This will not end well...

[Blog of Reason]

Discussion thread for the blog entry "This will not end well..." by AndromedasWake.

Permalink: http://blog.leagueofreason.org.uk/science/this-will-not-end-well/

 

[Merc]

Go get 'em AW! I can't wait to watch you go all Copernicus on their dumb asses. While you're at it, could you also look into reality-smacking the Flat Earthers? Yes, there is a society in the 21st century that claims membership from individuals who are convinced the Earth is flat. I swear the human race is devolving... :facepalm:

 

[theatheistguy]

I can see this ending almost as well as thunderf00t vs Ray Comfort

 

[australopithecus]

As deluded as flat earthers are, at least they're entertaining. This'll be fun.

 

[Pulsar]

AW, if you need material to debunk these guys, I can help. Take a look at my third post, because I think it contains an irrefutable argument against geocentrism: stellar aberration. The physics will go way over their head, but it's a treat for those who love science.

But first, a few other arguments:

Believe it or not, some geocentrists, like Gerardus Bouw, have a Ph.D. in astronomy!!! So, many of these guys actually have a (twisted) notion of physics, and are familiar with phenomena like parallax, Coriolis force or Doppler shift. That makes it all the more fun to debunk their nonsense.

There seem to be several (inconsistent) arguments made by geocentrists. The first is a cosmological one: the distribution of galaxies appears uniform in all directions. Well, it will look uniform from every place in the universe. And some geocentrists seem to think that the cosmic background radiation appears almost uniform in every direction. But that's not true. In fact, the CMB looks like this:

It has a so-called dipole moment: on one half of the sky, the radiation is redshifted, and on the other half it's blueshifted. This Doppler shift is caused by the combined motion of (a) the earth around the sun, ca 30 km/s (b) the sun around the galactic centre, ca 230 km/s and (c) our entire Galaxy, ca 600 km/s in our local Supercluster. The well-known graphs that show the small CMB anisotropies, detected by COBE and WMAP, are already corrected for the dipole moment.

By the way, the motions of the sun and our Galaxy can be disentangled. The motion of the sun can be calculated from observing the Doppler shifts of the hydrogen 21 cm lines in the spectra of molecular clouds. Combining enough data, the rotation curve of our Galaxy can be obtained, including the velocity of our sun.

 

[Pulsar]

The biggest morons of the bunch also deny the daily revolution of the earth, and claim that the entire universe rotates around us in 24h. Those are usually the "aether guys". They don't understand the Michelson Morley experiment or the Sagnac effect and somehow conclude that those debunk relativity and support a rest-frame (the aether), while it's the complete opposite. Yet, they explain Foucault's pendulum (i.e. the Coriolis effect) by invoking Mach's Principle, which is ironically supported by relativity. Basically, Mach's Principle states that the inertia of a massive object is determined by all other objects with which it is in causal contact. So, the stars and galaxies cause the Coriolis effect because the earth rotates with respect to them. And yes, in principle the same effect occurs if all the stars and galaxies rotate around us. But that doesn't mean that this interpretation is equally correct. Why would all galaxies rotate around us in 24h, regardless of their distance? And the rotation velocities of distant quasars would be ridiculous!

But the funniest and best counterargument comes from Francis Graham. As he remarked: the daily rotation of the earth isn't constant. Indeed, it varies, by less that a millisecond, every time the distribution of the earth's mass changes, as during a major earthquake, for example (see http://www.jpl.nasa.gov/news/features.cfm?feature=15). In heliocentric terms, this means that the earthquake has altered the rate of the earth's rotation. In the geocentric model, however, it would be "the heavens" -- supposedly revolving around the earth -- which are speeded up or slowed down by the quake. How does the information get from the earthquake all the way out to the distant galaxies... then back to the earth, much faster than the speed of light?


