This article was downloaded by: [Universitaets und Landesbibliothek]On: 29 November 2013, At: 04:27Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office:Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK

Contemporary PhysicsPublication details, including instructions for authors and subscriptioninformation:http://www.tandfonline.com/loi/tcph20

Essay review Interesting times for astronomyB. F. DroliasPublished online: 08 Nov 2010.

To cite this article: B. F. Drolias (1997) Essay review Interesting times for astronomy, Contemporary Physics,38:3, 243-245

To link to this article: http://dx.doi.org/10.1080/001075197182414

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”)contained in the publications on our platform. However, Taylor & Francis, our agents, and ourlicensors make no representations or warranties whatsoever as to the accuracy, completeness, orsuitability for any purpose of the Content. Any opinions and views expressed in this publication arethe opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis.The accuracy of the Content should not be relied upon and should be independently verified withprimary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims,proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoevercaused arising directly or indirectly in connection with, in relation to or arising out of the use of theContent.

This article may be used for research, teaching, and private study purposes. Any substantialor systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, ordistribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use canbe found at http://www.tandfonline.com/page/terms-and-conditions

Essay review

Interesting times for astronomy

B. F. DROLIAS

Our Evolving Universe. By M ALCOLM S. LONGAIR .

Cambridge University Press, 1996 . Pp xii+ 185. £24 × 95,

$34 × 95 (hbk), ISBN 0 521 55091 2. Scope: popular survey.

Level: non-specialist.

Ancient Chinese used to curse people `to live in interesting

times’ . What is a curse for ordinary people is a blessing for

scientists, and astrophysicists have been blessed with having

lived in incredibly interesting times for most of this century.

Astrophysics has known an incredible growth over the past

hundred years, a growth which is matched by no other part

of science. Starting from astrometric and spectroscopic

observations at the end of the previous century we are now

certain about many details in the evolution of the stars, the

galaxies, and the universe itself from nearly the beginning

of time till today. A reasonable explanation for this growth

is due to the `crossroads’ feature of its subject, that borrows

and adapts results from other parts of physics (like

theoretical, nuclear, high energy physics, optics, etc.).

Another very important part in this growth was played

by the remarkable link of astrophysics with technology and

the boost in technological developments in the 20th century

has given a similar boost to astronomy and astrophysics.

Astronomy and astrophysics 100 years ago meant observa-

tions in the visible part of the electromagnetic spectrum.

Soon astronomers realized that by looking at diŒerent

wavelengths they could get diŒerent information for the

world around us so any new technological breakthrough

that allowed scientists to look at the universe at a diŒerent

wavelength brought incredible new observations, new

species of objects and eventually new and better under-

standing for diŒerent eras in the age of the Universe.

Today one can meet quite a few astronomers optimistic

(or over-optimistic) enough to believe that we are within

grasp of the most initimate details in the complete history

of the Universe. However, there are many others that

believe otherwise and nearly everybody agrees that the

Universe never ceases to amaze with each new observation,

each new result. A t this m oment of `triumph’ for

astrophysics many are the popularised books that are

produced, most of them glossy and most of them with

incredible new pictures of the newest telescopes (and many

with an aggressive language that describes not how great

the Universe is but how great the intelligence of the author

is to comprehend it).

So another book about the Universe? Malcolm Longair’ s

book `Our evolving Universe’ was made with main aim to

® ll an important gap in the popularised astrophysics

literature: that of an up-to-date hierarchical building of

the ideas related to the current paradigm concerning `life,

the Universe and everything’ .

