NETA PowerPoint® Slides
to accompany
1
The Scale of the
Cosmos: Space
and Time
prepared by
Mircea Atanasiu
Mount Royal University
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The Goals of This Chapter
• In this chapter, we will consider three important
questions about astronomy:
– Where are you and Earth in the universe?
– How does the time span of human civilization
compare with the age of the universe?
– How does science give us a way to know about
nature?
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1.2 From Solar System to Galaxy to Universe
Scientific Notation
• Scientific notation – The system of recording very
large or very small numbers by using powers of 10.
• Quick Review:
nanometre (nm) = 0.000000001 m = 10–9 m
micrometre (μm) = 0.000001 m = 10–6 m
millimetre (mm) = 0.001 m = 10–3 m
centimetre (cm) = 0.01 m = 10–2 m
kilometre (km) = 1000 m = 103 m
(mega) metres = 1 000 000 m = 106 m
(giga) metres = 1 000 000 000 m = 109 m
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1.2 From Solar System to Galaxy to Universe
Units of Measure
• Light-year (ly) – A distance that light travels in
the period of one year (light travels at
300 000 km/s).
• Astronomical unit (AU) – Average distance
from Earth to the Sun (1.5 × 108 km).
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1.2 From Solar System to Galaxy to Universe
Scale of the Universe
• Let us start with the atom.
– The nucleus of an atom is 10-billionth of a metre,
where the nucleus of the atom is 10 000 times
smaller than the atom itself.
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1.2 From Solar System to Galaxy to Universe
Scale of the Universe
• Earth – Approximately 13 000 km in diameter.
• Compare that with the diameter of the Milky
Way disk—approximately 80 000 light-years
containing over 100 billion stars.
• However, we cannot see anything beyond
13.8 billion light years ... Why?
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1.2 From Solar System to Galaxy to Universe
100 m from CERN’s Globe of
Science and Innovation
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1.2 From Solar System to Galaxy to Universe
CERN site aerial view
104 m = 10 km
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1.2 From Solar System to Galaxy to Universe
Earth
107 m = 10 million km
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1.2 From Solar System to Galaxy to Universe
Earth with the Moon
109 m = 1 billion km
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1.2 From Solar System to Galaxy to Universe
Orbits of solar system planets
1013 m = 10 trillion km
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1.2 From Solar System to Galaxy to Universe
Closest stars to our Sun
30 ly = 3 × 1017 m
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1.2 From Solar System to Galaxy to Universe
The Milky Way
105 ly = 100 000 ly = 1021 m
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1.2 From Solar System to Galaxy to Universe
Local Group of galaxies
4 × 106 ly = 4 million ly = 4 × 1022 m
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1.2 From Solar System to Galaxy to Universe
The view with a diameter of
1.7 billion ly
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1.2 From Solar System to Galaxy to Universe
Extending Discussion to Some
Basic Definitions
• Planet
– A non-luminous body in
orbit around a star, large
enough to be spherical
and to have cleared its
orbital zone of other
objects.
– We live on planet Earth,
which orbits our star, the
Sun, once a year.
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1.2 From Solar System to Galaxy to Universe
Extending Discussion to Some
Basic Definitions (cont’d)
• Star
– A globe of gas held
together by its own
gravity and supported
by the internal pressure
of its hot gases, which
generate energy by
nuclear fusion.
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1.2 From Solar System to Galaxy to Universe
Extending Discussion to Some
Basic Definitions (cont’d)
• Solar system
– The Sun and its planets,
asteroids, comets, and
so on.
– The other major planets
in our solar system—
Mercury, Venus, Mars,
Jupiter, Saturn, Uranus,
and Neptune—orbit our
Sun in ellipses that are
nearly circular.
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1.2 From Solar System to Galaxy to Universe
Extending Discussion to Some
Basic Definitions (cont’d)
• Galaxy
– A large system of stars,
star clusters, gas, dust,
and nebulae orbiting a
common centre of mass.
• Spiral arms
– Long spiral pattern of
bright stars, star clusters,
gas, and dust. Spiral
arms extend from the
centre to the edge of the
disk of spiral galaxies.
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1.2 From Solar System to Galaxy to Universe
The Scientific Method
• How do scientists learn about nature?
– The scientific method—the process by which
scientists form hypotheses and test them against
evidence gathered by experiment and observation.
– A hypothesis is a suggestion about how nature
works, and the evidence is reality.
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1.3 The Cosmic Calendar: Concepts of Time
13.8 Billion Years Since the Big Bang
• Imagine now that 13.8 by is compressed in the
period of one year—as conceptualized by Dr. Carl
Sagan—and divided in 12 months. Now we have
a cosmic calendar.
– Using this analogy, our solar system began to form some
time in mid-August.
– Complex life appeared on Earth some time in midDecember.
– Egyptian pyramids were built 11 seconds before the new
year. Now let’s see that visually...
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1.3
1.2 The Cosmic Calendar: Concepts of Time
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Chapter 1
Summary
• Astronomy: A Global Human Adventure
• From Solar System to Galaxy to Universe
• The Cosmic Calendar: Concepts of Time
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The End
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