http://timestranscript.canadaeast.co...article/907407
Earth will be its closest to the sun today
Published Saturday January 2nd, 2010
So, why are we not getting summer weather?
Charles Perry
The winter is the time of the year when the Earth is its nearest to the sun.
In fact, early this evening, the Earth will be the closest to the sun than it will be at any other time in 2010.
This is when the Earth is at perihelion -- namely, when a body orbiting around the sun is at its closest to the latter, says Daniel LeBlanc of Dieppe, president of the Beauséjour Astronomy Club.
When it is furthest from the sun, the Earth is said to be at aphelion, said LeBlanc. Although the date for both will vary from year to year, the Earth in the Northern Hemisphere will always be closest to the Sun in January and the furthest away in July. This fact surprises most people who are not involved in astronomy, said LeBlanc.
If we are the closest to the sun this time of the year then why are we not getting our warmest weather -- summer-like conditions, people ask. Similarly, if we are the furthest from the sun in July, then why are we not getting the coldest temperatures of the year at that time, he said.
What is happening, weather-wise, appears on the surface to contradict what is occurring astronomically.
And this paradox does not perplex just the general public, noted LeBlanc.
He said a poll done at Harvard University asked 100 students whether the Earth was warmer when it was the closest to the sun or when it was the furthest away. "And most of the Harvard students also got it wrong, feeling it would have to warmer when the planet was the closest to the sun."
What people overlook, he explained, is the fact that the temperatures and the seasons are not affected by the proximity of the Earth to the sun or even the rotation of the planet.
It is the tilt of the Earth that determines the climate, said LeBlanc. The Earth has a 24.5-degree tilt on its spin axis.
When it is at perihelion in January, it is tilted away from the sun in the Northern Hemisphere, said the astronomy club president. As a result, he said the sunlight is not "getting a direct hit" on the Earth's atmosphere.
But when it is at aphelion in July, LeBlanc said it is tilted toward the sun. This means that the Earth is positioned, he said, to get the full impact of the sunlight rays.
Along with the tilting of the sunlight, LeBlanc said various other factors are involved in the proximity to the sun not affecting climates in the Northern Hemisphere.
"There are a lot of things happening," he said. "There are the different natural sources shaping the combinations of winds in the Earth and the different wind cycles that also play a part."
Today, the Earth will be 149,597,870 kilometres (92,955,807 miles) from the sun -- the closest proximity the two celestial bodies will be this year.
Earth will be its closest to the sun today !