Chapter 1 (`The Grand Design’ ) is an introductory

chapter in which sizes and time-scales of diŒerent species of

objects in the Universe are discussed. The electromagnetic

spectrum and the wavebands we use to observe the

Universe are also analysed in connection with the diŒerent

temperatures of the objects we observe. The proper analysis

of the evolving parts of the Universe starts its description at

Chapter 2 (`The birth of stars and the great cosmic cycle’ )

with the theory of stellar evolution. Since the 1930s the

main processes and chains of nuclear reactions that take

place in the Sun and stars are known. These are the

processes that burn hydrogen to helium and higher

elements and the theory that came afterwards provides us

with a very good understanding of why star luminocity and

behaviour is what is observed from the ® rst stages of their

birth when they start burning hydrogen and enter the `main

sequence’ (the largest part of the life of the star during

which the star burns its hydrogen) till the stages in which

the stars become red giants or eventually white dwarfs. In

the book the processes are discussed in detail and emphasis

is given to new results from experiments concerning the

long standing neutrino problem and also results from the

fairly new ® eld of helioseismology that studies solar

oscillations in order to obtain information about the

interior of the Sun. Not all problems have been solved in

stellar evolution today so the chapter ends with some

current problems in star formation and some simple ideas

for their eventual solution.

Chapter 3 takes the reader out of our galaxy in a quest

for the `Origin of quasars’ . This requires the introduction of

ideas from high energy astrophysics since high energy

processes are now important for the production of light in

0010-75 14/97 $12.00 Ó 1997 Taylor & Francis Ltd

D r D rolias is in the Blackett Laboratory, Imperial College, London .

Contemporary Physics, 1997 , volume 38, number 3, pages 243 ± 245

Dow

nloa

ded

by [

Uni

vers

itaet

s un

d L

ande

sbib

lioth

ek]

at 0

4:27

29

Nov

embe

r 20

13

the frequencies in which these objects are observed. In the

same chapter Ð because they are related to the processes

that power up quasars Ð the continuation of the stellar

evolution story is pursued at its ® nal stages with a

discussion of neutron stars, supernovae and black holes,

thus bringing naturally in the game the theory of general

relativity. Massive stars at their ® nal stage of their stellar

evolution explode in the most dramatic way leaving behind

them according to their mass a white dwarf, a neutron star

or a black hole. White dwarfs are stars in which the

electrons are responsible for providing the degeneracy

pressure (through the Pauli exclusion principle) that keeps

the star from collapsing further under its own gravity. In

neutron stars the density of matter is so huge that the nuclei

have been stripped of their electrons and it is the

degeneracy pressure of the nucleons that keeps the stars

from collapsing. For the case of very massive stars not even

this pressure is enough to balance the gravity of the star

and the star collapses into a singularity which we usually

call a black hole. Recent observational evidence from the

Hubble Space Telescope about the existence of black holes

is reviewed in this chapter along with a discussion about the

famous binary pulsar, the study of which provided us with

a very strong test of the general theory of relativity. The

chapter ends with the extension of black hole physics in the

way that power is produced in the centre of active galaxies

and quasars; it is usually assumed that in the centre of these

active galaxies is a super-massive black hole that eats up all

the matter around it. Thus a tremendous amount of energy

of this infall can be available to power up the activity in the

centre of these galaxies, the details of which are still under

study.

The next chapter deals with the evolution of galaxies

(`The origin of galaxies’ ). Naturally the author spends a

long time introducing the reader into the basic ideas of

cosmology by talking about the expanding Universe, dark

matter, observations that lead to measurement of the basic

cosmological parameters (such as the Hubble parameter,

the deceleration parameter, etc.). Since 1929 when Hubble’ s

observations were published it is known that the galaxies

are moving away with a rate which is proportional to the

distance from us. This is not a preferential expansion away

from us but it is assumed that due to the expansion of space

time every galaxy sees all the other galaxies moving

similarly away from it and obeying the same expansion

law. The crucial parameter that determines what will

eventually happen to this expansion (whether it will keep

on happening or whether it will grow to a halt after an

in® nite time or whether the Universe will start imploding at

some point) is the density of the Universe. Small density

means little deceleration of the expansion while larger

densities (larger than a critical density) mean that the

deceleration is large enough to start the Universe collapsing

back. For some theoretical (and sometimes also aesthetic)

