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First of all, for the purposes of this question Pluto is a planet. So the eight planets being considered are Mercury, Venus, Mars, Jupter, Saturn, Uranus, Neptune and Pluto.
My question is: can all eight of these planets go retrograde† at the same time? I know that seven can do so on rare instances; there were 12 days of that in the 20th century all in the 1940's and the 1980's. But to show how rare that is there was a block of 400 years in the middle ages with no days of seven retrogrades. Has eight ever happened? Or is it impossible?
†Retrograde motion as seen from Earth, not retrograde orbits around the Sun.
EDIT: I used the DE431 ephemeris to get the results below. However, if you visit HORIZONS (https://ssd.jpl.nasa.gov/horizons.cgi) and create an ephemeris for Pluto (actually Pluto's barycenter, object 999), the results include this warning:
The Horizons output log may report using DE431 as the source of target or center data, but it is nevertheless using DE433 as an override if Pluto is involved. This is to maintain ephemeris consistency for the New Horizons spacecraft encounter at Pluto.
Therefore, my calculations may be inaccurate, above and beyond the normal inaccuracy of predicting planetary data in the past and future.
There are 2 times in the past 15,000 years and 5 times in the next 15,000 years where all 8 planets are in retrograde as observed from Earth.
The table below lists the times when this happens:
The last column is the ephemeris time, the number of seconds since '2000-JAN-01 12:00:00 UTC', which NASA refers to as "the epoch".
The first line in each pair shows the start time of when all 8 planets are in retrograde, and the final planet to enter retrograde to make this true.
The second line in each pair shows the end time when at least one planet is no longer in retrograde, and the planet whose retrograde period has ended.
B.C. 12435-AUG-10 07:52 JUPITER STARTS RETROGRADE -455482152466.038696 B.C. 12435-AUG-24 17:12 MERCURY ENDS RETROGRADE -455480909251.797852 B.C. 4139-MAR-23 15:02 MARS STARTS RETROGRADE -193692373029.630005 B.C. 4139-MAR-28 21:57 MERCURY ENDS RETROGRADE -193691916114.978455 A.D. 7662-APR-27 19:33 MARS STARTS RETROGRADE 178685595220.195740 A.D. 7662-MAY-12 05:19 NEPTUNE ENDS RETROGRADE 178686840014.478882 A.D. 8807-JAN-07 02:02 MERCURY STARTS RETROGRADE 214808680981.726929 A.D. 8807-JAN-20 01:05 JUPITER ENDS RETROGRADE 214809800771.851685 A.D. 10575-FEB-14 21:34 VENUS STARTS RETROGRADE 270604748086.593933 A.D. 10575-FEB-24 18:53 NEPTUNE ENDS RETROGRADE 270605602468.037781 A.D. 13679-NOV-06 16:03 VENUS STARTS RETROGRADE 368580427477.379639 A.D. 13679-NOV-19 01:05 MERCURY ENDS RETROGRADE 368581496795.683594 A.D. 16364-MAR-11 19:25 MERCURY STARTS RETROGRADE 453290109945.561157 A.D. 16364-MAR-13 08:53 MARS ENDS RETROGRADE 453290244824.895996
Notes and caveats:
I wrote https://github.com/barrycarter/bcapps/tree/master/ASTRO/bc-retrograde.c to print out retrograde times for all planets.
The file https://github.com/barrycarter/bcapps/tree/master/ASTRO/all-retrogrades.txt.bz2 shows start and end retrograde times for all 8 planets. NOTE: the lines indicating that planets leave retrograde at "17191-MAR-01 00:00" is incorrect-- that's simply the maximum time for which I could make calculations.
I wrote https://github.com/barrycarter/bcapps/tree/master/ASTRO/bc-moving-backwards.pl to determine which planets were in retrograde at any given time, and used the results to find the times above where all 8 planets were in retrograde.
I spot checked my results against https://www.calsky.com/ -- note that I am computing "ecliptic retrograde", when a planet's ecliptic longitude is decreasing, not "equatorial retrograde", when a planet's right ascension is decreasing.
- As always, I invite people to double check my results, and remind everyone not to use my results for anything critical.
Experiment 3: Retrograde motion of Planets
Retrograde motion refers to the change of direction of the planets as they wander through the fixed background of the stars. All planets show retrograde motion when viewed from Earth with respect to background stars.
