Young-earth "proof" #10: Jupiter and Saturn are cooling off rather rapidly. Since they still give off internal heat, they cannot be billions of years old.
10. Jupiter is not cooling off that rapidly! Based on the fact that Jupiter is radiating twice as much energy as it receives from the Sun, and given its mass and other data, we can calculate the heat loss. "A simple calculation indicates that the average temperature of the interior of Jupiter falls by only about a millionth of a kelvin per year." (Chaisson and McMillan, 1993, p.269). (A drop of one kelvin is equal to a drop of 1.8 degrees Fahrenheit.) In short, Jupiter is big enough that it could still be radiating heat trapped during its formation 4.5 billion years ago. Thus, there's no problem there.
Saturn, which radiates almost three times more energy than it receives from the Sun, is a more complicated case as it is not massive enough to retain its primeval heat of formation 4.5 billion years ago.
The explanation for this strange state of affairs, first suggested by Ed Salpeter of Cornell and David Stevenson of Caltech, also explains the mystery of Saturn's apparent helium deficit, all in one neat package. At the temperatures and high pressures found in Jupiter's interior, liquid helium dissolves in liquid hydrogen. In Saturn, where the internal temperature is lower, the helium doesn't dissolve so easily, and tends to form droplets instead. The phenomenon is familiar to cooks who know that it is generally much easier to dissolve ingredients in hot liquids than in cold ones. Saturn probably started out with a fairly uniform mix of hydrogen and helium, but the helium tended to condense out of the surrounding hydrogen, much as water vapor condenses out of Earth's atmosphere to form a mist. The amount of helium condensation was greatest in the planet's cool outer layers, where the mist turned to rain about 2 billion years ago. A light shower of liquid helium has been falling through Saturn's interior ever since. This helium precipitation is responsible for depleting the outer layers of their helium content. ...As the helium sinks toward the center, the planet's gravitational field compresses it and heats it up. [Saturn is a "gas giant," a planet without a surface. As the helium in the outer layers "rained" down into the lower levels it was squeezed into a smaller space due to gravity, which caused the helium atoms to bump into each other more often. That is, the helium heated up according to Boyle's law. - D.M.]
You may object that the above is just a "theory," but this hypothesis comes with realistic, detailed mathematical and physical explanations something almost unheard of in creationist literature. We now have a plausible explanation for Saturn's heat output. Therefore, Saturn presents no problem with respect to the above creationist argument.