The Gravity of the Situation

Background Information:

The mythical story of an apple dropping on Newton’s head is simply one way to describe gravity.  Dropping a large textbook and a feather is a way to illustrated it, but what if you really want to define it.  Turns out, it’s not so easy.

Explaining Einstein’s general theory of relativity to an 8 year old can be a challenge (even to a 34 year old former science teacher), so as educators we usually rely on Newton’s law of universal gravitation to approximate this challenging force.  Regardless of which you use in the classroom, you now may have a little more confidence in your explanation.  On May 4, 2011, we received a status update on the data Gravity Probe B.

Einstein’s general theory of relativity, even-though well known, is supported with very little test data.  The math is there, but few experiments have been performed.   One of the first major experiments occurred in the late 1970’s with the launch of, what else, Gravity Probe A.  This probe was designed to test, what Einstein predicted,  gravitation redshift.  The data gathered from Gravity Probe A confirmed, with greater precision, that gravity slows the flow of time.  After more than 30 years of design, launch and analysis of the Gravity Probe B, we now have a more precise understanding of two more Einstein predictions.

  1. The geodetic effect—the amount by which the Earth warps the local spacetime in which it resides.
  2. The frame-dragging effect—the amount by which the rotating Earth drags its local spacetime around with it.


Demonstrations of gravity are rather easy to accomplish.  A simple book and a piece of paper can make for a great visual.  Holding up a sheet of paper and a book, tell students to watch as you drop both from the same height. What did you see?  What do you know?  What do you wonder?  Repeat this demonstration, only this time place the sheet of paper on top of the book.  Ask again the  I see, I know and I wonder questions.  This will open up many other questions, challenging some students’ understanding of gravity and creating an environment for open discussion on the concept.


There’s a lot of resources out there on gravity, but as I mentioned before, not all are easily digestible by all students.  Working with seniors in an AP Physics class, great.  Take the data here and go nuts.  I find it fascinating, but well over my head.   If you have access to one of our Discovery Education Science resources like the Techbook try an Exploration like the one below.

Check back next week as we pull you deeper in the gravity discussion with current research happening at CERN.



  1. John said:

    Larry Gonick’s cartoon guides to science is a great way to teach the principles of physics to a youngster. He has a titled called “The Cartoon Guide to Physics.”

    I didn’t pickup on Larry’s work until university. The info he lays out is good enough for college studies, but the principles are basic enough for children to understand.

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