EM Waves: Microwaves & The Big Bang!


Work with your group to sketch and label the two different ways x-rays are created by humans.

Those full body scans at the airport use 1.00 mm light:

    • Determine the frequency of that light
    • Determine the energy contained in one photon of that light
    • Determine the type of RMIVUXG for that light


LEARNING TARGET: I will be able to describe how microwaves are used to determine the age of the Universe during today's class.


  • hertz (Hz): a measure of wave frequency in waves/second
  • electromagnetic waves (light waves from radio - gamma)
  • quantum jump
  • energy levels
  • excited (electron) = ("electrons 'jolted' into a higher energy level")
  • rest state (electron) = ("electrons existing on the lowest energy level")


h = Plank's Constant = (6.63 x 10-34 m2kg/s)

c=λυ: The speed of light (c) = wavelength (λ "lamda") x frequency "nu")

E = hυ (The energy in a photon of light is given by Plank's Constant times the frequency of that light



Matter-Antimatter Annihilation occurred at 10-6 seconds after the Big Bang. Virtually ALL of the antimatter particles (such as positrons) and ALMOST all of the matter particles in the Universe (such as electrons) combined and annihilated each other. Each tiny collision produced a gamma ray of light. Because there were so many collisions, a MASSIVE amount of gamma light was produced. The Universe was so hot during this time that the gamma rays couldn't escape. As the Universe expanded, it cooled... and about 300,000 years after the Big Bang....

THE DARK AGE began when the Universe cooled off enough so that photons (that were created during the Matter-Antimatter Annihilation) could fly free. At that point, the Universe quite literarily went dark.


Those photons continued to expand as the Universe expanded, losing energy all the way down through the EM spectrum. Those seeting, high energy gamma photons 'cooled' off to x-ray, UV, through the visible spectrum, passed IR and are now present EVERYWHERE in the Universe as microwaves. Three generations of sattelites (COBE, MAPI and PLANCK) have measured those microwaves with greater and greater precision giving us, among things... the temperature of the Universe (2.74 K, which is a VERY chilly -455 degrees F) and the age of the Universe 13.74 billion years)


Now let's review our work from yesterday. The general form of the graphic below is helpful:


However THIS form of the Big Bang Timeline is a bit more expressive:



Today we're going to concentrate on the WMAP probe


COBE: COsmic microwave Background Observer - 1989



WMAP: Wilkinson Microwave Anistropy Probe (NASA) active from 2001 - 2010 (according to NASA the WMAP probe improved the measurements made by COBE by an astounding 68,000 times).

Here is a tough (but readable) summery of that mission



Please take a gander at this SHORT reading about the WMAP

Now let's take a quick glance at this TOUGH reading. Please keep in mind this is an article written BY astronomers FOR astronomers and not for high school students.


The European Space Agency launched the Planck Satellite (2009 - 2013) that collected THIS data


And better yet THIS data:


From all of that data, scientists have very, very strong evidence to support the Big Bang Theory.

That theory is so well researched and the evidence is so strong that there is no other scientific theory to explain how the Universe was formed.

From that data we know the temperature of the Universe (2.73 Kelvins (degrees above absolute zero) and the age of the Universe (13.82 billion years)


How can a light wave "cool off" ???