## What-If 0065: "Twitter Timeline Height"

What if there was a forum for discussing these?

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rmsgrey
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### Re: What-If 0065: "Twitter Timeline Height"

Simon_Jester23 wrote:Well, the trick is that you get very different results from applying the assumption of mediocrity to "this randomly chosen person is probably part of the middle of the set of all humans that exist" and saying "this randomly chosen year is probably part of the middle of the set of all years in which humans exist."

Both assumptions are equally valid, but they yield very inconsistent results- because human population has grown so rapidly that if we today are anywhere near the middle of the span of existence of the species, we are probably very close to the beginning of the list of all humans to be born.

Which to me undermines the whole assumption. How can you respect a statistical assumption that gives mutually contradictory predictions when used to analyze two different valid datasets from the same reality?

"This year" and "this person" are both chosen by someone contemplating the doomsday problem. It seems likely that "this year" is going to be heavily non-uniform, with a strong bias towards years with higher population, while "this person" is going to be a lot closer to uniformly distributed over the historical population...

gmalivuk
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### Re: What-If 0065: "Twitter Timeline Height"

mcdigman wrote:My point here is that if there's any nonzero probability for any human to survive to the end of the universe (or an arbitrary point far in the future), then any attempt to put a finite value on the expected lifetime of the human race is going to be confounded by extremely high variance, so in the absence of strong prior reasons to believe otherwise, the best assumption is to assume you are in the first 5%.
So because there are distributions with infinite variance, it's best to assume (for no particular reason) that we're among the forst 5%? Doesn't your reasoning apply equally well to assuming we're among the first 1%? How about the first 0.001% of humanity?

The fact is, reasonable guesses about the future don't have infinite mean or variance, because the universe itself will eventually become uninhabitable by humans.

In particular, an exponential distribution contradicts your statement. If a person has about a 0.1% chance of dying each year, independent of all other years, then there is a nonzero probability one will survive to any arbitrary point far in the future. And yet, there is a perfectly well defined expected value and standard deviation of 1000 years.
Unless stated otherwise, I do not care whether a statement, by itself, constitutes a persuasive political argument. I care whether it's true.
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mcdigman
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### Re: What-If 0065: "Twitter Timeline Height"

gmalivuk wrote:
mcdigman wrote:My point here is that if there's any nonzero probability for any human to survive to the end of the universe (or an arbitrary point far in the future), then any attempt to put a finite value on the expected lifetime of the human race is going to be confounded by extremely high variance, so in the absence of strong prior reasons to believe otherwise, the best assumption is to assume you are in the first 5%.
So because there are distributions with infinite variance, it's best to assume (for no particular reason) that we're among the forst 5%? Doesn't your reasoning apply equally well to assuming we're among the first 1%? How about the first 0.001% of humanity?

The fact is, reasonable guesses about the future don't have infinite mean or variance, because the universe itself will eventually become uninhabitable by humans.

In particular, an exponential distribution contradicts your statement. If a person has about a 0.1% chance of dying each year, independent of all other years, then there is a nonzero probability one will survive to any arbitrary point far in the future. And yet, there is a perfectly well defined expected value and standard deviation of 1000 years.

Of course there's a nonzero probability of them surviving far into the future - their lifetime in that scenario obeys a geometric distribution. As you said, over enough trials it would converge almost surely to a mean lifetime of 1000 years. The distribution I described is also a geometric distribution, but because it also has an exponential value function, it does not converge.

I also didn't claim humanity's true survival rate has infinite mean, just potentially extreme (not infinite) variance - if, for example, we colonize 1 planet in a different solar system, the expected number of humans and lifetime of the species increases incredibly, because now 2 simultaneous planetary catastrophes are necessary for extinction. In addition, if we make it to one star, chances are we can make it to more, and with 10^11 stars in are galaxy, that gives the possibility of sustained exponential growth rate for a long time. Therefore, even if the chance for the species to go extinct in the next 1000 years is high, in the event that it doesn't, the estimate of being in the middle 90% is potentially very very wrong, whereas at worst the estimate of being in the first 5% is only a little wrong.

zedtwitz
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### Re: What-If 0065: "Twitter Timeline Height"

Couldn't one just zoom in and quadruple (or x-tuple) the length of that tower? Good lawd, the possibilities.

