This thread is for asking any questions that might seem obvious, tangential, silly or what-have-you. Don't be shy, everyone has holes in their knowledge, though the fewer and the smaller we can make them, the better.
Please be respectful of other people's admitting ignorance and don't mock them for it, as they're doing a noble thing.
I was into dinosaurs when I was a kid, and now I'm teaching my kids about dinosaurs. In light how much our understanding of dinosaurs has drifted in 30 years, and after learning about how certain dinosaurs species are basically extrapolations based on, like, a single bone, I'm trying to get a sense of what we actually know about dinosaurs versus what is just being made up to fill in the gaps.
As an example of what I'm talking about, the wing span for quetzalcoatlus keeps being revised downward. They seem to have a few skeleton fragments, and then they extrapolated what the rest of the skeleton looked like based on other species which they assume to be similar. I find myself wondering if at some point they're just going to come out and say, "Yeah, this thing never flew at all, the assumption that it was just a bigger version of other azhdarchid species was completely wrong, sorry." Sometimes I read passages that suggest that pterodactyls may not have been fliers at all.
We've seen many similar revisions, such as the famous "T. Rex was a scavenger" and "all these dinosaurs had feathers". So if I had a pithy version of this "stupid question" it would be "What do we actually know about dinosaurs?"
I think that the basic answer is that they were really big, and looked kind of like dinosaurs. We certainly know more than that, but most of what we know is either highly technical, or just deductions that you might not want to consider "really knowing". There is also a third category, with things like "laid eggs" and "underwent a mass extinction event" that you already know and are probably not interested in hearing about again.
It is worth noting that although they were the dominant land animal for about 135 million years, we only have about 1,000 clearly identified species (to help put this in perspective, we have two clearly defined species identified in the genus Triceratops, one of the most recent of the dinosaur genera... as opposed to, for example, about 30 species for the genus Homo {not a very prolific genera}. These two genera, Triceratops and Homo, spent approximately the same amount of time on planet Earth.) It is possible that the less than 1% of dinosaur species that we happen to have stumbled across are a good representative sample of the clade, but it is also possible that they are not.
But... We do know that many dinosaurs had feather-like structures. We do know that T. Rex could eat you, even if you were hiding in your car, and there is some evidence of them attacking live prey (prey that escaped with wounds that were able to start healing before they died). Pterodactyls could fly, although some early scientists in the 17-1800s doubted this, and for a while it was believed to be a swimmer. (But pterodactyls are not technically dinosaurs).
Studying dinosaurs is still just peeking at the very edge of a very large and mysterious world, and that is probably more useful for kids to learn about than hunting down the few facts we know for sure. But I do agree that the information out there is not presented very well; it should all be in the form "we think X because of Y", but it is generally boiled down for popular audiences to something like "MAYBE X!"
Once in a while I read somewhere online an article that tells people not to worry about sexually transmitted diseases, because they are rare, and most of them can be easily cured by antibiotics anyway, so the dangers of having a lot of sex with random people are exaggerated. (And then the article often becomes political and starts explaining why the bad guys -- the conservatives -- want to scare you into having less happiness in your life. Because they are stupid and evil, duh.)
How realistic is this? The argument about frequency of diseases in population ignores the fact that the risk is not distributed evenly. For reasons similar to "why your average Facebook friend has more friends than you (because having a lot of friends makes them also more likely to become your friend)", having a lot of sex with random people will make you more likely to have sex with partners who also have a lot of sex with random people, therefore the risk is higher than the statistics calculated for people with average behavior would suggest. (Seems to me that the usual hypocrisy could actually be a good strategy here: if you decide to have sex with many partners, it still makes sense to avoid people known to have sex with many partners.)
However the part "can be cured by antibiotics" also deserves some attention. The words "can be" do not necessarily imply ~100% success, although the article can make such impression. If I understand it correctly, using antibiotics is like carpet bombing the microorganisms in your body: you will do a lot of damage to your gut flora, but the intended target is likely to survive. Also here is the evolutionary arms race against the diseases: the more people rely on the "antibiotics can cure anything" strategy, the greater evolutionary pressure there is on bacteria to mutate into variants resistant to the known antibiotics. And the bacteria can mutate much faster than we can invent new antibiotics. This seems like a "tragedy of commons" scenario.
