[GlentoranMark (OP)]

Humans can survive in Space but can we really live there?

All life seems to depend on other life. Bacteria in our gut for instance digest our food and in turn keep us alive. Start removing links in the food chain and things start to go wrong.

There's a lot of talk of sending humans to Mars. This is feasible but I don't think for the above reasons we could colonise the planet or terraform it. There's just too many variables that can go wrong. Similarly on Earth we are destroying our ecosystem. We almost destroyed the Ozone without knowing but who knows the repercussions of depleted Ozone or other things we as yet don't know about? For this reason I fear for our species and the planet.

Anyone any thoughts on this subject?

Can we really move off the planet and live elsewhere in the Solar System?

[RD]

Humans can survive in Space but can we really live there?

All life seems to depend on other life. Bacteria in our gut for instance digest our food and in turn keep us alive. Start removing links in the food chain and things start to go wrong.

Embryogenesis in microgravity is a problem ... http://www.thenakedscientists.com/forum/index.php?topic=49437

[alancalverd]

Survival on Mars would be a lot easier than survival in space, and colonisation (or recolonisation) should not be dismissed as an impossibility, particularly if we are prepared to import bacteria and plants to build a human-friendly ecosystem.

But it would be a very different ecosystem from anything we are used to. Even assuming we can find enough water, the solar energy input is so low that we would  need to cultivate at least ten times the area needed on earth to support one human. If you then add the requirement to live underground (for warmth) it all becomes quite a significant engineering task with apparently no natural resources to begin with. So we could begin by experimenting on a cold desert on earth. 

[yor_on]

Earth is not a closed micro system. It's communicating with the vacuum (heat regulation for example), as well as the planets, and the universe (EM, Gravity). It's a open, non-linear system, existing in a semi-stable balance. That's what 'tippings' are all about in physics, and in climate science. Those are depicted as the means by which Earth may find a new semi-stable balance, and climate, defined by the whole Earth-system, interacting with itself and the vacuum, etc.

We thought it was 'closed' in the Victorian era, and a lot of the 'geo engineering' on a global scale seems to assume the same. But we're not.

[evan_au]

The Earth is not a "closed" system - but nor is it as "open" as some people would like to believe.
Yes, the Earth is bigger than a human, but in aggregate, 7 Billion humans are affecting our planet.
Some people would like to think that resources are infinite, so they don't need to put a realistic price on them (especially if they come from another country...)

[Phractality]

In a closed system, entropy increases. If Earth were closed, all complexity, such as life, would fade away. What keeps life going is a kind of entropy engine. We receive low entropy light from the Sun and radiate high entropy heat into space. This leaves behind an accumulation of disentropy, or exergy, which takes many forms, including life.
We can't eliminate that entropy cycle by overexploitation of resources, but we can upset the balance enough to tip the system into a new configuration. We can cause the global temperature to rise, so that the thermal radiation of the planet takes away less entropy. When that happens, the entropy of the planet's surface will increase. Greater entropy generally translates as discomfort, suffering and chaos. At least that's what it means for us critters who evolved to fit a cooler climate.

[jeffreyH]

Whether closed or not all the models predicting climate have so far fallen short in predicting the actuality of environmental change. They are getting better but just because the assumptions are now for a worse outcome than originally predicted. We can attempt to colonize another planet but this would be an enormous engineering feat. Who is to say that we don't just foul that one up as well? We procrastinate like experts in the field of procrastination. Intelligent species?

[Ophiolite]

Whether closed or not all the models predicting climate have so far fallen short in predicting the actuality of environmental change. They are getting better but just because the assumptions are now for a worse outcome than originally predicted.

Would you like to provide citations to justify that assertion?

[jeffreyH]

Whether closed or not all the models predicting climate have so far fallen short in predicting the actuality of environmental change. They are getting better but just because the assumptions are now for a worse outcome than originally predicted.

