Io
Today’s subject of pastoral science is moons, or rather one moon in particular. On Jan 26 of 2001 Bob Enyart spent part of his BEL radio broadcast showing how Jupiter’s moon Io is evidence for a recent creation. The BEL Program is titled “Astronomical Evidence”. Starting at 22:00 in the program, Bob says:
Never go camping with Bob
Two years later he repeated this claim. On May 28, 2003, in the BEL program titled “There goes a great American”, starting at 50:05 we hear this: Both of these accounts of Io by Bob are collections of misinformation, ranging from scientific nonsense to blatant untruths
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Evolutionists = Astrophysicists?
Note Bob’s hatred of evolution bleeds through into his commentary on Io: And I would let a single case of the use of the word “evolutionists” in place of astronomers pass as a slip of the tongue. But both times when he is discussing Io Bob makes that silly assertion. (In my experience, most astrophysicists are rather unconcerned with evolution. Most of them think it a viable theory, but the nitty-gritty details they leave to the biologists and geologists and such.)
Small???
Bob can fall back on the use of “relatively” if he wants. With that qualifier, if Io is smaller than any other moon, then his statement stands. And indeed it is “smaller”. In our solar system, Io is surpassed in size by 3 other moons, Ganymede (also orbiting Jupiter), Titan (orbiting Saturn), and Callisto (orbiting Jupiter). It is a little bigger than the moon circling the earth, and bigger than more than 100 other “moons” found in our solar system. So Io ranks number 4 in size out of hundreds of "moons". I put “moons” in quotes, because there is not a precise size at which we say “this is a moon, but that slightly smaller orbiting body is not”.
Still cooking after 6000 years
The most important part of Bob’s claim about Io, which he uses to show it must have been recently created, is: Bob makes this claim, but he says nothing about those three other pesky moons that are bigger than Io, nor about the heat in our moon. A major factor in radiative heat loss (meaning heat loss by emitting infra-red light, which is the mechanism almost all orbiting bodies use) is the ratio of how much hot matter is in the moon to the size of the area the heat can be emitted from. (Warning – a smidgeon of mathematics ahead.) The surface area of a sphere (which is the shape moons take) is proportional to the square of the radius. The volume of a sphere is proportional to the cube of the radius. In simple terms this means if one sphere has 2 times the radius that another sphere has, it will have 4 times the surface area and 8 times the volume.
Splattering wildlife
To illustrate by something familiar to all of us – think of throwing things out of airplanes. Throw out a little teeny bug – a 0.5 mm long wingless bug. (I realize bugs are not spheres, but the ratios of volume and surface area and radius are equally true for objects that are not spherical). This bug has immense surface area, at least compared to its volume (meaning its volume is really small). The bug’s weight is determined by its mass, which is dependent on how much bug there is – in other words – its volume. But the rate at which it falls through the air is determined by how much surface area the bug’s body has for the friction of the air to slow its fall. For the bug, the fall to the ground is an immense imposition on its time, since it drifts down very slowly. Long after being thrown out of the airplane, it finally wafts onto the ground, takes its bearings with it’s bug compass, and starts the long trek back to its bug home.
Let’s throw out something bigger next time – say a mouse. The mouse is 5 cm long (about 2 inches), or 100 times as long as the bug. That means it has about 10,000 times as much body area to slow it’s fall as the bug had, but its volume (and weight) is one million times that of the bug. That means the mouse is going to actually fall, not drift down. But even for the mouse the fall is casual enough that it has a chance to practice several minutes of aerial ballet, and is not seriously worried about any threat to its life from the fall. It may have some sore muscles on hitting the ground, but will probably be little the worse for wear.
But your Siamese cat dove out of the airplane trying to catch the mouse. Bad idea. 6 times the length of the mouse (sans tail) means 36 times the skin area, but also 216 times the weight. The cat looks in disappointment as it plummets past the mouse doing a pirouette. Soon the cat impacts the ground. After a minute it gets its breath back, checks for broken bones (a couple), limps away, and swears off mice as food.
