I am sure that this is a scenario we have all encountered. We have all of the expensive sensors that money can buy to protect our vintage collection of bottle caps and Golden Girls memorabilia from theft, but our circa 1987 Coca-Cola commemorative Bea Arthur cap has gone missing. Le gasp.

However, fortune has smiled upon us by way of questionable leaps in logic scientific deduction and credit stealing good detective work. This guy is not using existential crises incarnate transporters to get in and out of their store/mother's basement. They are simply joining to points in space time and stepping into my . . . I mean their secret bunker.

And here in lies the rub. I don't have a sensor that is specifically calibrated to "guy joining points in spacetime". That would be ridiculous. I do, however, have a sensor that detects regional increases in the force of gravity.

So, since my understanding of gravity is "mass bends space time then magic happens" would my localized gravity-o-meter be able to detect his intrusion into my most holiest of locations? If not, what kind of sensor (based on real physics) would I need?

Note, I am not looking for a pressure sensor or laser alarm type of thing as he can get in and out quite quickly. The attaching of two points in spacetime has a runtime of seconds to a minute depending on distance. But after that it can be held for an extended amount of time and released at will. So we need an ambush. Also it is not something you can "accidentally" walk into as until the two points are joined, you can't "cross over". Plus that would defeat the purpose of an ambush.

  • $\begingroup$ I welcome retagging and reformatting. I want to keep the science based tag though because I would like it to be something that can at least be built in theory. $\endgroup$ – Jake Mar 9 '17 at 6:34
  • $\begingroup$ How exactly jumper jumps? By creating traversable wormhole? Or by magic and the only gravity is his own? $\endgroup$ – Mołot Mar 9 '17 at 6:59
  • $\begingroup$ @Mołot I asked a question about that once and they effectively told me I didn't understand gravity properly so I was trying to switch the question around. $\endgroup$ – Jake Mar 9 '17 at 7:22
  • $\begingroup$ and? This does not provide clarification I asked for. $\endgroup$ – Mołot Mar 9 '17 at 7:34
  • $\begingroup$ Call it what you want. The method is that he bends space-time to attach two points so he can walk across them. It could be magic or machine, but it doesn't change the mechanism or the physics of the method $\endgroup$ – Jake Mar 9 '17 at 7:43

If sensitive enough, it technically could detect him. Could it isolate him from the background noise? Could it distinguish between an intruder at 10 meters and a truck at 40 meters? That's an entirely different problem and much harder to solve.

I would suggest that instead you monitor unexpected changes in air pressure. Keep your rooms small, and airflow restricted when not in use, and the sudden presence of an intruder should give an easily detectable change. If you're opening wormholes rather than just teleporting then there will definitely be a difference in air pressure between the two locations which will flag up.


That will totally work and is completely within the range of the best current gravity sensors. To quote:

The superconducting gravimeter achieves sensitivities of 10−11ms−2 (one nanogal), approximately one trillionth (10−12) of the Earth surface gravity. — (Wikipedia, who in turn cites Virtanen, H. (2006).

Which compares favourably with the acceleration (6.674×10−10ms−2) you get from a light human (50 kg) on the other side of a room (5 m).

There may be cheaper ways — a webcam that just throws an alert your way if and when anything changes would be a first or second year project for a software engineer at university, and will work just fine if your bunker is one of those underground ones with no windows letting in natural light (natural light changes a lot, making it a little harder than first year CompSci, but there's probably an App For That already).

  • $\begingroup$ Please indicate the source of the claimed sensitivity re earth surface gravity. Not doubting you, but would like to see how that sensitivity is achieved -- and what bandwidth it's good to. $\endgroup$ – Catalyst Mar 9 '17 at 11:07
  • $\begingroup$ I thought the Wikipedia link would be enough; I've added a link to the dissertation that Wikipedia itself cites. Good enough? $\endgroup$ – BenRW Mar 9 '17 at 11:26
  • 1
    $\begingroup$ Much appreciated! $\endgroup$ – Catalyst Mar 9 '17 at 11:26

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