I am a sucker for fascinating on-line video games that do not have a rating or perhaps a aim. On this case, it is a cartoon house simulator to advertise the e book What If? 2, by Randall Munroe, the writer of the xkcd comics.
You may play it by clicking here. (Don’t fear, I’ll wait.)
The sport works like this: You begin off with a rocket on a really small planet. Click on on the rocket to start out, then you should utilize the arrows in your keyboard to activate the thruster, rotate the spacecraft, and discover different planets and some enjoyable issues which can be largely inside What If jokes. That is it. That is the sport. It is foolish and enjoyable, and I like it.
Nevertheless it seems that you should utilize even a easy sport to discover some key ideas in physics.
One of many issues you possibly can see on the preliminary planet is a recreation of “Newton’s cannonball”—Isaac Newton’s thought experiment concerning the connection between a fast-moving projectile and orbital movement. Newton stated that in the event you had been in a position to shoot a really quick cannonball horizontally off a really tall mountain, it is doable that the curve of its trajectory might match the curvature of the Earth. This might make the cannonball fall however by no means hit the bottom. (That is basically what occurs with an orbiting object like the International Space Station), solely the ISS wasn’t shot off a tall mountain.)
Seeing Newton’s cannonball made me assume that I might get my spacecraft to orbit this tiny planet, which might be enjoyable. I attempted it immediately utilizing the arrow keys—with little or no success. Each time I nearly obtained it right into a secure orbit, it wouldn’t final. That made me surprise if the physics interactions that management orbits within the What If world are something like these in the true universe.
The primary physics idea that applies to orbital movement is, in fact, gravity. There’s a gravitational interplay between any two objects which have mass. For instance, there’s a beautiful power between the Earth and the pencil you’re holding in your hand, since they each have mass. If you happen to launch the pencil, it falls.
If you happen to’re standing on the floor of the Earth, the gravitational power performing on the pencil appears to be fixed. Nevertheless, in the event you get that pencil far sufficient away from the Earth (like 400 kilometers away, which is the space at which the ISS orbits), you then would discover a lower within the gravitational interplay: The pencil would weigh much less and take longer to fall.
We are able to mannequin the gravitational power between two objects with the next equation: