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Realm of the Nebulae
In less than a century, the accepted picture of the universe transformed from a stagnant place, composed entirely of our own Milky Way galaxy, to a realm inhabited by billions of individual galaxies, hurtling away from one another. We must thank, in pa
288 pages, Paperback
First published January 1, 1938
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About the author
Edwin Powell Hubble
25 books17 followersEdwin Hubble (1889–1953), American astronomer, who made important contributions to the study of galaxies, the expansion of the universe, and the size of the universe. Hubble was the first to discover that fuzzy patches of light in the sky called spiral nebula were actually galaxies like Earth’s galaxy, the Milky Way. Hubble also found the first evidence for the expansion of the universe, and his work led to a much better understanding of the universe’s size.
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Displaying 1 - 8 of 8 reviews
September 10, 2022
A bit difficult to read but because it was written by Hubble himself, I had to give it a minimum of 3 stars. I was also impressed with the photo plates and how clear they were considering they were taken from a telescope on earth, all the way back in the 1930s. I’m sure a lot of what Hubble writes about is still used in astronomy today and if I had an astronomy degree, I’d probably understand it more 😋
July 2, 2017
The short version first . . .
There are always books that are considered to be “ground-breaking,” “seminal,” “essential,” (add your favorite superlative here). In the field of history, the twelve-volume A Study of History by Arnold J. Toynbee is one such work, focusing on civilizations and how they grow and fail. In biology, the controversial The Origin of Species by Charles Darwin revolutionized scientific thought on the biological sciences. Add to these the work reviewed here, The Realm of the Nebulae by Edwin Hubble. Hubble’s work focuses on the nature of the universe by way of the study of cosmology.
Hubble’s work is unique in several ways. First, it is a summary of almost a half century of documented observational studies of the universe using observatories around the world. He gathered his data by reading the literature in multiple languages from the scientific literature in his field of study. Almost every page contains at least one or more notes documenting by title, volume, number and page, the names and article titles of the research and observations to which he refers in his own work, including his own articles and documented observations from Mt. Wilson Observatory, home of the then largest reflector telescope in the world, the 100-inch Hook Reflector.
During the early 20th century, the construction of reflecting telescopes with ever-increasing primary mirror (aperture) diameter was the order of the day. In 1908, a 60-inch Hale, followed nine years later with the construction of 100-inch Hook were the principal tools by which Hubbleand others made their observational studies. There were the central telescopes on Mt. Wilson in Southern California, and they would be among the largest telescopes on Earth until they were surpassed in 1948 by the 200-inch Hale reflector at Mt. Palomar which today barely makes the top 20 largest telescopes on the Earth list. Edwin Hubble’s work was some of the most extensive efforts in observational astronomy. By using every scientific monitoring device, special photographic imaging, special photographic emulsions by Eastman Kodak, and collaboration with colleagues, Edwin Hubble’s The Realm of the Nebulae culminates the work of many observational astronomers and brings their efforts into a crystal focus, answering questions about the basic workings of the universe in which we live.
Second, Hubble, widely regarded as the greatest observational astronomer of the 20th Century, included in his work reports on the work of his colleagues worldwide including and integrating their analyses and findings into those he was making using the best, largest telescope available at the time. His observations and his systematic approach to the analysis of the data he received from his viewing of the cosmos led to his discovery that the universe was expanding and had been doing so since the beginning of everything. In fact, if anything, the expansion was increasing at a steady rate moving large “island universes” (the term of others not Hubble’s) away from each other and our galaxy at a steadily increasing pace. The basic realization that Hubble documented was the consistent change in the way certain chemical element wavelength spectrographs would change from one object to another which were determined to be at different distances from the points of observation here on Earth.
Writing at the height of the Great Depression, Hubble carried on his research and reading, observing and mapping, graphing, reading reports of others, and bringing all of these factors together in a unique, seminal way using the laws of general relativity and the Doppler effect associated with the elemental spectrographic results to point to clearly shifted measurements for the same types of chemicals for diverse sources, all of which measured a set of data that consistently came together across most if not all observations across the planet. It was clearly a unique finding and one which answered one of the most important cosmological question – what is the nature of the universe? Collapsing, closed and fixed, or expanding? The preponderance of the data clearly indicated that expanding was what the answer was consistently showing across observers, across the world, and regardless of what part of the sky into which they looked. Expansion was happening everywhere. This specific aspect of the universe bears Hubble’s name, just as the first orbital space telescope was named for him as well.
