This question is the first of a series about specific use of teleportation. It will concern only about momemtum and speed: other subjects will be exposed later.


The story happens in our world and current era. The protagonist possesses the power of teleportation with the following characteristics:

  • When teleporting, a volume including the protagonist is swapped with the same volume of matter in another place. For example, if the destination is in open air, the departure will receive the same volume of air.
  • That result with no problem of collision of matter: if the destination is in a solid rock, the protagonist will arrive in the rock. And at the departure, there will be a volume of rock with the same shape as the protagonist.
  • There are no collision problems, but there are still problems: the destination can override a part of something since what matters is the volume. It’s not a problem when swapping a part of a rock, but it’s one when swapping a part of a person.
  • The volume of exchange has the same shape as the protagonist adding a layer around it. The layer is at minima 5cm, but can expand by willpower.
  • There is no minimum time between two swaps: it can be as short as reflexes permits.
  • The protagonist can teleport as long as it has willpower: think of it as a superhero power.
  • The teleportation happens if the protagonist can picture it. Coordinate won’t work, but a memory, a picture/film will (no matter the distance). The protagonist could also teleport in a hidden part, even if what behind is unknown as long as the protagonist can guess it (for example behind a door or a rock).
  • Both volume exchanged keep their momentum ignoring the difference in velocity of the Earth's rotation. Falling toward Earth on the south pole, and teleporting to the north pole will result in the protagonist still falling. Flying westward and teleporting to facing eastward, will cause the protagonist to shoot forward in the eastward direction at the same speed.
  • If the destination is a moving structure (vehicle...), the protagonist will teleport at the coordinate where the structure was when teleporting. But the protagonist will keep its momentum, resulting in a possible speed difference. Comparison is like trying to jump in a car in your everiday life: there won't be too much problems if the car is slow or stopped, but there will if you are on foot and the car is at 90km/h. -If the destination is a picture or a memory of a moving structure, the destination will be at the coordinate when the picture/memory took place.


As the title said, my question is about that last point: speed.

Are they possible downside with keeping momentum when teleporting?

The two major problems I could find are:

  • Teleporting in a moving object when motionless or vice versa.
  • Teleporting by accident above a pit resulting in a free fall, which another teleport won’t resolve (unless quick thinking).

Please try to not raise problems from other subject since there will be other questions for them.

Edit: see also the answer of Zeiss Ikon, which is a nice one.

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    $\begingroup$ At least two "required reading" novels here: The Witling by Vernor Vinge, and Jumper by Stephen Gould. Might also include The Journeys of McGill Feighan by Kevin O'Donnell Jr. $\endgroup$
    – Zeiss Ikon
    Nov 29, 2018 at 18:55
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    $\begingroup$ @Ted Pwyll - Can I recommend you to change the title to "Teleportation - Relative velocity on arrival". I expected the question to be about how long it took to travel not about colliding with the scenery. $\endgroup$ Nov 29, 2018 at 19:13
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    $\begingroup$ @chasly from UK just teleport back, just a little off, and keep a stone statue of yourself as a bonus :) $\endgroup$
    – Alexander
    Nov 29, 2018 at 19:19
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    $\begingroup$ Imagine trying to teleport into the same space as someone else and a Git window pops up asking you to resolve merge conflicts, choose who gets eliminated, and add a commit message for the sake of posterity. $\endgroup$
    – Dubukay
    Nov 30, 2018 at 2:38
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    $\begingroup$ @Dubukay git rebase --teleport? $\endgroup$
    – Cort Ammon
    Nov 30, 2018 at 4:12

5 Answers 5


From some of the comments, I believe you're wanting to discount / ignore the difference in velocity of the Earth's rotation. Beyond that, yes, you still have much to worry about.

It's not the slide that gets you. It's the sudden stop at the end.

Deceleration for Mr. Teleporter from a jet airplane traveling at about 570 mph (917 kmh) to 0 at home, assuming it takes 3 inches for the body to fully decelerate, would be over 43444 G of force. That's... way beyond merely fatal. Your traveler hits the wall hard enough to go through the wall and possibly the next wall. Though he won't know, since he cannot possibly even begin survive that at all. In fact, he'll be a rather disgusting smear mixed into the debris from the wall(s). I suspect there won't be enough solid mass (bones) left over to recognize he was even human. Picture a water balloon exploding against a brick wall.

Similarly, if he's at home and suddenly wakes up, realizes he missed his flight and somehow can mentally picture the right plane (given they all look alike, that's unlikely in the extreme), he's going to suddenly appear sitting calmly in a seat that's going 570 or so mph, but he's at complete rest. I suspect the forces involved are more than sufficient to rip an entire line of seats out of their moorings to the plane's floor and even rip them out the back of the plane. Either way, your teleporter (and probably many other people) just died horrifically. But, at least its over quickly. Again, his body will be converted into a gooey mess in the initial impact between his back and the chair.

