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Posts Tagged ‘Tides’

10/07/2019 – Ephemeris – Tides on and by the Moon

October 7, 2019 Comments off

Ephemeris for Monday, October 7th. Today the Sun will be up for 11 hours and 24 minutes, setting at 7:12, and it will rise tomorrow at 7:49. The Moon, 2 days past first quarter, will set at 2:21 tomorrow morning.

We always see the same face of the Moon turned toward the Earth. This does not mean that the Moon doesn’t rotate. It means that the Moon rotates on its axis in exactly the same time it takes to orbit the Earth. That is no coincidence. The effect of the Earth gravitation across the diameter of the Moon have essentially locked the Moon’s rotation to its revolution period. The crust of the far side of the Moon is thicker than the Earth facing side. The Moon is trying to do the same thing to the Earth. Its pull on the side of the Earth facing it is greater than the pull on the Earth’s opposite side. This stresses the Earth and raises tides in the ocean which actually slow the Earth’s rotation a tiny bit. As a consequence it pushes the Moon away by about 3.8 centimeters a year.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Asymmetry of the crust of the Moon. Credit Lunar and Planetary Institute and Center for Lunar Science and Exploration.

For more information on this illustration:  https://www.lpi.usra.edu/exploration/training/illustrations/planetaryInteriors/ 4th illustration.

 

Categories: Concepts, Ephemeris Program Tags: , ,

04/18/2019 – Ephemeris – Tides

April 18, 2019 Comments off

Ephemeris for Thursday, April 18th. Today the Sun will be up for 13 hours and 37 minutes, setting at 8:31, and it will rise tomorrow at 6:52. The Moon, 1 day before full, will set at 7:22 tomorrow morning.

The Moon and the Earth gravitationally attract each other. And the Moon raises tides in the Earth itself and its oceans. The Earth’s tides on the mass of the Moon has slowed its rotation so it continually shows the Earth the same face. The Moon, only one 81st the mass of the Earth hasn’t been as successful at greatly slowing the Earth’s rotation. It does cause the world’s timekeepers to add one second occasionally to the time stream to offset our atomic clocks to the Earth’s rotation. The most noticeable effects of the Moon’s tidal force is the tides in the Earth’s oceans. The highest tides are when the Sun and Moon are in line with the Earth at new and full moon. Small bodies of water like the Great Lakes don’t have luni-solar tides greater than 2 inches (5 cm).  The Great Lakes do have tide like effects called seiches, like water sloshing in a bath tub, caused by wind or barometric pressure, and can be several feet high.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

This link from NOAA explains tides better than I can:  https://scijinks.gov/tides/.

This link is the explanation of seiches:  https://oceanservice.noaa.gov/facts/gltides.html.

Categories: Concepts, Ephemeris Program Tags:

11/20/2012 – Ephemeris – Tides from Sandy to Galaxies

November 20, 2012 Comments off

Ephemeris for Tuesday, November 20th.  The sun will rise at 7:46.  It’ll be up for 9 hours and 23 minutes, setting at 5:09.   The moon, at first quarter today, will set at 12:50 tomorrow morning.

It was three quarters of the moon’s revolution ago or three weeks that the moon was full and adding to the storm surge of Hurricane Sandy.  When the moon is full or new the moon’s greater tidal force adds to the sun’s giving us the highest tides called spring tides.  Tides are caused by the difference in the gravitational pull on a body from on side to the other when two bodies are close.  That’s why the moon exerts a greater tidal force than the sun, even thought its very much less massive.  Tides just don’t occur in earth’s oceans.  Jupiter’s tidal force tore apart Comet Shoemaker-Levy 9 two years before its more than 20 pieces plunged into Jupiter’s atmosphere in 1994.  Colliding galaxies exhibit tidal tails.

Times are for the Traverse City/Interlochen area of Michigan.  They may be different for your location.

Addendum

Tidal forces on a planet, the earth for instance by the moon.  Source - Wikimedia.

Tidal forces on a planet, the earth for instance by the moon. Source – Wikimedia.

 

Comet Shoemaker-Levy 9.  Courtesy NASA Hubble Space Telescope.

Comet Shoemaker-Levy 9 after a too close approach to Jupiter. The comet was torn into a “String of Pearls” by Jupiter,s immense tidal pull. They came back, crashing into Jupiter in July of 1994. Courtesy NASA Hubble Space Telescope.

 

Two galaxies colliding, throwing off tidal tails as they close in.  NGC4686 photo courtesy NASA and the Hubble Space Telescope.

Two galaxies colliding, throwing off tidal tails as they close in. NGC4686 photo courtesy NASA and the Hubble Space Telescope.

Don't do this at home!  Spaghettification by black hole.

Don’t do this at home! Spaghettification by black hole. The intense gravitational gradient near a black hole will stretch a body, be it asteroid or astronaut as they approach a black hole.

 

 

 

09/20/2012 – Ephemeris – Tides and the moon

September 20, 2012 Comments off

Ephemeris for Thursday, September 20th.  The sun will rise at 7:27.  It’ll be up for 12 hours and 14 minutes, setting at 7:42.   The moon, 2 days before first quarter, will set at 10:29 this evening.

The moon and the earth gravitationally attract each other.  And the moon raises tides in the earth itself and its oceans.  The earth’s tides on the mass of the moon has slowed its rotation so it continually shows the earth the same face.  The moon, only one 81st the mass of the earth hasn’t been as successful at slowing the earth’s rotation.  It caused the world’s timekeepers to add one second this June to the time stream after several years to match our atomic clocks to the earth’s rotation.  The most noticeable effects of the moons tidal force is the tides in the earth’s oceans.  The highest tides are when the sun and moon are in line at new and full moon.  Small bodies of water like the Great Lakes don’t have luni-solar tides.

Times are for the Traverse City/Interlochen area of Michigan.  They may be different for your location.

Note

I can’t explain much about tides in one minute.  Here I’m not explaining the force, but am explaining that it affects the solid bodies as well as the oceans on the earth.

Categories: Ephemeris Program Tags: