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If we assume a method of instantaneous teleportation, where an object such as a human or simply a sphere is instantaneously physically removed from one location and transported to another, what kind of a sound or physical effect (eg. shockwave) might this create on departure and arrival in an atmosphere?

On departure, we can simply assume that the space occupied by the object is now a pocket of perfect vacuum surrounded by regular atmosphere. This seems like it would be relatively possible to solve using real physics.

Arrival is more difficult. The air could either be physically pushed out of the space the object will be occupying, which seems like it could have catastrophic results if the air molecules reach relativistic speeds, or it could be teleported out of the space into eg. the immediately surrounding space. Not expecting hard real-world physics answers for this part.

Bonus questions:

  • Would making the teleportation slightly-less-than-instant by adding a time delta of eg. 10 milliseconds for removing/pushing the air help avoid it being a lethal or cataclysmic event? What would be the smallest reasonable time delta?
  • How would the situation be different if performed in water instead of air?
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    $\begingroup$ You've the basis for at least two fine questions. We can only deal with one per thread, but linked questions in their own threads are encouraged. Welcome to the site burneddi. $\endgroup$ Jul 21, 2021 at 4:34
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    $\begingroup$ What are the two questions here? Splitting it in two questions between arrival and departure seems a bit redundant, and splitting off something like the water part of the question (which is really just an "extra credits" type of question) also seems a bit redundant since both deal with fluid dynamics. $\endgroup$
    – burneddi
    Jul 21, 2021 at 13:56
  • $\begingroup$ Obligatory What If... Short version: I suspect both will be not unlike an explosion. $\endgroup$
    – Matthew
    Jul 21, 2021 at 15:25
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    $\begingroup$ The most physically sane version would be teleportation being swapping one volume of space with another. This avoids a lot of logical problems. $\endgroup$ Jul 21, 2021 at 15:34
  • $\begingroup$ OK, they were the bonus questions, but you might get better answers if you were to focus on one issue at a time, it depends on the level of analysis you need and can deal with. Having said that you've not been specific (in fact, you've offered speculation surrounding the assumptions to be made) - this makes for a problematic question because of lack of specificity. You might have asked about the specifics before the dynamics of teleportation. You might get some fine answers regardless of all that. Just a thought. Voting to leave open. $\endgroup$ Jul 21, 2021 at 16:41

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Teleport how?

There are a couple alternative mechanisms beyond what you suggest. One that I've seen used in fiction is that the teleport swaps whatever is in the target space with whatever was in the originating space. This kind of teleportation should be nearly silent (at both ends!); the only sound would be that generated by breaking molecular bonds in any solids that are divided by the boundary of the teleport volume.

Another is to have whatever is at the destination interpenetrate with the teleported object/body. Strangely, doing this with air at atmospheric pressure might be (I've read) survivable, because of the relatively low density of air at standard conditions (dust particles could be a big issue, however, and stone or wood would be very, very bad). With air, at least, this should again be almost silent.

The mechanism put forth in the novel Jumper (Stephen Gould, 1992 -- ignore the film, it didn't represent this the same way) was that the titular jumper actually opened a portal and simply slipped through; this took long enough that there was no actual sound (it was more like taking a quick step than what we usually think of as a teleport).

Your Way

If we choose only your mechanisms, all it takes is that the teleport not arrive all at once to avoid the relativistic air molecules -- if it takes even a millisecond to go from feet to head, you'll get a bang (essentially a sonic boom) similar to the one at the origin end (in fact, the origin bang will be reduced compared to instantaneous vacuum, because there's a progression instead of a discontinuity), as opposed to nuclear-explosion level disaster.

If the energy to push the air out of the way comes directly from the body being emplaced, it'll be similar to a supersonic aircraft ejection without the protective capsule -- pressure applied over the entire body comparable to that of a concussion grenade, and likely fatal. If, on the other hand, the energy is supplied by the teleportation effect itself, it'll still be felt (the rebound of the pressure wave, at a minimum), but won't be like the explosion of a bomb, anyway.

At the departure end, either way, you'd get a similar level of vacuum to what's created in the collapse of a lightning strike's plasma tube -- and of similar cross section (though vastly smaller length), so the sound would be roughly similar to a very nearby lightning strike (without the drawn-out effect you'd get if it were tens of meters away and you heard sound from the length of the bolt).

Water?

Now, to teleport into or from water complicates things due to the density of water compared to air (though it worked very well in Vernor Vinge's novel The Witling -- his was the source of swapping destination with source -- and was needed there to deal with momentum conservation). If you take even ten milliseconds to push a human-sized volume of water out of the way, the amount of energy required will approximate that of a hand grenade -- and do similar damage, by producing literally explosive levels of pressure.

The inertia of the water would actually reduce the sharpness of the clap at the origin, however, but might also result in effects similar to micro-cavitation (which has been hypothesized to produce nanoscale hydrogen fusion).