Zassounotsukushi
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### Re: What-If 0065: "Twitter Timeline Height"

JeffR23 wrote:If the doomsday argument works today, it would have worked a thousand years ago. If it had worked a thousand years ago, we'd all be dead. We're not dead. Contradiction, so QED: the doomsday argument is silly.

(Also, if it's right the same argument proves we're most likely simulations or intelligences existing in the fleeting, pre-painful death instants of a long series of Boltzmann Brains in deep time, which leads straight to the conclusion of sillyness as well.)

Ah ha - here is one of the few decent posts in this thread. Yes, we have historical president that we are obligated to look at for this argument, and that leads to some interesting quandaries. But most people run around the argument like a chicken with their head cut off.

Also, the simulation argument is ultimately superior. This is an extremely important detail. In a simple sense, we could abandon the doomsday argument in favor the simulation argument easily, but there are problems with that too. The doomsday argument is embodied within the simulation argument. These are the 3 possibilities according to the simulation argument:

(1) the human species is very likely to go extinct before reaching a “posthuman” stage;
(2) any posthuman civilization is extremely unlikely to run a significant number of simulations of their evolutionary history (or variations thereof);
(3) we are almost certainly living in a computer simulation

You can see that (1) is just the doomsday argument. It's also quite likely to be wrong, but not necessarily.

I have a different criticism. My problem lies in the details baked into both the doomsday and simulation argument. Everyone keeps arguing that we are all some Nth human, and that's how we should count things. Only because they are bad at counting. If we were a different species, we would say the same thing for that species. You can argue that ancient Greeks made the doomsday argument, but you could also argue that a Neanderthal did. It was improbable that we were born in those societies compared to living in 2013, so that's not a problem of the theory. The definition of "human" is.

You should include all animals in the history of Earth who were capable of rational thought. You don't know the dinosaurs couldn't! That inflates our baseline from several billions, to an equivalent number of possibly trillions. At least it's enough to make us feel secure through our expansion into space.

Ah, but now you protest that our predecessors of thinking dinosaurs (and other hominids, which is probably a better case-in-point, but I prefer to consider the Velociraptor society that we will discover the remains of after Greenland melts MARK MY WORDS) couldn't have made the doomsday argument, to which I would first reply "why not?" Then after that, I would ask "why should it matter?" If they can think then they were subject to the sample set of intelligent beings that you or I could have been.

Of course, you protest that DINOSAURS DIDN'T HAVE THE INTERNET, and were in a way less sentient. There might be some substance to this, since rational thought has multiplied significantly since the advent of books (likewise for irrational thought after the internet). After all, in the doomsday dilemma, we should focus on the act of reasoning. ...you can't contemplate the doomsday dilemma without thinking.

Right there everything starts to crumble, but it takes a keen eye. Effectively, we've taken the argument itself to define intelligence. There were plenty of humans who never thought of anything important (including several of my own family members). Why should they be included in the sample set? That becomes an extremely dicey proposition, but the true unqualified failure of the doomsday argument comes from the observation that maybe we shouldn't be included in the sample set. How do I know I'm not an idiot?? After all, with the simulation argument, I've already established that the doomsday argument had to be revised, if not completely replaced. This entire class of Bayesian arguments rely on the selection of a sample set for them, and that sample set is connected to who are capable of making those very arguments. There's no way to know if even the simulation argument is worth a crap.

In short, we have no idea how many times we will have to revise the doomsday argument until it says something meaningful. This is a problem, because it affects the selection of the sample set. Now let's consider what will happen when I stumble upon the as-of-yet unknown correct argument. In that case, I should only count myself in the sample set, which means oh shit, the world is about to end any moment now!

What if people who commit suicide really just discovered the correct Bayesian argument that predicts the end of the world? But they knew they couldn't tell us, and for statistical robustness of having a future they selflessly killed themselves.

Twitter. What does Twitter have to do with this? Perhaps a correctly reasoned suicide tweet could bring about the end of the world? What if that's what killed the dinosaurs? Actually, if you look it up, you find that the asteroid that killed them was about 6-10 km in diameter...

http://en.wikipedia.org/wiki/Cretaceous ... e_boundary

...about the same size as... that's right. 4942 Munroe. Which is actually traveling backwards in time to kill the dinosaurs, sent by a cleverly reasoned tweet of someone in the cult of people who logic themselves to suicide with the ultimate form of the doomsday argument.

rmsgrey
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### Re: What-If 0065: "Twitter Timeline Height"

Zassounotsukushi wrote:You should include all animals in the history of Earth who were capable of rational thought. You don't know the dinosaurs couldn't! That inflates our baseline from several billions, to an equivalent number of possibly trillions.

