Tuesday, December 21, 2010

Did a Jesuit priest discover the Coriolis force?

The Physics arXiv Blog uncritically promotes a preprint with an insanely long title,
The Coriolis Effect Apparently Described in Giovanni Battista Riccioli's Arguments Against the Motion of the Earth: An English Rendition of Almagestum Novum Part II, Book 9, Section 4, Chapter 21, Pages 425, 426-7
in which Christopher Graney, a physics instructor at a Kentucky community college, argues that the Italian Jesuit Giovanni Battista Riccioli (1598-1671) discovered the Coriolis force in 1651. The Physics arXiv Blog even adds that Riccioli was "centuries ahead of his time".



Given the fact that Riccioli's argument was nothing else than a traditional salvo of the Aristotelian pseudoscience against Copernicus' heliocentric theory in particular and against the emerging discipline of physics in general, I can only say: holy cow.




Note that the Coriolis force,
F = -2m Ω x v
was derived and written down, in this very form, by Gaspard-Gustave Coriolis in his 1835 paper. It is an apparent force that you have to add to the description of physics in the rotating frames - and Ω is the vector defining the rotation of the frame (with the right magnitude and the direction given by the axis of the rotation).  By the term "Coriolis force", we actually mean this formula, so it's obvious that it couldn't be called "Riccioli's force" because he didn't have the formula.

But it's not about the formula only.

Obviously, what appears in the text verbally coincides with a sloppy description of the Coriolis effect we could produce today: a cannon shoots in several directions (North, East) and if the Earth were rotating around its axis, which is what Riccioli denies, the projectile would be deflected differently depending on the direction. But what Mr Graney and the Physics arXiv Blog are totally missing is a "detail", namely that Riccioli's way of thinking about the motion is fundamentally wrong.

In particular, it's essentially still the old Aristotelian thinking. Note that Aristotle lived between 384 BC and 322 BC. When Riccioli wrote his text in 1651, Galileo Galilei was already dead; all Galileo's contributions were available to the whole world. Isaac Newton was 9 years old and was arguably closer to a correct picture of mechanics than Riccioli.

Riccioli wasn't centuries ahead of his time; he was mindlessly defending myths that should have been abandoned 2000 years earlier when Aristotle died.

The idea that there would be new effects in various moving, rotating, and accelerating frames was not Riccioli's personal groundbreaking discovery; it was exactly the format of the bogus arguments that were used against the heliocentric theory all the time.

Physics was born when the flagrantly obvious laws of inertia were acknowledged.
Objects remain in the state of uniform motion or rest if no force is acting upon them,
says the first Newton's law. Galileo was fully aware of its essence. And all philosophers in ancient Greece and the Roman Empire had access to a huge body of empirical evidence that pretty much proves that the principle above was right. For example, you may take a Roman coin and it will roll and roll. It doesn't need any force to continue. Just watch it for a while.

However, Aristotle's dogma was very different
Objects instantly return to the state of rest once the force cease to act.
Now, Newton's law is obviously expanding around the idealization in which the friction forces and other forces are zero or neglected (and may be added later); Aristotle's law is "expanding" around an infinite-friction limit. Are both attitudes legitimate?

Well, if you didn't know anything about physics, they would look equally legitimate to you. Just like S-duality says that we may expand around two different values of a coupling constant, zero or infinity, we might also expand around two different values of friction, zero and infinity.

However, if you actually know something about the physics of motion, you know that this superficial argument is just wrong. One cannot expand the laws of motion around the "infinite friction" limit. Once you start with the assumption of an infinite friction, the information about the motion - and the motion itself - is instantly lost and you can't get it back by any "corrections". These days, we say that the friction is irreversible, much like all other processes that increase the entropy. Because it is irreversible, you can't start your description of the world with the assumption that the friction is infinite.

So it is only Newton's approach that can lead to a valid description of the laws of motion: uniform motion is the default state and one needs forces to change the momentum and one needs forces to bring an object to rest, too.

It took approximately 2000 years after the death of Aristotle for the people to establish physics as we know it. These two relatively dark millennia were dark exactly because many people were hysterically unwilling to admit that the previous paragraph was right. They were scared of motion and they were scared of moving frames. They were inventing bogus arguments why they couldn't live in them. Riccioli was no different.

