Once again, someone has proposed that an ad supported company offer subscriptions for exactly its revenue-per-user, without seeming to realize that not all users are equally valuable to advertise to, and only the most valuable ones will opt out.
Love this. I took a few minutes and converted your image into an Illustrator/vector file. Not 100% true to your original, but pretty good. Infinitely scalable so people can print it if they want.
The trouble with making a higher res image is that when you make that lat/lon buckets smaller, you have fewer samples in each one, so the image gets noisier. For the best possible image you'd want to download all the years of data.
The process of making it was quite simple. I zeroed a 2d array of integers, then took all the pickup/dropoff points and incremented the nearest cell. The pixel values are based on the logarithm of the counts, since otherwise everything outside midtown would be pretty much black.
There are some artifacts, like the thin vertical line down the east river. I think that was because of how the data was rounded, i.e. the number of unique longitude values that map to a certain image column.
I wrote this myself with a few hundred lines of C++, though I'm sure there's GIS software out there that will do all this for you with a few clicks.
Can you explain why there is a line going to the airport? Shouldn't the airport be more of an island of light (since I imagine most people aren't getting picked up / dropped off a half mile from the airport)?
Also did you overlay it onto a map? How did you get the angled effect if it's just a grid?
> Can you explain why there is a line going to the airport?
I assume it is because there is a fixed fare to/from JFK so drivers have little incentive to start/stop the meter at the exact pickup/dropoff location.
> Also did you overlay it onto a map?
No. If taxis did not pick up or drop off people on some street, that street does not appear. For example there is an area downtown where there are streets but they have had security barriers since 9/11 thus no taxis.
> How did you get the angled effect if it's just a grid?
None of NYCs grids are exactly north/south/east/west aligned.
If you are interested in what the 2013 data looks like at full resolution, I have a web map of it (https://www.mapbox.com/blog/vector-density/). Haven't updated with the new data yet.
You don't even need dedicated mapping programs. It's just latitudes and longitudes, so any 2D plotting program would be sufficient (as long as the data can fit into memory!).
Although the country boundaries aren't strictly necessary. Since there appears to be a demand for generating these maps, I'll work on a tutorial for this NYC data set.
Apparently no one who knows what they'd be talking about has seen this, so I'll have to take a pass.
A ramjet is basically a tube open at both ends and moving very quickly so that air enters one end and leaves out the other. Because of the speed of the air moving through it and the shape of the tube, the air is compressed in the tube and something sprays fuel into the compressed air, which ignites and produces higher-velocity air moving out the end of the tube. It's a jet engine, although normal jets have to have elaborate turbine-compressor thingys to do the air compression.
The ionizing radiation thing is a goofy UFOs-are-space-travellers thing, where the UFO sprays ionizing radiation in front of itself, which heats and disperses the air in front of it, allowing the UFO to travel faster. Or something. It's goofy.
But still not perfectly safe. I'm not sure how much power a F-16 puts out but when I was working on space surveilance radars we were very careful not to be pointing our beam where people might be.
A roommate's girlfriend worked on PAVE PAWS. They were very careful where they steered the beam. Rumor was the one on the east coast cooked some fish when they pointed it into the ocean.
And of course the microwave oven was conceived when a guy walked in front of an operating radar and it melted the chocolate bar in his pocket. It gave him a genius idea!
The best part about this story is that if you tell people who don't know about it, they'll think you're full of shit. But it's absolutely true.
A much more important example of this than "martian potatoes" is uranium enrichment.
Natural uranium is ~1% U235; bombs need 90+% U235. So when you've enriched it from 1% to 2% it doesn't seem like you've made a lot of progress towards 90.
If instead of enriching U235 you think of it as eliminating U238, though, then you've done half of the work.
If you start with 10000 kg of natural (0.7%) uranium and you want to separate it into 45 kg of highly-enriched (90% U235) uranium and 9955 kg of depleted (0.3% U235) uranium, then you will have to do 8800 kg of "Separative work units".
On the other hand, separating that same fuel into 3000 kg of partially-enriched (1.4% U235) uranium and 7000 kg of partially-depleted (0.4% U235) uranium only takes 1790 kg of "Separative work units", even though the increased concentration of U235 means that "half the U238 has been eliminated".
Isotope enrichment is an area where, to borrow a line from software engineering, the first 90% takes 90% of the time, and the last 10% takes the other 90% of the time.