And then there are people like Malcolm Bowden, who made this amusing series of videos. I don't know if he came up with the ideas himself, or if he got them from e.g. these guys. Now his universe is the wackiest of them all. Not only is he an "aether guy", denying the daily revolution of the earth, he thinks he found a way to explain everything a normal guy would see as evidence against geocentrism. First, he starts with a Tychonic model of the solar system. That is: the sun and the moon revolve around the earth, but all the other planets revolve around the sun. That's the model proposed by Tycho Brahe, because he failed to measure the parallax of stars. It also explains the retrograde motion of e.g. Mars. Now, this goes directly against Newtonian dynamics. After all, small objects revolve around heavier objects. Or more precisely, both revolve around their barycentre. How can the sun, much heavier that us, revolve around the earth? And why does Jupiter revolve around the sun and not around us? And how does he explain the trajectories of our spacecraft in a geocentric model?

Bowden seems also unaware of the effect of the moon: because of it, we wobble in a month around the earth-moon barycentre, located 1700 km beneath our surface, at around 12 m/s. This effect is measurable: it causes a Doppler shift in the spectra of the sun and other stars, and fluctuations in the rotation period of pulsars. Also, how does he explain the high tides when the moon is on the other side of the earth?

But Bowden goes further. He accepts parallax. Great. But, according to him, parallax is not caused by our motion around the sun. Instead, all the stars themselves wobble during the year. And doing so, they don't seem to move with respect to the sun...

Ignoring the butchering of Newtonian physics and relativity, all the arguments mentioned above can be summarized in one statement: the effects we observe, like parallax, Doppler shift and the Coriolis force, are relative effects. They are caused by the relative velocity between us and the rest of the universe. So, the geocentrists say, all these effects can be explained with us standing still and everything else revolving around us, no matter how bizarre their motion.

So, is there a counter-argument that does not depend on relative velocities? Is there one more thing we can throw at them, the definitive evidence that we are not stationary? The answer is: YES!

 

[Pulsar]

In 1725, parallax was still not detected, which encouraged the die-hard geocentrists. James Bradley was also trying to observe it, but instead he stumbled upon a different phenomenon: stellar positions did change during the year, but not as expected from parallax. Stars near the ecliptic poles made a near-circular motion, with a radius of 20.5 arcseconds, while stars near the ecliptic plain appeared to move back and forth on a straight line, again with a radius of 20.5". All other stars in the sky followed an elliptic path, with different short axes, but the same long axis of 2x20.5". This identical value for all stars cannot be explained by parallax, because parallax depends on the distance of a star. Surely not all stars have the same distance to us... Moreover, the maximum displacements of 20.5" from the mean occurred when a star lies in conjunction with the sun or opposite the sun. In contrast, the maximum displacements due to parallax should be when the star makes a 90 degree angle with the sun.

Two years later, Bradley was able to explain what he had found: an effect called stellar aberration (aka aberration of light, or the Bradley effect). It's well known in everyday life: suppose you're standing in the rain, pouring straight down. When you start running, the raindrops appear to change direction, and hit your face, so you need to hold your umbrella diagonally in front of you. A similar effect happens to light from a star.

First, let's try to see what happens in Newtonian physics. Suppose there's a star, in absolute rest, that emits a beam of light at an angle theta. If we were standing still, we would see the star through a telescope at that angle. However, what if we're moving? First of all, the speed of light is finite, so it takes a little time to travel from the top of the tube to the observers eye, namely a time t = h/c. As a consequence, we have moved a certain distance during that time: if our velocity is v, then our telescope has moved a distance vt = vh/c. Therefore, to be able to see the star, we must tilt our telescope to an angle phi, so that the light passes through the tube while it's moving. So, we see the star at a different angle phi than its true angle theta:

