In our last story under the Cosmology category, we talked about how the frontiers of cosmology exist in the realms of the very large and the very small. We’ll see another example of this in today’s story.
I still remember the first time I saw a hologram. I believe it came with the National Geographic. It was a flat sheet like a sticker, and it had an odd, shiny, prism-like surface. You felt like you were looking “into” something. If you turned it slightly from side to side, it seemed like looking through a window at the model in 3 dimensions. This went beyond the clever ways that painters evoke the illusion of 3 dimensions on a 2-dimensional canvas. You felt as if you could reach in and touch her.
Other ways existed to make three dimensional images before holograms. I remember playing with my ViewMaster as a child. It was a simple kind of stereoscopic display. You inserted paper disks carrying pairs of photographic slides into a binocular style viewer. You could see things like the pyramids, or Niagara Falls, or your favourite cartoons in 3 dimensions. Readers may have seen an antique stereoscope in a museum, where you look down through a pair of granny glasses at two matched photographic prints side by side.
Holograms take the process further. Unlike photographs, holograms do not involve optical lenses. Instead, they preserve the patterns of light diffracted from an object. Holographers capture the light that fell on the object on photographic media. They also capture a reference beam that didn’t fall on the object. When only the reference beam falls on the resulting image, the light is bent. That gives us a reproduction with depth. Dr. Denis Gabor invented holography, for which he won the Nobel Prize in Physics in 1971.
We’ve talked about black holes in earlier stories. Readers know about them from science fiction. They’ve also made a big splash in the news lately. Scientists released the first ever image of a black hole back in April using the Event Horizon Telescope. A black hole is a region in space that’s so dense, not even light can escape from its gravity. Most often, they form from the collapse of a massive star.
This returns us to the frontiers of the very large and the very small. Scientists use the theory of general relativity to study astronomically huge objects like galaxy clusters. Quantum mechanics explains infinitesimally small objects like photons. The trouble is, the two theories don’t explain each other. Black holes have a level of mass that would normally be studied using relativity, but that mass is condensed into a region so tiny that scientists would normally deal with it using quantum mechanics.
As a guitar player, string theory has always appealed to me. It holds that matter consists of tiny vibrating strings. There’s a view in string theory that we live in the 4 dimensions of height, width, depth and time while the strings exist in a world of 5 dimensions. To avoid getting bogged down in string theory, we can just say that this extra dimension is called “holographic duality”.
The researchers think they can create a model of a black hole by using a sphere (which is 2 dimensional) and represent a black hole in 3 dimensions. They would make the sphere out of a material that allows holography. If you can shine a light at one point on the proposed sphere and measure it at another point on the sphere, the resulting holography should show a black hole.
The whole experiment can be done on a tabletop, which is more convenient than trying to observe deep space. Who knows? Having a model black hole on your coffee table may become the next fad in home décor.
The leader of the study, Professor Koji Hashimito says, “the holographic image of a simulated black hole, if observed by this tabletop experiment, may serve as an entrance to the world of quantum gravity.” A theory of quantum gravity is just what scientists need to reconcile the conflict between general relativity and quantum mechanics “Our hope is that this project shows the way forward towards a better understanding of how our Universe truly operates on a fundamental level,” says co-author, Keiju Murata.
In Monty Python’s Penguin Sketch, one of the characters hears that someone “knows everything”. She replies, “I wouldn’t like that! It would take all the mystery out of life.” This experiment may take some of the mystery out of black holes, but we are in no danger of losing all of the mystery in our lives.
We always have more to learn if we dare to know.
Learn more:
Denis Gabor
Osaka University
Einstein Rings in Holography