I'm interested in your opinions in general, but especially whether my reasoning about the antibiotics is more or less correct.
(I am not any kind of medical expert, so the value of this comment is very limited. But you did ask for general opinions.)
I think you are clearly correct about the likelihood of encountering a partner with an STD being higher than naive calculations would suggest. It isn't clear to me how much higher. If you are at least taking typical safe-sex precautions then the probability of transmission can be quite low even if your partner does have an STD; I fear there's no good substitute for actually doing the calculations, for someone who actually wants to make a sensible decision on this and would if possible like to have a lot of sex with a lot of people.
My impression (based on almost exactly zero information) is that antibiotic treatment for most STDs is very close to 100% successful at present, but I would be concerned about hastening the development of antibiotic resistance in STDs, on account of the implications for other people. (If you[1] can guarantee that if diagnosed with an STD and treated with antibiotics you will have absolutely no sex with anyone until you're definitely cured, maybe that's not a factor.)
Also, of course, antibiotics will do you no good at all if you get, say, genital herpes or HIV.
[1] Meaning a hypothetical person wondering about this stuff for practical reasons, not necessarily you.
the dangers of having a lot of sex with random people are exaggerated
This is one of those "bravery debate" things. The statement is not precise enough to be true or false. Some people definitely overestimate the risks. Are they the audience for this? Are you among them? I don't know.
My possibly stupid question is: "Are some/all of LessWrong's values manufactured?"
Robin Hanson brings up the plasticity of values. Humans exposed to spicy food and social conformity pressures rewire their brain to make the pain pleasurable. The jump from plastic qualia to plastic values is a big one, but it seems plausible. It seems likely that cultural prestige causes people to rewire things like research, studying, etc. as interesting/pleasurable. Perhaps intellectual values and highbrow culture are entirely manufactured values. This seems mildly troubling to me, but it would explain why rationality and logic are so hard to come by. Perhaps the geek to nerd metamorphosis involves a more substantial utility function modification than merely acquiring a taste for something new.
I'm not a biologist, but am I right in thinking that Crispr could be the most important human innovation ever? This Wired article claims that a knowledgeable scientists thinks that the "off-target mutations are already a solved problem." Within a decade we should know a lot about the genetic basis of intelligence. Wouldn't it then probably be easy to create embryos that give birth to extremely smart people, far smarter than have ever existed?
Unfortunately I have to retract my above statement, I checked https://www.reddit.com/r/Futurology/comments/3fri9a/ask_aubrey_de_grey_anything/ .
Q:Does it speed up the development timeline at all? A:Aubrey de Grey, SENS[S]: A lot, yes.
No concrete timeframe, but he also gives estimates:
https://www.reddit.com/r/Futurology/comments/3fri9a/ask_aubrey_de_grey_anything/ctr90ru
Seems as if he gives a 50yo has about 50% chance to be around when SENS comes.
Emphasis on probably -- intelligence is not a simple matter, and it is unclear that our genome, even if we clearly identify all relevant factors, would be "open ended" -- that is to say, there may be a difference between "making you as smart as you can be" and "making you smarter than any human ever". As a poor analogy, we will certainly soon be able to make humans taller, but there may be limits to how tall a human can be without important system failures; we have already had very tall people, and even if we do want to breed for tall, we might choose to top out at 7'0" for health reasons. Likewise, when you think of smart people, it may be that you are thinking of people with skills maximized for specific functions at the cost of other functions, and a balanced intelligence might top out at some level... at least until we get past mapping what we have and into the much harder task of designing new types of genomes.
I'm not a biologist, but am I right in thinking that Crispr could be the most important human innovation ever?
There are several competing techniques. People who use the other techniques think that CRISPR mostly has better PR, and is a fairly minor technical innovation. Gene editing, regardless of the technique involved, will be tremendously important for the next few decades.
