Absolutely Relativistic Baloney
Most recent answer: 04/27/2011
Q:
Has there really been a a discovery of the Unification of Electricity and Gravity with Einstein’s E=mc2?? as reported by this site einsteinelectricityDOTcom. This guy says that E=MS2 is not reduced to its core elements and that the C should be acceleration times time. But isn't the speed of light a constant with no acceleration? So my understanding of physics and math says he is wrong.
With the discovery of dark energy and matter I believe he may be right to say gravity is a pushing force not a pulling force, but that is beyond the scope of this question. Thanks to all who reply.
- Eric (age 34)
Ohio, USA
- Eric (age 34)
Ohio, USA
A:
That entire site is pure baloney. "Wrong" is far too kind a word- we're all wrong pretty often. Pauli's phrase, "not even false", comes closer to doing it justice.
And yes, constant energy densities do lead to accelerating expansion. Whether you call that pulling or pushing has no physical significance, so you get to pick the word whose sound you like.
Mike W.
And yes, constant energy densities do lead to accelerating expansion. Whether you call that pulling or pushing has no physical significance, so you get to pick the word whose sound you like.
Mike W.
(published on 04/27/2011)
Follow-Up #1: Was Einstein full of baloney? We think not.
Q:
I've reported this page as baloney, it's on your own site.
http://van.physics.illinois.edu/qa/listing.php?id=17050
On this page, Mike W. has written:
"And yes, constant energy densities do lead to accelerating expansion".
This is deepest baloney, for several reasons. We don't have any actual physics to back it up. The experimental evidence of Perlmutter is undeniable, but it could be a wide range of things causing it. It certainly doesn't have to be an accelerating expansion.
Failure to admit that we don't know what causes it is a failure to be a good scientist. Good scientists admit what we don't know, and so are more in a position to solve the puzzles. Bad scientists fill the gaps in the jigsaw with baloney, so they can derive self-esteem from science seeming to be on top of things. But these people hold progress back - they paper over the cracks, and sweep the best clues under the carpet, by pretending we know more than we do. Many students don't even know what the unsolved mysteries are, because they are not told.
But it's not only the mainstream who do this - cranks also pretend to have solved mysteries when they haven't, they're getting like the mainstream in their old age, and they too are into baloney.
- Ellen Davis (age 37)
Arizona
- Ellen Davis (age 37)
Arizona
A:
We did not, in that particular answer, mean to claim that dark energy is known to be the cause of the accelerating expansion. Since our questioner did, and we did not challenge him on that, I can see how you might think we did too.
What we did claim is that if there is dark energy, i.e. a constant energy density, it would cause an accelerating expansion. That's a direct consequence of the basic equations of General Relativity. It's not speculation. It's been standard physics for almost a century now. Standard physics can sometimes turn out to be wrong, but we don't feel a need to put that universal disclaimer on every statement.
On the other question you raise, whether the the expansion is really accelerating, the evidence is not just "Perlmutter", by which I assume you mean the pattern of redshifts vs. distances of standard candles. There is also the pattern of peaks in the fluctuations in the cosmic microwave background (giving Ωtot~1.0), combined with the pattern of matter clustering (giving Ωmass~0.3 ). These very different lines of evidence agree in pointing toward a narrow range of values for the acceleration parameter.
So the acceleration looks real and dark energy, if present, would cause such an effect. Is it the actual cause? We'll all have to stay tuned for further experimental and theoretical advances.
I'm surprised that you would pick us as a bad example of trying to make things too cut and dried. E.g. here's a quote from one of our earlier cosmology answers ()
"...the explanation of the origin of the cosmological constant is very much an open question. It may not even turn out to be best pictured as a dark energy density but perhaps as some sort of interaction with parallel spaces, etc. The reason that such questions are hard to sort out is that the different stories give essentially the same effects..."
Or you could look at what we have to say about quantum measurement ():
"We absolutely do not understand how this happens.....There are a variety of ideas about it, ranging from crazy to crazier. "
I invite a follow-up. It's not clear you disagree much with what we actually wrote.
Mike W.
What we did claim is that if there is dark energy, i.e. a constant energy density, it would cause an accelerating expansion. That's a direct consequence of the basic equations of General Relativity. It's not speculation. It's been standard physics for almost a century now. Standard physics can sometimes turn out to be wrong, but we don't feel a need to put that universal disclaimer on every statement.
