Apparently heretics are, on the aggregate, lazier than I suspected. I had the unusual pleasure of reading a blog post for completely independent reasons and coming across my own name — Ethan Zuckerman was reporting on a talk given by gerontologist Aubrey de Grey at the recent BIL Conference, in which he quotes my line from the Edge World Question Center that “Being a heretic is hard work.” (His other quote was from Gandhi.) It hadn’t occurred to me that such a sentiment was sufficiently unique to deserve being quoted, but as far as Google knows nobody else has pointed this out before. (While we’re at it, did nobody appreciate my previous Google joke?)
So I re-read my own World Question Center entry, and (to nobody’s surprise) I thought it was great. I’m my own most sympathetic audience. But in my post here about the WQC, I linked to the entry but didn’t reprint it in its entirely. Which I will hereby do now, because I’m a busy guy and you are busy blog readers who don’t always have the time to click on a link. Being a blogger is hard work.
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Growing up as a young proto-scientist, I was always strongly anti-establishmentarian, looking forward to overthrowing the System as our generation’s new Galileo. Now I spend a substantial fraction of my time explaining and defending the status quo to outsiders. It’s very depressing.
As an undergraduate astronomy major I was involved in a novel and exciting test of Einstein’s general relativity — measuring the precession of orbits, just like Mercury in the Solar System, but using massive eclipsing binary stars. What made it truly exciting was that the data disagreed with the theory! (Which they still do, by the way.) How thrilling is it to have the chance to overthrow Einstein himself? Of course there are more mundane explanations — the stars are tilted, or there is an invisible companion star perturbing their orbits, and these hypotheses were duly considered. But I wasn’t very patient with such boring possibilities — it was obvious to me that we had dealt a crushing blow to a cornerstone of modern physics, and the Establishment was just too hidebound to admit it.
Now I know better. Physicists who are experts in the field tend to be skeptical of experimental claims that contradict general relativity, not because they are hopelessly encumbered by tradition, but because Einstein’s theory has passed a startlingly diverse array of experimental tests. Indeed, it turns out to be almost impossible to change general relativity in a way that would be important for those binary stars, but which would not have already shown up in the Solar System. Experiments and theories don’t exist in isolation — they form a tightly connected web, in which changes to any one piece tend to reverberate through various others.
So now I find myself cast as a defender of scientific orthodoxy — from classics like relativity and natural selection, to modern wrinkles like dark matter and dark energy. In science, no orthodoxy is sacred, or above question — there should always be a healthy exploration of alternatives, and I have always enjoyed inventing new theories of gravity or cosmology, keeping in mind the variety of evidence in favor of the standard picture. But there is also an unhealthy brand of skepticism, proceeding from ignorance rather than expertise, which insists that any consensus must flow from a reluctance to face up to the truth, rather than an appreciation of the evidence. It’s that kind of skepticism that keeps showing up in my email. Unsolicited.
Heresy is more romantic than orthodoxy. Nobody roots for Goliath, as Wilt Chamberlain was fond of saying. But in science, ideas tend to grow into orthodoxy for good reasons. They fit the data better than the alternatives. Many casual heretics can’t be bothered with all the detailed theoretical arguments and experimental tests that support the models they hope to overthrow — they have a feeling about how the universe should work, and are convinced that history will eventually vindicate them, just as it did Galileo.
What they fail to appreciate is that, scientifically speaking, Galileo overthrew the system from within. He understood the reigning orthodoxy of his time better than anyone, so he was better able to see beyond it. Our present theories are not complete, and nobody believes they are the final word on how Nature works. But finding the precise way to make progress, to pinpoint the subtle shift of perspective that will illuminate a new way of looking at the world, will require an intimate familiarity with our current ideas, and a respectful appreciation of the evidence supporting them.
Being a heretic can be fun; but being a successful heretic is mostly hard work.
I have written a book on the physics of starprobes. The book is a way of presenting basic physics up the about the Junior year level within the context of sending spaceprobes to other stars. I discuss Newtonian mechanics within a framework not usually seen in texts, and of course relativity theory. There is a smattering of general relativity, but mostly I work with special relativity to work out issues with the physics of sending a probe to a star within about 25 light years or so.
