The Earth, By Marty Wyatt

Let me introduce myself. My name is Marty Wyatt and I teach astronomy at Comanche High School. Astronomy is such a broad science that pretty much changes daily. New information streams to us constantly. This article and those that follow contain information I have learned or researched and by no means is written in stone or to be taken as the absolute truth, simply the science as I understand it.

This piece of rock we live on, Earth, is a pretty amazing little world. Small compared to some the planets in our Solar System, but largest of the 4 inner or terrestrial (rocky) planets. Measuring about 8,000 miles in diameter (25,000 miles in circumference) it lies roughly 93 million miles from the Sun. This distance is also known as an astronomical unit (AU). It is much easier to talk about distances to other planets in single or double-digit AU rather than hundreds of millions of miles. Example: Mars lies about 1.5 AU from the Sun or 142,000,000 miles.

Our Earth makes one lap around the Sun in just over 365 days. The tilt of its poles is at 23 degrees from a line perpendicular to the Sun. As our planet revolves around the Sun the axis always points in the same direction. Luckily, for us in the northern hemisphere, it points very close to a star in our sky, Polaris, the North Star. As we make our trip around the Sun different parts of the globe receive varying amounts of sunlight. During June, July, and August the north pole of the Earth it tilted toward the Sun. Therefore, the northern hemisphere receives more direct rays from the Sun and we have more daylight hours (summer time). During December, January, and February the north pole points away from the Sun. The northern hemisphere receives less direct rays and we have less daylight hours (winter time). Our seasons are relatively predictable due to the constant axial tilt.

The orbits of all planets and moons are ellipses, slightly oval. At times the Earth is a bit closer to the Sun and at times it is further away. You might think, mistakenly, that during the summer months in the northern hemisphere we are closer to the Sun and further from the Sun in the winter months. Actually the opposite is true. The seasons here on Earth do not occur on the first day of the month. The summer solstice occurs on about June 21. This is when the Sun has reached its furthest point to the north. The autumnal equinox occurs on about September 21 and is when the Sun is directly over the equator. The winter solstice occurs about December 21 and marks the Suns furthest point south. The vernal equinox (spring) occurs about March 21 and is when the Sun is again directly over the equator.

There is another special little characteristic of Earth. That property is responsible for us being able to continue to survive here. The core of the Earth is molten iron and other metals and since the Earth is spinning a magnetic field is produced. Not only does that help us with directions using a compass in that it creates a magnetic north and south pole, it protects our atmosphere from particles given off by the Sun known as the solar wind. This magnetic field deflects the particles given off by the Sun that could “sandblast” away our atmosphere. By protecting our atmosphere the atmospheric pressure is maintained and water is not boiled away. If we were to lose our atmosphere, all the surface water would evaporate and Earth would become entirely devoid of surface water.

Please feel free to contact me at if you have any questions. I may not know the answer, but I will try my best to find it. I will respond to your email privately and hope to be able to post your question and the answer in the Chief.

Marty Wyatt

Astronomy Teacher

Comanche High School

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