When we talk about uncertainty in life we generally imply what is coming in the future. In this sense uncertainty is always related to the unknown. But uncertainty can surround the known as well, which always involves the past. Philosophically this has been known from the beginning of civilization. In modern times it has been brought into prominence by science, especially quantum physics where the uncertainty principle became a fundamental characteristic. It led to two far-reaching conclusions. First, the crucial role of the observer in any act of observation; second, the reconciliation of the wave and particle duality of matter.
In simple words, the first conclusion means that what is observed depends on the observer, which implies that the reality of observation is subjective not objective. Putting it in another way there is no objective reality in what we see in the external world. That has been the view of the philosophers since ages past. Whatever we see is simply an apparent manifestation of the ultimate reality. In scientific language we may say that everything we see is a transformation of the cosmic energy (or the universal consciousness).
This view is diametrically opposite to the materialistic view that reality is directly related to perception. A thing is real only if it can be seen, touched, or perceived in any other way. It exists independent of whether it is being observed or not; the moon is there even if no one is looking at it. So how does one reconcile these two opposite viewpoints?
The yoga philosophy suggests a way out (Patanjali's Yoga Sutra, 4-16). Everything in the universe changes in discrete steps; to use the language of physics everything including space, time, and matter is quantized. But the changes occur so rapidly that the mind perceives things as continuous. This is analogous to cinematographic projection of distinct pictures in rapid succession. So whatever one is observing is changing every moment and strictly speaking, at each moment it is not the same thing that one observed before. A distant star that we see now is only what or how it was perhaps a million yeas ago. The same is true for any other object with different time scales. The moon one was looking at a moment ago, continues to be there but it is not the same but a changed one, even though the change is not perceptible.
The second conclusion about the duality of matter is more difficult to relate to real life situations. In physics it easier to visualize "looking" into the subatomic world. A subatomic particle like electron or photon can behave both like a wave and a particle. This duality is obviously not perceived in day-to-day life. However, if we look within, we can find it in ourselves. The physical body is a conglomeration of particles, but it is not a complete representation of us. There is also the astral body, which in turn splits into different sheaths; mind and consciousness are parts of it. The mind can go anywhere and in all directions just as a wave does. It can also be made to give a pointed attention and move from one object (thought) to another like a point. Mind is an attribute of consciousness that is a field in the same sense as electromagnetic or gravitational field.
There is another aspect of uncertainty in real life. This arises from doubts about past actions or events. In most cases we cannot be certain that what we did was the right thing to do, or what happened could have been averted. The uncertainty regarding the past arises from thinking of what might have been, but it does affect the present. What might have been is as much wrapped up in probabilities as what may be. Dwelling on either one is futile.