The variation in the Earth’s distance from the Sun in astronomical units. An astronomical unit is the average distance of the Earth from the Sun and is approximately 150 million km. Diagram Nick Lomb
Today the Earth is at perihelion, that is, at its closest to the Sun in its slighly elliptical or oval-shaped path around the Sun. As you can see above, the variation is small with a plus or minus variation from the mean of only 1.7%. For other planets the variation can be much higher: for Mars it is 9.4% while for the dwarf planet Pluto the variation is as much as 24.4%.
The velocity of the Earth during 2011. for the calculations behind this diagram see this previous post. Diagram Nick Lomb
The Earth is moving fastest when it is closest to the Sun. This is Kepler’s second law and is purely a consequence of the law of conservation of angular momentum. You can see the law in action if you watch spinning ice skaters who slow down when they extend their arms and speed up when pulling their arms close to their bodies.
Today the Earth is moving around the Sun at the great speed of 109 025 km per hour. If you are careless enough to exceed the speed limit on a public road, you could try explaining to the police officer that your excess speed is trivial compared to the speed of the Earth. Then again, you may just get the officer angry and that would not be a good idea.
The diagram indicates that the velocity will remain high for the next few weeks and then start dropping until the Earth reaches aphelion, its greatest distance from the Sun for the year, on 5 July 2011.
If you think that in July we can all relax knowing that the Earth is moving at its slowest in its annual journey around the Sun, then think again. As well as moving around the Sun, the Earth accompanies the Sun on in its long journey around the centre of the Milky Way galaxy with a velocity about seven times that of the Earth moving around the Sun. Then the Milky Way itself is moving through space. Summing up these motions the Earth is moving through space at a velocity 12 times that of its velocity around the Sun. We are moving at a velocity of about 1.3 million km per hour towards the region of space denoted by the constellation of Leo the Lion.
Even if we are standing still, we are not where we were yesterday and not where we will be tomorrow!