رحلة في تاريخ المجرات

by Leila Belkora

إن هذا الكتاب يدور حول اكتشافنا (كبشر) أننا نعيش في مجرة، وفي الواقع في كون مليء بالمجرات وتحكي هذه الرواية المثيرة حول اكتشافنا لمجرتنا، ولغيرها من المجرات، من خلال سير حياة سبعة من علماء الفلك هم: توماس رايت، ووليم هيرشيل، وويلهم ستروف، ووليم هوغينز، وجاكوبس كابتاين، وهارلو شابلي، وأدوين هبل، فقد ساهم كل من هؤلاء بشكل كبير في بلورة فهمنا الحالي للموقع الذي نحتله كبشر في الكون العظيم: الكوسموس.

ومن خلال علم هؤلاء السبعة وقصص حياتهم -وكل منهم تأثرت حياته بعائلته وأصدقائه ومعاصريه- نتتبع هذه القصة المدهشة للاكتشاف من أواسط سنوات الـ1700، مع توماس رايت إلى أواسط القرن العشرين مع أسماء نعرفها أكثر مثل شابلي وهبل: وكل شخصية من هؤلاء قربتنا أكثر لتفهمنا الحالي للكون.

"إن هذا الكتاب ممتاز. وهو يعالج المادة العلمية بطريقة غير عادية، وقد تعلمت منه الكثير!! والنتيجة هي صورة واضحة وموثقة حول الطريقة التي تم من خلالها تطوير معرفتنا بمجرة درب التبانة، وليس لدي أي تردد في التوصية بهذا الكتاب".

باتريك مور

Genres: Science, Astronomy, Physics, Nonfiction

483 pages

First published November 1, 2002

Reviews

[Sajith Kumar · Rating 3 out of 5]

Anyone looking up at a very dark night sky would fail to be mesmerized by the panoply of the celestial sheet of stars adorning, as it seems, the roof of the sky. Stars have been providing unending inspiration to many young ones to identify their future career in science. Most people are aware of what stars are, how they form and die, why they are being at their present locations and take for granted the painstaking research and study that went behind our present knowledge of the stellar systems. Leila Belkora puts up a brilliant effort to narrate the history of our understanding of the Milky Way, our parent galaxy. Ask any school student and he will answer that we belong to the Milky Way, but we must read this book to understand the story of the quest that finally culminated in getting us to the point where we are now. The book does not merely describe the discoveries as such, but proceeds to make the reader conversant with the socio-political background and the personal lives of the astronomers who made the breakthrough. The book is so structured and lucid as to make it readable like a work of fiction. And the author is a renowned scholar, dividing her time between science writing and teaching astronomy at the University of Colorado, Boulder.

It is said that every well begun job is half done. Belkora does a wonderful job in laying out the preliminaries with a good introduction and a thorough discourse on the general concepts of astronomy and its history – how the pieces nicely fell in to the pattern. The narrative is concise and the economy of words gives it added significance as a prelude to the subject matter. The author answers a recurring question in the minds of students of astronomy, that of why many of the stars possess Arabic sounding names. The answer is curious to know. First work on naming and categorization of stars based on the luminosity was taken up by Hipparchus of Greece in second century BCE. This was compiled and published by Ptolemy of Alexandria as ‘Almagest’. However, great tribulations were taking place in the near east during the first few centuries of Common Era. Then came the onset of dark ages and learning took a back seat. The mantle of scientific enquiry shifted to Baghdad which held it high for nearly four centuries. A renowned astronomer, al Sufi published a treatise in Arabic around 900 CE which was translated to many European languages in the Middle Ages and found their entry into modern lore.

Europe continued to hold on to the concepts originated by Ptolemy and Hipparchus even during the times of Newton. The suns, stars and planets were thought to be moving along three-dimensional, concentric spheres around the Earth. The celestial spheres were thought to be put in motion by God. The first stirring in the right direction was taken by Thomas Wright in the 18th century. Even though a theologian and philosopher, Wright first suggested that the Milky Way is seen as a stream because we might be looking at it edge on. Wright published his observations and results, but didn’t gain much credence due to his metaphysical and religious arguments that crept into the subject matter. But his ideas were noted by William Herschel, A German by birth, but naturalized in England. Herschel, working with his siblings, was instrumental in discovering a new planet, Uranus. This discovery was the first of a planet since recorded history. A musician-turned–astronomer, his fame lay in building optical telescopes himself and using them to estimate the distances at which stars are separated from us. A consensus had dawned among the astronomers that the huge distances of stars could be measured by accurately finding the parallax of stars – the apparent shifting in position of a star caused by the Earth’s movement around the sun and taken at diametrically opposite points in the orbit, say in June and December and situated 300 million km apart. Unfortunately, Herschel’s results were in error.