Superior Planets show retrograde motion when they are in opposition, Inner planets Venus and Mercury appear to move in retrograde in a similar mechanism, but as they can never be in opposition to the Sun as seen from Earth, their retrograde cycles occur when they are in lower conjunctions with the Sun. For example, Mars appears to move monotonically in one direction but then suddenly during the time of opposition, appears to move backwards making a retrograde loop. Later it again shows motion in forward direction. Although it actually does not move in opposite direction, following figure illustrates the motion-
(source : http://todayastrology.info/retrograde-motion-of-mars.html)
To view the retrograde motion of mars using stellarium follow the steps-
- Step 1: Start the software Stellarium. You may set it in such a way so that the entire sky is visible.
- Locate the Mars
- Insert the planet's orbit. (Press 'O')
- Insert the planet's label. (Press 'P')
- Remove the Atmosphere and Ground. (Press A and G)
- Make the horizon round to see the whole sky through a hole. (Press 'up' and 'down' key)
- Zoom in and out to get the whole horizon and Mars' orbit. (Use 'Page up/down')
- Now you increment the sidereal day by pressing 'Alt+='.
Alternate Method- To Observe the Retrograde Loop of Mars using stellarium follow the steps :
(Please click here for larger view : http://youtu.be/xtuf-FShJM0)
Retrograde motion of other planets can also be viewed using similar procedure.
Venus, June 2021 (Chris Vaughan, Starry Night Education)
Extremely bright (magnitude -3.85) Venus will slowly continue to increase its angle east of the Sun during June, but it won&rsquot climb high enough to see in a dark sky after sunset until the end of the month. If you have an unobstructed view of the west-northwestern horizon, look for Venus sitting low in the sky. It will set at about 9:45 p.m. local time on June 1 and about 10:10 p.m. on June 30. Viewed through a telescope during June, Venus will exhibit a 90-per-cent illuminated phase and an apparent disk diameter of around 11 arc-seconds. (As always, ensure that the Sun has completely disappeared below the horizon before using binoculars or telescopes to view Venus.) Our neighbouring planet will be travelling eastward through the stars of Gemini from June 2-24. Then it will pass into Cancer, where it will rendezvous with Mars on July 12-13. On June 11, the very young crescent Moon will be positioned several finger widths to the lower right (or three degrees to the celestial west) of Venus, allowing both objects to appear together in binoculars, and offering a nice photo opportunity.
Mars, June 2021 (Chris Vaughan, Starry Night Education)
After spending several months parked halfway up the western evening sky, Mars will rapidly descend into the post-sunset twilight during June. On the first days of the month, the magnitude 1.75 red planet will be shining a palm&rsquos width to the lower left (or five degrees to the celestial south) of Gemini&rsquos easterly bright star Pollux, and Mars will set at about 11:30 p.m. local time. On June 8, Mars will move into Cancer where, on June 23, its orbital motion will carry it directly through the large open star cluster known as the Beehive or Messier 44. That passage will be a terrific sight in a backyard telescope or binoculars. Mars will be telescope-close to the &ldquobees&rdquo on the surrounding evenings. Telescope views of Mars during June will show a shrinking, four arcsecond-wide disk. At the end of June, Mars will be setting at 10:30 p.m. local time. Much brighter Venus, positioned about a palm&rsquos width to Mars&rsquo lower right, will already be closing in for their conjunction on July 12-13. Watch for the waxing crescent Moon to hop past Mars on June 12-13.
Mercury in retrograde: What it really means
For people of the astrological persuasion, few planetary trends are as noteworthy as Mercury in retrograde. As the solar system's smallest planet appears to reverse through the sky, you'll hear it blamed for a wealth of frustrating situations, including overspending on new purchases, poorly planned work pitches and unimpressive first dates.
The common astrological advice for people during Mercury retrograde is to avoid starting anything new and to focus instead on reassessment, mimicking the way the planet appears to be retracing its own movements. In 2016, Mercury retrograde will occur four times, totaling about 80 days. That is a lot of time for reassessment.
Astronomers tend to disagree with these associations. "The idea that the gravity from these very distant bodies affects our lives in some way just doesn't work in the framework of physics," said Jean-Luc Margot, a planetary astronomer and professor at UCLA. [The 8 Greatest Mysteries of the Planets]
Finding the facts about Mercury's retrograde motion is complicated because it's both a real and imagined phenomenon. "All the planets rotate around the sun in the same direction, and that never changes," Margot said. However, if a person were able to trace Mercury's position during retrograde -- which is a challenge, because the sun blocks our view -- they'd end up with a line that changes direction. This is because Mercury retrograde is an optical illusion resulting from our position (on Earth) relative to Mercury.
