Astronomy/planet core temps
I enjoyed your article on how Core Temps of planets decline, recently I heard that they had actually started to increase? have you heard of any notable changes in the cores of other planets thanks Arthur
There is no evidence that the actual temperatures have increased at any time in recent history. What has happened is that gravitational studies have indicated that the surfaces of Mars and Mercury are more "flexible" than previously expected, indicating that they have warmer cores than had been generally thought possible. So if you compare estimated temperatures from earlier studies to current estimated temperatures, the numbers have gone up a bit; but the actual temperatures are almost certainly the same now as they were a century or so ago.
Of course, over very long periods of time the temperatures should change. If they are a remnant of earlier warmer temperatures, maintained by the insulating properties of the outer solid rock layer, internal temperatures should gradually decrease. But if they are maintained by internal radioactivity, then they could increase. For instance, one "camp" of planetary geologists thinks that Venus might be producing heat through radioactive decay faster than that heat can move through its outer rocky layers, in which case the core would be heating up. Since there is no current way to know how much radioactive heating is going on inside the planet, or how fast any internal heat is moving through the outer layers, whether Venus is heating up or cooling off over very long periods of time is unknown, and as a result other "camps" disagree. And though not as contentious, the same thing applies to the other planets.
So my guess would be that if you have read any statements about the planets' cores heating up, they are probably based on theoretical models that can't be verified at the current time.
(I did a quick edit on the above, so hopefully it is clear and correct; but I have to leave in a few minutes, so I haven't checked it as thoroughly as I'd like. If you find that it is not as clear as it should be, please let me know and I'll try to fix the problem when I get back.)