# Doesn't quantum uncertainty disprove string theory? [duplicate]

String theory states that the oscillations of little strings are responsible for all the particles in and the evolution of the universe. The specific type of particle created by a string depends on the energy and the shape of its vibrations. However, in order for a particle to have a definite identity, the string would need to have a definite energy and a definite rate of change. Since the Heisenberg uncertainty principle forbids this, strings would constantly be a random, uncertain jumble and particles could never retain their identities.

## marked as duplicate by ACuriousMind♦, Diracology, Cosmas Zachos, Qmechanic♦Jul 23 '16 at 20:52

• String theory does not work as simply as you say it does, and it is not clear what you are talking about with "definite identity", or why the string would need a "definite energy". One quantizes the string and one finds creation/annihilation operators for several particles. The Heisenberg uncertainty has nothing to do with anything. – ACuriousMind Jul 23 '16 at 15:18
• cds.cern.ch/record/434343/files/0004074.pdf – Vishnu JK Jul 23 '16 at 17:34

In a nutshell, no.

Part of the problem seems to be that you misunderstand the fundamentals of string theory. The strings do vibrate. The frequency of these vibrations determines the type of particle and the energy of the string determines the energy of the particle.

Second, your understanding of the uncertainty principle isn't quite right. Yes, we cannot know the energy and position (position, not rate of change) of things exactly, but we can get a fairly general idea. Besides, the uncertainty principle doesn't really apply here because it is the frequency of vibrations that controls what type of particle it is.

To summarize: the uncertainty principle has nothing to do with anything, string theory doesn't work as you describe, and your comments about a string having a "definite energy" doesn't make sense.

• Just to try and clear up the H.U.P. reference . The tension in a string is on the order of the Planck force (10$^{44}$ newtons) and some popular science books say the string is kept in shape by constant quantum fluctuations, hence by a roundadout way the uncertainty principle reference, I think. – user108787 Jul 23 '16 at 16:31