The term "retrograde" in this instance refers to a perceived reversal in the standard west-to-east movement of Mercury through the stars. While some objects in space do experience true retrograde motion -- Venus spins about its axis in the opposite direction than the other planets, a situation called retrograde spin -- Mercury's backtracking is an issue of perspective. Its orbit is smaller and faster than Earth's. When its orbit catches up to and passes Earth, it creates the illusion that Mercury is backtracking, astronomers say.
Put more plainly, pretend you're Earth, watching Mercury run around a track. As it runs its loop, it will start out moving from the left side of your field of vision to your right. Then, it rounds the corner and, although not moving backward, is now running from right to left. This analogy is oversimplified because it doesn't take into account the fact that Earth is also moving, but it gives a good idea of how this optical illusion plays out.
All of the planets exhibit apparent retrograde motion, although it plays out slightly differently for planets farther from the sun than Earth versus those, like Mercury, that are closer to the sun than Earth.
Pseudo planetary effects
As for the potential influence of this seemingly odd movement on our daily lives, science doesn't back it up. In his 1974 book "The Jupiter Effect" (Walker Books), writer John R. Gribbinpredicted that the alignment of all of the planets and the sun on the same side of the Earth would have catastrophic effects.
James Zimbelman, a geologist at the Center for Earth and Planetary Studies at the Smithsonian's National Air and Space Museum, said this prediction actually prompted some scientists to look into the magnitude of the gravitational effects of planetary objects on Earth. "The net result of all of that was, the force is so small compared to either the sun or the moon, that any kind of planetary effect would just be swamped by the things the Earth is always feeling by either the sun or the moon," Zimbelman told Live Science. [Moon Myths: The Truth About Lunar Effects on You]
(For reference, Margot said the gravitational effects a person experiences when standing next to another person are thousands to tens of thousands of times greater than the gravitational forces exerted on them by the moon.)
The vast number of Internet sources mentioning Mercury's retrograde are astrological sites, which then go on to offer advice on how to combat its influence. Mars' apparent retrograde motion is the most obvious of the retrogrades because people can easily view Mars in the night sky as it is the closest planet and, unlike Mercury and Venus, doesn't require a person to look at the sun in order to observe it. This apparent retrograde motion garners much more notice from educational sources. Of the three experts contacted by Live Science, all three considered Mercury retrograde fairly unworthy of discussion.
"All planets appear to go through a period of retrograde (east-to-west) motion against the stars as seen from the Earth," Geoff Chester, a spokesman for the U.S. Naval Observatory, wrote in an email to Live Science. "There is nothing unusual in this. Mercury is no exception. There is no story here."
The Mercury transit
Even if retrograde isn't worthy of much scientific thought, it does overlap with a more exciting astronomical event. About once every 10 years, while Mercury is passing Earth, everything lines up just right, and Mercury crosses in front of the sun from our point of view on Earth. This is called the transit of Mercury and occurred again on May 9. [Video: Everything You Need to Know About the Mercury Transit]
Enjoying the transit may be perhaps the greatest, clearest effect Mercury retrograde can have on your life.
The NASA/ESA SOHO spacecraft captured this image of Mercury transiting the sun on Nov. 8, 2006. ESA/NASA/SOHO
How does the heliocentric model explain retrograde motion of Mars?
Because the earth orbits the sun faster than the outer planets (Mars, Jupiter, Saturn) the apparent position of those superior planets, viewed against the backdrop of the 'fixed stars', appears to undergo a 'looping' retrograde motion. From a heliocentric perspective, then, retrograde motion is an illusion.
Also Know, how does the heliocentric model explain retrograde motion quizlet? Aristotle proposed that all planets revolve around the Sun. During retrograde motion, planets actually stop and move backwards in space. The heliocentric model of the universe holds that Earth is at the center and everything else moves around it. The major axis for a particular planet is known.
Similarly, you may ask, can a heliocentric model explain retrograde motion of the planets?
(5) In the heliocentric model of Copernicus, retrograde motion of planets is naturally explained. Retrograde motions occur naturally if planets further from the Sun move more slowly. As Earth &ldquolaps&rdquo Mars, Mars appears to go backward as seen by observer on Earth.
What produces the retrograde motion of Mars?
Retrograde Motion in Mars occurs when Earth, which travels faster than Mars, passes Mars. This makes Mars appear to go Westward. The apparent motion of the planets when they appear to move backwards (westward) with resperct to the stars from the direction that they move ordinarily.
Retrograde Motion of the Planets
A. Retrograde motion occurs from the fact that the planets are revolving around the sun while the sun itself moves around the hub of the earth. This particular path the planets take makes it appear as if several of them make a loop along their annual journeys across the night sky.
