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Actually, he argues the opposite: that the biosphere itself is self-destructive. He points to positive feedback loops, such as the release of oxygen, as an example of one group of organisms poisoning the whole biosphere. He gives others examples, too, such as how it appears that life tends to promote the release of methane and carbon dioxide during warming events and their sequestration during cooling events -- leading, in the former case, to greater warming and, in the latter, to greater cooling than would happen otherwise.

He doesn't trace these problems to monoculture, though he's not praising that either.

Life isn't perfect but it's tenacious smile.gif Like you said, somehow it managed to hang on for 4 billion years or so - must be doing something right.

Though to be fair to Ward, he seems to be arguing that things like the Oxygen Catastrophe -- see http://en.wikipedia.org/wiki/Great_Oxygenation_Event -- are examples of life behaving badly. In this case, a waste product destroyed most of the biosphere. This makes me think there's something to the Medea Hypothesis... And this and other examples do seem to weigh against the Gaia Hypothesis.

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Though to be fair to Ward, he seems to be arguing that things like the Oxygen Catastrophe -- see http://en.wikipedia....ygenation_Event -- are examples of life behaving badly. In this case, a waste product destroyed most of the biosphere. This makes me think there's something to the Medea Hypothesis... And this and other examples do seem to weigh against the Gaia Hypothesis.

Not sure why you (or is it Ward?) characterize the formation of our oxygen atmosphere as "life behaving badly"? This event allowed life to flourish on Earth whereas before it only consisted of probably one or a few kinds of organisms.

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Though to be fair to Ward, he seems to be arguing that things like the Oxygen Catastrophe -- see http://en.wikipedia....ygenation_Event -- are examples of life behaving badly. In this case, a waste product destroyed most of the biosphere. This makes me think there's something to the Medea Hypothesis... And this and other examples do seem to weigh against the Gaia Hypothesis.

Not sure why you (or is it Ward?) characterize the formation of our oxygen atmosphere as "life behaving badly"? This event allowed life to flourish on Earth whereas before it only consisted of probably one or a few kinds of organisms.

I've not gotten to the part of the book where Ward deals with this, but my understanding is oxygen was toxic to most existing organisms and it might have also caused massive glaciation -- the Huronian Glaciation which seems to have lasted about 300 million years. Yes, afterward, life forms did evolve that could handle oxygen, but the point is the immediate outcome was probably very bad for almost all life at that time and probably resulted in a mass extinction event. That millions or ten or hundreds of millions of years later, life started to thrive and flourish under the new conditions seems to ignore this bad outcome.

And this does seem to be what Ward means by a Medean outcome: one where life brought on its own demise and brought about what looks like a biosphere-level collapse. I'll have to read his account -- if he has one; he mentions it early in the book, but I have not yet any detailed theory of his about this -- before deciding if I've rendered this correctly here.

Also, you raise the issue of biodiversity. Ward does go over this early in his book -- when he considers how to measure success at the biosphere level. I hope to go over this later, but I don't think there's a clearcut measure of biosphere success -- though Ward makes a good case for total biomass and diversity. But what happens in one is sacrificed at the expense of the other? E.g., is lower biomass with higher diversity more or less successful than higher biomass with lower diversity? (Also, how to measure biodiversity? Number of species? Number of higher taxa? And one must be careful about trying to measure this from the fossil record as it selectively preserves according to what's easy to preserve and is also known from what's easy to recover. Of course, this problem woulkd plague any account -- pro-Medean, pro-Gaian, or other -- of this, no?)

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The thing is it wasn't just life involved in this process, there were huge geochemical factors as well. The early microorganisms were actually terra-forming as well. This resulted in tremendous upheavals like snowball earths as the eco-system gradually stabilized into what we have now. This sort of goes with my argument about how long it takes to establish life on a planet because terra-forming a young planet is a huge undertaking that takes billions of years, assuming it must happen similarly throughout the universe. One has to assume the same elements and chemistry will be operating elsewhere in the universe.

