Why indoor lighting is hard to get right and how to fix it 2020-10-28T04:46:22.672Z
A simple device for indoor air management 2020-10-02T01:02:42.471Z
Description vs simulated prediction 2020-04-22T16:40:02.999Z
The unexpected difficulty of comparing AlphaStar to humans 2019-09-18T02:20:01.292Z
Welcome to Less Wrong! (11th thread, January 2017) (Thread B) 2017-01-16T22:25:56.482Z
Stupid Questions August 2015 2015-08-01T23:08:49.398Z


Comment by grothor on Why indoor lighting is hard to get right and how to fix it · 2020-11-03T19:26:32.198Z · LW · GW

Another thing that might be worth considering is that if you want to estimate your body's response to light, a camera-based illuminance meter with a very wide field of view and some amount of clipping is probably better than a standard lux meter with a diffuser, since it will account for whether the light is spread over your full field of view or not.

Comment by grothor on Why indoor lighting is hard to get right and how to fix it · 2020-11-03T19:22:05.995Z · LW · GW

This is a good question. I have not looked, and the closest thing I have done is to measure the color temperature and intensity according to my camera for direct sunlight just before sunset (seems to be about 2700K, 1900lx).

I would think that you could get a decent estimate using SMARTS if you adapted the input file to a ray going through a lot more atmosphere, but I'm not sure. I haven't looked at the code and it might do something like make approximations that only work for short path lengths or low optical densities or something.

Comment by grothor on Why indoor lighting is hard to get right and how to fix it · 2020-11-03T19:18:30.906Z · LW · GW

I just compared my phone (Pixel 3a) to my Uceri meter, using the app that you link to here.

It seems okayish. The main issue with it is that the camera has a limited field of view, so it does not capture light coming from every direction. With the lux meter and the phone both pointed directly at the lamp near my desk, the phone reads about 35% higher than the lux meter, and when they're both pointed at an angle that barely excludes the lamp from the field of view, the phone reads 45% lower than the lux meter. The reading on the lux meter only changed by 4% between these two angles.

I'd say if you're okay with getting within a factor of two, the phone app is fine. The phone and the lux meter seem to agree the best when the lamp is just barely inside the field of view of the camera.

Comment by grothor on Automated intelligence is not AI · 2020-11-01T23:56:12.181Z · LW · GW

It seems to me that there is an important distinction here between "the thing that replaces human cognitive labor" and "the thing that automates human cognitive labor". For example, a toaster might eliminate the need for human cognitive labor or replace it with a non-cognitive task that accomplishes the same goal, but it does not automate that labor. A machine that automates the cognitive labor normally involved in toasting bread over a fire would need to make decisions about where to hold the bread, when to turn it, and when it is finished toasting, by having access to information about how the bread is doing, how hot the fire is, etc. Or maybe people are using these phrases differently than I am expecting?

Comment by grothor on Why indoor lighting is hard to get right and how to fix it · 2020-11-01T22:37:03.527Z · LW · GW

Visors I've seen do not illuminate all that much of your field of view. Plus I'd prefer not to have to wear a thing all the time. But maybe there are better products like this now? Or were you thinking of building something?

Comment by grothor on Why indoor lighting is hard to get right and how to fix it · 2020-11-01T22:35:13.184Z · LW · GW

This is really cool!

I thought about how to do this a while back, but I couldn't think of a good way to do it without it being huge, expensive, or a fire hazard. At the time, I do not think there were bright enough LEDs to really make this work, and I simply hadn't thought of a good way to solve the Rayleigh scattering problem.

I also hadn't thought of the trick with a bunch of boxes with separate LEDs. It seems like you could make a bunch of smaller versions of his larger one (that is, using smaller LEDs with reflective collimators and a layer of colloid for scattering), and get a similar effect without needing such a large volume. I may try this out.

Comment by grothor on Why indoor lighting is hard to get right and how to fix it · 2020-11-01T22:26:36.023Z · LW · GW

Thanks! The last time I was shopping for LED strips, they just weren't bright enough to really light up a room, but it looks like that has changed. I'll add something about this in the post.

BTW, what I was using LED strips for was "UFO lighting" around the base of my bed. The relatively dim, low CCT strips were attached around the bottom edge of my bed frame, with the LEDs pointing toward the floor. The scattered light was just enough to read by, and having the light mainly on the floor was good for not tripping over things if I had to get up in the middle of the night.

Comment by grothor on Why indoor lighting is hard to get right and how to fix it · 2020-11-01T22:23:06.751Z · LW · GW

The biggest reasons why I do not try to do this myself are:

  1. I haven't done enough research to know what a good dose is in terms of wavelength, intensity, and time
  2. It seems hard to build a source that gets the dose right, without basically building a tanning bed
  3. I think it's hard to know what dose you're actually getting

It's also possible that I am unreasonably worried about shining artificial UV light on myself.

