[yamtaddle]

What escapes my understanding with the whole "interaction is observation" thing is that I don't get how anything could ever not be interacting with a whole lot of other stuff. Gravity and EM fields are everywhere. Even if photons are somehow immune to that (which, they're not, because gravity can re-direct photons) it's my understanding that we can see the same interference patterns with particle streams of ordinary matter, and I can't for the life of me figure out how those could ever not be interacting with basically everything remotely nearby, including the entire test apparatus.

[phailhaus]

> Gravity and EM fields are everywhere.

And now you understand why "quantum gravity" is such a big question in physics right now! We don't understand it all. I actually don't know anything about how EM fields affect superposition, perhaps someone else can chime in.

[kulahan]

The feeling of asking a question and realizing you've reached the edge of human understanding is very fun

[abdullahkhalids]

Yup, everything interacts with everything close by all the time.

The important thing is by how much, and what sort of interference patterns can this produce.

As it turns out, interference is quite hard to produce randomly because two fields only produce wavering patterns when their frequency and other parameters are almost equal.

So yes, the ball you just threw to your friend is actually spread out over a whole region, that spread is about 10^-34 m so it impact is not visible at all.

[monktastic1]

The short answer (as I understand it) is that decoherence is not binary. The gravitational field may be able to partially resolve the position, for example, and so you only get slight reduction in interference.

https://physics.stackexchange.com/questions/34993/reversing-...