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Strategies & Market Trends : VOLTAIRE'S PORCH-MODERATED -- Ignore unavailable to you. Want to Upgrade?

To: Jill who wrote (17841)	11/19/2000 10:01:52 PM
From: bela_ghoulashi	Read Replies (2) \| Respond to of 65232

Gravity: Faster than the speed of light This is new information to bland, and he has not had time yet to absorb it all, but it is fascinating and highly evocative in its implications: Gravity has some curious properties. One of them is that its effect on a body is apparently completely independent of the mass of the affected body. As a result, heavy and light bodies fall in a gravitational field with equal acceleration. Another is the seemingly infinite range of gravitational force. Truly infinite range is not possible for forces conveyed by carriers of finite size and speed – a point we will elaborate in Part II. Another curious property of gravity is its apparently instantaneous action. By way of contrast, light from the Sun requires about 500 seconds to travel to the Earth. So when it arrives, we see the Sun in the sky in the position it actually occupied 500 seconds ago rather than in its present position. (Figure 1.) This difference amounts to about 20 seconds of arc, a large and noticeable amount to astronomers. From our perspective, the Earth is standing still and the Sun is moving. So it seems natural that we see the Sun where it was 500 seconds ago, when it emitted the light now arriving. From the Sun’s perspective, the Earth is moving. It’s orbital speed is about 10-4 c, where c is the speed of light. So light from the Sun strikes the Earth from a slightly forward angle because the Earth tends to “run into” the light. The forward angle is 10-4 radians (the ratio of Earth’s speed to light speed), which is 20 arc seconds, the same displacement angle as in the first perspective. This displacement angle is called aberration, and it is due entirely to the finite speed of light. Note that aberration is a classical effect, not a relativistic one. Frame contraction and time dilation effects are four orders of magnitude smaller, since they are proportional to the square of the ratio of speeds. Now we naturally expect that gravity should behave similarly to light. Viewing gravity as a force that propagates from Sun to Earth, the Sun’s gravity should appear to emanate from the position the Sun occupied when the gravity now arriving left the Sun. From the Sun’s perspective, the Earth should “run into” the gravitational force, making it appear to come from a slightly forward angle equal to the ratio of the Earth’s orbital speed to the speed of gravity propagation. This slightly forward angle will tend to accelerate the Earth, since it is an attractive force that does not depend on the mass of the affected body. Such an effect is observed in the case of the pressure of sunlight, which of course does depend on the mass of the affected body. The slightly forward angle for the arrival of light produces a deceleration of the bodies it impacts, since light pressure is a repulsive force. Bodies small enough to notice, such as dust particles, tend to spiral into the Sun as a consequence of this deceleration, which in turn is caused by the finite speed of light. This whole process is called the Poynting-Robertson effect. But observations indicate that none of this happens in the case of gravity! There is no detectable delay for the propagation of gravity from Sun to Earth. The direction of the Sun’s gravitational force is toward its true, instantaneous position, not toward a retarded position, to the full accuracy of observations. And no perceptible change in the Earth’s mean orbital speed has yet been detected, even though the effect of a finite speed of gravity is cumulative over time. Gravity has no perceptible aberration, and no Poynting-Robertson effect – the primary indicators of its propagation speed. Indeed, Newtonian gravity explicitly assumes that gravity propagates with infinite speed. metaresearch.org metaresearch.org