Please note that the planets are moving very slowly around the sun, along with the sun as it rotates around the center, and would not retrograde several times a day as might be implied by the above diagram. The diagram is for illustration purposes only. Several retrogrades a year would be more appropriate, depending on the planet.
The retrograde happens very slowly in the night sky, over a long period of time.
Similar to Jupiter, Saturn retrogrades for about one third of every calendar year spending an average of 20 weeks moving backwards. This retrograde is probably the one that most astrologers feel relieved to see. Saturn, the taskmaker and stern grandaddy of the zodiac, is adamant about keeping us in line when the planet is direct. Saturn wants us to accomplish our goals, live a balanced, healthy life and work hard.
If we aren’t living up to Saturn’s standards, this planet has no problem reminding us of how it rules Karma, too. When Saturn goes retrograde, we get a little break from new lessons and a chance to revisit old ones, which tend to be gentler and more familiar. Enjoy this 20-week break and spend time ensuring you took heed in the life lessons you were taught when the planet was direct.
Chapter 8 — The apparent retrograde motions of our “P-Type” planets
Here on Earth, we only have a handful of clear, empirically solid clues to help us figure out the celestial mechanics of our cosmos. If we are going to ignore these precious few indicators, we might as well not bother thinking through the mechanics of our cosmos at all. The apparent “retrograde” motions of our system’s bodies are among these precious few, invaluable observations. The fact that our planets appear to periodically come to a halt — and start moving backwards for a few weeks or months — is something that has mystified astronomers. However, contrary to popular belief, these (irregular) retrograde motions have never been accounted for in a satisfactory manner.
Now, if you are among those contending that Earth is non-rotating, totally stationary and/or flat as a French pancake, you will still need to explain why our planets periodically appear to reverse course. It is hard to imagine what exactly such an explanation could be, but if you’re determined to believe such theories, you could come up with something to this tune:
“Oh, we occasionally see those planets retrograding because they are, in fact, rocket-propelled spaceships … and from time to time, the pilots will slam their engines into reverse gear!”
While we may laugh at such fanciful theories, it is a poorly-acknowledged fact that the question of the observed irregularity of our outer planets’ retrograde and stationary periods is still far from being settled. To wit, the Copernican/Keplerian model does not adequately account for the irregular nature of these intervals while the ancients ultimately failed to reconcile them with the Aristotelian ideal of uniform circular motions, a notion which model-makers pursued for millennia.
Above — extract from p. 20, Parallax: The Race to Measure the Cosmos,
Publisher: W. H. Freeman (May 1, 2001)
As we saw in Chapter 7, the retrograde motions of Mercury and Venus are incompatible with the Copernican/Keplerian model, since their observed durations are inconsistent with a heliocentric geometry. In fact, the same can be said about the retrograde motions of our so-called “outer planets” (from Jupiter to Pluto) or what we should more correctly refer to as our binary system’s “P-type planets”. We shall start with these and see if the TYCHOS can overcome the incongruities afflicting the heliocentric interpretation of our outer planets’ irregular motions in our skies.
Unless you are an astrophysicist, you might wonder what a “P-Type” planet is. A clear explanation can be found at this web page of the Vienna University’s department of Astrophysics.
Please overlook the highly elliptical orbital shapes in this graphic from the above site and note the P-Type planet’s behavior in relation to the central celestial bodies.
P-Type planets are bodies that circle around a binary system. They are circumbinary. In the case of our own Sun-Mars binary system, these would be our outer (a.k.a. “superior” or “Jovian”) planets from Jupiter outwards: Jupiter, Saturn, Uranus, Neptune and Pluto. As of the Copernican theory, the retrograde motions of our outer planets are meant to be caused by Earth periodically “overtaking them” as we hurtle around the Sun around our “inside lane”, faster than each one of them.
For instance, Jupiter is observed to periodically stop moving (remaining stationary for a variable number of days) and start “retrograding” for about 120 days (i.e. moving in the opposite direction of its ordinary motion). Curiously though, Jupiter can remain stationary for as many as 24 days or for as little as 12 days! This substantial irregularity has been an enigma what could supposedly cause Jupiter (as it gets routinely overtaken by Earth every thirteen months or so) to take such distinctly longer or shorter “lunch breaks”? This can hardly be imputable to any sort of Keplerian variables or perturbations, for these large disparities between Jupiter’s standstill intervals can occur within relatively short time periods. Let’s have a look at a typical such period (between 2019 and 2020) as predicted by Copernican planetariums:
• Between April 20, 2019 and July 30, 2019, Jupiter is observed to retrograde.
