ASTR 170B2 Study Guide - Fall 2018, Comprehensive Midterm Notes - Sun, Earth, Orbit
12 Oct 2018
School
Department
Course
Professor
ASTR 170B2
MIDTERM EXAM
STUDY GUIDE
Fall 2018
ASTR PTYS 170 B2 - Lecture 1 - The Earth and The Cosmos
Introduction / Helpful and Cool Information
● In some places on Earth, the Sun does not set
○ Like Finland for example, half of the country experiences this when the Sun gets
low to set but never goes below the horizon before rising again.
● Distance from Tucson AZ to Finland: 8750km
● Flight Itenerary:
○ Tucson to Dallas /Fort Worth - time: 2 h 14 m
■ Average speed 650 km/h
○ Dallas/ Fort Worth to New York - time 3h 31 m
■ Average speed 640 km/h
○ New York to Helsinki - time 8 h 5 min
■ Average speed 830 km/h
● In the class we will use MKS units (Meters, Grams, and Seconds)
● Quick simple unit conversions:
○ 1 mile = 1.6 km or 1,600 m
○ 1 foot = 0.3 m
○ 1 lb = 0.45 kg 0r 450 m
Earth Basics
● Radius: 6370 km (3960 miles)
● Circumference: 2�R =40,000 km (24,900 miles)
Zenith Angles and the Size of the Earth
● The size of the Earth was first determined in 230 BC Egypt
● Erastothenes of Cyrene determined the size of the Earth in about 230 BC by
comparing the solar noon zenith angle in Alexandria and Syene
● Local Zenith: Point in the sky directly above an object (commonly someone’s head)
● Meridian: In the dome around the surface of the Earth, it is the line between the North
and South.
● Horizon: Where, visually, the sky meets the surface of the Earth.
● Full circle is 360°, the arc distance from Alexandria and Syene is 7°, and the distance
between them is about 800 km
● 800 x (360/7) = 41,000 km (good estimation of the circumference)
Mass of the Earth
● 5.97 x kg10 24
find more resources at oneclass.com
find more resources at oneclass.com
● Density = mass /volume
● Density of Earth = 5500 kg/ m3
● The Earth is mostly made of rock and metals, mostly because of the core, while most of
the surface is water.
Material
Air
Water
Wood
Soil
Rock
Metal
Density
1.23
100
600
1400
3000
8000
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Astr ptys 170 b2 - lecture 1 - the earth and the cosmos. In some places on earth, the sun does not set. Like finland for example, half of the country experiences this when the sun gets low to set but never goes below the horizon before rising again. Distance from tucson az to finland: 8750km. Tucson to dallas /fort worth - time: 2 h 14 m. Dallas/ fort worth to new york - time 3h 31 m. New york to helsinki - time 8 h 5 min. In the class we will use mks units (meters, grams, and seconds) 1 mile = 1. 6 km or 1,600 m. 1 lb = 0. 45 kg 0r 450 m. Zenith angles and the size of the earth. The size of the earth was first determined in 230 bc egypt. Erastothenes of cyrene determined the size of the earth in about 230 bc by comparing the solar noon zenith angle in alexandria and syene.
