Astrophysics Science Project Integrating Research and Education

Angle of Particle Arrival

At the end of Activity 2, "Geiger Array: Particle Direction," you discovered that most of Hess' particles were coming straight down to the Earth from above. You also started to understand that these particles were moving very, very fast.

After making these discoveries, scientists began calling Hess' particles Cosmic Rays. Scientists all around the world began studying these Cosmic Rays, they wanted to know everything about them. They needed to understand exactly at what angles the Cosmic Rays were likely to strike the Earth.

In Activity 3,"Geiger Array: Angle of Particle Arrival" you will use Cosmic Ray simulations and computer generated histograms to make more specific observations of Cosmic Ray directions and angles of arrival.


  1. At what angles (with respect to the Earth) are Cosmic Rays usually moving through the atmospere?
  2. Using only the information gained in this experiment, what can you hypothesize about the amount of energy that most Cosmic Rays have? Do they mostly have high energies, or low energies? Hint: the more atmosphere that a Cosmic Ray has to travel through to get to the detector, the more energy it needs to make it.

Do this:
Write the lab title and the investigation questions into your lab notebook unless a handout is provided.
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