From Stars to Stalagmites (Paperback)
Paul S. Braterman (지은이)
World Scientific Publishing Co Pte Ltd
2012-04-17
정가 $37.00 / 49,240원
328쪽 | 228*154mm | English | 489g |
ISBN(13) : 9789814324977
요즘은 총체적인 과학에 관한 책들이 관심이 생긴다.
[목차]
- The Age of the Earth -- An Age-Old Question
- Atoms Old and New
- The Banker Who Lost His Head
- From Particles to Molecules, with a Note on Homoeopathy
- The Discovery of the Noble Gases -- What's so New About Neon?
- Science, War, and Morality; The Tragedy of Fritz Haber
- The Ozone Hole Story -- A Mystery with Three Suspects
- Rain Gauge, Thermometer, Calendar, Warning
- Making Metal
- In Praise of Uncertainty
- Everything is Fuzzy
- Why Things Have Shapes
- Why Grass is Green, or Why Our Blood is Red
- Why Water is Weird
- The Sun, The Earth, The Greenhouse
- In the Beginning
[사이언티픽 어메리컨 온라인 뉴스레터 January 25, 2013 자에 저자가 일부 글을 실었다.
Editor's Note: This excerpt is from the first chapter of From Stars
to Stalagmites: How Everything Connects, by Paul S. Braterman. Earlier
in the chapter the author discusses the ideas among geologists in the
19th century that physical processes such as erosion had always occurred
at the same rates and that the features of Earth were static, leading
them to conclude that the planet had had no beginning nor would it have
an end. Here he writes about how the ideas of physicist William Thomson
would end up turning those theories on their heads, paving the way for
our current understanding of Earth's early history and age.
Other developments, however, were to undermine this view. I have already
mentioned steam engines and railways. Science in the mid 19th century
was much occupied with matters concerning work and energy, and the
efficiency of heat engines. This period saw the development of a new
subject, thermodynamics, dedicated to such matters. One of the most
fundamental results of thermodynamics (the First Law) is that energy is
conserved. Another (the Second Law) is, that since energy tends to
spread out and degrade irreversibly over time, there could be no such
thing as a perpetual motion machine. Any real process, and certainly
such a process as the uplift and erosion of the Earth, is operating
against friction, with overall irreversible degradation of energy into
heat, and this is something that cannot continue on its own
indefinitely. Yet the Earth, as seen by Hutton and Lyell, appeared to be
just one such machine, running through cycles of uplift and erosion
with no visible source of energy to drive the process. Conflict between
the thermodynamicists and the geologists was inevitable.
William Thomson, Lord Kelvin, in whose honour the absolute temperature
scale is now named, was among the most distinguished scientists of the
late 19th century. His work straddled the boundary between pure and
applied research. Among other things, he played a major role in
establishing the relationships between heat, work, and electricity,
worked out the theory for how much information (as we would now say)
could be carried by the first submarine cable, and improved the form of
the compass and the methods of navigation. He was appointed Professor of
Natural Philosophy (i.e. Physics) at Glasgow University when he was 22,
and held that Chair for more than 50 years.
Kelvin was interested in the age of the Earth, considered as a problem
in physics, from a very early stage. It was the subject of a prize
undergraduate essay, and also of his inaugural lecture at Glasgow, now
unfortunately lost. He was also a sharp critic of the science of geology
as it was developing. He argued (correctly) that extreme
uniformitarianism was not compatible with the laws of physics. Things
must have been very different at some time in the past, and would be
different again in the future. The Earth was losing heat and must have
once been a molten ball. The Sun was emitting energy, could not have
been there forever, and must eventually run out of energy, plunging the
Earth into utter cold and darkness.
