Seven Brief Lessons on Physics (6 page)
Read Seven Brief Lessons on Physics Online
Authors: Carlo Rovelli
We are a species that is naturally moved by curiosity, the only one left of a group of species (the genus
Homo
) made up of a dozen equally curious species. The other species in the group have already become extinct—some, like the Neanderthals, quite recently, roughly thirty thousand years ago. It is a group of species that evolved in Africa, akin to the hierarchical and quarrelsome chimpanzees—and even more closely akin to the bonobos, the small, peaceful, cheerfully egalitarian, and promiscuous type of chimps. A group of species that repeatedly went out of Africa in order to explore new worlds, and went far: as far, eventually, as Patagonia—and as far, eventually, as the moon.
It is not against nature to be curious: it is in our nature to be so.
One hundred thousand years ago our species left Africa, compelled perhaps by precisely this curiosity, learning to look ever farther afield. Flying over Africa by night, I wondered if one of these distant ancestors setting out toward the wide-open spaces of the North could have looked up into the sky and imagined a distant descendant flying up there, pondering on the nature of things, and still driven by his very same curiosity.
I believe that our species will not last long. It does
not seem to be made of the stuff that has allowed the turtle, for example, to continue to exist more or less unchanged for hundreds of millions of years, for hundreds of times longer, that is, than we have even been in existence. We belong to a short-lived genus of species. All of our cousins are already extinct. What’s more, we do damage. The brutal climate and environmental changes that we have triggered are unlikely to spare us. For Earth they may turn out to be a small irrelevant blip, but I do not think that we will outlast them unscathed—especially since public and political opinion prefers to ignore the dangers that we are running, hiding our heads in the sand. We are perhaps the only species on Earth to be conscious of the inevitability of our individual mortality. I fear that soon we shall also have to become the only species that will knowingly watch the coming of its own collective demise, or at least the demise of its civilization.
As we know more or less well how to deal with our individual mortality, so we will deal with the collapse of our civilization. It is not so different. And it’s certainly not the first time that this will have happened. The Maya and Cretans, among many others, already experienced this. We are born and die as the stars are
born and die, both individually and collectively. This is our reality. Life is precious to us because it is ephemeral. And as Lucretius wrote: “our appetite for life is voracious, our thirst for life insatiable” (
De rerum natura
, bk. III, line 1084). But immersed in this nature that made us and that directs us, we are not homeless beings suspended between two worlds, parts
of
but only partly belonging
to
nature, with a longing for something else. No: we are home.
Nature is our home, and in nature we are
at
home.
This strange, multicolored, and astonishing world that we explore—where space is granular, time does not exist, and things are nowhere—is not something that estranges us from our true selves, for this is only what our natural curiosity reveals to us about the place of our dwelling. About the stuff of which we ourselves are made. We are made of the same stardust of which all things are made, and when we are immersed in suffering or when we are experiencing intense joy, we are being nothing other than what we can’t help but be: a part of our world.
Lucretius expresses this, wonderfully:
. . . we are all born from the same celestial seed;
all of us have the same father,
from which the earth, the mother who feeds us,
receives clear drops of rain,
producing from them bright wheat
and lush trees,
and the human race,
and the species of beasts,
offering up the foods with which all bodies are nourished,
to lead a sweet life
and generate offspring . . .
(
De rerum natura
, bk. II, lines 991–97)
It is part of our nature to love and to be honest. It is part of our nature to long to know more and to continue to learn. Our knowledge of the world continues to grow.
There are frontiers where we are learning, and our
desire for knowledge burns. They are in the most minute reaches of the fabric of space, at the origins of the cosmos, in the nature of time, in the phenomenon of black holes, and in the workings of our own thought processes. Here, on the edge of what we know, in contact with the ocean of the unknown, shines the mystery and the beauty of the world. And it’s
breathtaking.
The page numbers in this index refer to the printed version of this book. The link provided will take you to the beginning of that print page. You may need to scroll forward from that location to find the corresponding reference on your e-reader.
Anaximander,
24
Annalen der Physik,
4
Aristotle,
25
On the Heavens
,
26
Besso, Michele,
60
“Big Bounce,”
48
and loop quantum gravity,
45
–48
Boltzmann, Ludwig,
51
–56
“caloric,”
51
–52
Copernicus, Nicolaus,
26
–27
cosmic background radiation,
11
cosmos,
23
–30
Darwin, Charles,
15
Dirac, Paul,
35
Earth, place in cosmos,
24
–30
Einstein, Albert,
1
,
3
–5,
21
,
23
,
60
general theory of relativity,
1
,
5
,
6
–12,
13
,
39
–40,
42
and quantum mechanics,
18
–20
special theory of relativity,
4
elementary particles,
31
–38
energy
as quanta,
14
Feynman, Richard,
33
friction,
52
–53
Galileo Galilei,
41
Gauss, Carl Friedrich,
8
–9
gluons,
30
–32
See also
elementary particles
gravity
black holes,
10
and dark matter,
35
gravitational fields,
7
–8,
12
,
57
–58
gravitational waves,
11
Newton’s understanding of,
6
–7,
41
quantum gravity,
40
–41
See also
loop quantum gravity
Hawking, Stephen,
63
–64
heat and thermodynamics,
51
–54,
56
,
57
–58,
62
–64
Heidegger, Martin,
60
–61
Heisenberg, Werner,
17
humans and their place in the cosmos,
65
–81
Joyce, James,
Finnegans Wake,
31
Kepler, Johannes,
41
Landau, Lev,
5
light
bending of,
9
–10
loop quantum gravity,
42
–49
Lucretius,
De rerum natura
,
79
,
80
neutrons,
31
See also
elementary particles
Parmenides,
24
–25
Pavia, University of,
3
Planck star,
45
–6
probability
in quantum mechanics,
see
quantum mechanics
See also
elementary particles
Pythagoras,
25
quantum gravity,
40
–41
quantum mechanics,
4
,
13
–21,
32
–33,
39
–40,
42
See also
loop quantum gravity; quantum gravity; Standard Model
quarks,
31
–32
See also
elementary particles
relativity
general theory of,
5
,
6
–12,
39
–40,
42
special theory of,
4
Riemann, Bernhard,
9
Riemann’s curvature (R),
9
Schelling, Friedrich,
67
space
general relativity and curvature of,
8
–10,
29
,
36
,
42
as gravitational field,
8
,
11
–12
and loop quantum gravity,
42
–43,
45
Newton’s view of,
7
–8
Spinoza, Baruch,
73
–75
Standard Model,
34
–38
SU(5) theory,
36
–37
sun, place in cosmos,
24
–27
“supersymmetric” theories,
37
Thermodynamics. S
ee
heat and thermodynamics
time
direction of (“flow”),
58
–64
and loop quantum gravity,
43
–44
and relativity,
10
Tononi, Giulio,
71
–72
universe
See also
cosmos
Zurich, University of,
4
Carlo Rovelli
, an Italian theoretical physicist, is the head of the Quantum Gravity group at the Centre de Physique Théorique of Aix-Marseille University. He is one of the founders of the loop quantum gravity theory.
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