Our Earth, 3/4 of the surface covered by often miles-deep saltwater was, once upon a time, waterless.
I make the modest assumption that our planet acquired it’s water via cometary bombardment billions of years ago.
Unless some geologist here knows otherwise, I figure, a still red-hot planet swallowed up an ocean’s-worth of water from the heavens…only to exist as water vapor in an atmosphere too hot to condense and precipitate.
Just how much thicker was our atmosphere compared to today…compared to Venus…compared to a gas giant…etc.
Also, assuming the Earth’s surface magically became cool enough to rain on without instantly boiling away, how long would it rain before it stopped?
I do not know what our atmosphere was like when the planet formed.
We do know the planet needed to cool off enough to allow water to condense and collect. If the earth is 4.5 billion years old then a few hundred million years is doable.
Then add in a few tens of millions of years for the water to precipitate. This article suggests the water was not mostly from comets. Either way, the water on earth would collect over tens of millions of years which still leaves a few billion left over.
One inch per year would be 158 miles deep of water in 10 million years. (just an example)
I think the Tl;Dr of it is that we forget the reaaaalllly long times involved in the formation of the earth. Humans have been here for barely an eye-blink.
There have been three different stages to the atmosphere. The earliest atmosphere was primarily hydrogen and hydrogen, the gases present in the solar system when Earth formed. The next atmosphere stage was primarily nitrogen. The third and current stage is an atmosphere with a large oxygen component, although still a majority nitrogen.
It might be “miles deep” as the OP said, but it’s actually a very, very thin film on the surface of a large rockball.
Ref wiki, Earth’s water is about 1/4400 = 0.022% of the total mass. The bulk of the Earth is a very, very dry place. Fortunately the very scarce water is concentrated on the surface where we are.
It was really surprising to me the first time I saw that illustration just how little water there actually is, in relation to the size of the Earth, though we think of Earth as a ‘water planet’. The smallest dot, representing all the freshwater lakes and rivers, doesn’t look like it could fill a single Great Lake.
I remember hearing somewhere that if the Earth was reduced to the size of a golf ball, its surface would be smoother than the golf ball— in other words, the deepest ocean is not as deep as a dimple on a golf ball. All the Earth’s water is really just a thin film of moisture clinging to a giant rock.
You mean a billiard/snooker/pool ball. If the average dimple on a golf ball is 0.01 inches deep, that would be a depression on Earth more than 40 miles deep!
No, the point was that the surface of a golf ball-sized Earth would be smoother than the dimples on a golf ball. That does not disagree with your statement.
It doesn’t but you’re misremembering the factoid. A golf ball isn’t smooth at all. The point is that a billiard ball sized Earth would be smoother than a billiard ball, which is much more counter-intuitive.
No, I’m not misremembering the factoid. The point of the comparison was that one might assume that a golf-ball sized Earth would have dents in it where the oceans are, that are about as deep as the dimples on a golf ball, but in fact it would be smoother than the golf ball.
You might have heard or made your own factoid comparison of the surface of the Earth to a billiard ball, which is fine. But it doesn’t mean I’m misremembering my factoid.
I mean, it’s true that it’s smoother than a golf ball. It’s much smoother than a golf ball. So much smoother that a golf ball isn’t a useful comparison at all.
Well, it’s not true that it’s smoother than a billiard ball, either:
This article gave all the advantages to the proposition that the Earth was proportionally smoother than a cueball, but still fails. For example, the Marianas Trench is about 1700 ppm lower than the surface, Mount Everest about 1500ppm from average. That would put a lot of mountain ranges in the 500-1000 range.
The author then tested three cueballs, and the biggest difference he could find was on a practice ball that had some damage, and the biggest divot was about 100 ppm, or 17 times less than the Marianas trench. That translates into a change of +2.67 to -3.08 um.
A golf ball divot is about 254 um, so about 100 times the size of the biggest flaw in the worst cueball. And a golf ball is much smaller, so the PPM would be higher.
So, the golf ball divots are at least 10-20 times bigger than the biggest surface differences on Earth, while the Billiard ball is about 15-20 times smoother comparing the largest divots on one to the largest changes on Earth.
The reality is almost smack in the middle between those. The billiard ball thing was always too good to be true, but made for a popular comparison. If the Earth was the size of a cueball it would be visibly rough in places and quite smooth in others, and you’d feel the mountain ranges if you ran your fingers over them.
Makes me wonder if anyone markets an “anatomically correct” dry Earth mockup that’s about billiard ball size. Could even be softball or golfball size. Just something we can see and feel the texture of.
I found a couple that have vastly exaggerated vertical relief. But nothing close to the real thing.
I was giving some thought as to how updrafts, downdrafts, and phase transitions…heats of vaporization and crystallization…along with the crushing air pressure near the surface versus the near vacuum at the stratosphere…above the weather…can channel heat away from the planet’s surface to space.
Ultimately, heat leaves earth radiantly, but to get from the surface to the top of the clouds requires convection.
Snow and hail falling in a downdraft melting into rain absorbs heat, and rain evaporating into steam absorbs heat again.
Great thermal updrafts, like what’s found in massive thunderstorms, carry heat upwards until the water vapor encounters the appropriate level of low temperatures and pressures, triggering precipitation in the form of liquid and even frozen condensates…rain and snow. Thus heat is released.
