1/ We belong to a system of planets revolving around a beautiful star.
2/ Just at the edges of the solar system lies remnants from the early days that couldn’t assemble into a planet.
This disc is called the Kuiper belt.
3/ But the influence of our sun goes much beyond the planets and the Kuiper belt.
We’re surrounded by a spherical shell of billions of icy comets that extend 100,000 times as far as Earth is from sun.
It’s called the Oort cloud.
4/ The nearest star - Proxima Centauri - is about six times even further away.
5/ Of course, we all are embedded within the Milky Way, home to 100 billion stars like our sun.
Each pair is as far away from one another as Sun is from our nearest neighbour.
Our galaxy is truly staggering.
6/ Our nearest neighbour galaxy, Andromeda, is so far away that when we look at it, it appears to us as it was 2.5 million years ago.
It’s on a collision path to us, which will eventually create a new home for us - the Milkdromeda.
7/ Gravity binds stars within a galaxy.
Just the same way, neighbourhood galaxies are bound in a structure called the Local Group.
It contains Milky Way, Andromeda and ~50 other galaxies.
8/ Our local group is gravitationally bound in a supercluster of galaxies called the Virgo supercluster which contains the Local Group and many other such galactic clusters.
9/ Can structures in the universe get even bigger than the super clusters?
Yes!
The biggest known structure we belong to is called Lanieka supercluster. It contains Virgo superclusters and many other ones.
Our Lanieka is moving towards a point known as the great attractor.
10/ Finally, even the Lanieka supercluster is a tiny portion (~0.00001% by volume) of our entire observable universe.
Our observable universe is *huge*.
11/ Does anything lie beyond what we can observe in the universe?
Yes, it’s highly unlikely that the universe suddenly ends beyond our horizon.
Many scientists believe that it is infinitely huge, although nobody knows what that *really* means.
Can infinities exist physically?
12/ That’s it!
Hope you enjoyed the thread.
It blows my mind that universe may be finite or infinite. Both possibilities fill me with strange awe.
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1/ It’s mind-blowing that we humans are able to talk about what happened in the first 3 minutes of The Big Bang.
This book was written in 1976 which was quite a while back but while there have been extensions in the ideas presented, I’m not aware of any idea being rejected yet,
2/ This should perhaps be unsurprising because most scientific ideas that are accepted as truth are consilient, i.e. they’re supported by multiple lines of evidence.