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The thing is it wasn't just life involved in this process, there were huge geochemical factors as well.

I agree that it involved abiotic factors, but the actual production of oxygen in large quantities seems to have caused by some living organisms. (And, to be sure, anything life does, especially on a large scale and over long spans of time, is likely going to involve abiotic -- e.g., geochemical -- factors.)

The early microorganisms were actually terra-forming as well.

It's only "terra-forming" from the perspective of the life that later evolved -- not from the life that was dominant then. In fact, it's likely many of the organisms that originally gave off oxygen poisoned themselves in the process. This would be, in some ways, little different than, say, a closed biome where the plants and animals poison themselves to death and a few years later you note that it's dominated by certain bacteria (and not others that went down soon after the plants and animals died out) and then you proclaim that these bacteria have "terra-formed" the biome when it fact it's really that the plants and animals destroyed themselves and the bacteria merely benefited from this.

This resulted in tremendous upheavals like snowball earths as the eco-system gradually stabilized into what we have now.

I'm not sure the outcome was stable. Perhaps the largest known mass extinction -- the End Permian one around 251 million years ago -- came about well after the Huronian Glaciation and the two known Snowball Earths. That one might have been a Medean event -- i.e., biotically caused.

Also, since then, there seem to have been huge upheavals in eco-systems. Think of the whole Mezozoic and Cenozoic Eras from what's known from their fossil records. These seem to have involved massive changes in ecosystems and, of late, ice ages. (Of course, these changes might not all be Medean, particularly the ice ages.)

This sort of goes with my argument about how long it takes to establish life on a planet because terra-forming a young planet is a huge undertaking that takes billions of years, assuming it must happen similarly throughout the universe. One has to assume the same elements and chemistry will be operating elsewhere in the universe.

You'd also have to assume the same starting points and paths, which seems very unlikely. Yes, the chemistry and same elements are likely, but the not the particular initial conditions and histories.

And, again, I'd caution against thinking in terms of terraforming as here it seems to bring up the image of life transforming a planet into a world better suited for future life -- rather than what Ward would argue is more likely: past life unintentionally bringing about its own demise and afterward some other life adapting to the denuded environment caused by this. It also ignores that abiotic factors might have played a bigger role. E.g., the Earth cooled after its formation -- which seems abiotic. Carbon dioxide released from geological processes also seems to have prevented Snowball Earths -- until living things started removing carbon dioxide from the atmophere. The latter seems to have almost killed off life. (It's easy to imagine had boundary conditions been slightly different, a Snowball Earth might freeze over for good -- maybe, at best, having a remnant biosphere near volcanic vents or deep in the crust, but leaving the rest of the planet a vast icy desert.)

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I agree that it's only "terra-forming" from our perspective, but I also think that this would be outcome of the whole bio-geochemistry process on most any planet. Also why would you think that other planets would have different initial conditions? Don't you think planets (suitable for life) would all be formed in more or less the same way?

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I agree that it's only "terra-forming" from our perspective, but I also think that this would be outcome of the whole bio-geochemistry process on most any planet. Also why would you think that other planets would have different initial conditions? Don't you think planets (suitable for life) would all be formed in more or less the same way?

Consider the now decades old discovery of extremophiles. Also, consider the discovery of places throughout the solar system that seem very similar to conditions that known extremophiles seem to survive if not flourish under -- places like parts of Mars, Titan, Europa, and Enceladus. This makes me think whatever's necessary to give rise to life is a range of conditions that might be found in a range of places. (It might also be, as some have speculated for a long time now, that life arises in one place -- say, inside comets -- and merely finds its way to planets like Earth. The same might go for life originated on one world and then being transported to another via, say, an impactor -- as some have speculated might have happened with Earth.) Of course, this is speculation and we don't know what gives rise to life in the first place. There are some good guesses, I admit, but it seems these guesses weigh in favor of a broader range of initial conditions...

It also seems, from the solar system findings, that the range of conditions suitable for life -- at least for extremophile-like life -- is found in a broader range of places than just planets exactly like Earth.