But the dinosaur version of the Doomsday argument was proven correct about 65 million years ago.

If you're talking about intelligent creatures continuing to exist on Earth, then yes, there's a very good chance that there will be intelligent life on Earth half a billion years from now - and I'm sure the cockroaches who are their distant ancestors are thrilled to know that. Sadly that doesn't help with the outlook for the human race...

Zassounotsukushi
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### Re: What-If 0065: "Twitter Timeline Height"

rmsgrey wrote:
Zassounotsukushi wrote:You should include all animals in the history of Earth who were capable of rational thought. You don't know the dinosaurs couldn't! That inflates our baseline from several billions, to an equivalent number of possibly trillions.

But the dinosaur version of the Doomsday argument was proven correct about 65 million years ago.

If you're talking about intelligent creatures continuing to exist on Earth, then yes, there's a very good chance that there will be intelligent life on Earth half a billion years from now - and I'm sure the cockroaches who are their distant ancestors are thrilled to know that. Sadly that doesn't help with the outlook for the human race...

So for the sake of argument, let's considering positing that intelligent life has the sequence of dinosaurs, humans, and then robots.

Humans nearly all die, as the robots they built expand out throughout the universe. A small population of humans are kept in a zoo, consistent with the Doomsday hypothesis (side: what if we're in that zoo right now?). This is a deeply unsatisfying version of the Doomsday hypothesis. It's just not any good. Even in the absence of robots, humans will eventually evolve and become a species that is no longer Homo Sapiens.

The prediction that I am roughly the median individual of life very much like myself is useless. I fail to see why I should care if the future life is like myself or not. Worse, I fail to see why I should not "count" that life when considering the odds of various details surrounding my birth. If I was born a robot, I would still have hopes and dreams, I would still bicker on a forum like this, and I would still write angst-y things about the Fermi Paradox and Doomsday Hypothesis.

rmsgrey
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### Re: What-If 0065: "Twitter Timeline Height"

Zassounotsukushi wrote:The prediction that I am roughly the median individual of life very much like myself is useless. I fail to see why I should care if the future life is like myself or not. Worse, I fail to see why I should not "count" that life when considering the odds of various details surrounding my birth. If I was born a robot, I would still have hopes and dreams, I would still bicker on a forum like this, and I would still write angst-y things about the Fermi Paradox and Doomsday Hypothesis.

On the other hand, if you're attempting to predict how long humans will be around as a species, it follows from the problem statement that you do care whether the future life is like yourself since it being like or unlike yourself changes the answer to the question.

If you don't like the question, that's fine, but talking about answers to different questions doesn't invalidate the answer to the question asked...

Zassounotsukushi
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### Re: What-If 0065: "Twitter Timeline Height"

rmsgrey wrote:On the other hand, if you're attempting to predict how long humans will be around as a species, it follows from the problem statement that you do care whether the future life is like yourself since it being like or unlike yourself changes the answer to the question.

If you don't like the question, that's fine, but talking about answers to different questions doesn't invalidate the answer to the question asked...

But I am invalidating the proposition. Limiting the Doomsday argument to humans, US citizens, or people in my school club all fail. I'm not dismissing the Doomsday argument generally, because there is a correct form, but you are using an incorrect form.

In the What-If comic, an argument similar to the doomsday argument is used for Twitter. A similar statement could be made for humans, but neither case represents a doomsday. The Twitter argument predicts that twitter will probably see its end before the end of civilization. This is roughly correct. It's predicting that Twitter will go the way of myspace. Given 50 years into the future (or even 5, depending on who you ask), Twitter will almost certainly be irrelevant. A similar statement could be made for humans. While some people might think that's the end of the world, it's really not. The larger Doomsday argument actually does predict a doomsday because the known historical experience of intelligent beings is tightly constrained by the Fermi Paradox.

gmalivuk
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### Re: What-If 0065: "Twitter Timeline Height"

Wait, so your problem is calling it "doomsday", rather than any of the particulars of the argument itself?
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Zassounotsukushi
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### Re: What-If 0065: "Twitter Timeline Height"

