Scientifically Plausible SF Settings That Provide an Alternative to FTL Travel
https://www.tor.com/2022/06/24/scientifically-plausible-sf-settings-that-provide-an-alternative-to-ftl-travel/

The title is my fault. It's not quite right but I could not think of a better
alternative.

"Suppose for the moment that one was a science fiction author and was trying
to imagine a plausible setting in which a multitude of inhabited worlds were
within easy, quick reach. Further suppose that one did not care to discard
relativity, but likewise was not keen on a setting where time dilation plays
a significant role. What is one to do?"
--
My reviews can be found at http://jamesdavisnicoll.com/
My tor pieces at https://www.tor.com/author/james-davis-nicoll/
My Dreamwidth at https://james-davis-nicoll.dreamwidth.org/
My patreon is at https://www.patreon.com/jamesdnicoll

On Friday, June 24, 2022 at 10:09:04 AM UTC-4, James Nicoll wrote:
> Scientifically Plausible SF Settings That Provide an Alternative to FTL Travel
> https://www.tor.com/2022/06/24/scientifically-plausible-sf-settings-that-provide-an-alternative-to-ftl-travel/
>
> The title is my fault. It's not quite right but I could not think of a better
> alternative.
>
> "Suppose for the moment that one was a science fiction author and was trying
> to imagine a plausible setting in which a multitude of inhabited worlds were
> within easy, quick reach. Further suppose that one did not care to discard
> relativity, but likewise was not keen on a setting where time dilation plays
> a significant role. What is one to do?"

Parallel worlds?

In article <ef19df68-4c98-429c-a7c5-76d7823bfa6bn@googlegroups.com>,
Ahasuerus <ahasuerus@email.com> wrote:
>On Friday, June 24, 2022 at 10:09:04 AM UTC-4, James Nicoll wrote:
>> Scientifically Plausible SF Settings That Provide an Alternative to FTL Travel
>>
>https://www.tor.com/2022/06/24/scientifically-plausible-sf-settings-that-provide-an-alternative-to-ftl-travel/
>>
>> The title is my fault. It's not quite right but I could not think of a better
>> alternative.
>>
>> "Suppose for the moment that one was a science fiction author and was trying
>> to imagine a plausible setting in which a multitude of inhabited worlds were
>> within easy, quick reach. Further suppose that one did not care to discard
>> relativity, but likewise was not keen on a setting where time dilation plays
>> a significant role. What is one to do?"
>
>Parallel worlds?

(scribbles down essay idea)
--
My reviews can be found at http://jamesdavisnicoll.com/
My tor pieces at https://www.tor.com/author/james-davis-nicoll/
My Dreamwidth at https://james-davis-nicoll.dreamwidth.org/
My patreon is at https://www.patreon.com/jamesdnicoll

James Nicoll <jdnicoll@panix.com> wrote:
> Scientifically Plausible SF Settings That Provide an Alternative to FTL Travel
> https://www.tor.com/2022/06/24/scientifically-plausible-sf-settings-that-provide-an-alternative-to-ftl-travel/
>
> The title is my fault. It's not quite right but I could not think of a better
> alternative.
>
> "Suppose for the moment that one was a science fiction author and was trying
> to imagine a plausible setting in which a multitude of inhabited worlds were
> within easy, quick reach. Further suppose that one did not care to discard
> relativity, but likewise was not keen on a setting where time dilation plays
> a significant role. What is one to do?"

A few people have put nice litle black holes in asteroids to give them
all atmospheres eg Wil McCarthy, Antoine de Saint-Exupéry. Presumably,
funny shaped ones will collapse to spherical. Total surface
area ~51 million square km, though only ~6900 square km is Near
Earth.

On Saturday, June 25, 2022 at 3:22:06 AM UTC-5, David Duffy wrote:
> James Nicoll <jdni...@panix.com> wrote:
> > Scientifically Plausible SF Settings That Provide an Alternative to FTL Travel
> > https://www.tor.com/2022/06/24/scientifically-plausible-sf-settings-that-provide-an-alternative-to-ftl-travel/
> >
> > The title is my fault. It's not quite right but I could not think of a better
> > alternative.
> >
> > "Suppose for the moment that one was a science fiction author and was trying
> > to imagine a plausible setting in which a multitude of inhabited worlds were
> > within easy, quick reach. Further suppose that one did not care to discard
> > relativity, but likewise was not keen on a setting where time dilation plays
> > a significant role. What is one to do?"
> A few people have put nice litle black holes in asteroids to give them
> all atmospheres eg Wil McCarthy, Antoine de Saint-Exupéry. Presumably,
> funny shaped ones will collapse to spherical. Total surface
> area ~51 million square km, though only ~6900 square km is Near
> Earth.

