Notes

Doppler Effect and Red Shift

Temperature Scales

Problem

Doppler effect and red shift

http://science.discovery.com/videos/time-doppler-effect.html

Temperature Scales

Farenheit

 

Fahrenheit usually refers to a temperature scale proposed in 1724 by, and named after, the physicist Daniel Gabriel Fahrenheit (1686–1736). Today, the scale has been replaced by the Celsius scale in most countries; it is still in use for non-scientific purposes in the United States and a few other nations, such as Belize.

On the Fahrenheit scale, the freezing point of water is 32 degrees Fahrenheit (°F) and the boiling point 212 °F (at standard atmospheric pressure),

 

Celcius

 

Celsius (also known as centigrade) is a temperature scale that is named after the Swedish astronomer Anders Celsius (1701–1744), who developed a similar temperature scale two years before his death.

 

From 1744 until 1954, 0 °C was defined as the freezing point of water and 100 °C was defined as the boiling point of water, both at a pressure of one standard atmosphere. Although these defining correlations are commonly taught in schools today, by international agreement the unit "degree Celsius" and the Celsius scale are currently defined by two different points: absolute zero, and the triple point of VSMOW (specially prepared water).

 

Kelvin

The kelvin (symbol: K) is a unit increment of temperature and is one of the seven SI base units. The Kelvin scale is a thermodynamic (absolute) temperature scale where absolute zero, the theoretical absence of all thermal energy, is zero kelvin (0 K). The Kelvin scale and the kelvin are named after the British physicist and engineer William Thomson, 1st Baron Kelvin (1824–1907), who wrote of the need for an "absolute thermometric scale".

Lab Problem 

Problem Concerning the Temperatures at the center and surface of the Sun

The Solar Physics Group at NASA's Marshall Space Flight Center was formed in the early 1970's in conjunction with the Apollo Skylab Mission. Some facts about the Sun published by this group are given below:

Solar radius = 695,990 km = 432,470 mi = 109 Earth radii

Solar mass = 1.989 10³⁰ kg = 4.376 10³⁰ lb = 333,000 Earth masses

Solar luminosity (energy output of the Sun) = 3.846 10³³ erg/s

Surface temperature = 5770 K

Surface density = 2.07 10^-7 g/cm³ = 1.6 10^-4 Air density

Surface composition = 70% H, 28% He, 2% (C, N, O, ...) by mass

Central temperature = 15,600,000 K

Central density = 150 g/cm³ = 8 × Gold density

Central composition = 35% H, 63% He, 2% (C, N, O, ...) by mass

1. Convert these temperatures to C and to F

 

C = K - 273.15          F = (9/5)C + 32

 

	Kelvin	Centigrade	Fahrenheit
Surface Temperature	5770	5496.85	9,926.33
Central Temperature	15,600,000	15,599,726.85	28,079,540.34

 

 

2. What are these estimates based on? How are they determined?

 

 

3. Explain a rationale for the center being hotter than the surface.

 

The solar interior is separated into four regions by the different processes that occur there. Energy is generated in the core, the innermost 25%. This energy diffuses outward by radiation (mostly gamma-rays and x-rays) through the radiative zone and by convective fluid flows (boiling motion) through the convection zone, the outermost 30%.

Surface exposed to low temperature of space