The cat is lucky. The German Shepard that was after the cat was killed when it hit the ground some seconds before the cat hit. And you should never have grown so attached to your dog that you would jump after it. You were killed, and rather messily. Oh, the horse you were riding on that you rode out of the airplane – hardly recognizable as a horse, even a dead one. And your elephant literally splashed. Gore. All over. Gross.
The point of this macabre scenario is that the same mathematics (actually geometry) that is involved in making smaller animals fall more slowly also affects how fast moons would cool. Small things (animals and moons) have big surface area compared to their volume. For small animals that means lots of air friction to slow the fall of the light weight. For small moons that means lots of surface area to radiate the heat of the small moon away. Big animals, relatively little surface area, lots of weight, fall fast. Big moons, relatively little surface area to aid in cooling, lots of hot material inside, stays hot a long time. Or I could have avoided all the above and just said a big round hot rock sitting by itself will cool more slowly than a small one. Big moons stays hotter longer than small ones.
God’s Selective Residual Heat
The billy-goat gruff of moons is Jupiter’s Ganymede, with a radius of 2631 km. Titan comes in with a radius of 2575 km. Callisto has 2400 km. And then we come to Io’s 1815 km radius. Our moon is close behind, with a radius of 1738 km. Doing the math and seeing how these sizes would affect cooling rates, we find that Ganymede’s cooling rate would be 0.57 times that of Io, Titan’s is 0.59 times that of Io, and Callisto’s is 0.65. Our moon would cool at 1.06 times that of Io. These figures presume similar compositions for the moons, which is not strictly true. But the point is clear, if Io has substantial residual heat from a recent creation, then several other moons should likewise. And they don’t.
I will leave it to Bob to explain why his God chose to play favorites with hot moons and cold moons. But for real science, the answer is known.
5 important facts
To lay the necessary scientific foundation, I need to briefly discuss some relevant concepts:
1. Io’s Orbital Radius
2. Jupiter’s Gravity
3. Centrifugal Force
4. Balancing Forces
Io’s Orbital Radius
Io orbits at a distance of 422,000 km from the center of Jupiter. By contrast, our moon orbits at a distance of 384,000 km from the center of the earth. (Of interest, but not of particular import to the point being made, is that even though Io is much farther from Jupiter’s center than our moon is from the earth’s center, yet Io is closer to the surface of Jupiter than our moon is to the earth. This is because Jupiter is really big compared to the earth.) I need to note that the above orbital radii are nominal distances, since both Io and our moon do not travel in perfect circles.
Jupiter’s Gravity
Jupiter is big, so the strength of Jupiter’s gravity at Io’s distance is about 300 times as strong as the strength of the earth’s gravity at the moon’s distance.
Centrifugal Force
Centrifugal force is the force that pulls a rotating object away from the center. Centrifugal force increases as the distance from center increases (all else being the same), and it increases as the square of rotational speed.
Balancing Forces
To maintain its orbit, Io’s centrifugal force must exactly counteract Jupiter’s gravity. Therefore, Io orbits Jupiter 17 times as fast as our moon orbits the earth. Io zips completely around Jupiter in a couple of days. This means Io’s centrifugal force is about 300 times as strong as our moon’s centrifugal force.
But there is an important point to consider here. The distance from the center of Jupiter to the near side of Io is slightly less than the distance to the far side. This means the strength of Jupiter’s gravity on the near side is slightly higher than on the far side.
But at the same time, the far side of Io is feeling a stronger centrifugal force opposing gravity than the near side does. This is because the far side is farther away from Jupiter, yet it orbits Jupiter in the same time as the near side. It is similar to attaching a rock to the end of a string and swinging it around your head. If you let the string out a little but keep turning at the same rate, you will feel more tug on the string.
The differences felt by the near and far sides of Io are also felt by our moon, but since the gravitational field and orbital speeds are so much less, the differences are seldom of import.
