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Comment by forgot_my_pwd | Hacker News Reader

It's quite interesting how close galaxies are to one another relative to how far stars are from one another.

The distance from the Milky Way to Andromeda is only about 25 Milky Ways, but the distance from the Sun to Alpha Centauri is about 29 million Suns.

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When making this comparison, I think it is interesting to note that both the distances between Earth to Alpha Centauri and the Milky Way to Andromeda aren't "typcial".

To quote Douglas Adams, Earth is "Far out in the uncharted backwaters of the unfashionable end of the western spiral arm of the Galaxy". Intersteller distances are much smaller in galactic cores. For example, at the center of Andromeda, the average intersteller distance is 860 AU (compared to 266,900 for Earth-Centauri)[1].

Alternatively, Andomeda huge and on a colision course with the milky way, but not our closest neighbor. Both the Milky Way and Andromoeda have many smaller and closer neighbors, Some of which are of appreciable size. For example, the Large Magellanic Cloud is a "smaler" galaxy with about 30 billion stars and is 170kly or about one milky way diameter away from us.[2]

https://astronomy.com/magazine/ask-astro/2006/01/how-close-c...

https://en.wikipedia.org/wiki/Large_Magellanic_Cloud

Wikipedia has an apropos image of the brightened Magellanic Clouds to the bottom of that page, too: https://en.wikipedia.org/wiki/Large_Magellanic_Cloud#/media/...

I think a more apt comparison would be how many solar systems away we are. I calculate we are only 143-4550 solar systems away, depending on how you define the solar system (using the orbit of Sedna or Neptune as the radius).

I think you under by 50%.

Also 266,900 earth orbits away

Earth orbits != solar system diameters

That's implied by "Also".

Other interpretations of the GP would imply the GP thought 267,000 / 5,000 is about 1.5. I'm pretty sure the GP isn't making that mistake.

Indeed, we are star-huggers. Earth orbit is tiny when compared to the last round rocks we have around it.

Yeah, I don't know where I got whatever number I was using for sun-alpha centauri distance (I was converting from Milky Ways, I think). Today I calculate 1600 - 7300 solar systems, using wikipedia AUs. Maybe my calculator is broken, though...

I was thinking in terms of radii instead of diamters when I responded earlier.

That said, I think you might be interestested in the sister post I made to yours.

I was going to say much the same thing until I saw your comment, which already expressed what I was going to. This has also struck me for a while as being interesting.

if the sun, which is huge compared to the earth, were the size of a pea, the nearest star would be ~120 miles away to scale. this is a typical distance between stars and it’s why when andromeda collides with the milky way there is little chance of stars colliding.

I’ve heard, I think many years ago, this fact there is not much risk or star collisions when galaxies collide. But I wonder, given more recent knowledge of how common exoplanets are, if there is a more significant risk of disruptions to the planetary systems that surround the stars. These planetary systems are much larger than the stars themselves.

Stars are still sparse enough in both galaxies that most stars still wont have much effect on most other stars' planetary systems. On the scales of the galaxies a star system isn't much bigger than that system's star. A star affecting another's planetary system would pass so close it and the host star would likely form a gravitational relationship and would be considered a "collision". Space is stupid big and stupid empty.

I really like this demo to show how empty our solar system is: https://joshworth.com/dev/pixelspace/pixelspace_solarsystem....

Or the RL version in Sweden: http://www.swedensolarsystem.se/en/

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