Weird Earth. Donald R. Prothero
platform with a series of pegs or other markers around the edges. (There are many good video demonstrations online if you search for “Foucault pendulum.”) If you watch the pendulum for a while, you will see it slowly knock down one peg after another. When you first see it, if you note which peg has been knocked over, go spend some time looking at other exhibits, and return before you leave. You will probably see that the pendulum has knocked down another peg. (More modern versions have lights that are triggered when the pendulum passes over them.)
Figure 3.4. A. Foucault’s pendulum. (Photo by the author.) B. Diagram showing how Foucault pendulum over the North Pole would swing in one plane but on earth would appear to move in a circle. (Courtesy Wikimedia Commons.)
This experiment is known as Foucault’s pendulum, first demonstrated by French physicist Léon Foucault in 1851. If you set the pendulum in motion on a motionless earth, it would continue to swing back and forth in a single plane, as long as enough energy is supplied to keep the pendulum from slowing down and stopping. But the earth is rotating beneath the pendulum, so as soon as the pendulum starts, the earth moves a certain number of degrees beneath it every hour. This makes the pendulum appear to move around in a circle, but what is really happening is that the pendulum is moving in the same plane and the earth is turning beneath it. Modern geocentrists have no good explanation for this except vague references to Mach’s principle, which concerns the difficulty of describing anything in an absolute reference frame.
3. Coriolis effect: Another even larger result of the earth’s rotation is the Coriolis effect, something I have to explain early in every class I teach about oceanography, meteorology, and climate change, since it is fundamental to the way oceanic and atmospheric currents move around the globe. You can demonstrate it on a kid’s playground merry-go-round (fig. 3.5). If you are on one side of the spinning merry-go-round and try to throw a ball to your friend on the opposite side, the ball will appear to curve away from your friend (to the right if it’s spinning counterclockwise; to the left if it’s spinning clockwise). In simplest terms, this is because your friend is a moving target, so as soon as you release the ball thrown straight at him, he moves away from the point you targeted where he used to be, and the ball will miss him. It appears to curve sideways from your rotating perspective, but it’s actually moving in a straight path; you and your friend are doing the actual moving. (There are several excellent videos demonstrating this online, if you just type “Coriolis” into your browser.)
Figure 3.5. The Coriolis effect. On a merry-go-round, if you throw a ball at a target across the spinning disk, it will miss, since the target is moving away from the spot to where you threw the ball. (Courtesy Wikimedia Commons.)
The same goes for the motion of the currents of air and water around the world. If the world were not spinning, the air would rise from the tropics (where there is an excess of solar heat and the warm ground is heating the air, constantly creating a plume of rising air and low pressure), then move due north and south from the equator to the poles, where it would descend in a permanent zone of high pressure on the poles. But thanks to Coriolis, the air in the Northern Hemisphere curves to the right as it moves, creating the great circulating belts of air in different latitudes known as the Hadley, Ferrel, and Polar cells as well as permanent features like the west-going subtropical trade winds and the east-moving prevailing westerly winds in the middle latitudes.
These same winds drive the surface ocean currents of the world, creating the enormous circuits of water in the tropics and subtropics known as gyres, which move in a giant counterclockwise loop in the Northern Hemisphere and a clockwise loop in the Southern Hemisphere. And the huge cyclonic storms, such as hurricanes and typhoons, always rotate counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere—all due to Coriolis. It even works on smaller scales, such as a giant long-distance cannon. A sniper shooting in the middle latitudes of the Northern Hemisphere would find the shot deflected 7 centimeters (3 inches) to the right if he or she shoots 1,000 meters (about 3,300 feet). Modern geocentrists have no explanation for this global phenomenon.
4. The Chandler wobble: The earth’s rotation is not perfectly smooth. Instead, the earth wobbles on its axis very slightly over long periods of time, a phenomenon known as the Chandler wobble. It makes the stars and galaxies visible in the sky appear to wobble around their normal positions if you observe them over thousands of years. If the earth were stationary, then the modern geocentrist would have to explain why all the stars and galaxies wobble in the same direction and the exact same amount. Furthermore, measurements show that some stars and galaxies are relatively close to us (say, five light-years away), while others are farther (say, ten light-years away). Since the light we see from them started at different times (five years ago versus ten years ago), for them all to wobble the same amount would require enormous coordination and synchronicity, which violates all the laws of physics.
5. Motions of other planets: All the other planets in our solar system are spinning on their axes, something that can easily be observed with a good telescope that can resolve the surface features of Jupiter. If they are all spinning on their axis, why is the earth the only body that is not rotating?
What about proof that the earth is revolving around the sun? Again, the phenomenon is so large in scale that it’s difficult for us to see on earth, but it does provide a number of successful predictions that can be observed and tested.
1. Observations from space: As pointed out before, both modern geocentrists and flat-earthers reject images from space as hoaxes perpetrated by the great conspiracy of NASA, other international space agencies, and the entire worldwide scientific community. Nevertheless, the Hubble and Gaia space telescopes have repeatedly shot images of the earth in different parts of its path around the sun. Even more impressive are recent Mars rover images of a sunrise over the surface of Mars, something that would not happen in the same way if Mars were in an orbit around the earth and the sun were on an inner orbital track.
2. Phases of Venus: As Galileo first observed and published in 1610, Venus has phases (full Venus, half Venus, three-quarters Venus) just like our moon, something that could not happen if both the sun and Venus were orbiting the earth. It makes sense only if Venus is orbiting the sun (fig. 3.6). To get around this problem, modern geocentrists adopt a weird hybrid system proposed by Tycho Brahe as a compromise between geocentrism and heliocentrism in which the sun orbits the earth but the rest of the planets orbit the sun.
Figure 3.6. Diagram showing the phases of Venus, only explicable if the sun is at the center of the orbits of Venus and the earth. (Courtesy Wikimedia Commons.)
3. Retrograde motion: As Copernicus pointed out, the phenomenon of retrograde motion requires extremely complicated and unlikely gyrations, such as Ptolemy’s epicycles (fig. 3.2), to work in a geocentric system but is much more simply explained by heliocentrism. Once again, modern geocentrists fall back on Tycho’s weird hybrid system to explain it.
4. Stellar parallax: For a long time, early astronomers rejected the idea of the earth’s motion around the sun because of the lack of apparent stellar parallax. They reasoned that if the earth traveled in a huge ellipse around the sun (186 million miles or 300,000 kilometers in diameter), the position of the closer stars against the background of the most distant stars should be slightly different when looked at on one side of the orbit and again on the opposite side of the orbit six months later. Since the astronomers could not detect any difference in the stars, they initially rejected the heliocentric model. It turns out that there is a parallax effect, but most of the stars are so much farther away from us than the early astronomers thought that it is hard