the end of total solar eclispses *DELETED*

[tropicalzone]

Post deleted by tropicalzone

 

[doubletruncation]

The moon has a linear diameter of 3476 km. The sun has a linear diameter of 1.391 million km. The Sun is 149.6 million km away, which gives it an angular diameter of 0.5327 degrees. The present perigee of the moon is on average 364 thousand km. So presently the moon has an angular diameter at perigee of about 0.547 degrees, which is slightly larger than that of the Sun - hence total eclipses (the average apogee distance is something like 407 thousand km, at which point the moon has an angular diameter of 0.489 degrees - hence annular eclipses). For there to be no more total eclipses, the perigee of the moon would have to be greater than about 374 thousand km, in other words the perigee has to grow by 10 thousand km. The moon is currently moving away from the earth at about 3.82 cm/year (based on lunar laser ranging). At that rate it will take about 260 million years for the moon to recede to the point where we don't ever see total eclipses again. Note, however, that the rate at which the moon recedes from the Earth is *not* constant. It depends very much on the specific distribution of continents on the surface of the Earth. The current rate of recession is actually anomalously high due to a resonance between the time it takes waves to propogate across the pacific basin and the tidal forcing rate (see for example http://www.agu.org/pubs/crossref/1999/1999GL008348.shtml ), so in the past the rate of orbital evolution for the moon was quite a bit less than it is now, and in the future it may be different as well (depending on the course of continental drift). <div class="Discussion_UserSignature"> </div>

 

[MeteorWayne]

Thanx for doing those calculations. You saved my brain and calculator a lot of juice <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[tropicalzone]

that mean i can catch a few more eclipses before they die out!!

 

[weeman]

At a rate of 3.82 cm per year, I would say you have plenty of time to view eclipses, Tropicalzone! <br /><br />Of course, don't drink from the fountain of youth, because then you will live forever; meaning, you will one day see the end of solar eclipses, and this would be a sad, sad day <img src="/images/icons/laugh.gif" /> <div class="Discussion_UserSignature"> <p> </p><p><strong><font color="#ff0000">Techies: We do it in the dark. </font></strong></p><p><font color="#0000ff"><strong>"Put your hand on a stove for a minute and it seems like an hour. Sit with that special girl for an hour and it seems like a minute. That's relativity.</strong><strong>" -Albert Einstein </strong></font></p> </div>

 

[tropicalzone]

well they wouldn't die out they would just all be annular instead of total