That 570 mph sudden stop translates to about 29 823 142 Newtons or 6 704 511 pounds of force on impact. That's about 7 kg of TNT in equivalent energy you've just introduced into either Mr. Teleporter's home and/or airplane.

Maybe a less extreme example won't be so... messy?

Mr. Teleporter is in his car and realizes he forgot to grab his mug of coffee off the kitchen counter. Oops. Well, no problem. He's a commuter, but this week he's a passenger, not the drive. No one will mind if he pops back to the house, grabs his coffee, and then pops back into the car, right?

If their commute manages to get up to 70 mph on the highway (about 113 kph), he's going to appear in the kitchen going 70 mph and have a sudden and dramatically bad (but short) day. He will slide into the kitchen counter with roughly 655 Gs of force, give or take. If he has a kitchen counter that's well made at waist height, is upper body will be torn from the lower body, to impact somewhere else downrange with much less force. So the body will be recognizable and possibly even identifiable. But the bottom half just destroyed the kitchen counter, converting it all to a messy, gooey, pulp of debris.

He strikes the kitchen with almost 450 000 Newtons of force (101 115 lb. or about 450 kJ... that's about 0.11 kg of TNT). As far as I can find via Google, it takes about 1500 lb of force to break a typical 2x4 wall stud. So at 70 mph, he's going way more than fast enough to go through a wall. But then everything gets way too messy to determine whether he retains sufficient mass or velocity to continue going through wall(s) after that.

We can slow him down further, of course. My morning commute, on interstates, often drags along at about 25 mph (40 kph). That same bounce-to-kitchen event results in about 83.4 G when going from 25 to 0 mph. That's still well into potentially fatal territory, but maybe his now-widowed wife won't have to completely rebuild the kitchen out of his life insurance policy funds. Maybe.

As a point of reference, the highest Gs ever survived, according to Google, is 92 G during an Indy Car crash. This describes how his car hit at 214g, but his ear sensors measured 92g, resulting in multiple broken bones (femur, sternum, vertebra, and ankles). And that's with a great deal of safety equipment specifically designed to protect the driver from just this sort of thing. Your teleporter, wearing their best business-casual work clothing and without any sort of helmet, etc., isn't going to be so lucky (if you could even call an 18-month recovery from so many broken bones "lucky.") Note too that surviving high Gs requires physical training, so your typical office commuter won't make it out alive from that sudden 46 G event.

From this speed, he's going to strike with a force of about 57 370 Newtons (12 897 lb., 57 kJ, or about 14 g of TNT).

At 15 mph (24 kph), the impact Gs from suddenly sliding into a wall or other obstacle drop to a potentially survivable 30 G. But that's going to depend on what they hit (a wall spreads the force out more evenly, while striking a counter is probably completely fatal) and how tough they are. Regardless, they're going to suffer major, life-threatening injuries even at that relatively low speed.

Here, we've brought the impact force down to about a mere 20 653 Newtons (4 643 lb., 21 kJ or about 5 g of TNT).

At 10 mph (16 kph), we're down to about 13 G. That's painful but survivable, with about 9179 Newtons of impact force (2064 lb. or 2.2 g of TNT). But I wouldn't want to be going anywhere above that when I teleported.

Note, too, that if he's dumb enough to jump into the kitchen and misjudges his position, then there's now a mass from the kitchen that's sitting at rest in the car and about to strike the seat back he just left or the windshield with those same Gs, which will be destructive to the car and will likely pose a serious distraction to the driver.

If this power is held by a significant percentage of the population, there would be laws and public service announcements and stuff to prevent idiots from doing this sort of thing...

Teleporting with momentum is a bad idea.

Friends don't let friends teleport from moving vehicles.

A few commenters talk about surviving car crashes at higher speeds than above. I just want to mention that in a modern car, the vehicle is specifically designed with crumple zones, air bags, safety restraints, and numerous other safety features. All of this means that, in the split-second timing of the crash, the driver experiences far fewer Gs of force than the total potential Gs of two vehicles colliding. Unless your teleporter has the forethought to wrap themselves in bubble wrap (do NOT try this at home), they won't get the benefit of deceleration until their front half collides with the wall or counter. They instead get to let their internal organs and skeletal system absorb all of that energy all at once.

