Viewing a single comment thread. View all comments

atomfullerene t1_is6zv9o wrote

Reply to comment by Dokino21 in Ask Anything Wednesday - Physics, Astronomy, Earth and Planetary Science by AutoModerator

Well, you'd have month-long days. It wouldn't cause life to be on only one side of the planet though.

1

Dokino21 t1_is7rmst wrote

Why would the moon only facing one side of the planet impact the length of days?

1

atomfullerene t1_is7ttc8 wrote

The moon takes a month to go around the earth. If one side of the the earth faces the moon, it must therefore also take a month to rotate.

Granted, a "month" might be much shorter on some other planet if the moon was much closer. For example, pluto's moon charon faces only one side of the planet, but it only takes 6.4 days to orbit.

1

Dokino21 t1_is81el3 wrote

I'm still confused. Why would the moon always facing the eastern hemisphere dictate the duration of the day? The moon would just be up there, staring at us, menacingly day and night. Wouldn't it?

1

Rex_Mundi t1_isaw39q wrote

The presence of the Moon (which has about 1/81 the mass of Earth), is slowing Earth's rotation and extending the day by about 2 milliseconds every 100 years.

2

atomfullerene t1_is82z96 wrote

Think about what it means for the moon to be visible in the sky...that side of the planet has to face the moon. Which means the planet has to take the same time to spin around once as the moon takes to travel around the planet once. Otherwise that side of the planet would get ahead of the moon or get left behind it.

1

Dokino21 t1_is8ln59 wrote

I think I'm missing some vital piece of information in my brain because in my wee brain, I am talking moon is always above my head all the time, it does moon stuff, maybe it rotates like a good boy, but it's always there while the planet does it's rotation around the sun and does it's daily rotation. In my mind, the moon and earth are holding hands while the earth does it's 24 hours a day, 365 a year.

So I am really missing some kind of epiphany in understanding.

1