# Time dilation and the pioneer spacecraft

1. Jun 21, 2008

### Freyman

I've been thinking about this for a while but never got around to asking this. This has two parts.

First, I understand that time and matter are closely related and that time slows down when in proximity to more matter. So, time on the moon is faster than time on earth and time on Jupiter is slower than time on earth.

Second, I'm under the impression that the pioneer spacecrafts, the ones that were launched in 1973 and left the solar system are both accelerating in an unforeseen manner. Could this observed speed increase possibly be due to the lack of relative proximity to matter and time is becoming faster around the pioneer spacecrafts..hence the speed increase?

Let me explain. Lets say it takes 5 seconds to cross from point a to point b at a speed of 1 kph. While it still takes the same 5 seconds to cross from point a to point b at a speed of 1 kph, say time is now faster due to lack of matter in proximity wherein 5 seconds from point a to point b is observed from earth as 3 seconds. While it still took 5 seconds to go from point a to point b, I observed from earth that only took 3 seconds b\c of the way time works, so it appeared faster.

Basically, I assume this due to the causal association that time slows when in proximity to matter and the opposite in conditions of less matter..so the obvious lack of matter outside to solar system compared to within it should cause time to go faster, hence observable speed should increase from earth of any moving objects.

This brings a lot of other interesting possibilities too..like if something moving at just under the speed of light in conditions where time is faster could be observed from earth as moving faster than light even though the object itself is only moving at just under the speed of light because of the way time works. Also, matter between galaxies would appear from earth as moving very very fast b\c of a relative lack of matter compared to within galaxies.

Or..am i completely offbase with all this?

Last edited: Jun 21, 2008
2. Jun 21, 2008

### yuiop

To a certain extent you are right. To an distant observer high above a planet with a strong gravitational pull an object moving upwards from the surface, with constant velocity relative to a series of stationary local markers would appear to be speeding up. The converse is true and to the observer on the surface the object would appear to be slowing down. The effect is a slight additional acceleration towards the centre according to an observer near the centre. The problem is that the pioneer data has been re-analysed taking General Relativity into account which should include the effect you describe and yet the anomally still remains. Not having access to the raw data we have to assume they did the analysis correctly.

Another issue is that far out in the solar system are large meteorite fields that largely have a disk distribution. The gravity at the edge of a disk is a function of GM/R rather than the usual GM/R^2 and drops off less rapidly than a purely spheriacal distribution of matter. One has to assume that hese effects have also been taken into account but it is worth noting that no one is exactly sure of the total mass, extent and distibution of the meteor fields at the furthest reaches of the solar system.