Flashcards in Lecture 1 Deck (44)
The scientific method is a procedure for formulating hypotheses about the universe.
These are tested by observation
or experimentation in order to build consistent models or theories that accurately describe phenomena in nature
gather facts --> guess an explanation --> test hypothesis --> modify hypothesis
What is the closest star to Earth ?
What is the second closest star in the sky ?
What is the brightest star in the sky ?
star sirius is the second brightest star
How long does it take Earth to rotate once on its axis ?
How long does it take Earth to orbit once around the Sun?
1 year (365 days)
Does the moon move? If so, how?
- Moon orbits earth once every 28 days
Moon also rotates on its axis
Why do we have Day and Night
The side facing the sun has daylight
The other side has darkness (night-time)
Astronomy is the study of...
the totality of all of space, time, matter and energy.
It is a subject like no other – we need to change our perspective of size, scales and times unfamiliar to us
The universe is HUGE! So we must think BIG!
Astronomers measure length in
meters, astronomical units and light years
what is a astronomical unit
Its the distance from the earth to sun
1 astronimcal unit (AU)
= 1.5x10^11 meters
= 150 million kilometers
What is a lightyear
Distance traveled by light in one year .
Its a measure of length not time
1 light year (ly)
= 9.5 x10^15
Astronomers measure time in
seconds and years
Astronomers measure mass in
what is a star
– large burning ball of gas
what is a planet?
orbits a star
what's a moon ?
orbits a planet (sometimes called satellite)
What's a asteroid ?
relatively small rocky object orbiting a star
what's a comet ?
relatively small icy object orbiting a star
what's a galaxy ?
a group of stars clumped together (by gravity)
what is the organization of the universe ?
Universe --> superclusters of galaxies --> groups of galaxies --> galaxies --> solar system --> moons
what are superclusters of galaxies
thousands of galaxies held together by gravity
what are groups of galaxies ?
smaller amount of galaxies
held together by gravity
what are galaxies
groups of stars (~100 billion stars in each)
solar system ?
planets, asteroids, comets revolving (orbiting) around one star
revolving (orbiting) around planets
where is earth in the universe ?
in the local supercluster --> in the local cluster --> in the milky way --> in the solar system containing the sun as the star --> 3rd planet from the sun
Everything in the universe was confined to a single point
That point then “exploded” and expanded into the universe we know today (Big Bang)
Note: There was nothing before the big bang ( i.e., no space – the Big Bang created space)
time 10^-6 s
Earliest matter was created in the form of Plasma (resembles both gas and liquid)