The Smallest Thing There Is

The science of quantum physics, or the world of the very small.
By Douglas Duncan

Did you ever ask as a child, “What is the very smallest thing that there is?”, or “How small can something be before it becomes nothing?” Asking those two questions usually give rise to the grander third one, “What is the opposite of the universe?” Well, it is just a theory at this point, as there is currently no technological way of observing; but quantum physicists now theorize that the at the very bottom of the ladder, is nothing more than vibrating bits of oscillating waves, that for now, can only be described as ‘strings’. They conjecture two types… ‘open’ and ‘closed’ strings.

Traveling down through the world of the very small… smaller than the atom, smaller than protons or neutrons, smaller than electrons, still smaller than neutrinos and quarks, continuing downward beyond photons and gluons, we finally arrive at the point where ‘No man has gone before’.

There really is no way to explain String Theory, to most of us, but I researched and sought for the least technical article on the subject, and have included it below.

Just make an attempt to read through it, maybe twice, and you may (or may not) begin to see what the physicists are discussing.

I like the guitar string analogy best, as I would say that most people have observed how a plucked guitar string appears to look like a bunch of strings as it’s vibrating. By the way, cats go crazy when you pluck a string in front of them because they see every one of those vibrations as a single string.

I found the following article on string theory to be extremely enlightening and it is written with a more fundamental and easier to understand explanation. Even so, you still have to concentrate some (or at least browse what makes sense), but it will serve as an excellent beginners guide, and you will be able to discuss and learn further about our quantum universe from gaining a handle on it here.

Think of a guitar string that has been tuned by stretching the string under tension across the guitar. Depending on how the string is plucked and how much tension is in the string, different musical notes will be created by the string. These musical notes could be said to be excitation modes of that guitar string under tension.

In a similar manner, in string theory, the elementary particles we observe in particle accelerators could be thought of as the “musical notes” or excitation modes of elementary strings.

In string theory, as in guitar playing, the string must be stretched under tension in order to become excited. However, the strings in string theory are floating in space-time; they aren’t tied down to a guitar. Nonetheless, they have tension. The string tension in string theory is denoted by the quantity 1/(2 p a’), where a’ is pronounced “alpha prime” and is equal to the square of the string length scale.

If string theory is to be a theory of quantum gravity, then the average size of a string should be somewhere near the length scale of quantum gravity, called the Planck length, which is about 10-33 centimeters, or about a millionth of a billionth of a billionth of a billionth of a centimeter. Unfortunately, this means that strings are way too small to see by current or expected particle physics technology (or financing!!) and so string theorists must devise more clever methods to test the theory than just looking for little strings in particle experiments.

String theories are classified according to whether or not the strings are required to be closed loops, and whether or not the particle spectrum includes fermions. In order to include fermions in string theory, there must be a special kind of symmetry called supersymmetry, which means for every boson (particle that transmits a force) there is a corresponding fermion (particle that makes up matter). So supersymmetry relates the particles that transmit forces to the particles that make up matter.

Supersymmetric partners to currently known particles have not been observed in particle experiments, but theorists believe this is because supersymmetric particles are too massive to be detected at current accelerators. Particle accelerators could be on the verge of finding evidence for high energy supersymmetry in the next decade.

Evidence for supersymmetry at high energy would be compelling evidence that string theory was a good mathematical model for Nature at the smallest distance scales.


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