The short version: this book was a disappointment.

About 2 decades ago, Stirling wrote 2 books that modernized the mid 20th century Planetary Romance genre (_The Sky People_ and _In the Courts of
the Crimson Kings_). Both Venus and Mars had been terraformed during the Mesozoic by a highly advanced interstellar civilization and had been
seeded by life from Earth (with periodic inserts of more species,
including humans, up to about 5 thousand years ago for Venus and perhaps
200 hundred thousand years ago for Mars). The most advanced cultures on
Venus were Bronze age, but Mars had a uniform civilization with
extremely advanced bio-tech on a dying planet. In the epilog of _In the
Courts of the Crimson Kings_ some gates were opened that connected Venus
and Mars to other worlds, and Earth to a Dyson Sphere.

These two books have recently been reprinted by a new publisher and
Stirling wrote a 3rd title, _Lords of Creation_ to go with them. People
are exploring that Dyson sphere, but NONE of them appear to be aware
that a Dyson Sphere has no internal gravity force. They are all walking
around in a 1 g field. In addition, it appears that people had been
snatched from Earth as recently as the 19th century and had replicated
19th century technology. I have my doubts that there were enough people
in the original party to have enough of the knowledge to do this.

--
"We have advanced to new and surprising levels of bafflement."
Imperial Auditor Miles Vorkosigan describes progress in _Komarr_. ‹-----------------------------------------------------
Robert Woodward robertaw@drizzle.com

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

Note: I decided to repost this since Freeman Dyson didn't postulate a
hollow shell, but a massive swarm of objects.

The short version: this book was a disappointment.

About 2 decades ago, Stirling wrote 2 books that modernized the mid 20th century Planetary Romance genre (_The Sky People_ and _In the Courts of
the Crimson Kings_). Both Venus and Mars had been terraformed during the Mesozoic by a highly advanced interstellar civilization and had been
seeded by life from Earth (with periodic inserts of more species,
including humans, up to about 5 thousand years ago for Venus and perhaps
200 hundred thousand years ago for Mars). The most advanced cultures on
Venus were Bronze age, but Mars had a uniform civilization with
extremely advanced bio-tech on a dying planet. In the epilog of _In the
Courts of the Crimson Kings_ some gates were opened that connected Venus
and Mars to other worlds, and Earth to a hollow sphere, 2 Astronomic
units in diameter.

These two books have recently been reprinted by a new publisher and
Stirling wrote a 3rd title, _Lords of Creation_ to go with them. People
are exploring that sphere, but NONE of them appear to be aware
that a hollow sphere has no internal gravity force. They are all walking
around in a 1 g field. In addition, it appears that people had been
snatched from Earth as recently as the later part of the 19th century
and had replicated that 19th century technology. I have my doubts that
there were enough people in the original party to have the necessary
total knowledge to do this.

--
"We have advanced to new and surprising levels of bafflement."
Imperial Auditor Miles Vorkosigan describes progress in _Komarr_. ‹-----------------------------------------------------
Robert Woodward robertaw@drizzle.com

--
"We have advanced to new and surprising levels of bafflement."
Imperial Auditor Miles Vorkosigan describes progress in _Komarr_. ‹-----------------------------------------------------
Robert Woodward robertaw@drizzle.com

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

In article <robertaw-0A4722.23132121082025@news.individual.net>,
Robert Woodward <robertaw@drizzle.com> wrote:

Note: I decided to repost this since Freeman Dyson didn't postulate a
hollow shell, but a massive swarm of objects.

Dyson's phrasing in his original paper was misleading. It comes up
in the letters between Dyson and Poul Anderson. As I recall, the shell
idea upset Anderson because one vast shell had to be a monumental
public works project, which turn means TYRANNY BEYOND THE HUMAN
IMAGINATION.

A cloud on the other hand lends itself to an incremental approach.
Each solar collector could be independent, and you don't even need
traffic control as long as you take an American approach to the
resulting horrifying death rate as habitats collide.

The short version: this book was a disappointment.

snip

These two books have recently been reprinted by a new publisher and
Stirling wrote a 3rd title, _Lords of Creation_ to go with them. People
are exploring that sphere, but NONE of them appear to be aware
that a hollow sphere has no internal gravity force. They are all walking >around in a 1 g field.

