SGU Episode 308

Introduction

You're listening to the Skeptics' Guide to the Universe, your escape to reality.

S: Hello and welcome to The Skeptics’ Guide to the Universe. Today is Wednesday June 8th, 2011 and this is your host, Steven Novella. Joining me this week are Bob Novella,

B: Hey everybody

S: Rebecca Watson

R: Hello everyone

S: Jay Novella

J: Hey guys

S: And Evan Bernstein

E: Yuan Shang Hao. Good evening to all of our listeners in China of which there are...

J: I like your intonation

S: Inflection

B: I'm not sure if it was accurate though but it sounded good

E: Does anyone listen to us in China?

R: Of course, yeah, we have some Chinese listeners

S: But if it's the wrong inflection you say, 'I wanna massage your grandma' you see, so you've gotta be careful

E: You know the thing about saying 'good evening' in Chinese is that I want to say it again in an hour. I don't know what it is

B: O.M.G.

R: Wow

J: That was so bad

B: He was working on that all night

E: Where's my (room) shot? Oh god. (cymbols)

R: You get a sad trombone (sad trombone)

S: Rebecca you're joining us from London this week

J: I say

R: I am, yes, I'm back in Old Blighty, as no-one calls it

E: Rebecca Poppins

R: Yeah, so once again the listeners are being treated to Rebecca at one thirty in the morning. Awesome.

J: But you're still kind of on US time

R: No, not really

J: But you're not in a bad mood

R: No, not really

J: Well at least you're happy recording the show

R: No

S: Alright. Evan tell us what is absolutely fascinating about this day in skepticism

E: Well on this day that you're listening to the show it was 1854 in which the famous mathematician Bernhard Riemann proposed that space is curved and he announced this in a lecture titled On the Hypothesis on which Geometry is Based, which is apparently a very famous lecture that he gave. And what he did is he described the old-fashioned, Euclidean two-dimensional plane geometry along with some other examples of old geometry and... well let me put it to you this way. There's an example in which on a piece of paper there lived a bookworm, right, and this bookworm was drawn on the piece of paper so it was drawn in two-dimensional. You take the paper and you fold it up and you crumple it up. Now the worm drawn on the paper has no sense of the cumbling and the distortion of space that's going on around him because he also exists in two dimensions. Right, follow me so far?

S: Right

R: Yeah

B: Gotcha

S: Oh yeah

E: Whereas actually that crumpled paper is in three dimensions. So extend that out, we live in a world of three dimensions, but actually everything going around us exists in, what we believe is four dimensions, the fourth dimensions being time. And this was important not only as an important discovery of his time but it also influenced scientists and physicists such as Einstein who used Riemann's work in his theory of general relativity in which he incorporated time as the fourth dimension.

S: Yeah but when Riemann was talking about higher dimension I think he was talking about higher spatial dimensions, not necessarily with time as the fourth dimension. That was something that Einstein inserted. He was saying that space itself is curved into a physical fourth dimension which we can't perceive because we're on the surface of the paper like the...

E: That's right, we're like the worm. The two-dimensional worm on the paper has no idea it's getting all crumpled and crushed up.

S: But it's interesting. Imagine being the first guy to think of space as not linear, that's it's not Euclidean, that it's curved. That's mind blowing, right?

E: Big deal

B: The way he did that was to... I guess he was the first one to actually think of introducing numbers at every point in space and that was how he came upon the idea of using that method to describe how it was bent. I guess a pretty key insight. I wonder how relativity would have been affected if he hadn't come up with that and whether it would have been delayed significantly.

R: I don't know. For some reason this reminds me a lot of, was it Plato? Plato's cave/wall idea of people who are...

E: Shadows?

R: Yeah, I guess seeing shadows on a cave/wall so they assume that that's all that life is are these two-dimensional shadows, so if you were to explain the three-dimensional world to them it would blow their minds. And of course you can't say that Plato was thinking in terms of, well maybe there was a fourth dimension, a fourth spatial dimension as such, but I mean he was thinking in those sorts of terms, don't you think?

S: Yeah well that... our perception of reality is shaped by the physical reality in which we live

J: Right

S: We may be ignorant of reality in the same way that the cave shadow people are ignorant of their ultimate reality

R: Right and that's not to suggest that Plato had any sort of evidence of a fourth spatial dimension. I just want to put that out there. For conspiracy theorists out there...

S: He was talking more in just general philosophical terms, not that specific manifestation

J: Bob, what about this thing where we have these three dimensions that we can easily perceive and understand. But why do the dimensions end there? In other words, why couldn't there have been a fourth, a fifth, a sixth, a seventh, an eighth dimension that are physical dimensions?

B: There actually might be and some theories actually, string theory and things, actually consider that - have that as an integral part of that. But those dimensions are, it's kind of weird, they're actually wrapped up and compacted in such a small space that they're not visible easily, so higher dimensions can exist in our universe but we just can't really detect them yet, it's not obvious beyond the three spatial dimensions we're aware of now.

E: I've heard that membrane theory relies on 11 dimensions - they can calculate 11 dimensions based on those theories.

B: Yeah

J: How about - I've heard of other theories talking about other dimensions of time. Imagine two dimensions of time, say, four or five dimensions of say space and two of time. What would that be like?

R: Crazy. That would be...

B: Crazy. How many... two watches wherever you go

S: This kind of stuff only makes sense in the context of mathematics. We can't, you know, really think about it physically.

J: You know just because