The Realm of the Nebulae is a scientific report. It is very technical and scientific. It has a fair number of mathematical equations, and a very extensive set of notes on almost every page for either source citations or explanations of concepts with referencing as deemed necessary or helpful for clarity purposes. The discourse is technical, but the vocabulary is not as difficult as one might expect. It is a book for astronomy and cosmology researchers, enthusiasts, and historians of science and scientific discoveries. It also provides an inferential history of the progress made with each new aperture size when new instruments came on line. Recommended to anyone interest in the elements noted immediately above. If you are among that group, this book is a full 5 out of 5 stars for its topic. It is documented elegantly and clearly, it has a detailed and paginated index, and several black and white photographic plates and numerous charts, tables, and informative pieces of interest to the audience for whom the book is intended.
This review by Richard Buro is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.
Based on a work at https://www.goodreads.com/book/show/16073259-the-realm-of-the-nebulae.
Permissions beyond the scope of this license may be available at http://yalepress.yale.edu/yupbooks/contact.asp#permissions.
There are always books that are considered to be “ground-breaking,” “seminal,” “essential,” (add your favorite superlative here). In the field of history, the twelve-volume A Study of History by Arnold J. Toynbee is one such work, focusing on civilizations and how they grow and fail. In biology, the controversial The Origin of Species by Charles Darwin revolutionized scientific thought on the biological sciences. Add to these the work reviewed here, The Realm of the Nebulae by Edwin Hubble. Hubble’s work focuses on the nature of the universe by way of the study of cosmology.
Hubble’s work is unique in several ways. First, it is a summary of almost a half century of documented observational studies of the universe using observatories around the world. He gathered his data by reading the literature in multiple languages from the scientific literature in his field of study. Almost every page contains at least one or more notes documenting by title, volume, number and page, the names and article titles of the research and observations to which he refers in his own work, including his own articles and documented observations from Mt. Wilson Observatory, home of the then largest reflector telescope in the world, the 100-inch Hook Reflector.
During the early 20th century, the construction of reflecting telescopes with ever-increasing primary mirror (aperture) diameter was the order of the day. In 1908, a 60-inch Hale, followed nine years later with the construction of 100-inch Hook were the principal tools by which Hubbleand others made their observational studies. There were the central telescopes on Mt. Wilson in Southern California, and they would be among the largest telescopes on Earth until they were surpassed in 1948 by the 200-inch Hale reflector at Mt. Palomar which today barely makes the top 20 largest telescopes on the Earth list. Edwin Hubble’s work was some of the most extensive efforts in observational astronomy. By using every scientific monitoring device, special photographic imaging, special photographic emulsions by Eastman Kodak, and collaboration with colleagues, Edwin Hubble’s The Realm of the Nebulae culminates the work of many observational astronomers and brings their efforts into a crystal focus, answering questions about the basic workings of the universe in which we live.
Second, Hubble, widely regarded as the greatest observational astronomer of the 20th Century, included in his work reports on the work of his colleagues worldwide including and integrating their analyses and findings into those he was making using the best, largest telescope available at the time. His observations and his systematic approach to the analysis of the data he received from his viewing of the cosmos led to his discovery that the universe was expanding and had been doing so since the beginning of everything. In fact, if anything, the expansion was increasing at a steady rate moving large “island universes” (the term of others not Hubble’s) away from each other and our galaxy at a steadily increasing pace. The basic realization that Hubble documented was the consistent change in the way certain chemical element wavelength spectrographs would change from one object to another which were determined to be at different distances from the points of observation here on Earth.
