Wednesday, March 29, 2006
Wednesday, March 22, 2006
Vernal Equinox
Today is Vernal Equinox
You know how we say that Earth is 23.5 degrees tilted. Well that is with reference to the Sun. The Earth's orbit plane about the Sun (called the Ecliptic ) is tilted by about 23.5 degrees.
The Earth's tilt angle with respect to the Sun (Declination Angle) changes depending on the day of the year.
Here is the equation to calculate the declination angle:
23.45 * sin((DayNumber+284) * 360/365)
Today's Day Number is 31 (January) + 28 (February) + 22 (March) = 81
Declination Angle is zero!
So today, at Noon, Solar Time which ever part of the world you are at, the Sun will be directly above you!
Earth Day also happens to fall on Vernal Equinox!
Here are some useful links:
You know how we say that Earth is 23.5 degrees tilted. Well that is with reference to the Sun. The Earth's orbit plane about the Sun (called the Ecliptic ) is tilted by about 23.5 degrees.
The Earth's tilt angle with respect to the Sun (Declination Angle) changes depending on the day of the year.
Here is the equation to calculate the declination angle:
23.45 * sin((DayNumber+284) * 360/365)
Today's Day Number is 31 (January) + 28 (February) + 22 (March) = 81
Declination Angle is zero!
So today, at Noon, Solar Time which ever part of the world you are at, the Sun will be directly above you!
Earth Day also happens to fall on Vernal Equinox!
Here are some useful links:
Subscribe to:
Posts (Atom)