Everything is spinning or circling, or both. The moon goes round the Earth, the Earth goes round the sun, the sun goes round the galaxy, the galaxy goes round the universe.
These orbits are what hold things together, and it’s good to think about the dynamism of the cosmos once in a while. It puts things in perspective.
When David Sneider’s friend mentioned casually a couple years ago that she feared some bad luck because Mercury was in retrograde, Sneider winced a little.
“I thought this was kind of surprising that she was thinking about the movement of celestial bodies, but the way she was expressing it was full of confusion,” he said. So he wondered: “Is there a way to think about this with less superstition and a twinge of cosmic awe?”
Sneider, a tech worker in San Francisco, made some calculations. And then he figured it out.
“There is a lot of cosmography that humans can intuit,” he said. “We have a great sense of day and night, a great sense of year.” We celebrate New Year’s Day and the solstice. “But there are scales above (this) that we can’t intuitively understand.”
Like our solar system in relation to the rest of the galaxy. Like the position of our particular sun, one of hundreds of billions of suns in the Milky Way. Like the fact that our sun moves.
So Sneider decided to invent a new holiday: Galactic Tick Day. And get ready, because the 236th Galactic Tick Day is June 26.
“The delight of this whole thing is that somebody (now) has a cognitive frame, or sees through a lens, that’s bigger than they’ve ever used before,” Sneider said.
A galactic tick
Admittedly, it’s a bit arbitrary. After all, the Earth is in constant motion. There is no known starting point, so Sneider and three of his pals out west had to pick one. Here’s how they set this up:
Their clock started ticking (so to speak) on Oct. 2, 1608, the date Hans Lippershey filed the first patent for the telescope. The first Galactic Tick Day, therefore, was 1.7361 years after that.
That unit of time is equivalent to 633.7 days, which is 1/100 of an arcsecond. What’s an arcsecond, you ask? Good question! An arcsecond is a unit of time and angle that measures degrees of an circle. “Just as an hour is divided into 60 minutes and a minute into 60 seconds, a degree is divided into 60 arcminutes and an arcminute is divided into 60 arcseconds,” according to the website http://coolcosmos.ipac.caltech.edu.
Earth (along with the rest of our solar system) orbits the center of the Milky Way galaxy every 225 million Earth years (that's called a galactic year). One centi-arcsecond of this jaunt is a gallactic tick.
“People aren’t aware we’re on a moving train,” noted Jon Hakkila, a physics and astonomy professor at the College of Charleston. “On Earth, you think everything’s stationary. You’re unaware that we’re moving really fast — the Earth orbiting sun, and the sun itself is moving.”
OK, ready to have your mind blown?
“When the dinosaurs died off, that was a little more than a quarter of a galactic year ago,” Hakkila said. “The sun has orbited a little more than a quarter of the way around the galaxy since the dinosaurs died. In about 4.3 billion years — roughly the age of the sun — in that time we’ve completed around 19 orbits around the galaxy. So this is a really slow clock.”
As they say in sailboat racing, slow is fast. The clock might be “slow” according to human perception, but the sheer scale of the galaxy means the Earth is hurtling through space at enormous speeds: 67,000 mph around the sun. The solar system as a whole is moving through space at more than 500,000 mph.
“The motion of the stars keeps everything from falling in toward the center,” just as the moon’s orbit keeps it from falling into the Earth, and the Earth’s orbit keeps it a safe distance from the sun, Hakkila said.
Apparently, we are moving at just the right speed.
“If we orbited faster, we’d escape the pull of the sun,” he said. Next thing we’d know we’d be waving at Pluto in the rearview mirror. “This orbital motion keeps everything kind of relatively stationary. You can think of it as a bound system.”
Sneider said he sees this as a long-term project, and there is no plan to commercialize it. “Mother’s Day took 20 years to get any kind of foothold,” he noted.
Galactic Tick Day is meant to help start, or at least fuel, a conversation about the significance (or insignificance) of the human experience.
“It’s an interesting cultural leverage point, maybe shifting away from nation state-based thinking and accepting the idea of biosphere,” he said, expressing a desire for unity and solidarity and a collective celebration of science.
Hakkila betrayed a certain enthusiasm for the quirky project.
“In a way he’s really right,” he said of Sneider’s conceit. “I’m glad he did this. This is the stuff people like learning about. It’s a way to make it more real to people.”