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# A Layman’s Guide To String Theory

It’s probable that you have heard the word “string theory” before on science shows, in movies, or even from Sheldon on the US sitcom, Big Bang Theory. There has been no shortage of hype about the topic, especially from those in the field of physics. You may even have looked for more information about string theory yourself, only to find the topic complicated and hard to understand.

Today we’re going to attempt to break it down in layman terms so you don’t have to be a theoretical physicist to understand it. Then you can decide for yourself if it’s deserving of the hype.

## What is string theory?

In short, string theory refers to the mathematical models which seek to find a common explanation for the four main forces seen in nature. These forces are the electromagnetic force, the strong and weak nuclear force and gravity.

### Doesn’t relativity and quantum mechanics already do that?

The Standard Model

General relativity is an amazing scientific theory. It explains how gravity in the world of the large works. It tells how and why planets orbit stars, and how those stars orbit the milky way. Relativity makes predictions which can be seen and verified when you look through a telescope.

Quantum mechanics is equally amazing. It explains the world of the tiny. It gives us a mathematical description of atoms, electrons and quarks and how they interact with each other. Unlike the world of the large, which could be described as serene, smooth and predictable, the quantum world is incredibly strange, weird and chaotic.

### So what’s the problem?

Einstein spent the last years of his life trying to unify those 2 theories because as great as they are, problems and inconsistencies occur in some situations which show that neither theory has all the answers. They’re essentially incomplete.

One such situation is a black hole. Black holes are massive in density. They are so dense and heavy, that not even light can escape its gravitational pull. But they are also incredibly small. Gravity has compressed all that mass into a tiny point called a singularity. Do we use relativity to explain a black hole because it contains so much mass or quantum mechanics because it is so tiny?

And there exists the problem. Because the center of a black hole is both incredibly tiny, yet incredibly massive, you cannot avoid using both general relativity and quantum mechanics at the same time. When you attempt to do just that, 1+1 equals 8. They break down and give nonsensical predictions and answers that don’t make sense. It’s kind of like living in a city with 2 different sets of traffic laws that often conflict with each other. The universe is not nonsensical, 1+1=2 not 8, so something is terribly wrong.

### Enter String Theory – The theory of everything?

String theory attempts to unite quantum mechanics and general relativity so we can make sense of the universe on all scales, at any place or time, large or small without breaking down.

String theory does this by throwing away the idea that subatomic particles are point-like; instead replacing that notion with tiny vibrating bits of energy, called strings. They’re so tiny that if you enlarged a single atom to the size of our solar system, a string would only be the size of a tree on earth.

These strings are said to ‘vibrate’ at different rates. These ‘notes’ or vibrational frequencies are what give rise to the different properties of quarks and atoms. Vibrations which are similar to the notes on a guitar.

One particular type of vibration (note) may give rise to a muon, while another represents an electron. By changing the vibration of the strings, you can create different particles.

By replacing those point-like subatomic particles with little vibrating strings of energy, we open up a window to the universe that relativity and quantum mechanics can not; a window which may offer us insight into gravity at the quantum scale, black holes or even the birth of our universe itself.

### Are there problems or controversies?

For starters, string theory requires our universe to have a minimum of 10 dimensions. These extra dimensions are so small, they cannot be seen. They’re even smaller than quarks. Dimensions which we cannot see or feel doesn’t sit well with many people. It was partially responsible for keeping string theory on the back burner for more than 15 years because many thought the idea was ludicrous and wouldn’t take it seriously.

Another problem is testing string theory. While string theory does in fact make predictions that are testable (an absolute requirement for any serious scientific theory is being able to falsify it), many of the tests require technology that we do not possess yet and may not for hundreds, if not thousands of years from now. There are plenty of things that can be done that will be very suggestive if discovered though, (we may be able to see evidence of extra dimensions at the LHC, or evidence of cosmic strings with NASA’s LISA mission) but they wouldn’t be 100% conclusive.

So now we patiently wait while researchers and theoretical physicists try to discover new ways to test string theory.

### What’s this I keep hearing about multiple universes?

One interpretation of string theory’s mathematics may suggest that we live within a brane (membrane). This brane would contain our entire universe and would exist in a higher dimension or “bulk”. In this higher dimension, other branes may exist which could contain their own universes.