This is a recurring issue in Dyson shell SF. Authors want the characters
in illuminated landscapes, thus the inner shell. I can only think of
one exception, Pohl and Williamson's Cuckhoo stories, where the or
at least a biosphere is on the outside of the Dyson shell.
--
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

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

In article <108b28j$1sjak$1@dont-email.me>,
Cryptoengineer <petertrei@gmail.com> wrote:

On 8/22/2025 4:56 PM, Lynn McGuire wrote:

On 8/22/2025 1:13 AM, Robert Woodward wrote:

Note: I decided to repost this since Freeman Dyson didn't postulate a
hollow shell, but a massive swarm of objects.

The short version: this book was a disappointment.

About 2 decades ago, Stirling wrote 2 books that modernized the mid 20th >>> century Planetary Romance genre (_The Sky People_ and _In the Courts of
the Crimson Kings_). Both Venus and Mars had been terraformed during the >>> Mesozoic by a highly advanced interstellar civilization and had been
seeded by life from Earth (with periodic inserts of more species,
including humans, up to about 5 thousand years ago for Venus and perhaps >>> 200 hundred thousand years ago for Mars). The most advanced cultures on
Venus were Bronze age, but Mars had a uniform civilization with
extremely advanced bio-tech on a dying planet. In the epilog of _In the
Courts of the Crimson Kings_ some gates were opened that connected Venus >>> and Mars to other worlds, and Earth to a hollow sphere, 2 Astronomic
units in diameter.

These two books have recently been reprinted by a new publisher and
Stirling wrote a 3rd title, _Lords of Creation_ to go with them. People
are exploring that sphere, but NONE of them appear to be aware
that a hollow sphere has no internal gravity force. They are all walking >>> around in a 1 g field. In addition, it appears that people had been
snatched from Earth as recently as the later part of the 19th century
and had replicated that 19th century technology. I have my doubts that
there were enough people in the original party to have the necessary
total knowledge to do this.

I thought that Dyson Spheres had a star at the center of them for power ?

https://en.wikipedia.org/wiki/Dyson_sphere

"A Dyson sphere is a hypothetical megastructure that encompasses a star
and captures a large percentage of its power output.[1][2][3] The
concept is a thought experiment that attempts to imagine how a
spacefaring civilization would meet its energy requirements once those
requirements exceed what can be generated from the home planet's
resources alone. Because only a tiny fraction of a star's energy
emissions reaches the surface of any orbiting planet, building
structures encircling a star would enable a civilization to harvest far
more energy."

That would certainly give off gravity.

You'd fall toward the sun, in that case. Very, Very slowly.

If I trust the AI in my browser, the sun's gravity at 93 million
miles is about 1/1642 g.

Why burn down a rain forest for such a trivial calculation?
The Sun about 23000 Earth radii away. It is 330,000 times
Earth's mass. The force between them is directly proportional
to the mass and to the inverse square of the distance.



--
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

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

In article <1089que$1bj$1@reader1.panix.com>,
jdnicoll@panix.com (James Nicoll) wrote:

In article <robertaw-0A4722.23132121082025@news.individual.net>,
Robert Woodward <robertaw@drizzle.com> wrote:

Note: I decided to repost this since Freeman Dyson didn't postulate a >hollow shell, but a massive swarm of objects.

<SINP>

These two books have recently been reprinted by a new publisher and >Stirling wrote a 3rd title, _Lords of Creation_ to go with them. People
are exploring that sphere, but NONE of them appear to be aware
that a hollow sphere has no internal gravity force. They are all walking >around in a 1 g field.

This is a recurring issue in Dyson shell SF. Authors want the characters
in illuminated landscapes, thus the inner shell.

And I can think of two handwaves to "solve" the problem. I have a
suspicion that Stirling is unaware of this property of hollow shells
(BTW, the wikipedia article on Dyson Sphere mentions this, though in
passing).

