Now that all the kids are playing nice in the sandbox again ... I'll play 'know it all'

cirmand - there are 2 problems with your logic:

1) in the example given for gravity, the 2 cases are operating on very different principles. The pebble in the tennis ball is operating on centrifugal force, not gravity. The 2 forces are similar in nature and effect but can not be used for comparison.

2) in the example of hot air rising, there are too many variables in the comparison. Cold air at very high elevations is caused by many factors including air density and distance from the earth core.

Phew - that's been bugging me for days, glad to finally have it off my chest.

Note smiley in siggy - I'm not trying to restart the argument.