In fact, many theorists propose that our brane (or universe) was completely void of matter and energy, and that it happened to collide with another brane in the bulk. The collision would have been so energetic, that it would look just like a big bang (see picture on the right).

Though, that doesn’t necessarily mean there are alternate Earths with another you in those brane universes. The laws of physics in these other dimensions or branes could be incredibly different. For instance, gravity may not exist, or the electromagnetic force may be weaker than ours which would result in stars being unable to form. That universe would be just a sea of protons and neutrons floating around, forever.

### What is string theories current status in physics?

Unfortunately, directly observing strings is far beyond our current technological means. Additionally, string theory’s rich diversity makes it difficult (though not impossible) to derive unique predictions that are specific to just string theory.

Still, particle physicists at CERN’s LHC particle accelerator could connect string theory to reality. In particular, 2 discoveries, supersymmetry and extra spacial dimensions would suggest that string theory is on the right track. Stay tuned.

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1. MarEugenia Pereira

October 9, 2012 at 9:59 pm

I think string theory is likely the best candidate. It’s fascinating! I do believe in other Universes, it makes a lot of sense. Does our universe get more dimensions as we expand?

• Tina

April 9, 2013 at 3:16 pm

More dimensions? That is possible but not probable; most likely matter will increase in size, not in number. I also believe that String Theory will emerge as the only viable science. However, as this happens more theorists will come forward with questions that will raise even more new theories. I love it!

• Tony

December 6, 2016 at 5:14 am

We already know there are other dimensions from the Bible. Jesus’ transfiguration on the mountain with Elijah and Moses seen talking to him.
God has all the answers you seek.

2. Joe

June 23, 2014 at 12:48 pm

If there are multiple universes, why haven’t I, in a different universe, bridged the gap and given myself money? Or why hasn’t a powerful ruler bridged the gap and taken over the planet? The theory is so vague on how many universes and also what point in time they are in. If there was multiple universes it would be safe to say that an evil ruler more advanced than us could come into our reality and enslave us. There is no science that can refute that.

• Jacques

July 29, 2014 at 6:07 am

Why should you be able to cross between Universes? You would not even exist in another universe, since we are not talking about copies here. We are talking about discrete, separate Universes, each with their own physical laws and constants. Nothing indicates that any being in this universe would be able to even observe another universe, much less beings in another universe. Even assuming that there are other beings in other universes.

• Tom Arrow

July 23, 2016 at 8:23 pm

Why would someone so advanced be even interested in enslaving us? We are hardly that interesting. Or did you ever feel the need to, say, go into the forest and enslave ants?

3. Ruth

April 20, 2015 at 11:10 am

I’ve been reading Brian Greene’s book ‘Our Elegant Universe’ and prior to that Stephen Hawkings “Brief History of time”. Struggling, struggling, but so fascinated.
Thank you for your excellent, user friendly explanation of string theory. And the plot thickens.

June 6, 2015 at 10:51 pm

I know exactly what you mean, Ruth. Both of those and others fleft me feeling like the “savage” out of Brave New World. :o)

4. Derek Edwards

December 22, 2015 at 8:01 pm

My problem with string theory is that I can’t find any explanation of first principles. I don’t know if I should be impressed with all the wonderful things it can/could/might do when I don’t know how to tell one string from another, what properties define a string, what differences to look out for, how to recognize the string that can be part of a particular type of particle, how strings fit together to make things. Or anything useful about them really. The summary above doesn’t help, nor do Brian Greene’s Elegant Universe, television programs or TED talk.

Does anyone know where this sort of basic knowledge can be found, please?

5. Randy Purcell

November 28, 2016 at 1:36 pm

I had a chance to speak with Jim Gates, winner of the National Medal of Science (2013) and now head of string theory research at University of Maryland and was surprised to learn, contrary to this article that not string theories does NOT require additional dimensions. He told a group of us that his work at U of Maryland is focused on string theory that takes place in one dimension. When asked why so many other theorists use the multiple dimension model he laughed and said because its makes the math so much easier. If you’re not familiar with his work, see him on youtube, wiki, etc. Very cool and relatable guy for the the first person ever to author a book on supersymmetry…

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