reasons many scientists believe that the Universe has the

critical density. This expansion is important for the way

that galaxies are formed at the early Universe because it

will have to be included in the way diŒerent perturbations

in the mass will grow with time under the in¯ uence of

gravity. DiŒerent observations show however that the

matter that is contained in the visible parts of the galaxies is

only about 1% of the critical density, hence most of the

Universe is assumed to be composed of a matter that does

not radiate (hence the name dark matter). DiŒerent

particles have been assumed to compose dark matter: from

the most friendly baryons to exotic particles predicted by

theories of particle physics. What type of dark matter is out

there is also very important for galaxy formation since it

determines what will be formed ® rst: galaxies or clusters of

galaxies. Observations of the structure in the Universe in

diŒerent scales has shown that the favourite candidate is

the cold dark matter scenario in which dark matter is

composed of massive weakly interacting particles (WIMPS)

and this scenario implies that galaxies form ® rst and then

eventually they form clusters of galaxies.

In the ® nal chapter (`The origin of the Universe’ )

Longair talks speci® cally about current cosmological ideas

based around the Big Bang paradigm (such as in¯ ation and

nucleosynthesis) and also talks in detail about current ideas

concerning open problems occupying scientists’ minds at

the moment. The nature of the chapter demands from the

researcher quite a lot concerning the interpretation and

understanding of the observations and theories concerning

the beginning of time and the Universe, hence this chapter

includes some philosophical ideas that the author ® nds

intriguing for understanding the Universe (like the anthro-

pic principle). Naturally this is the most di� cult chapter to

understand and it may require the reader to go back to

previous chapters to remind himself of the concepts that

were described there. The book ends with a very helpful

glossary of the main terms described earlier in the book.

The level of the book is quite basic so it will be fairly easy

for a non-technical reader (with a lot of time on his hands)

to understand the basic evolutionary concepts in astro-

physics today. Som e paragraphs are quite dense in

information though, so it is quite possible that the reader

may end up completely confused after a ® rst read, or may

need to consult a more specialised and expanded text. The

language of the book is awkward sometimes and in a few

cases terms are used before their de® nition, but in most

cases words are carefully chosen and this helps the reader to

understand di� cult concepts with ease. There are some

sentences though which can be considered as quite

controversial philosophically (`The theory of relativity

was discovered in...’ ) and can serve as titles for philoso-

phical debates. In a way even these are also interesting since

they represent the views of a cosmologist about the nature

of his science.

Essay review244

Dow

nloa

ded

by [

Uni

vers

itaet

s un

d L

ande

sbib

lioth

ek]

at 0

4:27

29

Nov

embe

r 20

13

The book is an extension/rewrite of a book by the same

author called `Alice and the space telescope’ that came out in

1989. Even though the second part of this book is quite

similar to the Our evolving Universe, describing (in brief) the

main processes active in the Universe, the ® rst part is a clever

humorous and self sarcastic piece based on Lewis Caroll’ s

`Through the looking glass’ . I strongly recommend it to the

reader as an accompanying part to the `Our Evolving

Universe’ .

In general the book is very successful in showing the

whole hierarchical chain of events and concepts that govern

the evolution of objects in the Universe and even in the

cases of open problems it gives a very clear picture of

possible solutions.

We are at the moment at the most interesting part of

`problem solving’ in astrophysics: the paradigm of the

Big Bang and the expanding Universe is on a very solid

base and researchers spend most of their time solving

very complicated problems about important details of the

`master-plan’ and hence expanding the paradigm. As

usual this is not an easy and smooth process but is

complicated and full of debates and ideas that change

very rapidly. In the midst of this it is very di� cult to

write a popularised book on such a science (and if you

do it may have a very short half-life), the same way it is

di� cult (or even impossible) to write a historical analysis

that has led to the current theories and discoveries.

Longair however, has been very careful and has managed

to grasp the main key ideas of the paradigm as it has

been built by the problems solved so far hoping that this

is a way to increase the authority (and longevity) of the

book. But, as I mentioned before the Universe never

ceases to amaze us.

Essay review 245

Dow

nloa

ded

by [

Uni

vers

itaet

s un

d L

ande

sbib

lioth

ek]

at 0

4:27

29

Nov

embe

r 20

13