Assuming you have an answer for 1 (and that paper looks promising for having a good answer to this), you need to build a source that illuminates your skin in some reasonably even way. This can be hard, since most light sources radiate over a wide angle, so that you get 1/r^2 drop off in intensity. For example, just now I used my lux meter to measure the intensity of the light near my desk on my forehead and my stomach, and they varied by almost a factor of two. One potentially pretty neat way to fix this would be to use some kind of large collimator like the one in that video that Robert Miles mentioned. The intensity will drop off much more slowly with distance from the source, which should make it easier to get a predictable dose, plus our intuitions about dose from the sun will will still sort of work (for example "The part of my skin that is farther from the sun but is normal to the sun's rays is getting more"). If I did build a big sunlight simulator like that, I would be tempted to add in a little UV.

I recently learned that a common way to measure UV dose is to paint something with a white pigment that absorbs UV and reflects visible/IR light, and see how much it heats up when illuminated. I'm not sure how well this would work when the dose rate is less than 10 mJ/cm^2/minute as in that paper. You probably would just want to use a UV index meter, like they did in the Nature paper you linked.

What would be good is to have some kind of inexpensive cumulative dosimeters that you could place on yourself and around in the area where the UV is so that you can check that you're not inadvertently getting way more or way less than you want. A quick Google search for "UVB dosimeter" looks like there are options, but I have not looked at any of them enough to know if they're any good.

Comment by grothor on What risks concern you which don't seem to have been seriously considered by the community? · 2020-10-29T18:56:33.942Z · LW · GW

I do not mean technological development productivity, I mean economic productivity (how much stuff we're making, how many services we're providing).

Comment by grothor on What risks concern you which don't seem to have been seriously considered by the community? · 2020-10-29T16:59:11.249Z · LW · GW

It is plausible to me that this would be fatal to our civilization, in the long run. Eventually we need to stop being biological humans living on the surface of Earth. It is not clear to me that we can move past that without much higher productivity than present day US.

Comment by grothor on What risks concern you which don't seem to have been seriously considered by the community? · 2020-10-29T15:52:26.611Z · LW · GW

I'm worried that much or most of the risk we're facing over the next 100 or so years come from technologies that are not even on our radar. We do not seem to have a great track record for predicting which advancements are coming, and we seem to be at least as bad at predicting how they will be used or which further advancements they will enable. It seems likely to me that AI will make discovery faster and possibly cheaper.

It makes sense to me that we focus on problems that are already on our radar (AI alignment, synthetic biology), and some of our efforts to mitigate those risks might transfer to whatever else we find ourselves up against. And some people do seem to be worried about risks from emerging tech in a very broad sense (Bostrom and others at FHI come to mind). But I'm not sure we're taking seriously enough the problem of dealing with entirely unforeseen technological risks.

Comment by grothor on What risks concern you which don't seem to have been seriously considered by the community? · 2020-10-29T15:40:53.526Z · LW · GW

It is probably correct that we can't bring everyone up to USA level consumption

Do you mean USA levels of consumption in the economic sense or just energy consumption? If the former, this seems like a really big deal to me. But I'm guessing it's not the case. Right now we do many things in energy inefficient ways, because energy is so inexpensive right now.

Comment by grothor on Why indoor lighting is hard to get right and how to fix it · 2020-10-28T19:01:00.605Z · LW · GW

Thanks, I've added those links.

I actually did consider trying to start a bright light company or trying to make an indoor lighting consulting company in late 2016 or early 2017, but decided against it.

Comment by grothor on Why indoor lighting is hard to get right and how to fix it · 2020-10-28T15:39:28.475Z · LW · GW

I agree that it can be hard to manage a large number of fixtures. I know that other people have come up with more clever solutions than I have, but one thing that I have found helps is to plug as many lights as is practical into the same outlet, and use a remote like this one from IKEA: (I'll add this to the article)

Comment by grothor on Why indoor lighting is hard to get right and how to fix it · 2020-10-28T15:03:30.870Z · LW · GW


Sounds about right for CRI. I think there are a couple things going on with it:

  1. CRI is a mediocre measure to begin with, as far as the subjective quality of the light is concerned
  2. As far as I know, there's no oversight, third party measurement, etc

I'm not sure how much of it is bad measurement and how much of it is CRI being a poor metric, but the best 85 CRI bulbs I've seen are substantially better than the worst 90 CRI bulbs, which is why I'm hesitant to tell people to rule out 85 CRI bulbs entirely. I've not encountered any 95 CRI bulbs that are bad, so maybe the better advice is just to go for 95+ CRI whenever possible.

Comment by grothor on A prior for technological discontinuities · 2020-10-14T02:12:47.220Z · LW · GW

AI Impacts states: "32% of trends we investigated saw at least one large, robust discontinuity". If I take my 12 out of 50 "big" discontinuities and assume that one third would be found to be "large and robust" by a more thorough investigation, one would expect that 4 out of the 50 technologies will display a "large and robust discontinuity" in the sense which AI Impacts takes those words to mean.