In any field of study it is not unusual for an idea to get stagnated for a while for want of instruments of sufficiently advanced technology to verify its predictions. Belkora establishes that this was true in the case of measuring stellar parallax also. It fell to the lot of Wilhelm Struve and William Huggins to compile these figures of a vast numbers of stars. At the same time, the author identifies the transition that was taking place in astronomy in early 20th century. Up to that period, Europe led the field in the form of excellent observatories equipped with instruments that were in league of the world’s largest. Americans didn’t even have a decent telescope till the 1830s, as exemplified in the lament of John Quincy Adams, President of the US at that time. But with the immense progress that was lifting America from the clutches of primitive technology, lots of new observatories began to spring up across university towns and some of them rivaled competing installations anywhere in the world. Harlow Shapley was a senior figure among the American astronomers.

Belkora implies that the confirmative evidence of the structure of the universe came with the work of Edwin Hubble, who is also the most famous astronomer of the last century and known eponymously with the space telescope that is still working wonders in a Near Earth orbit. Till Hubble’s time, the scientific community was divided on the question of whether the Milky Way was the only galaxy or it was only one among millions. The three-dimensional space is viewed through the two-dimensional sky and distances to various stars could be deduced only through ingenious schemes. Hubble established that the immense distances which separate us from some of the observed stars imply that they are too far away from the regions bounded by our own galaxy. But one of his other observations caused a paradigm shift on the theories on the origin of the universe. Hubble saw that galaxies are receding away from us. The more distant they are, the faster they are moving apart. This means that the universe as a whole was expanding. And it also suggested that there was a time when the expansion began from a point in space-time, euphemistically called the ‘Primordial Atom’. See how quickly Hubble’s discovery paved the way for concepts of Big Bang to take the centre stage.

Belkora attempts to teach even the most ignorant reader some of the fundamentals of astronomy. The collection of finely illustrated diagrams and the richly detailed colour and monochrome plates prove their assertion. She does not resort to go after a difficult argument without introducing it at a prior occasion, so that the readers would be in sync with their ideas. The books became endearing to all classes of people precisely because of the apparent effort taken by the author to clear up doubts on fundamentals.

The book’s subtitle says that it is a story of our discovery of the Milky Way. But this description would be a case of underestimating the utility of the book. Belkora not just stops at the Milky Way, the attempt continues forward to cover the entire history of astronomy for two centuries beginning from the 1730s. Readers should not get confused by the humility of the subtitle, the book’s scope far outgrows our own galaxy.

Being a scholar of astronomy, the author presents the arguments in a well balanced way. She has visited every region of the Milky Way, like its centre, where the current consensus is that a black hole is lurking. It is rare to see such comprehensive treatment in books of astronomy. At the same time, a cautionary note is also sounded about the limited knowledge we still possess about the star system as not to mistake knowledge of the foam of a braking wave with that of the ocean.

The book is highly recommended.

[Maria · Rating 2 out of 5]

I chose to read this book because I wanted to learn more about the history of our discovery and mapping of our Milky Way galaxy.

Each chapter of the book discusses the life and contribution of a particular scientist who has contributed to our understanding of the Milky Way. But it’s so heavy on the biographical details! Probably less than half the content of the book is actually related to the Milky Way. The rest is about these scientists' life stories. It felt like too much irrelevant information, at least for my purpose in reading the book. So I didn’t enjoy the book very much and wouldn't necessarily recommend it. There are likely to be other books that tells the story of the Milky Way in a better and more engaging way.

[Skyler Peterson · Rating 2 out of 5]

I have no reason to knock this book nor give it significant praise. It gives a nice overview of some of the great Astronomers and links them together by how our view of the Cosmos changed thanks to their accomplishments. If you are an astronomer or are really interested in the history of astronomy, then this book may be of interest to you.

[Julian Onions · Rating 5 out of 5]

An interesting read on the characters behind the development of the understanding of our milky way galaxy. From Herschel to Hubble via Shapley and others. Some good detail on their lives as well as their discoveries.