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> researchers discovered what is known as an inverse square relation between the number of people in a given urban location and the distance they traveled to ge

> researchers discovered what is known as an inverse square relation between the number of people in a given urban location and the distance they traveled to get there I'm highly skeptical of this result as my lived experience is that travel time is so much more important than distance. There are two parts of my city that I like to visit that are roughly equidistant from my home. One can takes 20 minutes to arrive at, the other 45. Can you guess which one I visit more often?

tommymachine 5y ago
From the abstract: > we reveal a simple and robust scaling law that captures the temporal and spatial spectrum of population movement They throw around the word "temporal", but it's not clear exactly how they incorporate the time element without taking the plunge on the full study.
- pfortuny 5y ago
  In the frequency of visitation, so that sentence seems to be a bit confusing.
Anon84 5y ago
This is known as a "Gravity Model" in the transportation literature and it's very far form being a new discovery. It's been around since the 1930s under various guises (https://en.wikipedia.org/wiki/Gravity_model_of_trade https://en.wikipedia.org/wiki/Gravity_model_of_trade) We used the same concept in our 2009 paper (https://www.pnas.org/content/106/51/21484 https://www.pnas.org/content/106/51/21484) but the exact functional form of the distance dependency (1/r, 1/r^2, 1/e^r, etc) varies with their exact definition of city due to the Modifiable Areal Unit problem (https://en.wikipedia.org/wiki/Modifiable_areal_unit_problem https://en.wikipedia.org/wiki/Modifiable_areal_unit_problem). In our specific case (cities defined as Voronoi cells centered around airports) the dependency was exponential.
- soVeryTired 5y ago
  Presumably that just shows that it's easy to fit things with inverse-power functions, rather than revealing some fundamental truth about the behaviour the equation is modelling.
  - deleted 5y ago
    [deleted]
shatnersbassoon 5y ago
I think that both this and what the paper says can hold true. The paper is saying that from the point of view of the location, the distribution of effective distances traveled is invariant. So if you really like the 45min part of your city, then every one closer really loves it, so visit it much more than you do. Therefore the law holds true, even though on an individual basis you obviously go to the closer parts more frequently. The fact that you might be prepared to go all the way to e.g. Disneyworld means that the people who live closer are massively more likely to go there to the point where people who live 5 miles from it go there all the time.
yummypaint 5y ago
Averaged out over all inhabitants of the city and all areas of the city it wouldn't be surprising if it still held. What is accessible from your dwelling may be less accessible to someone else the same distance away but approaching from a different direction.

tommymachine 5y ago

From the abstract: > we reveal a simple and robust scaling law that captures the temporal and spatial spectrum of population movement They throw around the word "temporal", but it's not clear exactly how they incorporate the time element without taking the plunge on the full study.

pfortuny 5y ago
In the frequency of visitation, so that sentence seems to be a bit confusing.

Anon84 5y ago

This is known as a "Gravity Model" in the transportation literature and it's very far form being a new discovery. It's been around since the 1930s under various guises (https://en.wikipedia.org/wiki/Gravity_model_of_trade https://en.wikipedia.org/wiki/Gravity_model_of_trade) We used the same concept in our 2009 paper (https://www.pnas.org/content/106/51/21484 https://www.pnas.org/content/106/51/21484) but the exact functional form of the distance dependency (1/r, 1/r^2, 1/e^r, etc) varies with their exact definition of city due to the Modifiable Areal Unit problem (https://en.wikipedia.org/wiki/Modifiable_areal_unit_problem https://en.wikipedia.org/wiki/Modifiable_areal_unit_problem). In our specific case (cities defined as Voronoi cells centered around airports) the dependency was exponential.

soVeryTired 5y ago
Presumably that just shows that it's easy to fit things with inverse-power functions, rather than revealing some fundamental truth about the behaviour the equation is modelling.
- deleted 5y ago
  [deleted]

shatnersbassoon 5y ago

I think that both this and what the paper says can hold true. The paper is saying that from the point of view of the location, the distribution of effective distances traveled is invariant. So if you really like the 45min part of your city, then every one closer really loves it, so visit it much more than you do. Therefore the law holds true, even though on an individual basis you obviously go to the closer parts more frequently. The fact that you might be prepared to go all the way to e.g. Disneyworld means that the people who live closer are massively more likely to go there to the point where people who live 5 miles from it go there all the time.

yummypaint 5y ago

Averaged out over all inhabitants of the city and all areas of the city it wouldn't be surprising if it still held. What is accessible from your dwelling may be less accessible to someone else the same distance away but approaching from a different direction.