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
Action-Reaction 
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.