Free 13 Things That Don't Make Sense by Michael Brooks Page A

Nieto says. Anderson also thinks the Pioneer anomaly is most likely a false alarm. But he is leaving a door open for something
     revolutionary because he can’t help but notice the parallels with another anomaly, one that Einstein inadvertently solved
     when he came up with general relativity.
    IN 1845 Urbain Jean Joseph Leverrier, the French astronomer best known for the discovery of Neptune, calculated that Mercury’s
     elliptical orbit around the Sun would experience a shift in its perihelion , the point of closest approach to the Sun, with each revolution.
    This shift, or precession , is due to the gravitational pull of the other planets in the solar system. It is not unique to Mercury; the perihelion of
     every planet’s orbit exhibits a similar precession. Mercury’s, however, was not what it should have been. When Leverrier worked
     out, using Newton’s laws, how big the shift should be, it didn’t match the value astronomers had worked out from their observations.
     The discrepancy was forty-three seconds of an arc—just a little more than one hundredth of a degree—per century.
    Noticing such a tiny anomaly was a hugely impressive feat for the time, equivalent to measuring the diameter of a penny from
     thirty miles away. But no one was patting themselves on the back; faced with the discrepancy, the scientists had no choice
     but to find an explanation. Astronomers tried various ad hoc fixes. Leverrier, perhaps inspired by the way he had been able
     to predict Neptune’s existence by reference to other planetary orbits, thought the Mercurial discrepancy must be a sign that
     there was another planet waiting to be discovered. Others suggested the Sun had some kind of uneven weight distribution, or
     that dust clouds in between the Sun and Mercury were affecting the orbit. Nothing worked. It was only in 1915, when Einstein
     pointed out that a massive object like the Sun would warp the space around it, that an explanation for the anomaly was found.
    Using his equations for general relativity, Einstein worked out that the warp in space, added to the tug of the other planets,
     would give a value for Mercury’s perihelion precession of 42.9 arc seconds per century. It was a weighty validation for Einstein’s
     newly minted theory and led to its immediate acceptance. And, according to John Anderson, it’s a lesson for those who would
     discount the potential impact of the Pioneer anomaly.
    If the explanation for the Pioneer anomaly is mundane, Turyshev’s careful approach will almost certainly find it. If the explanation
     is something extraordinary, however, even the most meticulous sifting through the landscape of dull possibilities won’t help.
     Mercury has taught us that ruling out the ordinary is not always going to lead to the answer.
    Perhaps Pioneer doesn’t offer enough data to build a picture of another force in the universe, Anderson says. But even if
     no one uses the errant flight path to create a breakthrough in physics, Pioneer could at least provide the validation for
     a theory developed by other means. Einstein didn’t create general relativity because of the problem with Mercury’s orbit,
     but the problem was hugely significant in proving Einstein’s radical ideas were right. If the orbit of Mercury provided the
     perfect validation for one of the most important breakthroughs in science, perhaps the Pioneer spacecraft will one day do
     the same.
    IS some unforeseen breakthrough coming? So far we have gathered evidence that the constituent parts of the universe are largely
     unknown, that the four-hundred-year-old law of gravitation could be in need of a rewrite, and that an unknown force might
     be responsible for pushing two of our spacecraft—craft that were predicted to offer a test for Newton’s law of gravitation—off
     course. Kuhn might call this a sign of impending crisis. It certainly seems, as the foundations creak a little, that our current
     picture of the cosmos might