Everyone, from the time they are first able to comprehend the concept of the solar system, is taught that the Earth revolves around the Sun in a roughly circular orbit. While there is no doubt that the Earth, along with the rest of the planets, do indeed orbit the Sun, there is a lot more going on here than simple elliptical orbits. A key fact is always omitted from this rather simple explanation.
The proper way to describe the motion of the Earth as it travels around the Sun would be to describe it as a corkscrew, rather than a circular orbit, and the same is true of moons that orbit planets. If the Earth were to stream smoke behind it in space, like a stun plane doing a demonstration, it would become clear immediately that the motions of planetary bodies are not making circles through space.
Consider that the Sun is in motion through the galaxy. This means that every time the Earth completes an orbit around the Sun, it is not in the same place that it started. It actually completed a corkscrew around the Sun, traveling at the same speed and direction as the Sun through the galaxy. In terms of its galactic position, the Earth is at an entirely new location in the galaxy after every orbit.
Determining exactly how fast the Sun is moving through the galaxy is incredibly difficult. Consider that if the Sun is in orbit around the galactic center, along with all the other stars in our galaxy, that means there is no stationary point of reference in our own galaxy that we could look at in order to give us a means of determining the Sun’s speed of orbit around the galactic center. Scientists have approximated this solar orbital speed to be around ~230 km/s. The Earth’s speed as it corkscrews around the Sun is roughly 29.8 km/s. Of course, the entire galaxy is also in motion through the universe, adding yet another velocity component to orbital motions that is rarely discussed.
Gravitational theories that try to explain these motions based on the assumption of bending space run into problems that are glossed over through the use of relativity. Consider that for the Earth to orbit the Sun as it does, the Earth must “know” where the Sun is going to be in space before the Sun actually arrives at that location. The apparent speed of this “knowing” is faster than the speed of light. From the point of view of an observer on Earth, the gravitational effects of the Sun appear to be instantaneous, rather than moving at the speed of light, which is something that Einstein’s version of relativity says should be impossible. Physicist Tom Van Flandern shows us why this, along with other observations, support the assumption of an aether over the concept of bending space. Which means gravity must be caused by something else…
“The Speed of Gravity What the Experiments Say”, Physics Letters A 250:1-11 (1998)
There is no cause to doubt that photons arriving now from the Sun left 8.3 minutes ago, and arrive at Earth from the direction against the sky that the Sun occupied that long ago. But the analogous situation for gravity is less obvious, and we must always be careful not to mix in the consequences of light propagation delays. Another way (besides aberration) to represent what gravity is doing is to measure the acceleration vector for the Earth’s motion, and ask if it is parallel to the direction of the arriving photons. If it is, that would argue that gravity propagated to Earth with the same speed as light; and conversely.
Such measurements of Earth’s acceleration through space are now easy to make using precise timing data from stable pulsars in various directions on the sky. Any movement of the Earth in any direction is immediately reflected in a decreased delay in the time of arrival of pulses toward that direction, and an increased delay toward the opposite direction. In principle, Earth’s orbit could be determined from pulsar timings alone. In practice, the orbit determined from planetary radar ranging data is checked with pulsar timing data and found consistent with it to very high precision.
How then does the direction of Earth’s acceleration compare with the direction of the visible Sun? By direct calculation from geometric ephemerides fitted to such observations, such as those published by the U.S. Naval Observatory or the Development Ephemerides of the Jet Propulsion Laboratory, the Earth accelerates toward a point 20 arc seconds in front of the visible Sun, where the Sun will appear to be in 8.3 minutes. In other words, the acceleration now is toward the true, instantaneous direction of the Sun now, and is not parallel to the direction of the arriving solar photons now. This is additional evidence that forces from electromagnetic radiation pressure and from gravity do not have the same propagation speed
…anyone with a computer and orbit computation or numerical integration software can verify the consequences of introducing a delay into gravitational interactions. The effect on computed orbits is usually disastrous because conservation of angular momentum is destroyed. Expressed less technically by Sir Arthur Eddington, this means: “If the Sun attracts Jupiter towards its present position S, and Jupiter attracts the Sun towards its present position J, the two forces are in the same line and balance. But if the Sun attracts Jupiter toward its previous position S’, and Jupiter attracts the Sun towards its previous position J’, when the force of attraction started out to cross the gulf, then the two forces give a couple. This couple will tend to increase the angular momentum of the system, and, acting cumulatively, will soon cause an appreciable change of period, disagreeing with observations if the speed is at all comparable with that of light.” (Eddington, 1920, p. 94) See Figure 1.
Indeed, it is widely accepted, even if less widely known, that the speed of gravity in Newton’s Universal Law is unconditionally infinite. (E.g., Misner et al., 1973, p. 177) This is usually not mentioned in proximity to the statement that GR reduces to Newtonian gravity in the low-velocity, weak-field limit because of the obvious question it begs about how that can be true if the propagation speed in one model is the speed of light, and in the other model it is infinite.
If you would like to learn more about what is really going on out there in the cosmos, you can find more information like that which was just presented in this video:
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