[SPACE] Tidal braking

[Agemegos]

Originally Posted by Jon F. Zeigler

We may end up with a full-on rewrite of that page of the book. SJG errata coordinator tells me that this shouldn't present a problem, as long as we're satisfied that the results are correct.

Excellent! I can't tell you how glad I am.

[balzacq]

Originally Posted by Jon F. Zeigler

For those of you who have been following this:

I've finally found the time to start re-evaluating . . . well, pretty much the entirety of p. 117 of Space. I've got most of Agemegos' math in front of me and have been trying to confirm it, with some success already. I think he's on the right track even if I'm not sure of all the details yet.

We may end up with a full-on rewrite of that page of the book. SJG errata coordinator tells me that this shouldn't present a problem, as long as we're satisfied that the results are correct.

Jon, assuming that this is still on track, how would the page 117 rewrite be disseminated?

May I suggest a one-page PDF file linked from the book page and from the errata page? (That could be individually printed and affixed in place in our copies of the book.)

I would be disappointed if we all had to wait for a second printing.

[Noven]

If this does get fixed, I might have a ton of retyping to do on my wiki.

[Agemegos]

Originally Posted by Agemegos

Excellent! I can't tell you how glad I am.

Four months later. Have we any progress?

I have at long last lost any interest in completing my Excel instantiation of the GURPS Space star system generation sequence. Would it be okay to release the beta as orphan-ware, or would SJ Games prefer that I not do that?

[Agemegos]

Originally Posted by Jon F. Zeigler

For those of you who have been following this:

I've finally found the time to start re-evaluating . . . well, pretty much the entirety of p. 117 of Space. I've got most of Agemegos' math in front of me and have been trying to confirm it, with some success already. I think he's on the right track even if I'm not sure of all the details yet.

We may end up with a full-on rewrite of that page of the book. SJG errata coordinator tells me that this shouldn't present a problem, as long as we're satisfied that the results are correct.

Nine months later. Thirty months after I originally submitted these errata. Any progress?

I see that we have worn out another errata co-ordinator.

[David Johnston2]

Originally Posted by Agemegos

Nine months later. Thirty months after I originally submitted these errata. Any progress?

I see that we have worn out another errata co-ordinator.

There is in fact errata for the lunar tidal force equation on the page and the results I get from it aren't blatantly absurd to the untrained eye.

[Agemegos]

Originally Posted by David Johnston2

There is in fact errata for the lunar tidal force equation on the page and the results I get from it aren't blatantly absurd to the untrained eye.

I've seen it: it isn't adequate because it fails to take into account the density factor. And there have been no corrigenda for the errata in tidal braking and day length.

[balzacq]

Brett, now that you're looking at this thread again, and since I'm putting mindshare back into expanding my space milieu, I have a question about the nature of the tidal braking formula:

Originally Posted by Agemegos

Earth's initial day length was about 12 hours, so it has lost 1 rotations/day over 4.5 billion years.

<edit> Correct formula is

E = (0.184 * A * M/D^5) * sum of squares of tide heights.</edit>

I'm not sure how to practically apply E.

If for instance I generate an 8-hour initial rotation and come up with E=3, what is the final rotation period?

[Agemegos]

Originally Posted by balzacq

Brett, now that you're looking at this thread again, and since I'm putting mindshare back into expanding my space milieu, I have a question about the nature of the tidal braking formula:
I'm not sure how to practically apply E.

If for instance I generate an 8-hour initial rotation and come up with E=3, what is the final rotation period?

If you generate and initial rotation period is 8 hours, then the initial rate of rotation is 3 rotations per day. Subtract E, which is 3. You get zero. This will be less than the rate of orbit of/about about the body that raises the highest tides. Therefore your planet will be tide-locked. Set the period of rotation equal to the relevant orbital period.

[Agemegos]

Hi!

I has been three years since I submitted these errata. Fifteen months since Jon Zeigler started evaluating them.

Are we there yet?