And, aside from this, let's just imagine your right about part of this picture: for technological civilizations to arise, they have to have conditions much like Earth now -- e.g., high oxygen levels and similar temperature profiles to Earth's. This still doesn't mean every world that gives rise to a technological civilizations would have to start out just like Earth and go through exactly the same history. Don't you agree?

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Consider the now decades old discovery of extremophiles. Also, consider the discovery of places throughout the solar system that seem very similar to conditions that known extremophiles seem to survive if not flourish under -- places like parts of Mars, Titan, Europa, and Enceladus. This makes me think whatever's necessary to give rise to life is a range of conditions that might be found in a range of places. (It might also be, as some have speculated for a long time now, that life arises in one place -- say, inside comets -- and merely finds its way to planets like Earth. The same might go for life originated on one world and then being transported to another via, say, an impactor -- as some have speculated might have happened with Earth.) Of course, this is speculation and we don't know what gives rise to life in the first place. There are some good guesses, I admit, but it seems these guesses weigh in favor of a broader range of initial conditions...

It also seems, from the solar system findings, that the range of conditions suitable for life -- at least for extremophile-like life -- is found in a broader range of places than just planets exactly like Earth.

And, aside from this, let's just imagine your right about part of this picture: for technological civilizations to arise, they have to have conditions much like Earth now -- e.g., high oxygen levels and similar temperature profiles to Earth's. This still doesn't mean every world that gives rise to a technological civilizations would have to start out just like Earth and go through exactly the same history. Don't you agree?

My guess is that life and the planet have to evolve together. A planet already billions of years old could probably not be populated by an organism from somewhere else, unless it was engineered by intelligent life (terraforming). So if the ecosystem is going to evolve it has to start at a very rudimentary stage, albeit not exactly the same as Earth. But there are physical restraints, like the mass of the planet needs to be large enough to keep the atmosphere from drifting off into space for example and as you mentioned, moderate temperatures and pressures etc. (Mercury is too close to the sun and has wild temperature variation)

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I agree that it's only "terra-forming" from our perspective, but I also think that this would be outcome of the whole bio-geochemistry process on most any planet. Also why would you think that other planets would have different initial conditions? Don't you think planets (suitable for life) would all be formed in more or less the same way?

Consider the now decades old discovery of extremophiles. Also, consider the discovery of places throughout the solar system that seem very similar to conditions that known extremophiles seem to survive if not flourish under -- places like parts of Mars, Titan, Europa, and Enceladus. This makes me think whatever's necessary to give rise to life is a range of conditions that might be found in a range of places. (It might also be, as some have speculated for a long time now, that life arises in one place -- say, inside comets -- and merely finds its way to planets like Earth. The same might go for life originated on one world and then being transported to another via, say, an impactor -- as some have speculated might have happened with Earth.) Of course, this is speculation and we don't know what gives rise to life in the first place. There are some good guesses, I admit, but it seems these guesses weigh in favor of a broader range of initial conditions...

It also seems, from the solar system findings, that the range of conditions suitable for life -- at least for extremophile-like life -- is found in a broader range of places than just planets exactly like Earth.

And, aside from this, let's just imagine your right about part of this picture: for technological civilizations to arise, they have to have conditions much like Earth now -- e.g., high oxygen levels and similar temperature profiles to Earth's. This still doesn't mean every world that gives rise to a technological civilizations would have to start out just like Earth and go through exactly the same history. Don't you agree?

Terrific post, Dan. People are biased toward looking at the complex, autocatalytic reactions and circumstances that happen under Earth-like conditions. We don't have as much experience with observations and experiment in other environments.

Jim

Edited by James Heaps-Nelson
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Actually, I mentioned this recently somewhere, but one theory about the Earth and moon is that THEY collided and the Earth got quite a bit bigger than Mars, for example. This allowed it to keep it's atmosphere and subsequently life flourished. Now THAT might be an extremely rare event in the development of a solar system which in itself could eliminate countless systems from having life. But given that it does flourish, my argument to you would be that there are too many extinction events in the early stages of planet and life evolution for the sustained evolution required for intelligence to emerge.

