Generation or Sleeper Ships: which would be the better & more realistic option for space travel?


Forum Staff
Apr 2010
T'Republic of Yorkshire

This is your warning. If you can't discuss in good faith, and insist on being argumentative for the sake of trying to "win" the argument, you will be removed from this thread, and possibly the forum.
Jan 2020
Sorry, are you saying a spacecraft can somehow dock with an asteroid and turn it into a home ?

If so, that is simply a ridiculous assertion.
Certainly not. You need the means to turn a rock into a habitat. That requires infrastructure in space so we can build the tools to do the job with. Get a big iron asteroid and a bunch of ice and take it somewhere practical so we can work on it. Drill some holes in it and hollow out a small part of it. Stuff the ice inside and seal it up real tight. Get some large mirrors and use sunlight to heat the asteroid until the ice inside turns to steam and the molten mass expands. Let it cool, seal any cracks and import what you need to create a small eco system. It can be done.
Jan 2020
Isaac Arthur is great to watch, but he likes to think BIG. Like WAY beyond what can reasonably be accomplished in the current real world. For example, you blithely assert that we "have the technology" to make *millions* of cities in space, when we have not even built millions of cities on earth! Where the air is free and kids with baskets can haul mud for construction. While out in space, we've managed to dig up a couple spoonfuls of dirt from Mars and a couple asteroids, using stunningly expensive toys that only needed to work once. You can't just stick a John Deere backhoe on a rocket and start building viable habitats in the asteroid belt. And you certainly won't find millions of people champing at the bit to live there, much less billions. And we don't have the capability to get them there, even if they existed. And an entire asteroid-based community could be wiped out instantly by an accident no worse than a traffic collision.

The limits are HUGE, and will NOT go away "once we get out into space."

They didn't build Rome in a day. It may take us 1000 or even 10000 years to get out into the outer limits of our solar system, if we ever need to. I'm not thinking in terms of the current world or times. I mean really, we're back to building weapons of mass destruction. Considering the idiots in charge currently we may not be here in 1000 years. We haven't really left the caves yet.


Ad Honorem
Dec 2015
It is possible to build artificial space habitats with materials from small solar system objects like asteroids and comets.

So eventually there could be tens, hundreds, thousands, tens of thousands, hundreds of thousands, millions, etc. of such space habitats with populations of thousands of persons each.

And of course adding an engine and fuel supply, etc., to such a space habitat would turn it into a vast generation ship.

So I can imagine that a fleet of several such generation ships might be sent to colonize some region in the outer cometary halo of our solar system. At a speed of one percent of the speed of light, it would take such a fleet 100 years to reach a part of the cometary halo 1 light year from the Sun. At a speed of 2 percent of the speed of light it would take such a fleet 50 years to make the journey, at a speed of 3 percent it would take 33.333 years, at a speed of 4 percent it would take 25 years, at a speed of 5 percent it would take 20 years.

If a fleet of several such generation ships is sent to colonize some region in the outer cometary halo of our solar system. At a speed of two percent of the speed of light, it would take such a fleet 100 years to reach a part of the cometary halo 2 light years from the Sun. At a speed of 3 percent of the speed of light it would take such a fleet 66.666 years to make the journey, at a speed of 4 percent it would take 50 years, at a speed of 5 percent it would take 40 years, at a speed of 6 percent it would take 33.333 years.

So possibly several fleets would be sent from the inner solar system to colonize various regions in the cometary halo. And after expanding in the cometary halo for a period, perhaps centuries, each such colony there might send out one or more fleets of generation ships to colonize another, and farther, region of the cometary halo.

The average distance between a star and its nearest neighbor is about five light years in our part of the galaxy. At a speed of about 1 percent to 10 percent of the speed of light, it would take about 50 to 500 years for a generation ship to travel straight from the inner solar system of one star to the inner solar system of the other star, and about 1,000,000 to 10,000,000 years to go from side to sie of the disc of the Milky Way Galaxy.. But if generation ships make voyages of 1 light year each to colonize regions of the cometary halos, and take 100 to 300 years to each the stage to send out long distance colonizing expeditions of their own, the colonizers could reach the inner solar system of a star 5 light years away in about 450 to 1,700 years.

And travelling at about 100 to 300 years between jumps, and jumps of 1 light year each at a speed of 1 percent to 10 percent of the speed of light, a society could expand in all directions at an average speed of about 110 to 400 years per light year of distance. Thus such a society could eventually colonize the entire galactic disc of the Milky way Galaxy, 100,000 light years in diameter, in about 11,000,000 to 40,000,000 years, if they started from an outer rim of the galactic disc.

If the inhabitants of such space habitats expect that they and their descendants will live in space habitats forever, and have no desire to land on any habitable planets they might possibly find, Generation ships made of such space habitats could make much longer distances.

Possibly some generation ship fleets might travel 10 light years in a single voyage, taking 100 to 1,000 years. And if such voyages are successful, some generation ship fleets might later travel 100 light years in a single voyage taking 1,000 to 10,000 years. And eventually generation ship fleets might make voyages of 50,000 light years, taking 500,000 to 5,000,000 years, reaching and beginning to colonize distant regions of the galaxy.
Without hyperjump, this means space travels only result in separate human civilizations on different parts of the galaxy; they are UNLIKELY to witness others.