This seems reasonable, but I think it may be too high. For the AI Impacts discontinuities investigation, the process for selecting cases went something like this:

  1. All technologies <-- Select those which someone brings to our attention, thinking it might be discontinuous

  2. Discontinuity candidates <-- Do some cursory research to see if they're worth investigating in more depth

  3. Strong discontinuity candidates <-- Get data, calculate, and keep those with > 10 years of unexpected progress

  4. Discontinuities <-- Select those that are particularly large and not highly sensitive to methodology

  5. Large and robust discontinuities

That 32% statistic is the fraction of 3) that made it all the way to 5). It seems like your investigation corresponds roughly to calculating the fraction of 1) that makes it to 3). This is useful, because, as you explain, the AI Impacts investigation did not give us evidence about the overall prevalence of discontinuities. Of your list, 8 were things that we investigated, all of which you list as plausibly big discontinuities, except one that was 'maybe' and 'medium'. Of those, we found 3 to be discontinuous, and all of those three were deemed large and robust. So that's 42% if we ignore the 'maybe'.

This suggests that the 32% is too low. But the 42% above is the fraction of categories of technologies and lines of investigation that seemed very promising, and which showed at least one discontinuity somewhere. Some of these categories are quite broad (robotics), while some are rather narrow (condoms). Within those categories are many technologies, not all of which showed discontinuous progress. Supposing that all categories are equally likely to produce discontinuities, this suggests that the base rate is substantially lower, since even if discontinuities are very rare, we might expect most broad categories to contain at least one.

It is plausible to me that it is better to think of AI as one of these broad categories, especially since the potential discontinuities you're flagging do seem to correspond more to advances that substantially changed the field, and less to things that only advance one small corner of it. In that case, the 42% base rate is about right. But I'm not sure if this is the right approach, from an AI safety standpoint, since many discontinuities might be largely irrelevant while others are not. A discontinuity in performance for diagnosing cancer seems unconcerning, while a discontinuity in predicting geopolitics seems more concerning.

Nonetheless, this is interesting! I particularly like the idea of having multiple people do similar investigations, to see if the results converge. Another possibility is to spot check some of them and see if they hold up to scrutiny.

Comment by grothor on A simple device for indoor air management · 2020-10-03T14:44:57.836Z · LW · GW

I cracked the window next to the one with the filter installed, mainly for the reasons you're describing. It doesn't seem to make a huge difference, which makes me think my apartment is fairly leaky.

Comment by grothor on Industrial literacy · 2020-10-02T23:24:09.502Z · LW · GW

Losing a child is one of the worst things that can happen to a person, in terms of long-term well-being. See, for example,,, and

Comment by grothor on Muting on Group Calls · 2020-10-02T20:41:45.301Z · LW · GW

Another recommendation for a wired headset:

I have one and one of my coworkers has one, and I am pretty satisfied with from both ends.

Comment by grothor on A simple device for indoor air management · 2020-10-02T17:01:39.105Z · LW · GW

I think I was just trying to match the CFM of my Coway purifier, since I was using the same filters. I was also worried it would be harder to properly mate a larger/heavier fan to a box. Now that I've actually built the thing, I would say the larger fan is probably better.

Comment by grothor on A simple device for indoor air management · 2020-10-02T04:32:07.551Z · LW · GW

Here are some details that I left out of the main post:

The fan I'm using is this: The filter is this: (a bit expensive, but I figured it made sense to buy filters I can use with my commercial purifier, if I they did not work with the homemade one) This is the duct:

If you're buying a fan, I recommend getting one that does at least 200-250 CFM and is rated for at least 40W. This is what I'm using and it seems okay. You will probably get better results with a more powerful fan. I haven't looked in too much detail into which fans will handle the pressure difference across the filter well, but my impression is that centrifugal fans are better for this. I will likely replace the fan soon. If you want to estimate how much throughput you need, you can use a copy of this sheet (look at the column 'Outdoor air exchange rate required for CO2 steady state (m^3/minute)'):

You don't need to be super meticulous about sealing everything off with tape, except maybe on the parts of the box that are outside. The air pressure pushes the filter against the box, so that helps. I taped the carbon odor filter against the HEPA filter, mainly to give it a bit of protection from larger pieces of stuff outside.

One other perk is that, as assembled, the whole thing makes white noise (or maybe it's pink noise) that is, to my ear, quite pleasant and good for working or sleeping. It's a little annoying if I'm trying to listen to something through speakers.

Comment by grothor on A simple device for indoor air management · 2020-10-02T04:25:14.428Z · LW · GW

What air quality sensor are you using? How are you getting outdoor data?

I'm using one of these:

I get the outdoor data from PurpleAir. There are two stations within a few blocks of me, and they both seem to report very similar numbers, though I have not done anything to formally estimate the error/variance.

Have you thought much about circulation?

Yes, and it does seem to depend somewhat on where the sensor is placed and what the circulation is. I took notes on where it was sitting, but I haven't tried to notice any patterns yet. I had a fan running to circulate air in the room the whole time that data was being recorded. I did not open the door very many times.

Additionally, it looks like indoor PM2.5 is tracking outdoor PM2.5. Have you thought much about other sources of ventilation?

Some, yes. I do expect the indoor PM2.5 to track it at least a little, since I would (naively, at least) expect the filtration system to work linearly (that is, it removes a percentage of particulates that is not dependent on the particulate concentration. But it does not seem to be linear, since it was removing a smaller fraction later in the day when the outdoor concentration was higher. It does seem like this might be explained by a leak somewhere?

