The double slit experiment of Thomas Young
Quantum physics unquestionably connects strongly with the consciousness of the observer. ‘How do you know?‘ you will ask me. I will try to explain that on this website starting with the double-split experiment.
In a double-slit experiment, a bundle of monochrome light is focused on a double slit. A double slit device is in fact just a totally black slide with two thin parallel slits only a few mm apart. On the screen behind the double slit you won’t see the projected image of those two slits , as you might think, but it will show you a pattern of light and dark lines. With this experiment, Thomas Young did demonstrate convincingly that light should be a wave phenomenon.
The light waves rippling through the two slits start to interfere with themselves behind those slits, creating zones of maximum and minimum intensity.
For an exceptionally illuminating demonstration of water wave interference, watch this YouTube video from Veritasium and especially the part from 4:30 to 5:30.
Incidentally, this interference pattern of dark and light bands also arises when you will fire electrons, protons, atoms, and even large molecules through a double slit. And that is purely incomprehensible according to our classical views on how the universe functions. Such behavior – being at two places at once – is simply not possible.
Watching photons passing through the slits
The remarkable thing is that quantum physics tells us that light consists of particles, photons. Particles are discrete objects that do not normally pass through two slits at the same time. If we set this experiment up in such a way that we can determine through which slit those photons are passing, the result is that the interference pattern disappears, even if we look at just only one of the two slits. Apparently it is sufficient to receive information about the slit chosen by the photon, to influence the behavior of the photon. Now I consider seriously the idea that information is something that is being processed by consciousness.
Take a look at this ToutestQuantique animation. Play it several times and watch carefully what happens with the quantum waves. when passing through the slits. The quantum waves that you see going in that animation are not physical according to many prominent physicists such as Bohr and Heisenberg. They are waves of probabilities predicting the chance that if you were to measure at a certain location, the particle would be found having a certain momentum (*). Pay close attention when watching the animation to what happens in the slits if only one of the two is observed, and then pay also attention what happens in the unobserved slit.
(*) Momentum is a dynamics concept. It is the product of mass x speed. A 1000 kg car that drives at a speed of 1 m / s has the same impulse as a 2 kg bullet that passes at 500 m / s.
The photon is an abstract concept, not a little ball
Incidentally, the light quantum – soon called photon – is a concept that Einstein introduced and is now considered by most physicists to be real. But advanced experiments have already shown that the idea that photons are real particles is plain wrong. This figure with photon and electron as a ball is therefore misleading as a picture of reality. The biggest mystery in the quantum world is the measurement problem and that is exactly where the consciousness of the observer comes into play.