Every recorded meteorite strike on Earth since 2,300 BCE mapped
osm2.cartodb.comThis map is a great example of how Google Mercator is not always the right projection for a visualization. Antarctica is an important source for meteorite research; black specs are easy to pick off the white ice. But this map projection completely distorts Antarctica so you can't really read that part of the data. Cool map, but sometimes the off-the-shelf map tool isn't the right choice.
It's not google. This one is based on http://cartodb.com/, however the argument is still valid
This reply from Google explains why they use Mercator. http://productforums.google.com/d/msg/maps/A2ygEJ5eG-o/KbZr_... Not sure if it's really satisfactory, but at least there's a reason.
The projection (how the globe is represented in 2D) is still Google's. Technically it's Web Mercator / EPSG:900913, where 900913 is a rather clever choice by Google.
> not always
I think "almost never" would be more accurate here.
Mercator is only used because it's the projection you get when you don't apply any projection to longitude/latitude. It's a result of the map creator being lazy.
It depends on the scale. For a world map, Mercator is, as you suggest, almost never a good choice. For many other situations where it's important to show the correct angular relationship between objects (such as streets), Mercator is the most faithful. And I can understand why there might be issues with using different projections at different scales.
I could equally well say it's lazy to use just use Google Maps or some other convenient mapping service that uses Mercator projections at the world level when those services are not really optimized for displaying at that scale.
If you had a street that crossed the North Pole you wouldn't want a Mercator Projection. It would look thoroughly deformed.
Many orthogonal, North-aligned projections will look fairly similar same when zoomed into a street at least a couple degrees latitude away from the poles. Ideally, you would always use a 3D projection of that section of the sphere (e.g. Google Earth not Google Maps) or a local two-point equidistant projection since these are always the most accurate. An orthogonal projection only suffices in common usage because there is so little need for maps near the poles.
In any case, I should have qualified my original comment with: "for a whole-earth map or a map showing distributions". Mercator is always a bad projection for a map showing distributions because it seriously misrepresents area, undermining the effort to accurate portray distribution.
I think you're mistaken; the projection you get when you naively plot lat/lon as x/y is Plate Carrée (aka equirectangular). This visualization is Google Mercator.
You see a lot of Google Mercator because it's the native projection of Google Maps and pretty much all subsequent slippy map libraries and tilesets. It's a great projection when you want something that works easily with map tiles and is zoomable. But it's not a great choice for a whole-earth visualization.
Nice.
Some kind of explanation would be helpful, though. Apparently the size of the circle is related to the mass of the meteorite, and color is density of circles. But it took me a while to figure that out.
Also, what happened in Oman?
EDIT: Wikipedia says, "The central desert of Oman is an important source of meteorites for scientific analysis." Possibly meteorites are just easier to find there, due to properties of the terrain. Perhaps meteorite hunting is a popular sport/business, too?
Apparently Oman is a destination for meteorite explorers. That explains the difference between Oman and Saudi Arabia on the map. http://www.livescience.com/3613-searching-meteorites-deserts...
More accurately described as "where people were located since 2,300 BCE that were capable of recording meteor strikes and recorded them in a form that survived until present day and made its way into a database of meteor strikes." Latitudinal variations in the density of meteor strikes wouldn't surprise me; longitudinal ones should be entirely explained by the observational effect. Hence we see a ton of meteor strikes in the continental US and virtually none in rural China, though both are on similar latitudes.
What's the data source? If it's the US meteorical society database, then it probably includes "finds" in additional to witnessed "falls".
Interesting. The relatively high number in India compared to surrounding locations says to me that there is a strong component of culture (determines if things are recorded) and population density. On the other hand, flyover country in the US seems to get more than the coasts, despite population density, so perhaps light pollution on the coasts is skewing the results?
sorry, but this is another population density map
Not really.
Note the large number of strikes in the Sahara desert (and Antarctica, as someone else noted).
There are at least two things going on here, probably more:
1) Population density 2) Ease of finding the meteorite or crater (this is easier in barren areas with relatively homogeneous terrain, like the desert and Antartica).
Yup... I don't think anyone is going to argue that Australia in fact has a higher population density than China.
In fact, the effects of 2) are reinforced even more, since my guess is that many, if not the majority of these findings were by scientific studies/surveys (note that they typically list the date found, not the date it occured). And since no one likes wasting their time, they would obviously pick areas where it would be easiest to find evidence.
You right, but I still see this map as a catalogue of found meteors, rather than an informative visualisation. To make your observations clear, you need to normalise this heatmap by the population density.
