The Double-Slit Experiment
The Heisenberg Uncertainty Principle states that it is impossible to know both the position and velocity of a particle, or in other words, its momentum. From what we know about atoms, the uncertainty of an electron’s position is larger than the atom itself. The position of an electron is only a probability.
The double-slit experiment has, in my opinion, one of the strangest results in science. Picture two walls, in line with each other, with a gap in between them, where the closest wall has a vertical slit through the middle. If you were to shoot marbles through the slit where they stick to the back wall, the back wall would have a pattern of marbles that looks identical to the slit on the first wall. When you add a second slit to the side of the first, the marbles create two identical slits side by side.
When the single slit was shot with waves rather than matter, it created a line in the middle of the back wall which gradually decreased in intensity as it got further from the slit. When a second slit was added, both waves interfered with each other, canceling each other out at times. This created an interference pattern on the back wall like the one below.
So far, everything makes sense. However, when repeated with electrons, tiny pieces of matter, the expected result would be similar to the marbles. When they were shot through the single slit, they mimicked the marbles, creating one line behind the slit. The double-slit, on the other hand, made an interference pattern on the back wall, mirroring the waves. Even when the electrons were shot one at a time, with no chance of interference, they created the same pattern.
It was found that the electron exited as a particle, became a wave of potentials to enter both slits at once, and interfered with itself, to finally hit the wall once again as a particle. Mathematically, the electron goes through both, neither, the first, and the second slit all at the same time. All the possibilities are the same.
When the electrons were measured, to test which slit they actually went through, the electrons once again acted like matter, creating a double band pattern rather than the interference pattern found without measuring the electrons. The electron acted differently simply because it was being observed. It shattered our idea of matter and particles, creating the idea of quantum events.