On 29Jun2020 1501, Bruce Johnson wrote:
> On Jun 28, 2020, at 12:01 PM, xxxxxx@gmail.com
> <mailto:xxxxxx@gmail.com> wrote:
>>
>> I read one version that used (IIRC) 'tidal forces' dropping below
>> 0.01 G as the boundary. That seemed useful. I'm assuming the galaxy
>> would not impose a notable gravitational pull of over 0.01G... would
>> that be true?
>>
>
> IIRC the metric was the tidal gradient; basically the rate at which
> the large mass curved space/time as you traveled away from it. (IIRC
> the discussion here was sometime dirung the late 90’s early 00’s) For
> a standard earth sized planet it was roughly 100 diameters, but it
> enables you to cacluate the actual distance for multi-planet systems,
> whether the primary star would affect you, jumping away from neutron
> stars, etc.
One virtue of using tidal force was that it varies by the cube of
distance, and thus for worlds of the same density it will always be 100
diameters. Also, changes in density (and thus mass) don't actually
change the distance that much, so using 100 diameters as the standard
rule of thumb means if there's a little margin of safety it'll be fine
for all but the most dense worlds.

--
Rupert Boleyn <xxxxxx@gmail.com>