Readers of Action-Reaction may be interested in this recent post on my 180 blog.

*College-Prep Physics:* Even though we now have a mathematical relationship between mass and weight, we still don’t know what causes Earth’s gravitational pull. So first, we took a short survey:

Download a copy here: GRAVITY Survey 2015

Then we went through each of the four claims in survey question 4 and did a testing experiment for each claim.

**CLAIM #1: Earth’s Magnetism**

**CLAIM #2: Earth ‘s Rotation**

**CLAIM #3: Air Pressure**

**CLAIM #4: Earth’s Mass**

We also compared characteristics of different planets using a table of planetary data.

This sequence of claims and questioning is based off one found in *Preconceptions in Mechanics*. On Tuesday, we’ll discuss the relative strengths of the gravitational pulls that 2 masses exert on each other.

##BFPM

*NGSS Science and Engineering Practice #6. Constructing Explanations *

Find some amazing facts about Earth Magnetism… click here http://bit.ly/1oZUf5d

Amazing work here. Thanks for being your own special kind of awesome…!!!

For a better explanation of what causes gravity just look at the equation for escape velocity Ve^2 = 2GM/r. That Ve^2 looks a lot like a field diluted C^2 and the C^2 looks a lot like the rest energy per unit mass of M. So just spread the rest mass energy out as a field and call it gravity.