Mdthbs

Characters with powerful telekinesis are portrayed as being able to exert a superhuman force using only their minds. For example, they can throw a car.

Based on what I remember from high school physics, throwing a 2000 kg vehicle to 10 m/s requires an impulse of 20000 N⋅s. But Newton's 3rd Law states that momentum is always conserved and every action has an equal and opposite reaction. So exerting a 20000 N⋅s impulse—whether by gravitational, magnetic, or other means—would throw an 80 kg superhero backwards at 250 m/s. Even if they could survive that, it would be awfully inconvenient to walk back to the battlefield.

No violation of Newton's 3rd law has ever been observed by experiment, so even saying that our hero can draw on a vast energy source doesn't solve the problem.

So how could our hero throw a car without also throwing himself? Can the momentum be put somewhere else? Or is there a way for our hero to use his powers to protect himself from harm?

_{Note: I'm not looking for a scientific explanation for where the superpower itself comes from, just a little logical consistency. Truth be told, I mostly want a headcanon for when I watch X-Men films.}

Let us consider the humble FET

Here's a rudimentary description of a Field Effect Transistor (FET): Imagine water moving through a pipe. When the gate value is all the way open, water flows through the pipe freely. As you close the gate valve, the water through the pipe is restricted until the valve is finally closed and no water can flow. The magic? It takes a lot less water energy to open and close the valve than is represented by the water flowing through the pipe.

Why is this important? Because that's the basic operation of an amplifier. A little effort is applied to open or close the valve, but it controls a lot of water. And if you track the opening and closing of the valve over time (say it looks like a Sine wave, smoothly opening and closing, back and forth...), and then track the water flow through the pipe — you'll find that it's the very same Sine wave but MUCH BIGGER! Woot!

Now, let's apply this to your telekinesis

What your superhero is actually doing is acting like the base or gate of a transistor. He/she is creating/managing a channel of force between, let's say, the rotational momentum of the Earth and the object (oh, let's say Hoover Dam) to be tossed about. But your superhero isn't channeling that force directly. He/she is simply setting up the channel, and then controlling it as the gating function.

A little effort in, the destruction of Laughlin, Nevada out. Maybe a minor stress headache as a result. You know, the mental equivalent of a tired wrist from turning a screwdriver too many times.

But my superhero can't be godlike!

Absolutely not! But even FETs have limits. They can't channel infinite amounts of electricity. Superheros with this ability come in many sizes! Some can gate/control enough of the Earth's rotational momentum to kick a poodle. Others have no trouble slinging cars around. There was that one dude, Whackismo! back in the 50s... he actually diverted an incoming meteor! Which was COOL! Right up until the governments of the world figured that not only could he easily rip the doors off of Fort Knox, but that his saving of the world actually made days measurably longer.... People figure the last time anybody heard from him was October 3, 1956.

It's probably best that we forget. We'd hate for Majestic 12 to think anybody was remembering him.

Wait... did you say the days got longer?

Oh, yeah. There's a consequence to drawing energy from the Earth's rotational momentum. If you draw enough of it, the rotation slows down and days get longer. You could draw it from Earth's orbital momentum, but then the years would get longer. Technically you could draw it from Earth's solar trajectory momentum, but that would probably cause the Earth to slowly change its orbital elliptic — you know, the angle of the orbit compared to the rest of the planets. That could be fun.

They could brace themselves against the world behind them.

Basically, they would subconsciously learn to simultaneously exert an equal and opposite force spread out over a much larger area behind them or anywhere else that isn't the car they're throwing. A sign of an amateur telekinetic could be being thrown back by their 'throws' because they haven't learnt to do this yet. The area would be so large the force would be spread out such that that anyone in it couldn't tell someone was using telekinesis without precise scientific equipment.

Psionic/Telekinetic stuff is basically magic though, if you need the realism of "the force needs to go somewhere", then the hero could displace, disperse, or redirect it as they see fit.

Oh, or maybe fold it into a pocket dimension if you're talking really potent stuff.