How can a phone screen create a hologram?
It isn’t a true hologram, it’s a reflection trick. A video plays four copies of the same image, one on each side of the screen. A clear plastic pyramid placed upside down reflects each copy from its angled sides, and together they appear as one object floating in the middle.
The video shows four copies
Special hologram videos show the same object four times, pointing out in four directions on a black background. Black is important: it stays invisible, so only the bright object shows up.
Share this stepAngled plastic works as a mirror
Each side of the pyramid leans at about 45 degrees. Clear plastic reflects a little of the light hitting it, so each side bounces one copy of the image toward the viewer, while you can still see through it.
Share this stepThe image seems to float inside
Your brain places the reflected object where the light seems to come from, which is inside the pyramid. Walk around it and each side shows its own view, so the object seems to hang in the air.
Share this stepA 160-year-old stage trick in your pocket.
Four imagesangled plasticfloating fish
The idea is called Pepper’s ghost, after a London theater show in the 1860s that made ghosts appear on stage with a large tilted sheet of glass. The same trick is used for concerts with ‘holograms’ of artists.
Common follow-up questions
Is it a real hologram?
No. A real hologram records how light waves interfere, so it shows true depth from every angle. The phone pyramid is a reflection that looks 3D because it floats in the air.
How do I make one myself?
Cut four identical trapezoids from clear, stiff plastic, such as an old CD case, roughly 1 cm wide at the top, 6 cm at the bottom and 3.5 cm tall. Tape them into an upside-down pyramid and search for ‘hologram pyramid video’.
Why does it work best in a dark room?
The reflection is faint. In a dark room there’s less light coming through the plastic to compete with it, so the floating image stands out.
Why does the video have a black background?
A black screen gives off no light, so nothing is reflected there. Only the bright object appears, which makes it look like it’s floating in empty space.
