[Physicist]

Frankly, none of this sounds Darwinian at all. I suppose they just thought "quantum Darwinism" sounded catchy.

Happily, this tends to happen automatically, because each individual's observation is based on only a tiny part of the environmental imprint. For example, we're never in danger of 'using up' all the photons bouncing off a tree, no matter how many people we assemble to look at it.

If you assemble enough people, those in the back won't be able to see the tree, because others are in the way. The people in front used up those photons, you see (or not, as the case may be).

[PatrickHenry]

Frankly, none of this sounds Darwinian at all. I suppose they just thought "quantum Darwinism" sounded catchy.

Yup. "Charm"ing.

If you assemble enough people, those in the back won't be able to see the tree ...

And if everyone goes home, the decoherence goes with them, the forest reverts to quantum mush, and the elves come out to play.

[snarks_when_bored]

The 'pointer states' are the 'robust' states, which are able to survive and continue to announce themselves to their surroundings. The analogy with Darwinism is a bit strained, I'll agree. Zurek wouldn't be the first physicist to co-opt some aspect of evolution into physics. Lee Smolin comes to mind.

[grey_whiskers]

I betcha this was 'sloppy writing' and the earlier quote meant "don't use up just by seeing." Of course lotsa photons get abosorbed by skin, clothes, hair, or bounced away. Cheers! ...oh, and Merry Christmas!

[StopGlobalWhining]

Speaking of photons, hopefully you will be able to help me understand an aspect of special relativity that I have been puzzling over related to red shift.

Since a photon travels at the speed of light it never ages. It's identical today to the point when it was originally emitted, even if it originated back near the time of the Big Bang. All it's energy on it's journey through spacetime is expended on its motion through the familiar 3 dimensions, so it never advances through the 4th dimension: time.

Am I right so far?

If so, then how does an individual photon arrive at a detector on earth today with a different frequency than when it was originally emitted? The explanations I have read attribute this to the expansion of the universe and the relative motion of the photon and observer.

But I also thought that the relative motion between a photon and an observer were always the constant c, so how does the expansion of the universe change this? Or do we have to invoke general relativity, or am I just very confused?

Physicist, I've always enjoyed your informative postings, your participation in the 1998 March for Justice, and your efforts in defending Don Adams.

[Moonman62]

If you assemble enough people, those in the back won't be able to see the tree, because others are in the way. The people in front used up those photons, you see (or not, as the case may be).

I think the author's point is that you can ask the people with front row seats they saw.