Friday, July 3, 2009
Can you believe that the Earth is nearly 3 million miles farther away from the sun today, July 4, than it is on January 3? It's true. July 4 is when the Earth is at Aphelion with the sun. This means that we are at the farthest point away from the sun than at any other time during our orbit around the sun. Earth’s orbit around the sun is not round. Instead, it is more of an elliptic orbit with the sun off to one side at a point called the focus. This means that the Earth is a little bit closer to the sun for part of the year than it is the rest of the time. When the Earth is as close to the sun as it can get we say it is at perihelion which occurs on January 3. None of this has to do with seasons though. Seasons are related to the tilt of the Earth on its axis, not it's proximity to the Sun. If our summer season were to occur when Earth is at perihelion though, the temperature would average 2 to 3 degrees warmer! Another interesting fact is that the sun appears to be about 3% smaller in July than it does in January.