First habitable planet....

@DeepThought
How are we going to have that billion years considering every species goes extinct eventually and that would be measured in millions of years not billions.
The only way we could live a billion years from now is to put folks on a spacecraft going within a hair's breath of c and basically shoving that ship into the future, fly a billion ly and you would be a billion years from now at your destination. Even if it was a ship going around the galaxy in circles instead of going a billion ly away from us.
I suppose if we had that kind of capability, we could send ships into the future and come back to Earth every million years or so and repopulate Earth like that but I think in that scenario, the next ship to get here a million years later would find Earth without humans each time that cycle happened.

@sonhouse said
@DeepThought
How are we going to have that billion years considering every species goes extinct eventually and that would be measured in millions of years not billions.
The only way we could live a billion years from now is to put folks on a spacecraft going within a hair's breath of c and basically shoving that ship into the future, fly a billion ly and you would be a bi ...[text shortened]... hip to get here a million years later would find Earth without humans each time that cycle happened.

That figure is based on the sun becoming hotter as it ages. The projection is that in slightly under 1 billion years the Earth will not sustain eukaryotic life unless the Earth's orbital radius increases to compensate. This is the SciShow episode I was on about in my previous post. The video's about 12 minutes long and designed for a non-technical audience.

YouTube

@humy said
Like what?
Remember, robots and AI are improving all the time and whatever currently cannot be done with robots/AI that can be done by humans can always be more cost effectively be dealt with by doing research and development into robots/AI specifically for doing that thing rather than send people in space to do it.
Already unmanned probes and robots have done far more for the science discoveries than manned missions and with far far greater cost effectiveness.

Innovation for one. Manned space exploration has already led to countless innovations that may not exist if we were not facing the unique challenge. Materials science, computing, power generation and storage, food, recycling etc etc. What is required for self-sustaining support, miniaturization, lightweight, increased power efficiency, etc.

Biologically, we have learned a lot about aging, bone and muscle growth, hearing and vision, from microgravity environments.

There's also the inspiration piece. Science is capable of doing big things, not just sending a Roomba to Mars. Manned exploration of space has the potential to elucidate new solutions to complex global challenges.

@wildgrass said
Innovation for one. Manned space exploration has already led to countless innovations that may not exist if we were not facing the unique challenge.

If a challenge is unique and expensive and avoidable then, rather than spend money innovating for it, it would make more sense to save that money for better and more useful things by avoiding that unique challenge. There is no great need to send people in space but, in contrast, there are various great needs here on Earth we could better spend that money on dealing with.

Materials science, computing, power generation and storage, food, recycling etc etc.
...
Biologically, we have learned a lot about aging, bone and muscle growth, hearing and vision, from microgravity environments.

I have seen no evidence that any of those things on Earth have been improved in significant ways by manned missions. I am sure if any of those things were improved by manned missions then they could have been improved with vastly less cost and danger here on Earth without sending someone into space. Most if not vertually all of those improvements have come from research conducted here on Earth without involving sending people into space and, with the same amount of money spent on that same kinds of research but without sending someone to outer space, greater and better breakthroughs are likely because much less money will be spent on sending people to space and space life support equipment etc. and more of the money will be spent on the kind of things that would more likely lead to breakthroughs, such as building labs and doing experiments etc.
If you are trying to make a breakthrough in, say, water purification methods, the most cost effective and efficient way to do that by far would be to figure out how to do it on planet Earth and without sending somebody into space.

There's also the inspiration piece.

I have seen no evidence nor know any reason to believe that putting somebody in space generally would give inspiration to people to do more of the useful things here on Earth in particular.

@deepthought said
That figure is based on the sun becoming hotter as it ages. The projection is that in slightly under 1 billion years the Earth will not sustain eukaryotic life unless the Earth's orbital radius increases to compensate. This is the SciShow episode I was on about in my previous post. The video's about 12 minutes long and designed for a non-technical audience.

https://www.youtube.com/watch?v=sy8l0jkIeQ4

I watched that youtube and it gave me an idea for how we could live long after bright stars like our sun have burned themselves out and we are left with brown dwarfs; rather than use energy from the brown dwarfs which as I understand it would be very problematic, we could develop a more advanced form of fusion power on the surface of our chosen planets that uses not just hydrogen but even common elements in the rocks such silicon etc. We could generate so much of it that way that the waste heat could be used to heat the whole biosphere of the planet to a comfortable 20C and we could even use it to power giant bright electric lights suspended high in the air shining down and designed to give the illusion of being the sun during an artificial daytime. I admit I haven't done the calculations but if the fusion power uses common elements of rocks then, even with this high rate of nuclear consumption, taking into account we can mine a few kilometers down into the planet's crust, I assume this could last us many billions of years?
I understand fusion power using hydrogen is hard enough and for heavier elements such as silicon we will need much higher temperatures to make that work making it even harder to develop.

@humy said
If a challenge is unique and expensive and avoidable then, rather than spend money innovating for it, it would make more sense to save that money for better and more useful things by avoiding that unique challenge. There is no great need to send people in space but, in contrast, there are various great needs here on Earth we could better spend that money on dealing with.
[quote ...[text shortened]... erally would give inspiration to people to do more of the useful things here on Earth in particular.

