Can it be a coincidence that although the moon is 400 times smaller than the sun, it is also 400 times closer than the sun, such that the apparent size of the moon equals that of the sun?

I would say yes it is a coincidence, although fundamentalist religious people may disagree (but they could make a lot stronger case for an eclipse loving God using this fact than some of the other unscientific claims about the age of the earth and what fossils tell us...). In any case, thanks to this fact, we have eclipses that allow scientists to get a good look at and study the corona (atmosphere) of the sun.

Yes, I watched an episode of a documentary series about the universe and I learned a lot about the sun, even things I did not already know.


Right now there is a massive heat wave (and drought) across most of the U.S. Of course, there is no global warming, and even if there were, it would not be caused by human activity.

Oh man, I still cannot say that with a straight face.

But that is neither here nor there. This morning as I was drinking ice cold water to stay cool, I got to thinking about temperature, and more importantly the sensory experience of temperature.

Hot and cold is, physically speaking, really nothing more than the excitation of atoms and molecules in a substance. Cold things have less molecular excitation and hot things have more. By excitation, we are talking about the motion of atoms and to some extent the excitation of electrons (generating radiant heat, such as that given off by a hot surface).

But the sensation of temperature by an organism such as you or me, is quite fascinating. We don't think about atomic excitation when we experience temperature. We only sense cold or hot. That means we evolved cellular and molecular machinery to translate atomic excitation into the subjective experience of temperature. Temperature has meaning and value as a result. A rock doesn't care if it is hot or cold.

Our temperature sensing neurons basically translate the physical energy of an object into action potentials, the combined strength of which is determined by the energy of the object. These signals are transmitted to the brain, where they are processed and subjectively interpreted as hot or cold.

I say subjectively, because there is a relativity to the interpretation of temperature sense, and indeed all sense. For example, in the winter time, when the temperature rises to, say, 50 degrees, we think it is a balmy warm winter day in a relative sense. But a 50 degree day in mid summer would be downright chilly.

If you go outside in the winter without gloves and your hands get really cold, you can run them under luke warm water and it will feel "hot" at first.

Temperature is a physical absolute when measured as atomic excitation with objective scientific instruments. But try explaining that to your brain. Temperature is totally a subjective thing when it comes to experience.