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Tom Mazanec
2004-May-31, 06:40 PM
What will "naturally" end land life on Earth (no 1000km comets or hyperatomic wars)?
1 Solar luminosity rise?
2 End of plate tectonics?
3 Slowdown of rotation (unlikely IMHO)?
4 Loss of water or air (ditto)?
5 Something I did not think of?

Pi Man
2004-May-31, 07:07 PM
DHMO will eventually kill us, but don't hold your breath.

... or rather, do hold your breath.

wedgebert
2004-May-31, 07:51 PM
I think dying will be the thing that kills off land life.

Nowhere Man
2004-May-31, 08:04 PM
Probably the only thing that would end land life would be the Sun's increase in luminosity. The end of sea life would happen not long after.

The sun will blow up into a red giant and fry the Earth long before your choices 2, 3, or 4 would happen.

Given enough time, plate tectonics would stop, and then all the land would erode away. No land, no land life. But that takes too long.

Fred

TriangleMan
2004-May-31, 08:19 PM
If something completely destroyed the ozone layer would the excess UV radiation destroy all life on land (or destroy key life such as plants that it would cause the eventual extiction of other land life forms)?

Ilya
2004-Jun-01, 02:07 AM
If something completely destroyed the ozone layer would the excess UV radiation destroy all life on land (or destroy key life such as plants that it would cause the eventual extiction of other land life forms)?

No. Higher animals, probably, but not plants or insects. They are much more resistant to UV light. Even for higher animals the main killer would be blindness; all but the largest ones (man-sized or bigger) breed early enough to produce young before onset of lethal cancers.

For that matter, rodents and other small nocturnal animals which hide during day would be safe even from the blinding effects.

Kullat Nunu
2004-Jun-01, 05:58 AM
Well, if Peter D. Ward and Don Brownlee are correct in their book (http://www.amazon.com/exec/obidos/ASIN/0805067817/spaceorspacecomi/104-1099739-7033518), life on land will die due to the lack of carbon dioxide.

Erosion binds CO2 into ground and eventually (in the next 500-1000 million years) CO2 levels will drop so low that plant life becomes impossible. Because there are no more plants to convert CO2 to oxygen, CO2 levels and temperature of the atmosphere will rise rapidly making animal life impossible on the land in the following 100 million years.

HenrikOlsen
2004-Jun-01, 08:21 AM
Well, if Peter D. Ward and Don Brownlee are correct in their book (http://www.amazon.com/exec/obidos/ASIN/0805067817/spaceorspacecomi/104-1099739-7033518), life on land will die due to the lack of carbon dioxide.

Erosion binds CO2 into ground and eventually (in the next 500-1000 million years) CO2 levels will drop so low that plant life becomes impossible. Because there are no more plants to convert CO2 to oxygen, CO2 levels and temperature of the atmosphere will rise rapidly making animal life impossible on the land in the following 100 million years.
Everything dies because we have too much CO2 because we have too few plants because we have too little CO2?
I think there's a major flaw in that reasoning:)
Has anyone ever told these people about feedback loops?
If lower CO2 levels leads to fewer plants, and fewer plants leads to a rise in CO2, then that rise will lead to more plants.

A better reason why binding CO2 in minerals will kill everything might have been that binding CO2 in minerals removes oxygen from the atmosphere so animal life eventually suffocates.
But that takes a minimal knowledge of chemistry to understand, so it doesn't make for a wide appeal "Let's write about how the world will end and make lots of money" book.
It also won't work until the core has frozen enough to stop plate tectonics from recycling the CO2.

Kullat Nunu
2004-Jun-01, 09:11 AM
Everything dies because we have too much CO2 because we have too few plants because we have too little CO2?
I think there's a major flaw in that reasoning:)

After the plants die, one major CO2 absorber is gone. And plants are important factor in erosion, too.
High CO2 levels and the warming Sun finish the job.


Has anyone ever told these people about feedback loops?
If lower CO2 levels leads to fewer plants, and fewer plants leads to a rise in CO2, then that rise will lead to more plants.

And plants increase erosion and ...

They wrote that there will be some fluctiation, as the amount of vegetation rise and fall.

Trend is that CO2 is disappearing from the atmosphere. CO2 levels are lower than in the Paleozoic or Mesozoic era and much lower than in the Precambrian. Some plants like grass are already adapted to that.

I think they know what they are writing about (altough I think they're too pessimistic). I haven't read their previous book Rare Earth but it has similar views (lots of bacterial life, but higher lifeforms are extremely rare).


A better reason why binding CO2 in minerals will kill everything might have been that binding CO2 in minerals removes oxygen from the atmosphere so animal life eventually suffocates.
But that takes a minimal knowledge of chemistry to understand, so it doesn't make for a wide appeal "Let's write about how the world will end and make lots of money" book.

