This is a short collection of questions we’ve been asked many times. If you’ve got a query that isn’t covered on the list, then why not ask a string theorist?
Why Should I Care?
String theory is part of our ongoing mission to understand the universe. We humans are naturally inquisitive about our surroundings. A deeper knowledge of universal laws could lead to better technology. Oh, and now you can impress your friends at dinner parties by talking about the tenth dimension.
Is It Right?
Mathematically, yes. Physically, we don’t know. So far there has been no direct experimental evidence for string theory, and obtaining direct experimental evidence may require technology much beyond that currently existing. Physicists are divided about the chances of proving that strings exist.
How Would You Test It?
With unlimited budget and unlimited engineering capability, build a collider with an energy at the Planck scale (the size of the galaxy). This would produce higher string harmonics of the observed particles, with a characteristic straight line relationship (Regge trajectory) between mass squared and angular momentum.
Who Does It?
String theory is studied in academic physics departments around the world. It is a very broad area of research. Read more about exactly how scientists use strings.
Why Do Particles Have Mass and Charge?
Most physicists think that mass comes from the Higgs field. This permeates all of spacetime, clinging onto certain particles and endowing them with mass. The LHC has provided strong evidence that this interpretation is correct. The origin of charge remains a mystery.
What Forces Enable Me to Push Open a Door?
Fundamentally, the force of electromagnetism. Electrons in your hand repel electrons in the door allowing you to push against it. In fact most everyday forces, besides gravity, are really the result of electromagnetic interactions.
Why Do We Live in Three Dimensions?
Physicists say that we live in three dimensions because we can usually move in three different spatial directions: “forward-backward”, “right-left” and “up-down”. There’s also one dimension of time: “past-future”. String theorists reckon that there are six extra dimensions too small for us to ordinarily observe.
Why Is It Called String Theory?
Because it claims that every particle is actually a tiny vibrating string! These strings are assumed to be the most fundamental building blocks of the universe.
Will It Change the World?
Not in the near future. At present we don’t know enough about strings to assess whether they’ll be useful. Any technological benefits are probably centuries away. But history has shown that abstract physics can have very concrete applications. You wouldn’t have a computer without quantum mechanics or GPS without general relativity!
Who Thought of It?
Very few scientific discoveries are the work of just one person. String theory is a hugely ambitious project involving contributions from thousands of physicists. Read about its history for more information.
How Do I Find Out More?
Why Does It Need Ten Dimensions?
Unfortunately the precise reason for this is technical. String theory comes from making a quantum mechanical string consistent with Einstein’s Special Theory of Relativity. It turns out that this requires ten space-time dimensions.
How Much Does It Cost?
String theory is done in physics or mathematics departments. As a theoretical subject, the principal costs are the salaries of those studying it. Total expenditure in the UK is roughly two million pounds a year.
Will You Check My New Theory of Quantum Gravity?
No, it’s extremely unlikely that you have stumbled across a correct theory. For an humorous evaluation of crackpot contributions, see here.