After Hours

General discussion


size of the Universe

By john.a.wills ·
Tags: Off Topic
Claudius Ptolemy, whose Almagest was the standard astronomy text from his days till the end of the Middle Ages, when Copernicus, Galileo and Newton brought in a lot of upsetting stuff, stated that in comparison with the distance to the stars the Earth must be considered a point. The stars, in other words, are inaccesibly far away. But nowadays we have exponential notation. The Earth is 1.35 x 10^7 m in diameter, not a point, the Sun is 1.5 x 10^11 m away, and the nearest "fixed" star is 6 x 10^16 m away. So our notation makes the Universe more accessible than it was.
Furthermore, in the Middle Ages it was thought that things beneath the Moon were made of 4 or 5 elements whereas the heavenly bodies were made of something quite different. But nowadays we think that the heavenly bodies are made of the same 100-odd elements we know on Earth, with the possible exception of dark matter. So the Universe is not only smaller, it is homelier.

This conversation is currently closed to new comments.

Thread display: Collapse - | Expand +

All Comments

Collapse -


by boxfiddler Moderator In reply to size of the Universe

'homelier'. What does that say for our eyes?

Collapse -

Maybe, "homey-er". (U.S. Eng.)

by seanferd In reply to Hmmm...

Comfortable, home-like, describing a domicile which would make a good home in the speaker's opinion. As opposed to applying it to a person, which I have always found odd. (Perhaps meaning one who is so "plain" that he or she would never leave their parent's home, or one who could be trusted to stay home by default, and not "run around".

Weird is language.

Collapse -

In contrast, perhaps, to "Comely".

by AnsuGisalas In reply to Maybe, "homey-er&quo ...

"Come-hither-ly" Vs "Home-you-go-ly"

Collapse -


by seanferd In reply to size of the Universe

The stars not being plastered into a crystal sphere, all an equal distance* away, made conceptualizing the universe more difficult or less comfortable? I suppose it depends on one's mindset.

*Theorized to be at a much smaller distance than the closest real stars.

What blows my mind is that one cannot observe or guess at the size of the universe. The greatest distance to which we can see is the same distance EM radiation has been able to travel since <i>recombination</i>. We may be able to "see" 13.5-14 billion light years out, but that in no way is the "edge" of the universe.

Sci-Fi may give people the impression that the stars themselves are more accessible now, but they really are not. As to grasping the distances involved, I suppose people are more or less inclined to believe they can do this just because measurements have been taken, and represented by usable numbers.

I wonder how many people exposed only to ancient cosmologies would find the universe to seem either smaller or larger once introduced to modern cosmology. It would probably interests psychologists, sociologists, and anthropologists.

Collapse -

Not to mention

by santeewelding In reply to Interesting.

Being tripped up by "uni-".

Yes. I speak twice.

Collapse -

This, indeed, is a consideration.

by seanferd In reply to Not to mention

Both statements are worthy of consideration, in my thinking.

Collapse -

Less accessible, definitely...

by AnsuGisalas In reply to Interesting.

See, before it was taken for granted that God might move a person to the stars.
This is not now a universally held idea.

Collapse -


by santeewelding In reply to Interesting.

Who comes out of the woodwork when you talk of these things...

Collapse -

Of course...

by AnsuGisalas In reply to See

how else would those wormholes get into the wouldwork to begin with?

Collapse -

crystal spheres?

by john.a.wills In reply to Interesting.

Ptolemy did not teach the doctrine of the crystal spheres; that was Aristotle (or someone earlier). Ptolemy thought the planets moved in cycles and epicycles.

Related Discussions

Related Forums