Exploring the Planets
Problems of Study
z
Can’t observe Earth’s interior and other
celestial bodies
z Geophysical
z Spectroscopic
z Theoretical
Problems of Study
z
Can’t duplicate many processes in lab
z Scope
limited
z Wait for lab
Problems of Study
z
Space and time
z Can’t
observe Earth in past times
z Window into the past
Scientific Method
z
Make observations, recognize problems,
ask questions
Scientific Method
z
Formulate possible explanations
(hypotheses) consistent with available
data
Scientific Method
z
Test hypotheses by experimentation or
further observation (data collection)
Scientific Method
z
Reject or test further:
hypothesis Æ theory / law
Keys to Good Scientific Study
Remain objective
z Realize we could by wrong
z
The Solar System
The Solar System
Time
z
Basic unit: second
z 9,192,631,770
oscillations of a 133Cs atomic
clock
Earth: ~4.6 billion years old (Ga)
z Our Sun: ~5 Ga
z Universe: ~13.5 Ga (11 to 20)
z
Vastness can be very difficult to comprehend
Space - Distance
z
Metric:
millimetre - centimetre - metre - kilometre
z
Earth radius: ~6400 kilometres
Windows to the Universe, at http://www.windows.ucar.edu/
Space - Distance
z
Nearest celestial body (i.e., the Moon):
~384,000 kilometres
Space - Distance
z
Source of light and radiant energy (i.e., the
Sun):
~150 million kilometres
(actually 149,597,900 kilometres)
(or 1.496 x 108 kilometres – scientific notation)
Space - Distance
z
Planetary neighbours (i.e., the Solar
System):
~4,504 million kilometres
Space - Distance
z
Solar System “garbage” (i.e., the Oort
Cloud):
~30 trillion kilometres?
Space - Distance
z
Next fusion reactor (i.e., Proxima
Centauri):
~40.7 trillion kilometres
(40,678,000,000,000)
Space - Distance
z
Centre of our city of stars (i.e., Milky Way):
~247,200 trillion kilometres
(247,200,000,000,000,000)
Space - Distance
Nearby city of stars (i.e.,
Andromeda Galaxy):
z
~27,434,000 trillion kilometres
(27,434,000,000,000,000,000)
Space / Time: The Human Factor
Average life span: ~ 70 years
z Driving age: 16 years
z Potential driving span: 54 years or 19,710
days or 473,040 hours
z Drive @ 100 km/hour: 47,304,000 km
z
To drive to the Sun: more than 3 lifetimes
Solar System Space - Distance
z
The Oort Cloud
~30 trillion kilometres?
30,000,000,000,000 km
New Measuring System?
z
Astronomical Units (A.U.): average distance from the
Earth to the Sun
z
z
Light Year (ly): distance that light travels in one year
z
z
Earth is 1 A.U. from the Sun, whereas Neptune is about 30 A.U.
from the Sun
1 light year is about 9.46 x 1012 km or about 63,000 A.U.
Parsec (pc): angular measurement
z
z
Distance at which 1 A.U. perpendicular to the observer’s line of
sight subtends an angle of 1 arcsec (1”)
1 pc = 3.26 ly
Let’s stick with Astronomical Units and Kilometres
Mass vs. Weight
Mass: amount of matter in an object
z Weight: force of gravity on an object
z
Mass of the Earth:
5,976,000,000,000,000,000,000,000 kg
Mass of the Sun: 1,989,000,000,000,000,000,000,000,000,000 kg
But what about scientific notation?
Mass of the Earth: 5.976 x 1024 kg
Mass of the Sun: 1.989 x 1030 kg
That’s easier!
Comparative Mass
Mass of the Earth: 5.976 x 1024 kg
z Mass of the Sun: 1.989 x 1030 kg
z
Mass of the Sun: 332,900 Me
Let’s try to stick to comparative data!!