Albert Einstein put forward one of the most profound explanations of the universe in his
general theory of relativity. It wasn’t a complete picture of the universe, but NOW
science might be one step closer.
Hey guys Julia here for DNews
There are two theories that govern mostly everything in our universe. Einstein’s theory
of relativity accounts for the big stuff, the way planets move around a sun. His theory
says that spacetime is geometric and that large objects warp spacetime. Think of a bowling
ball on a sheet. As the bowling ball moves around the sheet, it bends the sheet around
it. That’s how large objects warp geometric spacetime.
Quantum theory explains all the weirdness that occurs when things get very very small,
how a photon can be both a particle and wave. One of the strangest things about quantum
theory involves an idea called entanglement. It’s an idea Einstein wasn’t too fond
of, he called it “spooky action at a distance”.
For most of the past century, these two theories seemed at odds with each other. If gravity
governed everything then these small particles shouldn’t behave that way. And the puzzle
of how these two pieces fit together to describe our universe has been one of the biggest frustrations
in physics for the past 100 years or so. Thought it’s not for lack of trying. Dozens of theories
have been put forward, but not satisfactory enough.
Until one. After repeated rejections from journals, Physicist Mark Van Raamsdonk described
his theory in an essay published in the journal General Relativity and Gravitation. So in
one neat theory he ties up most of the loose ends between the two dominating theories in
physics. He explained that entanglement could be the basis for geometric gravity.
His idea considers two model universes, one is called anti-de Sitter space (AdS). AdS,
also called the bulk, is similar to ours in which there’s 3 dimensions, it’s filled
with quantum particles, and it obeys Einstein's laws of physics. But it doesn’t expand or
contract. The other universe, called the boundary is only 2 dimensions, is filled with elementary
particles and doesn’t contain gravity. According to physicist Juan Maldacena, the boundary
and the bulk are equivalent, they follow the same physics. Some compare the two universes
to a balloon. The thin membrane of latex is the 2D boundary and the air inside makes up
the bulk. Or others have compared it to a hologram. Where information is encoded on
a 2D chip and projected onto 3D space.
But by using the boundary to describe what’s going on in the bulk, theoretical physicists
could now create calculations without using pesky gravity. And a whole new field of physics
took off.
But the question remained... how are those two universes connected? Well that’s where
entanglement comes in. Entanglement is a pretty fascinating concept in physics and to be honest,
one I don’t completely understand. Entanglement when two particles are linked through an unseen
pathway, some researchers consider this pathway to be the same thing as a worm hole. When
particles are connected in this way, a particle can affect the way the other particle spins,
even if there is a vastness of space between them. So when when observing one particle
we know the state of another. And while this strange behavior dominates most of the weirdness
we call quantum physics, it could also be responsible for space-time.
According to Raamsdonk “Space-time is just a geometrical picture of how stuff in the
quantum system is entangled.” As particles become entangled with each other they form
a network that looks like a tree branching off into many different directions. This network
is called tensor networks. And according to Raamsdonk, these networks connect the boundary
and the bulk. Think of these connections like scaffolding, holding up the boundary membrane.
If entanglement is reduced to zero, these connections are gone, and the bulk is pulled
apart. So entanglement is responsible for the existence of space-time.
So I must caution that this is theoretical physics and most of these discoveries have
only played out in mathematical equations for model universes, not necessarily our own.
So while some research does support this idea, I’d say more research is needed.
So are you curious for more theoretical physics? I bet you are! What about that whole holographic
universe thing? Well Trace and Ian have the spooky scoop in this episode right here.