Posts Tagged ‘Earth’

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.


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: 4th illustration.


Categories: Concepts, Ephemeris Program Tags: , ,

07/23/2018 – Ephemeris – The importance of Mars in determining the nature of the solar system

July 23, 2018 Comments off

Monday, July 23rd. The Sun rises at 6:19. It’ll be up for 14 hours and 59 minutes, setting at 9:18. The Moon, half way from first quarter to full, will set at 3:41 tomorrow morning.

The accurate observational positions of Mars by Tycho Brahe allowed Johannes Kepler in the early 17th century to discover his three laws of planetary motion. Tycho was the last and greatest of the naked eye astronomers. Kepler befriended Tycho who jealously guarded his observations. It was only after his death in 1601 that Kepler took possession of Tycho’s data. Until then it was believed that planets moved with uniform circular motion, even though they didn’t look like it. Astronomers added circle after circle, called epicycles, to attempt to make their system work. Mars was the worst case. Kepler finally determined that Mars, and indeed all the planets, orbited the Sun in elliptical orbits. That was his first law of planetary motion.

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


The source if the images below is the talk “Mars 2018” I gave at the Betsie Valley District Library, July, 20, 2018.

Tycho and Kepler

Tycho and Kepler. Artist for Tycho: Eduard Ender (1822-1883). Artist for Kepler, unknown. Source: Wikipedia.

Mars and Earth's orbits

Mars’ and Earth’s orbits to scale and positions of the Earth and Mars July 20, 2018, one week before opposition. Note that Mars’ orbit is decidedly not circular. Credit my LookingUp program.

Retrograde Mars Path 2018

Created using Cartes du Ciel (Sky Charts).

Retrograde motion explained

Created using Cartes du Ciel (Sky Charts).

10/19/2015 – Ephemeris – Where did the Moon come from?

October 19, 2015 Comments off

Ephemeris for Monday, October 19th.  The Sun will rise at 8:03.  It’ll be up for 10 hours and 48 minutes, setting at 6:51.   The Moon, 1 day before first quarter, will set at 11:51 this evening.

Only two planets in the solar system have moons at least a quarter the size of the planet they orbit:  The Earth and Pluto.  The Moon is a bit more than a quarter the Earths diameter while Pluto’s moon Charon is half its size.  Probably in the early days of the solar system, some four and a half billion years ago collisions were rather common.  It is thought by many planetary scientists that a Mars sized protoplanet collided with the proto-earth with a glancing blow to rip off much of the Earth’s crust, thrust it into orbit where it coalesced into the Moon.  It seems that Pluto’s Charon may have been formed much the same way.  Some thing the varying axial tilts of the planets may have been caused the same way by smaller objects.

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


Collision spawning the Moon

The hypothetical collision of a Mars sized body with the young Earth. Credit: Joe Tucciarone via NASA

Breaking News

Robert Farquhar the man behind the ISEE-3 spacecraft, the first to hang out at the Earth-Sun L1 point between the Earth and the Sun back in 1978 passed away yesterday.  In 1982 he “stole” the spacecraft and through an amazing number of maneuvers using very little fuel managed to send it through the tail of Comet Gicobini-Zinner ahead of the fleet of spacecraft then aimed at Halley’s Comet.  Last year when the then renamed spacecraft ICE approached the Earth, he hatched a plan to return the spacecraft to its L1 position.  Unfortunately apparently there was not enough fuel pressure to complete the burns necessary for the task.  I’ll have a program on Robert Farquhar next Monday.

05/18/2015 – Ephemeris – Venus, beautiful Evening Star or Earth’s evil twin?

May 18, 2015 Comments off

Ephemeris for Monday, May 18th.  Today the Sun will be up for 14 hours and 55 minutes, setting at 9:07.  The Moon is new today, and won’t be visible and tomorrow the Sun will rise at 6:10.

Venus has been called the Earth’s twin because it is 95 percent the size of the Earth.  It is 72 percent of the Earth’s distance from the Sun, and that seems to be the thing that turned a planet, perhaps as endowed with the same amounts of water and other minerals as the Earth, into Earth’s evil twin.  Those nice shiny white clouds are not the water vapor clouds of Earth, but poisonous corrosive clouds of sulfuric acid droplets.  The air which is mostly carbon dioxide is dense, some 90 times the Earth’s atmospheric pressure at sea level.  The carbon dioxide  atmosphere creates a runaway green house effect, giving a surface temperature of over 800 degrees Fahrenheit.   Hotter, even than Mercury, the closest planet to the Sun.

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


Venus' clouds

The clouds of Venus in ultraviolet light as seen by Pioneer Venus in 1979. Venus’ clouds provide a blank face in visible light. Credit: NASA.

Venus' surface

A map of Venus surface produced by NASA’s Magellan spacecraft using radar: 1990-1994. Credit NASA

07/04/2012 – Ephemeris – The earth at aphelion

July 4, 2012 Comments off

Ephemeris for Independence Day, Wednesday, July 4th.  Today the sun will be up for 15 hours and 27 minutes, setting at 9:30.   The moon, 1 day past full, will rise at 10:02 this evening.  Tomorrow the sun will rise at 6:03.

Today,  Independence Day the earth is at its greatest distance from the sun or about 94.5 million miles from the sun.  It doesn’t do much to weaken the strength of sunlight, as you will find out when you go to the beach, But, occurring in summer, makes summer the longest season by a several days over winter.  Our calendar tries to keep up with the seasonal or tropical year, while the earths revolution from its farthest or aphelion point to the next is slightly longer.  Back in 1776 at the founding of our country the earth was farthest from the sun on June 30th.  As we go more centuries into the future summer will get even a bit longer.  But remember the poor Aussies whose winter will also get longer.

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


The orbits of the inner planets.  (P)erihelion - (A)phelion

The orbits of the inner planets. (P)erihelion – (A)phelion

Perihelion is the closest point in an orbit to the sun, while aphelion is the farthest.  The earth and Venus have the most circular orbits while Mars and Mercury have markedly elliptical orbits.