On the other question you raise, whether the the expansion is really accelerating, the evidence is not just "Perlmutter", by which I assume you mean the pattern of redshifts vs. distances of standard candles. There is also the pattern of peaks in the fluctuations in the cosmic microwave background (giving Ωtot~1.0), combined with the pattern of matter clustering (giving Ωmass~0.3 ). These very different lines of evidence agree in pointing toward a narrow range of values for the acceleration parameter.
So the acceleration looks real and dark energy, if present, would cause such an effect. Is it the actual cause? We'll all have to stay tuned for further experimental and theoretical advances.
I'm surprised that you would pick us as a bad example of trying to make things too cut and dried. E.g. here's a quote from one of our earlier cosmology answers ()
"...the explanation of the origin of the cosmological constant is very much an open question. It may not even turn out to be best pictured as a dark energy density but perhaps as some sort of interaction with parallel spaces, etc. The reason that such questions are hard to sort out is that the different stories give essentially the same effects..."
Or you could look at what we have to say about quantum measurement ():
"We absolutely do not understand how this happens.....There are a variety of ideas about it, ranging from crazy to crazier. "
I invite a follow-up. It's not clear you disagree much with what we actually wrote.
Mike W.
(published on 06/10/2011)
Follow-Up #2: Big Bang and dark matter?
Q:
Thanks Mike, for your answer, and for inviting a follow up. Just to avoid confusion because of the title of the original post, I don't think Einstein was full of baloney - I think the evidence for SR is overwhelming, and for GR is very strong.
But I don't think GR covers areas like cosmology much, there's clearly so much more to find out, and it's a disaster to try to make GR cover it all, and try to fill in the gaps in the jigsaw that way. And I think we don't know enough to talk about dark energy at all, we talk as if we knew what it is, but we don't.
And the expansion? There's evidence for and against it, and we still don't know. One group says they know there's an expansion, another group says they know there isn't. personally I think we should admit that we don't yet know - might take 50 years. We know redshifts are caused by quite a list of different things, it's almost unthinkable that there are not more to be added to that list. There are bound to be other effects that cause redshifts, but we're so scared of a gap in the jigsaw like that, that we run away from the evidence that the redshifts we observe are not all from motion. We even assume huge general motion at the edge of our field of vision, instead of saying, "we are measuring some unexplained redshifts, might be this, might be that."
There's a great push to find dark matter - suppose we found it, but the evidence conflicted with big bang theory. Would we take it onboard? Well, in 2002 two Dutch astronomers found HII (neutral hydrogen) in an edge-on spiral, in just the right amount to be dark matter. HII is very hard to observe, it's basically invisible, as DM is meant to be. They found a way to detect it, but their beautiful discovery was ignored, because the implications are in direct conflict with big bang theory. Big bang theory is always kept, and other things are adjusted to fit it. But those "expansion redshifts" could be anything - we just don't know. I'm not assuming there was no big bang, I'm saying we don't yet know. But I'll say one thing - if there was a big bang, it was a lot longer ago than in standard theory, which simply doesn't fit all the facts.
- Ellen Davis (age 37)
Arizona
- Ellen Davis (age 37)
Arizona
A:
Hi Ellen- thanks for the thoughtful follow up. I don't think we have a major philosophical disagreement, but obviously we have a very different evaluation of the web of information supporting the current big bang picture.
The principle piece of information you cite that doesn't fit the current picture is the work indicating that there could be enough molecular hydrogen (HII) in spiral galaxies to account for their missing mass. If that were true, it would make big problems for all the self-consistent fits of other types of data to models in which there's about 5 times as much dark matter as ordinary baryonic matter. I was able to find the original paper (), from 1999. It used data that were near the edge of detectability and required a tough estimate of the ortho/para ratio to back out the mass of the HII. The obvious question then becomes whether follow-up experiments confirmed this somewhat shaky result. On the web site of the first author, I could find no follow up papers and no current discussion of the whole issue. In fact, his list of publications on the dark matter topic seems to leave out the one in question:
So I think it's pretty safe to assume that this work was not confirmed.
You raise the famous issue of what to do when a basic framework is challenged by bits of anomalous data. In most cases, the anomalies turn out to just come from little unforeseen complications in the particular systems studied, or from experimental problems. That was true of many anomalies found for the Newtonian gravitational model of the solar system. Then one of the smaller and most obscure anomalies, the precession of the perihelion of Mercury's orbit, turned out to be a sign that the entire geometry of space and time assumed by Newton was wrong. I don't think there's any good algorithm to say when to take anomalies seriously and when to leave them on the back burner.
Despite that general caveat, I'm really shocked that you find some problem not only with the picture of the acceleration of the cosmic expansion but even with the basic picture of the expansion itself. There is an enormous amount of data of many types that fits together in a sharp, well-tested mathematical framework here.
On a particular issue, you say there's "quite a list" of causes of redshifts. I know of only very basic effects, embedded solidly in the deep structure of GR:
1. recessional velocity
2. cosmological expansion
3. gravitation.
What else is on the list?
On another: there's a group of scientists who say there is no expansion? Seriously? We could use some citations here.
Mike W.
The principle piece of information you cite that doesn't fit the current picture is the work indicating that there could be enough molecular hydrogen (HII) in spiral galaxies to account for their missing mass. If that were true, it would make big problems for all the self-consistent fits of other types of data to models in which there's about 5 times as much dark matter as ordinary baryonic matter. I was able to find the original paper (), from 1999. It used data that were near the edge of detectability and required a tough estimate of the ortho/para ratio to back out the mass of the HII. The obvious question then becomes whether follow-up experiments confirmed this somewhat shaky result. On the web site of the first author, I could find no follow up papers and no current discussion of the whole issue. In fact, his list of publications on the dark matter topic seems to leave out the one in question:
So I think it's pretty safe to assume that this work was not confirmed.
You raise the famous issue of what to do when a basic framework is challenged by bits of anomalous data. In most cases, the anomalies turn out to just come from little unforeseen complications in the particular systems studied, or from experimental problems. That was true of many anomalies found for the Newtonian gravitational model of the solar system. Then one of the smaller and most obscure anomalies, the precession of the perihelion of Mercury's orbit, turned out to be a sign that the entire geometry of space and time assumed by Newton was wrong. I don't think there's any good algorithm to say when to take anomalies seriously and when to leave them on the back burner.
Despite that general caveat, I'm really shocked that you find some problem not only with the picture of the acceleration of the cosmic expansion but even with the basic picture of the expansion itself. There is an enormous amount of data of many types that fits together in a sharp, well-tested mathematical framework here.
On a particular issue, you say there's "quite a list" of causes of redshifts. I know of only very basic effects, embedded solidly in the deep structure of GR:
1. recessional velocity
2. cosmological expansion
3. gravitation.
What else is on the list?
On another: there's a group of scientists who say there is no expansion? Seriously? We could use some citations here.
Mike W.
(published on 06/11/2011)
Follow-Up #3: big bang issues
Q:
Thanks Mike. About big bang theory - When I say there's evidence both ways, I should remind you that we usually only see the evidence one way. A top Cambridge University Professor wrote an article recently about how good scientists who argue against BB theory are not published, so their evidence is not seen. There was a conference of physicists in Portugal a while ago on the "Crisis in cosmology" due to there being so much evidence against BB theory. They were trying to promote dialogue about it, and some were flaky scientists, but some were not. Personally, I think they should be stricter with who they include. But nevertheless, there are strong arguments both ways. Remember, I'm not one of these physicists (many of whom you won't have heard of, for the same reasons). I'm not arguing against BB theory, I'm only saying we don't yet know. This seems absolutely clear - but the mainstream are suppressing the arguments the other way. Some of the arguments the other way are good arguments from good physicists, such as the Dutch astronomer Valentyn, whose work you dismiss as unconfirmed. It was hard to detect DM, but they did. There was no encouragement, and perhaps no money to continue. If someone detected DM in a way that fitted with the current orthodoxy, no doubt they'd have had help and funding to continue, and confirm the discovery. And others, who would not fear for their careers, would look that way as well. Anyway, big bang theory isn't my field, and I don't have time to do the research to quote chapter and verse, which I could do off the top of my head in another field. But will try to dig out the article by the respected Professor, arguing that evidence the other way is being surpressed. That speaks for itself. As for the redshift effects, there are others, such as bremstrallung, which is a very small redshift on light when it collides with matter. It was so small that it was ignored for decades, and left out of all calculations. But it could possibly explain the redshift-distance relation, that is, the further away an object is, the higher its redshift. There's a lot of matter in the way on the light's billion year journey, and it might be colliding with HII for all we know. No doubt you will give arguments why that can't be the case, but I'm only mentioning it as an example. if there was more research done into examples like that, we might find other evidence, and other cosmology theories. You talk about a mathematical framework, but physics is full of equivalence - that is, where the same mathematics describes more than one picture. There is a also a major deficiency in lithium in the observed universe, which doesn't fit with standard BB theory. Various desperate attempts have been made to explain it away. "He's as blind as he can be, just sees what he wants to see" John Lennon. "How many times will a man turn his head, and pretend that he just doesn't see?" Dylan. It's a fair point to make - we simply don't know yet.
- Ellen Davis (age 37)
Arizona
- Ellen Davis (age 37)
Arizona
A:
Ellen- You raise one issue of which I hadn't been aware, the 7Li abundance. That depends strongly on models of nuclear reactions in stars. While one can't rule out the possibility that it could indicate some deeper problem, that's just the sort of anomaly that almost always turns out to be due to particular minor issues, not fundamental difficulties. Lee points out that one of our colleagues has recently suggested () some nuclear reaction channels that would account for what happened to the 7Li. These channels are consistent with current knowledge, but of course would need to be confirmed experimentally.
Yes, for any theory there are other theories that give mathematically indistinguishable results for all current observations. That lesson has been driven home by many historical experiences, including the replacement of a Newton+ether picture of stellar aberration by a relativistic one, and of Newtonian gravity by General Relativity.
I'm not an expert in these areas, but suspect that the Bremsstrahlung picture might run into many problems, e.g. line broadening. More importantly, I trust the consensus among the cosmologists on that issue. This leads directly to your main point, which is more about the philosophy and sociology of science than about specific content. Science requires some sort of balance between trust and doubt. You need the trust because otherwise each person would start over from scratch, instead of building on the efforts of hundreds of thousands of others (including many who were extraordinarily smart) over thousands of years. You need the doubt because otherwise we'd get stuck in some consensus rut, and never find anything very new.
I don't think the cosmologists are the sort of narrow-minded trusting conformists who are especially prone to getting stuck. In my memory, they've gone from assuming that the cosmological constant was zero to believing that it isn't, from a simple picture of a big bang to one that involves an extreme inflationary stage, from assuming that inflation was accurate to wondering whether a radically different cyclic scheme was needed, from working in 4-D to considering important roles for higher dimensions, from not thinking much about quantum issues to mostly adopting a Many Worlds interpretation, from assuming that there were fundamental explanations of the dimensionless parameters to seriously considering anthropic selection on a cosmic landscape, etc. This is not a group that's averse to basic change.
Mike W.
Yes, for any theory there are other theories that give mathematically indistinguishable results for all current observations. That lesson has been driven home by many historical experiences, including the replacement of a Newton+ether picture of stellar aberration by a relativistic one, and of Newtonian gravity by General Relativity.
I'm not an expert in these areas, but suspect that the Bremsstrahlung picture might run into many problems, e.g. line broadening. More importantly, I trust the consensus among the cosmologists on that issue. This leads directly to your main point, which is more about the philosophy and sociology of science than about specific content. Science requires some sort of balance between trust and doubt. You need the trust because otherwise each person would start over from scratch, instead of building on the efforts of hundreds of thousands of others (including many who were extraordinarily smart) over thousands of years. You need the doubt because otherwise we'd get stuck in some consensus rut, and never find anything very new.
I don't think the cosmologists are the sort of narrow-minded trusting conformists who are especially prone to getting stuck. In my memory, they've gone from assuming that the cosmological constant was zero to believing that it isn't, from a simple picture of a big bang to one that involves an extreme inflationary stage, from assuming that inflation was accurate to wondering whether a radically different cyclic scheme was needed, from working in 4-D to considering important roles for higher dimensions, from not thinking much about quantum issues to mostly adopting a Many Worlds interpretation, from assuming that there were fundamental explanations of the dimensionless parameters to seriously considering anthropic selection on a cosmic landscape, etc. This is not a group that's averse to basic change.