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  • $\begingroup$ On the departing side in air, how loud do you reckon the sound would approximately be? I understand that the "loudest sound" (misleading, I know) in a standard atmosphere is 194dB, which is when the sound wave effectively creates a vacuum between the peaks. Air has some inertia too though, so I'm not sure if simply flowing to fill a sudden vacuum would be enough to create a sound that loud. $\endgroup$
    – burneddi
    Jul 21, 2021 at 14:31
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    $\begingroup$ Coincidentally, a human body is close to the size of the vacuum tube formed by a lightning strike (except for length); there's no expansion section of the wave, but I expect the volume of the vacuum clap would be similar to that of lightning striking a nearby object. It's pretty loud, but I doubt it's above 190 dB -- certainly not at any distance more than a couple meters. $\endgroup$
    – Zeiss Ikon
    Jul 21, 2021 at 14:36
  • $\begingroup$ That seems like a good analogy. Another follow-up question: on the arrival side, would the people teleporting experience the negative explosive effects? They would essentially be the point of origin for any pressure wave created, and with the wave traveling outwards I feel like perhaps they wouldn't actually experience the worst of the effect themselves -- depending, of course, on how precisely our mechanism works. But then there is Newton's third... $\endgroup$
    – burneddi
    Jul 21, 2021 at 14:47
  • $\begingroup$ That depends strongly on where the energy comes from to displace matter at the arrival end. If it comes from pushing the traveler's body into the arrival space, it'll be like a concussion grenade -- they're likely to die of it. If the teleport effect pushes the matter out of the way, they'll feel it, but "just" the rebound of the pressure wave. Either, however, would effectively prevent the "teleport into a solid object" death or even teleporting into water, because of the much higher energy requirement. $\endgroup$
    – Zeiss Ikon
    Jul 21, 2021 at 14:54
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It would sound a bit like (not exactly like) thunder.

Lightning causes expansion and compression in air, too.

As lightning connects to the ground from the clouds, a second stroke of lightning will return from the ground to the clouds, following the same channel as the first strike. The heat from the electricity of this return stroke raises the temperature of the surrounding air to around 27,000 C° (48,632 F°). The rapid rise in temperature creates a rapid increase in the air pressure as well, rising to 10 to 100 times the normal atmospheric pressure. Under such pressure, the heated air explodes outward from the channel, compressing the surrounding air. As the heated air expands, the pressure drops, the air cools, and it contracts. The result is a shock wave, with a loud, booming burst of noise sent in every direction.

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How is Important

As others have already stated, how is very important.

Let's imagine the case above, where your 3D "You Are Here" is encapsulated in a 4D bubble and lifted from one part of the 3D world sheet to another part of the same 3D world sheet.

From the point-of-view of an observer outside of where you left, you completely vanish the instant you begin moving.

However, gasses, liquid, energy, and other matter, can probably flow freely in all 4 dimensions. So, hopefully whoever created this bubble packed extra, or you'd lose pressure momentarily. Let's assume that for now.

The region your leaving has no pressure drop. The area of overlap between the 4D hypersphere and 3D space is only $\pi R cos \theta$, which will drop the zero when the hypersphere is no longer touching the departure part of the world sheet. However, at no time will the pressure change. So, at the point of departure, there would be no sound.

At the point of arrival, things are a little different. There are not one, but two atmospheres worth of gasses in the arrival part of the 3D world sheet. This will not really create a sound, just a gentle rushing of the wind, unless the hypersphere slams into the arrival 3D world sheet at a good fraction of the speed of sound.

When "You are here" arrives, it will appear instantaneous. But it was preceded for a short amount of time by the atmospheric gasses that had more degrees of freedom inside the 4D hypersphere.

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  • $\begingroup$ This is a good answer in its own right, but it is less instantaneous transportation and more like wormhole travel, is it not? Nonetheless, I appreciate answers that provide alternate viewpoints and ideas. One question: what do you mean by gases, liquid, energy and other matter being able to flow freely in all 4 dimensions? Would that not rather violate our current understanding of physics (no one ever observed gas seeping out of a sealed container through an unseen 4th dimension)? $\endgroup$
    – burneddi
    Jul 22, 2021 at 16:36
  • $\begingroup$ It’s instantaneous from the point of view of someone watching the departure or arrival (because the travelers are quickly dis/re-appearing), but not instant from the perspective of the travelers. $\endgroup$ Jul 22, 2021 at 16:38
  • $\begingroup$ One current theory is that there are 11 dimensions, and we are moving along all 11 all the time. However, all but the familiar 3 of space and 1 of time are compactified - meaning they loop around from beginning to end to beginning again (like a circle) in an extremely small radius. For what I described above, one of these dimensions becomes larger; large enough to be useful for travel. $\endgroup$ Jul 22, 2021 at 16:44
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Depends on the teleportation mechanism.

departure

if instantaneous, then you'll have a thunderclap. Imagine the sound of a paper bag being exploded, magnified about 50-100 times.

arrival

if instantaneous, then the same, plus the yowl of the poor soul being transported, which will feel a tremendous backlash. Superficial cellular damage a very strong possibility ("transportation sunburn"), hydrostatic damage possible, damage to eyes and especially eardrums almost certain.

To avoid these pitfalls transporters are usually imagined as either exactly swapping the same volume at the two ends (this is how renging works in Vinge's The Witling), thereby eliminating also the departure boom, or "projecting" some kind of displacement field, that creates a vacuum just before the teleportation happens (this limits the ear-busting problem to pressure differential between the two points, which is limited to a maximum of 780 millibars and that if transferring between the Everest mountaintop and sea level (of course, entering a hyperbaric chamber isn't recommended in either case).

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