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Newton's Second Law, Revisited
eldavojohn writes "Dust off your fundamental physics books, an aspiring astrophysicist by the name of Alex Ignatiev has published a paper that proposes testing special cases of Newton's Second Law on earth's surface. His goal is sort of ambitious. The time he has to test his theory is only 1/1000th of a second, twice each year, in either Greenland or Antarctica. What would he look for? Spontaneous motion. From his interview with PhysOrg: 'If these experiments were to take place, Ignatiev says that scientists would look for what he calls the SHLEM effect. This acronym stands for static high latitude equinox modified inertia and would be noticed in a condition where the forces of the earth's rotation on its axis, and of the orbital force of the earth as it moves around the sun, would be canceled out ... In the end, if Newton's Second Law could be violated, he would be forcing physicists to reevaluate much of what we understand derived from that law — which is quite a bit.'"
Or is it?
Reminds me of what Patrick Moore did:
Stolen from
http://en.wikipedia.org/wiki/Patrick_Moore
Eccentric personality
Due to his long-running television and xylophone playing career, eccentric manner, distinctively rapid speech delivery and in later years his ever-present monocle, Moore is widely-recognised and well-respected in the United Kingdom, even by those with no interest in astronomy. This was used to great advantage for a 1976 April Fool's joke on BBC Radio 2, when Moore announced that at 9.47 am a once-in-a-lifetime astronomical event was going to occur: Pluto would pass behind Jupiter, temporarily causing a gravitational alignment that would reduce the Earth's own gravity. Moore informed listeners that if they could jump at the exact moment that this event occurred, they would experience a temporary floating sensation. The BBC later received hundreds of phone calls from listeners claiming to have felt the sensation.
Moore joined the Flat Earth Society as an ironic joke though many have taken this seriously.
It could be worse, it could be Monday.
Law breakers should be punished to the fullest extent of the physical law.
Yes, it only takes one demonstration to a render invalid a scientific theory. But that does not validate any other theories by doing so, unless they can accurately carry the same predictive weight as the previous theory, plus comply with the improved observations.
A hole in Newtons second theory in any case doesn't mean scientists throw out their physics books, it generally means they add and exception to the theory and work on finding a more unified algorithm to describe the newly revised observations. Here's hoping this somewhat exotic set of observations leads eventually to a stronger set of theories, rather than just more false controversy about 'mavericks' and 'closed minded skeptics' - everyone's a skeptic AND a maverick, closed minded and radical - focusing only on the extremes of that, especially in terms of science sort of ignores the whole point of science, to use biased viewpoints to paint a larger picture.
Ryan Fenton
I think it's odd that MOND's enthusiasts are so eager to push it as an alternative to dark matter, now that we've entered the era of high-precision cosmology. We know a hell of a lot about cosmology that we didn't know ten years ago. We know the age of the universe to two significant figures. We know that the universe is expanding at an increasing rate. We know the spectrum and angular distribution of the cosmic microwave background to high precision. We've found out that neutrinos have mass. I can see how MOND would have some appeal back in 1981, when it was first proposed, but so much has changed in the last 26 years. The evidence has accumulated that we live in a universe that's much stranger than we'd believed. I think that's cool.
Find free books.
"Fall heavy towards the moon, and the moon falls also towards you." -- Nietzsche
Hammer and feather are dropped simultaneously from equal heights (as measured by distance from the center of the moon), separated laterally by a distance substantially less than the moon's diameter. Both hammer and feather experience force from the moon's gravity proportional to their mass, and hence both accelerate at the same rate. Meanwhile, the moon is also accelerating towards the other two objects, but unevenly so: the hammer exerts a greater gravitational pull due to its greater mass. The moon is therefore subject to a torque, causing it to accelerate more rapidly towards the hammer.
The hammer is first to hit the ground.
Anyone who denies this truth is a spatially absolutist lunocentric whose refusal to recognize the validity of hammer/feather mechanics places him wholly beyond the help of Galilean metaphysics. Such hammer/feather rejectionists ought to be banished from planetary space, for their own good and for the good of not only hammers and feathers but all subjugated smaller objects, everywhere, who find themselves victims of this scientifically perpetrated emassculation.
--
a756f345ec354225c08ff1a10a43162a
Currently, there is a discrepancy between the rotations of galaxies, and what newtons law says should happen. If you look at large galaxies, at a bunch of different radii, all the stars orbits are at about a constant orbital velocity, which since there is less force acting on them from gravity, shouldn't happen.
The most common physical explanation of why this happens is that there is a ring of dark matter around the galaxies that is also producing a gravitational force, and that when you add in the force from the dark matter, the equations work out, and you calculate that the orbital velocities should be constant.
However, there are some physicists who don't like the idea of dark matter, and in order to explain how galaxies orbit, introduced a new version of newton's second law. F = m * f(a/a0)*a, where a0 is a new fundamental constant describing a small acceleration level where these new Newtonian dynamics hold. and f(x) is a function that equals x when x > 1. This theory describes the constant angular orbit speed of galaxies without the need for the existence of dark matter, however, the theory has problems when applied to relativistic systems.
What it looks like this new paper proposes to do is find a place on earth where the acceleration from the coriolis effect, the centripital acceleration and the acceleration from the sun will all cancel out, and then create a really small force and see if the modified second law works for a very small absolute acceleration.
If there's anything more important than my ego around, i want it caught and shot now.
Maybe he's wrong, maybe he's not right. But damned if I don't admire a scientist who is willing to destroy a potentially promising career over a tiny hunch. Maybe god will take pity and alter gravity for just such an instance. I think he's getting bored with Iraq.
"In the end, if Newton's Second Law could be violated, he would be forcing physicists to reevaluate much of what we understand derived from that law -- which is quite a bit.'"
In the end, if the second law of thermodynamics [or any other law of physics] could be violated, it would force physicists to reevaluate much of what we understand derived from that law - which is quite a bit. However, given that what we have derived from our laws generally fits with experimental observation (which is why we call them laws), the odds of him disproving Newton's second law with this experiment are about as good as me disproving the second law of thermodynamics by accidentally building a perpetual motion device.
Experiments disproving longstanding laws have happened before. People don't have reason to care about them until afterwards, though.
that Newton's Laws are actually just flawed theories? In that case, sign me up for the new "Intelligent Force" theory. Everything accelerates because something smarter than me decided it would, and there's no point asking questions. No more physics equations for me!
I mean, NSL only applies in the case of slow moving/low acceleration objects because it assumes infinite propagation speed of the force carrier.
If he finds this it will be interesting not because of NSL concerns but because it would be an observation of the finite propagation speed of gravity. A fact that would serve as indirect (or perhaps direct) evidence of gravitational waves.
Think it'd be cool to visit Greenland?
1. be a prof
2. propose theory that must be tested in Greenland
3. profit
Am I missing something, or would this be a hell of a lot easier to do in space? From TFA I gather that he's looking for an instance of no outside force, and, since orbit is essentially free-fall, this would be easily accomplished on the ISS. Granted, I might be missing the point entirely, or I don't get his strange "I've got to do this on the surface of the Earth!" fetish.
Newton's law underwent some serious revisiting in 1905 when a chap called Einstein realised that masses are not constant/absolute but in fact relative, and this is why the modern relativistic notation differs quite a bit from the original F=ma. Now if this new guy is not joking (Russian timezones, April 1st, bit early..etc) then not only is our understanding of momentum going to be radically different, but in fact E=mc2 might have to be revisited as well (must read part 10 of this historical paper by Einstein to understand). That happens to be a very ground breaking idea if it were true, and would change lots of things we supposedly know about fundamental physics.
Done.
So for this thousandth of a second in a remote location at 80 degrees of latitude, is he proposing that we build an entire testing facility to see if an uncharged particle wiggles a little bit for some reason by some mechanism that no one has really figured out?
Are we also to believe that because the mathematical calculations work out such that all first- and second-order gravitational forces are cancelled, if we observe some motion, that motion is a clear violation of Newton's Second Law by assuming that there is zero force on the particle?
Wouldn't it be just as reasonable to claim that there were another force involved rather than saying that the Law has been debunked?
You can take my gun from me...oh, wait, wrong 2nd law...
An example to illustrate the breakdown of theories: the Special theory of Relativity modified Newtonian mechanics on a fundamental level. However, for speeds much less than the speed of light (which is what most of us experience in daily life), it is STILL Newtonian mechanics that we use, even in several cutting edge research fields. The rule of thumb in research is: never use a full model when an approximate one is just as accurate in the domain of interest. In much the same way, even if MOND were true, any deviations from Newton would kick in at EXTREMELY LOW accelerations (of the order of 10^-20 m/s^2 which is about 10^-21 g, something next to impossible to duplicate in a lab because of ambient vibrational noise which is usually MUCH higher (say, about 10^-9 g is a VERY quiet environment)). This is the reason why the paper (which attracted our group's attention a few weeks ago) proposes an experiment at such well-defined times and locations. To put it bluntly, this is an ad-hoc modification in the sense that there is just no justification for the modification. Of course, I don't even think MOND would replace the Dark Matter hypothesis. One might even argue that this modification is simply a way of expressing the effect of Dark Matter (just a thought).
It's worth pointing out that this paper is only publihed on a preprint server - that means it has not been through peer review, so needs to be treated with a lot of caution. There's an awful lot of totally crazy stuff on preprint servers. Not that I'm saying it's totally crazy - whilst I'm a physicist, I do condensed matter not astro - amd wouldn't describe myself as qualified to have a definitve opinion. But I would be both cautious and skeptical until proven oherwise.
These theoretical astrophysicists are getting good at what they do.
The submitter of this article (and the populace of Slashdot as a whole) doesn't get the point of this article. Ignatiev isn't suggesting this experiment out of thin air, he's suggested a novel earth-based experiment to help explain the anomaly in galactic rotation (ie. Dark Matter). To explain this anomaly some theoretical astrophysicists modify Newtonian dynamics in a small way so that the galactic rotation calculations come out correct. Others introduce Dark Matter, or alter gravitation itself.