Why can I hear noise (white noise / pink noise / brown noise), but not hear temperatures?
EDIT FOR CLARIFICATION Air temperature is caused by air molecules moving randomly at high speed, white noise is caused by air molecules moving randomly at high speed, what's the difference? Why does white noise fill the room with sound instead of just raising the temperature slightly?
My hand-wavy-sounds-like-science-technobable guess is that temperature does fill the air with sound, but most of the energy of that sound is at far too high frequencies for my eardrums to detect (in part because my eardrums are emitting noise at a those frequencies). Maybe the average wavelength of thermal noise is roughly the mean free path length of the air molecules, so the average frequency of the noise is roughly 5 GHz. But I just making stuff up and really don't know.
You can't hear temperatures because if the temperatures of air were high enough to make enough noise for you to hear, you would be incinerated.
http://physics.stackexchange.com/questions/110540/how-loud-is-the-thermal-motion-of-air-molecules goes over this. There is a lot of error in that thread, but the parts that are right show up a few times and calculate the white noise sound level of room temperature air at about -20 dB SPL. SPL of 0 dB is the approximate threshold of human hearing. dB is a logarithmic scale such that every 10 dB increase is a 10X higher power. So -20 dB SPL is about 1/100 the average sound power level that would just barely be audible by a human. This is calculated at something close to room temperature, about 23 C which is about 300 K.
How hot would air have to get to have its thermal fluctuations audible as sound to humans? Any thermal power (at sufficiently low frequencies which situation applies here) is proportional to the temperature. So to increase the thermal sound level from -20 dB to 0 dB, the sound power needs to be increased by a factor of 100. So this would happen at an absolute air temperature of 30000 K, or about 29700 C. For us Americans, that is 53500 F. Super crazy hot, hotter than the sun.
So wait a minute, am I saying that a white noise generator generating 0 dB (barely audible) white noise is heating the air to super-solar temperatures? That doesn't pass the smell test: if it was true my ears would be burning off when exposed to any white noise loud enough for them to hear. But the answer is, we are only generating white noise over a very small frequency range in order to hear it. Even a high fidelity white noise generator will have a bandwidth covering about 50 Hz to 20,000 Hz. But the "natural" bandwidth of thermal fluctuations is found from quantum mechanical considerations: BW = T * kb/h or bandwidth is Temperature(in Kelvin) times Boltzmann's constant divided by Planck's constant. That ratio kb/h turns out to be about 20 GHz per degree K. So thermal noise loud enough to hear would have a bandwidth of 600,000 GHz or 6e14 Hz. TO an approximation, thermal power is proportional to bandwidth, so a 20 kHz white noise generator putting out 0 dB SPL is putting out only 20000/600000000000 = 1/30000000000 the power level associated with a 30000 K source. So in terms of TOTAL energy, a band-limited white noise source is delivering way less than 1 K of extra temperature to your ears, even though in terms of energy density (power per bandwidth), it sounds hotter than the sun.
Much of the thread below covers some of this, but perhaps I add a little detail with what I write. As to blackbody radiation, yes that is appropriate to use here and its upper frequency limit has nothing to do with electromagnetics, or not fundamentally. It is a quantum mechanical limit. At a high enough frequency, the quantum of energy becomes comparable to the thermal energy, and so at higher frequencies than that those frequencies can't be effectively generated by thermal sources. This is true for both photons (electromagnetic energy quantized) and phonons (sound or vibration energy quantized).
Hope this is clear enough to add more light than heat to the discussion. Or in this case, more sound than heat :)
white noise is caused by air molecules moving randomly at high speed
This is wrong. What you hear is sound waves, that is, rarefaction/compression zones in the air, pressure differentials. They are a phenomenon at a different scale than molecules. In particular, the energy involved is different. "White noise" means the frequencies are uniformly distributed.
Essentially, an air molecule doesn't have enough energy to register at your hearing sensors, that is, to move your eardrum (or cochlear hairs).
Essentially, an air molecule doesn't have enough energy to register at your hearing sensors, that is, to move your eardrum (or cochlear hairs).
