't done enough checking yet to convince me. Supernova data doesn't convince me - they're way too variable, and they are NOT standard candles, regardless of what anyone tells you.