The current hypothesis that Earth-1 collided with a Mars size planet Way Back When. The result was Earth-2 (the one we currently live on) plus enough debris to stick together and become our moon. If Earth-2 had not been made by an accident it is unlikely that intelligent life would have evolved on Earth-1 since it did not have enough mass to hold onto its atmosphere.

Ba'al Chatzaf

Mars has only about 1/10 the mass of earth. So even if an entire Mars size planet were to collide with earth and merge with it into a single planet, this would only increase the total mass of the new earth planet by about 10%. Would the earth with 10% less mass than it has presently be unable to hold onto its atmosphere? Venus it about 20% less massive than earth and has an atmosphere that is about 100 times thicker than earth's. Of course, Venus's atmosphere is mostly carbon dioxide, which is a much heavier gas than oxygen and nitrogen, so Venus might be unable to hold onto an oxygen/nitrogen atmosphere like is found on earth.

Martin

Martin

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Consider the now decades old discovery of extremophiles. Also, consider the discovery of places throughout the solar system that seem very similar to conditions that known extremophiles seem to survive if not flourish under -- places like parts of Mars, Titan, Europa, and Enceladus. This makes me think whatever's necessary to give rise to life is a range of conditions that might be found in a range of places. (It might also be, as some have speculated for a long time now, that life arises in one place -- say, inside comets -- and merely finds its way to planets like Earth. The same might go for life originated on one world and then being transported to another via, say, an impactor -- as some have speculated might have happened with Earth.) Of course, this is speculation and we don't know what gives rise to life in the first place. There are some good guesses, I admit, but it seems these guesses weigh in favor of a broader range of initial conditions...

It also seems, from the solar system findings, that the range of conditions suitable for life -- at least for extremophile-like life -- is found in a broader range of places than just planets exactly like Earth.

And, aside from this, let's just imagine your right about part of this picture: for technological civilizations to arise, they have to have conditions much like Earth now -- e.g., high oxygen levels and similar temperature profiles to Earth's. This still doesn't mean every world that gives rise to a technological civilizations would have to start out just like Earth and go through exactly the same history. Don't you agree?

My guess is that life and the planet have to evolve together. A planet already billions of years old could probably not be populated by an organism from somewhere else, unless it was engineered by intelligent life (terraforming).

I disagree and think there's a strong analogy with colonization events on Earth here. In fact, many evolutionarily important colonizations seem to be "fish out of water" events where some organisms are chucked into an environment they can only just barely survive in and their descendants end up adapting to. This was probably the case for the first land animals -- both from the arthropod and vertebrate lines.

So if the ecosystem is going to evolve it has to start at a very rudimentary stage, albeit not exactly the same as Earth. But there are physical restraints, like the mass of the planet needs to be large enough to keep the atmosphere from drifting off into space for example and as you mentioned, moderate temperatures and pressures etc. (Mercury is too close to the sun and has wild temperature variation)

But those constraints are likely to be much wider than you think. E.g., it seems at this time that some Earth life could survive on Mars, Titan, Europa, Enceladus, and likely many other places in the solar system. From known processes and without human intervention, it's quite possible for terrestrial life to be moved to some of these places -- though the odds are low...

However, low odds plus a long time and many, many cases might equal this happening often enough. Think of transport of microbial life from one planet to another via impactors. I believe I read an estimate that such a transport from Mars to Earth would happen successfully once about every ten million years. For the opposite journey, I believe the odds were much lower -- an order of magnitude lower, but that would still be about once every hundred million years. That's mean, if we assume microbial life has existed on Earth for about the last 3.8 billion years (one current estimate), that it's possible for some of it to have made it to Mars via impact roughly forty times. And the journey from Mars to Earth would be, assuming the estimate offered here is correct, on the order of several hundred times during the same period. Now, imagine hundreds or thousands of worlds like this -- which seems a low estimate for how many similar planets there are in the galaxy.

