Creating an Earth System II:

The Electromagnetic Spectrum

A quick review:

The Sun is a star - a furnace in which hydrogen nuclei undergo fusion to produce helium (and much rarer and heavier elements), and during which, about 0.3% of their mass is converted to energy.

The Sun emits energy in two major forms:

  1. The solid material is called plasma (which is actually the composition of the sun), a mixture of ions, electrons, and neutral atoms, which is emitted along perturbations in the Sun's magnetic field, and causes solar flares and coronal mass ejections (CMEs).

  2. Radiation (heat energy) has no mass and travels at the speed of light. Radiation is one of three ways in which heat is transferred:
  • Conduction: Heat (energy is transferred from warmer to cooler materials by direct molecular contact (e.g. hand burned by a pot handle).

  • Convection: Heat moves with a substance from one place to another.

  • Radiation: Heat moves from source through a material or vacuum.

Radiation is emitted throughout the electromagnetic spectrum at the speed of light, whether or not we can see it. The shorter the wavelength, the higher the energy.

In the image on the left, The electromagnetic spectrum illustrates the wavelengths and names of various types of radiation.

image courtesy


Solar radiation is composed of:

  • 40% at wavelengths of infrared (IR) or longer

  • 50% at visible wavelengths

  • 10% at wavelengths of ultraviolet (UV) or shorter (think: skin penetration)


Infrared: More Than Your Eyes Can See

This NASA video discusses infrared light and the measurement of temperature differences. It is appropriate for grades 5-8, 7 minutes in length, closed-captioned, and sells for $10.00. It is available from NASA CORE: Visit NASA CORE or e-mail:

Some important points from the video:

  • Infrared is actually a measurement of temperature. Thus all living organisms emit infrared, as do machines, etc.
  • Infrared can pass through things, but at the same time it is blocked by others (such as glass and water vapor).
  • Planets do not give off visible light, but they do give off infrared. Therefore infrared may be helpful in searching for planets and in providing a more complete view of the universe.

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