- The Milky Way
- How it formed
- It's size
- The experience
- Our neighbour Andromeda
- The Virgo supercluster
The Milky Way
How it formed
Timothy Ferriss, Seeing in the Dark
Around us is a vast galaxy arrayed on scales so gigantic that galactic structure becomes discernible only once the solar system has dwindled to a dot the size of the period of this sentence.
If the observable universe was shrunk to the size of the Earth, our galaxy would be the size of about 4 golf balls side by side.
And it's even bigger than that, because hydrogen extends out twice as far as the visible part of galaxies, AND gamma-ray bubbles extend 50,000 light-years.
- Using my Drake equation, I guess that there are ~7 civilizations in the galaxy at this time. If they are all evenly spaced out, the nearest would be a minimum of 15,000 light years away. The more likely life is, the closer the distance.
- First question: Can signals still deliver a meaningful message over that distance?
- If they can't, then we might never hear from anyone unless they emit a special signal, or they come to us.
- If they can, the civilization must have been emitting signals from at least 15,000 years ago. They may be long dead by the time we get it. No matter.
- Perhaps to make first contact, we need to develop the technology for communication at this kind of distance - it's on these wavelengths that we are most likely to hear something.
The outer edges is where complexity is.
But 90-99% of it is hydrogen.
Most matter sits eternally in coldness and darkness
Our neighbour Andromeda
This is how Andromeda would look in our sky if it was brighter
- And that's only the size of the visible part - the hydrogen extends to twice that size if you look with a radio telescope (21 cm, 1420 MHz).
- Reddit community, Andromeda's actual size if it was brighter
The Virgo supercluster
They are absolutely everywhere.
These are our neighbours. We will never reach them in any state of civilization conceivably similar to our own. We just ride into the Great Attractor together.
If you could see what a tiny scrape of the night sky actually contained, you would see this.
- Google sky can carry it home