Okay, Quick question for you Physics minded people, inspired by Portal:
If Person A were to put a portal on the ceiling (orange) and one on the floor right below it (Blue) and were to jump in and fall for 20 seconds, How fast would they be going? Also assume that some poor fool decided to try and stop them by diving at them at a full run (running 10 Feet Per Second), how hard would Person A hit the floor outside the portal?
Phrased another way:
If Person A jumped off a 10 story building and right before they hit the ground, Person B dived and hit them from the side at 10 feet per second, how hard would Person A hit the ground.
Would either one of them survive?
I have a bet on the fact that no matter how hard Person B hits Person A it is not going to affect their downward motion by more then a few Feet Per Second at the most.
Really hard. If you hit them totally horizontally, there’d be no change in downward velocity, you’d just change the location of the splat (and probably get somewhat beat up yourself, depending on how they landed on you).
For that matter, even jumping upwards, you’d probably not generate enough force to save them, and the resulting deceleration forces from the two of you hitting would be bone shattering for both of you, and he’d almost certainly still die.
At the simplest, just consider that momentum is conserved. No matter what Person B does to deflect Person A, between the two of them they’ll still have all the momentum of someone falling 10 stories. And that’s probably enough to squish both of them.
Assuming that the faller and the tackler are the same mass, the best the tackle could do is to split the momentum between them. That means that, at best, they are going 100 m/s when they hit the floor, which is 224 mph. The only question left is how many pieces their bodies would be in, not whether they would be alive or not.
This is it. The momentum is not only enough to kill one person but both of them. There is nothing they can do to spread it in a way that saves both of them.
This is true, but a sideways intercept dive may not actually permit the would-be-rescuer to couple with the system completely and be accelerated to deadly velocity.
What’s more likely to happen is something like:
-You dive at the falling person and try to grab them; their downward momentum dislocates your shoulders and tips you forward; they either continue falling through the portal (as also perhaps now do you), or they strike the floor beyond it and die, then you fall on top of them, badly injured.
-You dive slightly under the falling person; similar things happen as above, except they fall on top of you, killing you.
I bet you could find a theoretical way to save them. Sufficiently controlling the deceleration is all you’d need. If the room is small enough, perhaps having some sort of mechanism or movement to make them a BIT slower on each pass. Something like that.
With another set of portals, you could also get into a loop and hit the other faller a little bit each time, deccelerating him without either getting a fatal blow.
Actually, without that, you could just stick your hand out and slap him every time he passes. As long as you hit him hard enough to slow him more than he accelerates on the pass, that should do it. Once you stop him, use a portal to get thell out of there before the angry rescuee comes back to slap you back.
Yes, except that you’re talking about slapping someone with sufficient force to more than cancel their momentum from a fall from ceiling height - or to put it another way, slapping them hard enough to throw a person up to the ceiling from a stationary position; I don’t think that’s going to be very comfortable for either party, if it’s even possible.
If we take air resistance into account, things aren’t quite so bleak; the terminal velocity of a human is usually only about 50-60 m/s. Even if Person A had a death wish and tries to streamline themself, they probably wouldn’t get much above 150 m/s; according to Wikipedia, the current world record for skydiving speed is about 170 m/s.
Which is not to say that Person B could save Person A in this way; it’d just make it a little easier to clean up afterwards.
This is a good point, but it raises another interesting issue…
After the two portals are created, air will begin falling through them. In effect, you now have an infinitely high chimney, though one without walls. This would result (seems to me) in quite a strong downward draft after a while, at least near the center of the column.
The wind won’t reach infinite speed because of friction around the edges between the moving air and the still air. I’m guessing there’ll be a smooth, if steep, gradient of speed ramping up from the edges going to the center.
So, while a human’s terminal velocity might be 60 m/s, that figure applies to a reference frame in which the air is at rest. Inside a column of air moving downward, the victim will reach a greater speed relative to the room.
It’s worse than an infinitely tall chimney - on one of those, you’d only be passing through each section of air once - in the looped version, as you suggest, you get to keep acting on the same bit of air over and over again. There would be considerable edge effects, but I think the column of moving air through the portal loop would have a measurable effect.
Also though, since the victim is in free fall, he should be able to fly to one side by positioning his arns and legs like a skydiver - he’s only come into contact with the edge of the portal quite grazingly though, so it wouldn’t help him stop - in fact it would probably be nasty. In such a situation, it’s actually pretty unlikely that a person would keep on falling straight enough to keep falling through the middle of the bottom portal for long.
You know, Larry Niven addressed a lot of these questions in his essay “The Theory and Practice of Teleportation” (originally a Boskone lecture, later included in All the Myriad Ways).
But I think that anyone trying to stop a rapidly falling person by barrelling sideways into him/her is going to get seriously messed up, and probably killed. That hurtling body would hit you HARD, even ignoring the floor underneath you. i know of a case of Skydivers hitting each other in midair and losing limbs. Plus you’d be tumbled, and pick up some downward velocity.
