MadSci Network: Earth Sciences
Query:

Re: Can Earth be destroyed by a giant crack or can it be burned by the sun?

Date: Mon Jun 20 21:03:34 2005
Posted By: Jennifer Anderson, Geological Sciences
Area of science: Earth Sciences
ID: 1118170465.Es
Message:

Those are very interesting and complex questions! I hope that I can help you out!

1. Can the Earth be destroyed by a giant crack, or what keeps the Earth from just cracking in half? This is an interesting question because there are earthquakes on Earth, which happen when two large pieces of the Earth’s crust slide against each other along what can be thought of as a giant crack. In fact, maybe you have even felt an earthquake! But I assure you that the Earth is quite safe from cracking itself in half, even in the biggest earthquakes that have been measured and the biggest earthquakes that we can imagine. This is because the Earth is so very very very big compared to any crack that makes an earthquake. The Earth is HUGE! And the Earth is made up of a lot of stuff, like rocks and trees and water, all of which has mass (just like you).

All the mass of the Earth is being pulled toward the center of the Earth by gravity and all that mass weighs a lot. So the inside of the Earth is under a lot of pressure because all the mass is packed together tightly. If you sat down and put a heavy rock on your stomach, the added mass of the rock would press down on your stomach and you would feel that pressure. Just imagine how much pressure there would be if you had a pile of rocks over 6000 km high on your belly! That would be like the center of the Earth because the radius of the Earth (the distance from the surface to the very center of the Earth) is over 6000 km. All those rocks are pushed together tightly and so no earthquake, no matter how big or strong or even scary that it might feel, will ever be strong enough to break through the Earth. The Earth will never crack in half by itself because it is being held together by gravity -- a very powerful force!

2. Can the Earth be burned up by the Sun? This is a really great question! The Sun is very hot on its surface – about 6000 degrees Celsius (almost 11,000 degrees Fahrenheit). But the heat you feel from the Sun depends on how far away from the Sun you are, just like the heat from a fire. If you are very near the fire, it is very hot, but if you are far from the fire, it is cooler. The Earth happens to be far enough from the Sun that the average temperature is around 7 degrees Celsius (or 44 degrees Fahrenheit). Because the Earth has an atmosphere, that helps keep the surface warmer (like a blanket) and there are other effects that increase or decrease the surface temperature of the Earth, so we actually get a nice range of temperatures on the surface. In fact, the Earth is unique in our solar system because it is the only planet at the right distance from the Sun for water to be either a gas (like in the air we breathe), a liquid (like what we drink), or a solid (like ice and snow). This special location in our solar system is very important and one of the main reasons that Earth has lots of living creatures. So the temperature that we feel from the Sun on the Earth is not hot enough to burn up the surface of the Earth. We would need to be much closer to the Sun to experience such hot temperatures! Even Mercury, the closest planet to the Sun, is not so hot that the rocks on its surface burn, but it is over 177 degrees Celsius (350 degrees Fahrenheit) – now that’s HOT!


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