Would you like to provide citations to justify that assertion?

http://en.wikipedia.org/wiki/Global_climate_model
Two sections of relevance.

"For the six SRES marker scenarios, IPCC (2007:7–8) gave a "best estimate" of global mean temperature increase (2090–2099 relative to the period 1980–99) that ranged from 1.8 °C to 4.0 °C. Over the same time period, the "likely" range (greater than 66% probability, based on expert judgement) for these scenarios was for a global mean temperature increase of between 1.1 and 6.4 °C.[24]
Pope (2008) described a study where climate change projections were made using several different emission scenarios.[25] In a scenario where global emissions start to decrease by 2010 and then decline at a sustained rate of 3% per year, the likely global average temperature increase was predicted to be 1.7 °C above pre-industrial levels by 2050, rising to around 2 °C by 2100. In a projection designed to simulate a future where no efforts are made to reduce global emissions, the likely rise in global average temperature was predicted to be 5.5 °C by 2100. A rise as high as 7 °C was thought possible but less likely.
Sokolov et al. (2009) examined a scenario designed to simulate a future where there is no policy to reduce emissions. In their integrated model, this scenario resulted in a median warming over land (2090–99 relative to the period 1980–99) of 5.1 °C. Under the same emissions scenario but with different modeling of the future climate, the predicted median warming was 4.1 °C.[26]"

"In 2000, a comparison between measurements and dozens of GCM simulations of ENSO-driven tropical precipitation, water vapor, temperature, and outgoing longwave radiation found similarity between measurements and simulation of most factors. However the simulated change in precipitation was about one-fourth less than what was observed. Errors in simulated precipitation imply errors in other processes, such as errors in the evaporation rate that provides moisture to create precipitation. The other possibility is that the satellite-based measurements are in error. Either indicates progress is required in order to monitor and predict such changes.[33]"

[jeffreyH]

For ice core information see:

http://cdiac.ornl.gov/trends/co2/lawdome.html

Use the links for graphics and data.

Long range graphs.
http://cdiac.ornl.gov/trends/co2/graphics/lawdome.smooth75.gif
http://cdiac.ornl.gov/trends/co2/graphics/lawdome.gif

[jeffreyH]

From IOWA State University

http://www.meteor.iastate.edu/gccourse/chem/carbon/emissions.html

Figures 7a and 7b show the extent of our dilemma. I worked in the environmental monitoring sector for a number of years so I do know what I am talking about.

[Ophiolite]

I thank you for the link. Perhaps I am rather dull headed, but I fail to see where in your citations it shows that our estimates of the magnitude of global warming and its consequences are getting worse. If anything I could use the data from your first reply to argue that we are becoming more optimistic. Please clarify this for me.

The relevance of your linked graph missed me. The Iowa State discussion is, is it not, in line with IPCC conclusions. So, I remain at a loss to see where the evidence is for your assertion.

I worked in the environmental monitoring sector for a number of years so I do know what I am talking about.

A. I never suggested you didn't know what you were talking about.
B. Your statement verges upon being an Argument from Authority fallacy.
C. I'm really totally indifferent to what you know, except inasmuch as you can transfer that knowledge to me by presenting citations that support your assertion.

[jeffreyH]

I thank you for the link. Perhaps I am rather dull headed, but I fail to see where in your citations it shows that our estimates of the magnitude of global warming and its consequences are getting worse. If anything I could use the data from your first reply to argue that we are becoming more optimistic. Please clarify this for me.

The relevance of your linked graph missed me. The Iowa State discussion is, is it not, in line with IPCC conclusions. So, I remain at a loss to see where the evidence is for your assertion.

I worked in the environmental monitoring sector for a number of years so I do know what I am talking about.

A. I never suggested you didn't know what you were talking about.
B. Your statement verges upon being an Argument from Authority fallacy.
C. I'm really totally indifferent to what you know, except inasmuch as you can transfer that knowledge to me by presenting citations that support your assertion.

