WiFi can pass through walls.
This fact is easy to take for granted, yet it’s the reason we can surf the web using a wireless router located in another room.
However, not all of that microwave radiation makes it to or from our phones, tablets, and laptops. Routers scatter and bounce their signal off objects, illuminating our homes and offices like invisible light bulbs.
Now, German scientists have found a way to exploit this property to take holograms, or 3D photographs, of objects inside of a room — from outside of the room.
“It can basically scan a room with someone’s WiFi transmission,” Philipp Holl, a 23-year-old undergraduate physics student at the Technical University of Munich, told Business Insider.
Holl initially built the device as part of his bachelor thesis with the help of his academic supervisor, Friedemann Reinhard. Later on the two submitted a study about their technique to the journal Physical Review Letters, which published their paper in early May.
Holl says the technology is only in prototype stage at this point, and has limited resolution, but is excited about its promise.