If a tree falls in the forest...

[unixronin]

Thought for the day:

Neils Bohr once challenged Albert Einstein to prove that the moon exists when no-one is observing it, after Einstein asked him whether he could really believe that it doesn't.

I don't have the math chops to do it.  But, I believe it can be shown that for the Moon to not exist except when being observed would violate local causality.  This is because the Moon is approximately 1.25 light-seconds away, and thus in order to be observable, the Moon would have to consistently begin existing at least 1.25 seconds before being observed.

(There is also a problem with the fact that the Moon exists in a specific, definable location, implying that it has independent existence even when not being observed.  If we could call the moon into being simply by observing it, why can't we just observe it anywhere we choose, at any moment that the whim takes us?  The simple fact that we can only observe the Moon "where it is" argues rather strongly that it, in fact, is.)

Comments

[vatine]

Does observing tides equal observing the Moon? Does observing the after-effects of many years of tidal wear equal observing that the Moon must have existed in the past?

[unixronin]

Personally, I would agree that observing the tides constitutes indirect observation of the moon, and that likewise observing fossil evidence of past tidal effects constitutes evidence of past existence of Luna. In fact, we can use the effects of tidal drag on the Earth's rotation to calculate a minimum limit into the past for when Luna had to have existed. This very likely predates the existence of, at the very least, any life on Earth able to directly observe Luna, strongly arguing that its existence is not dependent upon being observed.


Personally, when physicists start asking questions like whether or not the moon exists independently when it is not being observed, or whether the entire universe that we observe, right down to the Planck level, is a holographic projection from the boundary of the universe, I have a tendency to consider it a descent into solipsism and navel-gazing.

[vatine]

Sometimes, it is enlightening, mostly I suspect it's self-indulgent formula-wank.

Of course, for people who claim that it's all a simulation, the answer would be that the Moon may or may not have existed in the past, but now all evidence is consistent with that fact (I guess, to some extend, that's terribly post-mortem^Wmodern).

[ithildae]

I play with my words. Scientists play with their assumptions. From, limited, observation, I believe the same sense of human is in play. There is something perverse in people that causes us to use humour to select listeners that have similar backgrounds and understanding. My button that states, "Heisenberg may have been here" is a case in point. (Or, "Poor Heisenberg, he know exactly how fast his keys are going".)

It is important to understand that our methods of pursuing science is developed as a branch of philosophy. Often, scientists want to poke as much fun of that particular way of thinking as the rest of us. No matter how useful philosophy is in the main, at the edges, it gets stupid.

[unixronin]

There's a joke about Werner Karl Heisenberg being pulled over by a state patrolman for speeding.
"Sir, did you know you were doing 93mph?"
"Dammit, officer!  What did you have to tell me that for?  Now I'm lost!"

[ithildae]

That is very nice! Thanks for sharing.

[ithildae]

My very thought for an example.

[unixronin]

Actually, from the discussion thread on the LiveJournal side, one of the points that came up is that at the quantum mechanical level, it's pretty close to the point where just existing in the same universe as an event effectively counts as observing it. The problem is less one of what counts as observing something, than one of trying to determine whether it is meaningfully possible NOT to observe something if it was possible at all for you to observe it. To all practical purposes, it's a case of "If you could have observed it, then for quantum mechanical purposes, you did, even if you didn't."

Of course, extending this to the macroscopic classical scale is a different kettle of fish altogether.