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    $\begingroup$ Indeed well you can get a fairly good idea of the sort of damage simply by reversing the situation and imagine standing still and being hit by the vehicle you just teleported from. Granted the different shapes and structural properties involved would change the exact effects but the person remains just as squishy in either scenario and will for the most part be fatally squished with largely similar results either way. Especially since in vehicle collisions the mass of the human is generally the limiting factor in the actual force transfer because it barely slows while getting you up to speed. $\endgroup$
    – MttJocy
    Nov 30, 2018 at 17:08
  • $\begingroup$ Yep. Humans are basically water balloons... Really messy water balloons. $\endgroup$
    – CaM
    Nov 30, 2018 at 17:10
  • $\begingroup$ Indeed or as the crystaline thingie in that one star trek episode aptly described the humanoid crew "Bags of mostly water" $\endgroup$
    – MttJocy
    Nov 30, 2018 at 17:13
  • $\begingroup$ Did not think that it would be that deadly with a low speed . The protagonist should be careful! $\endgroup$
    – Ted Pwyll
    Dec 2, 2018 at 11:20
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    $\begingroup$ I was in a motorcycle vs pickup truck head on crash - I was not in the truck. 40 mph me/ 55 mph pickup truck = 95 mph closing speed. Bike destroyed, pickup damaged but driveable. Not so much me. I survived, however suffered structural failures - significant portions of my skeleton are now held together via metal fasteners and strips. Bike frame & tank collapse dissipated much of the energy; serious track-quality riding armour helped protect my internal organs against fatal crush damage; still suffered much crush damage - but lived. Your protagonist needs serious gear. $\endgroup$ Mar 26, 2019 at 15:39

Both volume exchanged keep their respective velocity relative to Earth.

Oh boy this is gonna be fun. Not to the teleporter though.

Which imply there won’t be any problem if the protagonist exchanges place between North Pole and equator

Nope :)

You see, there is a reason why the best places to launch a rocket into space are close to the equator. You get a boost to your orbital velocity by starting from a point on Earth that is moving faster linearly, relative to the rotation axis.

Such a rotation is on the order of 460 m/s over the equator. This is proportional to the cosine of the latitude; at the very poles, this speed is zero.

What this means is that should the teleporter do their thing departing from, say, Colombia, and arriving in Nunavut... They will be causing a sonic boom, for they will be flying eastwards faster than sound. They will be undergoing aerobraking - and since the human body was not built for naked supersonic flight, they will come to rest (in peace and in pieces) a few seconds and probably a few kilometers later.

Likewise, people in Colombia will see a burning mass of melting snow moving westwards. The snow will burn for the same reason meteorites do upon atmospheric entry - it is compressing the air in front of it to absurd pressures, there is no actual combustion involved. Bystanders may also become deaf.

Due to directions and geometry, the same effect may happen if the teleporter 'ports from northern Brazil to Indonesia.

If they move along the same latitude, but say 90 degrees East (Pickle Crow, Ontario to London) they will reappear moving straight upwards at $460 \times cos(latitude) m/s$. Going 90 degrees west will cause them to splat against the ground at that speed.

Teleporting inside something means an impact against the inner wall of the cavity you create, at a potentially very high speed. Great fun indeed!

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    $\begingroup$ OK perhaps wrong wording. Relative to the surface of Earth. I exactly wanted to avoid that situation $\endgroup$
    – Ted Pwyll
    Nov 29, 2018 at 21:35
  • $\begingroup$ @tedpwyll that doesn't change anything. $\endgroup$ Nov 29, 2018 at 21:58
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    $\begingroup$ Hm, I don't get it or my wording is not correct. If I'm standing on the ground, my relative speed to the surface of Earth is 0 km/h. It shouldn't change if I'm on the equator or on the North Pole, thus switching place won't produce a difference of speed. Or you mean that's is not the relative speed to the surface, and I should change that ? $\endgroup$
    – Ted Pwyll
    Nov 29, 2018 at 22:10
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    $\begingroup$ @BKlassen I feel like he's being pretty clear about that. The frame of reference he's conveying is small enough that the Earth is effectively flat. Falling toward Earth on the south pole, and teleporting to the north pole will result in him still falling. Flying westward and teleporting such that he arrives facing eastward, will cause him to shoot forward in the eastward direction, $\endgroup$
    – Wazoople
    Nov 30, 2018 at 1:15
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    $\begingroup$ @MtJocy I read it as the momentum would NOT be traded. If you're driving a car and hit 200kmph, then teleport out, wherever you end up you're in a seated position moving forward at 200kmph, which would be unfortunate for you. If you swap places with something heavy, your car suffers internal damage (before inevitably crashing because there's no driver...). As for the air swap bit, I don't think the pressure difference between London and equatorial regions would be that noticeable. You don't level your house when you open the freezer. $\endgroup$
    – Wazoople
    Nov 30, 2018 at 17:01

I see potential issues with teleporting into a location that the protagonist doesn't know is moving. For instance, he remembers the interior of a travel trailer -- but doesn't know it's currently being towed at highway speed. Alternatively, he might teleport out of a vehicle without realizing it's moving (for instance, a very steady airliner flight, on straight and level course, might easily be mistaken for standing still, if you can't see outside).