I've been considering how hard it would be to build a system that can maintain a positive pressure difference in the house, so that it will reduce particulate inflow through cracks, other windows, etc. I'm not sure how hard that is to achieve.

Have you done experiments of your own?

Comment by grothor on Solar system colonisation might not be driven by economics · 2020-04-24T21:04:05.257Z · LW · GW

Vastly cheaper average cost for resources that can be mined in space might open up opportunities for economically valuable things that we currently won't do on account of the Earth cost of those resources. To use your glass/lake metaphor, if all we have available for water is a dozen glasses per day per person, we probably won't have much of a swimming pool or sprinkler system industry. If we find ways to pipe water from the lake, we might see much more demand for large volumes of water.

Comment by grothor on Discontinuous progress in history: an update · 2020-04-14T20:19:23.558Z · LW · GW

I agree that it would be interesting to look at evidence from further in the past or from non-Western progress.

Unfortunately, we found researching progress from before roughly 1700-1800 (and sometimes even later) to often be quite difficult. Most sources are vague, disagree with each other, or have clear signs of unreliability. Even when we have good accounts of what the state of the art was at some particular time, it was difficult to establish a progress trend leading up to it.

You're probably right that professional historians would be good at sorting some of these problems out. Usually when we did contact subject matter experts during the investigation, they could at help us to reality check out findings, but we did not try to get them to actually do work for us.

Comment by grothor on Rohin Shah on reasons for AI optimism · 2020-04-02T05:10:17.063Z · LW · GW

Neat idea!

If someone here thinks this is easy to do or that they can make it easy for us to do it, let me know.

Comment by grothor on What will be the big-picture implications of the coronavirus, assuming it eventually infects >10% of the world? · 2020-03-02T21:42:38.707Z · LW · GW

Those predictions are based on 80% of cases being mild. My claim is that if 90% of cases are undiagnosed, then substantially less than 20% will be severe.

Comment by grothor on What will be the big-picture implications of the coronavirus, assuming it eventually infects >10% of the world? · 2020-03-01T19:30:13.827Z · LW · GW

I'm also arguing that we might just have many fewer severe cases than these right-tail estimates are indicating. So far, Hubei has only had .1% of their population get confirmed cases, for example, and I think that many scenarios in which >10% of people are infected globally are ones in which the actual number of cases in Hubei is much larger than .1%.

I also think there are more reasons for expecting fewer severe cases in many parts of the world than in China, like the increased prevalence of smoking in China, relative to places like the US.

Comment by grothor on What will be the big-picture implications of the coronavirus, assuming it eventually infects >10% of the world? · 2020-03-01T18:20:20.149Z · LW · GW

I think the estimates in your links are not central estimates, even conditioning on 10% of the world being infected. The analysis in the Medium article basically assumes the worst case on every axis. So yeah, that will look pretty bad. And I think it is a good way to get a picture of what the right tail on this looks like. But it's pretty far from the most likely outcome. Mitigating factors that are ignored:

  • China got a lot better at managing the epidemic over time, and everyone can learn from that. (See the WHO report linked in the reddit post:

  • Related to the above, we're starting to get a sense of how it spreads, which should help us to slow the spread

  • Fatality rates so far may be much smaller than these worst case estimates, if the number of mild cases that were not detected is large. This is more likely to be true in Wuhan, where capacity for testing may have been stressed as well as capacity for treating. It is also more likely in the worlds where where ~50% of people become infected

  • Most published estimates of R0 are closer to the smaller end of the scale reported in that Medium article (2-2.5 from the WHO, 2-3 from JAMA, vs 1.4-3.8), and for comparison to influenza, 1.28 is on the smaller end of flu outbreak R0 estimates (~1.5 for the 2009 outbreak, and why did he use a point value with three significant figures for such an imprecisely measured thing?)

  • Any measure to slow down the virus will spread out the stress to hospitals. It's not as if we'll wake up one morning and half of all people in our town will be infected. We should be less concerned about how many people will be infected and more concerned about how many people will be infected at once.

  • Warmer weather usually makes these things less bad, which may slow the spread over the coming months

  • There is some evidence that east Asian populations are more susceptible (

If it looks like I'm reaching for arguments for not being worried, that's because I kind of am (though I do think everything I said here is true). But that's how the Medium article reads to me. It is very unlikely that all of the bad things will happen and none of the good things will happen.

Comment by grothor on AlphaStar: Impressive for RL progress, not for AGI progress · 2019-11-15T14:14:35.425Z · LW · GW

I'm not sure how surprised to be about middle of training, versus final RL policy. Are you saying that this sort of mistake should be learned quickly in RL?

Comment by grothor on AlphaStar: Impressive for RL progress, not for AGI progress · 2019-11-14T14:47:50.631Z · LW · GW

The replay for the match in that video is AlphaStarMid_042_TvT.SC2Replay, so it's from the middle of training.

Here is the relevant screen capture:

Comment by grothor on A Personal Rationality Wishlist · 2019-10-30T08:38:37.965Z · LW · GW

One thing that might be learned from bicycles is that their wonderfulness is partially contingent how you come to use them, and how much you seek out improvements in your relationship with them.