Mike W.
(published on 06/12/2011)
Follow-Up #4: cosmological sociology
Q:
Well, some of what you say makes good sense. We can agree to disagree about extent of the 'consensus rut', which as you say, is an issue that goes off into other areas. But do remember that with the kind of selection that constantly takes place, we only see one side of the story. There's a lot less consensus than there appears to be. This is partly about the way physics is funded, but also because of attitudes at places like Cornell, and the arXiv site. As for your next point, the openness to change in big bang theory that you mention would be seen by many as evidence that it is not a falsifiable theory at all, but a loose set of ideas that is constantly fixed up and adjusted when it turns out to be wrong. And in fact, your last paragraph is full of things you quote as showing openness to change, but to me they're almost all fix up measures of one kind or another. The many worlds interpretation of quantum theory, which as you say, was not thought about much for decades, became rapidly more central quite recently when it became clear that WITHOUT a many worlds picture, it's impossible to assume that the laws of physics arose by chance. That's the real reason behind that - not quantum theory at all. Anyway, thanks for the discussion, best wishes Mike.
- Ellen Davis (age 37)
Arizona
- Ellen Davis (age 37)
Arizona
A:
I agree that it's tricky to know when a theory is being refined and made more realistic and when it's being manipulated so much as to become un-falsifiable. My sense is that cosmology still has a very lively interaction between theory and data, and has not turned Ptolemaic. But I can see why you might worry.
I'm surprised that you find the arXiv site to be too much of a gatekeeper. How much looser could they be?
My sharpest disagreement concerns Many Worlds quantum mechanics. The cosmologists did not need it to allow anthropic selection, since that already is allowed by domains in a multiverse geometry. The motivation for MW is very simple. In quantum mechanics, the time dependence of the state is given exactly by:
-ihd|Ψ>/dt=2πH|Ψ> .
That's a linear equation. It obeys superposition exactly. The output state of any interesting input is a superset of what anyone actually observes. If the equation is right, then reality consists of many parallel such observations.
So the idea of MW arose completely independently of those cosmological parameter-choice issues, and the the cosmological issues can be solved without MW. Regardless of what we ultimately find out about this issue (or if we ever find out any more about it at all), the tendency of the cosmologists to be the first group to lean toward an unpopular radical interpretation indicates that they are not overly tied down to conservatism.
At least one other of those changes- starting exploration of the possible role of other dimensions- was driven more by developments in fundamental physics than by any data-fitting needs of the cosmologists.
Thanks for the interesting discussion.
Mike W.
I'm surprised that you find the arXiv site to be too much of a gatekeeper. How much looser could they be?
My sharpest disagreement concerns Many Worlds quantum mechanics. The cosmologists did not need it to allow anthropic selection, since that already is allowed by domains in a multiverse geometry. The motivation for MW is very simple. In quantum mechanics, the time dependence of the state is given exactly by:
-ihd|Ψ>/dt=2πH|Ψ> .
That's a linear equation. It obeys superposition exactly. The output state of any interesting input is a superset of what anyone actually observes. If the equation is right, then reality consists of many parallel such observations.
So the idea of MW arose completely independently of those cosmological parameter-choice issues, and the the cosmological issues can be solved without MW. Regardless of what we ultimately find out about this issue (or if we ever find out any more about it at all), the tendency of the cosmologists to be the first group to lean toward an unpopular radical interpretation indicates that they are not overly tied down to conservatism.
At least one other of those changes- starting exploration of the possible role of other dimensions- was driven more by developments in fundamental physics than by any data-fitting needs of the cosmologists.
Thanks for the interesting discussion.
Mike W.
(published on 06/13/2011)
Follow-Up #5: quantum many worlds
Q:
Well there's a difference between non-conservatism and what John Gribbin referred to as "Desperate remedies". Are you really trying to keep a straight face and say that people would have worked on many worlds theories (which as you say are unpopular and more or less untestable) for 25 years if it wasn't for the apparent coincidences in the laws of physics? That issue is what drove the inclusion of many worlds in a range of theories since the '90s and before. If you didn't know, well take it from me - people wouldn't bother with untestable physics without a very good reason.