In a lengthy series of publications, Kelvin attempted to quantify these
general objections. He developed a way of estimating the age of the
Earth’s solid crust from cooling arguments. It is hot down a mine, and
the deeper you go, the hotter. If you could go down deep enough, you
would, at a depth of some miles, reach the Earth’s mantle, where the
rock is actually molten. So if we have cooler rocks on top and hotter
rocks lower down, heat must be flowing up through the rocks from the
centre outwards. Knowing how fast the temperature increases as we go
down, and how effectively the rocks of the crust conduct heat, Kelvin
calculated how fast the Earth was losing heat. Where was this heat
coming from? Kelvin thought he had the answer. He assumed (correctly)
that the Earth was originally molten, and that heat must have dissipated
as the Earth’s rocks solidified from an originally molten state (the
opposite kind of process to ice absorbing heat as it melts). From an
estimate of the thickness of the solid rock layer (the crust), and from
measurements of how much heat it takes to melt a given amount of rock,
he was able to estimate how much heat has been given out by this process
of solidification. Then, by running the model backwards through time,
he calculated that the thickness of the Earth’s solid crust corresponded
to 100 million years. At this date before the present, all the rocks
now on the surface would have been molten, and this, according to his
argument, is therefore an absolute upper limit on the age of the solid
crust of the Earth.
Throughout the 19th century, unaware of this approaching crisis,
geologists worked away at establishing our familiar geological column.
They worked out the order of the strata from which lay on top of which
others, and later from the complexity of the fossils they contained, and
made estimates of the duration of each geological period from the
thicknesses of its best preserved sediments. Not realising that they had
only a very incomplete part of the total depositional record, they came
up with an estimated age of around 100 million years upwards, in
tolerable agreement with Kelvin.
The age of the Sun presented a much more serious problem. We know how
large the Sun is, how far away, and how much solar energy reaches us.
From this, it is relatively straightforward to calculate its total
energy output. Where is this energy coming from? Not from any chemical
process, for no chemical process is energetic enough. So Kelvin,
building on suggestions by Helmholtz and others, suggested that a more
useful source might be the gravitational energy released during the
Sun’s formation. Knowing the total mass of the Sun, and using Newton’s
Laws of gravitational attraction, Kelvin could work out how much energy
must have been given out by this process. This would first be converted
into the kinetic energy of the infalling matter, and that kinetic energy
would then by well-known physical processes be converted to heat and
ultimately to light, all in strict obedience to the laws of
thermodynamics. Divide the amount of energy available by the rate of
output, and you get an upper probable limit of 100 million years for the
Sun’s total productive life. This is also, by implication, an upper
limit to the age of the Earth as we know it. "As for the future, we may
say, with equal certainty, that inhabitants of the Earth can not
continue to enjoy the light and heat essential to their life for many
million years longer unless sources now unknown to us are prepared in
the great storehouse of creation." Kelvin wrote these words in 1862, and
published them in a popular journal (Macmillan’s Magazine).
In subsequent refinements of this calculation, he would add further
arguments, based for example on tidal friction and the dynamics of the
Earth–Moon system, and in the light of fresh information about the
thermal properties of rocks lower the range to some 20–40 million years,
"and probably much nearer 20 than 40."
The impact was sensational. For by this time, as Kelvin well knew, a
great deal was at stake. Darwin’s Origin of Species had appeared just
three years before the Macmillan’s Magazine article. This had
revolutionised our perspective on the world. It stated for the first
time with complete clarity the modern view that species were not
separately created but had evolved from simpler common ancestors by the
operation of natural selection on the variations between individuals.
The origin of these variations (what we now call mutations) was
completely unknown, but it was clear that descent from a common ancestor
must have been an extremely slow process, requiring what Darwin himself
had described as "incomprehensibly vast… periods of time", with 20 to
40 million years much too little for all this to have occurred by
natural selection. Nor did it help when Kelvin revised his 100 million
year estimate of the age of the Earth sharply downwards, in the light of
new evidence about the melting points of rocks. Indeed, Charles Darwin
referred to Kelvin as an "odious spectre" and among his sorest troubles,
and his son George was among the geologists most concerned with trying
to find flaws in Kelvin’s reasoning.
Reprinted from From Stars to Stalagmites: How Everything Connects, by Paul S. Braterman, with permission from World Scientific Publishing (U.K.), Ltd. Copyright © Paul S. Braterman, 2012.
