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Galaxies and the Cosmic Frontier
For the past twelve billion years, galaxies have governed the Universe, bringing form to the firmament, light to the void. Each one a giant system of as many as hundreds of billions of stars, the galaxies are the building blocks of the cosmos, and through new data from modern telescopes--including the Hubble Space Telescope--we are discovering dizzying new facts about how they formed, how they evolve, and what they are made of. This book acquaints readers with these facts and findings--and with what they can tell us about the lives of galaxies over cosmic time, from their emergence shortly after the Hot Big Bang to their ongoing gyrations and transmutations.
334 pages, Hardcover
First published July 31, 2003
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May 28, 2024
A lot of information is presented in this book, but there is no attempt, really, to offer a theoretical (cosmological) explanation for the main types of galactic structures (spiral, barred, elliptical, irregular). As with others, the authors work within Hubble’s 100 year old scheme that merely describes the structures observed and puts them into the right box.
Hubble’s “original tuning fork” diagram of galaxy types begins with early elliptical nebulae that split at the fork into spirals and barred spirals. But Waller and Hodge, working within the Hubble framework, reverse the evolutionary sequence by stating that the sequence moves in the opposite direction, from barred and spiral galaxies to elliptic and that galactic evolution results “mostly” from their “internal structure” and interactions between galaxies,
For their classification, the authors rely heavily on the age of stars based on their light, with older stars predominating within the bulge and younger stars predominating in the disks. They add that the spirals with the weakest bulges have the loosest spirals. Elliptic galaxies, they say, have no overall rotation or their rotation is slow, and they are brightest at their center. Spirals are less bright at their disks than at their center (brightness falls off per the inverse square law), and with differential rotation, the arms wind into a spiral pattern (trail behind in their rotation) . Irregulars are unformed, and typically are without disks or bulges. With irregulars, the authors say, gas flows inward, or outward, or that “perhaps both occur…as streaming motions.”
Einstein’s general theory of relativity is missing in this book. (Or, rather, it is negated altogether as Waller and Hodge opt for a flat cosmos that is “relentlessly Euclidian,” devoid of curvature.) With Einstein’s theory of gravity, matter-energy flows toward a gravitational center. But gravity’s flip side is inertial motion of matter-energy. So right here you have countering movements: inertial movement wants to continue its straight-line motion (self-propelled from the big bang - matter and energy’s original condition, propelled - accelerated - by an external body), and gravitational mass draws inertial movement toward the gravitational center (hence, space-time curvature performs its geometric function). When diffuse matter-energy take on structure, the end result is a relatively balanced orbital system where straight-line motion is countered by movement toward the gravitational center (with orbits reflecting a 45 degree compromise between the motions). But, when unbalanced, gravity will prevail so that all matter-energy moves ("pulled" by gravity, "pushed" by inertial motion; see also footnote 4) to the center.*
These two scenarios (orbital, movement toward the center) get conflated, and this is where any theoretical explanation for galactic formation seems to get muddled. While galaxies are often referred to as spirals by writers on this topic including, at least implicitly by the writers of this book, if one sticks to a strict Einstein formulation, the sequence might be as follows: undifferentiated irregulars in their various degrees of taking on structure; spirals follow, again in their varying degrees of structure; then barred spirals as disks intensify toward the galactic nucleus;** and finally the elliptic galaxies where the galactic center nearly completes its job by pulling in all the surrounding mass-energy (from irregulars, and spirals). What happens to the elliptic galaxies - concentrations of older and lighter (because of the concentration) stars is a next question, with black holes and their singularities figuring prominently.* * *
Despite the book’s many pages, a sense is that not a lot is known about galaxies. The descriptive material is abundant, but the explanations are short or more implied than not, and they are incomplete.