It depends on what you're after. What you're suggesting would would also distort the data, but in a different way -- it'd make it look like Antarctica was far more likely to get hit than it actually is.
One would expect the true distribution to be extremely uniform, right?
Overall, yes. I wonder, though, could the spin of the Earth have any effect on the distribution?
Improbable.
However, there could be a favoured plane of arrival, like the solar system plane, and with a circular cross section of the Earth I'd expect less debris/area near the poles. (I don't know this, I'm just extrapolating from what I actually know.)
> ... with a circular cross section of the Earth I'd expect less debris/area near the poles.
As it turns out, Antarctica is a very productive place to look for meteorites, first because there isn't really a preferred geographical zone for meteorite impacts, and second because of the large, empty ice fields, against which newly fallen meteorites stand out.
One of the most famous meteorite finds of all time, ALH84001, was located by simply driving across the Antarctica landscape and watching for dark objects.
Totally on 2. Checkout Oman, there a lot there, why? http://www.emirates247.com/news/oman-is-major-site-for-meteo...
Bingo. In order to report meteorite strikes, there must be 1) people to report them and 2) some institution to track them. If anything, it looks pretty evenly distributed after adjusting for 1 and 2.
Well, not all meteorite strikes could have been reported 4,300+ years ago! This is probably a map of where people have been looking for them. Less developed places, such as in middle America, (which stands out like a sore thumb) might make for good locations to look for such things!
I suspect it would be extremely challenging to observe a meteor from a rain forest, and practically infeasible to find it after. Unless we'll rely on satellite observations
I highly doubt we're able to locate or date meteorites (which are really, really small, especially after they've passed through the atmosphere) with satellites. I suspect we haven't found meteorites in rainforests because we haven't been looking due to the difficulty.
The recorded meteor strikes tend to cluster about human populations. Inescapable conclusion: Aliens!
;)
Apology accepted.
Are the patterns I see here artifacts of the data collection method, or do meteors really prefer the northern hemisphere?
Almost exclusively due to the data collection method. Specifically, only recorded strikes are shown -- someone had to find the meteorite and publish its existence. Hence the dense jungles of Congo are relatively empty compared to the well trodden plains of Kenya.
Also notice: the only plotted strikes in Antarctica are right near the scientific stations -- but the intensity is very high at those points.
If you plotted theoretical meteorite distributions, there would be more strikes at the poles than the equator (due to the Earth's rotation, the poles receive many more meteorites) but at a given latitude the distribution would be even.
Also notice: the only plotted strikes in Antarctica are right near the scientific stations -- but the intensity is very high at those points.
If you plotted theoretical meteorite distributions, there would be more strikes at the poles than the equator (due to the Earth's rotation, the poles receive many more meteorites) but at a given latitude the distribution would be even.
Could someone who understands this really well explain why the rotation of earth would change the number of meteorite strikes near the equator?
(It seems to me that strikes should be completely randomly distributed across the earth's surface and if a meteorite was headed for one area of the equator and the earth was spinning, the meteorite would simply hit another area of the equator.) I'm probably missing something here, but I can't figure out what.
I wonder what data source was used. I've confirmed a few strikes several miles from where they actually hit. (A Kendall County, TX strike appeared south of San Antonio, and a Louisville, KY strike appeared downtown while the actual strike occurred several miles from downtown.
The table gives a source for every data item. They all look to be from here: http://www.lpi.usra.edu/meteor/metbull.php
Some of these comments raised a lot of questions about meteor distribution due to orbital/rotational effects.
Found some answers here: http://curious.astro.cornell.edu/question.php?number=746
Logically oceans get hit at the same rate. Also land that is now under water. Are there any recorded oceanic meteor strikes in this map?
Oh! The one that killed the dinosaurs. It was pretty big. Maybe only the big ones leave a mark on the ocean floor.
Some explanation over the map is here http://www.theverge.com/2013/2/18/4001936/map-every-recorded...
They seem to concentrate in areas with the means to record them
it would be interesting to overlay geography and population maps on top of this data. It seems as if the most density comes in areas with flat, unobstructed land, but also with relatively high populations. Assuming random strikes, mere desserts or population centers do not seem enough to generate density, it must be a combination of prairie/desert and people such as Kansas or Northern Texas
If you are interested on how it was made, checkout https://vimeo.com/59791629
Interesting - there is a perception, I think, that Russia gets hit by more than their share, but actually opposite seems true