Most people ride with the saddle too low and their tire pressure too low (though recreational cyclists on road bikes will often have too much air in their tires). People tend to ride too close to the side of the road, and ride in too high of a gear (that is, they pedal too slowly). These are not universal. Many people get some or all of these things right or have good reasons for not doing them.

I'm not entirely sure why people get these things wrong so often, but it is at least partially because the wrong way feels intuitively correct, at least to begin with. And things like saddle height and gear ratio seem to have a lot to do with how the bike was configured when the person first started riding it. But all of these are things that can easily be learned from talking to experienced people, which most people never do.

So I think the lesson is: Seek out the correct ways of doing things, even in cases where you can just look at a thing and see basically how it works, so that it seems hard to get it wrong, and where it seems pretty wonderful even without help.

Comment by grothor on The unexpected difficulty of comparing AlphaStar to humans · 2019-10-01T11:31:17.435Z · LW · GW

Sorry I worded that really poorly.

It's all good; thanks for clarifying. I probably could have read more charitably. :)

That cognitive process of visual recogniton and anticipation is simply inseparable of the athleticism aspect.

Yeah, I get what you're saying. To me, the quick recognition and anticipation feels more like athleticism anyway. We're impressed with athletes that can react quickly and anticipate their opponent's moves, but I'm not sure we think of them as "smart" while they're doing this.

This is part of what I was trying to look at by measuring APM while in combat. But I think you're right that there is no sharp divide between "strategy" or being "smart" or "clever" and "speed" or being "fast" or "accurate".

Comment by grothor on The unexpected difficulty of comparing AlphaStar to humans · 2019-09-20T17:52:38.362Z · LW · GW

Being dumb and fast is simply more effective than smart and slow.

But it is unclear what the trade-off actually is here, and what it means to be "fast" or "smart". AI that is really dumb and really fast has been around for a while, but it hasn't been able to beat human experts in a full 1v1 match.

Much of the strategy in the game is build around the fact that players are playing with limited resources of athleticism (i.e. speed and accuracy) so it follows that you can't necessarily separate the two skill categories and only measure one of them.

The fact that strategy is developed under an athleticism constraint does not imply that we can't measure athleticism. What was unexpected (at least to me) is that, even with a full list of commands given by the players, it is hard to arrive at a reasonable value for just the speed component(s) of this constraint. It seems like this was expected, at least by some people. But most of the discussion that I saw about mechanical limitations seemed to suggest that we just need to turn the APM dial to the right number, add in some misclicking and reaction time, and call it a day. Most of the people involved in this discussion had greater expertise than I do in SCII or ML or both, so I took this pretty seriously. But it turns out you can't even get close to human-like interaction with the game without at least two or three parameters for speed alone.

Comment by grothor on The unexpected difficulty of comparing AlphaStar to humans · 2019-09-18T20:20:17.165Z · LW · GW

Thanks! I've updated the version on our site ( and I'm working on updating the post here on LW.

Comment by grothor on Which parts of the paper Eternity in Six Hours are iffy? · 2019-05-20T19:00:41.204Z · LW · GW

In the order that they appear in the paper, these are a few of the parts that seemed iffy to me. Some of them may be easily shown to be either definitely iffy, or definitely not-so-iffy, with a little more research:

As for nuclear fusion, the standard fusion reaction is 3H +2H→4He +n+ 17.59 MeV. In MeV, the masses of deuterium and tritium are 1876 and 2809, giving an η of 17.59/(1876 + 2809) = 0.00375. We will take this η to be the correct value,because though no fusion reactor is likely to be perfectly efficient, there is also the possibility of getting extra energy from the further fusion of helium and possibly heavier elements.

I'm not sure what existed at the time the paper was written, but there are now proposals for fusion rockets, and using the expected exhaust velocities from those might be better than using the theoretical value from DT fusion.

The overall efficiency of the solar captors is 1/3, by the time the solar energy is concentrated, transformed and beamed back to Mercury.

I feel like I'm the only one that thinks this Dyson sphere method is a little dubious. What system is going to be used to collect energy using the captors and send it to Mercury? How will it be received on Mercury? The total power collected toward the end is more than W. If whatever process is used to disassemble the planet is 90% efficient, the temperature required to radiate the waste heat over Mercury's surface area is about 7000K. This is hotter than the surface of the sun, and more than twice the boiling point of both iron and silica. In order to keep this temperature below the boiling point of silica, we would either need the process to be better than 99.98% efficient, to attach Mercury to a heat sink may times the size of Jupiter, or to limit power to about W. If melting the planet isn't our style, we need to limit power to about W.

I don't think this kills their overall picture. It "only" means the whole process takes a few orders of magnitude longer.

Of the energy available, 1/10 will be used to propel material into space(using mass-drivers for instance [37]), the rest going to breaking chemical bonds, reprocessing material, or just lost to inefficiency. Lifting a kilo of matter to escape velocity on Mercury requires about nine mega-joules, while chemical bonds have energy less that one mega-joule per mol. These numbers are comparable, considering that reprocessing the material will be more efficient than simply breaking all the bonds and discarding the energy.