The "German tank problem" is quite robust logic, and the statistical variation should be fairly self-obvious.

gmalivuk
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### Re: What-If 0065: "Twitter Timeline Height"

Then don't say you've "invalidated" anything.
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Zassounotsukushi
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### Re: What-If 0065: "Twitter Timeline Height"

My apologies for any cases where my posts wound up talking past someone else. I am adamant that I am invalidating a form of the DA proposition, and the entirety of what I wrote is nonsense without that. There are different propositions that I am not arguing against at all, and that seems to be the mismatch. Specifically, I have argued against consciousness-based forms of the DA. The DA is quite often worded to "humans". That certainly complicates things, since "the" DA argument is often taken to mean that. The human race could end without any form of doomsday. You could argue that the end of the human race is actually a trans-humanism statement, and as such, have a "doomsday argument" without any doomsday. This is quite prone to confusion, which I have contributed to.

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### Re: What-If 0065: "Twitter Timeline Height"

I'm still not sure why you stick to the word "invalidate". Your problems seem to be with calling it the doomsday argument because it's not really about doomsday (necessarily), and with the completely subjective choice to pose the question in terms of H. sapiens.

Neither of those choices has anything to do with validity, which is a quality of the logic used and not of how worthwhile you personally find a particular framing.
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Zassounotsukushi
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### Re: What-If 0065: "Twitter Timeline Height"

Your problems seem to be with calling it the doomsday argument because it's not really about doomsday (necessarily)

That statement is much weaker than what we've established so far. There are plausible stories of the future where there the number of humans to-come is very limited and there is not a doomsday at all. If you don't think that's a meaningful objection, then I just don't understand.

However, there is a way to formulate the DA argument such that we're talking about an in-your-face apocalypse (which adds to the confusion of this conversation). Establish the count using all sentient entities. As far as we can tell, this number is very limited, although still quite large. Then we have an argument for which the Fermi Paradox is relevant. In this form, it's in strong opposition to a technological singularity, whereas the form based strictly on humans is in perfect agreement with a technological singularity, via trans-humanism. The singularity would greatly multiplying the number of thinking entities. Any such prediction that foretells a diverging number of thinking entities might be problematic to you, or it might not be. Worse, you could be on either side of that discussion and still claim to adhere to the DA. Regardless of the merits of those specific positions, this nomenclature presents problems in talking about them. I'm trying to get things back on track.

The "What If?" predictions about Twitter are empirically extremely robust. This is because the verb "tweet" and the noun "Twitter" refer to incredibly specific entities which reflect the economic organization of our society in 2013. Consider a future where Weibo (the Chinese Twitter) takes over the planet:

http://us.weibo.com/gb

Predictions about the end of Twitter are still meaningfully robust. That's because we wouldn't count someone's Weibo activity as a part of their Twitter timeline. By making statements about something so culturally specific, it's easy for the prediction to turn out right.

gmalivuk
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### Re: What-If 0065: "Twitter Timeline Height"

Zassounotsukushi wrote:That statement is much weaker than what we've established so far. There are plausible stories of the future where there the number of humans to-come is very limited and there is not a doomsday at all. If you don't think that's a meaningful objection, then I just don't understand.
Sure it's a meaningful objection.

It's a meaningful objection about the name given to the argument. It's not at all the same as an objection about the validity of the argument itself.
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Zassounotsukushi
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### Re: What-If 0065: "Twitter Timeline Height"

gmalivuk wrote:
Zassounotsukushi wrote:That statement is much weaker than what we've established so far. There are plausible stories of the future where there the number of humans to-come is very limited and there is not a doomsday at all. If you don't think that's a meaningful objection, then I just don't understand.
Sure it's a meaningful objection.

It's a meaningful objection about the name given to the argument. It's not at all the same as an objection about the validity of the argument itself.

