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Well anyone can see a few million years back in time just by going outside on a dark night and looking at one of the nearby visible galaxies with their eyes. Kn

by gbrown 6y ago

Well anyone can see a few million years back in time just by going outside on a dark night and looking at one of the nearby visible galaxies with their eyes. Knowing that this is what is happening is indeed a great achievement.

inetknght 6y ago
Unfortunately, that's not quite true in many populated cities. Light pollution means the night sky is starless.
- gbrown 6y ago
  Not starless, surely. Stars like Sirius and Betelgeuse should be visible just about anywhere, and that gets you 8-500ish years back at least.
- cgriswald 6y ago
  Well, it’s sort of true. There are places within cities where you can’t see the Andromeda Galaxy, but you don’t have to leave those cities entirely in order to see it to some degree.
Keysh 6y ago
To be a bit pedantic: that’s only true for the Andromeda Galaxy (distance ~ 2,4 million light years), which is very hard to see with the naked eye. The Large and Small Magellanic Clouds are easy to see (from the Southern Hemisphere), but are only about 150,000-200,000 light years away.
- polishdude20 6y ago
  You could also argue that "seeing" doesn't necessarily mean "perceiving". I can point my eyes to the exact spot where the Andromeda Galaxy is, or even other galaxies further away, and not actually perceive anything. But tint amount of photons from that galaxy still hit my eye. But that's being obtuse..
- fairity 6y ago
  Can you clarify? Aren’t we still observing an old state of any galaxy we see in the skies, simply due to the fact that light takes time to travel to us?
  - planet-and-halo 6y ago
    I believe OP's point is that which state you're seeing varies by distance. We see Andromeda as it was millions of years ago, but we see other stars as they were "only" hundreds of thousands of years ago. Closer = more recent picture, Farther = older snapshot.
    - Keysh 6y ago
      Yes, exactly. (The Triangulum Galaxy, M33, can sometimes be seen; at ~ 3 million light years, it’s further away and thus an even older “snapshot” than Andromeda.)
- Florin_Andrei 6y ago
  > the Andromeda Galaxy (distance ~ 2,4 million light years), which is very hard to see with the naked eye That's due to light pollution in populated areas. If you're out in the deep desert, it's not that hard to see. The night sky in the desert is a very, VERY different experience from what most people have seen from the city. It's like you're on a different planet.
  - Keysh 6y ago
    I’ve seen it from fairly high in the Sierra Nevadas, far from any cities, and I still think it’s very faint.
    - Florin_Andrei 6y ago
      Make sure your eyes are dark-adapted. I.e. you've spent at least 20 minutes in pitch darkness, with no sources of light other than the sky. And no Moon. Altitude is not relevant in most cases.
- gbrown 6y ago
  To be more pedantic, you are incorrect that this is only true for Andromeda. Several other galaxies are visible with the naked eye under excellent conditions, though they can certainly be challenging. These include M81 and M33.
RHSman2 6y ago
Technically every thing you look at is in the past.

by gbrown 6y ago

inetknght 6y ago

Unfortunately, that's not quite true in many populated cities. Light pollution means the night sky is starless.

gbrown 6y ago
Not starless, surely. Stars like Sirius and Betelgeuse should be visible just about anywhere, and that gets you 8-500ish years back at least.
cgriswald 6y ago
Well, it’s sort of true. There are places within cities where you can’t see the Andromeda Galaxy, but you don’t have to leave those cities entirely in order to see it to some degree.

Keysh 6y ago

To be a bit pedantic: that’s only true for the Andromeda Galaxy (distance ~ 2,4 million light years), which is very hard to see with the naked eye. The Large and Small Magellanic Clouds are easy to see (from the Southern Hemisphere), but are only about 150,000-200,000 light years away.

polishdude20 6y ago
You could also argue that "seeing" doesn't necessarily mean "perceiving". I can point my eyes to the exact spot where the Andromeda Galaxy is, or even other galaxies further away, and not actually perceive anything. But tint amount of photons from that galaxy still hit my eye. But that's being obtuse..
fairity 6y ago
Can you clarify? Aren’t we still observing an old state of any galaxy we see in the skies, simply due to the fact that light takes time to travel to us?
- planet-and-halo 6y ago
  I believe OP's point is that which state you're seeing varies by distance. We see Andromeda as it was millions of years ago, but we see other stars as they were "only" hundreds of thousands of years ago. Closer = more recent picture, Farther = older snapshot.
  - Keysh 6y ago
    Yes, exactly. (The Triangulum Galaxy, M33, can sometimes be seen; at ~ 3 million light years, it’s further away and thus an even older “snapshot” than Andromeda.)
Florin_Andrei 6y ago
> the Andromeda Galaxy (distance ~ 2,4 million light years), which is very hard to see with the naked eye That's due to light pollution in populated areas. If you're out in the deep desert, it's not that hard to see. The night sky in the desert is a very, VERY different experience from what most people have seen from the city. It's like you're on a different planet.
- Keysh 6y ago
  I’ve seen it from fairly high in the Sierra Nevadas, far from any cities, and I still think it’s very faint.
  - Florin_Andrei 6y ago
    Make sure your eyes are dark-adapted. I.e. you've spent at least 20 minutes in pitch darkness, with no sources of light other than the sky. And no Moon. Altitude is not relevant in most cases.
gbrown 6y ago
To be more pedantic, you are incorrect that this is only true for Andromeda. Several other galaxies are visible with the naked eye under excellent conditions, though they can certainly be challenging. These include M81 and M33.

RHSman2 6y ago

Technically every thing you look at is in the past.