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S, S, Pokhara
Thus to study a particular phenomenon one performs an experiment or a set of experiments on the given system. These experiments provide some information about the phenomenon occuring in the given system in terms of so me well defined physical variables. Thus in all scientific methods there takes place some interaction between an observer and an object. In many cases, the interaction first occurs between an apparatus and the given object then the chages taking place in the apparatus after the interacton with the object give some information about a given plenoinenon oecuring in that object. Thus in this case interaction also occurs between the apparatus and the observer. Then our main argument is this that the simple interaction which takes place between the apparatus and the object or between the observer and the object causes change in the properties of the object. To understand this idea more clearly let us consider a very simple and small object (say an electron) whiclı we just want to sce. For this we just allow sonje light to fall on the object i.e, on the electron. After striking with the electron the light is reflected in to our cyes and we say that “well, we see the electron", (in reality we cannot see an electron but this is simply a thought experiment.) Now the light exerts pressure on a body on which it falls. Therefore the elactron will be subjected to this light pressure. This light pressure may change the position of the electron from its earlier position. Thus the light scattered from the electron which will give information about the position of the electron does not give the earlier position of the electron which we had desired. Thus when we just want to see an electron's position its position becomes uncertain the light intensity cannot be reduced to zero, othewise we will not be able to see the electron.
If the electron were moving with some vclocity and we had thought of measuring its specd then also we can similarly conceive that the process of measurement of its velocity may change its velocity in a significant way and thus making the velocity measurennent uncertain.
We can extend the whole argument to any system and make the following general statement. The scientific processes of nieasuring any property of any system may change the property to be measured in a significant way which make our knowledge about that property of the system uncertain. This is Heisenberg's uncerta inity principle. It is just one defect of all scientific methods. We can overcome this only by a process in which interaction between the knower and the object does not change any property of the object or there is no physical interaction at all,
(b) Limitations caused by space time and finite speed of interaction :
Let us discuss how space and time limits our knowledge of this world. When we just look at a distant star ( say 500 light years away from the
