Jordan14 wrote:Below the level of Plack Time does exists time but not in the sense that we know it because the time below 3.3+10^-42 secs (I think that's the right value) follow Quantum Laws in the sense that time is unpredictable. So when I say discrete I mean discrete in the sense that below the Planck Time boundary time is nonsense, that is why Planck Time is the smallest value of time.
You have to be careful there. As I said in my previous post, QM, as originally formulated by Schrodinger, Bohr, etc. doesn't require space and time to be continuous, just matter and energy. In fact, Schrodinger's Equation requires taking the derivative with respect to time and position, which implicitly assumes that time and space are continuous.
Despite the great success of "conventional" QM at predicting things like atomic spectra and the properties of subatomic particles, it became clear that not everything was well. The way QM looks at the universe is very different from the way General Relativity, the other highly successful theory of the 20th century, looks at the universe. Furthermore, in the second half of the 20th century, the Big Bang theory came to be accepted, and this brought the problem that at the instant of the Big Bang, the Universe was predicted to be infinitely hot and dense, which caused problems. Also, in their never-ending quest for simplicity, some theoretical physicists looked for a way to unify all four known fundamental forces: gravity, electromagnetism, the strong nuclear force and the weak nuclear force. Attempts to unify electromagnetism and the weak force at high energies were ultimately successful; during an experiment in the 1980s, it was shown that unification does indeed occur at sufficiently high energies. But this wasn't enough for physicists; they wanted further unification with the strong force (known as grand unified theories) and, most challenging of all, gravitation (known as theories of quantum gravity, or more the more grandiose term, Theories of Everything).
As a result, theoretical physicists searched for decades for a solution to these solution. Several theoretically plausible theories have emerged such as string theory. In some of theories, thorny issues are resolved by postulating that there is an upper light to energy. Now, Heisenburg's Uncertainty Principle states that:
(delta E) * (delta t) >= h/4pi
where (delta E) is the uncertainty in energy and (delta t) is the uncertainty in time. If there was an upper limit on energy, this would imply an upper limit on the uncertainty in energy. By the Uncertainty Principle, there would then be a lower limit on the uncertainty in time, which would mean that intervals of time shorter than that lower limit (called the Planck time) would be uncertain. The Planck time multiplied by the speed of light would then give the Planck length, below which measurements of length would be unreliable. This solves some theoretical problems; for example, if we assume that this is true, then we remove the singularity at the Big Bang where infinite temperature and pressure occur. But since we've assumed that space and time are discrete, there can't really be a t = 0 moment, the earliest moment possible is just the Planck time.
This is all nice on paper, but is it a correct explanation of the way the Universe works? Theories like this make few predictions that are testable with today's technology, and most of the few predictions that are testable haven't been confirmed experimentally. For example, many grand unified theories predict that protons are not eternal, but have a very long half-life (I don't remember the exact figure, but its over 10^30 years) and eventually decay into other particles. Since then, giant tanks of water have been placed underground for, and the quantity of water has been measured by instruments precise enough to detect the decay of a single proton. So far, no confirmed cases of proton decay have been observed. This doesn't necessarily that all those grand unified theories are wrong, since some of them predict a half-life that is so long that even those experimental results don't rule them out.
As I've already said, another prediction is that there is a smallest unit of time and length, below which time and length as we know it don't exist. But are these claims correct? The Planck Time and Planck Length are far too small for almost all of our experimental techniques to detect. But a few attempts have been made. Here is one from a few years ago:
http://uahnews.uah.edu/read.asp?newsID=99
To sum it up, the researchers made observations that, according to their calculations, should have turned up evidence for the existence of a Planck Length. No such evidence was found, which casts doubt on the existence of the Planck Length. This is not to say that all scientists agree with them. But it does mean that the quantization of space-time shouldn't be considered as certain as, say, the Schrodinger Equation or the constancy of the speed of light.