What are the basic physics of the portal gun? [closed]

Since a real portal gun is impossible, this answer only addresses the physics within the game itself.

First off - not all surfaces will accept a portal. Typically, a portal can be placed upon any light-colored flat surface, whereas an uneven or dark surface cannot be used in this way.

Portals are bi-directional - there is no specific entry or exit. This makes it easier to move since you can place the blue portal, then the orange one, move through the blue portal, and then place it elsewhere before moving back through the orange portal.

Portals have a small local bubble of physics - this is to ease movement through the portal and back into the world beyond - especially if one or both portals are on a moving surface. If you place two portals on the floor and/or ceiling so that their long axes are at 90 degrees to each other and pass through, you will be turned 90 degrees.

If you put two portals into the ground, and jump into one you will be pulled down by the world physics into the portal, pass through the bubble and out of the other portal, at which point the world physics will take over and you will be pulled back into the portal you just exited from. There seems to be no friction in the portal physics bubble, so you could keep bobbing between portals indefinitely until one of them is moved/closed, or you move so that you no longer land back in the portal(s).

Speedy things go in, speedy things come out

This is probably the coolest and most useful feature (beyond the common getting around obstacles). You come out of a portal as fast as you enter it. If you set the portals above each other (one on the floor, one on the ceiling), you will accelerate to terminal velocity. If you place a portal in the floor on the ground, and another in the wall and jump from a height into the floor portal, your vertical velocity will be translated into a horizontal velocity on exit.

There seems to be no distance limit between where you can place the portals (this is particularly important in Portal 2). There also seems to be no distance limit on where you project a portal onto (across the room, down the end of a corridor, or even further). You just need to point at a surface that can accept a portal.

Ultimately, the best way to get your head around the physics is just to play around with them and have fun.