Einstein's Theory Has a Problem -- This Idea Solves It

Added: 2026-05-12

[00:00:00]The biggest open problem in the foundations of physics is how to make Einstein's theories of space and time compatible with quantum theory.

[00:00:10]Physicists have tried to make this work since the 1930s unsuccessfully.

[00:00:16]This week though, we have a serious contender that's based on a remarkably simple idea. Maybe space is not actually threedimensional.

[00:00:26]Maybe deep down it's just onedimensional. It's not as crazy as it sounds. And I find this idea intriguing because it's not the first time this conclusion has popped up. And maybe the maths is trying to tell us something.

[00:00:41]Physicists have been trying to turn gravity into a quantum theory many times, but the standard mathematical techniques don't work on gravity. You just end up with infinities in the calculations.

[00:00:54]This is why they've come up with new mathematical frameworks such as string theory, loop quantum gravity, causal dynamical triangulations, or asmtotically safe gravity. The curious thing is that in most of these approaches, you either use one-dimensional objects like strings or loops directly, or you find that at very short distances, the space effectively behaves as if it was one-dimensional.

[00:01:22]You can find out by looking at how perturbation, think of a sound wave, spreads out. In three dimensions, the waves spread out with the surface of a sphere. In two dimensions with a circumference of a circle and in one dimension, they have nothing to spread out in. If you calculate the number of dimensions in spaceime this way, then the dimensions are not necessarily integers. Spacetime could have a fractal character. There is a real world example of this. If you look at the propagation in porous media such as foam or sponges and grainy materials, these can be described by fractional dimensions and they often also have a fractal-like structure. Okay, but I didn't want to talk about sponges. I meant to talk about quantum gravity. You see, the idea that space becomes one-dimensional at short distances is a big deal because then the problem with the infinities goes away. The idea is not entirely new, but previously it ran into a rather serious problem, which is that if you build a theory of quantum gravity this way, then you get probabilities larger than one. And what's that? Yeah. Yes, exactly. It isn't anything. Doesn't exist. Mathematical nonsense. In the new paper now, the authors claim that they've solved the problem. In technical terms, the property that you need for quantum probabilities to make sense is called unitarity. And that's what they say they can get. Now, okay, this is all very neat, but how would you test it?

[00:02:51]Well, their major prediction is that actually you basically can't test it.

[00:02:56]It's totally out of reach of possible experimental tests. This is why I have to give the paper an 8 out of 10 on the meter. So, why am I telling you about this? Is because this highlights a problem in the foundations of physics and one that I'm personally conflicted about. The issue is it might well be that whatever is the correct theory for quantum gravity will never be testable.

[00:03:20]And if that is so then is it even still science or will we just end up with a set of mathematically possible answers and we'll end up fighting which one is the most appealing on philosophical and aesthetic grounds. Now, let me be clear that I think there are other problems besides quantum gravity in the foundations of physics that we can solve with the existing mathematics and that we can experimentally test. Notably, that's the question of what dark matter is or what else explains the observations and the measurement problem in quantum physics. When it comes to quantum gravity, I'm not so sure. The problem is that whenever you follow the mass, the observable effects are tiny, like 40 orders of magnitude beyond our current technological ability. And maybe that isn't a technological gap that we can ever close. This is also ultimately the reason why string theory doesn't die because it makes sense mathematically but as a theory of quantum gravity it's untestable and will remain untestable for the next thousand years if not forever. So where does this leave us?

[00:04:28]Well, this is the reason why I stopped working on quantum gravity as a UV completion because the only potentially testable predictions that I've seen coming out of it are either in the low energy range where you can't really distinguish different theories or they rest on some bizarre extra assumptions that no one actually believes to be true unless a journalist asks. But to come back to the idea that space might be merely one-dimensional at short distances, that still seems to me like one of the most appealing ideas mathematically as well as aesthetically.

[00:05:02]And since it isn't widely known, I thought you should know about it. In summary, after a century of mathematics, the answer may be spaghetti. I do a lot of online research and I hate the idea that third parties are tracking what I read, what videos I watch, and what I search for. If you care about your privacy, encrypting your internet traffic is non-negotiable. And this is why I use NVPN. NVPN is an app that makes your internet connection ultra secure. You install it on your phone or laptop and use it to create a safe connection. But it's not just that.

[00:05:41]NodeVPN comes with a malware shield that warns you of fake shops, malicious ads, malware, and fishing attempts. For Android users, they now also display a scam detection warning during incoming calls. It doesn't just protect your privacy. It also makes your life easier.

[00:05:58]You see, NodeVPN has thousands of servers all over the world, and you can choose one. This allows you to access websites in other countries by using a server located there. I find this especially convenient to get around all the blockages on US pages for visitors from the European Union. NVPN is a high quality product that I'm happy to recommend. If you want to try it out yourself, use my link nodevpn.com/zabina or the coupon code Zabina for my special offer. Thanks for watching. See you tomorrow.