All objects absorb energy from their environment, and re-emit that energy as radiation until they are in equilibrium with that environment. Energy in = energy out. In general, as a body heats up, it emits radiation, usually in the far infrared at room temperature, but molten metals also glow in the visible range, from dull red to white hot. A warm object gives off energy at all wavelengths, but the shape of that spectrum, the total energy given off, and the wavelength where the peak energy is emitted all depend primarily on the temperature.

Every substance’s radiation curve for any temperature will vary from substance to substance, due to quantum interactions in the material, but the theoretical average, the “perfect radiator” is the black body radiator. It’s called a “black body” because it absorbs all the radiation that hits it, regardless of wavelength, and then re-emits it according to the spectrum I mentioned above for whatever temperature it is. Black soot is a pretty good approximation to a black body, in the laboratory, they usually use a spherical cavity coated on the inside with soot, and the opening into the cavity is the “cavity radiator” which is a synonymous term to “black body radiator”. Radiation directed into the cavity will heat it up, and energy will come out of the opening at a spectrum very similar to a theoretical black body curve.

Most common materials behave fairly closely to a black body, even stars have a spectrum pretty close to a black body. So if you can measure a spectrum’s shape, you have a pretty good idea of what a body’s “effective temperature” is. That’s how we know the sun’s surface temperature. It’s total spectrum is close to a black-body spectrum for 6000 deg K although it may deviate from that somewhat at different wavelengths. (Peak radiation is in the yellow-white).

And now comes the good part…If you aim a radio telescope at empty space, where there is absolutely nothing, you get a tiny whisper of microwave radiation: the remnant glow of the big bang, it is the flash of creation, redshifted down into the radio region. It is the spectrum of a black-body radiator at 3 degrees Kelvin (about -268 C) It is our primary piece of evidence that there was a big bang. Russian theorists predicted it, and American physicists discovered it, in 1964, the year I graduated from high school and the Beatles were on Ed Sullivan.

You measure temperature with a thermometer, and if you stick a thermometer sensitive enough to measure that temperature into space, so it is exposed to no other sources of energy or matter, it will cool off to 3 deg K and then stay there, in equilibrium with its environment.

It’s always some smart-ass perfesser and a devout Christian student who puts him in his place.

And its always a Christian. Apparently Jews, Muslims and Zoroastrians don’t believe in the right god.

Personally, I don’t see much differnce between a belief in God and a belief in Santa Claus. I don’t see that much differnce between their believers, either.

P. Z. Myers took it to pieces some time ago, but I can’t find the link.

Snope took it apart as well: http://www.snopes.com/religion/einstein.asp

Found a different version where the student learns logic:
http://depressingfacts.tumblr.com/post/6490229024/what-the-real-dialogue-with-a-theist-aka-the-albert

Hope the student doesn’t get a drug-resistant infection and learn about evolution of bacteria. A CT scan or MRI shows the brain quite nicely.

There are a number of examples of evolution occurring in front of people. Physical changes in response to the environment. That soot-colored moth in Europe comes to mind, but I could track others if I had to. The Galapagos Islands kind of rub our noses in it.

God watches the fall of every sparrow. Nobody ever said he catches them.