Someone educate me. Isn't this farcical at the core? If we are living in a hologram, then why is our world visible inside of structures, even when devoid of light (eg: buildings, dark tunnels, etc).
They're not saying the universe is a light hologram like the one on your credit card, they're saying it might be holographic in the sense that our 3d space could be a projection of a 2d boundary.
The idea came about as a way to resolve the black hole information paradox in a way compatible with string theory (the idea is that information can never be destroyed, but black holes appear to destroy information). One interesting consequence would be that our universe could be the result of a black hole in some other universe.
Last I read about holographic projection was the idea that our universe is a 3D projection of a 4D star. Is this a completely different theory or maybe just easier to test?
Where does the idea come from that information cannot be destroyed? Is that supported by strong evidence, or is it just an assumption, axiom, or hypothesis?
My intuitive sense is that information can be created and destroyed. For example if I arrange wooden block letters to form a sentence, I have expended energy to encode information. If I scatter the blocks randomly, I have expended more energy to destroy information.
It's supported in both classical mechanics (Liouville's theorem, which is a vital component of the proof of Newton's second law) and in quantum mechanics (quantum unitarity).
The term hologram is more of an analogy than anything else, you shouldn't think of it as a projection produced by light. The idea is that we're living on the edge of a high-dimensional membrane and that our 3 dimensions (+ time) form the surface of that membrane. One of the interesting thing about membranes is that the surface encodes a lot of information about the interior structure, or stated differently, the interior determines the surface. That's what they mean by hologram.
The other replies here reference a 2D encoding of a 3D space. That's a simple example of this kind of holograpy but it's not the one being tested for. Most of hte holographic theories reference a much higher dimensional space on the inside and a 3 dimensional surface.
The 'hologram' in holographic physics doesn't refer to the standard 3d optical illusion things. It's a more general term for 3-dimensional information being encoded on a 2-dimensional surface. Just like the hologram you're thinking of constructs a 3d image out of a bunch of 2d dots, so the entire physics of our 3d universe are constructed out of information on an imaginary 2d surface.
The optical holograms we see often are an example of holograms in general, but they're far from the only ones.
Indeed, it's amazing tech. It's even better than you think: size of the image is dependent on projection, not size of the medium. If you cut it it will show the same size as before, but with lower resolution. That is one of the things that blows my mind every time: the less data points there are, the less precise it is, but it's all still complete.
I don't think they mean literally a hologram. As far as I can tell, they're checking to see if the universe is actually a 2d sheet like an infinitely thin piece of paper. It's like a computer game displayed in 3d, but all the data exists in a 2 dimensional structure (ram).
Or maybe I just don't get it at all. (I know next to nothing about quantum theory)
