Cultivating a sense of the galactic centre

20.51, Wednesday 30 Jun 2021

About 10 years ago I cultivated a sense of the direction of the centre of the galaxy.

I’ve lost the knack now, but it was something I would do while I was waiting for the bus each morning.

At the beginning, I used the night sky app Star Walk. It has an augmented reality view, so I would swing the phone round until I found the constellation Sagittarius, and if you look in that direction and head about 26,000 light years, you get to the supermassive black hole at the centre of the Milky Way, Sagittarius A*.

(The light reaching the centre of the galaxy right now will have left the Earth 26,000 years ago, the Upper Palaeolithic, around the time of the invention of weaving and permanent settlements.)

So I would end up pointing through the pavement, or down a street, and thinking, huh, that’s where it is. And it’s a nice trick if you can do it, but it’s better when you can do it at any time, without an app. Which is what happened.

First I got good at figuring out the ecliptic. That’s the flat disc of the Earth’s orbit (and the solar system). If you wave your arm along the path that the Sun makes across the sky, that’s the disc.

Then I can’t remember how I would locate Sagittarius each day (it lies on the ecliptic) but I trained my intuition by checking the app each day. Over the weeks and months, I could follow how the position changed (at the same time each day as I caught the bus). First through the ground that way, then under the ground further that way, and so on.

Eventually then I had this picture of myself, and the Earth, and the solar system, and the centre of the galaxy which had initially been whirling round me, and now it had flipped, I was turning around it.

It was wildly situating.

The feelSpace belt uses vibrating motors and neuroplasticity to give humans a sense of “north.”

Every morning after he got out of the shower, Wächter, a sysadmin at the University of Osnabrück in Germany, put on a wide beige belt lined with 13 vibrating pads – the same weight-and-gear modules that make a cell phone judder. On the outside of the belt were a power supply and a sensor that detected Earth’s magnetic field. Whichever buzzer was pointing north would go off. Constantly.

“It was slightly strange at first,” Wächter says, “though on the bike, it was great.” He started to become more aware of the peregrinations he had to make while trying to reach a destination. “I finally understood just how much roads actually wind,” he says.

The brain is super good at incorporating this new sensory input. The result? Eventually, I felt I couldn’t get lost, even in a completely new place.

I’ve never tried this, though I would love to. Periodically there are semi-commercial versions:

But I haven’t yet seen something that I could imagine myself wearing every day for a few months. I would like it as part of my Apple Watch. (Could that be done?)

Some animals do have a sense of north! Birds can literally see the Earth’s magnetic field – and it’s possible that humans have a north sense too (as previously discussed).

HOWEVER: I did have a glimpse of what this would be like.

A few years back I visited Marrakesh.

The old city is a tangle of roads and alleys and souks and neighbourhoods. It’s fun (and inevitable) to get disoriented and lost.

But one particular day we set off from a junction back to our riad, only to end up back at the junction 30 minutes later. So we set off in another direction… and 30 minutes later we found ourselves back there. Repeat. Repeat.

Then we realised that all the buildings had satellite dishes, and all the satellite dishes were aligned south. So matter how turned-about we got, we could always have a sense of the cardinal directions. It was an incredible moment. I had a tiny peek at how a swallow sees the world, the door opened just a crack to the magnetosensitive avian umwelt.

The satellite dishes oriented me in the city just as a sense of the location of Sagittarius A* oriented me in the galaxy.

Are there words for the cardinal directions of towards/away/etc with respect to the galactic centre? Galinwards. Galockwise.

So I wonder about the best way to re-train myself as to the location of the galactic centre? I enjoyed the perspective. It’s been a decade.

In my imagination I see an iPhone app which displays a 3D model, connected to the gyroscope and the compass and the GPS.

It would show, diagrammatically, the sphere of the Earth and a sharp line where I’m standing, and the ecliptic and the Sun, and glowing at the edge of the disc of the ecliptic: the constellation of Sagittarius. Then a floating arrow labeled, “Galactic Centre: 26,000 light years.”

The whole thing would be in 3D, centred on the icon of me standing on the Earth, and it re-orient as I moved the phone in my hand. So the 3D arrow would point the way. Perhaps it would buzz with increasing intensity until I pointed the phone the right way. Perhaps even it would bother me with a notification at a set time each day to have a guess!

The purpose of showing all the moving parts is to help with building intuition.

Maybe it’s an app. Maybe it’s a mobile website. Every so often I poke around at trying to build this for myself (there are a bunch of astronomical coordinates code libraries out there). But there are slightly too many things I would need to learn for it to bump its way to the top of my project list.

Which is why I’m sharing it here. I’d love to have a go if you make it.

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