You talk as if the many worlds interpretation of quantum theory, suggested by Everett in the 1950s, is the only interpretation. People sometimes talk that way nowadays, but for the reasons given above. In fact it's one of 5 or 6 alternatives, all of which have deep problems that accompany them, which is why there are that many. By far the most likely thing is that the true interpretation is something else again, that we haven't yet thought of. Many worlds is a way of getting out of almost anything. It rather makes science meaningless, because we study OUR world, and look for reasons why it is the way it is. If you just make all of its attributes statistical, you weaken science's role in a major way. It certainly is a desperate remedy, and if science wasn't in a battle with some deeply stupid religious people at present, they'd bother with MW far less. Anyway, sorry we've wandered some way off topic Mike... warm regards to you, and keep up your excellent work on this site.
- Ellen Davis (age 37)
Arizona
- Ellen Davis (age 37)
Arizona
A:
I can agree with this part: "...it's one of 5 or 6 alternatives, all of which have deep problems that accompany them, which is why there are that many. By far the most likely thing is that the true interpretation is something else again, that we haven't yet thought of."
I can't agree that the motivation for the many worlds idea is primarily to solve anthropic issues. Over the years I've often taught a course with a large component on the interpretation of quantum mechanics. The first time, I included MW because the previous instructor had, and it seemed like a good idea just to illustrate how crazy the whole field was. Gradually, the implications of the known unitary time evolution sank in, and after a few years I was having trouble remembering why that interpretation seemed crazy. Occam's razor would say that if you have a simple known time dependence that works perfectly over the domain of experiment, you shouldn't postulate a qualitative change to it unless compelled by data. Of course, once you take that road you expect the simple time dependence to give you the observed probability rule, since you now have no collapse process or other kluges by which you can insert it as a separate hypothesis. That the unitary time evolution is even consistent with, much less predictive of, the correct probabilities is not altogether clear. So that's the real problem with MW, not the intuitive impression that it's crazy. As you say, the other interpretations (with the possible exception of the most popular one, "Shut up and calculate") all have comparably severe problems.
As for whether we can decide between ideas by saying which ones strengthen or weaken science's role, we probably also disagree. Statistical mechanics works beautifully. Maybe nature is the boss of us.
Mike W.
I can't agree that the motivation for the many worlds idea is primarily to solve anthropic issues. Over the years I've often taught a course with a large component on the interpretation of quantum mechanics. The first time, I included MW because the previous instructor had, and it seemed like a good idea just to illustrate how crazy the whole field was. Gradually, the implications of the known unitary time evolution sank in, and after a few years I was having trouble remembering why that interpretation seemed crazy. Occam's razor would say that if you have a simple known time dependence that works perfectly over the domain of experiment, you shouldn't postulate a qualitative change to it unless compelled by data. Of course, once you take that road you expect the simple time dependence to give you the observed probability rule, since you now have no collapse process or other kluges by which you can insert it as a separate hypothesis. That the unitary time evolution is even consistent with, much less predictive of, the correct probabilities is not altogether clear. So that's the real problem with MW, not the intuitive impression that it's crazy. As you say, the other interpretations (with the possible exception of the most popular one, "Shut up and calculate") all have comparably severe problems.
As for whether we can decide between ideas by saying which ones strengthen or weaken science's role, we probably also disagree. Statistical mechanics works beautifully. Maybe nature is the boss of us.
Mike W.
(published on 06/15/2011)
Follow-Up #6: many world statistics
Q:
I just want to clarify two things. I don't have the 'inuitive impression that many worlds is crazy'. I have rational reason to believe it's untestable, and therefore bordering on unscientific. It's not so much that no test can be devised, it's more that no test can be devised with only one interpretation for the results. When you do the test, you can say 'ah! another universe is involved'. But it could always be something else. So scientific method goes out of the window. But also, I used the word 'statistical' in relation to something entirely different from statistical mechanics (nothing wrong with that). It was the idea that all the attributes of our world arose statistically. If they did then science has a lot less explaining to do, if you think about it. It's an idea that seems to get science out of any corner it finds itself in, so people invoke many worlds when they're stuck. But we should agree to disagree, and stop there! Anyway, cheers Mike.
- Ellen Davis (age 37)
Arizona
- Ellen Davis (age 37)
Arizona
A:
We should drop it, but you've provided an excuse to discuss some intriguing issues.
