7 EXPANSION AND AGE

03:10 Doppler effect

04:20 V/C = Δλ/λ
The ratio of the speed of the object to the speed of the wave is equal to the change in wavelength over the emitted wavelength.

05:30 Pure thermal and real star spectra
Hydrogen's spectral lines: unshifted/redshifted/blueshifted

08:15 Diffraction gratings

09:39 Galaxy Doppler shift

11:29 Hubble law: The entire Universe is expanding
velocity= Hubble constant×distance
Hubble constant =72km/s/megaparsec
=22km/s/Mly

18:55 Calculating the Age of the Universe
V = H × d
Distance / Speed = d / V = d / （H × d ）
= 1 / H ( The Hubble Time )
C / H (The Hubble radius ) = 13.5 billion light years

22:09 Cosmic age estimate - the real Universe

25:08 H-R Diagram and Star Lifetimes

26:57 ...The oldest clusters approach the cosmic age, and must have been formed shortly after the Big Bang, but most importantly there are no clusters much older than 14 billion years...

28:38 Cosmic stretch factor
rsf = λ now / λ emit = d now / d emit

LECTURE 9 DARK MATTER AND DARK ANERGY :96%!
( part 1 )

02:42 Circular orbital motion

Force = mass × acceleration
The gravitational force = GMm/R^2
G is the universal gravitational constant ≈ 6.7×10^-11 N·m^2/kg^2
F = ma
centripetal acceleration = V^2/R
GMm/R^2 = m × (V^2/R)
GM/R^2 = V^2/R
M = V^2·R / G

05:00 Measuring the Mass of the Sun
The Earth moves around the Sun at about 30 kilometer per second...

V = 30km/s
R = 150 million km
M = V^2 R / G
Mˇsun = 2.0×10^30kg
(3.0×10^4)^2 · 1.5×10^11 / 6.7×10^-11 ≈ 2.0×10^30


05:35 Measuring the mass of a Galaxy

07:11 Solar system rotation curve

07:34 Galaxy rotation curve

第十课打卡 宇宙的几何形状

C=2πr 半径越大周长越短？AWSl
希望我们的宇宙是圆圆的萌萌哒正曲率宇宙～ 比较有安全感(⌒▽⌒)