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Cosmologist Sean Carroll: If we are Boltzmann brains, our perceptions are befuddled

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In a universe where we did not evolve so as to understand reality, someone is supposed to have developed a theory by which we need not worry about the Boltzmann brain From Anil Anathaswamy at New Scientist:

 Any theory that lets bizarre brains randomly pop into existence can’t be a valid description of the universe.

No?

No?

That might seem obvious, but such conscious observers, called Boltzmann brains, are inevitable in certain versions of cosmology. New work that claims to banish such theories not only suggests your brain isn’t such an oddity, but tells us which frameworks for the cosmos are the most sound.

Cosmologist Sean Carroll can apparently save us. Whew. Patchy Ausstechformen

Carroll isn’t a fan of Boltzmann brains, and now he thinks he can show they are a bridge too far.

If our brains spontaneously fluctuated into existence, he reasons, then we must be living in the very far future, since the universe needs a near-infinite time for such fluctuations to become a reality. But our measurements suggest that the universe began a mere 14 billion years ago.

That discrepancy means that if we truly are Boltzmann brains in an old universe, then our perceptions are befuddled, too. “We’d have no reason to believe that our memories of the past are accurate,” says Carroll. More.

But wait. That’s exactly what naturalists in cognitive psychology do say. Our brains are shaped for fitness, not for truth, and truth is only sometimes adaptive. Rinse. Repeat.

Anyway, dark energy gets dragged in too, in this piece. But it’s free online.

See also: Saving us from the plague of Boltzmann brains

Dark matter: An invisible civilization could be living right under our noses…
Harvard is buying this? No wonder Peter Woit worries at Not Even Wrong about what physics is coming to.

and

Anti-dark energy theories are burnt toast?

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3 Replies to “Cosmologist Sean Carroll: If we are Boltzmann brains, our perceptions are befuddled

  1. 1
    EDTA says:

    If our brains spontaneously fluctuated into existence, he reasons, then we must be living in the very far future, since the universe needs a near-infinite time for such fluctuations to become a reality. But our measurements suggest that the universe began a mere 14 billion years ago.

    If our brains spontaneously fluctuated into existence, then how could we know that there is a universe, or that it took a long time for our brains to come into existence, or that every universe would need near-infinite time to generate us?

    And isn’t the very act of observing that our universe is (allegedly) 14Gy old assuming that our observations are valid? I.e., that we’re not Boltzmann brains and are looking at a real objective universe?

    Did Carroll just come out from under anesthesia when he wrote this?

  2. 2
    bornagain77 says:

    Boltzmann brain is a comparison of relative probabilities between our entire universe coming into existence in its low entropy state compared to the much lower probability of a single brain ‘fluctuating’ into existence. Carrol, despite his dislike of Boltzmann brain, cannot negate the math:

    The Fine Tuning of the Universe – drcraigvideos – video
    https://www.youtube.com/watch?v=UpIiIaC4kRA

    Multiverse and the Design Argument – William Lane Craig
    Excerpt: Roger Penrose of Oxford University has calculated that the odds of our universe’s low entropy condition obtaining by chance alone are on the order of 1 in 10^10(123), an inconceivable number. If our universe were but one member of a multiverse of randomly ordered worlds, then it is vastly more probable that we should be observing a much smaller universe. For example, the odds of our solar system’s being formed instantly by the random collision of particles is about 1 in 10^10(60), a vast number, but inconceivably smaller than 1 in 10^10(123). (Penrose calls it “utter chicken feed” by comparison [The Road to Reality (Knopf, 2005), pp. 762-5]). Or again, if our universe is but one member of a multiverse, then we ought to be observing highly extraordinary events, like horses’ popping into and out of existence by random collisions, or perpetual motion machines, since these are vastly more probable than all of nature’s constants and quantities’ falling by chance into the virtually infinitesimal life-permitting range. Observable universes like those strange worlds are simply much more plenteous in the ensemble of universes than worlds like ours and, therefore, ought to be observed by us if the universe were but a random member of a multiverse of worlds. Since we do not have such observations, that fact strongly disconfirms the multiverse hypothesis. On naturalism, at least, it is therefore highly probable that there is no multiverse. — Penrose puts it bluntly “these world ensemble hypothesis are worse than useless in explaining the anthropic fine-tuning of the universe”.
    http://www.reasonablefaith.org.....n-argument

    Does a Multiverse Explain the Fine Tuning of the Universe? – Dr. Craig (observer selection effect vs. Boltzmann Brains) – video
    https://www.youtube.com/watch?v=pb9aXduPfuA

    A Matter of Considerable Gravity: On the Purported Detection of Gravitational Waves and Cosmic Inflation – Bruce Gordon – April 4, 2014
    Excerpt: Thirdly, at least two paradoxes result from the inflationary multiverse proposal that suggest our place in such a multiverse must be very special: the “Boltzmann Brain Paradox” and the “Youngness Paradox.” In brief, if the inflationary mechanism is autonomously operative in a way that generates a multiverse, then with probability indistinguishable from one (i.e., virtual necessity) the typical observer in such a multiverse is an evanescent thermal fluctuation with memories of a past that never existed (a Boltzmann brain) rather than an observer of the sort we take ourselves to be. Alternatively, by a second measure, post-inflationary universes should overwhelmingly have just been formed, which means that our existence in an old universe like our own has a probability that is effectively zero (i.e., it’s nigh impossible). So if our universe existed as part of such a multiverse, it would not be at all typical, but rather infinitely improbable (fine-tuned) with respect to its age and compatibility with stable life-forms.
    http://www.evolutionnews.org/2.....84001.html

    GORDON: Hawking irrational arguments – Washington Times – 2010
    For instance, we find multiverse cosmologists debating the “Boltzmann Brain” problem: In the most “reasonable” models for a multiverse, it is immeasurably more likely that our consciousness is associated with a brain that has spontaneously fluctuated into existence in the quantum vacuum than it is that we have parents and exist in an orderly universe with a 13.7 billion-year history. This is absurd. The multiverse hypothesis is therefore falsified because it renders false what we know to be true about ourselves. Clearly, embracing the multiverse idea entails a nihilistic irrationality that destroys the very possibility of science.
    http://www.washingtontimes.com.....arguments/

    Of related note:

    “An explosion you think of as kind of a messy event. And this is the point about entropy. The explosion in which our universe began was not a messy event. And if you talk about how messy it could have been, this is what the Penrose calculation is all about essentially. It looks at the observed statistical entropy in our universe. The entropy per baryon. And he calculates that out and he arrives at a certain figure. And then he calculates using the Bekenstein-Hawking formula for Black-Hole entropy what the,,, (what sort of entropy could have been associated with,,, the singularity that would have constituted the beginning of the universe). So you’ve got the numerator, the observed entropy, and the denominator, how big it (the entropy) could have been. And that fraction turns out to be,, 1 over 10 to the 10 to the 123rd power. Let me just emphasize how big that denominator is so you can gain a real appreciation for how small that probability is. So there are 10^80th baryons in the universe. Protons and Neutrons. Now suppose we put a zero on every one of those. OK, how many zeros is that? That is 10^80th zeros. This number has 10^123rd zeros. OK, so you would need a hundred million, trillion, trillion, trillion, universes our size, with zero on every proton and neutron in all of those universes just to write out this number. That is how fine tuned the initial entropy of our universe is. And if there were a pre-Big Bang state and you had some bounces, then that fine tuning (for entropy) gets even finer as you go backwards if you can even imagine such a thing.”
    Dr Bruce Gordon – Contemporary Physics and God Part 2 – video – 1:50 minute mark – video
    https://youtu.be/ff_sNyGNSko?t=110

    Fine Tuning, Pink Unicorns, and The Triune God – video
    https://www.facebook.com/philip.cunningham.73/videos/vb.100000088262100/1145151962164402/?type=2&theater

  3. 3
    OldArmy94 says:

    So, to add on to what News has said about the multiverse:

    Everything is possible and will occur an infinite number of times EXCEPT:

    1. A supernatural Creator

    AND

    2. Boltzmann Brains

    Nice.

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