I'm looking for a chemical that can be injected into the human body and be tracked by satellite that will also be safe to absorb and have no ill or lasting affects. Can you point me in the right direction?

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    $\begingroup$ I guess water will do. $\endgroup$ – Ivan Neretin Nov 9 '17 at 15:44
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    $\begingroup$ If you think you can inject a small amount of an inert chemical into a specific human and then track them from orbit, you really haven't put any effort into the problem. $\endgroup$ – Jon Custer Nov 9 '17 at 15:53
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    $\begingroup$ Haha, thanks for the laugh man, but tracking anyone from satellite isn't exactly easy and targeting specific chemical, identifying person from such distance is complete nonsense. Human's chemical signature is scent. $\endgroup$ – Mithoron Nov 9 '17 at 15:58
  • $\begingroup$ I am sure OP doesn’t want to use this to any evil plan $\endgroup$ – Greg Nov 11 '17 at 6:47

I think that no such chemical would exist.

Assuming passive detection

The chemical would need to decay and emit electromagnetic radiation. Human tissue would need to be transparent for that radiation. Looking at the electromagnetic spectrum, we are not transparent for large parts of it. One would go to low-frequency/low-energy (radio waves) or high-frequency/high-energy (gamma rays). The latter causes cancer. The former suffers from the fact that chemical/photochemical processes that release energy do so at higher, i.e. too high, energies (we emit infrared partly because that's our temperature, partly because that is what comes off some chemical reactions in our body).

Assuming active detection

So the satellite would emit some form of electromagnetic radiation, which would detect the chemical. The same problems as with passive detection apply. Nuclear magnetic resonance and electron spin resonance are the only spectroscopic techniques that use radiation in that region, and they require strong magnetic fields. In theory, you could use the earth's magnetic field instead (its not constant from place to place) - then you are at tiny energies and you still need to irradiate the whole earth, detect the tiny echo, which would have to be unique and would have awful signal/noise ratio.

So, yeah, I think that no such chemical would exist. You are better off implanting a radio transmitter in the subject's phone or head.

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