The probes will need stored energy and reaction mass to get into the appropriate orbit, unless all the desired orbits intersect Mercury's orbit. Maybe this issue can be mitigated by gradually pushing Mercury into new orbits via reaction force from the probes. Or maybe it's just not much of a limitation. I'm not sure.

Because practical efficiency never reaches the theoretical limit, we’ll content ourselves with assuming that the launch system has an efficiency of at least 50%

This seems pretty optimistic. In particular, making a system that launches large objects at .5. Doing this over the distance from the sun to Earth requires an average force of about N per kg. For .9 and .99, it requires about 8 and about 35 this force/mass, respectively. I don't know what the limiting factor will be on these things, but this seems pretty high, and suggests that the launcher would need to be a huge structure, and possibly a bigger project than the Dyson swarm.

I also have some complaints about the notation, which I will post later, and possibly other things, but this is what I have for now.

Comment by grothor on What are questions? · 2019-01-09T19:03:26.330Z · LW · GW

Do animals ever 'ask questions'?

I've seen animals do things that seem like they are trying to resolve uncertainty (like a cat batting at some unfamiliar object with his paw), or make a request (a dog begging for food) which both seem similar to asking questions.

Comment by grothor on Reflections on Berkeley REACH · 2018-06-13T22:12:36.174Z · LW · GW

I slept on a couch while I was in town for EA Global. I'm glad that I did. My sleep quality wasn't great, mainly because I'm sensitive to light and sound and I forgot to bring an eye mask or earplugs. But I was reasonably well rested during the conference, nonetheless. Having Soylent available in the morning was nice, too, because I didn't have to spend time or mental energy finding something to eat before heading to SF for the conference.

But mostly, I liked the people. There were always friendly, interesting, and helpful people around, and everyone made me feel welcome from the beginning. We discussed things and played games, and I made some friends. When I needed to go to sleep in the main space while others wanted to keep talking, we quickly found a solution and nobody made me feel guilty.

A few minor complaints:

  • It's tough to coordinate things with six or seven people and one shower, especially when everyone is on the same schedule in the morning. I had been warned about this, and it's not clear to me what could be done, but it was a problem nonetheless.
  • When I reserved the couch, it wasn't clear to me what would be available, in terms of bedding, towels, etc. I just assumed I would be on my own, but it might be good to communicate this more explicitly.
  • There was some slight confusion about who was in what room and what was reserved. It might be good to have some simple way to designate this. Maybe a place to stick a name tag outside the doors to the rooms, or above the couches?

All in all it was great, and I hope I can come back soon!

Comment by grothor on Welcome to Less Wrong! (11th thread, January 2017) (Thread B) · 2017-03-29T04:12:17.962Z · LW · GW

I think one of my problems is that I don't actually think that much about what I read.

Do you mean that you don't put much thought into deciding what to read, or that when you read something you don't reflect on it?

Comment by grothor on Stupidity as a mental illness · 2017-02-12T16:06:35.459Z · LW · GW

They do, but there are also efforts to develop tests that measure other important aspects of cognition, which have an important bearing on things like how well you can function in society and how much of a risk you are to other people (these tests are, more or less, measuring what the rationality community might refer to as rationality). See, for example, What Intelligence Tests Miss: The Psychology of Rational Thought by Keith Stanovich.

Comment by grothor on Welcome to Less Wrong! (11th thread, January 2017) (Thread B) · 2017-02-09T02:18:07.324Z · LW · GW

(Also, the place to ask this sort of question might be the current Open Thread:

Comment by grothor on Welcome to Less Wrong! (11th thread, January 2017) (Thread B) · 2017-02-09T02:16:34.552Z · LW · GW

I do this too. I don't think that it is abnormal

Same here. I find that simulating other people's reaction to my arguments, mistakes, or work that I've done is helpful. When I want to find logical errors in my arguments, I imagine explaining them to someone with a strong background in philosophy. When something isn't working well in the lab, I imagine explaining the situation to someone with experience, and if I feel embarrassed or like they're about to offer a super obvious solution, it usually means I've made some silly mistake. Also, getting back to Sandi's question, some of the most helpful people for me to simulate are people that I met through the LessWrong meetup in Austin.

you could consider enrolling in graduate school

My classmates in grad school are often, but not always, a good source of more productive intellectual conversations. There is still sometimes an issue of differences in the style of thinking that people appreciate, or the kinds of topics they're interested in. And, of course, just because someone has had enough success in graduate school to stick around and be a friend for a few years doesn't mean they don't succumb to a variety of biases that can make it harder to have the kinds of conversations you're seeking.

Comment by grothor on Open thread, Feb. 06 - Feb. 12, 2017 · 2017-02-06T21:44:49.749Z · LW · GW

It's not an escape orbit, it's just a more eccentric orbit (unless it is much higher). Still, you are correct that my second solution will not work (see my second edit).

I started solving the trajectory for an exponentially decaying air density and a drag force that scales linearly with density and quadratically with velocity, but I did not immediately see the solution to the resulting differential equation, nor did I see a clever trick for avoiding the calculation. I'll look at it again later.

