• General

  • Stack Exchange - General Q&A Forum - Useful for Math, Phsyics Astronomy etc - FREE!
    • Math Stack Exchange - Q&A Forum for Math - FREE!
    • Physics Stack Exchange - Q&A Forum for Physics - FREE!
    • Astronomy Stack Exchange - Q&A Forum for Astronomy - FREE!

• Astronomy websites

  • List of Astronomical-Cosmological references
  • The Milky Way (video 42.21 min)
  • Before the Big Bang 6: Can the Universe Create Itself (video 52.25 min)
  • The Big Bang was not the origin of the universe - Interview of Sir Roger Penrose (video 41.09 min)

• Math websites

  • Indiana Pi Bill
  • Khan academy - math (cannot use Internet Explorer browser)

• Engineering websites

General interest miscellany

Test your internet speed (www.speedtest.net)

How Lucky We Are

Phenomenal Wonders of the Natural World

How just one animal changed the environment

How BIG are bacteria?

What Your Body Does in a Day

Mother Earth

The Galaxy Song - from The Meaning Of Life

How big are you?

How big Australia is

Rare Old Photos

What a Wonderful World

Galileo Experiment

Weird World 1 pictures

Great animal pictures

Super Blue Blood Moon, Townsville 31 January 2018.pdf

A Pretty Blue Planet

A graphic from NASA shows the amount of space debris floating around the Earth Window to the Universe

Star sizes in the Universe

How Big is Big?

What is 2+2?     Correct answer - Inspector Rex    Miss USA 2011 - Should Math be taught at school

Mathematical notes

S1:  1. Number Sense        2. Is 'one, two, many' a myth?    (CLICK on the videoclip Walpiri counting)         3. COUNTING SYSTEMS AND NUMERALS
4. Mayan, Egyptian, Greek, Babylonian, etc        5. Count with Greek Numbers

S2:  6. A decimal place system has been traced back to c 500 in India        7. List of numeral systems (Wikipedia)
8. Twelve Mind Blowing Number Systems From Other Languages         9. Numbers in different bases        10. OPTIONAL: Dedekind and Number notations

S1:  1. An introduction to modular arithmetic     Exercise1 on Diophantine equations    Comment - Residues, Dedekind section     Comments on Diophantine equations     Pascal's Triangle

S2:  2. An introduction to modular arithmetic

Astronomy section

What is a parsec?
What makes the spiral shape in galaxies?        Is there a centre of the universe?
Origins of the Universe 101       The Big Bang Theory - An Illustrated Timeline
Topics in studying the Universe - Mathematical

Astronomy notes

Velocity of light c=299,792.458 km/sec    Gravitational constant G = 6.67408 x 10^-11 m³ kg^-1 s^-2

Mass of Earth 5.972 x 10²⁴ kg    Radius of Earth 6371 km    Escape velocity from earth 11.2km/s
Average distance between the Earth and the Sun: 149.60 million km. One complete orbit takes 365.256 days (1 sidereal year), during which time Earth has traveled 940 million km. Eccentricity of Earth's orbit: 0.0167.

If a straight smooth tunnel were bored through a uniform density earth, and a particle released, would it reach the opposite end - and if so how long would it take?
Click here for answer and a detailed mathematical explanation.

One journey of our sun and planets around the center of our Milky Way galaxy is sometimes called a cosmic year. That is approximately 225-250 million Earth-years.
(Ref: http://earthsky.org/astronomy-essentials/milky-way-rotation.)
Therefore with the earth being about 4.54 billion years old, it would have orbited the center of the galaxy about 16-20 times.
The earth is about 26,000 light years from galactic centre.
The diameter of the Milky Way galaxy is 100,000 light years.

Relativity notes

How did Einstein get E=mc²?.         Theory of relativity explained in 7 mins (video)         The Big Bang Theory – An Illustrated Timeline (video ~32 min) Very Good!

Physics section

Velocity of light c=299,792.458 km/sec
EM radiation energy unit is: eV (electron Volt - the energy of moving 1 electron across 1 volt. 1eV = 1.602 x 10^-19 Joules {kg m²2/s²}
1 photon of energy of 1 wavelength of radiation = 6.63 x 10^-34 x f {freq.} Joules

Life, Evolution