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As someone who likes to pick things apart, I was wondering if their is any detailed explanation as to why Earths oceans have magically boiled way. For that to happen the earths temperature would have rise by like 30 degrees or something, even if they somehow managed to burn all the fossil fuels on earth, temperatures would only rise by 5-10 degrees at most, causing the sea level to rise of course.

Because of GrimDark.

I think it's said that during the siege of the Imperial palace during the Horus Heresy the seas were boiled away by the orbital bombardment. Not sure why the water vapour wouldn't reform the seas though. Unless it somehow left the atmosphere.

It's long before that.

Basically during the age of strife earth was one giant super war. Every weapon concievable was unleashed, and something boiled away the water.

Or maybe some aliens stole it, who knows.

Large amounts of industry over 10k years probably doesn't help either. Although the whole oceans boiling away is also to set the scene for a horrendous cradle of humanity.

But... wouldn't something powerful enough to boil away the oceans also take most of the atmosphere with it?

emperorsGlory wrote:
For that to happen the earths temperature would have rise by like 30 degrees or something, even if they somehow managed to burn all the fossil fuels on earth, temperatures would only rise by 5-10 degrees at most, causing the sea level to rise of course.

No need to rise the temperaure that hight, you only need a few degrees.

Water vapor is a green house gaz, so if you elevate the temperature, more water will evaporate, thus increasing the green house effect, producing more water vapor, increasing the temperature, etc, etc it is a runaway green house effect.

In high altitude, the solar wind (particules) will hit the water molecules shooting them away form the earth, so Earth will lose its water.
It is probably what happened on Venus

Plus, it isn't said that it happenned overnight. It could have taken centuries

Venus is rather a bit hotter than Earth is. And earth in 40k is still habitable. And we probably still have our EM field, which is what shields us from the solar wind. Water vapor doesn't get high enough into the atmosphere to get snagged like that, its too heavy. I think so anyway. Not really my scientific field.

If we're guessing, my guess would be something to do with warfare, some anti-planetary weapon of some sort. Or maybe they used it all up in some technological process to make electricity.

emperorsGlory wrote:
As someone who likes to pick things apart, I was wondering if their is any detailed explanation as to why Earths oceans have magically boiled way. For that to happen the earths temperature would have rise by like 30 degrees or something, even if they somehow managed to burn all the fossil fuels on earth, temperatures would only rise by 5-10 degrees at most, causing the sea level to rise of course.

Historic industrial exploitation, ecological damage, and finally ending in orbital bombardment during the Heresy.

 Flo wrote:

emperorsGlory wrote:
For that to happen the earths temperature would have rise by like 30 degrees or something, even if they somehow managed to burn all the fossil fuels on earth, temperatures would only rise by 5-10 degrees at most, causing the sea level to rise of course.

No need to rise the temperaure that hight, you only need a few degrees.

Water vapor is a green house gaz, so if you elevate the temperature, more water will evaporate, thus increasing the green house effect, producing more water vapor, increasing the temperature, etc, etc it is a runaway green house effect.

In high altitude, the solar wind (particules) will hit the water molecules shooting them away form the earth, so Earth will lose its water.
It is probably what happened on Venus

Plus, it isn't said that it happenned overnight. It could have taken centuries

I though some fairly crazy explosions can cause bits and pieces to fly competently off planet.

but il take a bit of column a and b please

Earth wouldn't be habitable if the oceans boiled away.

40k is not about science it's made up space fantasy. Don't expect logic or science in it.

They've covered the earth in concrete. All the water is probably bound up chemically in there

Flinty's answer is probably the most accurate one. The oceans may have 'boiled away', but the'll have been condescend back into underground reservoirs.

posted in this thread by accident...

Maybe they use water in Rockrete. And then exported it.

Its because of when Horus bombarded the planet during the siege of Terra.

Granted, much of the vapor would have eventually re-condensed as rain. Multiple times actually during the siege. So you actually would have had the air becoming super saturated. It would have been torrential rain that almost immediately evaporated.

