Waving at Saturn: The day the Earth smiled.

At 21:27 UTC on July 19, Smile and Wave at Saturn

At 21:27 UTC on July 19, Smile and Wave at Saturn

Bad Astronomy
The entire universe in blog form
July 17 2013 11:00 AM

Look Up, Smile, and Wave … at Saturn

2006 picture of Earth and Saturn from Cassini
From 2006, Earth peeks out from behind Saturn in a Cassini mosaic. Click to encronosenate.

Photo byNASA/JPL/Space Science Institute

Sometimes, when the abyss stares into you, you can stare back. And you can smile and wave.

Phil Plait Phil Plait

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death From the Skies!  

On Friday, July 19, between 21:27 and 21:42 UTC, the Cassini spacecraft will be taking pictures of Saturn, the magnificent ringed jewel of our solar system. Unlike most of the tens of thousands of images of Saturn taken, though, these will be special: From more than a billion kilometers away, Earth will be shining in them as well.


When this mosaic of images is completed, it will show Saturn and its rings, backlit by the Sun, with the Earth peeking over its edge. That final image will therefore in principle contain every human in existence. That means you. And me. And everyone you know, don’t know, love, are miffed at, are inspired by, in awe of, and who are taller, shorter, sicker, healthier, happier, sadder, slower, faster, the same, and different than you.

In short, human.

To celebrate this planetary family portrait, two events are planned.

One, The Day the Earth Smiled, is organized by Cassini Imaging Team Leader Carolyn Porco. You don’t have to smile: You can dance, tip your head, make a toast, or do whatever you think fit to acknowledge what we humans have done to explore our Universe. She’s also holding a pair of contests to encourage participation.


The first is to take a picture on July 19 of Earth, bearing in mind this question:

If you found yourself somehow communicating with an alien being from another world orbiting a star in a distant quadrant of the galaxy, and you could take only one picture of your home planet that best conveys to her/him/it the uniqueness of Earth among the planets orbiting the Sun, what would that picture look like?

For me, I would use this picture to show these aliens that we explore, we learn, and we concern ourselves about our home. But that’s me. (And, to be fair, I didn't take that picture.) What picture would you take? Think it through, go and take it, and submit it!

The other contest is to create a piece of music that, as Porco puts it, “ … must exalt the listener and capture the spirit and significance of The Day The Earth Smiled ... a day of cosmic self-awareness, celebrated planetwide, marked by an interplanetary salute between robot and maker.”


The rules for the contests are on Porco’s Diamond Sky Productions website. You can tweet about the event (or follow it on Twitter) with the hashtag #DayTheEarthSmiled. The wonderful group Astronomers Without Borders is supporting the effort as well, with lots of nifty ideas for you to participate in.

Saturn and its rings, by Cassini
Saturn, its rings, and their shadow on the planet's cloudtops. This was taken by Cassini on July 13, 2013. Tip o' the lens cap to Titan Saturn's Moon on Facebook.

Photo by NASA/JPL/Space Science Institute

The other event is being held by NASA’s Jet Propulsion Laboratory and is called Wave at Saturn. This one is simple: At the time the Cassini pictures are taken, go outside and wave at Saturn. You can take a picture of yourself at that moment and upload it to their Flickr group. They’ve set up a Facebook page, and you can tweet your efforts with the hashtag #waveatsaturn.

Remember, the pictures will start being taken at 21:27 UTC on July 19—that time has been calculated to include the time it takes light to get from Earth to Saturn. So if you go out then, for the next 15 minutes the light from Earth will be on its way to Saturn, to be captured by Cassini’s cameras.

At the appointed time, I will be in San Diego at Comic Con. But I think I can spare a few minutes to go outside, soak up the afternoon Sun for a moment, and then turn to the east a bit. I’ve seen it countless times through images, through data, through my telescope, and through my own eyes, and let me say: There’s always a smile on my face ready for Saturn.