Escape velocity is a function of total gravitational potential and not on surface gravity as such. For example,
Basidium, the "Mushroom Planet" from the books by Eleanor Cameron, is something like twenty five miles in
diameter and has Earth-normal surface gravity because of its high density. Escape velocity would be only about
635 meters per second, compared to 11,300 meters per second for Earth. The speed of sound, which is close
to the average speed of an air molecule, is about 300 meters per second in an atmosphere like ours. A significant
fraction of molecules would have speeds above escape velocity. At the top of the atmosphere molecules with
escape velocity can leave the planet without hitting anything to slow them down; they can also be driven
off by solar wind. I would be interested in any estimates of the rate of atmosphere loss for such small bodies.
Certainly they would not retain air over geological time.

Peter Wezeman
anti-social Darwinist

On Saturday, June 25, 2022 at 2:16:49 PM UTC-4, peterwezeman@hotmail.com wrote:
> On Saturday, June 25, 2022 at 3:22:06 AM UTC-5, David Duffy wrote:
> > James Nicoll <jdni...@panix.com> wrote:
> > > Scientifically Plausible SF Settings That Provide an Alternative to FTL Travel
> > > https://www.tor.com/2022/06/24/scientifically-plausible-sf-settings-that-provide-an-alternative-to-ftl-travel/
> > >
> > > The title is my fault. It's not quite right but I could not think of a better
> > > alternative.
> > >
> > > "Suppose for the moment that one was a science fiction author and was trying
> > > to imagine a plausible setting in which a multitude of inhabited worlds were
> > > within easy, quick reach. Further suppose that one did not care to discard
> > > relativity, but likewise was not keen on a setting where time dilation plays
> > > a significant role. What is one to do?"
> > A few people have put nice litle black holes in asteroids to give them
> > all atmospheres eg Wil McCarthy, Antoine de Saint-Exupéry. Presumably,
> > funny shaped ones will collapse to spherical. Total surface
> > area ~51 million square km, though only ~6900 square km is Near
> > Earth.
> Escape velocity is a function of total gravitational potential and not on surface gravity as such. For example,
> Basidium, the "Mushroom Planet" from the books by Eleanor Cameron, is something like twenty five miles in
> diameter and has Earth-normal surface gravity because of its high density.. Escape velocity would be only about
> 635 meters per second, compared to 11,300 meters per second for Earth. The speed of sound, which is close
> to the average speed of an air molecule, is about 300 meters per second in an atmosphere like ours. A significant
> fraction of molecules would have speeds above escape velocity. At the top of the atmosphere molecules with
> escape velocity can leave the planet without hitting anything to slow them down; they can also be driven
> off by solar wind. I would be interested in any estimates of the rate of atmosphere loss for such small bodies.

A few weeks, I would guess. O2 moves about 350m/s at room temperature. As the velocity distribution is
Maxwell-Boltzmann I would expect a large fraction to be moving faster than escape velocity.

If warmed by a cool star or a brown dwarf, that is. If this object receives earth-normal insolation, the top of the atmosphere will be bombarded by very energetic photons, will effectively be at thousands of degrees, and will vanish rapidly.

Those at the surface would be breathing a lot of O3 and even O as not all of these energetic photons will be absorbed
in the upper atmosphere.

William Hyde

On 2022-06-24 8:09 a.m., James Nicoll wrote:
> Scientifically Plausible SF Settings That Provide an Alternative to FTL Travel
> https://www.tor.com/2022/06/24/scientifically-plausible-sf-settings-that-provide-an-alternative-to-ftl-travel/
>
> The title is my fault. It's not quite right but I could not think of a better
> alternative.

Don't say "scientifically plausible".

On 24/06/2022 09.09, James Nicoll wrote:
> Scientifically Plausible SF Settings That Provide an Alternative to FTL Travel
> https://www.tor.com/2022/06/24/scientifically-plausible-sf-settings-that-provide-an-alternative-to-ftl-travel/
>
> The title is my fault. It's not quite right but I could not think of a better
> alternative.
>
> "Suppose for the moment that one was a science fiction author and was trying
> to imagine a plausible setting in which a multitude of inhabited worlds were
> within easy, quick reach. Further suppose that one did not care to discard
> relativity, but likewise was not keen on a setting where time dilation plays
> a significant role. What is one to do?"

