Earthrise / Christmas

Earthrise, taken aboard Apollo 8 by Bill Anders on 24 December 1968 (NASA photo).

With Christmas coming up, it seems appropriate to post this iconic photograph, taken by Lunar Module Pilot Bill Anders on 24 December 1968, while orbiting the moon in Apollo 8. The team also did a live television broadcast, in which Anders read from Genesis:

For all the people on Earth the crew of Apollo 8 has a message we would like to send you: In the beginning God created the heaven and the earth. And the earth was without form, and void; and darkness was upon the face of the deep. And the Spirit of God moved upon the face of the waters. And God said, Let there be light: and there was light. And God saw the light, that it was good: and God divided the light from the darkness.

Command Module Pilot Jim Lovell continued: “And God called the light Day, and the darkness he called Night. And the evening and the morning were the first day. And God said, Let there be a firmament in the midst of the waters, and let it divide the waters from the waters. And God made the firmament, and divided the waters which were under the firmament from the waters which were above the firmament: and it was so. And God called the firmament Heaven. And the evening and the morning were the second day.

Commander Frank Borman closed: “And God said, Let the waters under the heavens be gathered together unto one place, and let the dry land appear: and it was so. And God called the dry land Earth; and the gathering together of the waters called he Seas: and God saw that it was good. And from the crew of Apollo 8, we close with good night, good luck, a Merry Christmas, and God bless all of you – all of you on the good Earth.

And the same from me.


Her pale fire she snatches from the sun

Shakespeare writes “the moon’s an arrant thief, and her pale fire she snatches from the sun” (Timon of Athens, Act 4, Scene 3). He is, of course correct. The moon merely reflects sunlight, and produces no light of its own. One way of telling this is that moonlight actually displays the same telltale absorption spectrum as sunlight:

Our eyes tend to perceive moonlight as “blueish” or “silvery,” but that is because of the way our eyes work at low light levels. Long-exposure photographs under moonlight, like this one, look much like daytime shots:

Anaxagoras (499–428 BC) seems to have been the first to discover that the moon shines only by reflected light:

Anaxagoras also explained that solar eclipses occur when the moon moves between the earth and the sun. Total solar eclipses are dark precisely because the moon produces no light of its own:

Lunar eclipse, October 2014

Here it is, taken about half an hour ago, just as totality was beginning:

Update: this one was taken a little later, and with a longer exposure:


Four blood moons? Really?

In recent times, there has been a degree of interest – particularly within the USA – in so-called “blood moons” (as in the above book). Although this phrase is intended to recall Biblical texts such as Joel 3:21 (“The sun shall be turned to darkness, and the moon to blood, before the great and awesome day of the Lord comes”), it actually refers to ordinary lunar eclipses. Lunar eclipses are great to watch (see photo below), but are actually not particularly uncommon – see this list.

Much has been made of the “coincidence” of lunar eclipses occurring on major Jewish holidays. However, the geometry of lunar eclipses (see below) requires the moon to be on the opposite side of the earth from the sun, which means that lunar eclipses only occur on full moons. Furthermore, the Jewish calendar is a lunar one, so that several major holidays – such as Passover (15th of Nisan), Purim (in Jerusalem, 15th of Adar), and Sukkot (15th of Tishrei) – always occur on full moons. Lunar eclipses have therefore occurred on major Jewish holidays many times over the past two millennia.

Basically, the whole theory makes about as much sense as the panic of 2012. But, of course, that’s no reason not to watch the next lunar eclipse, on 8 October:


Sleeping in the moonlight… or not

Moritz von Schwind, Selene and Endymion‎, 1831

In 1609, the English writer Thomas Dekker wrote these lines in praise of sleep:

For do but consider what an excellent thing sleep is: it is so inestimable a jewel, that, if a tyrant would give his crown for an hour’s slumber, it cannot be bought … sleep is that golden chain that ties health and our bodies together. Who complains of want, of wounds, of cares, of great men’s oppressions, of captivity, whilst he sleepeth? Beggars in their beds take as much pleasure as kings. Can we therefore surfeit on this delicate ambrosia? Can we drink too much of that, whereof to taste too little tumbles us into a churchyard; and to use it but indifferently throws us into Bedlam? No, no. Look upon Endymion, the Moon’s minion, who slept threescore and fifteen years, and was not a hair the worse for it. Can lying abed till noon then, being not the threescore and fifteen thousandth part of his nap, be hurtful?

The modern prevalence of jet travel and shift work has prompted considerable research in sleep and sleep-related issues, since many travellers and shift-workers struggle to find effective strategies for managing sleep. Thomas Dekker is certainly correct about the effects which sleep deprivation can have – indeed, sleep deprivation can be as debilitating as high blood alcohol concentration.

Full moon (from Weird Tales, Sept 1941)

However, although Selene (the Moon) caused Endymion to sleep, she is unlikely to be of any help here. Past studies have shown that the full moon reduces hours slept (although a recent study finds no effect), and this may underlie traditional beliefs in lunacy caused by the moon… not to mention the legends about lycanthropy.

This post was reblogged and updated from Human Science Explored


Surface areas of the solar system

Here is another gem from XKCD: surface areas of the various solid objects in the solar system – excluding the gasballs Jupiter, Saturn, Uranus, and Neptune, but including their moons (click to zoom). As might be expected from images of the planets, Earth and Venus have the lion’s share of the real estate:


Choose your favourite NASA LRO image of the moon

The Lunar Reconnaissance Orbiter has been photographing the Moon since 2009, and to celebrate its fifth anniversary, NASA is asking people to vote for one of the five fabulous pictures above (click image to go to voting website, with larger versions of the pictures). Which one do you think is the most beautiful?