--
"We have advanced to new and surprising levels of bafflement."
Imperial Auditor Miles Vorkosigan describes progress in _Komarr_. ‹-----------------------------------------------------
Robert Woodward robertaw@drizzle.com

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

Robert Woodward <robertaw@drizzle.com> writes:

In article <1089que$1bj$1@reader1.panix.com>,
jdnicoll@panix.com (James Nicoll) wrote:

In article <robertaw-0A4722.23132121082025@news.individual.net>,
Robert Woodward <robertaw@drizzle.com> wrote:

Note: I decided to repost this since Freeman Dyson didn't postulate a
hollow shell, but a massive swarm of objects.

<SINP>

These two books have recently been reprinted by a new publisher and
Stirling wrote a 3rd title, _Lords of Creation_ to go with them. People
are exploring that sphere, but NONE of them appear to be aware
that a hollow sphere has no internal gravity force. They are all walking
around in a 1 g field.

This is a recurring issue in Dyson shell SF. Authors want the characters
in illuminated landscapes, thus the inner shell.

And I can think of two handwaves to "solve" the problem. I have a
suspicion that Stirling is unaware of this property of hollow shells
(BTW, the wikipedia article on Dyson Sphere mentions this, though in passing).

Wouldn't a completely enclosed shell be unstable, like Niven's
Ringworld, and would require something to keep the sun from drifting off
center and eventually hitting one side of the shell?
--
-Don_from_AZ-

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

In article <87tt1y156x.fsf@comcast.net.invalid>,
Don_from_AZ <djatechNOSPAM@comcast.net.invalid> wrote:

Robert Woodward <robertaw@drizzle.com> writes:

In article <1089que$1bj$1@reader1.panix.com>,
jdnicoll@panix.com (James Nicoll) wrote:

In article <robertaw-0A4722.23132121082025@news.individual.net>,
Robert Woodward <robertaw@drizzle.com> wrote:

Note: I decided to repost this since Freeman Dyson didn't postulate a
hollow shell, but a massive swarm of objects.

<SINP>

These two books have recently been reprinted by a new publisher and
Stirling wrote a 3rd title, _Lords of Creation_ to go with them. People >>> >are exploring that sphere, but NONE of them appear to be aware
that a hollow sphere has no internal gravity force. They are all walking >>> >around in a 1 g field.

This is a recurring issue in Dyson shell SF. Authors want the characters >>> in illuminated landscapes, thus the inner shell.

And I can think of two handwaves to "solve" the problem. I have a
suspicion that Stirling is unaware of this property of hollow shells
(BTW, the wikipedia article on Dyson Sphere mentions this, though in
passing).

Wouldn't a completely enclosed shell be unstable, like Niven's
Ringworld, and would require something to keep the sun from drifting off >center and eventually hitting one side of the shell?

Yes. On the plus side, it's only passively unstable. If the star
or shell drift a bit with respect to each other, you have time to
notice and fix it. Ringworlds are actively unstable on short time
scales.
--
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

--- SoupGate-Win32 v1.05
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"Michael F. Stemper" <michael.stemper@gmail.com> wrote or quoted:

Pretty close. I get 1/1656.

Output:

G = 6.6743e-11 ± 1.5e-15 [m^3 kg^-1 s^-2]
Mass of Sun = 1.98847e+30 ± 1e+25 [kg^1]
Distance to Sun (r) = 149668992000.0 ± 0.0 [m^1]
Acceleration towards Sun at r (a) = 0.005924628171867096 ± 1.364445131956885e-07 [m^1 s^-2]
Standard gravity on Earth (g) = 9.80665 ± 0.0 [m^1 s^-2]
Ratio g/a = 1655.2346772691253 ± 0.03812014580713078 [dimensionless]

