Posts tagged with Mars

As to longitude, I declare that I found so much difficulty in determining it that I was put to great pains to ascertain the east-west distance I had covered. The final result of my labours was that I found nothing better to do than to watch for and take observations at night of the conjunction of one planet with another, and especially of the conjunction of the moon with the other planets….

After I had made experiments many nights, one night, the twenty-third of August 1499, there was a conjunction of the moon with Mars, which according to the almanac was to occur at midnight or a half hour before. I found that…at midnight Mars’s position was three and a half degrees to the east.

Amerigo Vespucci

Good gosh. Can you imagine having travelled so far on the globe—without a swift means of return, of course—that you literally had no idea where you were?

And what’s more, science to save you. You can’t ask anyone around you for the answer. Many of the people around you not only have never heard of Europe, but can’t even conceive of such a thing.

Nobody knows the answer. ∄ books that purport to have the answer. ∄ communication channels back to home. You’re all alone, mentally. To figure out what’s going on all you have to go on is reason and facts. And if you get the answer right, whom are you going to tell?

(Source: Wikipedia)

How come the planets aren’t arranged spherically around the sun?

the solar system

Instead of being spherical, as seems to be the default shape of things in the universe, the planets are arranged in a more-or-less flat disk — a series of concentric ellipses.

planets and planetessimals

What’s up with that?

Answer: angular momentum + gravity.

The nascent planets (or planetesimals) may have started out spherically arranged around the sun.

But then the spinning sun (or proto-sun) flung its satellites—including Earth—further out into space, like how a merry-go-round flings you off when it spins fast.  So the shape would have become an oblate spheroid, with the major axis being the direction of the sun’s spin.

[an oblate spheroid]

At the same time as centrifugal force pushed out in just one circle, gravity pulled in on the entire sphere.

So the minor axis of the oblate spheroid had nothing pushing it out, only something pulling in, while the major axis was being pushed and pulled.  Eventually the minor axis mostly collapsed and now we humans observe the “flat disk” shape.

SOURCE: Essentials of Geophysics, Part One