Though, now that I'm thinking about it, if the white noise generator I bought to help me sleep is really good at producing white noise with uniform power at high enough frequencies, an air molecule would have enough energy to move my eardrums. I would also be on fire.
And if my white noise generator is really really good at producing white noise with power uniform across all frequencies, the noise's mass-energy will cause my bedroom to collapse into a black hole and I will be unable to leave a 5 star review on Amazon.
The peak frequency of thermal noise at room temperature is far higher than 5 GHz, it's actually closer to 30 THz. I'm not exactly sure about the biology here and whether Brownian motion of air molecules excites the hair cells in your cochlea. I'm guessing that it does, but even so, the range of frequencies you can hear (20-20,000 Hz) carries only a very, very tiny fraction of the thermal energy. Someone should do the calculations; my guess is that it's far below the detection threshold.
Another thing to keep in mind is that at equilibrium, you have thermal excitation everywhere. You might as well ask why you don't hear or see or smell the thermal excitation in your own brain.
whether Brownian motion of air molecules excites the hair cells in your cochlea
As far as I remember, you need to hit the resonant frequency of a particular hair to trigger a "sound" response, so frequencies higher than 20KHz might excite them, but if you're not getting resonance, nothing triggers.
As far as I remember, you need to hit the resonant frequency of a particular hair to trigger a "sound" response, so frequencies higher than 20KHz might excite them, but if you're not getting resonance, nothing triggers.
No this is wrong. Each hair is excited by the amount of its particular resonant frequeny in the sound hitting it. If a violin note is heard, that note only has a few discrete frequencies in it and so a few hairs are very excited about it and the brain (of the trained violinist with perfect pitch anyway) goes "oh, A 440." If white noise loud enough to hear is hitting the ear, then essentially all the hairs are excited because all frequencies are present in white noise, and the brain goes "sounds like the ocean."
As to excitement by sound above 20 kHz, a very high frequency ultrasound, say at 100 kHz, can be modulated with the vibrations associated with a violin string, much as sound can be modulated on radio carriers. Such ultrasound hitting a human ear can actually cause the appropriate hairs to be excited so that the brain goes "oh, A 440." The phenomenon relies on the non-linear response of cochlear hairs and highly directional speakers based on this effect have been built and demonstrated. See for example http://www.holosonics.com/
Repeating my question from late in the previous thread:
It seems to me that if you buy a stock, you could come out arbitrarily well-off, but your losses are limited to the amount you put in. But if you short, your payoffs are limited to the current price, and your losses could be arbitrarily big, until you run out of money.
Is this accurate? If so, it feels like an important asymmetry that I haven't absorbed from the "stock markets 101" type things that I've occasionally read. What effects does it have on markets, if any? (Running my mouth off, I'd speculate that it makes people less inclined to bet on a bubble popping, which in turn would prolong bubbles.) Are there symmetrical ways to bet a stock will rise/fall?
It gets very interesting if there actually are no stocks to buy back in the market. For details on how it gets interesting google "short squeeze".
Other than that exceptional situation it's not that asymmetrical:
-Typically you have to post some collateral for shorting and there will be a well-understood maximum loss before your broker buys back the stock and seizes your collateral to cover that loss. So short (haha) of a short squeeze there actually is a maximum loss in short selling.
-You can take similar risks on the long side by buying stocks on credit ("on margin" in financial slang) with collateral, which the bank will use to close your position if the stock drops too far. So basically long risks also can be made as big as your borrowing ability.
if you buy a stock, you could come out arbitrarily well-off, but your losses are limited to the amount you put in. But if you short, your payoffs are limited to the current price, and your losses could be arbitrarily big, until you run out of money.
This is accurate.
it feels like an important asymmetry
This asymmetry comes from the fact that prices are non-negative numbers and do not dip below zero.
Effect on the market? Off the top of my head, here is a couple: long-term shorts are more risky than they seem; and shorting penny stocks (stocks with a low price, typically below $5) is also "extra" risky because your upside is small, but your downside is not.