Comment by grothor on Open thread, Feb. 06 - Feb. 12, 2017 · 2017-02-06T21:07:57.354Z · LW · GW

Air density drops with increasing altitude. The object dropped from a higher altitude reaches a higher speed before reaching the denser air where object B is dropped. I'm not sure if a realistic density profile will allow object A to arrive first, but it is easy to show that there is some air density profile which will cause this to happen. I suspect that a necessary condition is that object A is already above the terminal velocity at object B's initial height when it reaches that height.

Or, if you interpret "free fall without any initial relative velocity against the planet" to say that it is stationary with respect to both the Earth's center of mass and the Earth's surface, then drop B from a geostationary orbit, and A from a higher position, where it will have insufficient angular velocity to be in orbit. It will fall to Earth, while B's orbit will decay.

Edit: It is permitted to assume that they are dropped over the equator, since the problem says "Central Atlantic".

Edit 2: Wait, I did this wrong. If object A has a rotational velocity of 1/day, and it is at an altitude higher than a geostationary orbit, it will be in some larger more eccentric orbit, so it won't fall to Earth any sooner than object B.

Comment by grothor on Stupid Questions December 2016 · 2017-02-06T18:24:46.212Z · LW · GW

I recently had a dream in which an unspecified organization was anticipating trouble from an unspecified group of people. One member of the organization remarked that, should things get bad, they had seven gay 400 lb game theorists that could be called in on a moment's notice.

What sort of problem is solved by the deployment of unusually heavy game theorists? Does it matter that they are gay? What kind of organization would have such resources at its disposal?

Comment by grothor on Open thread, Jan. 30 - Feb. 05, 2017 · 2017-02-04T17:22:48.538Z · LW · GW

It is completely unsurprising to me that there is an amount of energy use that makes one feel clearer and more productive compared to the sedentary graduate student, and that that can vary from person to person and over time in the same person as their physiological state adapts and changes.

I don't think that anybody here is surprised by this. What's surprising is not that there is an amount of exercise that is required for me to feel alert and productive, it's that the relationship between my mood and my exercise seems to follow a single, simple, specific rule. You explain the reasons why this should be surprising in your first paragraph. To illustrate why this seems surprisingly simple, here is a list of things that seem not to affect my productivity, holding total work constant:

-Heart rate


-Time of day

-Eating before or during the ride*

-How fatigued I am from the day before**

-Average Power

-Normalized power

-My functional threshold power at the time (a measure of fitness)

-"Training Stress Score"

The last three of these are metrics that are part of a physiological model. The model is somewhat simplistic, given the complexity of humans that you have mentioned, but the metrics have proven to be useful for athletic training (anyone who is interested in a more detailed description, which is still written for the layman, should check out Training and Racing with a Power Meter by Coggan and Allen). More to the point, there's no particular reason (that I can see) to expect total work to win out over any of the other things on this list.

But I do notice two things, having actually written down this list. First, each of these does seem to have a small non-zero effect. As I already mentioned, doing a little more than 1000kJ over a longer duration does seem to be okay, and my FTP does seem to shift my ideal amount of work a bit. Second, these are tightly coupled to each other. You can boil duration, average power, total work, normalized power, TSS, and FTP down to four variables, one of which is total work, and another of which will usually be 90% determined by total work. Furthermore, fatigue and how much I eat will have an effect on how much of a work I'm able or willing to do on a given day. This all means that it would be very easy to mistake a more complex relationship between some or all of these factors and my mood/cognition as a simple one, especially a simple rule that is bent slightly by external factors. I feel like this eliminates much of the confusion for me (the lesson here being that when I'm confused, I should stop, write down my confusion, and stare at it). However, it does not offer a strategy for venturing too far from the 900kJ rule without consequence.

Comment by grothor on Infinite Summations: A Rationality Litmus Test · 2017-02-02T19:57:58.061Z · LW · GW

When this sum hit the mainstream interwebz a while back, we had some discussion about it in the physics department where I work. The consensus was that it was misrepresented as a spooky non-intuitive fact about adding numbers, when really it's closer to a particular notation for assigning a finite value to a diverging sum that happens to be useful in physics*. Some of us were annoyed, because it feels like it's reinforcing this idea that math is impossibly opaque, a notion that we have to deal with on a regular basis when trying to teach physics to undergraduates.

Also, FWIW, I don't recall seeing this presented in my QFT class, but then again, I only took one semester.

*I think you're actually characterizing a it a little differently and a little more precisely, as a way of actually evaluating the sum, while subtracting off a term of order infinity, in a way that allows for certain kinds of manipulations that happen to be useful in physics.

Comment by grothor on Open thread, Jan. 30 - Feb. 05, 2017 · 2017-02-02T16:17:49.556Z · LW · GW

Could there be other substantial moderating differences between the days when you generate ~900 kJ and the days when you don't? (E.g., does your mental state before you ride affect how much energy you generate?

This could be the case, or there could be a common cause between the total work I do and my mood for the day. What makes me think this is less likely is that, when I'm following a training plan, the total work for the ride is largely determined days or weeks ahead of time. Then again, I will modify the day's workout on a training plan if I'm feeling shitty. Or it could just be that I noticed the pattern once when it happened by chance, then I expected it to continue, so it did (that is, it's more of a placebo than anything else). Then again, it wouldn't be hard for small effects like this to add up to the observed effect.