I understand your point, but practically speaking if you are doing things that are already done you are not innovating. Its true that it would be cheaper if we never went to the moon but invented all those cool things anyway. But the inspiration for those inventions would not have existed if not faced with that unique challenge. Books have been written detailing how many people chose scientifically oriented careers because of Apollo. They were trying to do things that had never been done and, through a lot of serendipity, learned a lot of other extremely interesting and important things along the way. The complexity of manned space travel was the driver. I don't have the reference off-hand, but there was a huge spike in Apollo-inspired Ph.Ds too.

I have seen no evidence that any of those things on Earth have been improved in significant ways by manned missions.

Surely you can appreciate the innovations in computing technology that came about because of Apollo in the 60's. But also...
Ever heard of the Dust Buster?
https://science.howstuffworks.com/innovation/nasa-inventions/nasa-change-cleaning1.htm

Radiant barrier insulation? The Jaws of Life? Foil blankets? Nike Air shoes?

https://gizmodo.com/the-brilliant-but-absurd-history-of-nike-air-technology-1741712594

@wildgrass said
the inspiration for those inventions would not have existed if not faced with that unique challenge.

I don't know of any reason to think those or similar inventions would never come to exist without such an unique challenge.
I don't know of any reason to think that the rate of inventiveness among people on Earth globally would generally have been any less if that same amount of money was spent on other things other than putting people into space.
If we hadn't send anyone into space but spent all that money on more Earth-bound challenges then history would have taken at least a slightly different course and probably some of those particular EXACT things wouldn't have been invented by now but then other things would have been invented instead and I have no reason to think those other things would be any less good.

@deepthought said
That figure is based on the sun becoming hotter as it ages. The projection is that in slightly under 1 billion years the Earth will not sustain eukaryotic life unless the Earth's orbital radius increases to compensate. This is the SciShow episode I was on about in my previous post. The video's about 12 minutes long and designed for a non-technical audience.

https://www.youtube.com/watch?v=sy8l0jkIeQ4

All well and good but it is extremely more likely humanity will be extinct long before we need to worry about the planet cooking. Maybe some new intelligence will evolve out of squids or some such by then also able to do spaceflight.

@sonhouse said
All well and good but it is extremely more likely humanity will be extinct long before we need to worry about the planet cooking. Maybe some new intelligence will evolve out of squids or some such by then also able to do spaceflight.

Planet of the Squids.

In defense of the squid, they are currently unable to conduct spaceflight. We know how to do it but choose not to.

@humy said
I don't know of any reason to think those or similar inventions would never come to exist without such an unique challenge.
I don't know of any reason to think that the rate of inventiveness among people on Earth globally would generally have been any less if that same amount of money was spent on other things other than putting people into space.
If we hadn't send anyone into ...[text shortened]... have been invented instead and I have no reason to think those other things would be any less good.

I don't know about all those elaborate hypotheticals. Most likely, if the US wasn't pouring so much money into spaceflight science in the 60's they'd have just spent the money on weapons. Lots and lots of weapons. I know those things exist as a direct result of the Apollo program, and they made the terrestrial world a better place. Especially the DustBuster.

This sounds like the old "We'd know about relativity without Einstein, so what'd we need him for?" argument. Same with Copernicus and Newton for that matter.

We'd unite the world with a manned trip to Venus. Undoubtedly there'd be innovations that make mankind more efficient and advanced. Undoubtedly there'd be serendipitous findings. I have no doubt that it would inspire a new generation of engineers, astronauts and biologists who dream about something greater than incremental "make this cell phone work slightly better" kind of science. Isn't that worth it?

@pawnpaw said
@wildgrass
I think the space agencies of the various countries must combine efforts to establish a human base on the moon. That's the closest to earth, and cost won't be too high. Then, if a disaster of some epic proportions strike the earth, that's the place to escape to. After whatever happened simmers down, we can repopulate the earth and start over again.
Except if the occurance also affects the moon...

That'd be so cool. Next stop, Titan.

@deepthought said
It's not entirely obvious to me what the point of manned space missions are. GPS satellites have an obvious use, the Hubble Space telescope and its successors are all useful missions. The dangers involved in space travel go beyond the immediate risk to a persons life if there's a fire, sudden depressurization, or problems during fast re-entry; although they've learnt a ...[text shortened]... issues connected with radiation and so forth. So manned space missions need a lot of justification.

Do you think Apollo was well-justified?

@wildgrass said
Do you think Apollo was well-justified?

Well I do but I am biased by the fact I worked on Apollo, Apollo tracking and timing. We got a lot more out of Apollo than we did for the Manhattan project.

@sonhouse said
Well I do but I am biased by the fact I worked on Apollo, Apollo tracking and timing. We got a lot more out of Apollo than we did for the Manhattan project.

I agree. Much of it was serendipitous. A world without tang is undeniably worse.

Without the Soviets, though, none of it would have happened.

@sonhouse said
1 g for 1 year = the speed of light.

Not to question you, yes, I know you worked at NASA and you know your stuff, but how do you get this equation? (For instance, I'm sure you know that the ToR says we cannot actually reach lightspeed.)

Is this just something you know off the top of your head?