What is space? That’s one of the biggest questions  not just in the foundations of physics but,  

I think, in all of science. According to a new  paper which just appeared the answer may be:  

a quasicrystal. Yes, space quasicrystal, sounds  like something you’d buy in a wellness shop to  

realign your chakras. But this idea comes  from two researchers at Perimeter Institute  

who have previously worked on quantum  gravity, and it’s not as crazy as it  

might sound. If they are right, this could  not just answer the question what space is,  

it might also hold the clue for why the laws  of nature are as they are. Let’s have a look.

Matter is made of molecules and molecules are  made of atoms and atoms are made of yet again  

smaller particles like quarks and gluons. But  what are space and time made of? We currently  

describe space and time with Einstein’s theory  of general relativity. In Einstein’s theory,  

space and time are not made of anything.  They are a continuum of infinitely many  

points combining to what is formally known  as a differentiable Riemannian manifold,  

a phrase that I tell you works wonders  to get rid of guys in nightclubs.

Einstein’s general relativity does not work  together properly with the quantum theories that  

we use for the particles. And many physicists have  suspected that the reason is that space and time,  

like matter, is made of something else, a sort  of underlying structure, a type of spacetime  

“atom” in some sense. This is the case in  big approaches like string theory, in which  

everything including space, is made of strings,  or in loop quantum gravity, in which space is  

made of a network of loops, and other approaches  such as causal sets or causal fermions and really  

even Eric Weinstein’s geometric unity has it that  space and time are not what we think they are.

The authors of the new paper say that space and  time have the structure of a peculiar sort of  

crystal, called a quasi-crystal. Quasi-crystals  are mathematically closely related to Penrose  

tilings. A normal crystal has a pattern that  repeats. A quasi crystal also has a pattern,  

but one that never exactly repeats.  It repeats in an infinite variety  

of slight variations. Quasi  crystals are not just maths,  

they have been created in the laboratory. The  Nobel Prize for Chemistry in 2011 was awarded  

for their discovery because they have very  unusual electrical and thermal properties.

Ok, you might say, but if space is some sort  of crystal, why would it be such a complicated  

crystal? Well, the big problems with making space  and time up of other things though is that we  

know that Einstein’s theory is correct to very  high precision. And it’s difficult to reproduce  

the correct predictions of Einstein’s theory from  some sort of discrete chunks. The problem becomes  

apparent if you look at the simplest type of  regular arrangements of atoms you can think of,  

a square crystal lattice. *You might say it’s  square. But now imagine that your friend Joe flies  

by in a spaceship. For him the crystal lattice  would be length contracted in one direction. It  

would no longer be square. This means that  you could use such a lattice to figure out  

whether you are moving or not, something that  should be impossible, according to Einstein.

This isn’t just a philosophical problem,  if you write this down mathematically and  

try to build a new theory in it, this turns  into a nightmare quickly. The issue is that  

the motion of quantum particles in this regular  spacetime now depends on whether their paths are  

aligned with the lattice or not. This would have  observable consequences that we don’t observe.  

This is why there are no approaches to quantum  gravity built on this idea, it just doesn’t work.

So if there are any sort of spacetime atoms, then  their configuration must be more complicated than  

a regular crystal. And a quasi-crystal helps. One cannot just use the standard quasicrystals,  

because these are really only a discretization  in space. One must extend the quasicrystals to  

include both space and time. This is what the  authors of the new paper do. This way, one still  

does not recover Einstein’s theory exactly, but  then again, one does not really want that either. 

What one actually wants is a theory that is very  very close to Einstein in the macroscopic range,  

but on short distances it becomes  compatible with quantum physics.

Not only this, they say that the  quasicrystal might actually exist  

in more than three dimensions of space. It could  have a width in several other dimensions of space,  

so to speak. And because quantum particles  experience these extra dimensions, that relates  

the size of the universe with the masses of  the particles and the strength of gravity.

What are we to make of this? I give this  a 3 out of 10 on the bullshit meter.  

The authors took on a tough problem,  and I think this is a genuinely new  

and creative new approach to solve a tough  problem. However, this idea is far away from  

being a useful theory of quantum gravity.  It does not, for example, actually explain  

how quantum particles would be moving in this  quasi crystal. So it’s really just a first step.

I am personally sceptical that this  will pan out in the end but if this  

video didn’t realign your chakras then I don’t  know what will, so don’t forget to subscribe.

Curiosity is a good start to learn more about  science, but it only gets you so far. If you want  

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premium subscription with unlimited access.  Thanks for watching. See you tomorrow.