Squashing a moon
This differential of gravitational pull on Io’s near side and centrifugal force on Io’s far side actually pulls Io into a slightly squashed shape.
The Musical moons
Even on Io, this squashed shape would not be important, except that Io has buddies. Io is the innermost of 4 large moons that circle Jupiter. Io and the next two moons out (Europa and Ganymede) maintain an interesting orbital relationship to each other. While Ganymede, quite a distance from Jupiter, orbits Jupiter once, Europa makes 2 trips around Jupiter, and Io makes 4. These 3 moons maintain a resonance in their orbits, like octaves in music.
Since Io zips around Jupiter the fastest, it is regularly imposing itself between Europa and Jupiter or Ganymede and Jupiter, and then continuing on to the far side of Jupiter and back again. Europa and Ganymede are very small compared to Jupiter, but the gravitational pull they have on Io as it swings under them pulls it very slightly up towards them, and away from Jupiter. Then as Io speeds on, it moves on around Jupiter where the only nearby gravity is Jupiter’s own, so Io is pulled down into its natural orbital distance.
This periodic (every couple of days) tug-of-war that Io undergoes is the source of its heat. Remember that Io is already in a gravitational field 300 times the strength of our moons. So even minor orbital perturbations cause strengthening and lessening of the other tug-or-war between gravity and centrifugal force that distorts Io’s shape. The net result is that Io is constantly being stretched, then relaxed, then stretched, and relaxed.
This constant changing in the forces felt across Io causes a type of tide. To get a feeling for the magnitude of this tide, remember that on earth the ocean tides are normally about a yard high. There are also tides in the land on earth, but they are extremely small (about 0.5 mm or 1/50th inch). But on Io, with no ocean, the tide is strictly on the land, and is the height of a 30-story building, 300 feet. This major incessant stretching and relaxing of the shape of Io generates immense internal frictional heat. This heating of Io has (and will) continue as long as Io’s orbit is oscillating closer to and farther from Jupiter.
Who knew what when?
Bob portrays NASA as having to come up with some quick excuses when volcanoes were first spotted on Io: Bob’s knowledge of scientific history is no better than his understanding of science itself. Did the volcanoes on Io catch the scientific community by surprise? Yeah, some of them, me included. But I, and the vast majority of scientists do not, and can not, keep up with all the expanding frontiers of science. That does not indict the astronomical community, nor NASA. In fact, directly contradicting Bob’s claim was an interesting article that was published in the journal Science and sent to thousands of subscribers, BEFORE the volcanoes were ever seen. This article is in the Mar 2nd issue, 1979. That is about a week before the first voyager spacecraft reached Io and spotted the first volcano. The article is titled “Melting of Io by Tidal Dissipation”. The abstract reads: Within the body of the article is this: So we have the publication and dissemination of thousands of copies of a major peer-reviewed scientific journal specifically addressing the likelihood of volcanoes on Io, before a single one had ever been seen. How well does that comport with the broadcast claim from a particular pastor that: “And of course after the fact NASA has to say, ‘Oh yeah, well, we knew that.’ Well they didn’t know that. They had to come up with a reason why it’s still hot”? Bob’s claim of ignorance on NASA’s part comes almost a quarter century after the data falsifying it was widely available. Ignorance or intentional deception? You decide.
The Icing on The Cake
Bob himself turned out to be one of his own worst enemies on this. Because on the BEL recording of May 28, 2003, less than a minute after Bob finished giving his corrupted version of Io’s lunar science, he highly recommended the purchase of a Creationist Book written by a PhD Creationist, Dr. Walt Brown: I took Bob’s recommendation and padded Dr. Brown’s pocket with a bit of my money. Most interesting. Dr. Brown talks a little about Io and its heat. What does he say? It is caused by
tidal interaction with Jupiter. I must admit, it was delicious listening to Bob expound nonsense about Io, then turn right around and give effusive praise to a text from a Christian fundamentalist scientist who disagrees with what Bob just said. The end of a perfect day.
