Powers of 10: the Australian version

In the footsteps of the classic short film, we explore the powers of 10 (click to zoom).

We begin with a classic NASA photograph of the Earth seen from Saturn, with a field of view (in the distance) about 100,000,000 km across. We zoom in by a factor of 10 to see the Earth and the Moon beside it. After three more such jumps (to 10,000 km), the Earth fills the frame. Three further jumps (to 10 km) zooms in on Melbourne, Australia. Two more jumps show us the city centre (1 km) and St Paul’s Cathedral (100 m). Another two jumps (to 1 m) give us a small boy on the grass beside the Cathedral. Two more give us the iris and pupil of his eye (1 cm) and a small patch of his retina (1 mm). Finally (at 100 µm or 0.1 mm), we see red blood cells inside a blood vessel in his retina. Fifteen jumps in all, zooming in by 1015.


New Horizons status check

The New Horizons spaceprobe, having given us some lovely pictures of Pluto in 2015, is on its way to the Kuiper belt. But what is the Kuiper belt? Named after Dutch-American astronomer Gerard Kuiper, the Kuiper belt is much like the asteroid belt, but much larger, about 15 times further out from the Sun, and far less well understood.

Initially, New Horizons is headed for the rock, or perhaps pair of rocks, (486958) 2014 MU69, which NASA has nicknamed Ultima Thule. The space probe is due to reach it on January 1st (which will be just short of 13 years after its launch). Currently, New Horizons is 6,360,000,000 km or 5.9 light-hours from Earth, and has recently completed a course-correction manoeuvre.

InSight mission to Mars launches on schedule

The InSight Mars lander launched yesterday from Vandenberg Air Force Base in California, and is scheduled to land on Mars on 26 November. There, it will probe beneath the surface and check for “marsquakes.”

Follow the progress of the mission here.

The InSight lander (JPL/NASA image)

Sunset on a flat earth

Earlier, I wrote a post on why people know that the earth is round. Evidence such as star movement, the obscuring of distant objects by the earth’s curvature, and aircraft flight times shows that the earth is not flat:

In this post, I want to temporarily put on the “hat” of a flat-earther. They claim that the sun is a “spotlight” which travels across a circular flat earth like this:

That is at least a well-defined model, crazy though it might be, and therefore can be tested. Here is a computer render of the spring sun at sunset on that assumption (as seen from, say, San Francisco, at the moment that the sun disappears from view):

Three obvious problems with the flat-earth model are visible in this picture:

  • The sun is much too small: only 40% of its noontime diameter (because it is 2.5 times as far away as at noon)
  • The sun appears oval, rather than circular, because the “spotlight” is being seen obliquely (click to zoom if you can’t see the shape)
  • The sun is much too high in the sky (24° above the horizon)

In reality, of course, the sun at sunset is a circular disk that gradually slips under the horizon. Oops. No, the earth is not flat.

Four worlds

The picture above shows four possible worlds: a (slightly oblate) sphere, a torus, a disc, and a Klein bottle (images © Anthony Dekker). The darkened end of the Klein bottle is shifted through the fourth dimension to connect with the other end, making it a one-sided surface (like the Möbius strip). How do we know which world we live in?

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.