• On July 30, 2019, Jupiter stops again, and remains stationary for 24 days.
• Between August 24, 2019 and May 8, 2020, Jupiter is observed to move prograde.
• On May 8, 2020, Jupiter stops again, and remains stationary for 14 days.
One can only wonder why Jupiter would possibly behave in this way in the Copernican model. Shouldn’t Jupiter remain stationary for a fairly equal number of days, each time it meets up with Earth around their concentric, near-circular orbits?
The TYCHOS model submits the following explanation for this substantial variance, although the reader may have to return to it later on in order to fully conceptualize it (in Chapter 26, I will expound in more detail what I call “a Man’s Yearly Path”, the peculiar loop around which we all “swirl” each year). For now, suffice to say that the annual, asymmetrical frame of reference of any earthly observer follows a geometric curve known as a “prolate trochoid”.
A so-called “prolate trochoid”
In order to visualize how such a trochoid can manifest itself in the real world, imagine affixing a little fluorescent sticker on the side of your bicycle tire. If you just spin the wheel around its axis, the sticker will revolve in simple, uniform circles. But if you hop on your bike and start pedalling down the road, passers-by will see your fluorescent sticker tracing such trochoidal loops.
In the TYCHOS, Earth spins once daily around its axis while slowly moving forward. If you could hover above Earth for a full year and film a time lapse video of someone lighting a firecracker outside their house at midnight every night, those flashes will trace a trochoidal path similar to one of the three above loops. We may thus imagine the difficulty for earthly observers to make sense of any long-term astronomical observations since they are themselves being carried around this looping trajectory.
This leads us to how the TYCHOS model can geometrically account for Jupiter’s odd behavior. In the TYCHOS, the three well-known motions of Jupiter (prograde, stationary & retrograde) are plotted in my below graphic. The irregularities of Jupiter’s alternating retrograde and prograde motions is caused by the “accelerating and decelerating” transverse displacements of the observer in relation to Jupiter’s (more or less perpendicular to the viewer) direction of travel. Likewise, the duration of Jupiter’s standstill intervals will also fluctuate substantially. This, due to the constantly-variable vectors of the annual trochoidal curve (with respect to Jupiter’s celestial positions) along which any earthly observer will be carried.
Note that Jupiter’s three “stationary intervals” depicted in my above 2019/2020 example clearly correspond to time periods during which an earthly observer’s annual motion will transition between the “x” and “y” coordinate axes constituting the vector components of a Man’s Yearly Path. In fact, all of our “P-Type” planets are observed to behave in similar manners, as they alternate between prograde, stationary & retrograde motions. The irregularity of these various intervals are a natural consequence of our ever-shifting, “non-linear” (or, if you will, “non-uniform”) earthly frame of reference.
The Danish astronomer Ole Roemer is famously credited for having first determined (or approximated) the speed of light. As the story goes, Roemer made this epochal discovery while observing the motions of Jupiter’s largest moon “Io” (which employs about 42½ hours to revolve around Jupiter). He noticed that the eclipse periods of Io, as it passed behind Jupiter, were irregular they lasted longer (as his heliocentric reasoning went) “whenever Earth was receding from Jupiter” and they lasted for a few minutes less “whenever Earth was approaching Jupiter” . According to his calculations, the total time-discrepancy amounted to about 22 minutes. He came to the conclusion that this 22-minute difference (subsequently adjusted to 17 minutes) was due to the time needed for light to travel across the distance of 2AU (twice the distance between Earth and the Sun).
In the TYCHOS, Roemer’s observations have a plain, “geoptical” explanation I’ve illustrated below. Whenever Jupiter appears to retrograde, the eclipses of Io will appear (as viewed from Earth) to last for a slightly shorter time than when Jupiter moves prograde. The time differential is thus nothing more than an angular “space-time” optical illusion.
Please note that my above graphic isn’t about disproving the currently-accepted velocity of light (approx. 300,000 km/s). It is only meant to show that Roemer’s acclaimed (yet misinterpreted) observational discovery can be readily accounted for by the TYCHOS model without the need for Earth’s supposed orbital motion around the Sun.
In short, the irregular periods of Io’s eclipses are quite simply a direct consequence of Jupiter’s alternating motions as viewed from Earth. One may say that the history of astronomy is riddled with illusory conclusions. One of the weaker spots of the human mind appears to be its spatial perceptions when confronted with the many tricks of perspective that nature loves to play on us.
What explains retrograde in the Copernican model of the solar system?
