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A Rainbow of beetles, a closer Moon, big bang picture taking

Q: The bodies of beetles display a great variety of colors. Describe an experiment I could do to determine the cause of a beetle’s color. Is it due to organic pigments in the cuticle [skin], interference patterns, or heavy metals in the cuticle? (Sara, Canberra, Australia)

A: The colors are due to skin dyes and light interference (but not heavy metals). The rainbow of beetle colors arises from those two sources.

A Japanese Beetle displays her brilliant metallic green body and copper-brown wing covers. [© Scott Camazine 2003, used with permission]

Light interference. An iridescent Japanese Beetle lands among a flower’s petals. Light shines down upon the transparent outer-most layers of her skin. The light bounces and bends as it filters through microscopic spaces in chitin layers to the green pigment below. (Chitin is a fibrous material analogous to fiberglass — layered on, tough, and light.)

The jumbling light waves superimpose one on another like colliding rings of water waves from successively dropped pebbles. The mishmash of waves causes some crests to reinforce, others to cancel. Likewise, troughs deepen, others fill.

When waves reinforce (higher crests, deeper troughs), the light intensifies. When they cancel, the light diminishes. The resulting patterns hit my eyes and I see her body as a shimmering metallic green. The colors change as I shift my viewpoint much as they do when I look at and tilt a CD.

"Some green beetles, like Sternocera aquisignata vary from dull bronze to bright emerald to blue and violet as the light shifts," says David J. Shetlar, entomologist at Ohio State University.

Pigments. Beetle skin has dyes, just as humans have. Melanins produce browns and blacks. Carotenoids make reds, oranges, and yellows. Anthocyans result in blue, purple, and scarlet. Many pigments, like these, come from plants that a larva eats. He retains the pigment as he changes from larva to adult.

An experiment. We can determine the cause of a beetle’s color by looking at the creature from several viewpoints. If he doesn’t appear to change colors, then the coloration is due simply to pigments.

By the way, we recently found in Germany one of the oldest fossils that still retains its original color. The fossilized animal is a brilliant metallic-blue beetle, dead 50 million years. Its original hard chitin is still intact, interfering with light, and dazzling the eye.

Further Surfing:

WebExhibits: Causes of color

National Geographic News: Beetle find is one of the oldest colored fossils by John Pickrell

A closer Moon

Q: I just read the Q&A for "Goodbye Moon" and was wondering... If the moon is receding from earth, how close has the moon been to earth since its creation? (Mark, Salt Lake City, Utah)

A: As you read in my "Goodbye Moon" answer, the Moon is now about 30 Earth diameters from Earth.

The oldest record of Earth’s ocean tides ever found is from South African rocks, 3.2 billion years old. The rocks indicate that the Moon was 25-percent closer to Earth then — only 23 Earth diameters away. It may have been even closer but that’s as close as we have supporting evidence.

Of course, you could claim that, when Moon was created (4.6 billion years ago), it was zero distance away. Apparently, a Mars-sized object blasted into the proto-Earth and the debris gradually gathered together to form the Moon. "Before then, most of the two bodies were no distance from each other at all," says Robert Massey, astronomer at the Royal Observatory Greenwich.

Tides enlarge Moon’s orbit [April Holladay]

You might wonder why the Moon moved away from Earth, in the first place. The Moon and the tides it creates on Earth are the culprit. As you know, the Moon pulls more on that part of Earth closest to the Moon (than it does on the far side of Earth). The greater pull stretches the near land, bulging it by as much as a foot (30 centimeters) toward the Moon. (That creates one high tide.)

The Earth, however, rotates faster than this happens because stretching land is slow business. Earth’s crust resists. So the bulge is actually a bit ahead of the Earth-Moon line.

This bulge — sticking out from Earth — has mass and therefore gravity. So the bulge pulls forward on the Moon and speeds it up. The increase in Moon speed increases its orbital energy. That enlarges the Moon’s orbit and moves the Moon farther away.

We will never say goodbye to the Moon, though, because her departure is so slow that it exceeds the expected age of the Universe.

Further Surfing:

Space.com: Torn away, the Moon’s violent birth

The Royal Observatory Greenwich: The Moon

Big bang picture taking

Q: Sometime in the future, will it be possible to get a picture from space before the big bang occurred? If it is not, please explain why. How old is the oldest space picture we have today? Theoretically, how old a picture can we get? (Bambing, Quebec, Canada)

Full sky map of the oldest light in the Universe (click credit for a history of the Universe). [NASA/WMAP Science Team]

A: According to Einstein’s general theory of relativity, no, we will not be able to get a picture before the big bang.

Einstein believed that time and space began with the big bang, actually the tiniest shading afterwards. (10^-43 seconds later — the number of zeros in that decimal fraction would take over a line of text to display.)

This time bit (called Planck time) is due to the uncertainty principle of quantum mechanics. We can’t measure time any more accurately than that and therefore can’t speculate meaningfully about smaller times.

Events earlier than the big bang are beyond present theory. We don’t know if any exist or if we can image them.

The oldest picture we have today snapshots the Universe when it was 380,000 years old. The cosmos then was less than one thousandth the size it is now and hot — 5000 degrees Fahrenheit (3000 degrees Celsius). Our oldest image captured early light that first escaped when particles cooled enough to form atoms, thereby creating holes in space. Before that, the Universe was a fog — too dense for light to shine out.

Over 13 billion years later, the light reached us, cooling en route to about 3 degrees Kelvin above absolute zero (-455 degrees F). That dim cold glow (called the "microwave background radiation") is our snapshot.

Theoretically, the oldest picture we can take will image the first light free to zip through the Universe. That happened about 300,000 years after the big bang — when light photons separated from expanding matter. We have almost captured that radiation. Perhaps we have.

Further Surfing:

WonderQuest: The big bang theory

NASA: New image of infant universe revealed

PBS.org: Big bang time line

NASA/WMAP: Tests of the big bang, microwave background radiation

(Answered April 23, 2004)