Venus Moon

Compare with Jupiter's moons. Beyond that, no significant changes to any of those fields.

"If Venus had a moon similar to ours, what would it look like from Earth..." From the Earth, I suspect it might look something like this: O^.

"...how would its appearance in the sky have changed the history of science, religion, technology etc." For one thing, LynDoor™ Industries would not be the world leader in technology pirating distribution that they have become. So, we thank our lucky stars that Venus has no natural satellite!

Without the aid of a telescope people cannot see that Venus goes through phases like the moon. We do perceive the change in brightness that happens from Venusian phase changes but we cannot discern the shape. Our moon has a diameter about 1/4 the size of the Earth. So resolving a moon 1/4 the size of Venus orbiting this planet between us and the sun with the naked eye is very unlikely. There might be an added cycling in the perceived Venus brightness that spurs a different story about this wanderer in mythology.

Redfred

Surely Venus is easily resolved after sunset or before sunrise as a very bright object. I would have thought that a moon would have been clearly visible at the size mentioned. The phases were first resolved in 1610 apparently with the first telescope although wiki says the extreme crescent is just about visible with excellent eyesight. There is a stream of thought that suggests mans need to explain and predict eclipses promoted the growth of scientific reasoning. I wonder if a moon around venus may have likewise pushed us to answering fundamental questions.

It would not have been visible from the earth, until the invention of the Lunascope®, by LynDoor™Industries in 1993, therefore it would not have affected any of the things you list.

You see, there is a moon there, but it is always on the opposite side so we'd never have seen it, until 1993.

A moon of Venus, if it were the same size as ours and the same distance, should be easily visible with the naked eye, I should think. Venus is about 30 million miles (roughly) at its closest approach, and so a degree is about half a million miles at that distance. Our moon is a quarter million miles away, so it would be separated by about half a degree at that distance, or about the width of our moon in the sky. Our moon is about 1/16 the area of the earth, so Venus's moon would be much dimmer than Venus, but still quite visible.

How it would affect our mythology is anybody's guess.

One sixteenth as bright as Venus is still very bright. Since Venus has a magnitude of around -4.4, its moon would have a magnitude of -1.4 (each step is 2.512 times as bright as the the previous one, and 2.512 x 2.512 x 2.512 = 15.85). It would have the approximate brightness or Sirius, the brightest star in the sky. Clearly the ancient astronomers would have been very aware of it.

Another thought: With a visible example of a moon circling another planet, the Heliocentric view would have evolved earlier without having to wait for Galileo to point his telescope at Jupiter.

Maybe so. It's impossible to say. The ancients might simply have decided that 'Venus and its child' follow a path together around the Earth, etc. Being able to see Venus' phases helped explain that it is heliocentric.

After the invention of the clock, and once the heliocentric nature of orbits was understood, the natural philosophers of the day might have noticed the lag in Venus' companion's path around Venus when it was at superior conjunction vs at inferior conjunction, and discovered the speed of light sooner.

While a minute of arc is considered the nominal resolution of the naked eye, I still doubt that this moon would even be recognized as Venus' child. The Wikipedia link includes this reference

1. ^ Zezong, Xi, "The Discovery of Jupiter's Satellite Made by Gan De 2000 years Before Galileo", Chinese Physics 2 (3) (1982): 664-67.

This observation was accomplished without the use of a telescope. Without a telescope allowing anyone's eye the ability to clearly discern a moon around another planet this early discovery of the moons of Jupiter fell into obscurity. On a related point, the change in brightness that all of the visible planets exhibit baffled Greek astronomy until Appolonius of Perga proposed the idea that these objects change their distance from the Earth. Yet this significant concept toward a heliocentric system instead of a geocentric system remained trapped in only academic circles until observations with a telescope became possible.

My point here is that until a valuable tool (telescope) existed that anyone could use, any data that disagreed with established folklore was ignored. I believe an alternate reality with a moon around Venus would not have discovered a heliocentric explanation faster due to this moon.

I agree having an inferior planet with a moon might have revealed many things about light sooner. Along with the velocity of light being discovered sooner, might the gravitational effects on light been noticed sooner.

