Let's say that there are two people named S and C. They are not far apart; less than 10 meters. Let's also assume the scenario takes place in late evening or in the night, for simplicity.

Normally when C shoots a gun at S then S will most likely not be able to dodge it. That is he doesn't have enough skills to dodge bullets. And C is highly efficient and accurate at aiming and shooting. So, normally when C shoots at S the bullet will hit him for sure.

But, what if S has some kind of mechanism that, when activated, causes the light emitted or reflected by his body to be slowed down or delayed or refracted and, as a result, his body's current position will not be accurate to C. Something like the twinkling of stars in night. Or like a small lag. Maybe this mechanism is also dynamic in the sense that it will delay the light based on the distance between S and whoever is shooting at him. For example, a longer distance lessens the "delay factor" more than with shorter distances.

My question is if this is possible. How would that mechanism be achieved? More directly, how would it be implemented?

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    $\begingroup$ Why slowing down when you can efficiently use a mirror? :-) $\endgroup$
    – NofP
    Jan 14, 2019 at 23:59
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    $\begingroup$ The speed of light in a medium is an intrinsic property of the medium and cannot be changed without changing the medium of propagation. So, what's between S and C? Can you put something between them? Some mirrors, perhaps? $\endgroup$
    – AlexP
    Jan 15, 2019 at 0:18
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    $\begingroup$ would simply putting a large fire between the people suffice? It changes the density of the air, and thus the refactive index, causing ones position to warble just like the stars (for the same reason as the stars, in fact) $\endgroup$
    – Cort Ammon
    Jan 15, 2019 at 0:35

3 Answers 3


Slow down light at source

University of Glasgow Scientists Slow Down The Speed Of Light Travelling Through Air

Researchers from the University of Glasgow and Heriot-Watt University slowed single photons down by shaping the photons at the source.

So with a little science-fiction hand-waving you could have S wearing whole-body technology suit to do it. Basically the suit emits the image of S with the ability to shape the photons.

Slow down light with intervening materials

If you have force fields in your world you could have intervening materials between S and C. The force field holds an invisibly-clear, ultra-dense material that actually slows light as it passes through it. The material is like water or glass but capable of refracting and slowing light to the extent needed by your story.

The gravity at the centre of the material could be almost black-hole like to distort space-time. You'd need equal and opposite gravitational control to nullify the super-gravity outside the event horizon.

But then the bullet C fires would need to pass through the same material which seems to defeat the purpose you've described.

Alternative Images

More science-y with extensions to current technology: use holograms or Augmented Reality projectors to overlay S with both a background mask (to make him "vanish" and an overlaying S image. S's image stays still 10m from C while S actually steps back and over out of the line-of-fire.

3D images could even be projected into C's eyes to create the AR field.


The speed of light in any medium is fixed. Also, when light moves from a medium to a other medium, the bigger its difference in speed among media, the more it bends. This is called refraction.

So all your buddy really needs is a man-sized lens between him and the shooter. Make it a curved lens and make it so that it is not really aligned among them, but a bit off, and the shooter C will see just a big S, kinda distorted as if seen in a hiuse of mirrors. C will probably get a headache from these giant glasses if he stares too long.

Unfortunately for S he will probably go bankrupt building such a lens, specially when it shatters due to shotgun shells refracting differently than light in it. But hey, while C ponders where S even got a giant lens in the very first place, S can run away and disappear.

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    $\begingroup$ The best example of this answer is a pool of water, perhaps two feet deep. You're looking down at an object on the bottom, but when you reach in your hand to pick it up, it isn't where you see it. (This actually happens!) When the light transitions from the atmospheric medium to the water medium, it's refracted (like a prism, bent at an angle) so the object can't be seen where it actually rests. Now, let's use Hubbard's atmospheric shields as proposed in Battlefield Earth (the book, not the horrible movie) and you have a way to offset yourself, at least a bit! $\endgroup$
    – JBH
    Jan 15, 2019 at 2:57

You can have S having a big screen beside him that mimics the surrounding area and make c think that there is no screen but only normal surrounding and s wearing the same technology on an whole body so he gets invisible and the screen will show his body and s will escape.


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