I actually did think about blinding it. I could modify some existing software to give me an intensity or duration that I don't know ahead of time, and that I don't have in front of me while I'm riding, and I could even not look at what it was until days or weeks later when I'm analyzing the results (or I could get even more hardcore and have someone else analyze it). The problem is that most of the motivation mechanisms I have for actually doing a worthwhile ride indoors require me to have access to a lot of this data. It would sort of be like trying to stay motivated in a game where you have no access to your score or whether you've eliminated another player.

Comment by grothor on How often do you check this forum? · 2017-02-01T23:20:20.574Z · LW · GW

I check once or twice most days.

  1. On average I'll maybe read two or three posts per day, comment once per week (though it comes in spurts), and vote once per day.
  2. Maybe 1/3-1/2 of link posts. Oftentimes, they're links to things I've already seen posted elsewhere (like Facebook)
  3. Browser on a desktop. Occasionally smartphone.
  4. SSC is the obvious answer. Also a few Facebook groups*, or people I follow on Facebook.

Much of the time, I'll just look at the recent comments to see what's getting activity. But when I look at the actual discussion posts, I usually find things worth clicking that I wouldn't have found by only looking at recent comments. I don't know why I do this. Maybe commenting about it here will make me stop.

Also, I feel like the LW meetup in Austin meets some of my need for the sorts of discussions that might otherwise be met by the website.

*Optimal Memes for Cosmopolitan Teens has become an unexpectedly useful place to hang out.

Comment by grothor on Open thread, Jan. 30 - Feb. 05, 2017 · 2017-02-01T21:03:20.860Z · LW · GW

I'm a cyclist and a PhD student, and I've noticed some patterns in the way that my exercise habits affect my productivity. I get a lot of data from every ride. While I'm riding, I measure heart rate and power, and if I'm outside, I also measure distance and speed. I've found that the total amount of energy that I produce, as measured by the power meter on my bike, is a useful metric for how I should expect to feel the rest of the day and the next day. In particular, if I generate between 800 kJ and 1000 kJ, I usually feel alert, but not worn out. If I do less, I feel like I've not had enough exercise, and I either feel restless or like my body is in lazy recovery mode. If I do more, I feel physically worn out enough that it's hard to work for an extended period of time, especially on the days that I am working in the lab.

What I think is most curious about this is that it is relatively independent of my fitness or the intensity of the ride. If I go balls-out the whole time, it takes slightly fewer kJ to make it hard to focus, and if I go super easy, it takes a bit more. It's the same with fitness. The difference between the power I can sustain for an hour when I'm in form for racing vs when I've barely been riding at all is about 25-30%, but the difference in the amount of mechanical work to make me unproductive is about 10%. (You might notice this gives me an incentive to stay in shape; I can do the same amount of work for the same productivity boost in less time when I'm more fit.)

So, what's definitely true is that the amount of work I put in on the bike is a useful metric for maximizing my productivity. What's unclear is if the amount of work is in some way fundamental to the mental state that it puts me in. The most obvious possibility is that it mainly has to do with the number of calories I burn; this is consistent with the finding that I need to do more work to feel tired when I'm more fit, since training will make you more efficient. But it's not obvious to me why this would be the case. When I'm in poor shape, an 800 kJ ride will have a much more drastic effect on my blood sugar than it will when I'm fit enough to race. It would be useful to venture outside the 800-1000 kJ range on days when I need to get work done.

I don't really know enough physiology to get any further than this. Does anybody else have experience with this sort of thing? Does anyone have empirically testable hypotheses? (Non-testable or not-testable-for-me hypotheses may be interesting as well.)

Comment by grothor on Feature Wish List for LessWrong · 2017-01-17T06:47:00.082Z · LW · GW

It would be helpful to have a few threads that are sticky, or otherwise easy to find. For example, the current open, welcome, and stupid questions threads. Today when I created that spurious welcome thread, I noticed a post made by a new user that seemed appropriate for the welcome thread and I wanted to link them to it. The link to the welcome thread at points to a 2015 edition. I tried a few different searches in the Google search bar, then checked a few of the tags that customarily go along with the welcome threads. Then I got anxious that I was double posting, and checked again. So I finally posted it, and within two hours, before I was even aware that I'd double posted, the thread got two new users posting on it, even though the original had sat idle for over a week.

This makes me think that I'm not the only one that had trouble finding it. The Google search that's integrated into the site is great for searching based on content and popularity, especially for older content, but it's slow to index, and sometimes the title of the link is misleading (it actually finds the original January 2017 Welcome thread, but the link shows up as January 2016). It looks like the way to have found it would have been ctrl-F on the discussion page. If the standard, regularly-reposted threads were sticky'd at the top, or had links on a sidebar or something, this wouldn't be an issue. A search that allows to filter by date would probably also suffice, so long as it indexes quickly enough.

I hope this doesn't sound like I'm making excuses; I made a mistake, and I feel appropriately embarrassed (and even as I type that, I get the mental image of Vaniver looking at me critically and saying "But do you?"). I realize that this may be mainly a case of me being bad at searching for things, and if I'm the only one who experiences this, then we can probably just not worry about it.