Jan 26 -- stars on the sky

Finally, there's a clear day. cold, -8 also.
Went back to China from Jan 7 to 18, smog all the time.
Then it's cloudy and rainy, snowy here in toronto for several days. good temprature though.

Today, I saw gemini, tarus, canis minor, auriga, canis major, cassiopeia. Still not dark enough to see everything clear.

Jan 5 -- MasteringAstronomy Seasons

elongated ellipse -- fast on the near side and slow on the far side
directness
tropic of cancer
tropic of capricron
arctic circle
antarctic circle
solstice
equinox
hemispare
discrepancy

dark and cloudy still (Jan 4)

It's still cloudy/rainy/snowy. We only saw blue sky on Dec 30, but not enough to watch stars.

MasteringAstronomy is working now. The first thing is to get a sense of distance.

I also learned the moon and some new words on the web.
Apogee Perigee Avarage
0.405mkm 0.363mkm 0.38mkm
Aphelion Perihelion Avarage
152mkm 147mkm 150mkm 1.5 x 10^8km--- AU
circumference diameter radius

sidereal -- a real full orbit synodic -- a full phase (month)
27.3 29.5 (days)

AU -- Astronomical Unit
light year -- 3 x 10^5km/s x3600 x 24 x 365 = 9460800000000km = 10 ^ 13 km
Mars orbit -- 1.5 AU 220mkm
Jupiter -- 5.2 AU
Saturn -- 10 AU
Uranus -- 20 AU
Neptune -- 30 AU
Pluto -- 40 AU
Alpha Centauri -- 4.1 x 10^13 km

Earth Radius -- 0.0063mkm 6,374km
Earth circuference -- 6,374 x 2 x 3.14 = 40,000 km

Sun Radius -- 0.7mkm 700,000km


milky way -- 10^5 light year in diameter, contains 100billion stars 10^11

local group -- 3 x 10^6 ly across, 40 galaxies
andromada is 2.5 x 10^6 ly
Local supercluster -- 10^8 ly across

observable universe is 15 x 10^9 ly

light emitted from outside of obserable universe has no time to reach us yet.


radius --> radii

Facts:
5 month get to the moon if drive a car 100km/hour
8 hour to the moon use fastest spaceship 50,000km/h
2 year to Jupitor use this spaceship
10 months to Mars
100,000 years to Alpha Centauri

8 min for the sun light to reach earth
5 hours for the sun light to reach pluto