Lawrence B. Crowell
Dear Lawrence Crowell,
I am of two minds about whether to continue. In view of your last post just read, I don’t expect an answer but I will give this one last try. What I already wrote was:
Thank you for your concern, but I cheer up by laughing at myself!
I notice the term Lambda above. I wonder what your interpretation of Lambda is. More broadly, I wonder about gravitational instability and the feature of a limited amount of mass-energy in the universe. NASA says the universe is supposed to have “released” all its mass-energy within a certain time, which requires a kind of mass-energy “bank” – once all the mass-energy is withdrawn from the bank, there is no more. Yet at the same time there is an entity whose influence increases (dark energy).
However, what if the universe is not the inflation-powered surface of a balloon, but the volume inside the balloon, expanding at a constant rate powered by a positive energy density, creating positive pressure, in turn creating matter which absorbs the local pressure resulting in local non-expansion (perceived as gravitational attraction/spacetime curvature), followed by further expansion (perhaps perceived as accelerated expansion depending on frame), pressure inside the surface, and further matter creation, in cycles? No need for rho crit., Lambda, etc. since the system stabilizes itself by cyclical matter creation.
When you quit laughing, how about a round of “Row, row, row your boat. . . .”?
As much as people might be surprised, there is no conservation of energy law globally in a cosmology. The metric coefficients are time dependent, and this precludes the existence of a Killing vector K_t that defines an isometry and energy conservation law. There is the continuity equation for the momentum-energy tensor
$latex
nabla_mu T^{munu}~=~0,
$
but there is no conservation principle for energy in cosmology!
The expansion of the universe is likened to a baloon blowing up, but of course in three dimensions instead of two. However, ignore the idea that this sphere encloses a higher dimensional region or a ball. The space will just keep expanding, and of course there is no “rubber” that will break. I think Sean posted the Ned Wright’s cosmology website. There is a lot of good stuff there which can help anyone understand some of this stuff.
Lawrence B. Crowell
Thank you Lawrence Crowell,
I have been to Ned Wright’s tutorial several times over the years, but I find the assumption not only there but also generally (running the film backwards) is that the universe began as an extreme density region. Whatever the inferred history prior to the CMB, all that is “known” is that it is emitted from a hydrogen plasma at 3000 K (correct?). How it got to be that way is what I question. In other words it could be either cooling down or heating up. There seems to be no consideration of a heating up scenario. I think this is for reasons of the historical growth of physics, e.g. bodies of matter, conservation of mass-energy.
Re the balloon analogy, I dimly understand the mathematicians have a special sense of 2D and 3D, sphere and ball. It is difficult to ignore the interior of the ball, I wonder how the mathematicians do it. But the key to my idea is in your sentence, “The space will just keep expanding, and of course there is no “rubber” that will break.” If the initial condition is spatial expansion, the universal expansion rate will be dictated at the moment of expansion. The “spatial field” will expand at its full potential, which it cannot alter without breaking its own natural law (or our understanding of the constancy of natural laws in our frame). The initial condition therefore dictates a constant expansion rate and immediately invokes space and time measurement, including added volume per unit of existing volume of the ball.
The thing is that, after a very short time, for every added unit of constant radial expansion the added volume is less than the natural law (initial condition) requires. That is, each unit of existing volume adds less and less new volume as the ball expands at its limit. In other words, if every ‘point’ within the expanding field replicates the initial condition of the field itself, there is not enough space within the field to absorb the expansion potential – even while the field is expanding at its full potential at its ‘edge’. So although there is no rubber that will break, the initial condition of constant expansion rate produces pressure inside the ball. I am told that rotation is a degree of freedom. So rotation absorbs the pressure. I think it would have to be rotation on the equivalent of three axes in order to absorb pressure from all directions. It also has the effect that space in the rotating region does not expand. If you go by Planck times and Planck lengths and rotation rate of c applied to ~10^23 hertz frequency for protons and ~10^20 hertz frequency for electrons, I calculated something like 10^64 particles would be created in one second. Each non-expanding region forms effectively a zero point for the spatial field, so the working of the natural law restarts from an effective zero radius with each matter particle created. Then the cycle repeats itself, constantly creating new matter just inside the edge of the ball, but I think with larger intervals, so you end up with dense regions of matter and voids. Large enough voids may create pressure and rotation, i.e. dark matter.