Writing at the height of the Great Depression, Hubble carried on his research and reading, observing and mapping, graphing, reading reports of others, and bringing all of these factors together in a unique, seminal way using the laws of general relativity and the Doppler effect associated with the elemental spectrographic results to point to clearly shifted measurements for the same types of chemicals for diverse sources, all of which measured a set of data that consistently came together across most if not all observations across the planet. It was clearly a unique finding and one which answered one of the most important cosmological question – what is the nature of the universe? Collapsing, closed and fixed, or expanding? The preponderance of the data clearly indicated that expanding was what the answer was consistently showing across observers, across the world, and regardless of what part of the sky into which they looked. Expansion was happening everywhere. This specific aspect of the universe bears Hubble’s name, just as the first orbital space telescope was named for him as well.
The Realm of the Nebulae is a scientific report. It is very technical and scientific. It has a fair number of mathematical equations, and a very extensive set of notes on almost every page for either source citations or explanations of concepts with referencing as deemed necessary or helpful for clarity purposes. The discourse is technical, but the vocabulary is not as difficult as one might expect. It is a book for astronomy and cosmology researchers, enthusiasts, and historians of science and scientific discoveries. It also provides an inferential history of the progress made with each new aperture size when new instruments came on line. Recommended to anyone interest in the elements noted immediately above. If you are among that group, this book is a full 5 out of 5 stars for its topic. It is documented elegantly and clearly, it has a detailed and paginated index, and several black and white photographic plates and numerous charts, tables, and informative pieces of interest to the audience for whom the book is intended.
This review by Richard Buro is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.
Based on a work at https://www.goodreads.com/book/show/16073259-the-realm-of-the-nebulae.
Permissions beyond the scope of this license may be available at http://yalepress.yale.edu/yupbooks/contact.asp#permissions.
May 3, 2020
nebu-ley
October 15, 2025
Written in 1936, the book has to be a classic. Hubble was the first to establish via observational evidence that there was a full celestial world beyond the Milky Way and that this world was expanding and accelerating.
The writing is on the thick side, with a lot of numbers tossed into the mix, but the main challenge I had with the book was sorting through his terminology. He seemed to be using nebula-nebulae, stellar systems, star systems, globular structures, realm of the stars, extra-galactic nebulae, and galaxies loosely, to the point that it was not clear what he was referring to. At a time when the Milky Way was thought to be the cosmos, it was not always clear what the faint and starry dust were, so some imprecise usage of terminology was understandable. Though he preferred nebulae, in the end I think Hubble went with the galaxy terminology to describe what he thought to be star systems (collections of stars) beyond the Milky Way.
Hubble describes the methodology he uses to determine the distribution of galaxies and their relative distances from Earth. This was too complicated for me to follow in any meaningful way and it’s for others to comment on the validity of Hubble’s methodology that leads him to conclude that these collections of stars are red shifted and, thus, generally moving away from the Milky Way at ever increasing speeds. But one question continually crops up in third-party accounts of Hubble’s finding in this regard. Galactic structures are swirling around a globular center, and light from one side is moving away from the earth’s vantage point whereas the other side is moving toward the earth. Which direction is being measured to determine red versus blue shift? As vast galactic structures are undifferentiated collections of light the closer one gets to the galactic center, Hubble seems to take his sample from the disks where he can see a distinct star in making his determination of whether it is red or blue shifted, but it is in the swirling arms where the red versus blue shift would be the greatest. While he acknowledges that there is this light differential “from the nebula” (“One end is receding and the other end is approaching, with respect to the nucleus.”) in Plate VII, he does not elaborate why this doesn’t compromise his methodology. I suppose Hubble could look at the central cluster to determine whether that light as a whole was moving toward or away from his vantage point, but I can’t say that this is what he does.