What a surprise, people like Riccioli were not complete idiots. They could also produce pretty pictures. But they were still idiots and their way of reasoning - or the lack of it - was totally reactionary. They were the very reason why the scientific revolution couldn't have exploded a few centuries earlier.

A reason why Graney and the Physics arXiv Blog celebrate the Jesuit propaganda is that they totally take the Coriolis force out of the context. The Coriolis effect is not a new theory of the whole physics that replaces the Newtonian mechanics. On the contrary, it is a tiny addition to the Newtonian mechanics.

And whatever NM is, you simply can't be credited for tiny additions to NM if you completely deny NM itself.

It would be as preposterous as crediting Aristotle with the discovery of viscosity because his model of the world already assumed viscosity that was not just nonzero but actually infinite. ;-) Well, Aristotle talked about some situations where the friction forces were large (a horse in the mud): but he was not the only one who was familiar with the situations so he can't be credited for the discovery of these "experiments". He can't be praised for the discovery of the theoretical explanation, either, because it was wrong. The same thing applies to Riccioli.

The essential point in this whole debate was whether or not life could proceed in moving frames - whether motion itself was lethal. Aristotle and the Jesuits wanted to believe it was very bad to move their asses; for the bigots, motion was dangerous (much like the global warming crackpots think that climate change is dangerous). But motion is not dangerous. In fact, the physical phenomena observed in uniformly moving frames are indistinguishable from the phenomena at rest.

Riccioli's scenario is of course similar to an argument we could use to derive an effect of the Coriolis force today (and sloppy students won't find any difference); the Jesuits tried all conceivable complicated setups to defend their beliefs (Riccioli printed 77 reasons why Copernicus was wrong - you offer 77 lousy arguments if you don't have a single solid one, a wisdom that is true for the climate alarmists as well) so it is not shocking that they also found the Coriolis setup at some point. But what matters is that the most important conclusions they made about the setup were wrong. That's why we can say that the overlap between Riccioli's analysis and the present explanations of the Coriolis force was just a coincidence.

Obviously, if he really understood what he was saying, he would realize that it was no argument against the Copernican model. Why? He could estimate the magnitude of the effect to see that this effect is so small that it could be very real; I will show the estimate momentarily. And he could even construct the Foucault pendulum (which was only shown 200 years later, in 1851).

Was there some mathematics that was missing in 1651? It's preposterous. Small boy Isaac Newton was already starting to work on the differential calculus. ;-)

Imagine that it's 1651 and you really understand the Coriolis argument that is being attributed to Riccioli. Galileo has already made his contributions and died: everyone knows that one should test the hypotheses before he says that they are correct or wrong. So let's test whether the phenomenon exists or not. We must first calculate the predictions.

The heliocentric theory - with a rotating Earth - implies the deflection of the projectile. How much will it deflect? Well, let's look at the anomalous change of the velocity. If you shoot from the equator towards the pole (to the North), the East-West velocity beneath the projectile will change from the equator velocity to zero near the pole, thus modifying the information about the speed and direction of the projectile. The rotation-induced velocity near the equator is 40,000 km over 24 hours, about 463 m/s. The circumference of the Earth had been approximately known from the era of ancient Greece.

(Riccioli himself, together with Grimaldi, measured the circumference of the Earth between 1644 and 1656 - although their error 360x 10 km, about 10%, caused by various defects of their method, was worse than Willebrord Snellius' earlier measurement that was off by 360x 4 km , i.e. 4%, only. Riccioli was also the first man who tried to measure the Earth's gravitational acceleration.)

However, normal projectiles in 1651 didn't shoot 10,000 kilometers, to reach the pole from the equator. They may shoot 100 meters or so. That's 100,000 times less than 10,000 kilometers. Correspondingly, the change of the East-West velocity beneath the projectile will be 100,000 times smaller than 463 m/s, i.e. about 4.6 millimeters per second. That's clearly too small to be measured so the conclusion is that one can't distinguish the two theories by the unrefined projectiles available in 1651.

If we can't distinguish them, we have no right to say that one of them is right and the other one is wrong; we can only abandon theories that have been falsified; science doesn't give you any tools to favor one explanation if the evidence speaks a neutral language. (This simple point was misunderstood by the Jesuits and it is still misunderstood by the dumb critics of string theory today.)

