Thanks, Ray. You are correct, but my sloppy use of the term was to imply a very rapid diminishing of brightness.

Larry S.

I’m finally getting around to checking out the new blogs. Very much enjoyed your “How bright is the sun?” Just want to make a quick comment on the sun’s size as seen from Mercury. Even though the sun’s angular diameter would be some 3 times larger than here on Earth, it’s disk size would be 9 times larger (diameter squared).

That would probably be pretty impressive!

Bruce

Your article was fascinating. However, since part of the article focused on accuracy in the media, I do have an accuracy quibble. I’ve been taught differently about the meaning of “exponential” variation.

The article states that the light intensity diminishes as the square of the distance, and this is called “exponentially.” I don’t believe that that is accurate. Varying as the square of distance or the hundredth power of distance is not considered exponential. To be exponential, the variable has to itself be part of the exponent. With light intensity versus distance, the distance is at the base, and a constant, 2, is in the exponent. In other words, light intensity varies as d to the power of two, or I = d^2.

If it were the other way around, if the light intensity from a point source varied as two to the power of the distance, I = 2^d, then the variation would be exponential. (There is nothing magic about the 2, it could be 3^d, e^d, or any other number of course.)

For example, on Saturn, which is ten times the distance from the sun that the earth is, the sun’s apparent intensity would be 10^2, or 100 times less than on earth. If the variation were exponential, the ratio of intensities would be 2^10, or 1024.

The classic story of the inventor of chess, who asked that a single grain of wheat be placed on the first square of the checkerboard, and then doubled on each of the remaining squares, was trying to take advantage of exponential growth. The final square would have had 2^63 grains, or roughly 9 with 18 zeros after it. As the story goes, the king realized he’d been conned long before they got to square 64, and had the guy beheaded.

That minor misstatement didn’t affect any of the numbers in the table or the conclusions of the article, of course. I just couldn’t resist.
Ray

Thanks for the links. I’ll check them out!

Larry S.

Today I get new information that VY Canis Majoris (VY CMa) is a red hypergiant star.
Please check these links
the largest known stars and one of the most luminous stars known.

MES

So we can be near the Sun or any other star and it wouldn’t necessarily be a violation as long as the bulk properties of space even out over large distances in all directions. Even if we were orbiting the brightest star in the Universe, that could be pure coincidence. Some star has to be the brightest, right? Surely that does not imply a violation in itself. I am assuming that there is a brightest star in the Universe, but not that it occupies any preferential location.

Now, if we were the only life in the Universe, and we orbited the truly brightest star, that might say something. But we could never be sure. We could no more prove that we were the only life in the Universe than we can prove that God doesn’t exist. Just can’t be done.

L.

Unless, of course, a precursor for human life were that it needed the brightness of the galaxy’s brightest star in order to evolve!

I sense a science fiction story idea in the making …

Deborah