Much of this vapor also likely got blown away into space by the same bombardment. But there still would have been a good amount of water left.


So the legends that the oceans boiled away is both true and false. They still exist, just much reduced and under the current city. And they did boil away.

Plus much of the water is likely in use currently. There are trillions and trillions of people living on Terra. Water they excrete will have to be immediately collected and reprocessed. The atmospheric scrubbers likely collect water vapor while excrement and urine is recycled. The water than reenters the distribution system.

 Grey Templar wrote:
Its because of when Horus bombarded the planet during the siege of Terra.

There hadn't been oceans on Earth for thousands of years before Horus was even created.

The fluff is contradictory in that respect. Some say they were gone, others say they were still around.

Pretty much all fluff I read had the oceans gone long before even the Unification Wars.

Boiling away the oceans may not mean the water is completely gone. It could be trapped down in the sumps beneath the continent spanning cities.

They turned it all in to beer?

raekone wrote:
They turned it all in to beer?

To further this explanation after a world wide kegger (which used all he earths water) everyone hopped on their ships for the age of expansion....then peed on other planets thereby reducing the earths water supply to zero
Or maybe they converted it to hydrogen for fuel on space ships meaning it would not be returned to the water table....personally though I will bet on the kegger...

Pretty sure I read some old fluff that stated the oceans had been drained into colossal underground reservoirs in order to make use of more of the Earth's land due to population growth.

Water in the atmosphere wouldn't evaporate into space before the actual atmosphere did too, and unless the water imported for the billions upon billions of people on Terra was also exported as waste after use (unlikely and probably impossible), then it would stay on the planet and you would eventually fill up the seas again simply though generations of recycled urine, sweat and kitchen/laundry use.

Also, it would be virtually impossible to import via space and distribute the daily water needs of Terra. Just think of the logistics.

The real answer is likely some ecological catastrophe caused some of the seas to dry up (just water displacement though really), then humanity drained the (much larger) oceans for industrial use. They'll still exist, somewhere.

The ocean beds still exist, yes. Mankind has built cities in them. Terra in 40K is an ecumenopolis, a city-planet. As such, like all Hive Worlds, it relies on regular shipments of food and water to survive. I seem to recall reading somewhere that Luna was terraformed for that purpose.

 Psienesis wrote:
The ocean beds still exist, yes. Mankind has built cities in them. Terra in 40K is an ecumenopolis, a city-planet. As such, like all Hive Worlds, it relies on regular shipments of food and water to survive. I seem to recall reading somewhere that Luna was terraformed for that purpose.

Luna being so much smaller than terra could never hope to feed everyone on earth.

Also Luna having a 674 hour day wouldn't help you grow food.

It could easily be all aquaculture or synthetic food.

 Exergy wrote:

 Psienesis wrote:
The ocean beds still exist, yes. Mankind has built cities in them. Terra in 40K is an ecumenopolis, a city-planet. As such, like all Hive Worlds, it relies on regular shipments of food and water to survive. I seem to recall reading somewhere that Luna was terraformed for that purpose.

Luna being so much smaller than terra could never hope to feed everyone on earth.

Also Luna having a 674 hour day wouldn't help you grow food.

If only Mankind had experienced a period of time in which their technology was truly wondrous and amazing, capable of performing feats long thought fantastical... a sort of "Golden Age of Technology", if you will.

Alas.

I think that the number one use for water in the grimdark is.... ....people.



We're made of ~90% of the stuff so presumeably thats where the water went?

We're more like 60% water. Let's assume Terra has 900 billion people, average weight is 70kg, meaning each person has around 42kg of water in them. If we multiply 42kg by 900 billion we get 37 800 000 000 000 kg of water. The mass of earths hydrosphere today is about 1 400 000 000 000 000 000 kg, meaning the population would only hold about 2.7% of all the water.

If earth built a huge galaxy spanning empire and used a lot of plastic to construct their materials, a lot of water would be consumed in building all that material.