On the Behaviour of Atomic Clocks during the 1999 Solar Eclipse over Central Europe
 

Previous Observations

Previously some scientist have found that solar eclipses can have an influence on the motion of pendulums and the relative pace at which clocks are ticking. While the pendulum results are not conclusive, i.e. some scientist saw these effects while others did not make such observations, the effects on clocks have been observed by one chinese group of researchers (Zhou et al.) so far during previous eclipses. Their clocks have been adjusted to precisely the same time before the eclipse. After the eclipse they found that some of their clocks where off by as much as 65 micro seconds (1 millionth of a second). This may sound like a very short time, but it is well within the accuracy of current state of the art atomic clocks.

Possible Explanations

Different explanations have been offered to these effects that were connected with some yet unknown features of gravity. It is well known that gravity influences the pace of time and therefore can change clock rates. But this effects any clock in the same way provided they are located in the same place and therefore feel the same gravity. So according to the classical theory of gravity Zhou et al. should not have seen an effect on their clocks.

A new Experiment

Because it is certainly no good science to say "if this effect should not be there, we shouldn't look for it" we repeated this experiment during the total solar eclipse on August 11th 1999 over central Europe. We have compared four different atomic clocks that where located within the path of totality. We found no relative time deviations between the clocks that where larger than 60 nano seconds (1 billionth of a second). The limit of 60 nano seconds was set by the equipment that we used. This means that we have seen no effect, not even one that would be 1000 times smaller than reported by the chinese group. Since we now don't think that effect (at least on the clocks) exists we do not really need to think about possible explanations.

What's the Problem with Gravity?

Gravity is the only force in nature that resists a quantum mechanical description. Quantum mechanics is the most successful theory in history of physics. There is no known failure of this theory. Even when it comes to the most precise experiments done so far the theory of quantum mechanics can still reproduce all the figures measured in the laboratory. The big problem, however with this theory is (among some philosophical issues) that there are some things in nature where quantum mechanics does not say anything about it. On of these things is Gravity. So one very interesting question is: Does the classical theory of gravity do the job completely or do we need quantum mechanics to describe it correctly? So far there is no known failure of the classical theory of gravity which is called general relativity. Any other classical theory has known limitation where it simply fails. That is why it is interesting to search for possible violation of the classical description of gravity. Our experiments however suggest that there is no problem with atomic clocks during solar eclipses.
 
 


Last modfied 14.12.1999