Radio Free Earth

Back at the first San Francisco Science Hack Day I wanted to do some kind of mashup involving the speed of light and the distance of stars:

I wanted to build a visualisation based on Matt’s brilliant light cone idea, but I found it far too daunting to try to find data in a usable format and come up with a way of drawing a customisable geocentric starmap of our corner of the galaxy. So I put that idea on the back burner…

At this year’s San Francisco Science Hack Day, I came back to that idea. I wanted some kind of mashup that demonstrated the connection between the time that light has travelled from distant stars, and the events that would have been happening on this planet at that moment. So, for example, a star would be labelled with “the battle of Hastings” or “the sack of Rome” or “Columbus’s voyage to America”. To do that, I’d need two datasets; the distance of stars, and the dates of historical events (leaving aside any Gregorian/Julian fuzziness).

For wont of a better hack, Chloe agreed to help me out. We set to work finding a good dataset of stellar objects. It turned out that a lot of the best datasets from NASA were either about our local solar neighbourhood, or else really distant galaxies and stars that are emitting prehistoric light.

The best dataset we could find was the Near Star Catalogue from Uranometria but the most distant star in that collection was only 70 or 80 light years away. That meant that we could only mash it up with historical events from the twentieth century. We figured we could maybe choose important scientific dates from the past 70 or 80 years, but to be honest, we really weren’t feeling it.

We had reached this impasse when it was time for the Science Hack Day planetarium show. It was terrific: we were treated to a panoramic tour of space, beginning with low Earth orbit and expanding all the way out to the cosmic microwave background radiation. At one point, the presenter outlined the reach of Earth’s radiosphere. That’s the distance that ionosphere-penetrating radio and television signals from Earth, travelling at the speed of light, have reached. “It extends about 70 light years out”, said the presenter.

This was perfect! That was exactly the dataset of stars that we had. It was a time for a pivot. Instead of the lofty goal of mapping historical events to the night sky, what if we tried to do something more trivial and fun? We could demonstrate how far classic television shows have travelled. Has Star Trek reached Altair? Is Sirius receiving I Love Lucy yet?

No, not TV shows …music! Now we were onto something. We would show how far the songs of planet Earth had travelled through space and which stars were currently receiving which hits.

Chloe remembered there being an API from Billboard, who have collected data on chart-topping songs since the 1940s. But that API appears to be gone, and the Echonest API doesn’t have chart dates. So instead, Chloe set to work screen-scraping Wikipedia for number one hits of the 40s, 50s, 60s, 70s …you get the picture. It was a lot of finding and replacing, but in the end we had a JSON file with every number one for the past 70 years.

Meanwhile, I was putting together the logic. Our list of stars had the distances in parsecs. So I needed to convert the date of a number one hit song into the number of parsecs that song had travelled, and then find the last star that it has passed.

We were tempted—for developer convenience—to just write all the logic in JavaScript, especially as our data was in JSON. But even though it was just a hack, I couldn’t bring myself to write something that relied on JavaScript to render the content. So I wrote some really crappy PHP instead.

By the end of the first day, the functionality was in place: you could enter a date, and find out what was number one on that date, and which star is just now receiving that song.

After the sleepover (more like a wakeover) in the aquarium, we started to style the interface. I say “we” …Chloe wrote the CSS while I made unhelpful remarks.

For the icing on the cake, Chloe used her previous experience with the Rdio API to add playback of short snippets of each song (when it’s available).

Here’s the (more or less) finished hack:

Radio Free Earth.

Basically, it’s a simple mashup of music and space …which is why I spent the whole time thinking “What would Matt do?”

Just keep hitting that button to hear a hit from planet Earth and see which lucky star is currently receiving the signal.*

Science!

*I know, I know: the inverse-square law means it’s practically impossible that the signal would be in any state to be received, but hey, it’s a hack.

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