home observation science solar system stars our galaxy cosmology astrobiology exoplanets astrophotography

Earth - Introduction

The South-East Asian Tsunami of December 26, 2004 has painfully reminded us that we live on a dynamic planet.

The Earth is a very beautiful place to live with an atmosphere that is capable of sustaining life and a temperature range that allows for the 3 states of water (solid, liquid, and gas). But these life sustaining substances come at a price.

It is important to understand that while tragedies like the tsunami are devastating, they are a necessary part of the continual evolution and life sustaining benefits of the planet Earth. Storms allow for the cycle of water, land provides plant life to expel oxygen, the oceans swallow up carbon dioxide and plate tectonics (the movement of the land masses that cause earthquake, volcanoes, and tsunamis) keep the surface renewed and free of long term cratering as a result of meteorite impact.

As tragic as these events are, they are necessary for the maintenance of life. Click here to view the NOAA high resolution computer simulated QuickTime movie of the Indonesian tsunami of December 26, 2004.

Not all tragedies are natural, some are man-made. I am talking about the damage to our environment as well as the atmosphere and Ozone layer. I won't preach about that here, but here are a few places you can visit:

The Earth - A Quick Summary: (More information can be found on the Earth Fact Sheet)

Average Distance from Sun: 1.496x108 km
Eccentricity of Orbit: 0.017
Average Orbital Speed: 29.79 km/s
Orbital Period: 365.256 days
Rotational Period: 23.9345 hours
Inclination of Equator to Orbit 23.45
Diameter: 12,756 km
Mass: 5.974x1024 kg
Average Density: 5515 kg/m3
Escape Speed: 11.2 km/s
Albedo: 0.39
Maximum Surface Temperature: 60 C
Minimum Surface Temperature: -90 C
Average Surface Temperature: 14 C
Atmospheric Composition 78.08% Nitrogen
20.95% Oxygen
0.035% Carbon Dioxide
1% Water Vapor

A magnetic field surrounds the Earth which helps to protect us from solar storms. The presence of the magnetic field is a bit of a mystery as the Curie temperature of Iron is 770 degrees Celsius. What this means is that when Iron reaches this temperature, it looses all magnetic properties.

(Click Image for Video)

Despite this fact, a magnetic field does exist. It is believed the current is generated by a dynamo effect - that is the liquid molten outer core rotating around the solid inner core.

There is evidence by the permanent magnetization of rocks that the earth's magnetic field has reversed 171 times in the past 71 million years (video care of Swinburne Astronomy Online).


Unfortunately I have seen several websites that claim a magnetic field reversal will cause catastrophic changes to life on Earth. If this were true, then there would have been 171 extinction events on Earth - we would not have evolved! We are quite safe from any event such as this.

One physically observable feature of the magnetic field are the Aurora - solar particles are funneled by gaps in the magnetic field and interact with Earth's ionosphere resulting in an impressive light show.


The magnetic field does protect us from solar wind, creating a magnetopause - a sort of shock wave. In the image above, notice the cusp. This is where some of the solar particles reach our upper atmosphere. This is the location of the aurora.

Back to Top

Search | Site Map | Buy Stuff - Store | Appendix
©2004 - 2013 Astronomy Online. All rights reserved. Contact Us. Legal. Creative Commons License
The works within is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.