Sean,
A Dark Matter thought experiment.
1) Dark Matter was invented to augment the observed motion of
real visible matter, right? right!
2) Dark Matter interacts with real matter via gravitational forces
only, right? right!
3) Dark Matter too interacts with Dark Matter gravitationally
right? right!
4) Therefore Dark Matter must take part in the orbital dynamics
of the system, right? right!
5) The only difference is that Dark Matter cannot be seen, other
wise, it takes part in the gravitational dynamics of the system,
which is purely Newtonian motion, right? right!
Now that we agree, let us do a pure thought experiment.
Let us do an N-Body simulation, where N will be in the billions.
6) All N Bodies will therefore do a Newtonian Samba. Each of the
N Bodies will clearly have rotational motion velocities defined
by Newton’s laws. Therefore only Newton’s Law accounts for
their motions.
7) Now we will use some magic, we will make 90% of the N bodies
invisible, and call them Dark Matter!
8).What do you think would happen to the 10% that are still visible?
9).You guessed! they will keep moving as before and still obey
Newtonian Law’s with no velocity discrepancies.
10)Moral of the story is, Dark Matter don’t matter.
11)There must be another way! I have a hypothesis for another
alternative to Dark Matter at cosmicdarkmatter.com.
/Tissa Perera
Hmm, that sounds very plausible, unless there were forces other than gravity that acted on ordinary matter. I wonder what those could be?
> Let us do an N-Body simulation, where N will be in the billions.
OK, now let’s do one with N in the billions of equal billionth parts of the mass of the combined Earth-Moon system.
> 7) Now we will use some magic, we will make 90% of the N bodies
> invisible, and call them Dark Matter!
> 8).What do you think would happen to the 10% that are still visible?
> 9).You guessed! they will keep moving as before and still obey
> Newtonian Law’s with no velocity discrepancies.
This time let the magic be to make the Earth invisible and call it Dark Matter. Then an alien observer on Mars, say, observing the moon through a telescope for several months would see it perform bizarre cyclic motions superimposed on its orbit of the Sun.
As this motion would not certainly not be Newtonian, they would be able to correctly predict the large invisible mass sufficient to cause the combined centre of mass of that and the Moon to orbit along the approved Newtonian ellipse.
It’s the same with stellar rotation rates – The dark mass is needed to restore Newtonian sanity to observations in conflict with it when only visible mass is taken into account. Somehow you’ve put the cart before the horse.
(me again sorry)
Tissa (#55), to emphasise the point implied in my final paragraph, stars in a galaxy do *not* orbit their galaxy as one would predict from Newton’s laws assuming theirs is the only mass in the galaxy. So your argument is based on a false premise, specifically your point 9.
Read the Wikipedia article http://en.wikipedia.org/wiki/Galaxy_rotation_problem
I’m not entirely clear how cosmologists exclude the possibility of enough non-stellar material to account for observed orbits. But this stuff, especially gas and ice and dust, absorbs and reflects radiation. So presumably the amount present can be deduced from spectrographic data and the amount infered by this and other means is insufficient for the job.
In any case, dark mass and energy is apparently needed to make up the total amound of mass-energy which the Standard Model predicts must have been formed in the Big Bang. Ordinary matter falls far short of what is required.
In reading the blog, it sadly occurs to me that Sean is less of an iconoclast than he imagines. He still accepts “string theory” which has become an unfortunate choice of orthodoxy these days. “String” has yet to make any testable, falsifiable predictions despite 30 years and hundreds of physicists wasting their time , falling into 10-dimensional Calabi-Yau manifolds 🙂 Far more promising theories ( such as loop quantum gravity ) go underfunded, while grant money still is poured down the toilet on “string”. It is a regrettable situation.
Sean, if you really want to shake things up, join the growing number of scientists who realize “string” is the wrong path to quantum gravity.