He basically wants to observe an object smaller than 7 cm x 40 cm x 40 cm at the precise moment and the precise location on the earth such that it would experience an acceleration that is much smaller than the extra acceleration it would experience as proposed by the modified Newtonian dynamics. So any extraneous acceleration observed at this moment had to have come from modified Newtonian dynamics.
The interesting thing about this article is that it isn't just a wild claim by a crackpot scientist, it's the proposition of an extremely accurate measurement using the most advanced technologies we have available. Of particular interest to me was that the proposed effect was two orders of magnitude larger than that observable by LIGO, a gravitational wave detector, suggesting that such an experiment is actually possible.
You're right that you can still use an equation that looks like F = dp/dt in GR, but I still think the original second law is wrong with all the quantities defined as they were. Writing it your way, it is then the definition of momentum which is wrong (or going on, the definition of velocity as dx/dt not dx/dTau). (Also in GR F= dp/dTau, not dp/dt if t is the time coordinate). The symbols in GR just happen to look and act quite like the newtonian symbols, but are interpreted differently.
Anyway, it is the error in predicted motion that is interesting here, where 'F=ma' gives the newtonian motion,
but this becomes like 'F = ma + m Gamma Vi Vj' in GR. You can't clearly see the different motions each theory gives in F = dp/dt.
We know the spectrum and angular distribution of the cosmic microwave background to high precision.
This is the only statement that is correct since it is the only conclusion derived directly from observation. A lot depends on how accurate our models of the universe and physics are. I think MOND is unlikely to last, but the theory is yet viable. Your claims about the age of the universe, mass of neutrino, etc are likely to be correct, but it would be embarrassing if these observations turn out to be dependent on assumptions that are incorrect. Eg, perhaps Type IA supernovas are different in the early universe than they are now (even though physical law is the same, there are substantial differences like elemental composition), perhaps we're incorrect about our local gravity environment (eg, we're deeper in a gravity well) and this effects our perception of the temperature of the cosmic background, or perhaps a more accurate model of the universe involves oscillating yet massless neutrinos.This article (and the whole MOND thing) would make some sense if the systems described in them were not accelerating because of gravity. Sun is subjected to the gravity forces toward the center of our galaxy, so its path relative to the center of the galaxy is not a straight line but a circle -- though a very large one. I find it to be an extremely weird oversight considering that the whole hypothesis exists to describe parameters of the very same motion of stars in galaxies. So even when a point on the Earth surface is not accelerating in the Sun's coordinate system, it still does in the galaxy's coordinate system.
Worse yet, MOND does not explain anything about galaxies because galaxies themselves accelerate. They are not distributed evenly and uniformly in space but form clusters. Each cluster just like a galaxy itself, is pulled together by gravity, so galaxies experience some acceleration in the cluster's coordinate system because of the gravity of other galaxies.
Obviously this acceleration is not detectable locally because it is caused by gravity -- for the same reason objects in orbit are "weightless". To find out that you are in freefall (or in orbit, what is the same thing) without looking at other celestial objects you have to throw something and observe its movement -- since gravity is not parallel and uniform everywhere, after the object will get far enough from you, it will be noticeable that its trajectory is not a straight line relative to you, as it would be if you weren't accelerating at all. However locally gravity and acceleration are indistinguishable, and at the scale of Solar system or galaxy the size of such "local" area is huge.
MOND is talking about absolute acceleration that should be clearly distinguishable from gravity. However if we will try to find something in the universe that is really "unaccelerated" by this definition, there will be very few objects in this category, if any. Certainly it would not be massive centers of galaxies, Sun or two spots on the Earth surface the author of the article proposes as locations for his experiments.
This is the theoretical part of the problem. Now, the practical one. In two proposed spots the conditions that article author expects to happen last for a very short time and happen once a year. The extent of effect is similar to the influence of gravity from many existing celestial bodies. Tidal waves caused by Moon and affected by the shape of oceans, condition in the atmosphere, movement of Earth crust, etc. are likely to produce more noticeable influence on any test body that may be used in the experiment. Though I didn't do any calculations, it's hard to believe that variations of tidal waves caused by changes in weather will be less than supposed effect of "modified" 2nd Newton's Law even if it worked the way that the article author's proposed. And since conditions are supposed to be so rare, there is no way to collect enough samples for any statistical analysis.
In the end, I can add that if your experiment is to look for a black cat in a dark room, it shouldn't be a surprise if the result is negative regardless of the actual presence of a cat. However this makes no excuse for proposing that the cat is in the room when there is no reason for it to be there in the first place. Both theory and proposed experiment look extremely stupid, and if MOND can be modified to explain why it should include movement of stars within galaxies but not movement of galaxies in clusters, maybe it would be worth a second look. For now it's just that -- stupid idea with no foundation and no viable method of verification.
Contrary to the popular belief, there indeed is no God.
That assumes that the difference in position and momentum is greater than the uncertainty principle allows, which isn't immediately obvious. If you do the calculations, you may just find that the difference is smaller than QM allows, and thus there is no difference.
The TIMECUBE.
Wh47 d1d j00 541, 31337 15n't t3h r0xor5 ne m0r3???