The Watchmaker: my fav argument

[polymath257]

Ptolemy and Copernicus both used epicycles and were pretty bad as sand alone theories. Copernicus certainly did NOT disprove Ptolemy. Tycho's hypothesis of a fixed Earth with planets orbiting the Sun and the Sun orbiting the Earth shows that a fixed Earth description was consistent with the observations at the time.

On the other hand, the joint work of Galileo and Kepler *did* undermine Ptolemy's system. Kepler showed how to avoid epicycles and Galileo provided observations that directly contradicted Ptolemy's views. It was still possible to have a variant of Tycho's system, but it was no longer possible to have the old Ptolemaic system.

It should also be noted that the 'physics' that supported the Ptolemaic system was also undermined by Galileo's observations. Because of this, the traditional arguments for a fixed Earth were invalidated and a replacement was found. The final nail was Newton's discovery of his laws of motion and his law of universal gravity. This gave a much simpler description that was also much more accurate that either the Ptolemaic or the Copernican system. It even surpassed the system of Kepler by adding in additional corrections *that were motivated* by the theory as opposed to being ad hoc add ons.

[John 6IX Breezy]

The final nail was Newton's discovery of his laws of motion and his law of universal gravity.

Out of curiosity, since I'm reaching far beyond my comfort zone, what role does Einstein play in this battle? If Newton put the final nail, but Einstein is often described as somewhat replacing Newton, what does Einstein's theory do to these models? Relativity seems to make use of "frames of reference" and "observers," which at first glance is the main difference between the geocentric and heliocentric model.

[Peebothuhlu]

The final nail was Newton's discovery of his laws of motion and his law of universal gravity.

Out of curiosity, since I'm reaching far beyond my comfort zone, what role does Einstein play in this battle? If Newton put the final nail, but Einstein is often described as somewhat replacing Newton, what does Einstein's theory do to these models? Relativity seems to make use of "frames of reference" and "observers," which at first glance is the main difference between the geocentric and heliocentric model.

Well.... help explain why Mercury does its weird little thing in its orbit. 

From a poor memory I think there's a weird little 'bulge'(?) (Or maybe an excentricity in the shape of the orbit?) or some other strangeness that, under Newton, had people looking for another planet tucked in there near Mercury and the Sun.

Einstein's 'Bendy space time' accuratley accounts for the Sun's immense gravity on the tiny mass that is Mercury orbiting so close.

That's all I've got off the top of my head. Hopefully others will add better stuff.



Not at work.  

[GUBU]

Hawking's point was not that one can arbitrarily chose any theory you like. 

I don't know whether or not Hawking would agree. But as far as his book is concerned, he only favors one theory over the other on the basis of simplicity (which I would argue is equivalent to being arbitrary). And he seems to leave the actual nature of the universe to philosophy. Here's the rest of his quote for reference:

"Despite its role in philosophical debates over the nature of our universe, the real advantage of the Copernican system is simply that the equations of motion are much simpler in the frame of reference in which the sun is at rest."

I don't know whether Hawking would agree with HappySkeptic. I don know he wouldn't agree with ypu, as you're lying both about what he said and about what he meant.

I do notice that people like you tend to wait until prominent scientists are dead before twisting their words. Not very moral of you, isn't it?

[possibletarian]

I don't know whether or not Hawking would agree. But as far as his book is concerned, he only favors one theory over the other on the basis of simplicity (which I would argue is equivalent to being arbitrary). And he seems to leave the actual nature of the universe to philosophy. Here's the rest of his quote for reference:

"Despite its role in philosophical debates over the nature of our universe, the real advantage of the Copernican system is simply that the equations of motion are much simpler in the frame of reference in which the sun is at rest."

I don't know whether Hawking would agree with HappySkeptic.  I don know he wouldn't agree with ypu, as you're lying both about what he said and about what he meant.

I do notice that people like you tend to wait until prominent scientists are dead before twisting their words.  Not very moral of you, isn't it?

When your faith is based on twisting the words and deeds of dead people to fit your denomination (hence so many different ones) , what did you expect ?

[HappySkeptic]

The final nail was Newton's discovery of his laws of motion and his law of universal gravity.

Out of curiosity, since I'm reaching far beyond my comfort zone, what role does Einstein play in this battle? If Newton put the final nail, but Einstein is often described as somewhat replacing Newton, what does Einstein's theory do to these models? Relativity seems to make use of "frames of reference" and "observers," which at first glance is the main difference between the geocentric and heliocentric model.

Newton's laws of motion work in the limit of small speeds,  while Special Relativity must be used for high speeds.  Special Relativity also creates new physics, such as frame-of-reference transformations for length and time, and mass-energy equivalence (E=mc^2).

