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Lecture 1

# ASTA01H3 Lecture 1: ASTA01 LECTURE 1 NOTES

Department
Astronomy
Course Code
ASTA01H3
Professor
Kristen Menou
Lecture
1

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ASTA01 LECTURE 1 NOTES:
Chapter One -> The Scale of the Cosmos
- You will have the ability to see evidence of the beginning to the universe, but you
will not find an edge or an end in space
- As far as we know, the universe is infinite and no matter how far you voyage you will
not run into a wall
- Approx. 90 years ago, astronomers discovered the universe expands
- Approx. 15 years ago, astronomers discovered the universe expands at an
accelerating rate
- In Chapter 1, the main topic is comparing objects of different sizes in order to
comprehend the size of the universe.
- Physicists study collision of objects on the scale of 1fm (1 fermi) -> 0.0000000001m
- The Earth’s diameter is 13,000km
- The rotation of the Earth on its axis each 24hours carries you eastward
- One of the main distance units in Astronomy is AU (Astronomical Units). It is 1.5*
10^8 km = 150 million km = 1.5*10^11 m.
- Using the AU, the distance from Venus to the Sun is approx. 0.7 AU
- Earth, Venus and Mercy are planets small, nonluminous bodies that shine by
reflecting sunlight.
- While Venus and Earth are roughly the same size, Mercury is smaller and is roughly
the size of Earth’s moon
- The Sun is a star, a self-luminous ball of hot has the generates its own energy
- The Sun’s size is roughly 110 times larger in diameter than the Earth 1.4 million km
- Light from the Sun reaches in 8 min, whereas it can take up to 4 hours to reach
Neptune
- A unit of distance larger than AU is defined as A light year” (ly)
- One light year is equivalent to 10^13 km or 63,000 AU
- One of the nearest stars to the Sun is the Proxima Centaury which is 4.2ly from Earth
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