The galaxy is larger, from centre to outer arms, than four puppies laid head to tail. But that's partly because if you try it they'll keep wandering off.
Posted on 02/24/2016 1:10:36 PM PST by sparklite2
Unluckily the universe turns out to be incredibly complicated. The sheer amount of stuff
in it is mind-boggling. Do you know how many stars there are in a galaxy? You're probably
thinking of a large number, like 107, but there are way more than that! There are more stars
in the galaxy than grains of sand in a small handful of sand. The combined weight of gasses
swirling about the milky way is so much greater than that of a large dog as to make the
comparison seem unhelpful and arbitrary. The universe is actually much larger than Canada.
The galaxy is larger, from centre to outer arms, than four puppies laid head to tail. But that's partly because if you try it they'll keep wandering off.
But imagine if we could simulate an entire universe, not just down to the scale of galaxies,
but right the way down to individual earth-like planets. The authors of this paper imagined
that, then they stopped imagining it because they'd done it.
(Excerpt) Read more at astrobites.org ...
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I have a book, in hardcopy, entitled ASTRONOMY, by AGNES M. CLERKE, published in 1898. It's from THE CONCISE KNOWLEDGE LIBRARY, and aims to be an authoritative account for the layman of the subject.
The very last chapter, VII. THE CONSTRUCTION OF THE HEAVENS of Section IV - THE SIDEREAL HEAVENS, is most "illuminating" in regard to this "interesting thought".
In the first place, it was unknown at that time that the sun was situated in a "galaxy", and the stars of the Milky Way were at that time understood as "the universe", and the very crudely perceived dimensions of our galaxy were construed as the dimensions of the "heavens" or universe.
Most interesting is the discussion of the Andromeda Nebula. It was known at that time that its spectrum resembled the stellar spectra, and the idea that it might be an "external universe" is entertained, only to be rejected, on the ground of the great distance that would imply.
A lot of flexibility of mind is shown, however. It is suggested that our galaxy, or "universe" might be held in isolation by a bubble of luminiferous ether, for example.
Utimately, it seems that it was just very difficult to evaluate the immense scale of the observable heavens.
Even in my lifetime, the growth of knowledge has been amazing. I remember commenting to a grade school teacher that it looked like the continents could fit together. She said it was just a coincidence. Mars still had ‘canals.’
It has been a great time to be alive.
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