Take-Home Message & Topic Sentence Outlines samples


THM: Solar sails offer a fuel-less propulsion method that is actively being research for applications in unmanned spacecraft and satellites.

  1. Solar sails are a space propulsion method that utilize radiation pressure emitted from a star instead of a fuel.
  2. Radiation pressure is a small force that acts upon anything exposed to electromagnetic radiation due to the momentum imparted by photon collisions.
  3. Due to the weakness of radiation pressure, large sail structures are required for any meaningful propulsion.
  4. A Japanese spacecraft, IKAROS, has already been launched and demonstrated the use of solar sails as a propulsion method.
  5. Solar sails are being looked at for additional usage in probes and as a means to decelerate and deorbit satellites.


THM: Doppler cooling, and laser cooling as a whole, allows cooling of samples to allow very precise measurements and interactions.

  1. Doppler cooling is a form of laser cooling that leverages specific frequencies of lasers to cause atoms to emit photons and thus lose kinetic energy (reduce in temperature).
  2. Utilizing a specific frequency light, atoms have their electrons excited based on their movement thanks to the Doppler effect altering the light's frequency.
  3. Doppler cooling has a theoretical minimum reachable temperature known as the Doppler temperature, at which point momentum is no longer lost due to collisions.
  4. Doppler cooling is used in technologies such as precise atomic clocks and magneto-optical traps.
  5. Alternative methods of laser cooling such as Sisyphus cooling and optical molasses have been developed that overcome the Doppler temperature limit of Doppler cooling.


THM: Auroras are a beautiful spectacle of light in nature that is the result of a complex interaction of earth's magnetic field and our sun.

  1. An aurora is a naturally occurring display of light found near the magnetic poles due to interaction between solar winds and earth's magnetic field.
  2. Auroras are typically found in the auroral zone, a band approximately 5 through 15 degrees away from Earth's magnetic poles.
  3. Auroras are thought to be caused by ionization of the atmosphere by solar winds guided by the magnetic fields, though the full reason is not entirely known.
  4. The auroras themselves can take on many colors and are divided into discrete (curtain-like) auroras and diffuse auroras.

Your comments and suggestions are appreciated.

To cite this page:
Samples: THM and TSO
Edited by: wilkins@mps.ohio-state.edu on