String Theory: A Theory of Everything?
Present day physicists are currently dealing with one question: How does gravity fit in with the other three forces? Namely, the electromagnetic, strong and weak forces (which are thought to be mediated by force carrying particles called bosons). As discussed in this post, the question has guided scientists towards the Theory of Everything (TOE).
One proposed TOE is String Theory. It was originally based on the works of Gabriele Veneziano in 1968. Veneziano was dealing with something very strange, things called Tachyons. Tachyons are supposed to move faster than the speed of light! Venziano’s theory is no longer accepted. There have been some step-ups in the theory since then.
String Theory says that every single fundamental particle is actually made of a tiny, one-dimensional, vibrating ‘string’. They exist on extremely small scales, much smaller than atoms (If string theory is a theory of quantum gravity, then strings will be about a millionth of a billionth of a billionth of a billionth of a centimeter)! The different frequencies, or modes of vibration, of these strings gives each string it’s own respective properties.
It gets more diverse in the string theory world. Strings can exist as either open or closed models. Think of open models like pieces of spaghetti:
and closed models like flexible hoops:
Open string models are said to account for matter while closed string models are said to account for hypothetical particles of gravity, gravitons. Strings are thought to bend space and time while they vibrate, creating gravity just like Einstein predicts.
In both of these diagrams, you can see that each string has it’s own frequency. Of course you have to remember that strings are down-right-strange. These are just simply metaphors.
In fact, strings are said to vibrate in more dimensions than the ones we are familiar with. These dimensions are difficult to detect since they are said to be very, very small. Only the strings are said to contain them. A good comparison to explain these hidden dimensions is to think of a rope. Imagine you are standing 20 ft. away from the rope. To you, it seems just like a 2-dimensional rope. It is not until you come very close to it that you realize it exists as a 3-dimensional cylinder.
There have been multiple versions of string theory that include different number of dimensions and types of strings. There is a table of string theories here. Current progress is taking place in unifying all the versions of string theory into one “superstring” theory- M Theory.
String Theory has many profound implications. A single post cannot fully provide all of them. Some scientists think that we are stuck in a 3 space dimensions+1 time dimensional “brane” and that other branes exist, maybe just a fraction of a centimeter away.
Carl Sagan claims that “Remarkable claims require remarkable proof”. To be completely honest, there is no proof of string theory available today, and may not ever be. This article covers a variety of tests being conducted.