If I recall correctly, Poul Anderson's "Antoran" system ("A Sun
Invisible") had a huuuuge primary that had captured a couple dozen
planets. The primary being huuuuge had a huuuge habitable zone (much
farther out than in our system). Thus, the system was ripe for
planetary romances -- not that Anderson used it for that purpose.

--
Michael F. Stemper
Exodus 22:21

On 2022-06-25 3:08 p.m., Michael F. Stemper wrote:
> On 24/06/2022 09.09, James Nicoll wrote:
>> Scientifically Plausible SF Settings That Provide an Alternative to
>> FTL Travel
>> https://www.tor.com/2022/06/24/scientifically-plausible-sf-settings-that-provide-an-alternative-to-ftl-travel/
>>
>>
>> The title is my fault. It's not quite right but I could not think of a
>> better
>> alternative.
>>
>> "Suppose for the moment that one was a science fiction author and was
>> trying
>> to imagine a plausible setting in which a multitude of inhabited
>> worlds were
>> within easy, quick reach. Further suppose that one did not care to
>> discard
>> relativity, but likewise was not keen on a setting where time dilation
>> plays
>> a significant role. What is one to do?"
>
> If I recall correctly, Poul Anderson's "Antoran" system ("A Sun
> Invisible") had a huuuuge primary that had captured a couple dozen
> planets. The primary being huuuuge had a huuuge habitable zone (much
> farther out than in our system). Thus, the system was ripe for
> planetary romances -- not that Anderson used it for that purpose.
>

Nor did the planets have the wildly elliptical orbits you'd expect from
a capture. Velikovskian orbital dynamics were in play.

James Nicoll wrote:

>Scientifically Plausible SF Settings That Provide an Alternative to
>FTL Travel

It depends on what you consider plausible. In the Alastair Reynolds's
Revenger series, the current planets and moons have been broken up and
used to create a multitude of habitats and planetoids (with artificial
gravity).

The tech leven needed to do that is pretty mind-boggling.

Brian

On Saturday, 25 June 2022 at 09:22:06 UTC+1, David Duffy wrote:
> James Nicoll <jdni...@panix.com> wrote:
> > Scientifically Plausible SF Settings That Provide an Alternative to FTL Travel
> > https://www.tor.com/2022/06/24/scientifically-plausible-sf-settings-that-provide-an-alternative-to-ftl-travel/
> >
> > The title is my fault. It's not quite right but I could not think of a better
> > alternative.
> >
> > "Suppose for the moment that one was a science fiction author and was trying
> > to imagine a plausible setting in which a multitude of inhabited worlds were
> > within easy, quick reach. Further suppose that one did not care to discard
> > relativity, but likewise was not keen on a setting where time dilation plays
> > a significant role. What is one to do?"
> A few people have put nice litle black holes in asteroids to give them
> all atmospheres eg Wil McCarthy, Antoine de Saint-Exupéry. Presumably,
> funny shaped ones will collapse to spherical. Total surface
> area ~51 million square km, though only ~6900 square km is Near
> Earth.

I think Larry Niven's _Protector_ has one but I don't
think _The Little Prince_ mentions the issue.

In article <t94ghs$pg7$1@panix3.panix.com>,
jdnicoll@panix.com says...
>
> Scientifically Plausible SF Settings That Provide an Alternative to FTL Travel
> https://www.tor.com/2022/06/24/scientifically-plausible-sf-settings-that-provide-an-alternative-to-ftl-travel/
>
> The title is my fault. It's not quite right but I could not think of a better
> alternative.
>
> "Suppose for the moment that one was a science fiction author and was trying
> to imagine a plausible setting in which a multitude of inhabited worlds were
> within easy, quick reach. Further suppose that one did not care to discard
> relativity, but likewise was not keen on a setting where time dilation plays
> a significant role. What is one to do?"

Peter F Hamilton has wormholes. Big, stable, fixed to the
planet surface, always open, with a pressure curtain to
stop air flowing away. Big enough to drive a train through
- and that's what the humans do. Travel to other worlds by
train.