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Ch. 4: Between the Galaxies
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Author:  Chris OConnor [ Thu Oct 12, 2017 2:39 pm ]
Post subject:  Ch. 4: Between the Galaxies

Astrophysics for People in a Hurry
by Neil deGrasse Tyson

Ch. 4: Between the Galaxies


Please use this thread to discuss this chapter.

Author:  Cattleman [ Wed Nov 22, 2017 1:32 pm ]
Post subject:  Re: Ch. 4: Between the Galaxies

"The universe is not only queerer than we imagine, but queerer than we can imagine." J. B. S. Haldane, Possible Worlds and Other Papers (1927).

Dwarf galaxies, runaway stars, gas clouds, dark matter, etc. etc. ad infinitum. :hmm: And here I thought inter-galactic space was empty. :? Of course, as Tyson reminds us, such ignorance is honest; without the aid of powerful telescopes and other modern detecting devices, we had no way of knowing what was out there. (A side note; 'ignorance,' traced to its roots, simply means 'without knowledge.' There is nothing wrong with ignorance; it is simple recognition that you do not know something. This is not to be confused with 'stupidity' which implies not only a lack of knowledge, but a lack of desire for knowledge.)

It is also interesting to note the (honest) misnaming of many celestial objects; the "Milky Way" (actually the dense center of our own galaxy), the Great Nebula in Andromeda (now the Andromeda Galaxy), the Greater and Lesser Magellanic Clouds (dwarf galaxies). Not bad for naked eye astronomy.

Obviously, the universe is a very crowded place. :yes:

Author:  Interbane [ Thu Nov 23, 2017 8:26 am ]
Post subject:  Re: Ch. 4: Between the Galaxies

I always think of space as a simple place. Gas clouds and burning balls and orbs of rock. I always remind myself that this very same territory - space - is where life arose. There are complexities we can't imagine, hidden by distance. The apparent simplicity is only because I consider space on a macro scale.
There's good little bits all over if you look close. Heavenly bodies all various enough to warrant a classification system that is still being thwarted by new discoveries. The expanse isn't a simple place. It's just easy to ignore.

Author:  Harry Marks [ Fri Nov 24, 2017 3:28 am ]
Post subject:  Re: Ch. 4: Between the Galaxies

All this blithe talk of star formation and galaxy formation loses, to my mind, the sense of the time scales involved. It took billions of years to produce enough heavy elements to seed the Solar System with the stuff of the dense inner planets. Gravity is humble in its slow but steady pace, yet it eventually fires up thermonuclear generators in the form of stars, and pulls together enough of this to make the dazzling array of galaxies.

Then it "suddenly" crosses a threshold, for a large enough star, into sufficient heavy interactions to explode the star in a supernova, visible even from other galaxies at unimaginable distances. Is gravity like war, dragging on in long periods of complete boredom, only to erupt into brief moments of complete terror?

Author:  Taylor [ Fri Nov 24, 2017 9:59 am ]
Post subject:  Re: Ch. 4: Between the Galaxies

Harry Marks wrote:
Is gravity like war, dragging on in long periods of complete boredom, only to erupt into brief moments of complete terror?
.
It's like hand to hand combat at twenty paces.

Author:  Harry Marks [ Sat Nov 25, 2017 9:18 am ]
Post subject:  Re: Ch. 4: Between the Galaxies

Taylor wrote:

It's like hand to hand combat at twenty paces.

With a lot of circling around.

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