Quote:
Originally Posted by Jim Colyer  If the moon's gravity is strong enough to cause the tides, why does it not rip away earth's lighter atmosphere?
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We know that every molecule of the atmosphere are of higher individual speeds (actual atomic speeds) than that their group speeds (wind speeds).
The actual temperatures in the upper atmosphere are much higher than the room temperatures in the lower atmosphere. And the speeds and directions of individual air molecules are of random/statistical distribution. That means even though without the presence of the Moon, some molecules have already tried to run away from the Earth. Perhaps part of them were successful, while most of them recaptured by the Earth. I don't know the exact relative scales of the runaway speed for an object. But it seems that there is also the replenishments from the ocean water, the volcano vapor and the meteoric gas. Only when the loss is greater than the gain, then our atmosphere will gradually diminish. Just like what happened to the Mars.
So, I think, the run away really increased a little by the pull from the gravity of the moon, but not too obvious.
Best Regards. Bottomlander