Actually I meant 45 kg and 9955 kg. I adjusted the numbers several times looking for values which would come out with round-ish quantities but %U235 values in the right ranges for HEU and DU.
Annnnd just spent an hour reading that delightful Colin Percival Putnam thread. Thanks for the reminder on that. Man, people really loved to hate on Tarsnap because of his perceived arrogance.
On the contrary, Colin is highly regarded on HN both for his technical ability, and his success in business (despite breaking from conventional wisdom in how to be successful in business).
Thanks for pointing this out. I've vaguely heard before that some nations (like North Korea) have difficulty building nuclear bombs because it's hard to enrich Uranium. This really quantifies that difficulty for me.
as much as our brains are designed to understand logarithmic scales, this percentage problem never really feels intuitive for me. If you have 1 part U235 and 99 parts U238, to get to 2%, it is 50.5% (50/99) of the work to get to to 100% enriched. If all you need to get to weapon grade uranium is 90% enriched, you need to eliminate 98.88888 of the 99 units of U238 (1/1.11111 = .90). So there is no real significant difference in your progress, you are now 50.56% of the way there.
> they want to filter out people who don't take OpSec rules seriously
I personally think it's a little bit this.
I know someone who applied to be an intelligence analyst agent in the UK. First stage was a multiple choice exam in a London hotel, where they had to turn up and say they were there for "KRNP Recruiting" or something. Now the hotel staff must have known something was going on, and it wouldn't be to hard to find this out ... but I reckon it filtered out both ppl who didn't take it seriously and also people who enjoyed that kind of subterfuge a little to much :-)
That was my understanding, they know it is possible for a foreign government to tap the phone lines and they don't want a foreign government being able to target candidates for hire.
They pump in freshwater to the cooling circuit of the reactor, like from the tap. The water that comes back out of the discharge has gained temperature but has no tritium. They probably just return this water to the sewer system for now.
Just the water from the leaks has be retained at present.
If they mixed the water from the tanks, they'd have to retain 100% of the flow of the water.
Now if they built a big cooling pond and stuff they could reuse the water 'forever'. But the last thing you want is a big pond of slightly radioactive water than all kinds of wildlife can come live in.
You cannot compare averages because the users who choose to pay to kill ads will not be randomly selected. No, there will be massive adverse selection -- the users with lots of disposable income are the ones that make advertising lucrative, and will be exactly the ones who pay to opt out of it. The averages massively understate what they would have to charge.
I bet they required the guy who delivered the rocket fuel to sign something saying it contained no impurities, the guy who delivered the external tank to sign something saying it did not leak, etc... why should the software guy be special?
Yeah I know. We're special. But the world doesn't always see it that way.
No. That it contained under n ppm of impurities, that it did not leak more than 0.001%/year, maybe. Only a Sith (and consumer product marketing that is lying to you) deals in absolutes.
In the durable goods world, you don't pretend things are perfect. Failure modes are designed and disclosed, replacement of parts is expected and made reasonable, tolerances are marked, failure rate metrics like MTBF are known, and as a customer you choose the price-quality tradeoff that makes sense for you.
I just wish consumer products were also sold this way. Instead we pretend every product is awesome and act surprised when things break.
That reminded me of phone plans, oddly enough. For a while, everybody was advertising their data plans as unlimited, and then the tech press would get all upset when they found the limit.
I always thought the whole thing was dumb - of course there's a limit. Or are we supposed to believe we can push megabytes/s nonstop all month? I'd rather have them just tell me what the limit is and what happens when you go over it than pretend it's unlimited. And stop having the tech press act like the sky is falling when they discover that the unlimited plan actually has a limit.
At least some consumer goods have similar limits, e.g. maximum amount of arsenic permitted in apple juice. Of course, whenever people find out about these limits, they lose their shit... "Why is any arsenic ok? OMG! The evil government is trying to poison us!"
The person in charge of a mass spectrometer (Thermo Element 2) at a local college likes to toy with his students by running tests on their commercial bottled water during a lab demonstration. This particular instrument can pick up minute traces of uranium, lead, and the like (on the order of fg/L IIRC).
At the end of the demonstration, the trash can is full of discarded water bottles.
My first thought from "properly dispose of, we don't want it in landfills" was, this is for hazardous waste -- you know, that box of old paint cans and dead SLA batteries that you know your city has a plan for, if only you could be bothered to figure it out. If not, maybe the website should make that more clear.
