Wednesday, April 23 2014, 09:23 AM MDT
Good Question: How is Autumn Start Minute Determined?
(KUTV) On September 22, Autumn began at exactly 2:44 PM Mountain Time. Frank Salisbury from Logan asks, "How can they say that fall (or spring) starts at some exact time: hour & minute?"
"Fall begins when earth's axis is at a 90 degree angle to the direction of the sun," says Clark Planetarium education director Robert Bigelow. "So the sun would be exactly over the equator on the earth."
That is a fairly simplistic explanation of what takes a very lengthy formula to calculate. Within the book, Explanatory Supplement to the Astronomical Almanac, there is a formula long formula which allows scientists to calculate how the gravitational force of every planet in earth's solar system has on the earth. In order to figure out fall's timing, Bigelow says that, not only the sun and the earth must be considered but also how every other planet's gravity affects the earth.
But that's not all; Scientists also need to calculate orientation of earth's axis, which Bigelow describes as a “simper equation."
Combined, those two formulas allow scientists to determine the exact minute that Summer becomes Fall. The equations were derived by a couple of names you have probably heard: Issac Newton and Albert Einstein.
Thanks, Frank, for the good question. If you have a question you would like answered, contact Matt Gephardt at (801) 839-1250 or Gephardt@kutv.tv. Questions are answered every Friday on 2News at 10.
By Matt Gephardt
Edited by Ryan Malavolta
Photography by Mike Sadowski
(Copyright 2013 Sinclair Broadcasting Group)