I am a sucker for attention-grabbing on-line video games that do not have a rating or perhaps a aim. On this case, it is a cartoon area simulator to advertise the e-book What If? 2 by Randall Munroe, the creator of the xkcd comics.
You possibly can play it by clicking right 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 begin, then you should use the arrows in your keyboard to activate the thruster, rotate the spacecraft, and discover different planets and some enjoyable issues which are largely inside What If jokes. That is it. That is the sport. It is foolish and enjoyable, and I adore it.
However it seems that you should use even a easy sport to discover some key ideas in physics.
Actual Orbits
One of many options you may see on the preliminary planet is a recreation of Newton’s cannonball, or Isaac Newton’s thought experiment concerning the connection between a fast-moving projectile and orbital movement. Newton mentioned that for those who had been capable of shoot a really quick cannonball horizontally off a really tall mountain, it is potential that the curve of its trajectory might match the curvature of the Earth. This is able to make the cannonball fall however by no means hit the bottom. (That is basically what occurs with an orbiting object just like the Worldwide House 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 instantly utilizing the arrow keys—with little or no success. Each time I virtually received it right into a steady 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 may be a pretty drive between the Earth and the pencil you’re holding in your hand, since they each have mass. In the event you launch the pencil, it falls.
In the event you’re standing on the floor of the Earth, the gravitational drive performing on the pencil appears to be fixed. Nevertheless, for those who 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 will mannequin the gravitational drive between two objects with the next equation:
Illustration: Rhett Allain
