View source for Misc science info

This article will be about miscellaneous science information that I have not organized just yet.

==The Six Great Stages of Evolution on Earth==
#From the origin of life to the ”Last Common Ancestor"
#Prokaryote diversification
#Unicellular eukaryote diversification
#Multicellularity
#Invasion of the land
#Appearance of intelligence and technology. 

==Back of the Envelope Calculations (BotEC)==
 see: [[wikipedia:Fermi problem]]
It is a good practice to use the following steps when performing BotEC's:

;Formula(s) : formula(s) that provide a roadmap to the upcoming calculations. The formula should include names for any quantity that will be estimated, and should give units of measurement (in parentheses). Conversion factors (e.g. bits/Byte) can appear without a name.
;Estimates : Estimates of the quantities appearing in the formula. There should be a very brief justification of the estimate if it is not obvious. You should use "wiggley equal signs" to indicate approximations.
;Calculation(s): Calculations in which the estimates and known facts are substituted into the formula. 

===Example #1: Calculate the bandwidth needed for full screen video===

;Formula
:Bandwidth (Bytes/sec) = ScreenSize(dots/image) x RefreshRate (images/sec) x Information (Bytes/dot)

;Estimates
:ScreenSize ~= 1,000,000 dots/image (estimating a 1000x1000 screen)
:RefreshRate ~= 30 images/second (so eye won't see flicker)
:Information = 3 Bytes/dot (one Byte each for R, G, B) 

;Calculation
:Bandwidth ~= 10^6 dots/image x 30 images/sec x 3 Bytes/dot = 90x10^6 Bytes/sec ~= '''100 MByte/sec'''

===Example #2: AU / ly===
*Calculate the number of astronomical units (AU) in a light-year (ly)

 Speed of light ~= 300,000 km/sec
 Seconds in a year = 60 X 60 X 24 X 365.25 = 31,557,600
 Distance traveled in a year = speed in km/sec X seconds
 = 9,467,280,000,000 km = 1 Light Year
 
 1 AU = 149,598,500 km
 
 Number of AU in 1 ly =
 (9,467,280,000,000 km) / (149,598,500 km)
 = 9,467,280,000 / 149,598.5 =
 = 946728 / 15 
 = 63115.2 AU/ly
 ---------------------------------------------------------
 c = speed of light = 2.99792458E+8 m/s
 y = seconds per (tropical) year = 31556926
 cy = one lightyear in meters = 9.460528412641E+15 meters
 au = one astronomical unit = 1.49597870691E+11 meters
 # There are cy/au astronomical units in one lightyear.
 cy/au = 63239.7
 # If you use the Julian year instead of the tropical year 
 # to calculate the number of meters in a light-year, then
 y = 31557600
 cy = 9.46073047258E+15 meters
 cy/au = 63241.1
 ---------------------------------------------------------
 1 light-year = 63.241 × 10^3 AU = 63,241 AU
 1 AU = 149,597,870,700 metres 
      = 149.60 x 10^6 km 
      = 149.60 x 10^9 m
 1 AU ~= 499 seconds
      ~= 8.32 minutes for light to travel this distance
 1 light-year = 9460730472580800 metres (exactly)
 1 year = 365.25 days (exactly)
 1 year = 86400 SI seconds, totaling 31,557,600 seconds)
        = pi x 10^7 s
 speed of light = 299792458 m/s
 ---------------------------------------------------------
 speed of light in AU/hr:
 2.998 x 10^8m/s = (2.998x10^8 m/s)/(1000 m/km)
  = 2.998 x 10^5 km/s = (2.998x10^5 km/s)*(3600 s/h)
  = 10792.8 x 10^5 km/h = 1.07928 x 10^9 km/h
  = (1.07928 x10^9 km/h)(1/(1.50 x 10^8 km/Au)
  = 0.71952 x10^1 Au/ h= 7.1952 Au/h,
 ~= 7.20 AU/h (at 3 significant figures)
 # the accuracy of the least accurate data "1.50 x10^8 km/Au"

===Misc examples===
*Victor Weisskopf's pamphlet ''Modern Physics from an Elementary Point of View''.<ref>[http://cdsweb.cern.ch/record/274976/ Lectures given in the 1969 Summer Lecture Programme, CERN (European Organization for  Nuclear Research), CERN 70-8, 17 March 1970.]</ref> In these notes Weisskopf used back-of-the-envelope calculations to calculate the size of a hydrogen atom, a star, and a mountain, all using elementary physics.

*Land area for use by humans:
 Each family get a piece of land of area A = 30m x 30m = 10^3 m^2 (or about 1/4 acre).
 Therefore, all of us together will use a total land area of
 A = 6 x 10^9 people * (1 family)/(3 people) * (10^3 m^2)/(family) = 2 x 10^12 m^2
 
 (when one multiplies numbers in scientific notation, one multiplies the coefficients
 and adds the exponents. In this case, 10^9 x 10^3 = 10^(9+3) = 10^12.)
 
 This is 2 x 10^6 km^2 (two million square kilometres); around the area of Alaska or
 twice the area of Egypt, which is about 1% of the surface area of the Earth.

==External links==
*[http://www.eurekalert.org/pub_releases/2009-04/cu-bin033009.php Being Isaac Newton: Computer derives natural laws from raw data]
*[http://www.dailygalaxy.com/my_weblog/2009/04/the-six-great-s.html The Six Great Stages of Evolution on Earth -- Is There a Seventh?]

[[Category:Science]]