Newton's law of gravity works in the limit of small levels of gravity.  However, for higher gravitational forces, one must use General Relativity.  This solves the precession of Mercury.  General Relativity also creates new physics, such as gravity bending spacetime (and therefore bending light).

Newton's theories are much simpler and easier to use in the realm in which they work.  Relativity is a superset of Newton, and solves new problems.

[polymath257]

The final nail was Newton's discovery of his laws of motion and his law of universal gravity.

Out of curiosity, since I'm reaching far beyond my comfort zone, what role does Einstein play in this battle? If Newton put the final nail, but Einstein is often described as somewhat replacing Newton, what does Einstein's theory do to these models? Relativity seems to make use of "frames of reference" and "observers," which at first glance is the main difference between the geocentric and heliocentric model.

The simple answer is 'it's complicated'.

Special relativity has no distinguished inertial observers. In other words, motion at a uniform velocity cannot be distinguished from being at rest in SR.

BUT acceleration is a different story, even in SR. There is NOT a symmetry between observers in accelerated frames of reference. That is part of the resolution of the twin paradox: the twin that experiences the acceleration is the one that ages less.

In general relativity, things get stranger. gravity is considered to be a curvature of spacetime and different locations do have different curvature. That means that two observers with different spacetime geometry are NOT equivalent. Things like proper time (what is measured by clocks) depends on the path through spacetime taken.

In particular, a rotating observer will experience corriolis forces because of their peculiar frame of reference. They can see themselves as being at rest, but to do so drastically limits their usable coordinate system. In particular, distances that 'look' like they would be moving at faster than the speed of light can be present. An observer that is not rotating will not have those same limitations. In any case, all local motion will appear to be less than the speed of light.

So, in reference to the current discussion, the Ptolemaic system cannot be fit into GR. A *very limited* version of Tycho's system is at least consistent with GR, but there are severe restrictions on the coordinate system used by the observer on a 'fixed Earth' that are not present for an observer that is closer to being inertial.

This actually shows up in cosmology, by the way. In cosmology there *is* a preferred reference frame for any observer: the one in which universal expansion does not depend on direction. The Earth is NOT in that frame of reference: we are moving with respect to it. That motion shows up as a 'dipole' component to the cosmic background radiation.

[Angrboda]

Truly, the theories that "All swans are white" and "All swans are black" both validly describe the world correctly for appropriate definitions of black and white.  

I'm not sure I understood your analogy, but I would be careful not to confuse theories with descriptions. The phrase All swans are X doesn't function as a theory.

I believe you are mistaken. It is a perfectly good theory that explains the evidence. Just as "All electrical quantities in a circuit satisfy ohm's law" is a valid theory, so is "All swans are X." The role of a theory is to explain the evidence. Perhaps you are confusing it with, "All swans that have been observed are X." Please explain to me why you feel it is not a valid theory. Theories are necessarily descriptive, so the dichotomy you propose is not correct.

[polymath257]

Out of curiosity, since I'm reaching far beyond my comfort zone, what role does Einstein play in this battle? If Newton put the final nail, but Einstein is often described as somewhat replacing Newton, what does Einstein's theory do to these models? Relativity seems to make use of "frames of reference" and "observers," which at first glance is the main difference between the geocentric and heliocentric model.

Well.... help explain why Mercury does its weird little thing in its orbit. 

From a poor memory I think there's a weird little 'bulge'(?) (Or maybe an excentricity in the shape of the orbit?) or some other strangeness that, under Newton, had people looking for another planet tucked in there near Mercury and the Sun.

Einstein's 'Bendy space time' accuratley accounts for the Sun's immense gravity on the tiny mass that is Mercury orbiting so close.

That's all I've got off the top of my head. Hopefully others will add better stuff.



Not at work.  

The story of Mercury is actually pretty informative in how accurate things are these days.

Mercury orbits the sun every 88 days. We can think of this as going through 360 degrees of its orbit every 88 Earth days.

The anomaly in Mercury's orbit that was not explained by Newtonian physics amounts to 43 *seconds* of arc in that orbit over the course of a century.

The Ptolemaic system was regularly off by tens of degrees in the position of planets *in our sky* over the course of decades. That 43 seconds of arc in the orbit of Mercury would be even less as an apparent arc in our sky.

The general relativistic correction to the orbit of Mercury took into account that full 43 seconds of arc per century.

[John 6IX Breezy]

The role of a theory is to explain the evidence.

Right, theories are explanations of things. And explanations either give a causal account of phenomena, or a unification of them. All swans are X isn't a causal account for anything, or a unification of anything, it's simply a description of what all swans are. Such descriptions might instead fall under the category of laws. Consider the structural similarity between your phrase, and the first law of behavioral genetics: All human behavioral traits are heritable.