Ad Honoris
Jan 2011
I'm sorry, but that is all meaningless metaphysical mumbo jumbo, and borderline embarrassing to read. Physicists know what these things are as well as anyone knows anything. Space is expanding, but that doesn't mean it is expanding into something. We already can change the rate at which we travel through time. Light can be stopped because particles with both positive and negative electromagnetic charge exists. This doesn't work with gravitational waves because no particles with with negative gravitational charge have ever been spotted, and none are postulated by any theory I've ever come across.

Look, fundamental physics is difficult and most people have a very poor understanding of it. Nothing wrong with that, I have a very poor understanding of the vast majority of subjects. But that is no excuse to be saying things which are a combination of wrong, meaningless, and wildly wrong. It's fine to be learning something, it's fine to ask questions and it's fine to make mistakes, but posturing as if you're a source of deep wisdom and saying that nobody knows how something works just because you don't is not fine.
I tried to keep the language simple and probably it does come off well.... But your claim that "these things are well known" is at the other extreme....
For example: Big bang ? Theory.. Cosmic inflation ? Theory ... Yes they are widely accepted and still there are plenty of things we do not know

Among mainstream cosmologists, doubts about the Big Bang largely melted away in the 1960s with the discovery of the cosmic microwave background–an omnidirectional buzz of radiation that makes sense only as a relic from the hot, early era of the universe. But around the fringe, the doubts have persisted. Lately they have intensified, inspired by a puzzling discrepancy in different measurements of how the universe is expanding. Even scientific centrists acknowledge that our understanding of the early universe is glaringly incomplete.

Cosmic inflation is a widely accepted theory about what happened during the first fraction of a second during the Big Bang, but it is not proven. The current dispute over the cosmic expansion rate may be a reflection of our ignorance about that early era. Why and how the Big Bang occurred are complete mysteries. You may have heard cosmologists speculate about the “multiverse,” or about the idea of an oscillating universe with many beginnings, or about a collision between two membranes of reality that created our universe. Nobody knows which of these ideas, if any, is correct.

Was there a time before the Big Bang? Will the universe expand forever? Will there be another Big Bang? Is the universe finite or infinite? Do other universes exist? These are all exciting, wide open questions

I said we do not really know how "time" (among other things) works..... this is one of the top guys in the field saying the same thing

Sean Carroll: I'm trying to understand how time works. And that's a huge question that has lots of different aspects to it. A lot of them go back to Einstein and spacetime and how we measure time using clocks. But the particular aspect of time that I'm interested in is the arrow of time: the fact that the past is different from the future. We remember the past but we don't remember the future. There are irreversible processes

Simple point is again, we need significantly better tech that we have in order to be able to move to other galaxies etc... This better tech might come from a better knowledge and understanding of the above questions and more....


Forum Staff
Oct 2011
Italy, Lago Maggiore
Mah ...

I've noted the exchange of comments about the relativist effect which makes the travellers spend less time than the observers on a "stationary" object. Relativity [the word says it] is related to a system of reference. If a rocket takes off from the surface of the Earth [since the rocket, before of taking off, is moving with the Earth and with us] actually we are the observers and the Earth is the "stationary" object in the system of reference. A part that the speed of the Earth from a relativistic perspective is irrelevant.

Anyway, our beloved rocket takes off and it accelerates reaching the 95% of the speed of light [not bad!].

A common way to express the effect of speed on time is:

Applying this formula we can see that while the travellers on the rocks spend about 10 years on Earth we [the observers on the stationary object] spend a bit more than 32 years.
Reasoning in the other way round, reaching a speed enough near to the one of the light we could cover very long distances without the need to sleep.

If I've written correctly the formula in the electronic sheet, at the 99.5% of the speed of light the factor of time dilatation would allow us to cover 100 light years in about 10 years. At 99,9% it would take 4.5 years [from the subjective perspective of the travellers].
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Ad Honorem
Feb 2012
The effects of low gravity on human beings is known. Our bone structure withers along with muscle fibre. Please note that long term astronauts need assistance during recovery. The six month journey time of an astronaut to Mars, especially if largely confined to a fixed position, does not bode well for returnees. In fact, the recent recruitment for volunteers to colonise Mars was made on the understanding that returning was not possible - however inventive, the colonists would not physically cope with life on Earth again.

That would have the universe expanding at more than 700 times the speed of light (or alternatively even more initially and then progressively slower)
No, it doesn't. Your argument relies on expansion from a fixed centre, in which case you would be right, but the inflation of the universe acts on every part of it. This means the rate of expansion from an observation position is only relative, as indeed Einstein argued.


Ad Honorem
Feb 2012
I don't think that's a solid argument. If zero gravity affects individuals - and technically absolute zero gravity is impossible within the solar system if not space in any scale given mass that generates it - then low gravity cannot be much different other than the extent of the decline. We do have info on the subject - it's been gathered by astronauts for nearly sixty years now, and that was why the low gravity of life on Mars was considered too damaging for a returnee.