I don't think they're that ignorant of chemistry.

I saw some gross (in my point of view) Bad Astronomy in the later part of the book, but I'm not sure if they're to blame (I didn't like the translation at all, it could be the culprit).


It also won't work until the core has frozen enough to stop plate tectonics from recycling the CO2.

According to them plate tectonics will stop after the oceans have evaporated, which won't happen long after the disappearance of land life.

The main point in that book is that advanced life doesn't survive on any planet for billions of years, but is a rather brief event.

If Earth's lifetime was 12 hours, first multicellural lifeforms appeared at 4 am. Bacterial life will be the most complex form of life again at 5 am. Clock is a bit over 4:30 now, so a bit over half of Earth's "happy hour" is already gone.

glen chapman
2004-Jun-01, 12:07 PM
Ohh dear...we really are not thinking this thing through. First who feels life will remain static for the next billion years? Evolution will continue much as it has today. If higher life is cleaned up by some event, stuff is going to evolve into the vacant niches. Or if the event is extreme enough, evolve into the new niches.

Current land based life does have a fairly grim outlook. As the Sun ages, the deposits of helium ash will cause a steady rise in temperature. Not talking giant phase here, but a steady increase.

What will happen. Life will attempt to adapt, failure will lead to extinction and other more successful animals moving in. The rise of reptiles over amphibians is a classic example of this process.

Success will see creatures we can only guess at. We can assume these creatures will follow the successful body plans already laid down, and fill, within their own evironment the niches animals hold today - Mega fauna etc etc.

So while ever there is material that can be metabolised by an organism...we will have land based life on Earth.

Glen Chapman

Kullat Nunu
2004-Jun-01, 12:40 PM
Ohh dear...we really are not thinking this thing through. First who feels life will remain static for the next billion years? Evolution will continue much as it has today. If higher life is cleaned up by some event, stuff is going to evolve into the vacant niches. Or if the event is extreme enough, evolve into the new niches.

Current land based life does have a fairly grim outlook. As the Sun ages, the deposits of helium ash will cause a steady rise in temperature. Not talking giant phase here, but a steady increase.

What will happen. Life will attempt to adapt, failure will lead to extinction and other more successful animals moving in. The rise of reptiles over amphibians is a classic example of this process.

Success will see creatures we can only guess at. We can assume these creatures will follow the successful body plans already laid down, and fill, within their own evironment the niches animals hold today - Mega fauna etc etc.

So while ever there is material that can be metabolised by an organism...we will have land based life on Earth.

Bacterial life will survive easily for a long time, as it has done before, but we multicellular beings are so fragile. Luckily the changes are so slow that life can adapt to the changing environment. But still there are some absolute limits that any known life form cannot cross, like temperature and amount of water.

It is too easy to say life will just survive, it must be backed with facts. I hope somebody can write similar book with a more optimistic -- and well reasoned -- view.

PS. I've got an impression that often astronomers are over-optimistic and paleontologists over-pessimistic when it comes to complex extraterrestial life.

chirld
2006-Oct-21, 02:41 PM
:dance: [IMG]C:\Documents and Settings\Administrator\My Documents\My Pictures[/[QUOTE][QUOTE]
I think everybody what they have said is right. I like it because form my hometown

chirld
2006-Oct-21, 02:46 PM
I think everybody what they have said is right. I like it because form my hometown

Ronald Brak
2006-Oct-21, 03:13 PM
Well, if Peter D. Ward and Don Brownlee are correct in their book, life on land will die due to the lack of carbon dioxide.

Erosion binds CO2 into ground and eventually (in the next 500-1000 million years) CO2 levels will drop so low that plant life becomes impossible. Because there are no more plants to convert CO2 to oxygen, CO2 levels and temperature of the atmosphere will rise rapidly making animal life impossible on the land in the following 100 million years.

I don't get this at all. CO2 is still going to be released from volcanoes for a lot longer than 100 million years and even if you used a magic spell to remove all the CO2 currently in the atmosphere it would start building up again immediantly from decay enabling many plants to survive. Plants that have access to a constant water supply should be able to get buy on very low levels of CO2. Then there's photosystem I that doesn't require CO2 to generate energy.

Chip
2006-Oct-22, 01:09 AM
Whatever happens, roaches will survive.

Ronald Brak
2006-Oct-22, 04:41 AM
And the mute ants.

Dave Mitsky
2006-Oct-22, 07:22 AM
Only the ones that don't talk? ;)

Dave Mitsky

Ronald Brak
2006-Oct-22, 07:49 AM
Only the ones that don't talk?

Here is a picture of the mute ant looking sad because all his lines got cut.

