When I was a child, I read many times over with fascination about the formation of the Earth in a large illustrated encyclopedia of sorts for adults (one of at least two volumes, though I will probably never remember the title). The first few chapters dealt with the formation of the solar system and the accretion of matter that created planetesimals that would eventually coalesce into the planets, the late bombardment, the creation of the Moon, and so on, peppered with beautiful artistic impressions.
Today I remembered that there were a few pages talking about how water came to the Earth and how the first oceans formed. The atmosphere must have had an immense amount of water vapour, but for a very long time the surface of the planet was far too hot for the raindrops to reach the ground. The Earth eventually became completely shrouded in clouds for many millennia, as the water vapour kept building up and condensed in the very top of the atmosphere, but had nowhere to go. And then one day water started falling to the ground faster than it evaporated, unleashing a downpour of unimaginable proportions which lasted centuries without abating.
My question is, is that an accurate picture? Can we actually figure out even so much as the order of magnitude of how long the first showers on Earth lasted for, or was the interval of "centuries" used solely for dramatic effect?
PS: I mean to make absolutely no reference to mythological events. I am talking strictly about what we can know by applying science. Also, apologies if this question is too soft.
Best Answer
Interestingly I recall the same kind of account (I am 49) and was looking seeking and researching it in the last few weeks; see http://www.amnh.org/learn/ocean/Resource1 . It would seem that one infers that this has to be a fairly accurate picture: the origin of water on Earth though is still very uncertain but it seems that much water was here in the atmosphere whilst the Earth's surface was hot enough to drive the scenario you describe. The linked document sums it up simply as "Earth’s thick steam atmosphere slowly cooled to the point where water was stable as liquid" in a short section called "Things Cool Off". It is known there was liquid water on the Earth's surface $4.2\times10^9$ years ago, about $3.55\times10^8$ years after Earth's formation. I daresay some experts would have some back of the envelope calculations as to how long it rained, but I presume concrete geological evidence for this period is very scanty. It likely wouldn't be that well defined: not everywhere on the Earth's surface would be at the same temperature so one would probably have a slow and ill-defined shift from an intensely steamy fog to something you and I would call a rainstorm.