The first graph on this page on sea level rise show what I mean.
http://www.skepticalscience.com/climate-models.htm

"Here, the models have understated the problem. In reality the events are all within the upper range of the model’s predictions. There are other examples of models being too conservative, rather than alarmist as some portray them. All models have limits - uncertainties - for they are modelling chaotic systems. However, all models improve over time, and with increasing sources of real-world information such as satellites, the output of climate models can be constantly refined to increase their power and usefulness.

Climate models have already predicted many of the phenomena for which we now have empirical evidence. Climate models form a reliable guide to potential climate change."

The predictions match at the upper range whereas it would be better if they met at the mean. They still produce worthwhile results. Polar ice melting has also exceeded expectations dramatically.

This site discusses effects on migratory species.
http://www.cep.unep.org/news-from-region/climate-change-may-be-hitting-migratory-species-harder-than-we-thought

Overall, considering every factor and impact, we may be understating the nature of the problem. It is important to know by how much. As climate change progresses we need more accuracy. Rather than being too conservative we need to know the accurate extents of change. Forewarned is forearmed.

[yor_on]

Nice to read you Jeffery. The IPCC have constantly adjusted their (subsequent) scenarios upwards, to a worse climate situation, as I remember. That alone is enough to argue your case I think I wonder at what time scale people will have to admit it becoming truly alarming. We think in short time scales, and we do not really notice changes close to us, if they come slow enough. That's why I find statistics such a valuable tool, it show us what otherwise might miss. But at some point I would expect it impossible to ignore, but that will be long after a tipping, as I suspect, and so nearly impossible to do something about.

[yor_on]

As for your question Glentoran?
Don't know, but I think you have a very valid point questioning how we will take with us, and be able to support, the correct 'micro life', for surviving indefinitely in some space ship. It seems as we need a whole Earth to really feel well, and keep healthy I think that will be as it is with climate, the more we search the more we will find us to need to define it.

[CliffordK]

As extended stay on a space ship.  One could recycle everything from urine to excrement.  One wouldn't necessarily need to have the whole variety of micro organisms that are found on Earth.   

Assuming a closed system, one might be able to eliminate most non-flora human pathogens, and thus also reduce the risk of fecal-oral transmission of disease.

One should be able to simulate such a rigidly closed system on Earth (with the addition of gravity), although on a large enough ship, one should be able to create centrifugal gravity.

Mars likely has most of the basic nutrients for life.  Water, Oxygen, Nitrogen, CO₂, plus various minerals.  Although one may need to transport some resources from the poles to the equator.  I find it doubtful the planet will ever be "terraformed", but rather all life will be maintained within greenhouses.  One may, in fact, not choose subterranean living quarters as the conductive heat loss may be too high.  Or, there may not be a big difference between that and a well insulated above-ground structure that only had to deal with radiative heat loss.  A geosynchronous space mirror could help minimize diurnal and seasonal solar energy and heat cycles.  But the size would have to be a large fraction of the size of the colony.

Unlike a space ship, there would be many more planetary resources available for growing and maintaining the colony.  However, each living area would have to be sealed.

[CliffordK]

As to whether Earth is "open" or "closed", that would depend on the definition. 

As mentioned, it receives energy from the sun, and radiates energy to space.

Over millions of years, gigatons, or perhaps teratons of carbon has been sequestered deep below the surface, where it has generally stayed for millions of years, until humans chose to dig it up.  Of course it is a continuing process, and undoubtedly some organisms die on the surface and don't decompose.  Or, perhaps the methyl clathrates deep under the oceans is a form of carbon sequestration, and a precursor to undersea methane and oil deposits.

I believe the oceans have also been slowly increasing in salinity as minerals are washed from the mountains to the sea.  Certainly some dried oceans have left deep underground salt deposits, no longer easily accessible from the surface.

So, as carbon and salt is lost (pre-human history), the Earth acts like an open system.  Of course, humans have figured out how to reverse much of that.