Edit: That link didn't work. Imagine a sad looking mute ant.

BigDon
2006-Oct-31, 04:29 AM
I thought somebody figured out that as the Sun expands its effective gravity lessens so Earth's orbit will relax outwards enough to keep it from being engulfed? Or will the Sun still be Too Darn Close?

eburacum45
2006-Nov-01, 09:35 AM
No; the effective gravity of the Sun decreases because it loses mass during the red giant phases. During these periods, and the orange sub-giant phases in between, the solar wind increases enough for the Sun to lose significant mass.
http://www-astronomy.mps.ohio-state.edu/~pogge/Lectures/vistas97.html.

Based on the information on that site and elsewhere here is a rough summary of the way I see the future history of Earth's climate;

100-500 years from now; anthropogenic greenhouse effect warms the Earth several degrees, raising sea levels.

1000-1 million years from now; Anthropogenic effects cease (for one reason or another) and Earth reverts to an intermittent ice age.

1 million -100 million years from now; carbon dioxide levels in the atmosphere decrease as carbon is deposited in rocks; this is the overall current trend. Earth becomes a snowball world, intermittently thawed by CO2 buildup from volcanic activity.

100 million years -3 billion years from now; the increasing luminosity of the Sun thaws out the Snowball Earth; but CO2 levels remain low, so plant life must adapt or die. I suspect it will adapt.

3 billion years -5 billion years; the Sun is so luminous that Earth loses all its water and becomes like Venus; life may survive in the upper atmosphere.
(this is based directly on the 'Once and Future Sun' link given above).

5 billion years and on- Earth is first a cinder, then a frozen world orbiting a white dwarf.

Using extreme technology I believe we could maintain a habitable environment on our planet right up to the red giant phase; but after that we would probably have to live on Triton or Sedna, or skip about from world to world as the luminosity goes up and down.

greenfeather
2006-Nov-08, 01:30 AM
Trend is that CO2 is disappearing from the atmosphere. CO2 levels are lower than in the Paleozoic or Mesozoic era and much lower than in the Precambrian. Some plants like grass are already adapted to that.


C02 is disappearing?? What about all the C02 us humans are putting into the atmosphere?? I thought that was a major problem. I thought my cause in life was to produce LESS c02, by for instance not ever burning anything and not supporting the Burning Man Festival??

greenfeather
2006-Nov-08, 01:33 AM
It is too easy to say life will just survive, it must be backed with facts. I hope somebody can write similar book with a more optimistic -- and well reasoned -- view.

Me too. Learning about the Universe is getting me pretty depressed. :( We're all gonna die/become extinct. It's all dangerous & pointless. :sad: Anyone know something cheery?

Van Rijn
2006-Nov-08, 02:11 AM
Me too. Learning about the Universe is getting me pretty depressed. :( We're all gonna die/become extinct. It's all dangerous & pointless. :sad: Anyone know something cheery?

What is so depressing? I fully expect that what we think of as "humans" will cease to exist at some point in the future, but I think it quite likely that there will be something that remembers us as their ancestors. Actually, I'd be quite sad if we never changed or developed.

In the extreme long run it currently looks like the universe will grow dark and thin, but (a) it is hard for me to worry about things that far in the future, long after our sun fades away and (b) we haven't learned everything yet.

tofu
2006-Nov-08, 07:17 PM
Anyone know something cheery?

We have the brains to understand this stuff and to develop the technology to survive - the only thing we lack is nature to cooperate, at least, some of us lack that.

Imagine what life is like for your dog, who has no clue why things happen to him. He gets sick, he can't possibly know why. There's a fire, he's afraid, he doesn't even know what fire is. For all he knows it's a demon chasing him. He sees lights, but it means nothing, so he starts to cross the road and gets hit by a car. Sounds like a pretty terrible life to me.

Just the ability to understand should cheer you up considerably.

MaDeR
2006-Nov-08, 09:30 PM
Me too. Learning about the Universe is getting me pretty depressed. :( We're all gonna die/become extinct. It's all dangerous & pointless. :sad: Anyone know something cheery?
While is no higher sense or purpose in life, you can create this for yourself. You're alive here and now. Is it not sufficiently wonderful?

greenfeather
2006-Nov-09, 01:06 AM
Just the ability to understand should cheer you up considerably.

I'm not sure. We can see a disaster coming and know what will happen, but probably can't do anything about it. The dinosaurs didn't know what was coming & they were happy right up until the big barbecue. As for us...we read articles like "in 50 years we'll need another Earth." So that makes us miserable for our remaining 50 years. We can't enjoy things like the above mentioned Burning Man festival or a trip to the shore because we know how much fossil fuel we're burning. In fact, some of us won't have children because we don't know if there'll be a planet for them. (Although, maybe if enough people did that, we'd solve our population crisis, and there Would be an Earth for them.)

