Amazingly enough, the first attempt to simulate galaxy interactions (1941) predated computers & used light bulbs! The trick is that the gravitational force and electromagnetic force (for light) both vary as 1/distance^2; Erik Holmberg realized this meant he could use light to simulate galaxies. 🧪 - ThreadSky

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mbkplus.bsky.social • 98 days ago

Amazingly enough, the first attempt to simulate galaxy interactions (1941) predated computers & used light bulbs! The trick is that the gravitational force and electromagnetic force (for light) both vary as 1/distance^2; Erik Holmberg realized this meant he could use light to simulate galaxies. 🧪

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astrobailin.bsky.social•98 days ago

I love that paper. He spends a significant amount of it demonstrating that the light bulbs are isotropic!

ngc3314.bsky.social•98 days ago

Ahead of a meeting ~1990 I wrote to Holmberg for a photo of his setup. He replied, there were none - it was basically the darkened inside of a barn all draped in black to avoid reflections and scattering. (Bonus, I suspect the finite size of the photocells played the role of a softening length...)

astrobailin.bsky.social•98 days ago

Someone ought to replicate it! Imagine a AAS exhibit where you can come join in and help make measurements/move bulbs. See how far you can get over the course of the conference.

berfield.com•98 days ago

That's amazing.

tmac223.bsky.social•98 days ago

I recently heard that multiple smaller galaxies are currently interacting with the Milky Way. Is that true I wonder?

mbkplus.bsky.social•98 days ago

Yes! There are at least 50, and maybe up to 500 or so more undiscovered, satellite galaxies orbiting the Milky Way. Most aren’t interacting directly with our galaxy but several have been through the Galactic disk and have even been whittled down by these interactions.

mbkplus.bsky.social•98 days ago

The search for undiscovered dwarf galaxies, which can be as light as 100 times the mass of the sun (!!), is one of the key science drivers of the Rubin observatory, which is set to begin operations next year.

kwh561.bsky.social•98 days ago

It's good to be in the galaxy that does the whittling rather than being whittled.

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