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Why is there a sweet spot?

Karmeck
Explorer
Why can't all of the lens be a sweet spot? Why not just make the sweet spot bigger and cover up the blurry part?
21 REPLIES 21

FingerMcPokeye
Heroic Explorer
Haha, Dr. Quantum is one of my favorite explanations.

What gets left off:
If you move the observer to *after* the slits, the effect is the same.

Wierder:
Wait until the photon has already passed through the slits and THEN put a mechanism in place to decide whether or not to observe.  The effect is the same.  Why this is head popping:  It implies that the choice to observe or not affected the photon behavior at a time in the past.

How I wrapped my head around the weirdness:  Imagine instead of a lab for your experiment, you use the universe.  Emit some light from a far away star, let it get gravitationally lensed by a nearby galaxy then pass through the slits in your lab on earth.  Now *after* the light has passed through the slits, decide whether to observe it or not.

If you observe you'll get solid lines.  If you do not observe, you'll get an interference pattern.  You have chosen the behavior of the light.... light that got emitted a billion years before your lab on earth ever existed.