The meaning of getting to Mars? Your view?

Solar radiation ... will increase by 10% in a billion years.

the oceans will boil away.

Even if one could reflect that radiation, that's the death of the biosphere, too. Plants need that sunlight, and animals need those plants.

Setanta wrote:

Solar radiation ... will increase by 10% in a billion years.

So why not protect against that?

Setanta wrote:

the oceans will boil away.

Not if we prevent the excess light from reaching us.

Setanta wrote:

Even if one could reflect that radiation, that's the death of the biosphere, too. Plants need that sunlight, and animals need those plants.

We would not block all light from reaching Earth. We would only block enough light to keep the temperature under control. The Earth would still receive the normal daily allotment of light that is needed for life to thrive.

The problem is that you have to first grasp that Earth is a mechanical system that has an established feed of solar energy, which it has evolved in tandem with for as long as it has existed.

You also have to realize that you can't just put a bunch of solar shields in orbit around Earth and have them stay there permanently and not break down due to bombardment by xrays, cosmic rays, dust/debris, and other exposure to energy that's they're not shielded from the way they would be if they were closer to sea level.

Chlorophyll has evolved to reflect energy abundantly. It does so to retard/slow the rate at which energy is absorbed by leaves/trunk/branches/soil because everything has to stay hydrated to survive.

Trees and plants also absorb latent heat from their surroundings and warmer cells transport nutrients and grow at a faster rate. So trees/plants are designed/evolved to use the latent waste heat of the environment to grow leaves/canopies that reflect sunlight.

So when you talk about building and launching solar shields around the planet, you are talking about huge quantities of energy that have to be somehow harvested/mined from Earth's energy budget and then used to make and deploy a huge number of artificial solar shields that would need to cover an area greater than that of the Earth at sea level (which is already enormous).

And you can't just build and deploy these shields once and forget about them; you'd have to maintain them the same as you'd maintain a roof or solar array that breaks down and needs repairs and replacement that costs lots of effort, energy, and materials.

I think you should put some effort into thinking about how a forest canopy, whether it's a rain forest or a deciduous forest or a northern boreal forest or an established agricultural orchard maintains itself by growing/dropping seeds, which automatically/naturally sprout and grow to replace their aging parents.

You can't engineer a system that automatically builds and deploys orbital solar shields by absorbing some of the solar energy they are reflecting, so that the net effect of systemic entropy doesn't affect Earth's energy budget.

For argument's sake, let's say you could design such a system and then just 'seed' an automated solar-shield-factory that flies itself around the solar system using only solar power, gathers materials it needs to reproduce itself, and then brings the solar shields back to Earth orbit so that the overall solar shield maintains itself indefinitely without polluting the Earth with unmanageable debris OR depleting the Earth of energy/resources needed to maintain various aspects of the system.

I find that about as likely as the prospect of building a fleet of self-driving cars and automated infrastructure machines that reproduce themselves while maintaining a sustainable infrastructure that keeps humans in harmony with restored/natural climate.

I'm not saying they both aren't interesting prospects to theorize and critically plan/assess; but I think you have to proceed from the restriction that you don't allot Earth's energy to achieving them; because the moment you invent a project/process that taps into Earth's energy budget, you're initiating a pattern of dependency that will be difficult if not impossible to reform over time.

Whenever an industrial/economic pattern is launched and established, eventual reform prospects get thwarted and/or suppressed in the interest of protecting the economic interests that would be interrupted by reforms.

Humans struggle to preserve status quo and avert change, so it doesn't make sense to begin projects that are unsustainable with the intent of reforming them later to become sustainable. New projects should already be sustainable when they are initiated, and otherwise it should be 'back to the drawing board' to make them permanently sustainable and non-harmful from the start.

Sorry. It's difficult to keep track of all the posts in all the threads sometimes.

I don't see what is unsustainable about doing this. It may be a large undertaking. But humanity is capable of large projects.

Not doing it, on the other hand, is highly unsustainable. Life comes to an end on Earth if we don't do it.

What is unsustainable is not protecting the planet from the increase in sunlight. If we don't do that, life starts to come to an end in 500 million years.

Oh my gosh you have a PS4 and you are a gamer!!! I would never ever think you would have one...prejudice and mea culpa! Wink

I really don't understand why people waste time talking to LL.

One enormous advantage of a ring word, say out beyond the asteroids, near the orbit of Jupiter, would be as a place to preserve the wealth and diversity of our biosphere. As (if) humanity begins to spread to the stars, we will need such a resource.

The lesson of wolves in Yellowstone Park is that we need to preserve as much of our biological diversity at possible. Another advantage of a vast ring world would be the ability to create environments that probes have found on distant planets, and introduce Terran life to see how it responds, and to facilitate genetic manipulation. Well out beyond Mars, almost as far as the orbit of Jupiter would be a good region because we could get resources from the asteroids, as well as from the moons of Jupiter and Saturn.

proof of concept for all these "mirrors and rings" would include a density shield like osmium or lead 207.2
Gamma rays, short peiod energy , has a bigger punch than photons or xrays so would plow through mirrors(no matter the angle, it wouldnt reflect just plow). We now enjoy gamma radiation maxima only during solar storms and we havent gotten toxic doses as far as I have read.
When we later experience the sun going through the beginnings of its unstable perio and leading to its brown out. gamma radiation will begin in earnest. Maybe ring things may get us afew hundred million years (I may be just blowing smoke on tha guesstimate), but I dont believe that any increase in gamma radiation is good for our longevity without major shielding. Based on its energy field, Pb needs to be a specific thickness or its of no value. Planets where rad minerals have reached several half lives would provide enough leas for our needs?? Mars or the moon (where bolides can lead us to a small list of the stuff Wed find Pb 210 a well as Pb 207.2.
All thats part of proofs of concept and concept engineering phases.

Irresponsible thinking; or at least it's irresponsible to assume it's feasible without considering the consequences.

Lead and other elements will rain on us but not in BIG CHUNKS . It may be best seen on planets where meteors have landed and contain expended nuke minerals.