Physicists frequently observe matter by hitting it with probes and measuring how the probes are deflected. (This is what particle accelerators are used for. Detectors are used to analyze the scatter of debris remaining after the collision.) The smaller the probes, the more accurate a picture can be gained of the object's structure. All objects can be seen within a margin of error equal to that of the probe's wavelength. You can make a string's wavelength ever smaller by increasing its energy and thereby increasing its frequency. But as David Gross and his student Paul Mende showed in 1988, taking quantum mechanics into account, once you are able to make a string small enough to probe objects at the scale of the Planck length, increasing the string's energy further actually increases its size. Since strings are, in theory, the smallest elements in existence, nothing can become smaller than this minimum size of strings. Therefore, distances shorter than the Planck length cannot be seen. This more or less means that quantum undulations - quantum foam - does not affect anything made of strings. This gets rid of the infinities created when you attempt to merge relativity with quantum mechanics. We can even say that quantum foam doesn't exist, and only surfaced in calculations because we were unaware of the limits placed on how deeply you can magnify space.

Another way in which string theory is superior is that it gives finite answers where you would otherwise calculate infinities. The diagram on the right shows an electron-positron pair meeting. They annihilate one another in a burst of pure energy as a photon, which then releases its energy back into another electron-positron pair. If you replace the photon in this situation with a point-particle graviton, the power of its force is in a single point which gives rise to infinite calculations. When the point is replaced with a string (below), the energy is distributed around the string to give finite answers.