Answer: Retrograde motion is an APPARENT change in the movement of the planet through the sky. The explanation for retrograde motion in a heliocentric model is that retrograde occurs roughly when a faster moving planet catches up to and passes a slower moving planet.
Secondly, why was the Copernican model not accepted? Copernicus had two main reasons for asserting that the Sun was the center of our solar system. He knew that this could be explained instead by having the Earth also moving around the Sun. The true motion of the planets around the Sun is not uniform circular motion, so Copernicus' model still needed to have epicycles.
Herein, how did the models of Aristarchus and Copernicus explain the retrograde motion of the planets?
Models of Aristarchus and Copernicus were based on a heliocentric model in which all planets including Earth revolve about the Sun. Their models suggested that the retrograde motion of the planets is a result of our viewing the universe from a moving Earth.
How does the heliocentric model of Copernicus explain the retrograde motion of Mars?
Because the earth orbits the sun faster than the outer planets (Mars, Jupiter, Saturn) the apparent position of those superior planets, viewed against the backdrop of the 'fixed stars', appears to undergo a 'looping' retrograde motion. From a heliocentric perspective, then, retrograde motion is an illusion.
Worlds of Creation: Earth
“The Earth is the Lord’s, and all it contains, The world, and those who dwell in it” (Psalm 24:1). It’s not the largest planet, nor the brightest. It is one planet among billions, perhaps even billions of billions. But the Earth is uniquely designed for life (Isaiah 45:18). This makes it quite different from any other known world. And while it may not be the center of the physical universe, the Earth is certainly central to God’s plan of redemption.
It seems strange to discuss the discovery of the planet Earth. After all, people have lived on its surface since the sixth day of creation. But people have not always known that Earth is a planet. From our everyday experiences, it is not obvious that Earth is the same kind of object as those five “wandering stars” that people have watched since antiquity. Throughout most of recorded history, most people believed that the Earth was a stationary object at the center of the universe. The heavens were thought to be very different from Earth. They were considered to be the unreachable realm of the gods, while the Earth was the lowest order of creation.
But the Lord delights in defying our expectations. He has ways of showing us that hasty generalizations from our extremely limited experiences often lead to wrong understandings of reality. The field of astronomy is full of examples. Who in antiquity could have imagined that we live on a massive sphere that encircles the sun at 67,000 miles per hour? Who would have guessed that from the cloud tops of Venus or from the surface of Mars, the Earth would appear as a tiny bright star, just like the other planets? Did Adam understand any of this? Did Noah or Moses?
Educated people have known since the 500s B.C. that the Earth was spherical. Biblical verses such as Job 26:10 suggest that believers knew about the roundness of Earth since 2000 B.C. But the first record we have of someone claiming that the Earth orbits the sun goes back to the Greek mathematician Aristarchus in the early 200s B.C. He used geometry to demonstrate that the sun was bigger than the Earth – contrary to previous thinking. Aristarchus then correctly supposed that it made more sense for the little sphere to orbit the big one than the reverse. But few people, if any, were persuaded by his claims. It would take the advancement of Christianity to allow science to triumph over preconceptions.
When we think biblically, we recognize that God is Lord of both heaven and Earth (Acts 17:24). Both are under His sovereign control, and neither are divine (Deuteronomy 4:19). God upholds the cosmos in the same consist way that He upholds activity on Earth, for they are equally His, and hence obey the same laws (Job 38:33 Jeremiah 33:25). Contrary to what is often claimed, biblical thinking made possible the scientific discovery that the Earth is a planet that orbits the sun. And great Christian astronomers such as Johannes Kepler were instrumental in this scientific revolution. Thanks to the advancement of Christianity in Europe by the 1600s, science began to advance rapidly due to the common expectation that God upholds His creation – both heaven and Earth – in a consistent and rational way. Today we have pictures of Earth taken from space. We even have pictures of Earth taken from the surface of Mars. And indeed, the Earth is a planet that orbits the sun.
This image is from the surface of Mars. The tiny “star” to the left and slightly above center is Earth. The much fainter star just below it is the moon.
Similarities and Differences
As a planet, the Earth has much in common with the other worlds of the solar system. But since it was uniquely designed by God to be inhabited, it also has important differences. Let’s consider some of the more significant similarities and differences.
Like Mercury, Venus, and Mars, Earth is a terrestrial planet – meaning it has a solid surface and consists mainly of rock. In fact, Earth is the protype of terrestrial planets since the term terrestrial means “Earthlike.” Like the other terrestrial planets, Earth is relatively small – a mere 7900 miles in diameter. This seems large with respect to our everyday experiences. But the Jovian (“Jupiter-like”) planets in our solar system are much larger. Earth is, however, the largest of the terrestrial planets in our solar system – just 5% larger than Venus.
