> I've also heard that if our moon, or any other substantial body, gets too close to our Earth it will breakup.

This is called the Roche Limit: https://en.wikipedia.org/wiki/Roche_limit

This is a factor of tidal forces and depends on several factors, like
how big the central planet is, how big the moon or other body is, what
the mood is made of. This is why, for example, Saturn has rings.

On Sun, Sep 29, 2024 at 1:42 PM Phil Pugliese - philpugliese at
yahoo.com (via tml list) <xxxxxx@simplelists.com> wrote:
>
> Say, I also have an astro-question.
>
> Over the years I've watched a number of PBS prgs concerning our moon & it's origins.
>
> It's been stated that the distance of the moon has been slowly increasing & it should at some far distant future time, essentially, 'decouple' & go it's own way.
> I've also heard that if our moon, or any other substantial body, gets too close to our Earth it will breakup.
>
> But I've never heard of calculated figures that show;
> A. How close the moon ever could've been w/o breaking up & how long ago that could've been.
> or,
> B. If things go on as currently exists, how long before the moon moves so far away that it's orbit becomes unstable.
>
> Can anyone provide answers?
>
> TIA,
>
>
> On Sunday, September 29, 2024 at 09:23:04 AM MST, Charles McKnight - chuckmcknight at pheonic.com (via tml list) <xxxxxx@simplelists.com> wrote:
>
>
> Hi All!
>
> I’m not an astronomer/astrophysicist so I’m hoping that one of the list members might be able to help me with a question.
>
> In one of the articles on the GURPS JTAS CD, I have the following statement:
>
> In fact, 7+ACU- of light speed is about 1 AU (150 million km) per hour, so the Jgd ship will cross the party's path and pass by the main world in about the time it will take the party to travel a 1/500 that distant.
>
>
> I thought the +ACU- might be some odd character for percentage, but when I do the conversion to validate that number, it doesn’t look correct. Using the calculator from https://inchcalculator.com, I get the following result = 150,000,000 km/h = 0.138985 c, i.e., nearly double what the article seems to be stating so my initial assumption is that the +ACU- may not stand for the percentage sign. If not that, then what might that unit of measure be?
>
> Thanks in advance for your help!
>
> Chuck
>
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