Discoveries of astronomy: How did they do that? / General Science and Electronics / Forums

Forums

4hv.org :: Forums :: General Science and Electronics

« Previous topic | Next topic »

Discoveries of astronomy: How did they do that?

Move Thread

LAN_403

IamSmooth

Sun Jun 25 2006, 02:10AM

Registered Member #190 Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567

I have an interest in astronomy and astrophysics. I have searched books and the internet for the ways and means man through the ages has solved the puzzles of the universe. Examples include how man proved the earth was round, the distance from the earth to the moon and sun, and the mass of the sun. Does anyone know of a book or reference to were one can find all of this information in one place?

benbradley

Sun Jun 25 2006, 03:46AM

Registered Member #312 Joined: Mon Mar 13 2006, 01:50AM
Location: Georgia, USA
Posts: 27

I recall, I think from one of Isaac Asimov's books (I can't possibly remember the title - he wrote at least 400 books, but this would be a non-fiction book which narrows it down some) the story of using Alexandria and another town to measure the Sun's angle at noon, and thus measure the size of the Earth. Googling:
Alexandria Earth Sun distance
brings interesting links, perhaps the most relevant is:

under "Measurement of The Earth."
This link, "How distant is the Moon?", looks good too:

Does anyone know of a book or reference to were one can find all of this information in one place?

How much do you want to know? There's a LOT of these things. Galileo got a good approximation of the speed of light by noticing that the orbits of Jupiter's moons were a few minutes (time wise) off from the positions they "should have been" based on observations made six months earlier, when the Earth was at a different distance from Jupiter. There are several methods for finding the distances to stars, each one working over different ranges of distance. I don't remember them all, but using parallax, nearby stars move back and forth over the background of more distant stars yearly because of the orbit of the Earth shifts our viewing position.

One book may have many such things in it (this would have been a good idea for Asimov to write a book on, but I don't recall if he wrote such a book), but there are too many of these discoveries to fit into one book.

I've read many dozens, perhaps hundreds of 'popular' books on science. I've always found it fascinating to learn, not just the results, but how these things were discovered. My advice is just keep reading - You'll learn most or all of the things you want, but you'll also learn things you didn't know you wanted to know!

IamSmooth

Sun Jun 25 2006, 03:53AM

Registered Member #190 Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567

I know the answers to the examples I gave. I am asking is there a book that includes all of the great discoveries. I can go on with more examples:

earth-moon distance
earth-sun distance
mass of moon
mass of earth
mass of sun
earth-planet distances
Proof that the planets revolved around the sun
speed of light

Answers to some of these questions include Alexandria, like you mentioned. Others used the Transit of Venus, Kepler's laws of motion, Jupitor's moons, Michaelson and Morley, and so on.

I have not seen a book that has all of these in one place. Does anyone know?

Carbon_Rod

Sun Jun 25 2006, 03:53AM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155

Unfortunately the biggest puzzles of the day are rather tricky to explain in full. To understand why events like mars seemly traveling back and forth in the sky required some blasphemous ideas and intermediate calculus (most universities will cover this classic problem in 2nd or 3rd year math and physics courses.) Most good books on this subject are pretty thick reading for some people â€“ astrophysics is a very interesting field.

Statistical observations that lead Hubble to the system of aging solar systems.â€ His greatest discovery was the linear relationship between a galaxy's distance and the speed with which it is moving.â€ (

)

The greatest advancement in the last few years in my opinion has been the interferometer-based observations showing planetary activity in other galaxies. It does rather inspire peoplesâ€™ imaginations.

wikipedia is a good place to start:

Cesiumsponge

Sun Jun 25 2006, 04:44AM

Registered Member #397 Joined: Wed Apr 19 2006, 12:56AM
Location: Western Washington
Posts: 125

Retrograde motion of Mars was observed in ancient times. Since the geocentric model was still popular, I recall someone developed an increasingly convoluted model including additional circular orbits of Mars that would produce the retrograde motion while fitting the popular model at the time.

Finding out the Earth was round could be observed by ships sailing into the horizon and gradually dissapearing. When I took astro in college, we covered a fair share of history too which was a nice interesting complement to plain mathematical material but I forgot most of it without revisiting textbooks.

The mass of the Earth was slowly developed over time. A greek (forgot name) or two measured shadows in the aforementioned Alexandria and Syene. Cavendish measured G=6/67x10^-11 xxx (forgot unit) Galileo figured out 9.8m/s^2. Newton developed his F=ma, subsituted the proper variables, and came up with the mass

There probably exists a compendium on the history of astronomy...and if there isn't, there should be. A lot of stories behind scientific discoveries are interesting in itself...especially the accidental ones or the ones that took centuries in the making with gradual blanks being filled in.

We just tend to not give our ancestors enough credit and saw them as primitive or scientifically/technologically naive people. They are, for all practical purposes, identical to you or I today...and many of them had a lot of spare time to ponder and argue the nature of the universe and to lay out the basic foundation of astronomy, since none existed.

Simon

Sun Jun 25 2006, 11:24PM

Registered Member #32 Joined: Sat Feb 04 2006, 08:58AM
Location: Australia
Posts: 549

wrote ...

We just tend to not give our ancestors enough credit and saw them as primitive or scientifically/technologically naive people. They are, for all practical purposes, identical to you or I today...and many of them had a lot of spare time to ponder and argue the nature of the universe and to lay out the basic foundation of astronomy, since none existed.

Indeed. It's often forgotten that Eratosthenes' method of calculating the size of the Earth assumes the Earth is round. That's one example.

Reading something like Galileo's A Discourse on Two Sciences (I think that's the name) or Archimedes' On Floating Bodies is fascinating. These people were so clever and did so much more than the usual pop history gives them credit.

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob