The arrow of time, the sequence of changes that will slowly but inexorably lead the Universe to its death, is the very thing that created the conditions for life in the first place. It took time for the Universe to cool sufficiently after the Big Bang and for matter to form; it took time for gravity to clump the matter together to form galaxies, stars and planets, and it took time for the matter on our planet to form the complex patterns that we call life. Each of these steps took place in perfect accord with the Second Law of Thermodynamics; each is a step on the long road from order to disorder.
The arrow of time has created a bright window in the Universe’s adolescence during which life is possible, but it’s a window that won’t stay open for long. As a fraction of the lifespan of the Universe, as measured from its beginning to the evaporation of the last black hole, life as we know it is only possible for one-thousandth of a billion billion billionth, billion billion billionth, billion billion billionth of a per cent.
And that’s why, for me, the most astonishing wonder of the Universe isn’t a star or a planet or a galaxy; it isn’t a thing at all – it’s a moment in time. And that time is now.
Around 3.8 billion years ago life first emerged on Earth; two hundred thousand years ago the first humans walked the plains of Africa; two and a half thousand years ago humans believed the Sun was a god and measured its orbit with stone towers built on the top of a hill. Today, our curiosity manifests itself not as sun gods but as science, and we have observatories – almost infinitely more sophisticated than the Thirteen Towers – that can gaze deep into the Universe. We have witnessed its past and now understand a significant amount about its present. Even more remarkably, using the twin disciplines of theoretical physics and mathematics, we can calculate what the Universe will look like in the distant future and make concrete predictions about its end.
This colour image of the Earth, named the ‘Pale Blue Dot’, is a part of the first-ever portrait of the Solar System taken by NASA’s Voyager 1. The spacecraft took 60 frames which could be used to create a mosaic image of the Solar System from a distance of over four billion miles from Earth.
NASA
This seemingly insignificant image of a pale blue dot is in fact one of the most important and beautiful images ever taken, revealing our planet at a distance of over six billion kilometres away.
I believe it is only by looking out to the heavens, by continuing our exploration of the cosmos and the rules that govern it, and by allowing our curiosity free reign to wander the limitless natural world, that we can understand ourselves and our true significance within this Universe of wonders.
In 1977, a space probe called Voyager 1 was launched on a ‘grand tour’ of the Solar System. It visited the great gas giant planets Jupiter and Saturn and made wonderful discoveries before heading off into interstellar space. Thirteen years later, after its mission was almost over, Voyager turned its cameras around and took one last picture of its home. This picture (left) is known as the Pale Blue Dot. The beautiful thing, perhaps the most beautiful thing ever photographed, is the single pixel of light at its centre; because that pixel, that point, is our planet, Earth. At a distance of over six billion kilometres (3.7 billion miles) away, this is the most distant picture of our planet that has ever been taken.
The powerful and moving thing about this tiny, tiny point of light is that every living thing that we know of that has ever existed in the history of the Universe has lived out its life on that pixel, on a pale blue dot hanging against the blackness of space.
As the great astronomer Carl Sagan wrote:
‘It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly with one another, and to preserve and cherish the pale blue dot, the only home we’ve ever known.’
Just as we, and all life on Earth, stand on this tiny speck adrift in infinite space, so life in the Universe will only exist for a fleeting, dazzling instant in infinite time, because life, just like the stars, is a temporary structure on the long road from order to disorder.
But that doesn’t make us insignificant, because life is the means by which the Universe can understand itself, if only for an instant. This is what we’ve done in our brief moments on Earth: we have sent space probes to the edge of our solar system and beyond; we have built telescopes that can glimpse the oldest and most distant stars, and we have discovered and understood at least some of the natural laws that govern the cosmos. This, ultimately, is why I believe we are important. Our true significance lies in our continuing desire to understand and explore this beautiful Universe – our magnificent, beautiful, fleeting home
Our time on Earth is precious and fleeting. The most important use of this time that we can make is to ask questions about our wonderful universe, so that perhaps one day one of our descendants will truly understand the natural laws that govern our cosmos.
* * *
‘Somewhere, something incredible is waiting to be known’
—Carl Sagan, 1934–1996
* * *
© CORBIS
SEARCHABLE TERMS
The pagination of this electronic edition does not match the edition from which it was created. To locate a specific passage, please use the search feature of your e-book reader.
Entries in italics indicate photographs and images
A
Abell 2218 (cluster of galaxies) 190, 191
AD 185 (supernova) 83
Aldrin, Buzz 96 al-Haytham, Ibn 56
Alpha Centauri (star) 45, 98
Alpha Orionis (Betelgeuse) 120, 120, 121, 121, 123, 130, 130, 131, 131, 133
Altair (star) 230, 231, 231
Ampère, André-Marie 36, 37
Ampère’s Law 36
Amun-Re 17, 18
Anders, William 8
Anderson, John 120
Andromeda (M31 galaxy) 13, 25, 25, 29, 48–9, 48, 49, 52, 149, 169, 169, 170, 170, 171, 171
Apollo 8 8, 162
Apollo 11 96
Apollo 15 145
Apollo 17 156, 157, 166, 167
Arches Cluster 26–7, 26
Aristotle 38, 56
Armstrong, Neil 96, 161
arrow of time 212–13, 219, 239, 240
asteroids 134–5, 164, 165
atom:
formation of 69
stability of 181
atomic clock 209
‘atomic hypothesis’ 79
Australopithecus 47
B
Bagmati river 80–1, 80
barred spiral galaxy 28
Bell, Jocelyn 177, 180, 182
Betelgeuse (star) 120, 120, 121, 121, 123, 130, 130, 131, 131, 133
Big Bang 9, 62, 106–7
as the beginning of time 10
CMB as evidence of 66, 68, 69, 70–1
Hubble expansion as evidence of 65
inflation and 71
pre-10
raw material of human being and 11
spacetime and 65, 67
standard model 108–9
symmetry-breaking events 106
timeline of the universe and 110–11
black dwarf 129, 237, 239
black holes 24, 129, 205, 206, 235
anatomy of 196–7
detecting 12
gravity and 151
mass scales with galaxy size 238
Milky Way and 36, 148, 149, 195 quasars and 177
Sagittarius A* 26, 149, 149, 195, 195
S2 and 36
supernova and 84
Boltzmann, Ludwig 217, 219
Boomerang Nebula 231
Boreman, Frank 8
Brahe, Tycho 151
branes 10
Bunsen, Robert 98, 99
Burgess Shale, Canada 72–3, 72, 73, 75
C
Calabash Nebula 124, 124
California, gold m
ining in 126, 127
Cambrian Explosion 72–3, 75
Cape Observatory, South Africa 98
Carina Nebula 74–5, 74–5
Cassini, Giovanni 40, 164
Cassiopeia (constellation) 48, 48, 49
Cat’s Eye Nebula 125, 125
Cavafy, C.P. 10
Cepheid variables 60, 65
centrifuge 174–5
CERN, Geneva 12, 78, 79, 106
Chaco Canyon Great Houses, New Mexico 177, 177, 178–9, 178–9
Chandra X-ray observatory 83, 239
Chandrasekhar limit 181, 182
Chandrasekhar, Subrahmanyan 181
Chankillo, Peru 201–3, 201, 202, 203
Chesterton, G.K. 8
Clark, Alvan Graham 231
Clausius, Rudolf 214, 215, 217
cosmic clock 39, 40–1
Cosmic Microwave Background (CMB) 66, 69, 70–1
Cosmos (Sagan) 177
‘cosmological redshift’ 64–5
Crab Nebula 176, 176, 177, 179, 180, 180, 181, 181, 182
D
dark matter/energy 24, 65, 222, 224
dating, carbon and radioactive 27
dawn of time 46–7
Degenerate Era 234, 235
Democritus 79, 91
Deneb (star) 230, 231, 231
Descartes. René 32, 38, 58, 59, 150
Draco (constellation) 190, 191
Duillier, Nicolas Fatio de 164
‘Dwingeloo 1’ (galaxy) 13, 13
Dyson, Freeman 180–1
E
Earth 204, 205
age of 205
blue marble 166–7, 166–7
death of 230, 232, 240, 241
elements see elements
gravity and see gravity
light and see light
orbit 39, 39, 149, 202, 204–5
Eddington, Sir Arthur 188, 189, 213, 215, 219
Eduard Bohlen 234–5
Egypt, ancient 17–19, 83, 209
Einstein, Albert 10, 11, 12, 36, 43, 65, 145, 151, 185, 188, 188, 189–93, 194, 195, 213
El Tatio geysers, Chile 103, 104–5, 104, 105 Electromagnetic Induction, Faraday’s Law of 36
electromagnetism:
Big Bang and 106
force of nature 140
light as an electromagnetic wave 36, 37, 43
spectrum 59, 68, 69, 168
stability of elements and 116
stars and 122
strength of 151, 174
electron 69, 79, 101, 114, 130, 181, 194, 195, 209, 210, 222
electron degeneracy pressure 181, 194, 195
elements, chemical 79
atomic explosions and 115
construction of 113, 114
Periodic Table of 94–5
rarest of all 126–7
role in human history 114
Empedocles 38
entropy:
arrow of time and 219, 221
destiny of stars and 228
in action 216–19, 216–17, 218, 219