This is why I have been speaking about the form of the DA that does constitute a true doomsday. The Fermi Paradox is a very strong statement, and if you imagine a space-faring society, the upper limit on the number of future individuals is very large. Let's say that we efficiently dedicated all energy to the maintenance of conscious thinking entities. If I assume those entities are human, then I can easily estimate the lifetime energy use to be 230 GJ. The energy available in the universe is obviously greater by a large margin. Limit the calculation to visible matter in the observable universe, and make conservative assumptions about what energy could be derived from it through (proven) fusion reactions, include a thermal efficiency correction, and you can conclude that 10^66 J would hypothetically be usable via established physics. The temperature of space increasing due to releasing this energy over long time frames is not a concern thanks to the cosmic expansion and acceleration. If all of that energy was dedicated to maintaining humans, we would have 10^53 humans. It can be argued that it's not likely that an advanced society would dedicate all the energy resources in the universe to powering thinking entities, but to defeat the point of the DA, it would have to be unlikely by a factor on the order of 10^42, which is an approximate ratio of the thinking entities we know have existed to the number we know could exist. That's a robust, powerful, argument.

Should I ignore this obvious apocalypse prediction because the DA is commonly written with the word "human"? A decent summary of the DA includes the contentious discussion about the selection of the sample size, of which this is a part of. That strongly indicates that there's not just one DA, and I believe that the ratios I mentioned here are a valid conception of it. So no, I'm not arguing against the DA at all, I'm quite a strong proponent of it! However, it's not a monolithic thing, and there are versions that aren't any good. There are even versions that are proposed tongue-in-check in order to academically sort things out.

I'm still not sure why you stick to the word "invalidate". Your problems seem to be with calling it the doomsday argument because it's not really about doomsday (necessarily), and with the completely subjective choice to pose the question in terms of H. sapiens.

See the Wikipedia article on the DA. It's wasn't my decision to formulate it in terms of humans. They do this over and over again without qualifiers. Maybe it should be edited. I don't know what it means to you. I have put considerable effort into clarifying what positions I'm making a statement on myself.

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### Re: What-If 0065: "Twitter Timeline Height"

I'm not objecting to what you're complaining about or what you want to focus on instead. I'm merely saying that you haven't invalidated anything about the traditional DA just because you have good reasons to focus on a different form of it.
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### Re: What-If 0065: "Twitter Timeline Height"

gmalivuk wrote:I'm not objecting to what you're complaining about or what you want to focus on instead. I'm merely saying that you haven't invalidated anything about the traditional DA just because you have good reasons to focus on a different form of it.

I didn't say "I invalidated the traditional DA" or anything of the sort. I agree that would be incoherent. I had just written a rant about the doomsday argument, simulation argument, and other tangential ideas. The point you keep referencing was in reply to something that was in reply to that. There is a meaningful requirement of the doomsday argument that may not always imposed, but I nonetheless explicitly imposed it in my original post here. In particular, the extension to the simulation argument from the doomsday argument very specifically requires the form of that applies for all consciousness.

I will agree with a modified form of what you're saying when it is established that the goal of "the traditional DA" is "to predict how long humans will be around". While the rhetoric might start out with that kind of wording (depending on the source), it quickly gets into discussion that necessitates statements for conscious entities generally, as my writing did, as the Wikipedia article does, as the simulation argument extension does, and as the word doomsday itself does.

Addition: If I were to define the doomsday argument myself, I would say "it is a resolution to the Fermi Paradox".

wesleyac
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### Re: What-If 0065: "Twitter Timeline Height"

A bug in the Twitter app briefly makes it so you can swipe down to refresh and see future tweets that haven't yet been posted.

Fun fact:
If your timezone setting is behind GitHub's, it'll say things like "WesleyAC authored in 5 hours" and "Last commit in 3 hours".

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### Re: What-If 0065: "Twitter Timeline Height"

Yes, I'm resurrecting this long sleeping thread. why? cuz it's Armaggedon (or is it?)
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Jorpho
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### Re: What-If 0065: "Twitter Timeline Height"

Dang, the link to http://www.econ.umn.edu/undergrad/math/ ... Axioms.pdf in Note 11 is dead. It's on the Wayback machine, but it's pretty brief anyway.

So, how does "The idea of having 'an equal chance of getting every number from 1 to infinity'" violate the Second Axiom?

rmsgrey
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### Re: What-If 0065: "Twitter Timeline Height"

Jorpho wrote:So, how does "The idea of having 'an equal chance of getting every number from 1 to infinity'" violate the Second Axiom?

If every number has the same chance of being picked, then the chances of getting any number at all is either 0 (if each number has 0 probability of being picked) or infinite (if each number has a probability greater than 0 of being picked). There's no way to get a total of 1.