[FlamingCobra]

http://space.alglobus.net/papers/Expansion.pdf

Courtesy of Al Globus. 

[watsisname]

http://space.alglobus.net/papers/Expansion.pdf

Courtesy of Al Globus. 

That's very interesting.  What was OP's take on it?

Meanwhile, I'll keep to the two-liner post style of "Yeah."

[The E]

It's a worthless fluff piece. It's all "we can do this, by using this-and-this technology", which would be fine except those technologies are nowhere near the maturity needed, and there is no timetable for them getting to that maturity.

Consider the following excerpts:

At Neptune’s orbit solar arrays must be roughly 900 times larger than 
in Earth orbit to generate the same amount of energy. Thus, it would be best to find another 
source of energy.   One approach is to mine hydrogen and helium from the atmospheres of 
the giant planets and Titan, separate the isotopes and use them in fusion reactors3
.  This is beyond today’s technology but the basic physics are understood.

Beyond today's tech indeed.

[about settlements on Kuiper Belt Objects]
If these objects can be settled, then Earth will at long last be freed from any possibility of a 
devastating collision.  All the large asteroids will have long since been consumed or at least 
shadowed by human settlements, insuring that these will not strike Earth.  Settlement of the 
vast reaches of the outer solar system will bring under observation the source of the 
comets, the last reservoir of objects threatening Life’s birthplace.

If it wasn't clear before, it should be clear now that this article is all about dreaming, not about reality. Even if the tech he wants to use for these plans existed, it would still take a concerted effort by humanity over several generations, hundreds if not thousands of years of continuing dedication to the principle of expanding ever outward. Humanity, as a whole, does not have a good track record when it comes to staying on track for that long.

In the final part of the piece, he talks about creating settlements in systems that are about to be ejected out of the galaxy in order to reach the next one over the course of several million years with the underlying assumption that whatever is on that planet will continue to bear any resemblance to humanity at all.

What could we do in 100 million years with a population measured in quadrillions around each of hundreds of billions of stars? Here’s one possibility.

Here's a few things we can definitely do in a hundred million years and that are much more likely than the dreams he has: 1. We can evolve to something nonsentient. 2. We can kill ourselves by some tech snafu. 3. We can die out through natural causes.


Optimism is a good thing. Blind dreaming without any regard to the practicalities of the situation may look like optimism to the naive observer, but is just stupid intellectual wanking as far as I am concerned.

[Mikes]

You forgot to quote the best part The E,...

Scientists at the Harvard‐Smithsonian Center for Astrophysics recently discovered that
galactic black holes can eject stars from the galaxy at up to four or five percent of light
speed. Furthermore, planets and other bodies orbiting the star can, under the right
circumstances, stay bound to the star. If the direction of this ejection could be controlled,
perhaps by a gravity tractor, then we could use the Milky Way’s black hole to send stars,
complete with orbital space settlements, to the next galaxy in a about twenty million years.

Gravity tractors huh...   and maybe we'll need phasorz in case there are space aliens between the Galaxies too

[watsisname]

I was hoping for OP material, but I'll post some things for discussion anyway.  I'm as pessimistic as The E.

First off, if were as easy to go spreading through and colonizing interstellar and intergalactic space as this paper makes it seem, then why do we see no evidence of it happening anywhere?  Even with lengthy estimates of the timescales required, once the process got going, by virtue of exponential growth with effectively limitless resources, it would take far less than the age of the universe for a civilization to colonize the galaxy, which apparently has not happened.  I can far more readily believe that it is infeasible to spread to other star systems than that we are the only advanced life in the galaxy and/or universe, or that we are the only civilization with dreams of spreading through the cosmos.

These advantages include artificial gravity similar to the Earth

I have not seen much data to the effect of low-gravity environments on human physiology compared to zero-gravity environments, so I'm not sure if I buy this.  I'm not sure if I believe that extended habitation in mars or even lunar gravity is that problematic as far as their surface gravity is concerned.

larger sizes

One can more easily build a larger colony in space as opposed to planetside?  Why?

With the subsequent discovery of Near Earth Objects (NEO),
asteroids and comets in orbits crossing Earth’s, the orbital space settlement materials
problem is elegantly solved by simply co-orbiting with a NEO; and it turns out that orbital
settlements built from small-body materials has radical implications for the future of
humanity.

