Before we invented civilization our ancestors lived mainly in the open out under the sky. Before we devised artificial lights and atmospheric pollution and modern forms of nocturnal entertainment we watched the stars. There were practical calendar reasons of course but there was more to it than that. Even today the most jaded city dweller can be unexpectedly moved upon encountering a clear night sky studded with thousands of twinkling stars. When it happens to me after all these years it still takes my breath away.
stars space astronomy exploration night-sky
At every level in our inventory, nothing seems special about our Earth, our Sun, our Galaxy, our Local Group. Evidently, mediocrity reigns throughout. Such is our niche in the Universe.
earth universe sun astronomy galaxy
Though we might like to think so, humankind is not at any special, unique or privileged location in the gargantuan, perhaps infinite, Universe.
earth universe astronomy humankind
There is nothing particularly special about that location of the centre of mass. If you were to find yourself at the precise spot that is the centre of mass of the earth-moon system, the only thing unusual that you would notice is that there would be one thousand miles of rock on top of your head. Pluto is only about twice the size of Charon, so if you put Pluto and Charon on the cosmic seesaw you would find that the balance point is a little bit outside Pluto, rather than inside it. Again, there is nothing particularly special going on there. If you were to find yourself at that precise spot, you would only notice that you were very, very cold and could no longer breathe.
earth astronomy
Let's grant that the stars are scattered through space, hither and yon. But how hither, and how yon? To the unaided eye the brightest stars are more than a hundred times brighter than the dimmest. So the dim ones are obviously a hundred times farther away from Earth, aren't they?Nope. That simple argument boldly assumes that all stars are intrinsically equally luminous, automatically making the near ones brighter than the far ones. Stars, however, come in a staggering range of luminosities, spanning ten orders of magnitude ten powers of ten. So the brightest stars are not necessarily the ones closest to Earth. In fact, most of the stars you see in the night sky are of the highly luminous variety, and they lie extraordinarily far away. If most of the stars we see are highly luminous, then surely those stars are common throughout the galaxy. Nope again. High-luminosity stars are the rarest. In any given volume of space, they're outnumbered by the low-luminosity stars a thousand to one. It's the prodigious energy output of high-luminosity stars that enables you to see them across such large volumes of space.
astronomy physics
Across the sea of space, the stars are other suns.
space astronomy space-exploration
Mathemata mathematicis scribuntur.
latin astronomy mathematics
A circle has no end.
paradox astronomy geometry
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