To keep track of time, humans have relied on Earth’s rotation around the sun as a measurement of time, often celebrating the journey with the New Year’s holiday. Like most celestial objects in space, the Sun (and the solar system with it) also completes its own rotation around the center of the galaxy – home to a supermassive black hole.
The supermassive black hole exerts a tremendous amount of gravity on objects closer to the center of the galaxy, but the Sun maintains a very safe distance away from it.
So why doesn’t the sun get pulled toward the centre of the black hole?
Because it travels at a speed of about 230 kms a second, or 500,000 miles per hour, allowing it to stay in orbit instead of being pulled right into the black hole. Each complete rotation is known as one galactic year or cosmic year.
But most of humanity won’t be able to celebrate the Sun’s rotation – at least not in our lifetimes because it takes anywhere from 220 to 250 million years for the sun to complete one galactic rotation. In other words, if we were to switch measurement of time with the cosmic year, the Earth would be only 16 years old, the sun would be 20 years old, and the universe will have formed just about 60 years ago.
This didn’t deter a group of enthusiasts to celebrate Galactic Tick Day, which celebrates the journey the sun takes around the circular disc of the Milky Way galaxy. To make the Galactic Tick Day more compatible with human lifespans, the holiday was divided into smaller chunks of time so that it arrives every 1.77 years, during which period the sun completes one centi-arcsecond of its orbit around the galaxy.
The Galactic Time Frame Isn’t Consistent
Because the rotation takes place over incredibly vast celestial distances, the time frame for the cosmic year is not consistent. Scientists peg the number to be around 220 to 230 million years – the difference of 10 million is colossal for human lifespans. The folks behind Galactic Tick Day settled with an estimate of 225 million years for the sake of consistency.
When is the Next Galactic Year – 2020 Update
The last galactic year coincided with September 29, 2016, which happened to be the 235th Galactic Tick Day. The next galactic year would occur 225 million years later, also known as the cosmic year.