Laplace's Demon and the Deterministic Nature of the Universe

After Newton's ground-breaking and revolutionary work on classical mechanics in the seventeenth century, nature's secrets were beginning to unravel. And many years later and many scientific breakthroughs and discoveries later, Pierre Laplace, a French scientist put forth his famous quotation known as 'Laplace's Demon'. It was the year 1814 and he envisioned a super intelligent universal mind (the demon) that knew the location and position of every atom in the universe and had complete knowledge of all the forces that act on these atoms. And this all-powerful universal mind could apply the laws of physics to determine the entire course of events from the moment of creation to the end of time. In effect he was saying that the past, the present and the future are ultimately predetermined? The future has already happened. Any cause has an effect that can be predicted and any effect has a cause. In fact a cause is an effect and an effect is a cause. Each cause is it's own timeframe. Each effect is the next timeframe. Time is actually a series of timeframes (Could each timeframe be the 'Plank time', the minimum unit of time, 10^-43sec). Time is a series or a chain of occurences, or causal chains. Laplace's universe is a universe where randomness does not exist and uncertainity does not exist.

Heisenberg Uncertainty Principle

The fundamental building blocks of the universe are elementary particles at the subatomic level. This is the world of quantum mechanics. And the more we investigate this world, the more bizzare it seems! But this is the real world, this is the true nature of reality. Despite the fact that quantum mechanics is counter-intuitive experiments always support its assertions making it a highly successful theory.

The existence of determinism can be ruled out by the Heisenberg Uncertainty Principle, because the demon requires precise knowledge of particles to accurately predict the future events of the universe. And precise information on particles has been ruled out. It is fundamentally impossible to measure the position and momentum of a particle at the same time with complete accuracy, because the very act of measuring one of the characteristics affects the other. So the more you learn about a particles position, the less you learn about it's momentum, and the reverse is also true, the more you learn about momemtum the less you know about it's position. In fact if you halve the uncertainty in position you have to double the uncertainty in momentum. So if we take an electron (or a photon) for instance, which is a so-called 'point' particle, we can never know precisely where it is, all we can estimate is the probability of finding it at any given point.

Simply put, in an experiment to measure the position of any elementary particle, we shine a light on it and the reflected light indicates its position. But the accuracy of its position is determined or limited by the distance from crest to crest (wavelength) of the light we use in the experiment. We also know that the measuring light disturbs the particle's velocity in minute but an unpredictable way (do photons not have always the same velocity in a vacuum?) and the amount of this disturbance is proportional to the energy of the measuring light. So to increase the accuracy of locating its position, we use shorter wavelengths of light, which means increasing the frequency and energy of the light and therefore introducing more unpredictability or uncertainty in the particle's velocity. This is the principle that underpins quantum mechanics. And it's crucial to understand that this uncertainty is not a result of human incompetance in carrying out such measurements. The position and velocity cannot be precisely measured even in theory! This uncertainty is intrinsic to the quantum world. There is an unavoidable element of unpredictability in the universe around us. And this uncertainty also applies to other pairs of observables, such as energy and time. It is a consequence of the wave-particle duality property of elementary particles. So Mr. Einstein, It appears that God does play dice.

So is all information and all knowledge probabilistic? Well yes if all information that we possess or become aware off is dependent on the electromagnetic spectrum. And that's how we see things, measure things, become aware of things. So what we see does not have to be the definitive version of reality. There must be numerous versions of reality. There must be infinite versions of reality. Just like beauty, reality is in the eye of the beholder. Particles exist in a quantum state, which does not have precisely defined positions and velocities. And the same principle must apply to the macro level.

And to make reality even more bizzare, it appears that particles lead a double life, sometimes they behave as particles, other times as waves. Constructive and destructive interference patterns are characteristic phenomena associated with waves, yet experiments (the famous double slit experiment) show that these patterns can be produced by particles such as electrons or photons. And even more bizzarely, when only one particle at a time is used in the experiment the same interference patterns emerge, as if the particle is passing through both slits at the same time producing this interference. So the same particle can be in two places at the one time!

It seems beneath the surface of our common sense world lies another world!