Earth has an atmosphere that is far more substantial than the atmosphere of Mars, or the virtually non-existent atmosphere of Mercury. On the other hand, Earth’s atmosphere is less than 2% the mass of the atmosphere of Venus. The composition of Earth’s atmosphere is rather unusual. It is about 80% nitrogen, which is common, but the remaining 20% is primarily oxygen. No other known planet or moon has abundant oxygen in its atmosphere. From a biblical perspective, this makes sense because humans and animals need oxygen to breathe.
Being the third planet in distance from the sun, the Earth has a cooler surface temperature than that of Venus or the (average) temperature of Mercury. And it is warmer than Mars. Its unique position, being neither too close nor too far from the sun leads to a very significant difference between Earth and the other planets: liquid water.
Liquid water can only exist in a fairly narrow temperature range, and with significant atmospheric pressure. Earth has the right kind of atmosphere and orbits at the right distance from the sun for water to exist in a liquid state. Water is essential for life, and Earth seems to be the only world that has any. To be clear, the water molecule (H2O) is fairly abundant in the universe. But it is nearly always in either an ice or vapor state. Yet, the surface of Earth is 71% covered with the liquid form of this vital compound. As such, oceans, lakes, and rivers of water are (as far as we know) unique to Earth.
Earth has a dipole magnetic field, like Mercury, but a hundred times stronger. Magnetic fields naturally decay with time, and rather rapidly by secular standards. Hence, Earth’s magnetic field is confirmation of the biblical timescale. The exponential decay of Earth’s magnetic field suggests an age significantly less than 100,000 years.
Earth has geological features in common with the other planets. Earth has mountains and valleys, as do the other terrestrial planets. Earth has volcanos, much like Mars and Venus. Earth is made of rocky material with compositional similarities and differences from the other terrestrial planets.
Earth has a crust, a mantle, and a core – something that astronomers believe is true of all the terrestrial planets. But Earth’s crust appears to be unique, in that it is thin enough to be divided into plates that float on the mantle. Under the right conditions, these plates can move relative to one another – plate tectonics. As far as we know, Earth is the only planet with plate tectonics. This is extremely significant because most creation scientists believe that plate tectonic activity was the mechanism God used to power the global flood described in Genesis 7-8. God knew that the wickedness of mankind would increase, and that He would have to judge sin. So, God designed the Earth to be “floodable” – a feature apparently unique to Earth.
Like the other terrestrial planets, Earth has impact craters, apparently the result of meteor strikes. However, Earth has very few impact craters relative to the other terrestrial planets. Secularists believe that this is because plate tectonics and other geological activity have erased them. However, from a creationist perspective, it is possible that Earth never had that many craters – perhaps none at is origin. From Genesis we learn that God created the Earth on a different day from the other planets, and perhaps using a different mechanism. After all, God spent five of the six creation days forming and filling the Earth but He made all the other planets on day four (Genesis 1:1-2, 14-19, 31). Earth is three days older than any other planet.
We live in an amazing time. What a blessing that we have pictures of the Earth from above – something our ancient ancestors could have only imagined! Seeing the Earth from space reveals the astonishing beauty of this planet on which the Lord has placed the creatures that He made in His own image. Worlds like Mercury, Venus, and the moon certainly have a type of beauty. But it is a desolate beauty compared to the colorful richness of the Earth. We can so easily become complacent and take for granted the majestic beauty of this world with its mountains, oceans, rivers, waterfalls, and abundant fauna and flora. The other worlds of creation serve to remind us of the special beauty of our own planet.
Earth view from the International Space Station. (credit: NASA)
At an altitude of 200 miles, astronauts on the ISS are treated to a spectacular view of only a section of the Earth.
Earth has an unusual natural satellite – the moon. Although moons are very common in the solar system (six of the eight planets have moons), Earth’s moon has several characteristics that are remarkable. Although Earth’s moon is not the largest by any means, it is the largest moon relative to the size of its planet. That is, the diameter of the moon is over one fourth the diameter of Earth. The moon is about 400 times smaller than the sun, but is also 400 times closer to Earth than the sun is. For this reason, the moon appears about the same size as the sun as seen from the surface of Earth. This allows for total solar eclipses in which the moon fully covers the sun, with little left over. This configuration appears to be unique in the solar system. No other moon appears to be so precisely the size of the sun as seen from the surface of its planet.
