I Must Inform You of the Gravity of the Situation

Today’s reading in Physics and Technology for Future Presidents really got me thinking about gravity.  When it said, “They misunderstand several important concepts, including weightlessness, orbits, and the behavior of gravity,” I hadn’t realized that I was as wrong as the people mentioned in this.  The first concept that is said to be commonly misunderstood is weightlessness.  I hadn’t realized that in orbit, the reason astronauts seem weightless isn’t because they’re out of range of Earth’s gravity (if they were, they wouldn’t be in orbit of it), but because they’re moving so fast.  I do wonder what the actual distance is to escape all of Earth’s gravity.

On the behavior of gravity, I remain confused on a concept that was introduced.  According to Newton’s Third law, if something exerts any amount of force on another object, that object exerts the same amount of force back on the original object.  Therefore, since I weigh 110 lbs, Earth pulls me down with that amount of force, but I also pull Earth with that amount of force.  If Newton said it, I believe it, but I still don’t understand why.

Unfortunately, I believe that is one of the biggest and most confusing questions in all of science.  Why?  It has a huge amount of answers, and oftentimes, require huge amounts of knowledge to fully understand.  With my knowledge of physics, it’s better just to accept it for now.

Another point I found interesting was the idea that if the gravity of the sun were eliminated, Earth would simply fly in a single direction at its orbital speed forever until it hit something.  This, of course, is an obvious idea if one thinks about inertia, but of course, being the person that I am, I didn’t think about that, and assumed that Earth would simply scatter.  This concept is illustrated perfectly by the sling (shown at the left).  The sling is swung around, until the rock in the pouch at the end is let go.  It flies straight from then until it hits the target.  The Earth’s orbit around the sun is the same, except that instead of having a string, the forces of gravity combined with high velocity create a bond between the two that holds them together.

The final point I found interesting was the idea of denser objects having greater gravity force than objects with low density, such as oil.  Due to the fact that Earth is heterogeneous, judging its surface by examining the force of gravity in different areas can lead to the discovery of various elements.  I found this very interesting, especially with the frequent discovery of new resources today, possibly due to this in some cases.  Is it possible perhaps that this difference in gravity can be felt from high altitudes, such as satellites, or is it too small to be felt from that altitude, as we saw by calculating the difference in the force of gravity at Earth’s surface and 100 miles above the surface (5%)?  I hope to learn more about my questions as the readings continue.


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