Three other points to toss in here regarding this book. If galaxies - whole bodies of stars, gas, and dust - have two rotation directions - away and toward - how is their “light,” collectively, measured to determine red and blue shifts, which is the key to the measurement of the direction of movement? Also, the authors’ last chapter goes into the “standard model” of cosmological history, positing the necessity of dark energy as the countering force of gravity. But with the inverse square law of Newton, why wouldn’t the inertial movement of matter and energy progressively become free of gravitational effects per the inverse square law?**** A third, and final point, is that the authors define force as a push-pull phenomena that creates movement. In the standard account of physics, there are just four forces that are said to explain movement: gravity, electro-magnetic, and strong, and weak nuclear force. I don’t know about the weak nuclear force, but electro-magnetic and strong nuclear forces exhibit push-pull forces. That leaves gravity out as the definition of “force,” which is thought to only have a “pulling” (attraction) effect. But if inertia is seen per Newton as a moving body that stays at rest if at rest, or in motion, then this is also the property of a gravitational body: It pushes (itself) as well as it pulls. Is this what Einstein meant, in part, by saying inertia is the flip side of gravity?
*Does the movement inward create the galactic rotation and, thus, the disk formation? As matter-energy moves toward the center, it is increasingly intensified into a smaller area, where matter-energy’s inertial straight-line motion gets converted into curvature, and curvature is what creates rotation. The direction of rotation - spin - is another curious question, with a few observers stating that this begins with matter-energy’s initial spin conditions at the quantum level, that then gets magnified as matter-energy form particles and particles then form bodies, etc.
**Another ambiguity in the description of galaxies is whether the spiral arms flow inward or outward. Under Einstein's theory, the flow is inward, and what is being seen with galactic structure formation is the theory of general relativity in real time. From the Hubble, and now Webb, photos, spirals move to just two points at the center (the axial points of rotation), with secondary arms moving into them, as gravity per inverse square law, draws them closer together. The outlier to seeing galaxy formation like this are the so-called ringed galaxies where there seems to be more of an orbiting than a self-gravitating structure.
***Does matter and energy continue to swirl across the event horizon and into their singularity (with remnant disks moving into the black holes from axial points that might explain some jet phenomena,) or does matter-energy move into the black hole from all directions which is the way inward movement is commonly diagrammed (the authors refer to “swarming” where the bulges occur).
****And wouldn’t this have something to do with the puzzling issue of why spirals seem to be bound together more tightly than by what can be determined by “luminous matter alone?” It’s not the pull of matter-energy (gravity) per se, but rather the force of inertial straight line movement toward the central point of curvature that accounts for the increasing tightness of a galactic system. In other words, it’s not just the “pulling” effect of gravity, but also the "pushing" effect of inertial movement.
Hubble’s “original tuning fork” diagram of galaxy types begins with early elliptical nebulae that split at the fork into spirals and barred spirals. But Waller and Hodge, working within the Hubble framework, reverse the evolutionary sequence by stating that the sequence moves in the opposite direction, from barred and spiral galaxies to elliptic and that galactic evolution results “mostly” from their “internal structure” and interactions between galaxies,
For their classification, the authors rely heavily on the age of stars based on their light, with older stars predominating within the bulge and younger stars predominating in the disks. They add that the spirals with the weakest bulges have the loosest spirals. Elliptic galaxies, they say, have no overall rotation or their rotation is slow, and they are brightest at their center. Spirals are less bright at their disks than at their center (brightness falls off per the inverse square law), and with differential rotation, the arms wind into a spiral pattern (trail behind in their rotation) . Irregulars are unformed, and typically are without disks or bulges. With irregulars, the authors say, gas flows inward, or outward, or that “perhaps both occur…as streaming motions.”