My main interest in this book is in Hubble’s descriptive scheme for the evolution of galactic structures. He nicely lays it out in Figure 1 (page 45) which is by now, 90 years later, the still-definitive description of galactic types, though not necessarily on their evolution, and this is where I think a serious revisiting of Hubble’s findings is warranted, especially on his evolutionary sequence of galactic structures. In Hubble’s most basic division, he categorizes 95 percent of the galaxies as normal, with 5 percent being irregular. Hubble then focuses on the normal galaxies. For him, in their primordial form, normal galaxies are first elliptical, i.e. they are compact structures at the center without disks or spirals on their edges, and this is where the oldest stars lie. Then they split into two forms, spiral and barred, with the last category of elliptical galaxies (E7) having characteristics of barred galaxies*. These galaxies in turn have their own evolutionary variations (Sa to Sc for spirals; SBa to SBc for barred) - that increasingly thin out regarding their nuclear and spiral densities. Hubble’s scheme is, in short, that galaxies begin as gravitational centers that rotate outward via the disks.**
According to the introduction to this book, Hubble was known for sticking close to observational evidence, taking little risk in engaging in theoretical speculations. Is this a significant shortcoming to his book? Galactic structures are the most abundant and striking phenomena in the cosmos, yet Hubble and others are overly sparing in their attempts to account for their presence and operation, even when some very basic questions are posed. For example, and most significantly, it is not clear whether the disks are spiraling outward or inward (as movement toward a gravitational center), or whether the spiraling is orbiting or something else.
When I asked AI to answer whether the spiral arms are moving outward or inward, AI says this is not an appropriate question to ask because galaxies are orbital systems (Does this working within the existing paradigm of standard answers show a flaw in AI?). The books on galaxies, and even Hubble in this book, use the word orbiting to describe the rotation around a galactic nucleus. It is a loosely applied term. That there is movement around a galactic center is clear enough, but is it orbital when the arms so clearly morph into the galactic center (unlike the planet and sun in our solar system where orbits are distinct balance points between inertial straight-line movement in the presence of gravitational curvature)? Most photos - not drawings and depictions - of galaxies show a definite connection of the arms (spiral or barred) to the nuclear cluster at the galactic center, and even Hubble (see quote in the second footnote plus his well-cited Figure 1 diagram) sees this connection.
Then there is Einstein whose theory of gravity never gets pulled into the discussion on galactic structure. Einstein said that gravity is not a force. Rather, gravity is the weighty center of mass toward which spacetime (and the stuff within it, like stars, planets, objects, gas and dust) flows by virtue of its own inertial properties per Newton’s first law of motion. Could it be that what we’re seeing with galactic structures is Einstein’s theory in, so to say, real time? Are we seeing the movement of space-time and the stuff within it into the galactic nucleus? Are the black holes thought to be at the center of “most” galaxies cut off from what’s going around them, or are they the large bodies of gravitational mass toward which all matter and energy flows and, after passing the event horizon, disappears into the singularity?
Playing this Einstein angle out a bit, and applying it to Hubble’s schema, what if we were to flip Hubble’s scenario for the evolutionary sequence of galaxies? Now the sequence begins at the outside, the irregular gas and dust. In the presence of a large gravitational mass, unformed gas and dust become disks that are shaped by gravity. Disks flow into the nuclear cluster from two directions (with side spirals flowing increasingly into the main spiral arms) and, as they increasingly move to the center, the galaxies take on the barred effect that Hubble notes and, from there and in time, this barred effect disappears to form the elliptical galactic effect that Hubble notes. And, presumably, this movement toward the gravitational center continues with movement into the black hole.***
*”The transition between E7 and SBa is smooth and continuous,” but “Between E7 and SA no nebulae are definitely recognized.”
**Hubble does not use the term angular momentum, but this is what the arms seem to be doing doing vis-a-vis the nuclear center. “In the normal spiral,” he writes, “ the two arms emerge smoothly from opposite segments of the periphery of the nuclear region…and thence wind outward along spiral paths.” For the barred spirals, “the two arms spring abruptly from either end of a bar of nebulosity stretching diametrically across the nuclear region, and thence follow the spiral paths similar to those found in the normal spirals.”
***This scenario preserves Hubble’s findings that the oldest stars are in the “nebula cluster” - because the flow sequence goes from younger stars at the periphery to the older stars at the center, with the latter being the first to have been affected by the large gravitational mass at the center. I get the sense that Hubble is somewhat baffled by the large, luminous but undifferentiated galactic center, which is certainly a highlight feature of any galaxy, in part because it is an obstacle to his search for distinct stars that can tell a better story. But from the Einstein scenario, it makes perfect sense. Stars, as matter and energy, concentrate as they move toward the galactic center, with density making it impossible to differentiate individual stars. Of course, the ultimate density is the singularity thought to be at the tail end of this sequence of increased concentration. The role of the disks presents a problem when we split up a galaxy into an equatorial plain where the disks are thought to form as the stronger gravitational presence is felt at poles, not the equator which is further away from the gravitational center and where angular momentum would be more prominent. As a final note, in Hubble’s Figure 1 diagram, his Sc spiral galaxy has only one entry point to the galactic center, not two. I don’t know how that fits into Hubble’s own theory. It could be a matter of somewhat sloppy drawing?
