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Notes Regarding Dupuis’ 1910 Elements of Astronomy [pdf] (gron.ca)
83 points by mymythisisthis 18 days ago | hide | past | favorite | 14 comments

It is worth remembering that we are barely 100 years from the time in which the notion of galaxies was not common. The textbook itself discusses Nebulae near the end, in all of 2--3 pages.[1]

From p. 199: It was consequently thought, at once, that all nebulae might be shown to be star clusters under sufficiently high powers of the telescope. But the spectrascope has shown that such an inference is untenable, as the spectra of the two things are quite different, and that the spectrum of a nebula contains a line which is found nowhere else, and which is attributed to some substance called nebulum, and which is totally unknown anywhere except in a nebula.

I propose we adopt neo-nebulum as a more neutral term than dark matter!!

[1] https://archive.org/details/cu31924031322203/page/n213/mode/...

Other 1910 astronomy questions: how do star work? How are they powered? Do they just cool forever from their birth? Do they contract to the point of becoming liquid?

What ended up being the cause of that mysterious spectral line?

Ha! Didn't occur to me to search the archaic name on Wikipedia, but in hindsight, of course that works.

There are some great anti-flat earth examples in here - digging canals having to drop 8" per mile is obvious when you think about it. Objects being heavier at the poles and pendulums running faster because the earth is oblate, not a perfect sphere is also a clever illustration.

Speaking of astronomy books, I wish there were a (history of) physics book that would not assume any prior knowledge about astronomy or cosmology on the reader's part and slowly build up the (currently accepted) theories of cosmology and astrophysics, starting from "See those bright spots on the sky? We call those 'stars' and we have reasons to believe that they are similar in nature to our sun because […]." to "This is how we measure distances (assuming a flat background) to nearby stars"[00] to "This is how we know what the Milky Way looks like and that there are other galaxies outside ours[0]" to "This is why we are convinced that the universe at large scales is best described by an FLRW spacetime with cosmological constant > 0 and there was a Big Bang et cetera".

The issue is that, ultimately, the only thing we can observe is electromagnetic waves[1], characterized by frequency, polarization and intensity, and originating from some point on a 2D sphere. Everything else is interpretation[2]. So cosmology today consists of dozens of layers of interpretation stacked upon one another and for me (as a mathematical physicist who once dabbled in cosmology but is ultimately an outsider to the field) it's hard to keep track of all the assumptions and the causal chains of observations and interpretations that are implicit in today's widely accepted results.

To give an example, people say that the universe is expanding and they point to redshift (~ (apparent) velocity) measurements such as those done by Hubble. Great, but how do you measure redshift as a function of distance if all you see is a 2D sky and you can't "see" the axis parallel to your line of sight? You introduce various distance measures like angular distance and luminosity distance which are based upon the notions of standard rulers and standard candles. But these are not exactly trivial to get right, either[3], and AFAIU rest upon an entire body of theories from astrophysics and plasma physics. Plus, there are countless of things that can happen to electromagnetic waves on their way to Earth (absorption, gravitational lensing, Sachs-Wolfe effect, …) and you must account for those, too.

Don't get me wrong. I'm not trying to cast doubt on any of the currently accepted theories. Not in the least. Nor is the particular example above not well-understood. I'm just saying that, for an outsider, it's not easy to follow the chain of implications sometimes and many books don't do a very good job of logical bookkeeping. A book painting the architecture of the Standard Model in broad but logically accurate strokes would go a long way.

Meanwhile, I notice reruns of "Through the Wormhole" on TV every other year with Morgan Freeman going on about hypotheticals like string theory, parallel universes and such, while completely foregoing the (well-established but IMO still exciting) "basics". It's almost physically painful to imagine what additional confusion this must cause the layman that knows barely anything about physics in the first place. Any sufficiently advanced physical theory is indistinguishable from magic comes to mind.

[00] See the conundrum there?

[0] https://en.wikipedia.org/wiki/Galaxy#Observation_history

[1] and some ionized radiation, and now of course gravitational waves.

[2] "Everything is interpretation" not in the esoteric sense but of course in the sense that we draw logically stringent conclusions based upon already well-established physical theories.

[3] https://en.wikipedia.org/wiki/Cosmic_distance_ladder#Problem...

Isaac Asimov's _Understanding Physics_ is older (1966) but is meant for the general reader or to supplement a textbook. It uses algebra and only a little trig.

J. D. Bernal's _A History of Classical Physics_ (1972) begins with ideas from ancient Greece and goes to the end of the 19th century. No math, but lots of pictures and diagrams. I have a 1997 reprint.

Stephen F. Mason's _A History of the Sciences_ (1962) covers chemistry and biology as well as physics, from Babylonia and Egypt to the mid twentieth century.

I am sure there are many others, but these, which include history and biography as well as scientific content, are good, readable overviews.

That's why I really like Dupuis's 1910 textbook. Gets the right amount of basic information and math.

I'd really like to see how Newton, Kepler or Copernicus went about making their calculations, step by step. Break it down point by point to make it understandable without skipping steps. Like to see how Ptolmey constructed the star table.

Too many science books are either popular in nature with no math, or for someone doing a masters in the field. I guess there is not a large enough audience of people in the middle to justify writing such books.

This is a bit of a shameless plug, but I'm an astronomer who has been interested in these kinds of questions for a long time and earlier this year started a podcast to delve into answering them. It's a history of astronomy starting with the Babylonians and working towards modern astronomy (though at one episode a month it will take a while to get all the way through).

My intention has been to take the astronomy of each era on its own terms and try to understand what questions they were trying to answer and what techniques they used to answer them. You tend to read things like "the Ptolemaic system was geocentric and had to use lots of epicycles to work and then 1500 years later Copernicus introduced a heliocentric system that didn't need epicycles." but I'm trying to explain how these systems developed, why epicycles seemed to be natural, how they figured out what epicycles were needed based on the observations they had made, etc.

The website is here if you're interested: www.songofurania.com

This was a good read https://archive.org/details/historyofplaneta00dreyuoft History of the planetary systems from Thales to Kepler by Dreyer

Yes, I have that book! It's excellent and one of the ones I use as a source. A few others that I've found to be really good:

* A History of Astronomy by Pannekoek

* Aristarchus of Samos by Heath (this is actually a much broader history of Greek astronomy than its title suggests)

* Episodes in the Early History of Astronomy by Aaboe

* Exploring Ancient Skies by Kelly & Milone (much more technical, but also broader and more up to date than the other books)

Hi, maybe you can give me some advice about what to read. I'm looking for a book/video that would give me a step by step account of how early astronomers worked. How they actually took a reading, what corrections they made, and specifically how they did all their calculations. I found this video on celestial navigation really great https://www.youtube.com/watch?v=yu5R5mrrGB0&t=611s it walks a person step by step through navigation. Looking for something like this, but showing how a star catalogue, like the Rudolphine Table, is compiled.

The Earth by Hubert Krivine (ISBN:978-1-78168-799-4) does exactly this for the case of the Earths age and motion around the Sun, so that's a start.

If your ambition is a more detailed history of science account of the establishment of the distance ladder (up to some slightly distant point in time, as work is still ongoing, see the famous Hubble tension), try googling for articles about history of science and the distance ladder. That activity gives me this preview that might be interesting: https://www.jstor.org/stable/24536521

A full version can probably be found online.

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