CrackerJack's reply
... the Shapiro Effect decreases with the inverse of the logarithm of distance, not the inverse of the distance. And this has supposedly already been verified by observations of the Mariner spacecrafts.
The effect on satellites Pioneer 10 and 11 would also be noticeable as they are the furthest craft from earth. In fact there is an anomaly in their oribits -- see
Spacecraft anomalies put gravity to the test:
Indeed, the spacecraft move as if they were subject to a new, unknown force pointing towards the Sun. This force imparts the same constant acceleration, ap, of about {10e-7 cm/s/s} to all three spacecraft, about ten orders of magnitude less than the free-fall acceleration on Earth.
The third satellite mentioned is Ulysses - "on an elongated orbit that roughly bridges the orbits of Jupiter and Earth" -- Note that these satellites are outside the orbit of the earth while the Mariner satellites were inside earth's orbit (10 going to Mercury), and thus are much more relevant to any discussion of long distance effects of gravity.
Also see
The Pioneer anomaly : a bulk scalar field ?
Authors considered the possibility that the origin of ap is:
- an effect of a modification of gravity like
- the addition of a Yukawa force to the Newtonian
- Milgrom’s proposed modification of gravity
- If the cause is dark matter (DM), consistency with the accuracy of the ephemeris implies an amount less than a few {10e-6 M} within the orbit of Neptune.
... ... ...
So, it may be of interest to look for new physics and try to make some predictions that can be tested in future missions (Pluto Express mission, Solar Probe mission).
As we have shown, a bulk scalar field external to gravity and which respects the WEP, may provide a solution to both the anomalous acceleration observed on remote spacecraft and the absence of a comparable effect on planets, comets or asteroids.
In other words we are talking about a measured gravity anomaly effect on the order of dark matter within our solar system, but not one sufficient to cause the Shapiro effect. That the same anomaly in gravity that gives rise to the concept of dark matter is observed within our solar system should be expected, as this is consistent with the standard model.
CrackerJack's reply
I don't quite see your point about the correlation of time for particles with mass and the light. The gravity is affecting the light after it has left the emitter and continues to affect it as it travels through empty space
The effect of gravity is proportional to the mass of the object, thus those with significant mass can be predicted to arrive later than those with little or none and you can chart out which particles should arrive in what order and at what relative intervals. The first to arrive are the light\radio waves, consistently with the intervals to the others predicted by their having 0 mass and 0 gravitational attraction. Remember that for relativity the effect of gravity on light is not from attraction of the light particle but from the warping of space by gravity about the objects with mass -- this is why the prediction of light being bent by gravity was a surprise and a confirmed surprise -- warping that includes time dilation effects and causes the space to act as a "gravitational" lens.
If the effect of gravity was as claimed by the Shapiro effect, then the intervals of the arrival of particles would be different than what is predicted by the standard model -- and what is observed (which does fit the standard model (and the ekpyrotic model)).
CrackerJack's reply
... if the Shapiro Effect is something to be reckoned with, and if the BBT is also considered correct, then the Shapiro Effect could have a drastic effect on how we interpret certain observations. For instance, if we use the current estimates of the expansion rate as being correct, it would mean the universe is much younger than what most cosmologists say it is.
It isn't.
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