Van Rijn
2006-Nov-09, 01:39 AM
I'm not sure. We can see a disaster coming and know what will happen, but probably can't do anything about it.


We do? I don't see any obvious disaster coming. I do see problems (and opportunities) as always.



The dinosaurs didn't know what was coming & they were happy right up until the big barbecue. As for us...we read articles like "in 50 years we'll need another Earth."


And the scientific basis of those articles is . . . ? We would need another earth for what?

Certainly our resource use will change, just as it has already. But there isn't a single modest sized block of iron, aluminum or uranium in the ground, or a tank of oil. Resource use depends on economics, technology and extraction methods.



So that makes us miserable for our remaining 50 years.


I'd suggest that questionable arguments are a poor reason to be miserable.



We can't enjoy things like the above mentioned Burning Man festival or a trip to the shore because we know how much fossil fuel we're burning. In fact, some of us won't have children because we don't know if there'll be a planet for them. (Although, maybe if enough people did that, we'd solve our population crisis, and there Would be an Earth for them.)

Population crisis? There was talk of a population growth crisis in the '70s, but population growth rates aren't what had been projected. There are places in the world with high population growth, but there are also places with negative population growth. In the U.S. a large portion of the growth is due to immigration and fertility is expected to drop as the population ages.


And while additional population presents problems, it also means more scientists and engineers - more science, more technology, more possibilities.

BigDon
2006-Nov-10, 09:25 AM
LOL, Tofu, way to cheer somebody up! "Hey Greenfeather, your sick dog has been hit by a car while being chased by fire demons". And on the down side...

apocalypse_chick
2006-Nov-10, 09:53 AM
who knows really
life will always find a way - isnt that how the saying goes?
im not very versed on the issue, but ive got some comments.
life found a way in the bottom of the deepest oceans by evolving to live off of deep sulphur vents instead of getting energy from the sun. i dont know how this kind of ecosystem would go if the sun ceased to shine, as other results could lead to the ecosystem shutting down, but it has its own energy source which is the basis for life so who knows.
then again the question was land life wasnt it. If organisms have evolved in situations like that in the ocean, why couldnt they evolve in situations like that on land around volcanic vents etc.
another theory is that eventually the earth will come to close to the sun and will go up in flames. not literally but kinda like venus. too hot for anything to live there.

eburacum45
2006-Nov-10, 10:38 AM
Population crisis?
Even an optimist like me can forsee a time when population becomes a problem with no easy solution.

A number of projections of the current demographic trends seem to predict a peak population of about 9 billion by 2070;
here's one
http://www.ncpa.org/sub/dpd/index.php?page=article&Article_ID=7973

after that population will gradually decline. Trouble is, that decline will be temporary, if medical science continues to prolong human life as I expect it will. There is no real reason why haman life expectancy could not be extended to several hundred years; once life expectancy is more than a thousand years or so then death by accident will become the most common cause of death by far.
Assuming a world population of people with very long life expectancies, the population will begin to skyrocket once again, unless the birth rate is severely restricted.
Simple maths; low death rate requires a low birth rate if we want to avoid population increase. And if a low death rate is technically possible, I think it will happen eventually. A world full of long-lived people means a world with very few children.

BigDon
2006-Nov-10, 11:22 AM
eburacum45, ever hear of the Yeast Mold Factor? If you put mold in a sealed petre dish with a nutrient base and just leave it, it doesn't go completely extinct. In almost all cases after the population crashs when the resources are used up it stabilizes at 3% of the maximum initial population. I can see that happening to us. So at what did you say, 9 billon? We'll then die back and stabilize at 30 million world wide. Sounds good to me.

Noclevername
2007-Apr-11, 07:59 AM
Assuming we don't use one of the thousands of possible ways for us to kill ourselves, life on Earth should survive as long as there's an Earth. Land life however is not gauranteed, but something will be squirming here foe a good long time. I think it may possibly even survive solar expansion, as by then we (or our successors) will have found a way to move the planet, and maybe even the wisdom and foresight to actually do it before the first flare touches the surface (not to contrast them with us short-sighted moderns or anything).

Ronald Brak
2007-Apr-11, 08:49 AM
eburacum45, ever hear of the Yeast Mold Factor? If you put mold in a sealed petre dish with a nutrient base and just leave it, it doesn't go completely extinct. In almost all cases after the population crashs when the resources are used up it stabilizes at 3% of the maximum initial population. I can see that happening to us. So at what did you say, 9 billon? We'll then die back and stabilize at 30 million world wide. Sounds good to me.

I dunno. There have been times in the past when people were told to die for the greater good. None of them seemed too thrilled about it.