Starting at 1000 km/hr is a bad thing, if you don't know it's the case. If you do, you could (assuming you have enough "remembered" destinations) teleport somewhere outdoors that puts that velocity straight up from ground, wait for the "wind" to die to as near zero as it gets, then 'port back to ground. The same method could be used (likely with prior planning as an emergency procedure) to deal with "Oh, I'm above a pit or just outside a tall building" situations.

  • $\begingroup$ Great answer - I think you've covered the whole thing really well. Swapping places with someone on the other side of a door would be unpleasant. Any bits of them that didn't coincide with you would be chopped off and deposited back behind the door. I foresee this as the most unpleasant aspect of the super-power. As requested, I won't put this in an answer. $\endgroup$ Nov 29, 2018 at 19:09
  • $\begingroup$ An excellent method of airplane destruction : book your flight, board the airplane & then during the flight port to a location you know is stationary & occupied by a big chunk of rock, quickly port from there to a safe location (not the plane, the front lawn of your home perhaps) : leaving a large stone statue of self in your seat that's stationary in relation to the plane, it'll rip through the back of your seat & all those behind you & tear a hole in the back of the plane, explosive decompression ensues (assuming you waited for adequate altitude) & you've a plane down. $\endgroup$
    – Pelinore
    Nov 29, 2018 at 19:40
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    $\begingroup$ ^ no, nasty, you don't get to port out of the rock because you just got squished to mush against the side of your man shaped hole by the planes velocity the instant you arrived, didn't think that one through :) $\endgroup$
    – Pelinore
    Nov 29, 2018 at 19:44
  • $\begingroup$ @Pelinore You could pick a rock you know that's 90 degrees around the world (so your velocity vector points up), and expand your field by "willpower" so it's bigger than the rock. Rock lands in the plane at ~1000 km/h relative to the plane, you (and your seat, and some bits of the fuselage and other passengers) get a free skydive upward (you did remember to squeeze your eyes shut, and/or turn backward to the plane, before popping, right?) -- see my answer for dealing with that. $\endgroup$
    – Zeiss Ikon
    Nov 29, 2018 at 20:01
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    $\begingroup$ @Ted Pwyll Honestly I say I don't know how to answer this since the tag Physics is there, but you dont want a scientific answer. I'll just sit, eat popcorn and learn. $\endgroup$ Nov 29, 2018 at 20:42

Unless the source of his powers are somehow intrinsically linked to the Earth itself, I would suggest a simple alternative to Geostationary relativity is to make it relative to the "thing" he pictured teleporting to. Since you've already established that what he pictures is where he goes, then it also stands to reason that that would be the thing he aligns to.

This would eliminate problems like getting splattered inside of a moving vehicle or what would happen if he goes to outer space. This opens up a lot of plot points you can create with his power instead of limiting him by making him helpless to deal with simple issues like a runaway car.

I think the matter displacement element of his power like the risk of accidentally cutting a person in half adds enough risk and intrigue without needing to further complicate it.

  • $\begingroup$ I thought of that. The volumes get the speed of the other. But that would be a problem if teleporting in a full wind zone. $\endgroup$
    – Ted Pwyll
    Nov 29, 2018 at 21:41
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    $\begingroup$ Think of his destination not as the place he is going, but as the photo taken from the camera of his mind's eye. If he pictures a still spot on mount Everest, then he comes in still, even in the midst of a blizzard. This also gives room for character development so that, perhaps in book 2, he may learn that he can throw himself if he pictures a still destination as moving one. Sort of how the Flash learns to use his speed to phase through matter or travel through time as his character developed, it becomes a hook for growth instead of an impetus. $\endgroup$
    – Nosajimiki
    Nov 29, 2018 at 22:06
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    $\begingroup$ I would also pair this with: the matter he displaces will continue it's relative trajectory. So, if he jumps into the blizzard relative to the ground, then where he was would get a nice cold puff of wind and snow. $\endgroup$
    – Nosajimiki
    Nov 29, 2018 at 22:09
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    $\begingroup$ Also, minor problems could arise early on if he does not focus his mind right, like maybe he did focus too hard on the memory of the wind and not the place, and OPPS! he hits a wall. So, he has to learn to not do that. Seeing superheroes make mistakes with their powers early in their character development humanizes them. $\endgroup$
    – Nosajimiki
    Nov 29, 2018 at 22:13
  • $\begingroup$ Might also think about cooperative use of superpowers, structuring in such a way that long distance teleportation is dangerous without assistance, or using an apparatus that they can use to place the body in a state conducive to not being detonated on arrival. $\endgroup$
    – Giu Piete
    Nov 30, 2018 at 9:34

Teleportation cannot pass momentum

If momentum was passed, teleportation couldn't work. A person is never actually at rest. The world is spinning and the world is also orbiting the sun in a spinning galaxy in an expanding universe. Your momentum is constantly changing even is you are standing perfectly still.


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