Now, tell me what was unavailable in the previous 3 paragraphs in 1651? I haven't even used any Newton's laws of motion or anything of the sort. It was just a simple scaling argument. We know the maximum change of the East-West speed; and we know the approximate fraction of this change we can probe by cannons. The product is so tiny that the effect could very well be real.

If someone can't make this simple step - at the same time when others are already beginning to work with the differential calculus - then he simply can't be credited with a discovery just because some words resemble the words in a correct argument. You have no idea how to apply the "discovery" or use it, even in the simplest situations, so you simply have nothing to do with the discovery.

And that's the memo.



The luminiferous aether: a similar story

In the story above, modern people were defending the Aristotelian misconceptions as being "centuries ahead of their time". It's preposterous but it is not the only example of passionate heirs to some of the history's most mistaken thinkers.

One of the 20th century revolutions in physics began with special relativity. Relativity only became possible once Einstein realized that the vacuum was totally empty and there couldn't have been any aether that would pick a preferred reference frame.

Many physicists of the 19th century - including some big shots - believed in the luminiferous aether, an environment that has to exist for its waves to behave as light - in the same sense as the air has to exist for the sound waves to propagate. They were convinced that they had some actual evidence that the aether existed.

However, they didn't have any existence. The only thing they had was a dogma stating that a plausible analogy was necessary. One could envision the analogy - the aether had to be composed out of "atoms" just like the air - and they thought it was necessary.

If you think about it, the existence of a possible analogy doesn't prove that the analogy has to be realized in Nature. The argument was totally fallacious. In fact, Einstein realized that there was an overwhelming evidence that the analogy was wrong. Maxwell's equations work and don't seem to require any "speed of the aether": they can predict the speed of light without it. Because the aether speed seems to be absent in the fundamental equation that agree with electromagnetism, it seems that the aether is unphysical. Einstein was right, of course, and he didn't even need to take the Morley-Michelson experiments into account.

The emptiness of the vacuum, and the Lorentz symmetry that requires the emptiness, was totally crucial to make the relativistic step. And on the contrary, the idea that the aether had to exist was exactly what prevented the relativistic revolution to arrive e.g. 50 years earlier. The aether was a highly regressive idea.

Nevertheless, you may see how it was possible for the 19th century physicists to be stuck in the logical fallacies behind their opinion that the aether had to exist: some 21st century physicists are still stuck in these fallacies! That includes all the researchers of loop quantum gravities, spin foams, Ted Jacobson, and lots and lots of others. The difference between Maxwell and them is that Maxwell didn't live in a world where the arguments against the existence of the atoms filling the vacuum had been known for 100+ years.

2 comments:

  1. But Riccioli actually acknowledges Newton's law of inertia (atleast in some vague form). Without this, the argument that the speed of the cannon at the equator will have a horizontal component of earth's velocity is invalid. Also, according to Aristotle, this velocity would die out (as there is no force pushing it) when it reached the poles.

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  2. Dear f.,

    well, yes, he doesn't deny the inertia totally. That would be really painful 9 years after Galileo's death. Galileo invented the concept for modern times.

    Galileo has figured out the detailed shape of trajectories of falling bodies, among many other things, and you want me to praise people for "not denying inertia completely" 9 years after Galileo closed his life's work, 21 years after Kepler's death, and 108 years after Copernicus' death? WTF?

    It's like praising someone who starts to appreciate that the neutrinos could oscillate, or whatever that was found a decade ago, or that string theory could be right. This is just not where science stays in 2010. Those people have nothing to do with the state-of-the-art research.

    Riccioli still couldn't get rid of the Aristotelian sentiments that blocked his rational reasoning and prevented him from making any right conclusions about the motion of the Earth and the celestial bodies.

    I don't think that Aristotle had any genuine laws for the motion of bodies that were thrown into the air. Riccioli had some vague understanding of these things - but holy crap, they have been known for decades to the whole world. He was still trying to revert their consequences in 1651 which is just painful.

    It's not surprising that there's no widespread consensus that crackpots of the LQG, Swolin, CDT, ... kinds are trying to drag physics under the water if we can't even agree that the Jesuits had contributed negatively to the physics knowledge of the mid 17th century.

    Best wishes
    Lubos

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