The writing is on the thick side, with a lot of numbers tossed into the mix, but the main challenge I had with the book was sorting through his terminology. He seemed to be using nebula-nebulae, stellar systems, star systems, globular structures, realm of the stars, extra-galactic nebulae, and galaxies loosely, to the point that it was not clear what he was referring to. At a time when the Milky Way was thought to be the cosmos, it was not always clear what the faint and starry dust were, so some imprecise usage of terminology was understandable. Though he preferred nebulae, in the end I think Hubble went with the galaxy terminology to describe what he thought to be star systems (collections of stars) beyond the Milky Way.
Hubble describes the methodology he uses to determine the distribution of galaxies and their relative distances from Earth. This was too complicated for me to follow in any meaningful way and it’s for others to comment on the validity of Hubble’s methodology that leads him to conclude that these collections of stars are red shifted and, thus, generally moving away from the Milky Way at ever increasing speeds. But one question continually crops up in third-party accounts of Hubble’s finding in this regard. Galactic structures are swirling around a globular center, and light from one side is moving away from the earth’s vantage point whereas the other side is moving toward the earth. Which direction is being measured to determine red versus blue shift? As vast galactic structures are undifferentiated collections of light the closer one gets to the galactic center, Hubble seems to take his sample from the disks where he can see a distinct star in making his determination of whether it is red or blue shifted, but it is in the swirling arms where the red versus blue shift would be the greatest. While he acknowledges that there is this light differential “from the nebula” (“One end is receding and the other end is approaching, with respect to the nucleus.”) in Plate VII, he does not elaborate why this doesn’t compromise his methodology. I suppose Hubble could look at the central cluster to determine whether that light as a whole was moving toward or away from his vantage point, but I can’t say that this is what he does.
My main interest in this book is in Hubble’s descriptive scheme for the evolution of galactic structures. He nicely lays it out in Figure 1 (page 45) which is by now, 90 years later, the still-definitive description of galactic types, though not necessarily on their evolution, and this is where I think a serious revisiting of Hubble’s findings is warranted, especially on his evolutionary sequence of galactic structures. In Hubble’s most basic division, he categorizes 95 percent of the galaxies as normal, with 5 percent being irregular. Hubble then focuses on the normal galaxies. For him, in their primordial form, normal galaxies are first elliptical, i.e. they are compact structures at the center without disks or spirals on their edges, and this is where the oldest stars lie. Then they split into two forms, spiral and barred, with the last category of elliptical galaxies (E7) having characteristics of barred galaxies*. These galaxies in turn have their own evolutionary variations (Sa to Sc for spirals; SBa to SBc for barred) - that increasingly thin out regarding their nuclear and spiral densities. Hubble’s scheme is, in short, that galaxies begin as gravitational centers that rotate outward via the disks.**
According to the introduction to this book, Hubble was known for sticking close to observational evidence, taking little risk in engaging in theoretical speculations. Is this a significant shortcoming to his book? Galactic structures are the most abundant and striking phenomena in the cosmos, yet Hubble and others are overly sparing in their attempts to account for their presence and operation, even when some very basic questions are posed. For example, and most significantly, it is not clear whether the disks are spiraling outward or inward (as movement toward a gravitational center), or whether the spiraling is orbiting or something else.
When I asked AI to answer whether the spiral arms are moving outward or inward, AI says this is not an appropriate question to ask because galaxies are orbital systems (Does this working within the existing paradigm of standard answers show a flaw in AI?). The books on galaxies, and even Hubble in this book, use the word orbiting to describe the rotation around a galactic nucleus. It is a loosely applied term. That there is movement around a galactic center is clear enough, but is it orbital when the arms so clearly morph into the galactic center (unlike the planet and sun in our solar system where orbits are distinct balance points between inertial straight-line movement in the presence of gravitational curvature)? Most photos - not drawings and depictions - of galaxies show a definite connection of the arms (spiral or barred) to the nuclear cluster at the galactic center, and even Hubble (see quote in the second footnote plus his well-cited Figure 1 diagram) sees this connection.
