
The Crisis of the Multiverse - dnetesn
http://cosmos.nautil.us/feature/120/the-crisis-of-the-multiverse
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justinpombrio
> Theoretical and observational evidence suggests that we are living in an
> enormous, eternally expanding multiverse where the constants of nature vary
> from place to place.

Really? What is this evidence? I didn't see much of it in the article.

Also, the "sleeper" argument (at least as presented?) seems to be flawed. To
repeat, the argument is this:

Suppose you are cryogenically frozen, to be woken up in either 1 year or 100
years, determined by the flip of a coin right after you're frozen.
Furthermore, say that the population of the Earth doubles every year, and each
year 1% of people undergo this experiment. Now suppose you wake up, and wonder
how much time has passed. There are two lines of reasoning:

1\. Obviously, the odds are 50/50, since the result was determined by the flip
of a coin. 2\. Whatever year it is, most of the people waking up from the
experiment were frozen last year (when the population of Earth was higher).

The article then concludes that "The fact that two logical lines of argument
yield contradictory answers tells us that the problem is not well-defined."

But they're not contradictory; either may hold depending on what you know. The
probability of an event depends on your knowledge. Assuming you remember when
you were frozen, then there are two possibilities: "I am John Doe who was
frozen in 2020 and woke up in 2021", or "I am John Doe who was frozen in 2020
and woke up in 2120". Thus line of reasoning #1 holds. On the other hand, if
you're an experimenter who's _greeting_ people as they wake up, then there are
many possibilities: "It's 2120, and this was one of the 70 million people who
was frozen in 2020", or "It's 2120, and this was one of the 140 million people
who was frozen in 2119". Thus line of reasoning #2 holds, and the person
you're greeting was probably frozen last year. No contradiction.

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kordless
> The probability of an event depends on your knowledge.

This is a false statement and hints at the dissonance in the argument made for
hard determinism.

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justinpombrio
I'm not saying what you think I'm saying.

I'm not saying that if we had full knowledge, then the future would be
deterministic (on the contrary, I agree that this is false). However, we
almost _never_ have full knowledge, and how much knowledge we have and what
that knowledge is determines the probability of something.

For example, what's the probability that a RNG produces 38434 as its next u32
output? Usually, it's 1/(2^32). However, if I just wrote a program to reverse
engineer your computer's RNG as part of an attack, that program knows
_exactly_ what the next output will be, and to it, the probability is either 0
or 1. Or take another example. You're teaching a probability class, and I'm a
student who has just taken your test. What's the chance that I fail? To you,
who doesn't know much about me, the probability is 5%, since only 5% of your
students fail the first test. But _I_ know that I didn't study, and peg it at
50%.

So again, the probability of an event depends on your knowledge.

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YeGoblynQueenne
But your knowledge of stochastic events depends on the number of observations
of the outcomes of those events.

If you know only how well you do in probability tests, you can peg your
chances to pass at 50%, but that doesn't tell you anything about the chances
of the rest of the class.

I think you're arguing that you're just another observer, however you're not.
You're the event and you have some sort of expectation about your outcomes.
The observer here is the tutor, who has seen enough of you and others like you
to have some more or less justifiable state of belief about the outcomes _of
the class_.

Are you needlessly complicating what amounts to a very simple and reasonable
point? You can't know what you don't know until you've seen enough of it to
know it.

This goes for both deterministic and probabilistic knowledge. If you observe
all possible outcomes of an event, you can deterministically predict its
outcomes. If you observe sufficiently many outcomes of a stochastic event, you
can probabilistically predict its outcomes. If you don't observe enough
outcomes - and an infinite event will never give you enough outcomes - then
you're stuck with inaccurate predictions for ever.

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justinpombrio
> You're the event and you have some sort of expectation about your outcomes.

The event is the test grade. I am not a test grade, I am a person. If it's
problematic that I'm _taking_ the test, how about I tell my friend that I
didn't study, and my friend give a 50% probability that I fail?

> you can peg your chances to pass at 50%, but that doesn't tell you anything
> about the chances of the rest of the class.

I wasn't talking about the rest of the class, I was talking about the
probability that the _professor_ would give _me_ of failing the test. Is your
probability theory so weak that it refuses to make a prediction for that? What
are we supposed to use instead, our gut feelings?

> If you observe all possible outcomes of an event, you can deterministically
> predict its outcomes. If you observe sufficiently many outcomes of a
> stochastic event, you can probabilistically predict its outcomes.

The laws of probability apply just as well to deterministic and stochastic
events. There is no useful distinction between a deterministic event of which
we have partial knowledge (enough to assign a good "probability" to each
outcome), and stochastic events of which we have full knowledge. As an
example, take a board game that uses dice. How does the gameplay change if we
replace the dice with a seeded RNG picking numbers from 1-6? Moreover, think
of your favorite (classical) stochastic process. What if it's secretly
deterministic, but only you know enough information -- an impractically large
amount of information? What changes?

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nonbel
There is some interesting background to Nautilus magazine. It is funded by an
organization that has the goal of using scientific methods to prove
"spiritual" stuff. Since the "spiritual dimension" is so ill defined and hand-
wavy, this requires pseudoscientific methods.

I am one who sees _a lot_ of pseudoscience out there these days. Undeniably,
the primary funding source is US taxpayers, but this looks like another one.

[http://www.nature.com/news/2011/110216/full/470323a.html](http://www.nature.com/news/2011/110216/full/470323a.html)

[https://www.templeton.org/what-we-
fund/grants/nautilus](https://www.templeton.org/what-we-fund/grants/nautilus)

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FascinatedBox
I'm not sure why, but this site is adding several history entries. It's even
worse when I try to navigate down using arrow keys.

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derrickdirge
On mobile safari it completely fills the back button history, making it
impossible to actually go back. Pretty egregious UX.

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MattRix
Yeah it's awful, though you can go back if you hold the back button, which
will pop up a list of history entries.

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derrickdirge
That list is exactly what I'm talking about.

By the time I wanted to go back, that list was completely full of links back
to the current page and I had to load HN from my favorites instead.

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woodandsteel
The article assumes that string theory has been proven correct. From what I
understand, that is very far from being true.

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miles7
My impression is that, far from being proven correct, it's actually falling
out of fashion. Some ideas originating in string theory, such as the AdS/CFT
correspondence, are having a heyday though.

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protomikron
Unbelievable, this fucking modern UI designs. How can you publish a page,
where the back button is broken, and just call it a day.

It is freaking text and some images. We know how to do that, there is no
magic, please do not use technology that breaks basic expectations of users.

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trav4225
You must have missed the memo -- back buttons are now "considered harmful". ;)

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nobrains
The crisis of the nautil.us website back button

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trav4225
BackGATE!

