Planet X

Planet X is back in the news – as noted last week. However, some old proponents of Planet X have now had a say – go to http://phys.org/print378535345.html. We even have an article on Planet X in the prestigious journal Monthly Notices of the Royal Astronomical Society . Caltech researchers have revived the idea that Planet X may periodically cause mass extinctions on the Earth. How? Apparently the idea is that it periodically triggers a shower of comets, as it journeys the far reaches of the solar system. This idea was first aired in the journal Nature as long ago as 1985 and astrophysicist David Whitmire, now retired, is eager to regurgitate the idea.