That's pretty amazing to have good enough eyesight to pick out one of Jupiter's moons. Scientific results need to be independently verified, which could be a problem if nobody else can see it. (I can see a moon near not only most planets but stars also - I think it's called astigmatism ).

yes probably it would

Has anyone considered that the proximity to the sun nearly rules out a stable orbit for a moon of Venus? I have not done the math, but I expect the orbital perturbation to be extremely large due to oscillation in solar attraction of this moon. If the orbit were to become eccentric enough, eventually the moon would collide with Venus, end of story. If is indeed a mightly big word in such a case. I leave others to work on the math, who are accustomed to these calculations.

You bring to my warped mind an additional question. How much of a stabilizing effect does the ocean tides provide to prevent our moon from being destabilized by the sun? Would arid Venus lose her moon because no tidal action can dampen the tangential from orbit tug of the sun?

I am too challenged to calculate the escape velocity of a moon (earth sized) orbiting Venus but I suspect it would be similar to earth's moon at 2.4 km/sec. So yes, IMO Venus could lose its moon and the orbit of such moon may even interfere with the Earth Orbit. Hope no collision.

The tides on Venus would likely cause its dense Atmosphere to expand and perhaps even transport to the moon. I would also think an expanded atmosphere would increase the Albedo effect and and the magnitude of brightness for both Venus and its moon. Venus and its moon would be very visible from earth. An increase in the size of the atmosphere on Venus would also lower its density and perhaps cool the surface of Venus (it is about 750 degrees C now).

Observers on earth would discover Venutians and declare war. NASA and all countries would increase space study and space travel. We would make movies called, "The Attack of the Venutians".

I think there may indeed be a "Goldilocks" effect involved in the stability of Earth - Luna system. Einstein used his corrected theory (actually his original 1914 theory) (that Hilland nearly scooped him with by the way), to exactly solve the erratic "rose-petal" orbit of Mercury (the orbit precesses out of the planetary system "plane") due to the extent to which the sun distorts space (gravity well) near Mercury. Obviously, the theory also predicted shift in stellar apparent position during total solar eclipse at precisely 1.75 arc seconds (the measurements were made with especially prepared telescopic cameras, and a measurement system of the plates produced).

As far as the tides stabilizing Luna's orbit, maybe. But I consider more important the fact that Luna's pull on Earth stabilized rotation down to a 24 hour day. Otherwise, how would the trains keep on schedule?

Some very thought provoking ideas which are very interesting. Perhaps Mercury is the moon that escaped from Venus. Would it also mean that the progression to intelligent life on other planets may depend on their need to explain eclipses and thus intelligent life would be more commonly developed on planets further away from their stars gravitational pull. Pure conjecture of course. I wonder if the recently discovered Jupiter type planets close in to their stars could sustain moons with all that gravitational tussle going on. If not then how did our Jupiter collect its moons if it migrated from close in to its present position as some people think.

What if Proto-Venus had a moon - takes a specific type of collision so it would not really be proto-venus - but lost this moon to Proto-Earth (yes Earth has been made over again - even says so in the Bible. (if you have eyes to see this). This moon may have been large, may in fact have been the pandora that formed the Earth-Luna system by a glancing collision.

Venus is nearly (0.72) as far from the sun as the earth. Are you saying that holding our moon in a stable orbit is due to another one of the "Goldilocks factors"?

Since I have not actually done the calculations, how could I possibly be definite about it? I think someone needs to apply Einstein's gravity equation here to see if there is something about the solar gravity well that might perturb a moon's orbit just enough.

I would be a Baptist, and technology would not have evolved beyond the chess board.

The effects on religion science and technology may be marginal but the effect on science fiction writing would be tremendous. Venusians would have invaded the Venusianetts (the inhabitants of Venus's moon) rather than turning their attention to Earth. With a far more compact and thus integrated military-industrial structure, the Venusianetts would naturally have had a technological edge. Bombarding Venus with bolts of CO², SO² and other greenhouse gasses they would quickly have turned Venus into the arid dust bowl that we see today. Being much closer to the Sun than ourselves, their solar extractors would provide almost limitless power. Enough in fact to cloak their moon from any other potential invaders from the outer solar system, which is of course why we cannot observe it.

I just checked yesterday morning, and Venus does have a moon! Actually, its the planet Saturn, but it's just about the right distance and brightness you would expect. I thought it was a funny coincidence.

Noticed that myself! Ha!