In this, the latest edition of Hero Dad, we tackle another question about how the world works for your sprogs. How does gravity work?
The kids will obviously ask this question in a different form. But any enquiry about why we don’t just float off into oblivion, or why a ball hits the ground will certainly do.
How does Gravity Work? Isaac Newton
We’ve all heard the story about an apple falling from a tree onto Newton’s head. While we don’t know if such an event actually happened, we do know that something sparked Newton’s interest in gravity.
In the 1680s the English Physicist published his Theory of Gravitation. It stipulates that gravity is a force of attraction between all particles in the universe. This attraction will cause two objects to naturally come together, if there is no other force to stop it.
The more massive the object, the stronger the force of gravity will be. This means a huge ball of matter like Earth affects enough force upon us that we don’t just fly away across the solar system.
This is important, because without gravity, there would be no solar system. Nor any stars or universe as we know it at all for that matter.
The force of gravity acting upon an object also determines it’s weight. That’s why a dense rock weighs more than a bag of feathers the same size. The particles within the rock have more mass and thus their attraction to earth is greater.
How does Gravity Work? Albert Einstein
The next person that needs to be mentioned in any exploration of gravity is Albert Einstein. He contributed an alternative view of gravity in the early 1900s, part of his famous Theory of General Relativity.
Interestingly, under Einstein’s interpretation, gravity is not a force at all. Rather, it’s just a natural behaviour of objects moving through the pits and bends in space-time. I can understand if that sounds difficult to comprehend.
In general relativity the mass of an object causes it to have an effect on space-time. What we need to understand, is that space-time is another dimension all on it’s own. It can be bent, stretched, contracted and squashed like any other object.
Under physical laws, two objects with no external forces acting upon them travel across the straightest possible line. Einstein said that when two objects appear to come together, it’s not because of gravity, but because a curve in space time causes the straightest possible path to be a collision course.
How does Gravity Work? Other Theories and Facts
Both of these explanations of gravity mean that everything in the universe has a gravitational field. The mass of the object determines how strong it is. That’s probably the easiest way to answer the question for the kids.
Another interesting observation based on this is that a falling object pulls against the earth, just as the earth pulls against the object. Earth wins obviously, just because of how damn big it is.
There have been particles suggested called Gravitons, but these have never been found. There’s a lot of work going on with gravitational waves too, the first of which were detected from a distant black hole very recently.
Work to understand gravity is on-going. We don’t yet have a fully tested theory on how it works, but like everything in science, it’s just a matter of time (Pun intended).
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Have you had any difficult questions posed by the sprogs recently?