磁力网站The Teaching Company 美国最著名的大学教育课程制作公司之一，专门聘请世界一流大学的顶尖级教授讲授大学程度的各种课程，并推出课程的磁带，录像带，CD，DVD和学习手册，因注重学术性，教育性和娱乐性，符合终身学习的时代观念，在业界享有盛誉。由它推出的课程简称为TTC course，又名 The Great Course。（http://blog.sina.com.cn/s/blog_687f9d370102uyft.html）
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
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
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