200
R. Barrett and P. P. Delsanto
positive rays), but one must not take it too seriously. Death alone can save one
from making blunders.”
The last sentence is a free translation from the original German, which
reads: “Gegen das Böcke-Schießen hilft nur der Tod.” The literal translation
of this is: “Only death helps against the shooting of goats.” If Einstein can
so freely admit that he has shot a few goats in his life, then the rest of us
should take heart. We have all of us in our various careers no doubt shot a
goat or two, but most of us have tried to conceal it. Shooting goats (or the
commission of blunders) is a by-product of innovative thought, even with the
greatest minds in the world.
10.5 The Expanding Universe—Observational
Evidence
Huge advances in the design of telescopes and in the observational techniques
during the first decades of the twentieth century brought tremendous progress
in the study of the sky. First, the number of visible objects formerly known
as nebulae steadily increased. A nebula is a diffuse, cloud-like object. A wellknown example, which can be observed with a small telescope or powerful
binoculars, lies in the constellation of Orion, where the second “star” in the
handle of the sword is diffuse. Improved resolution of telescopes revealed that
these nebulae are actually comprised of many stars.
Next, an ongoing ancient debate on the whereabouts of these nebulae came
to an end with the realization that they are located much farther away from us
than are our surrounding stars. In fact, we now know that stars are grouped
into huge conglomerations, or galaxies, as we call them today, from the Greek
name for the Milky Way. The Milky Way, visible in our sky, is simply the
inner part of our galaxy, seen from within.
Galaxies are enormous aggregates of gravitationally bound stars. They are
classified according to their shape, but in general they resemble flat disks,
with or without a central bulge and/or spiral arms. Astronomers believe that
our galaxy, seen from outside, would look more or less like the galaxy NGC
6744, shown in Fig. 10.5.
The Milky Way is a barred spiral galaxy. Its diameter is in the order of
100,000 light years and our sun is located in the inner side of one of the
arms of the spiral at some 27,000 light years from the centre. An observer
on earth (call her Susan) looking away from the plane of the galaxy will see
few stars (See Fig. 10.6). An observer (Bob) looking towards the centre will
see many stars, as he is peering right through three-quarters of the full length
R. Barrett and P. P. Delsanto
positive rays), but one must not take it too seriously. Death alone can save one
from making blunders.”
The last sentence is a free translation from the original German, which
reads: “Gegen das Böcke-Schießen hilft nur der Tod.” The literal translation
of this is: “Only death helps against the shooting of goats.” If Einstein can
so freely admit that he has shot a few goats in his life, then the rest of us
should take heart. We have all of us in our various careers no doubt shot a
goat or two, but most of us have tried to conceal it. Shooting goats (or the
commission of blunders) is a by-product of innovative thought, even with the
greatest minds in the world.
10.5 The Expanding Universe—Observational
Evidence
Huge advances in the design of telescopes and in the observational techniques
during the first decades of the twentieth century brought tremendous progress
in the study of the sky. First, the number of visible objects formerly known
as nebulae steadily increased. A nebula is a diffuse, cloud-like object. A wellknown example, which can be observed with a small telescope or powerful
binoculars, lies in the constellation of Orion, where the second “star” in the
handle of the sword is diffuse. Improved resolution of telescopes revealed that
these nebulae are actually comprised of many stars.
Next, an ongoing ancient debate on the whereabouts of these nebulae came
to an end with the realization that they are located much farther away from us
than are our surrounding stars. In fact, we now know that stars are grouped
into huge conglomerations, or galaxies, as we call them today, from the Greek
name for the Milky Way. The Milky Way, visible in our sky, is simply the
inner part of our galaxy, seen from within.
Galaxies are enormous aggregates of gravitationally bound stars. They are
classified according to their shape, but in general they resemble flat disks,
with or without a central bulge and/or spiral arms. Astronomers believe that
our galaxy, seen from outside, would look more or less like the galaxy NGC
6744, shown in Fig. 10.5.
The Milky Way is a barred spiral galaxy. Its diameter is in the order of
100,000 light years and our sun is located in the inner side of one of the
arms of the spiral at some 27,000 light years from the centre. An observer
on earth (call her Susan) looking away from the plane of the galaxy will see
few stars (See Fig. 10.6). An observer (Bob) looking towards the centre will
see many stars, as he is peering right through three-quarters of the full length