4 ms·
Can you explain the math as to how you know there is a 10% chance that we're seeing the US in the last 10% of its history? I don't understand that part.
by moheeb 11y ago
Can you explain the math as to how you know there is a 10% chance that we're seeing the US in the last 10% of its history? I don't understand that part.
- charrisku 11y agoHe's saying that if you looked at the whole history of the US and divided that into 10 equal parts, then there would be a 10% chance of any random observation falling into the last part. Hence, all else equal, we have a 10% chance that we are looking at the US in the last 10% of it's history.
- hamburglar 11y agoThis would imply that there is also a 10% chance we are currently looking at the first 10% of the country's existence, which means you have confidently calculated the odds of the USA lasting at least 2350 years at 10% based on absolutely nothing. These probabilities are nonsense.
- btilly 11y agoIf we assume that we're observing at a random point in our history, we are equally likely to be observing at a point in the first 10%, second 10%, third 10%, and so on. That's what the assumption means. Which means there is a 10% chance that we're observing in the last 10%. See https://en.wikipedia.org/wiki/Doomsday_argument https://en.wikipedia.org/wiki/Doomsday_argument for the most famous use of this line of argument. (It concludes that the human species is likely not long for this universe.)
- Kluny 11y agoThere's something seriously squirrely about that math.
- grillvogel 11y agoI really don't think thats true and I also don't think that your doomsday argument link relates to what you are claiming either.
- btilly 11y agoThe conclusion absolutely follows from the assumption. But there are two questions. 1. Is that a reasonable assumption to make? (In a surprisingly wide variety of cases, yes. But not always.) 2. How do we update the conclusion of the argument given a variety of other information that we have available to us? For example we have a great deal of information about the US system of government, current political state, potential threats, and so on.
- grraaaaahhh 11y agoWhat's stopping us from applying this math to other things? Like, every baby at the 1 minute mark of their life. Shouldn't that mean that ~10% of all babies born dies within a minute and a half? We can take this to extremes. At the 1 minute mark we have a 99% change of being in the latter 99% of their life (and thus a 99% chance of dying 99 minutes later). It's amazing how many of them beat these odds.
- Houshalter 11y agoIt's an uninformative prior (https://en.wikipedia.org/wiki/Prior_probability#Uninformative_priors https://en.wikipedia.org/wiki/Prior_probability#Uninformativ...). Meaning it's the best estimate you can make, if you don't have any additional information about the problem. Obviously we have a lot of additional information on human lifespans, which allows us to build a more accurate probability distribution. Also see my comment above.
- smellf 11y agoNope, your example would be true if we didn't know how long babies lived, and we were observing a baby who was a minute and a half old.