Mystery Tug on Pioneer 10 and 11 Probes Is Einstein’s ‘I Told You So’
It’s been a bad year to bet against Albert Einstein.
In the spring physicists had to withdraw a sensational report that the subatomic particles known as neutrinos were going faster than light, Einstein’s cosmic speed limit; they discovered they had plugged in a cable wrong.
Now scientists from NASA’s Jet Propulsion Laboratory have reported that they have explained one of the great mysteries of the space age, one that loomed for 30 years as a threat to the credibility of Einsteinian gravity.
The story starts with the Pioneer 10 and 11 space probes, which went past Jupiter and Saturn in the late 1970s and now are on their way out of the solar system. In the 1980s it became apparent that a mysterious force was slowing them down a little more than should have been expected from gravity of the Sun and planets..
Was there an unknown planet or asteroid out there tugging on the spacecraft? Was it drag from interplanetary gas or dust? Something weird about the spacecraft? Or was something wrong in our calculation of gravity out there in the dark?