Plug this back into the rest of my argument. You don't need, in my view, life to coevolve in one environment for billions of years. One can imagine it colonizing from another environment -- here, another planet -- via some non-technological process, such as planetary mass exchange. And even if the odds of such successful mass exchange are low -- the microbes have to be knocked off one planet, survive the journey through space, and then live through crashing into another planet, and find the new world at hospitable enough to barely survive on.

Also, the sort of Medean events discussed in Ward's book have made Earth, if he's right, a fairly inhospitable place. The life forms that came after a Medean event are not necessarily, too, life forms that could survive through one. Think of it this way, to borrow and alter a metaphor from Nicholas Nassim Taleb, imagine a room full of a thousand people where there's a giant Russian roulette game going on. In this case, the gun is set to kill 999 out of the thousand people in the room. The one person surviving this event is not really adapted to win at Russian roulette. She or he is just lucky. Add to this, her or his descendants are unlikely to have Russian roulette adaptations.

In a similar fashion, Earth life that survives through a mass extinction event, such as the Late Devonian one (which Ward covers in chapter five of his book, but I haven't gotten that far yet), might latter evolve into life that would have no better chance of surviving through a similar event. Even setting Ward's book aside, just think of the Mesozoic Era itself. Had I been around during the Permian Period and making predictions, I'd have said the mammal-like reptiles and their descendants would probably be the dominant species on the planet. Sure enough, I'd be right for our time, but I'd have been wrong for the whole Mesozoic Era, which lasted from 251 million years ago to about 65.5 million years ago -- a time almost three times longer than when the mammal-like reptiles descendants (i.e., the mammals) actually came to dominate the planet. (Of course, mammal-like reptiles and mammals were around during the Mesozoic and it seems they were not the minor players there were once thought to be, but it still seems this was the Age of the Dinosaurs more than a preparation for mammalian diversification.)

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Consider the now decades old discovery of extremophiles. Also, consider the discovery of places throughout the solar system that seem very similar to conditions that known extremophiles seem to survive if not flourish under -- places like parts of Mars, Titan, Europa, and Enceladus. This makes me think whatever's necessary to give rise to life is a range of conditions that might be found in a range of places. (It might also be, as some have speculated for a long time now, that life arises in one place -- say, inside comets -- and merely finds its way to planets like Earth. The same might go for life originated on one world and then being transported to another via, say, an impactor -- as some have speculated might have happened with Earth.) Of course, this is speculation and we don't know what gives rise to life in the first place. There are some good guesses, I admit, but it seems these guesses weigh in favor of a broader range of initial conditions...

It also seems, from the solar system findings, that the range of conditions suitable for life -- at least for extremophile-like life -- is found in a broader range of places than just planets exactly like Earth.

And, aside from this, let's just imagine your right about part of this picture: for technological civilizations to arise, they have to have conditions much like Earth now -- e.g., high oxygen levels and similar temperature profiles to Earth's. This still doesn't mean every world that gives rise to a technological civilizations would have to start out just like Earth and go through exactly the same history. Don't you agree?

Terrific post, Dan. People are biased toward looking at the complex, autocatalytic reactions and circumstances that happen under Earth-like conditions. We don't have as much experience with observations and experiment in other environments.

Jim

Thanks. I think some people are so biased. The problem is, again, generalizing from one example. It's like trying to figure out the slope of a line from one point.

Edited by Dan Ust
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This would perhaps have a better home on a Fermin Paradox topic... It links up to some things we've discussed here:

Animals Living Without Oxygen Discovered for First Time

http://www.livescience.com/animals/metazoan-loriciferans-ocean-100407.html

More work needs to be done to see if these animals are from a line that never used oxygen or had mitochondria or if their line merely lost these over time.

Comments?

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  • 4 weeks later...

MSK: Spammer.