It's unfortunate that the many worlds/one world issue is so difficult to test. That's quite a bit different from saying that the many worlds hypothesis is difficult to test, because it avoids assigning either hypothesis the status of the default value. If one were to look at the one relevant part of the known physics, the unitary time dependence, one would say (with Hawking and many others) that many worlds is the obvious default. That would mean it should be accepted unless some evidence were to develop to the contrary. If one were to go with our intuitive sense of the world, one would say that one world is the default. I incline toward the former view, but think that the problem of the origin of the probabilities is enough to throw the whole question open.
As you know, toy versions of the scientific method were already out the window. Say your intuition said that the world began abruptly 6000 years ago, with various ancient rocks and radioisotopes and incoming light all arranged to look exactly as they would have if the universe were much older. Your intuition really strongly tells you that's right. Then somebody comes along with a theory about a whole bunch of extra years actually having existed, more than 13 billion of them. What test will show if you or they are right? Does Occam say to skip the hypothesis of all those extra years, or to skip the hypothesis of a break in the continuity of the behavior? Intuitions differ.
On statistics: Nobody, so far as I know (with the possible exception of Max Tegmark), is proposing that absolutely any logically consistent laws are realized. The presumption is that there is some unique set but it's deeper than the partial, inconsistent laws we have now. As with all sorts of spontaneous symmetry breaking processes in familiar physics, there would be a collection of more more less stable states possible. They would have a wide variety of partial laws of physics, but still with some constraints. There is some hope that a suitable metric on the density of those laws could be developed, so that a statistical mechanics could be applied to them.
For this program, it's useful that traditional statistical mechanics is now often viewed as applied Bayesian statistics. Prior probabilities of states are supplied by an ensemble,. Partial knowledge of the state then provides a likelihood function. The rest is standard stat mech. The hope is that string landscapes (or something like that) can provide a prior density of states, with anthropic constraints providing the likelihood function. The big problem now is that nobody has a decent way of getting (or maybe even defining) those priors. Nevertheless, Weinberg discussed how to predict the approximate value of the cosmological constant by an informal version of this method in 1987, well before much was known about the actual value.
Mike W.
It's unfortunate that the many worlds/one world issue is so difficult to test. That's quite a bit different from saying that the many worlds hypothesis is difficult to test, because it avoids assigning either hypothesis the status of the default value. If one were to look at the one relevant part of the known physics, the unitary time dependence, one would say (with Hawking and many others) that many worlds is the obvious default. That would mean it should be accepted unless some evidence were to develop to the contrary. If one were to go with our intuitive sense of the world, one would say that one world is the default. I incline toward the former view, but think that the problem of the origin of the probabilities is enough to throw the whole question open.
As you know, toy versions of the scientific method were already out the window. Say your intuition said that the world began abruptly 6000 years ago, with various ancient rocks and radioisotopes and incoming light all arranged to look exactly as they would have if the universe were much older. Your intuition really strongly tells you that's right. Then somebody comes along with a theory about a whole bunch of extra years actually having existed, more than 13 billion of them. What test will show if you or they are right? Does Occam say to skip the hypothesis of all those extra years, or to skip the hypothesis of a break in the continuity of the behavior? Intuitions differ.
On statistics: Nobody, so far as I know (with the possible exception of Max Tegmark), is proposing that absolutely any logically consistent laws are realized. The presumption is that there is some unique set but it's deeper than the partial, inconsistent laws we have now. As with all sorts of spontaneous symmetry breaking processes in familiar physics, there would be a collection of more more less stable states possible. They would have a wide variety of partial laws of physics, but still with some constraints. There is some hope that a suitable metric on the density of those laws could be developed, so that a statistical mechanics could be applied to them.
For this program, it's useful that traditional statistical mechanics is now often viewed as applied Bayesian statistics. Prior probabilities of states are supplied by an ensemble,. Partial knowledge of the state then provides a likelihood function. The rest is standard stat mech. The hope is that string landscapes (or something like that) can provide a prior density of states, with anthropic constraints providing the likelihood function. The big problem now is that nobody has a decent way of getting (or maybe even defining) those priors. Nevertheless, Weinberg discussed how to predict the approximate value of the cosmological constant by an informal version of this method in 1987, well before much was known about the actual value.
Mike W.
(published on 06/17/2011)