Observations of Mercury’s transit haven’t been scientifically important, but that’s not why we do it.
Evening Star
[av_video src=’http://vimeo.com/112644328′ format=’16-9′ width=’16’ height=’9′] When Venus is in the western sky after sunset, it is known as the evening star. It is a time when Venus is most prominently seen. For most of 2015 Venus will be quite visible in the evening as it approaches greatest elongation in May.
Secular and Periodic
More general relativity today. This time a bit on how to calculate the perihelion advance of Mercury in general relativity. When you derive the central force equation for relativistic gravity you find there is an extra term not seen in Newton’s gravity. The extra term is small, but enough to make Mercury’s orbit (any orbit really, but we typically use Mercury as an example) deviate slightly from an ellipse. Since the deviation is small, you can make some broad approximations, get an approximate solution for Mercury’s orbit, then determine the perihelion advance for one orbit.
Small Changes
One aspect of general relativity that always amazes me is the level of precision needed to distinguish it from Newtonian gravity. Take, for example, the advance of Mercury’s perihelion. When you count in the gravitational tugs from the sun and all the planets, Newton predicts Mercury’s perihelion will advance about 531.65 arcseconds per century. When we measure the orbit of …
Icy Hot
Mercury is the closest planet to the Sun. You might think that means it is also the hottest planet, but that award goes to Venus with its thick, heat-trapping atmosphere. Mercury can be listed as one of the hottest planets in the solar system, but also one of the coldest.
Close Encounters
Just how stable is the solar system against close encounters with stray planets? Pretty stable, and we can show that with a bit of computational physics.