The moon is tidally locked, meaning that it rotates at the same rate it revolves around Earth. Consequently, we always see the same side of the moon. In fact, all large moons do this, and so do many small ones. Such a configuration is energetically favorable, as it minimizes tidal torqueing on the moon. So, in this sense, the moon is quite typical.
The Earth and moon as seen from the Messenger spacecraft on its way to Mercury
However, the moon’s orbit is atypical and rather unique. All other large moons in our solar system, with one exception, orbit in the plane of their planet’s equator. But Earth’s moon orbits very near the ecliptic – the orbital plane of the Earth, which is tilted relative to the equator by 23.5 degrees. This makes solar and lunar eclipses more common than they would be otherwise. But the moon’s orbit is tilted about 5 degrees relative to the ecliptic. If it were not tilted, then we would get a solar and lunar eclipse every month, and perhaps this would make them seem less remarkable and simply commonplace. The moon’s unusual orbit apparently has a stabilizing effect on Earth’s tilt – preventing the Earth from toppling in a random fashion over long time-scales. Although the degree of Earth’s tilt is stabilized by the moon, the moon does cause the direction of Earth’s axial tilt to precess over millennia. Ancient star charts confirm this effect.
The moon benefits life on Earth in multiple ways. The moon causes tides in Earth’s oceans which help stir nutrients essential for life. Furthermore, many organisms navigate or otherwise depend on moonlight. The phases of the moon give us variety they allow us to experience some nights in which we can easily navigate by bright moonlight, and others where the sky is much darker so that we can explore the universe beyond. The moon also helps us to measure time. The period of the lunar orbit is why we have twelve months in a year – the moon goes through its phases twelve times in a year, or once per month. The word month is derived from the word moon.
In 1969, human beings first set foot upon the moon. I have always found the Apollo space program to be fascinating, and one of humanity’s greatest technological accomplishments. To travel 250,000 miles into space, to land, and then walk on the surface of another world is amazing. What would it be like to walk on the lifeless desolate surface of the moon? To then look up into the black sky and see the Earth delicately suspended upon nothing as a small blue marble – knowing that it is home to billions of people and countless living creatures? Twelve people have experienced this to date and there are plans to return.
The Splendor of Earth
When Voyager 1 passed into the outer regions of the solar system in 1990, it turned its camera inward, and photographed the planets – a sort of “family portrait” of the solar system. One of these images is the Earth, which from a distance of 3.7 billion miles appears as a tiny pale blue dot suspended in a sunbeam. It is a humbling picture, knowing that everyone who ever lived was confined to this tiny speck. The image was named the “pale blue dot” by Carl Sagan, who found the image very moving. So do I, but for very different reasons. To Sagan, the pale blue dot symbolized the utter insignificance of humanity. To me, it represents the magnificence of God and our utter dependence on Him. The same God who spoke the entire universe into existence deeply cares about the inhabitants of this pale blue dot, to the point that He was willing to die for them.
The pale blue dot. The small speck on the right-hand side of this image in the center of a sunbeam is Earth, as photographed by the Voyager 1 spacecraft from a distance of 3.7 billion miles.
This coming Sunday is Easter and many Christians will celebrate the resurrection of our Lord – the same Jesus who spoke the worlds into existence. No doubt the Lord made all these amazing worlds for His glory and also perhaps for our enjoyment. We can marvel at the magnificence of Saturn’s rings, the enormous size of Jupiter, the stunning brightness of Venus. But salvation did not occur on these worlds. It was not on Jupiter or Saturn where the Lord became man and died and rose again. No, Earth is where God placed those special creations made in His own image. Earth is where God became man and died our death. God proved His power over death by raising Jesus from the dead on this planet we call home. Far more amazing than man walking on the moon is God walking on the Earth! And He offers forgiveness and salvation to all who will repent and trust in Him. Let us be extra grateful this Sunday that the Lord visited this pale blue dot.
 The stars were made on day four of the creation week. The Hebrew word for “stars” (kokhavim) would include planets. Hence, all the celestial luminaries – all the stars, moons, and planets (except Earth) were made on day 4.
 The one exception is Triton, a moon of Neptune, which orbits neither in the ecliptic nor around Neptune’s equator. Furthermore, Triton orbits retrograde – opposite the direction Neptune rotates.
 The sun also influences tides on Earth, but solar tidal forces are three times weaker than lunar tidal effects.
 Six of the eight planets were photographed. Mercury was too close to the sun to be detected, and Mars was in an unfavorable position and phase. So, they are missing from the family portrait.