Let us see. Fast vehicle we have ever launched goes fifty thousand miles an hour. Humans live about seventy five years (give or take). How many hours in seventy five years? Multiply by fifty thousand and you have it.

I am sure the technology will improve somewhat, but not much.

Ba'al Chatzaf

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MSK: Spammer.

Let us see. Fast vehicle we have ever launched goes fifty thousand miles an hour. Humans live about seventy five years (give or take). How many hours in seventy five years? Multiply by fifty thousand and you have it.

I am sure the technology will improve somewhat, but not much.

Ba'al Chatzaf

The fastest "man-rated" vehicle is much slower, of course.

By the way, I believe the fastest spacecraft actually topped out at over 100,000 mph back in the 1970s: the US space probe Mariner 10. If you use the right tricks, you can get up to pretty high speeds. Of course, the spacecraft in question was going to the inner solar system and was not heading out from there.

Edited by Michael Stuart Kelly
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As I understand it a manned spacecraft at maximum tolerable g forces would take a lifetime of constant acceleration just to get near the speed of light.

We're already on a spaceship. Why jump into a tin can except for local work?

--Brant

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As I understand it a manned spacecraft at maximum tolerable g forces would take a lifetime of constant acceleration just to get near the speed of light.

We're already on a spaceship. Why jump into a tin can except for local work?

--Brant

So you can go to places other than where the Earth is going.

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As I understand it a manned spacecraft at maximum tolerable g forces would take a lifetime of constant acceleration just to get near the speed of light.

My back of the napkin non-relativistic calculation for a one gee -- very tolerable since that's what humans spend almost their whole lives living with -- acceleration gets the spacecraft near light speed in about 354 days. Where did you get the lifetime figure from?

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As I understand it a manned spacecraft at maximum tolerable g forces would take a lifetime of constant acceleration just to get near the speed of light.

We're already on a spaceship. Why jump into a tin can except for local work?

--Brant

Because in several billion years the sun may expand and become a red giant and absorb the nearest planets. We have to get ready! :)

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As I understand it a manned spacecraft at maximum tolerable g forces would take a lifetime of constant acceleration just to get near the speed of light.

My back of the napkin non-relativistic calculation for a one gee -- very tolerable since that's what humans spend almost their whole lives living with -- acceleration gets the spacecraft near light speed in about 354 days. Where did you get the lifetime figure from?

Oh, I read it somewhere. Isn't 1 gee standing still?

--Brant

blush

Edited by Brant Gaede
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As I understand it a manned spacecraft at maximum tolerable g forces would take a lifetime of constant acceleration just to get near the speed of light.

My back of the napkin non-relativistic calculation for a one gee -- very tolerable since that's what humans spend almost their whole lives living with -- acceleration gets the spacecraft near light speed in about 354 days. Where did you get the lifetime figure from?

Oh, I read it somewhere. Isn't 1 gee standing still?

--Brant

blush

One gee is an acceleration of around 9.8 meters per second per second. (Standing still is meaningless here as we're talking about acceleration -- changes in velocity -- and not velocity itself. Let's leave alone that standing still would be with respect to some reference frame.)

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As I understand it a manned spacecraft at maximum tolerable g forces would take a lifetime of constant acceleration just to get near the speed of light.

We're already on a spaceship. Why jump into a tin can except for local work?

--Brant

Because in several billion years the sun may expand and become a red giant and absorb the nearest planets. We have to get ready! smile.gif

If Ward is correct, the biosphere itself will make this planet untenable much sooner -- in about 100 million years or so.

However, there are much more immediate threats to human life and civilization -- from things like asteroid impacts and supervolcanoes to WMDs.

But even if it weren't for those, what's wrong with getting off world? What's wrong with just the pure urge to explore and travel? (This reminds me of someone who responded to Rothbard's view of space exploration. I believe it was Schulman who said something along the lines of Rothbard viewing space not as almost the entire universe -- like 99.99999999% of everywhere that we know of -- but as something along the lines of a small closet in New Jersey that only perverts would want to get into.)

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