Transcript Lecture 1: The Scale of the Cosmos

PSc 100D
The Solar System
Please pick up a transmitter
(“clicker”) for the response
system.
PSc 100D
The Solar System
Associate Professor M. Böttcher
Clippinger Hall #339
Phone: 593 1714
E-mail: [email protected]
Office Hours:
Mo., Tu., We., Th., 5:00 p.m. – 6:00 p.m.
General Information
• Course
Web Site:
http://www.phy.ohiou.edu/~mboett/PSC100D/winter09/PSC100D_winter09.html
Link
Check this web site regularly.
All updates, reading and writing
assignments, exam results, etc. will be
posted on this web site
The Response System
• We will use the personal response system
(PRS) for questions + answers throughout the
lectures (Mo. – We.).
• Class participation during regular lectures will
enter with 10 % into the final class grade.
• Also used for 6 Reasing Assignment Quizzes
almost every Thursday.
• Scores of Reading Assignment Quizzes will be
combined to 30 % of your final class grade.
Example: Which of the
following is not a part of
the solar system?
1.
2.
3.
4.
5.
Planets
A star
A galaxy
Comets
Meteoroids
As a Matter of Courtesy
• Please turn your cell phones off
or on vibrating mode during the
lectures
• If you really need to leave during
the lecture, do so quietly, through
the rear door of the lecture hall.
The Scale of the Cosmos
• Astronomy deals with objects on a vast
range of size scales and time scales.
• Most of these size and time scales are way
beyond our every-day experience.
• Humans, the Earth, and even the solar system
are tiny and unimportant on cosmic scales.
A Campus Scene
16 x 16 m
A City View
1 mile x 1 mile
The Landscape of Pennsylvania
100 miles x 100 miles
The Earth
Diameter of the Earth: 12,756 km
Guess: How many times would you have to
travel around the Earth to travel the distance
between the Earth and the moon?
1.
2.
3.
4.
5.
2.1
9.6
26
745
1.38 million
Earth and Moon
Distance Earth – Moon: 384,000 km
Earth orbiting around the Sun
Distance Sun – Earth = 150,000,000 km
Earth orbiting around the Sun
In order to avoid large
numbers beyond our
imagination, we introduce
new units:
1 Astronomical Unit (AU)
= Distance Sun – Earth =
150 million km
How many miles are
there in 1 AU?
1.
2.
3.
4.
5.
245,000
9.4 million
93.7 million
1.38 billion
3.6 trillion
The Solar System
Approx. 100 AU
(Almost) Empty Space
Around our Solar System
Approx. 10,000 AU
The Solar Neighborhood
Approx. 17 light years
The Solar Neighborhood
New distance scale:
1 light year (ly) =
Distance traveled by light in 1 year
= 63,000 AU = 1013 km
= 10,000,000,000,000 km
(= 1 + 13 zeros)
= 10 trillion km
Nearest star to the Sun:
Approx. 17 light years
Proxima Centauri, at a distance of
4.2 light years
1 AU (= 150 million =
150,000,000 km) equals
1.
2.
3.
4.
5.
1.5*108 km
1.5*1010 km
1.5*1015 km
8*1015 km
8*101.5 km
The Extended Solar Neighborhood
Approx. 1,700 light years
The Milky Way Galaxy
Diameter of the Milky Way: ~ 75,000 light years
Animation
The diameter of the
Milky Way is
1.
2.
3.
4.
5.
7.5*103 light years
7.5*104 light years
7.5*105 light years
5*107.5 light years
57.5 light years
The Local Group of Galaxies
Galaxies usually don’t exist alone, but in clusters of galaxies
Distance to the nearest large galaxies:
several million light years
The Universe on Very Large Scales
Clusters of galaxies are grouped into superclusters.
Superclusters form filaments and walls around voids.