, source code:

from math import sqrt, isclose

# SI base units: [m, kg, s, A, K, mol, cd]
SI_UNITS = ['m', 'kg', 's', 'A', 'K', 'mol', 'cd']

class DimFloat:
def __init__(self, value, error=0.0, dims=None):
self.value = float(value)
self.error = float(error)
# dims: tuple/list of 7 ints, one per SI base unit
self.dims = tuple(dims) if dims else (0, 0, 0, 0, 0, 0, 0)
if len(self.dims) != 7:
raise ValueError("dims must be a 7-tuple for SI base units")

def __str__(self):
dim_str = ' '.join(f"{u}^{p}" for u, p in zip(SI_UNITS, self.dims) if p != 0)
if not dim_str:
dim_str = "dimensionless"
return f"{self.value} ± {self.error} [{dim_str}]"

def _check_dims(self, other):
if self.dims != other.dims:
raise ValueError(f"Dimension mismatch: {self.dims} vs {other.dims}")

def __add__(self, other):
if isinstance(other, DimFloat):
self._check_dims(other)
val = self.value + other.value
# Errors add in quadrature
err = sqrt(self.error**2 + other.error**2)
return DimFloat(val, err, self.dims)
return NotImplemented

def __sub__(self, other):
if isinstance(other, DimFloat):
self._check_dims(other)
val = self.value - other.value
err = sqrt(self.error**2 + other.error**2)
return DimFloat(val, err, self.dims)
return NotImplemented

def __mul__(self, other):
if isinstance(other, DimFloat):
val = self.value * other.value
# Relative errors add in quadrature
rel_err = sqrt(
(self.error / self.value) ** 2 +
(other.error / other.value) ** 2
) if self.value and other.value else 0.0
dims = tuple(a + b for a, b in zip(self.dims, other.dims))
return DimFloat(val, abs(val) * rel_err, dims)
elif isinstance(other, (float, int)):
return DimFloat(self.value * other, abs(other) * self.error, self.dims)
return NotImplemented

def __truediv__(self, other):
if isinstance(other, DimFloat):
val = self.value / other.value
rel_err = sqrt(
(self.error / self.value) ** 2 +
(other.error / other.value) ** 2
) if self.value and other.value else 0.0
dims = tuple(a - b for a, b in zip(self.dims, other.dims))
return DimFloat(val, abs(val) * rel_err, dims)
elif isinstance(other, (float, int)):
return DimFloat(self.value / other, self.error / abs(other), self.dims)
return NotImplemented

def __pow__(self, power):
if isinstance(power, (int, float)):
val = self.value ** power
rel_err = abs(power) * (self.error / self.value) if self.value else 0.0
dims = tuple(int(power * d) for d in self.dims)
return DimFloat(val, abs(val) * rel_err, dims)
return NotImplemented

def isclose(self, other, rel_tol=1e-9, abs_tol=0.0):
if not isinstance(other, DimFloat):
return False
self._check_dims(other)
return isclose(self.value, other.value, rel_tol=rel_tol, abs_tol=abs_tol)

# Constants with values and uncertainties

# Gravitational constant G (CODATA 2018)
G = DimFloat(6.67430e-11, 0.00015e-11, (3, -1, -2, 0, 0, 0, 0)) # m^3 kg^-1 s^-2

# Mass of the Sun (CODATA has no uncertainty listed here, using negligible) M_sun = DimFloat(1.98847e30, 0.00001e30, (0, 1, 0, 0, 0, 0, 0)) # kg

# Standard acceleration due to gravity g (exact by definition)
g = DimFloat(9.80665, 0.0, (1, 0, -2, 0, 0, 0, 0)) # m/s^2

# Distance Earth-Sun average in meters (93 million miles to meters) mile_to_meter = 1609.344
distance_miles = 93e6
r = DimFloat(distance_miles * mile_to_meter, 0.0, (1, 0, 0, 0, 0, 0, 0)) # m

# Calculate acceleration due to Sun at distance r: a = G * M_sun / r^2
a = G * M_sun / (r ** 2) # m/s^2

# Calculate g/a ratio (dimensionless)
g_div_a = g / a

print(f"G = {G}")
print(f"Mass of Sun = {M_sun}")
print(f"Distance to Sun (r) = {r}")
print(f"Acceleration towards Sun at r (a) = {a}")
print(f"Standard gravity on Earth (g) = {g}")
print(f"Ratio g/a = {g_div_a}")

--- SoupGate-Win32 v1.05
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On Fri, 22 Aug 2025 20:33:23 -0400, Cryptoengineer
<petertrei@gmail.com> wrote:

<snippo Dyson Sphere stuff>

If I trust the AI in my browser, the sun's gravity at 93 million
miles is about 1/1642 g.

