Boltzmann brains

[unixronin]

New Scientist for August 18-24 contains an article talking about Boltzmann brains and the nature of the Universe.  (The concept of the Boltzmann brain is basically this:  We know elementary particles are constantly popping in and out of existence from quantum vacuum fluctuations.  Occasionally, entire atoms pop into existence in this way.  The more complex a construct, the lower the probability of its spontaneous appearance.  Theoretically, given a sufficiently large space and a sufficiently long time, quantum fluctuations should cause complete functioning consciousnesses able to observe the Universe to spontaneously pop into being.)  Much of the thread of the article seems to center around discussion of how crucial it is that Boltzmann brains never outnumber physical human observers, because if that happened we wouldn't be typical of the Universe, and everything we know might go poof.

Oh, boy.  There's that old anthropic bugbear raising its head again.  Let us suppose that tomorrow, some theorist irrefutably proves that, 10^{10^30} years from now, Boltzmann brains will dominate the Universe.  Would his proof cause the universe as we know it to suddenly disappear in a flash of logic?  I rather doubt it.  (In fact, were we able to somehow prove that Boltzmann brains becoming the majority obeservers of the Universe would cause the end of existence as we know it, it would logically follow that, at least for now, such quantum observers do not outnumber us.)  Does it even MATTER whether we are typical observers of the Universe, or whether our little corner of it is typical?  Again, I rather doubt it.  Nothing that happens to the Universe in the deep future can possibly affect the demonstrable fact that right now, we and our little hospitable corner of the Universe exist.

I propose that we will never fully understand the Universe, so long as our theories about the nature of the Universe are unconsciously built atop a foundation that says it is necessary we remain somehow significant to the Universe, even if only by virtue of being a typically representative sample of it.  I roll to disbelieve that the Universe as a whole gives a blind tinker's damn (figuratively speaking, of course) whether we exist or not.

This, I think, is modern science's version of arguing about how many angels can dance on the head of a pin.

Comments

[unixronin.livejournal.com]

Oh, and I meant to add, yes, at the quantum level our best models seem to indicate that one cannot observe an event without influencing it in the process. But as far as we can tell, that effect is significant only at close to the quantum level, and has long since disappeared by the time we reach the scale of everyday objects, let alone the universe as a whole. If I look at a plant in my front yard, the photons by which I see it have already completed any interaction with the plant that they're going to before they even reach my eye, and that interaction is unchanged by whether or not my eye happens to subsequently capture those photons (i.e, by whether or not I happen to look out the window).
Apart from anything else, we observe most of the universe as it was long before we even existed to observe it. If our observation of an object so far away that the solar system didn't exist yet when the light we're observing it by began its journey to us, changes that object in time for us to observe the change, then causality is broken and practically the entire structure of physics as we know it collapses.

[johnkzin.livejournal.com]

If I look at a plant in my front yard, the photons by which I see it have already completed any interaction with the plant that they're going to before they even reach my eye, and that interaction is unchanged by whether or not my eye happens to subsequently capture those photons (i.e, by whether or not I happen to look out the window).

That's not necessarily true. There was a paper several years ago that I read where they looked at light coming through the gravitation lens of galaxy A from galaxy B. They were able to perform the standard wave interference vs particle experiments on the light ... observer affecting outcomes of events that happened millions or billions of years ago.

I also heard about (but didn't see a paper for) an experiment where pictures were taken of events and then data randomly sampled to look for particles vs waves, well after the events happened and the pictures all turned out to match the observations (as in, you couldn't look for a particle in the data, and then hope to see a picture of wave interference in the picture, getting around the problem that way: if you looked for a particle in the data, you got a picture of particles, if you looked for wave patterns in the data, you got a picture of waves ... even though both the revelation of the picture and the analysis of the data were both happening well after the event in question).

So, it's not unreasonable that you're affecting the photons hitting the plant, even though the photons aren't getting to your eyes until much later.

Time doesn't play the role that we think it does, in these situations :-}

[unixronin.livejournal.com]

That's not necessarily true. There was a paper several years ago that I read where they looked at light coming through the gravitation lens of galaxy A from galaxy B. They were able to perform the standard wave interference vs particle experiments on the light ... observer affecting outcomes of events that happened millions or billions of years ago.

Well, that's one interpretation. I don't buy the idea that there's retroactive causality taking place — I think it's just that you can observe wave/particle duality in light regardless of how long it took the light to reach you or from how far away, simply because photons exhibit wave/particle duality.

As for roles played by time, I don't think we really understand time well enough to be able to say what it does. We still can't be sure it's not merely a perceptual illusion.