In My Traveller Universe Detail what parts of Traveller you do (or don't) use in your campaign. 
April 5th, 2021, 05:18 PM

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Issue with living “inside the shell”
Gravity will only naturally come from layers you are outside, once you are in the inside surface, the only gravity will be from the system in the middle which will pull you (and all the inside atmosphere) into the central star.
What I would have it do is
people live outside Most of the shells, but there is one thin shell encompassing the rest (a ceiling shell) at a distance of a few 1000 km, that provides the “sunlight”.
(that way the “living space gravity is natural rather than artificial.

April 6th, 2021, 02:01 PM

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Might need occasional pillars to hold it up, at 1000 km. If its 10 km up you can rely on the difference in air pressure between top and bottom, at 1000 km there would be just vacuum. One can go with arches and pillars.

April 7th, 2021, 05:20 AM


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Quote:
Originally Posted by Werner
Might need occasional pillars to hold it up, at 1000 km. If its 10 km up you can rely on the difference in air pressure between top and bottom, at 1000 km there would be just vacuum. One can go with arches and pillars.

if the area is sufficiently deep as to have significant dilation, it's sufficiently deep that people will be turned to jam.
The difference between 0.9G and 1G is measured in centiseconds per year. And a year is roughly 31536000 seconds.
To have livable for humans, the G's can't exceed 2 by much... and that's still only going to be no more than single digit seconds per year.
you're not going to get humans surviving significant gravitational dilation without having significant centrifugal pseudoforce... but that's got other issues, as well, since the gravitational gradient over 2m with significant time dilation is going to be enough that your speed won't save you from spaghettification.
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April 7th, 2021, 06:00 AM

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Quote:
Originally Posted by aramis
if the area is sufficiently deep as to have significant dilation, it's sufficiently deep that people will be turned to jam.
The difference between 0.9G and 1G is measured in centiseconds per year. And a year is roughly 31536000 seconds.
To have livable for humans, the G's can't exceed 2 by much... and that's still only going to be no more than single digit seconds per year.
you're not going to get humans surviving significant gravitational dilation without having significant centrifugal pseudoforce... but that's got other issues, as well, since the gravitational gradient over 2m with significant time dilation is going to be enough that your speed won't save you from spaghettification.

Here are two real world examples. Earth and Saturn, surprisingly, Saturn has 95 times the mass of Earth, but at its "surface" the gravity is the same as Earth, although its escape velocity is much higher. If you continue increasing the radius of a sphere by the square root of its mass as its mass increases, then its surface gravity will remain the same as its escape velocity continues to increase. In order to do this, the density of the object must decrease, if you continue this trend until the radius equals 0.48 of a light year, that is a birch world, at that point the escape velocity approaches the speed of light, it is the largest possible World you can build that is held together by it's own gravity.
Gravity obeys the inverse square law with distance, and it also increases proportional to mass so is you have a planet with 1 Earth mass and 1 Earth radius you will get 1 Earth gravity on its surface. If you double the radius but keep the mass the same the gravity on its surface will be 1/4 g, and if you quadruple its mass within that same volume you are back to having 1g on its surface. Now normally if you double a planet's radius while keeping the density the same the mass is proportional to the planet's volume so you would octuplets the planets mass, but since you are only quadrupling it, the density of the planet has to be halved each time your double the planet's radius to keep the surface gravity at 1g.
Last edited by Werner; April 7th, 2021 at 09:55 AM..

April 8th, 2021, 09:38 AM


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Quote:
Originally Posted by Werner
Gravity obeys the inverse square law with distance, and it also increases proportional to mass so is you have a planet with 1 Earth mass and 1 Earth radius you will get 1 Earth gravity on its surface. If you double the radius but keep the mass the same the gravity on its surface will be 1/4 g, and if you quadruple its mass within that same volume you are back to having 1g on its surface. Now normally if you double a planet's radius while keeping the density the same the mass is proportional to the planet's volume so you would octuplets the planets mass, but since you are only quadrupling it, the density of the planet has to be halved each time your double the planet's radius to keep the surface gravity at 1g.

n.b. Only applies if the body is solid and (for hollow bodies) is small enough for Rsquared not to be significant.
Birch is neither solid nor small
Take a planet the mass of earth...1G
Take two planets each half the mass of earth and separate them by 1 diameter...No longer 1G at any point on either surface.

April 8th, 2021, 05:56 PM

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Quote:
Originally Posted by BackworldTraveller
n.b. Only applies if the body is solid and (for hollow bodies) is small enough for Rsquared not to be significant.
Birch is neither solid nor small
Take a planet the mass of earth...1G
Take two planets each half the mass of earth and separate them by 1 diameter...No longer 1G at any point on either surface.

Solid is a relative term, a white dwarf is much more solid than the Earth.
A typical white dwarf has the mass of our Sun and the radius of Earth. Since our Sun has 333,000 times as much mass as the Earth, its surface gravity will be 333,000g in direct proportion to its mass, and it will also be 333,000 times as dense as the Earth. The Earth and this hypothetical white dwarf both have the same radius, 6400 km. Now let's say we wanted to blow up this white dwarf to a large enough size so that it has 1g on its surface. The radius of the new object is the square root of its mass multiplied by an Earth radius 6400 km. The new radius is 3,693,194 km. The surface area is 333,000 times that of Earth, it's volume is 192,161,487 times that of Earth. We can find its density relative to Earth by 333,000/192,161,487=0.0017 times that of Earth, if the mass is uniformly distributed under its shell, meaning that every square kilometer has the same amount of mass under it, it doesn't matter whether its hollow or filled with a diffuse gas, it will still be 1g on its surface, if more mass is packed towards one side of the sphere, obviously the uniform gravity won't hold. One can have an expanding sphere and so long at added mass distributed uniformly equal the increasing surface area, the gravity will remain the same.

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