Einstein’s general theory of relativity is missing in this book. (Or, rather, it is negated altogether as Waller and Hodge opt for a flat cosmos that is “relentlessly Euclidian,” devoid of curvature.) With Einstein’s theory of gravity, matter-energy flows toward a gravitational center. But gravity’s flip side is inertial motion of matter-energy. So right here you have countering movements: inertial movement wants to continue its straight-line motion (self-propelled from the big bang - matter and energy’s original condition, propelled - accelerated - by an external body), and gravitational mass draws inertial movement toward the gravitational center (hence, space-time curvature performs its geometric function). When diffuse matter-energy take on structure, the end result is a relatively balanced orbital system where straight-line motion is countered by movement toward the gravitational center (with orbits reflecting a 45 degree compromise between the motions). But, when unbalanced, gravity will prevail so that all matter-energy moves ("pulled" by gravity, "pushed" by inertial motion; see also footnote 4) to the center.*
These two scenarios (orbital, movement toward the center) get conflated, and this is where any theoretical explanation for galactic formation seems to get muddled. While galaxies are often referred to as spirals by writers on this topic including, at least implicitly by the writers of this book, if one sticks to a strict Einstein formulation, the sequence might be as follows: undifferentiated irregulars in their various degrees of taking on structure; spirals follow, again in their varying degrees of structure; then barred spirals as disks intensify toward the galactic nucleus;** and finally the elliptic galaxies where the galactic center nearly completes its job by pulling in all the surrounding mass-energy (from irregulars, and spirals). What happens to the elliptic galaxies - concentrations of older and lighter (because of the concentration) stars is a next question, with black holes and their singularities figuring prominently.* * *
Despite the book’s many pages, a sense is that not a lot is known about galaxies. The descriptive material is abundant, but the explanations are short or more implied than not, and they are incomplete.
Three other points to toss in here regarding this book. If galaxies - whole bodies of stars, gas, and dust - have two rotation directions - away and toward - how is their “light,” collectively, measured to determine red and blue shifts, which is the key to the measurement of the direction of movement? Also, the authors’ last chapter goes into the “standard model” of cosmological history, positing the necessity of dark energy as the countering force of gravity. But with the inverse square law of Newton, why wouldn’t the inertial movement of matter and energy progressively become free of gravitational effects per the inverse square law?**** A third, and final point, is that the authors define force as a push-pull phenomena that creates movement. In the standard account of physics, there are just four forces that are said to explain movement: gravity, electro-magnetic, and strong, and weak nuclear force. I don’t know about the weak nuclear force, but electro-magnetic and strong nuclear forces exhibit push-pull forces. That leaves gravity out as the definition of “force,” which is thought to only have a “pulling” (attraction) effect. But if inertia is seen per Newton as a moving body that stays at rest if at rest, or in motion, then this is also the property of a gravitational body: It pushes (itself) as well as it pulls. Is this what Einstein meant, in part, by saying inertia is the flip side of gravity?
*Does the movement inward create the galactic rotation and, thus, the disk formation? As matter-energy moves toward the center, it is increasingly intensified into a smaller area, where matter-energy’s inertial straight-line motion gets converted into curvature, and curvature is what creates rotation. The direction of rotation - spin - is another curious question, with a few observers stating that this begins with matter-energy’s initial spin conditions at the quantum level, that then gets magnified as matter-energy form particles and particles then form bodies, etc.
**Another ambiguity in the description of galaxies is whether the spiral arms flow inward or outward. Under Einstein's theory, the flow is inward, and what is being seen with galactic structure formation is the theory of general relativity in real time. From the Hubble, and now Webb, photos, spirals move to just two points at the center (the axial points of rotation), with secondary arms moving into them, as gravity per inverse square law, draws them closer together. The outlier to seeing galaxy formation like this are the so-called ringed galaxies where there seems to be more of an orbiting than a self-gravitating structure.
***Does matter and energy continue to swirl across the event horizon and into their singularity (with remnant disks moving into the black holes from axial points that might explain some jet phenomena,) or does matter-energy move into the black hole from all directions which is the way inward movement is commonly diagrammed (the authors refer to “swarming” where the bulges occur).
****And wouldn’t this have something to do with the puzzling issue of why spirals seem to be bound together more tightly than by what can be determined by “luminous matter alone?” It’s not the pull of matter-energy (gravity) per se, but rather the force of inertial straight line movement toward the central point of curvature that accounts for the increasing tightness of a galactic system. In other words, it’s not just the “pulling” effect of gravity, but also the "pushing" effect of inertial movement.
May 13, 2024
A thorough breakdown of the cosmos for a lay person. It explains concepts and the history concepts in a tangible and understandable way, while not staying too surface level.
June 2, 2016
Best book I've found so far on galaxies, but a little dated (2003). Needs to be updated to include last 13 years of progress.
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