Hey there PF, as you can see I am newly registered here, but I have been floating around for a little while now reading the forums. That being said, I come to you today in hopes that I can get some answers and resolve these problems I have regarding String Theory. I just recently finished reading "The Elegant Universe" by Brian Greene. It was my first true exposure to the particulars of String Theory. I had heard about it, but did not know what it consisted of. While reading, there were 3 points that did not seem reasonable, so without further ado, here they are. 1. Strings are said to be Planck's Length. Planck's Length has importance because at distances smaller than it General Relativity and QFT are not compatible. Unless I am mistaken, this is due to the Uncertainty Principle causing fluctuations, even in "empty" sections of space-time. However, Greene states that because you cannot accurately observe phenomena smaller than your measuring device. In this case, a string is the device and the phenomena would be fluctuations. Since you cannot observe the fluctuations, Greene states you can say they do not exist. This seems wrong to me, not only because it seems mistaken to disregard an occurrence because you cannot directly observe it, but also because it seems to be disregarding the Uncertainty Principle itself, which is at odds with my second issue. 2.It is found that strings must be under incredible tension. Therefore, it requires enormous energy to cause a string to vibrate. As Einstein said, energy is mass, so therefore vibrating strings should create huge masses. However, this is not the case, Greene states, because quantum fluctuations cause the strings to lose energy, just enough to create small mass particles. First he states that the fluctuations do not exist because they can not be directly observed, but now they are used to cause strings to lose energy? You can not simply disregard one section of the Uncertainty Principle and then use another part, it just is not consistent. 3. The third issue is one about string theory in general. From Greene's book, it seems that String Theory gained a lot of popularity because it stated that a particular string vibration explains the graviton, but I do not see why the graviton needs to exist. General Relativity states that gravity is caused by space-time curvature. Why must the gravitational field be quantized by the graviton? As far as I know, the infinity problems caused by the combination of General Relativity and QFT is when one attempts to apply GR to the graviton. Both energy and mass cause space-time curvature, so why can the same concept not be applied to particles? It seems that QED, QCD, and General Relativity should be combined to be able to explain the forces (assuming the weak force can be connected to QED). This issue may only be born out of my ignorance on the particulars of the GR and QFT incompatibility, but it seems just plain silly to have two different theories on the same force, and then expect them to work together. Thank you for your assistance and time.