Trust an AI? <ROTFL>

Did I tell you about the AI in my browser? When asked if the two parts
of a doorknob lock (one with the lock in the knob, the other with a
turnable thing to lock it on the inside) was recyclable it said "yes,
provided it is empty and clean".

IOW, it thought I was talking about a bottle or a jar.

So much for the "I" in "AI".
--
"Here lies the Tuscan poet Aretino,
Who evil spoke of everyone but God,
Giving as his excuse, 'I never knew him.'"

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

In article <kcnjaklunepcpb4fac4ld94p65f7so2813@4ax.com>,
Paul S Person <psperson@old.netcom.invalid> wrote:

On Fri, 22 Aug 2025 20:33:23 -0400, Cryptoengineer
<petertrei@gmail.com> wrote:

<snippo Dyson Sphere stuff>

If I trust the AI in my browser, the sun's gravity at 93 million
miles is about 1/1642 g.

Trust an AI? <ROTFL>

Did I tell you about the AI in my browser? When asked if the two parts
of a doorknob lock (one with the lock in the knob, the other with a
turnable thing to lock it on the inside) was recyclable it said "yes, >provided it is empty and clean".

IOW, it thought I was talking about a bottle or a jar.

So much for the "I" in "AI".

It didn't think. It strung together words that fit a pattern.

--
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

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

James Nicoll <jdnicoll@panix.com> wrote:

Paul S Person <psperson@old.netcom.invalid> wrote:

So much for the "I" in "AI".

It didn't think. It strung together words that fit a pattern.

I have worked with people like that too.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

--- SoupGate-Win32 v1.05
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In article <nr9makhng176e9irn21d1no2o356m1ue4v@4ax.com>,
Paul S Person <psperson@old.netcom.invalid> wrote:

On Sat, 23 Aug 2025 16:07:31 -0000 (UTC), jdnicoll@panix.com (James
Nicoll) wrote:

In article <kcnjaklunepcpb4fac4ld94p65f7so2813@4ax.com>,
Paul S Person <psperson@old.netcom.invalid> wrote:

On Fri, 22 Aug 2025 20:33:23 -0400, Cryptoengineer
<petertrei@gmail.com> wrote:

<snippo Dyson Sphere stuff>

If I trust the AI in my browser, the sun's gravity at 93 million
miles is about 1/1642 g.

Trust an AI? <ROTFL>

Did I tell you about the AI in my browser? When asked if the two parts
of a doorknob lock (one with the lock in the knob, the other with a >>>turnable thing to lock it on the inside) was recyclable it said "yes, >>>provided it is empty and clean".

IOW, it thought I was talking about a bottle or a jar.

So much for the "I" in "AI".

It didn't think. It strung together words that fit a pattern.

So I have read here and elsewhere. I do not doubt it.

But how does this improve the situation?

Why should we give /any/ credence to something that just strings
together words?

People absolutely should not place any credence in AI slop.

--
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

--- SoupGate-Win32 v1.05
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On Sat, 23 Aug 2025 16:07:31 -0000 (UTC), jdnicoll@panix.com (James
Nicoll) wrote:

In article <kcnjaklunepcpb4fac4ld94p65f7so2813@4ax.com>,
Paul S Person <psperson@old.netcom.invalid> wrote:

On Fri, 22 Aug 2025 20:33:23 -0400, Cryptoengineer
<petertrei@gmail.com> wrote:

<snippo Dyson Sphere stuff>

If I trust the AI in my browser, the sun's gravity at 93 million
miles is about 1/1642 g.

Trust an AI? <ROTFL>

Did I tell you about the AI in my browser? When asked if the two parts
of a doorknob lock (one with the lock in the knob, the other with a >>turnable thing to lock it on the inside) was recyclable it said "yes, >>provided it is empty and clean".

IOW, it thought I was talking about a bottle or a jar.

So much for the "I" in "AI".

It didn't think. It strung together words that fit a pattern.

So I have read here and elsewhere. I do not doubt it.

But how does this improve the situation?

Why should we give /any/ credence to something that just strings
together words?
--
"Here lies the Tuscan poet Aretino,
Who evil spoke of everyone but God,
Giving as his excuse, 'I never knew him.'"

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)