I'm not so enthusiastic about this idea with NEO's.  Distance of closest approach does not correlate to the energy (delta-v) required to get to and co-orbit or land there.  To do anything useful with an NEO you have to match its orbit, which means achieving a hyperbolic orbit relative to Earth.  This means that even if the NEO should regularly pass as close as 10,000km of Earth, you still must expend more energy to land on it than you would to get to and land on the moon.  So why not just go to the moon instead?  It's larger, closer to earth for far more of the time (so travel time to and fro is almost always less and you don't have to wait enormous lengths of time for a favorable launch window), and is less of an energy hurdle.

As we approach the center, settlement becomes easier as the stars are closer together.

The frequency of supernovae also increases, though this is a more minor issue and I do not suggest it should stop anybody from going to the galactic core.

While the distances between stars are vast, light years, they pale compared to the distance
between galaxies, which are typically around one million light years. However, while we
have never observed them, it is reasonable to expect that, like the space between stars,
there are small bodies, perhaps even entire star systems, in these spaces. Can we develop
the technology to send the first orbital space settlement across the vast void between our
galaxy and the next? Only time will tell, but 100 million years is a long time.

By what theory is it reasonable to expect star systems in the intergalactic medium?  (beyond streams from galaxy collisions, and good luck using those to bridge between galaxies and clusters...)

An additional problem is the relative motion of galaxies with one another and the constant expansion of space which drives clusters ever farther apart.

Scientists at the Harvard-Smithsonian Center for Astrophysics recently discovered that
galactic black holes can eject stars from the galaxy at up to four or five percent of light
speed. Furthermore, planets and other bodies orbiting the star can, under the right
circumstances, stay bound to the star. If the direction of this ejection could be controlled,
perhaps by a gravity tractor, then we could use the Milky Way’s black hole to send stars,
complete with orbital space settlements, to the next galaxy in a about twenty million years."

The author omits some pretty important details with this concept.  Yes, it is true that black holes can and do eject stars at a significant fraction of light speed.
But this happens when a binary (or multiple) star system gets too close, and one component gets captured while the other speeds away.  It's a result of conservation of angular momentum -- the gain in energy of one component must come at the loss of energy from the other.  This maneuver would not and does not work with single objects, and you'd need to sacrifice something significant to get the necessary kick in energy.

Greater question:  Let's assume you somehow manage to control this, and by the power of a supermassive black hole eject your super intergalactic space colony out toward the next galaxy at a significant fraction of the speed of light.

How do you stop upon arrival?  Before anyone answer's, "With a similar maneuver at the SM black hole at that galaxy, of course.", think of the exactness of the trajectory required, how one achieves the course correction if needed, (which it certainly would be), the conservation of energy problem I just mentioned above, and the effect of the interstellar medium smashing into you at relativistic speeds throughout the journey.

edit to add stuff and fix spelling.

[Flipside]

"We could do lots of stuff if we had lots of stuff that did that stuff..."

That said, it doesn't always hurt to dream, but as The E says, we as a species have a poor track record with co-operation beyond a certain point. We need, preferably, a big discovery to motivate us back out there or, at a worst-case scenario, a danger to unite us, such as a small incoming Asteroid. Even then, give it three generations and we will probably be arguing about how big a threat the asteroid really was...

[Mikes]

"We could do lots of stuff if we had lots of stuff that did that stuff..."

That said, it doesn't always hurt to dream, but as The E says, we as a species have a poor track record with co-operation beyond a certain point. We need, preferably, a big discovery to motivate us back out there or, at a worst-case scenario, a danger to unite us, such as a small incoming Asteroid. Even then, give it three generations and we will probably be arguing about how big a threat the asteroid really was...

An asteroid scheduled to arrive right after a presidential election might just wipe us out... 

[666maslo666]

There is a huge catch, though. We don’t know how to generate energy so far from the Sun
and there are no vast supplies of hydrogen or helium.

How come? I thought that in the outer solar system and Oort cloud, light elements such as hydrogen are abundant. If anything, lack of heavier elements will be a problem for asteroid-hopping to the next star.