randomness and 215
ESA (European Space Agency) 75, 85, 135, 158
Eskimo Nebula 124, 124
Eta Carinae (star) 30, 31, 75
Euclid 38, 150
Euler, Leonhard 34
European Southern Observatory (ESO) La Silla Observatory, Chile 75, 85
evolutionary Big Bang 72–3, 75
exoplanets, how to find 88–9
extraterrestrial life 84, 175, 177
eye, emergence of the 72–3, 75
F
Faraday, Michael 36, 37
Faraday’s Law of Electromagnetic Induction 36
Fermi, Enrico 115
fermions 181, 194
Fish River Canyon, Nambia 152–3, 153, 154, 154, 166
Fornax (constellation) 54
Fraunhofer lines 99
Fraunhofer, Joseph von 98, 99
G
Gagarin, Yuri 141, 142, 143
galactic halo 27
galactic neighbourhood 24–5
galaxies 24
barred spiral 28
collisions of 169–71
dwarf 24, 25, 48
giant 24
measuring distance of 60–1
shape of our 28
spiral 25, 25, 28, 48, 49, 53, 55, 70, 169, 169
term 24
see also under individual galaxy name
Galaxy Evolution Explorer, NASA 235
Galileo 32, 38, 40, 52, 145, 209
gamma-ray burst 226, 226, 227, 227
General Theory of Relativity 11–12, 145, 151, 182, 188, 189–93, 194–5, 213
Gentilin, Guillaume 29
geoid 155, 158–9, 158, 159
Glenn, John 142
Gliese 581 (planet) 84, 89
GOCE (satellite) 158
GPS 191, 193
Grand Unified Theory 239
gravity 11–12, 138–97
centrifuge and 174–5
formation of 161
geoid 155, 158–9, 158, 159
invisible string 140, 148–9
minimising potential energy and 166
Moon and 148, 159, 160–3
mountains and surface gravity 154
neutron stars and 84, 180, 181, 182, 194, 195
Newton’s Law of Universal Gravitation 150–1, 163, 184, 185, 186, 190, 193
newtons 154, 155
paradox of 174–5
planets, effect on 174–5
sculptor 140, 146, 147, 151, 152–3
stars and planets, creator and destroyer of 141, 166
Sun’s 175
surface 154
understanding 150–1
water and 153, 156, 159, 160–3
weakness of 174–5
weight, mass and 154–5
what is? 184–5
why do all objects fall at the same ratio in gravitational
fields? 144–5, 184–5
zodiacal light and 164–5
GRB 090423 (star) 227, 229, 229
Great Rift Valley, Tanzania 46, 46, 47, 47
Greece, ancient 19, 38, 79, 83
Greenland 146, 146–7
Grisson, Gus 175
H
H D 93129A (star) 75
H E 1523-0901 (star) 27
Hawker Hunter 42–3
Helix Nebula 124, 124
Herschel 36 (star) 29–30
Herschel Space Observatory Telescope 134, 135
Herschel, Sir John 120
Herschel, William 124
Hewish, Anthony 177, 182
Higgs Boson 12, 107
Himalayas 80, 92, 92, 93, 93
Hindu religion 8, 80–1
Homo Habilis 47, 48, 48
Hooke, Robert 32, 34
Hoyle, Sir Fred 177
Hubble Telescope 25, 50–5, 51, 52, 60–1, 64–5, 71, 85, 120, 142, 176, 180, 190, 231
Hubble Ultra Deep Field 54, 54, 55, 56, 59, 227
Hubble, Edwin 52, 60, 62, 149
Hubble’s Law 60, 63, 64–5
human ancestors 47, 48, 48
Huygens, Christiaan 32, 34, 41, 209
hydrogen bomb 115, 116
hypernova 31
Hypothesis of Light (Newton) 34
I
IC 4406 (star) 124, 124 inflation 71, 106
infrared 68, 69
Infrared Telescope, UK’s (UKIRT) 227
Innes, Robert 98
Isaac Newton Telescope, La Palma, Canary Islands 12
J
Jansky, Karl 168
Johanson, Donald 47
Joule, James 214–15
Jovian clock 40–1
Jupiter 40, 41, 41, 45, 164, 165, 174
K
Karnak Temple, Luxor 17, 17, 18, 18, 19
Kathmandu, Nepal 80–1
Kepler, Johannes 19, 32, 38, 151
Kirchhoff, Gustav 98, 99
Kohoutek 4-55 (planetary nebula) 125, 125
Kolmanskop, Namibia 216–21, 216–17, 218, 219, 220
L
Lagoon Nebula 29, 29
Large Hadron Collider (LHC) 12, 78, 79, 79, 107
Leakey, Louis 47
Leakey, Mary 47
Lenard, Andrew 180–1
Lescarbault 186
Leucippus 79, 91
Lewala, Zacharias 216
LGM–1 177, 182
Liberty Bell 7 175
light 11
a star is born 29–31
as an electromagnetic wave 34, 35, 36, 37, 59, 60, 64, 68, 69, 101, 191
barrier 43
birth of the universe and 66–75
connection with past 16, 31, 44, 45, 48–9, 52, 71
‘corpuscles’ 34
cosmic clock and 39, 40–1