Earth closing on the sun
Despite Utah's frigid temperatures this time of year, come Jan. 2 at 5 p.m. MST, Utah and the rest of the Earth will be as close to the Sun as we're going to get this year. Astronomers refer to this point in Earth's orbit as perihelion.
"While it may seem counter intuitive that we're coldest when we're closest to the source of the heat, there is a simple explanation." says NASA Solar System Ambassador to Utah Patrick Wiggins.
The difference between furthest from the Sun and closest is actually quite small so the change in distance has little effect on temperature. The real culprit is the tilt of the Earth.
Many might remember that Earth globes are usually tilted. That's the way it is with the real Earth too, tilted just a bit over 23 degrees from straight up.
"During this time of year," explains Wiggins, "we in the northern hemisphere are tilted away from the Sun, meaning the Sun stays pretty low in our sky and doesn't stay up nearly as long as it does in the summer. This makes for short, frigid days."
On the other hand, during the toasty days of July Earth is actually furthest from the Sun. But at that time we in the north are tilted towards it, so the Sun is much higher in our sky and stays there a lot longer.
"Happily," jokes Wiggins, "for Utahns who don't like the current frosty temperature there is a simple fix. Just head for the southern hemisphere where the seasons are reversed and it's pretty hot down there just now."
For additional astronomical information log on to Wiggins' Solar System Ambassador website at http://utahastro.info.