which is independent of h, i.e. independent of the length of the telescope tube. The only variables are our velocity, and the speed of light. If the star lies in conjunction with the sun or opposite the sun, its angle theta is 90 degrees, leading to the maximum displacement. And indeed, since v = 30 km/s, we obtain the value 20".49552, called the constant of aberration, for every star. But here's something remarkable: we assumed that the star was at rest. Yet, stars clearly move: e.g. Barnard's star has an observable proper motion, and binary stars revolve around each other. But in Newtonian physics, the motion of the star would change the speed of light it emits, which would change its aberration. This is not the case, the constant of aberration leads to a surprising conclusion: the speed of light is constant, regardless of the velocity of the source! So, we've found evidence for relativity, long before Michelson Morley. And, it seems that the stellar aberration of a star does not depend on its velocity. There's additional evidence for this, as remarked by Edward Eisner: if aberration would depend on the motion of a star, then this would affect visual binary systems. In binaries, we can observe both stars following the elliptical orbits expected from the laws of Kepler. But aberration would cause a shift in their positions, disturbing these elliptical orbits. As we don't observe these distortions, aberration is indeed independent of on the motion of a star.

So, we need to solve the problem using relativity. This is a bit more difficult to do, but using the general velocity addition formula (see here for a calculation), one can find the formula

However, this time the term v is not our velocity, but the relative velocity between us and the star. That's to be expected from relativity: there is no preferred frame of reference, so the formula should hold everywhere. But this seems in contradiction with the conclusion above: the stellar aberration of a star does not depend on its velocity. What's going on?

How does the relative velocity of a star affect its appearance? First, its spectrum would be Doppler shifted (including a transverse Doppler shift). Also, its beams of light would be tilted towards the direction of the stars motion (that's the aberration effect). That causes an effect called relativistic beaming: the concentration of light in the star's forward direction is higher than the rear direction, so its brightness is higher at the front than at the rear (see also http://en.wikipedia.org/wiki/Relativistic_Doppler_effect). But both of these effects are very small (a star's velocity is of the order 100 km/s), and we have no way to compare what we see with what the star would be like if it was at rest with respect to us. But more importantly, while the velocity of the star has an effect on its individual beams, it has no overall effect on the direction in which we see the star. Indeed look at this figure:

If the star were standing still, its beam alpha would travel towards us, and we would detect the star in 'horizontal' direction. But when the star moves upward, beam alpha is tilted diagonally upward and it misses us. But now, beam beta will be tilted horizontally, so beam beta will reach us, and again we observe the star in horizontal direction. So, while the aberration has affected the beams, it hasn't affected the location of the star: even in relativity, aberration is indeed independed of on the motion of a star.

But now we have a new paradox: if the motion of the star itself doesn't cause aberration, how is it possible to detect aberration at all? As stated, the relativistic formula depends only on the relative velocity between us and the star. So the frame of reference shouldn't matter. Again, what's going on? The solution is a beauty: it's impossible to detect aberration from one single observation. However, what we call aberration is actually a comparison between two observations: we observe the same star twice, at different times of the year. In other words, we need to apply the relativistic formula twice: suppose, in some frame of reference, that the earth has a velocity v1 at one time of the year, and a velocity v2 at a later time. And suppose that the velocity of the star, w, remains constant during this time. Then one can derive the difference between both observations (again, see here):

The velocity of the star w cancels out! So the aberration we observe is due to the relative velocity v21, between us and OURSELVES at a later moment! And this is the difference with other effects like parallax. Those phenomena can be explained by a relative motion between us and a star, but aberration can only be explained by a relative motion between us and ourselves. Our velocity changes, therefore we orbit the sun, even using relativity!

More info:
http://en.wikipedia.org/wiki/Aberration_of_light
http://en.wikipedia.org/wiki/Relativistic_aberration
http://en.wikipedia.org/wiki/Relativistic_Doppler_effect
http://arxiv.org/abs/astro-ph?papernum=0203056

 

[Kain]

I almost had to take a Valium when I saw "The Evolution Delusion - Geocentricity Part 2" where he claimed the Michelson - Morley experiment proved the earth was stationary.