Then there is Einstein whose theory of gravity never gets pulled into the discussion on galactic structure. Einstein said that gravity is not a force. Rather, gravity is the weighty center of mass toward which spacetime (and the stuff within it, like stars, planets, objects, gas and dust) flows by virtue of its own inertial properties per Newton’s first law of motion. Could it be that what we’re seeing with galactic structures is Einstein’s theory in, so to say, real time? Are we seeing the movement of space-time and the stuff within it into the galactic nucleus? Are the black holes thought to be at the center of “most” galaxies cut off from what’s going around them, or are they the large bodies of gravitational mass toward which all matter and energy flows and, after passing the event horizon, disappears into the singularity?
Playing this Einstein angle out a bit, and applying it to Hubble’s schema, what if we were to flip Hubble’s scenario for the evolutionary sequence of galaxies? Now the sequence begins at the outside, the irregular gas and dust. In the presence of a large gravitational mass, unformed gas and dust become disks that are shaped by gravity. Disks flow into the nuclear cluster from two directions (with side spirals flowing increasingly into the main spiral arms) and, as they increasingly move to the center, the galaxies take on the barred effect that Hubble notes and, from there and in time, this barred effect disappears to form the elliptical galactic effect that Hubble notes. And, presumably, this movement toward the gravitational center continues with movement into the black hole.***
*”The transition between E7 and SBa is smooth and continuous,” but “Between E7 and SA no nebulae are definitely recognized.”
**Hubble does not use the term angular momentum, but this is what the arms seem to be doing doing vis-a-vis the nuclear center. “In the normal spiral,” he writes, “ the two arms emerge smoothly from opposite segments of the periphery of the nuclear region…and thence wind outward along spiral paths.” For the barred spirals, “the two arms spring abruptly from either end of a bar of nebulosity stretching diametrically across the nuclear region, and thence follow the spiral paths similar to those found in the normal spirals.”
***This scenario preserves Hubble’s findings that the oldest stars are in the “nebula cluster” - because the flow sequence goes from younger stars at the periphery to the older stars at the center, with the latter being the first to have been affected by the large gravitational mass at the center. I get the sense that Hubble is somewhat baffled by the large, luminous but undifferentiated galactic center, which is certainly a highlight feature of any galaxy, in part because it is an obstacle to his search for distinct stars that can tell a better story. But from the Einstein scenario, it makes perfect sense. Stars, as matter and energy, concentrate as they move toward the galactic center, with density making it impossible to differentiate individual stars. Of course, the ultimate density is the singularity thought to be at the tail end of this sequence of increased concentration. The role of the disks presents a problem when we split up a galaxy into an equatorial plain where the disks are thought to form as the stronger gravitational presence is felt at poles, not the equator which is further away from the gravitational center and where angular momentum would be more prominent. As a final note, in Hubble’s Figure 1 diagram, his Sc spiral galaxy has only one entry point to the galactic center, not two. I don’t know how that fits into Hubble’s own theory. It could be a matter of somewhat sloppy drawing?
July 1, 2022
Interesting to see how space photography and information has changed since the early 1900s. Truly worth taking the time to look back and see the past's progress.
August 2, 2016
Fantastic book if you're curious about how scientists from this era did their work. Edwin Hubble was able to take an extremely complex subject and scale it down to be easier to digest for readers who may be less familiar with the science that was examined in the book.
The book is quite math heavy, so be prepared to think about numbers a whole lot!
The book is quite math heavy, so be prepared to think about numbers a whole lot!
Want to read
March 27, 2011I haven't read this book yet! I accidentally gave it a star rating on my ipod (clumsy fat fingers), this book may well be worthy of 4 stars however please ignore my rating for now!
This entire review has been hidden because of spoilers.
Read
February 18, 2014Used for citation
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