What if New Horizons flew by Earth instead of Pluto? Could it see my house?

Short answer: Only if you were a billionaire.

Longer answer: I know I talked about New Horizons and Pluto yesterday, but there’s too much awesome to be had for just one post about it.

New Horizons’ closest approach to Pluto was about 12,600 km (about 7,800 miles), and believe it or not you could actually travel this distance. If you want to figure out how far it would be from your home town go get a globe and measure a piece of string (or floss, whatever works) from the west coast of Ecuador to the north shore of Lake Victoria in Africa, near Kampala. They should be easy to find, both are right on the equator. That string is now a ruler – pin one end on your current location and see how far it reaches. If you don’t want to do this experiment, then for reference, this distance is comparable to the length of the Great Wall of China, or it’s about how far you would fly if you traveled from Los Angeles to Benin City, Cameroon (also in Africa) if you had a connecting flight in Newark, NJ.


Anyway, New Horizons came really close to Pluto, close enough to take some great pictures. It’s highest resolution camera on board was the Long Range Reconnaissance Imager (LORRI), which has a resolution of about 1 arcsecond (or 5 microradians). At closest approach, we can turn this into a minimum distance resolvable by using the small angle approximation:

     sin(θ) ~ θ ~ (size of smallest thing resolved) / (distance)

which tells me that the smallest resolvable feature, at a distance of 7,800 miles from earth Earth or Pluto, would be about 60 meters long. That’s about half of a football field, and a little bit bigger than the average house. This could get a good look at the average big building, but your house probably wouldn’t be resolvable unless you were a billionaire with a big ass mansion.

So what could you see on earth if you had this resolution? Well, I did my best on Google maps to reproduce a view of what New York might look


New York City (Google Maps)


I based it on the scale in the bottom corner – it’s about 120 pixels long and it says 5 miles, so it’s very nearly 60 meters/pixel. If you want to reproduce this scale over your hometown on Google maps, just zoom in all the way, and then zoom out until the scale jumps from 2 miles to 5 miles.

Unfortunately, New Horizons was only close enough to get this kind of detail for a few hours, which is not long enough to scan the entire planet. The highest resolution images of the entire planet we should expect are about 1 kilometer/pixel, which would have this sort of resolution:



East Coast (Google maps)

and a lot of neat features jump out. Those wavey lines in the top left are the Appalachian Mountains, and that grey fungus is cities. I can pick out (starting from the bottom of the Chesapeake Bay) Virginia Beach, Richmond, DC and Baltimore, Philadelphia, and New York City.

So, what does Pluto look like at a resolution of about 5 km/pixel?


pluto kmperpixel

Pluto (NASA)


What a time to be alive.




asked by /u/Tiduszk
cover image credit: NASA




Have a question? Send it to matt@quarksandcoffee.com