Science Buddies: "Ask an Expert"

I am thinking that if the earth moves, then there are part of the earth that the gravity is getting weak. Now I want to know when does the gravity of every continent becomes weaker and how much it becomes weaker. I want to know about this because I am curious and I am not satisfied until I know the answer, but if there are no changes in gravity, then I am still satisfied because that's still an answer.

Hi angelo_limena,

As long as the mass of the Earth stays constant, then the gravitational pull of the Earth will also remain constant. However, there are other forces in the Earth that caused motion. Continents move across the Earth's surface because they are embedded within tectonic plates. These plates move in response to the forces created as new crust is created at mid-ocean ridges and as plates dive down into the Earth's mantle (a process called subduction). You can learn more about the forces that make plates move here:

http://www.geosci.usyd.edu.au/users/pre ... onics.html

Another question about your answer, is that the reason of low-tide and high-tide?

angelo_limena - The rising and falling of the tides is indeed a quality of gravity but in this case it is the varying gravitational attraction of the moon as it revolves around the earth in a varying orbit. You can easily look this up on the web.

Rick Marz