Introduction to the Exploration of the Universe

1
Introduction to the Exploration of the Universe

• Our picture of the Universe
• Scientific theories
• Going to extremes
• Frontiers and edges of science
• Counting in powers of 10
• Crazy ideas
• An expensive research

2
Our Picture of the Universe

• Old and new questions about the Universe
• Where did it come from and where is it going ?
• What is the nature of time ?
• Answers from astronomy, physics, cosmology

3
Early Answers

• Archaeoastronomy has dealt with practical things
  such as
• keeping time,
• marking the arrival of seasons,
• predicting eclipses of the Moon and the Sun.
• Stonehenge (2700 B.C.), Chichen Itza, Chaco
  Canyon
• Constellations were recorded by the Sumerians,
  Greeks, Chinese, Babylonian and Egyptians
• Earth at the Center - Aristotle (On the Heavens
  340 B.C.), Ptolemy (140 A.D.)
• Round-shaped Earth - Pythagoras
• the size of Earth Erathosthenes
  (size given in
  stadia 1 stadium160m)

4
Cyclic Cosmologies

• Almost all religions deal only with the creation
  of the Universe similarities related to the
  study of constellations (see Zeitgeist on the
  Web)
• Hindu cosmology is unique in its presentation of
  a cyclic evolution of the Universe (cycles inside
  cycles). For instance one cycle would correspond
  to a day and a night in the life of Brahma, equal
  to 8.6 billions of years. A higher level cycle is
  a year in Brahmas life, equal to 3.1 trillion
  years.
• Cyclical cosmology was also proposed by
  Heraclitus of Ephesus around 500 B.C.

5
Modern Science

• Sun at the Center Copernicus(1514), Tycho Brahe,
  Giordano Bruno.
• Modern astronomy
• Galileo (1609)
• Keplers laws(1609-1618)
• Newtons laws (Philosophiae Naturalis Principia
  Mathematica 1687).
• Infinite static Universe - H.Olbers (1823)
  paradox
• Expanding Universe (Big Bang) E.Hubble(1929)

6
21st Century Science

• Superstrings and M-Theory
• Many dimensions
• Parallel Universes
• Where does the Universe come from ?
• Science more exciting than Science Fiction !

7
Non-scientific Answers

• Answers provided by religions, astrology etc are
  easier to understand. Only 5 of the population
  in NA, UK and Japan can read articles on science
  for laymen.
• For a long time science provided very few answers
  to the big questions about the Universe.
• Different roles for Science and Religion.
  Human belief is not based on science and logic
  but on what makes us feel good to believe
  W.James 1890.

8
Scientific Theories

• Definition A scientific theory is a model of
  the Universe or of a part of the Universe which
• accurately describes a large class of
  observations
• makes predictions about the results of future
  observations.
• Any physical theory is provisional, in the sense
  that it is only a hypothesis (K.Popper).
  Experiments prove it or disprove it.
• The ultimate goal of science is a single theory
  for the Universe, but today we still break the
  problem into parts and find partial theories
  quantum theory and general relativity.

9
Frontiers and Edges of Science

• The frontier in science is the boundary of
  current knowledge in the respective science.
  One can speak about frontiers
  in every area of research.
• The edge in science is different from a frontier
  in the sense that a theory on the edge is not a
  full scientific theory as it isnt backed by
  experiment. As you will see
  later in this course, some ideas about the origin
  of the Universe or about parallel universes
  qualify as theories on the edge. This situation
  might change in the future and these edges might
  become frontiers of science.

10
Counting in Powers of 10

• Q How many atoms in the Universe ?
• A Easy to give an approximation
• - Atoms in a gram 1024
• - Grams in a star 1033
• - Stars in a galaxy 1011
• - Galaxies in the Universe 1010
• Total atoms
  1078
• Note the multiplication of the powers of 10 is
  done by adding the exponents

11
Distances in the Universe (in 10N centimeters)
N
28
Radius of the observable Universe (over 1028)
24
Distance to the nearest galaxy(3x1024)
20
Distance to the nearest star (4x1018)
16
Distance to the Sun (1014)
12
Diameter of Earth (1010)
8
Diameter of neutron star (106)
4
Height of a human being (2x102)
0
Diameter of virus (10-4)
-4
-8
Diameter of an atom (10-8)
-12
Diameter of an atomic nucleus (10-13)
-16
12
Other Distance Units

• One light-year is the distance covered by light
  in a year.
• As the speed of light is 300,000 km/sec, 1
  light-year is equal to the speed of light times
  the number of seconds in a year, or about 1018cm.
  
• The nearest star to our Sun is Proxima Centauri
  at about 4.2 light-years
• The distance Earth-Sun is 8.3 light-minutes
• Earth-Moon is 1.3 light-seconds.
• One atomic unit (a.u.) is the radius of the
  hydrogen atom in its ground state, which about
  10-8 cm.

13
Weights in the Universe (in 10N grams)
N
44
Mass of a galaxy (1044)
36
28
Mass of Sun (1032)
20
Mass of a mountain (1016)
12
Mass of a human being (105)
4
-4
-12
Mass of a heavy atom (10-21)
-20
Mass of electron (10-25)
-28
14
Crazy Ideas

• Arbitration by the experimental results liberate
  thought rather than constraining it. The more
  facts the more challenge to the imagination.
• Quantum theory was probably the most imaginative
  theory, which today explains in detail the
  workings of the micro-cosmos. N. Bohrs famous
  comments in a 1958 seminar we all agree that
  your theory is crazy what divides us is whether
  it is crazy enough
• Newtons crazy idea was that the same force
  that drove an apple towards the ground, also
  steers Earth in its rotation around the Sun.

15
An Expensive Research

• Modern telescopes and particle accelerators can
  cost hundreds of millions of dollars
• This is a research which cannot be justified by
  practical applications but by the need to
  understand the most fundamental questions about
  the Universe.
• (a few years ago R.Wilson, the director of
  the Fermi laboratory, asked by a senator about
  Fermi labs contribution to the defense program,
  said this lab makes our country worth
  defending).
• International cooperations
• CERN, Fermi lab, Hubble Telescope,
  The International Space Station

16
CERN Geneva
17
Hubble Telescope