# What’s the easiest tool to explain the most complex ideas in physics? Lego

Professor A.W. Peet featured in the National Post on May 6, 2015 in advance of her lecture at the Perimeter Institute.

Imagine if you could use the world’s most plentiful toy to explain its most complex ideas? That’s precisely what A.W. Peet, a theoretical physicist and University of Toronto professor, seeks to do. In a public lecture Wednesday evening at the Perimeter Institute for Theoretical Physics in Waterloo, Ont., Peet will use Lego as an analogy for string theory, a complex idea in quantum physics that could explain everything from the Big Bang to black holes.

The National Post ’s Ashley Csanady spoke with Peet this week about the theory and how plastic bricks can help illuminate it. Here is a condensed, edited version of their conversation.

National Post: How does Lego factor into your explanation of string theory?

Peet: I wanted a metaphor for making string theory more accessible to people who found it scary or too abstract. For example, you might have seen the difference between a Lego fire engine and a real fire engine.… The Lego fire engine has little doors that open and some features of it that make it somewhat realistic for describing a fire engine but it doesn’t have all the features of a true fire engine, it’s just a model fire engine. I’d like you to think of string theory as like my Lego set. I can’t, and nobody in the world can, build you a fully realistic model of all the things that we really want to understand all the details of in physics, but what we’re looking for is the most realistic model that we can build. String theory is a work in progress and that’s why I like to use the Lego analogy, just to give people an idea that it’s still something that we’re working on refining and building better Lego sets as we get more towards realism.

NP: What is string theory?

Peet: When you went to high school you presumably learned that things like apples are built out of particles, which are built out of atoms that have subatomic particles inside them. When we heard about this in school we were always taught that the fundamental constituents of everything, the most basic Lego out of which everything is made, are particles.

Those are objects are point-like (the idea they are so small they are infinitesimally reduced to points and are non-dimensional), they have no structure inside them. Those are supposed to be the most elementary things in the universe. But string theory comes along and says, well, there are a number of puzzles in particle physics that seem to be incredibly difficult to solve, and what if we just ventured a more daring idea, that instead the fundamental Lego of the universe are not zero-dimensional particles but little tiny one-dimensional strands of energy that we call strings.

NP: So string theory is like the fancier pieces of Lego, with different shapes?

Peet: String theory has a few advantages over particles because strings are more versatile pieces of Lego. They can vibrate in different ways, they don’t just have one way of moving through the world; they can wiggle around as well as moving through space and time. That versatility of strings allows strings to do certain things that particles can’t. One of the things that enables is to build better theories than Einstein’s gravity for describing very extreme physics involved in the Big Bang that created the universe in the first place and the other really powerful gravity situations that we have in the universe, which is black holes.

NP: So, everything we were taught in high school is wrong?

Peet: I’d like to give you a better word for it than wrong. I like to talk about string theory as an evolution of theories of gravity. Newton’s theory of gravity, which was invented three-and-a-half centuries ago, you can think of that as like Gravity 1.0. That was the first version of gravity that was put out by physicists. And it was good enough to land men on the moon, in terms of its precision. It describes the physics of baseballs here on Earth and the motion of moons around planets, and planets around suns, and suns around centres of galaxies. Then Einstein came along in 1916, almost a century ago, and he produced what I like to call Gravity 2.0, it has a fancy name called general relativity. In a familiar regime (like Earth) where you could apply Newton’s theories, Einstein’s theories would reduce back to Newton’s. I like to say that Einstein’s theory superseded Newton’s theory but it didn’t blow it out of the water, it stood on the shoulders of it.
And string theory, which is one of the possible theories of quantum gravity, are trying to build Gravity 3.0, so we’re trying to build something that supersedes Einstein’s theory. If all you want to do is land a man on the moon, then Newton’s theory is good enough. If you want to explain the bending of light by the sun…then use Einstein’s theory. But if you want to ask the more sophisticated questions (like how the Big Bang happened), you need the more sophisticated theory and that’s what string theory provides.

NP: Is there an Einstein or Newton of string theory?

Peet: I think time will tell. There were several co-inventors of string theory and there’s been over 40 years of work on it so far, so it would be unfair to nominate a single person to take credit for the whole enterprise.
That’s one of the features of modern science: a lot more of it is teamwork than it used to be back in the epoch of Newton and Einstein, where a single person could make a very great contribution to a large part of physics.

You can watch the lecture here.

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