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Caledonian2 comments on Belief in the Implied Invisible - Less Wrong

30 Post author: Eliezer_Yudkowsky 08 April 2008 07:40AM

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Comment author: Caledonian2 08 April 2008 10:56:15PM 1 point [-]

Should I believe that, in the moment where I can no longer interact with it even in principle, the photon disappears?

No.

It would violate Conservation of Energy. And the second law of thermodynamics. And just about every other law of physics. And probably the Three Laws of Robotics. It would imply the photon knows I care about it and knows exactly when to disappear.

1) The Second Law is a non-sequitur. It simply isn't relevant. The loss of a photon due to universal expansion does not violate that principle at all.

2) The First Law was formulated when we found that, in our attempts to examine situations where it was asserted substance was created or destroyed, substance was always conserved. It exists on empirical grounds; it's not some sacred revelation that cannot be questioned or even discarded if necessary. Citing the First Law against the idea that a bit of mass-energy *could* be destroyed is simply invalid, because if that substance could be destroyed, we'd have to abandon the Law.

3) The idea that "the photon knows when to disappear" is based on a mistaken understanding of existence. It is not an inherent property of a thing, but a relationship between two or more things. The photon doesn't keep track of how far it's gotten from Eliezer and then lose the "existence" property when it's distant enough. Its existence relative to Eliezer ends when it passes forever out of the universe in which things interact with Eliezer.

There is no difference between saying that a photon that travels far enough away from Eliezer is destroyed, and saying that a photon that travels far enough from Eliezer is no longer part of the set closed under interaction that includes him. Knowing the properties of the photon would no longer be necessary to completely represent Eliezer and the things that interact with him.

The photon is no more. It has ceased to be! Relative to Eliezer, at least. Whether it exists relative to other things is undefined - and utterly irrelevant.