The double slit experiment and the limits of intuition
A reminder that pre-existing beliefs and prejudices are often inaccurate and insufficient.
In recent years, populist politicians have been encouraging us to believe in simplistic solutions to complicated problems, to trust in our intuition, to confirm our biases, to scorn expertise and avoid thinking too deeply.
Don’t challenge your prejudices, wallow in them, they say.
The double-slit physics experiment is an extraordinary thing for many scientific reasons - but I like it because it forces me to reconsider my preconceptions, and reminds me not to get too comfortable in my reality.
My (overly) simple description of the experiment:
Place two pellet guns two metres away from a wall, with a one metre gap between the two guns. Then place a board in front of the two guns. The board has 2 vertical slits in it that exactly align with the spacing of nozzles of the guns.
Then, fire pellets from the two guns.
The pellets fly through the air, pass through the two slits and hit the wall behind, forming two vertical lines on the wall, that align with the two slits.
As expected, two lines are created by the pellets on the wall.
Now, repeat the process but use tiny electrons instead of visible pellets.
The electrons fly through the two slits, but more than two vertical lines form on the wall behind the board. Let’s say five lines appear on the wall behind.
Unexpected - multiple vertical lines appear on the wall - even though the electrons only passed through the two slits in the board.
The firing of the electrons produces a counter-intuitive result. It’s quantum physics, apparently. Electrons can be particles and probability waves at the same time. When they are waves, and pass through the two slits, the waves interact and diffract, causing multiple lines to appear on the wall.
The even weirder part of this experiment is: When the waves are observed, their behaviour changes - they go back to acting like visible pellets - and the pattern on the back wall would reduce to two vertical lines.
The implications are pretty huge, and are still being figured out.
The exact reason why observation causes this change is one of the central questions in quantum mechanics.
One explanation, known as the Copenhagen interpretation, suggests that the act of measurement forces the particle to 'choose' a position.
Apparently, the scientific consensus is that this doesn't mean our consciousness creates reality. Instead, they think it's more about how these tiny particles interact with other particles when we measure them.
Anyway… I may never really understand what the double-slit experiment reveals about quantum mechanics. I like how its results are so counter-intuitive (to me), that they expose the limits of the simplistic stories I use to make sense of the world.
This experiment reminds me of the need to challenge my pre-existing beliefs, as they are often inaccurate and insufficient. Life is much weirder than many of us imagine.
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