July 6, 2010, is the date of our annual "aphelion" -- the time of year when the earth is furthest from the sun. That's right... It's the northern hemisphere's summer, and we are FURTHER away from the sun on this date than we are at any other time of the year! We're 94.5 million miles away from the sun, to be exact. On January 3rd, we are "only" 91.4 million miles away from the sun. This time of year is called "perihelion."
The reason we are warmer at this time of year than in January is because the northern hemisphere is tilted towards the sun's direct light at this time of year. In January, the northern hemisphere is tilted away from the sun's direct light. Another way to say it is the sun appears to be higher in the sky in the summer than it does in the winter. This is a much more important factor than the (percentage-wise) small, temporary fluctuation in distance we are away from the sun. --TS
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