In this video, we delve into the famous double-slit experiment, which not only revolutionized modern physics but also raised profound philosophical and spiritual questions. The discovery that observation alters the behavior of matter challenges us to reflect on the nature of reality and the connection between consciousness and the universe. The experiment bridges science with spiritual traditions that have discussed the nature of perception and reality for millennia.

Double-slit experiment – from Wikipedia:
If light consisted strictly of ordinary or classical particles, and these particles were fired in a straight line through a slit and allowed to strike a screen on the other side, we would expect to see a pattern corresponding to the size and shape of the slit. However, when this “single-slit experiment” is actually performed, the pattern on the screen is a diffraction pattern in which the light is spread out. The smaller the slit, the greater the angle of spread. The top portion of the image shows the central portion of the pattern formed when a red laser illuminates a slit and, if one looks carefully, two faint side bands. More bands can be seen with a more highly refined apparatus. Diffraction explains the pattern as being the result of the interference of light waves from the slit.

If one illuminates two parallel slits, the light from the two slits again interferes. Here the interference is a more pronounced pattern with a series of alternating light and dark bands. The width of the bands is a property of the frequency of the illuminating light.^[20] (See the bottom photograph to the right.)

When Thomas Young (1773–1829) first demonstrated this phenomenon, it indicated that light consists of waves, as the distribution of brightness can be explained by the alternately additive and subtractive interference of wavefronts.^[9] Young’s experiment, performed in the early 1800s, played a crucial role in the understanding of the wave theory of light, vanquishing the corpuscular theory of light proposed by Isaac Newton, which had been the accepted model of light propagation in the 17th and 18th centuries.

However, the later discovery of the photoelectric effect demonstrated that under different circumstances, light can behave as if it is composed of discrete particles. These seemingly contradictory discoveries made it necessary to go beyond classical physics and take into account the quantum nature of light.

Feynman was fond of saying that all of quantum mechanics can be gleaned from carefully thinking through the implications of this single experiment.^[21] He also proposed (as a thought experiment) that if detectors were placed before each slit, the interference pattern would disappear.^[22]

The Englert–Greenberger duality relation provides a detailed treatment of the mathematics of double-slit interference in the context of quantum mechanics.

A low-intensity double-slit experiment was first performed by G. I. Taylor in 1909,^[23] by reducing the level of incident light until photon emission/absorption events were mostly non-overlapping. A slit interference experiment was not performed with anything other than light until 1961, when Claus Jönsson of the University of Tübingen performed it with coherent electron beams and multiple slits.^[24][25] In 1974, the Italian physicists Pier Giorgio Merli, Gian Franco Missiroli, and Giulio Pozzi performed a related experiment using single electrons from a coherent source and a biprism beam splitter, showing the statistical nature of the buildup of the interference pattern, as predicted by quantum theory.^[26][27] In 2002, the single-electron version of the experiment was voted “the most beautiful experiment” by readers of Physics World.^[28] Since that time a number of related experiments have been published, with a little controversy.^[29]

In 2012, Stefano Frabboni and co-workers sent single electrons onto nanofabricated slits (about 100 nm wide) and, by detecting the transmitted electrons with a single-electron detector, they could show the build-up of a double-slit interference pattern.^[30] Many related experiments involving the coherent interference have been performed; they are the basis of modern electron diffraction, microscopy and high resolution imaging.^[31][32] Read the full explanation here!

The double-slit experiment conducted with molecules and atoms demonstrates that even at the level of relatively large particles, matter can exhibit wave-like behavior, displaying interference patterns when passing through two slits, signifying that they can occupy multiple states simultaneously, a key principle of quantum mechanics; essentially, it shows that atoms and molecules can act like both particles and waves depending on the observation conditions. 

Key points about the double-slit experiment with molecules and atoms:

Wave-particle duality:Like photons and electrons, atoms and molecules can exhibit both particle-like and wave-like properties, meaning they can behave as localized particles when measured but can also interfere with themselves like waves when not being directly observed! Read More Here!