Audible Snowflakes and Other Discoveries
More science highlights discovered in 2000
Snow Falling on Water
A team of researchers have discovered that when a snowflake falls onto a body of
water, it deposits a tiny amount of air just beneath the surface. Before the bubble
reaches the surface and pops, it sends out a piercing sound. This sound, ranging from
50 to 200 kilohertz, is too high-pitched to be heard by human ears, which generally
pick up nothing higher than 20 kilohertz. However, to porpoises and other aquatic
animals that can hear the higher frequencies, the falling snowflakes create an
enormous racket just below the surface. Falling snow can add 30 decibels to
underwater noise levels. Beyond its deafening impact on water animals, snowflake
noise can create “electronic clutter” for people who use sensitive sonar devices.
Our Tiniest Ancestors
In March 2000, a team of researchers led by Northern Illinois University
paleontologist Dan Gebo announced their discovery of the fossil bones of
45-million-year-old monkeylike primates, the smallest primates ever found. The new
species, named Eosimias (“dawn monkey”), was discovered in a limestone quarry in
eastern China.
Its foot bones are the size of grains of rice, and it weighs less than a dozen paper
clips. Yet the miniature “Dawn Monkey” could represent an evolutionary link
between lower primates and higher primates, a group that includes apes and humans.
The structure of its tiny ankle bones suggests that it could walk flat-footed, using all
four legs, like advanced primates. Unlike advanced primates, however, it probably
“didn't have a lot of time to be social,” guesses one scientist. That's because the little
animal had to spend most of its time eating to feed its high-speed metabolism–when
it wasn't trying to avoid being eaten by bigger creatures. The discovery of this
specimen in Asia suggests that our earliest ancestors did not live in Africa alone, as
previously thought.
The researchers said that the minute mammals were tree dwellers that relied on a
steady diet of insects, fruit, and nectar to fuel their high metabolisms. Unlike
contemporary higher primates, the tiny primates likely were nocturnal and solitary
creatures.
Solar Heartbeat Discovered
Astronomers from the National Science Foundation's National Solar Observatory
have discovered a “solar heartbeat” in the motion of the layers of gas circulating
beneath the Sun's surface. Their research shows that some parallel layers speed up
and slow down rhythmically about every 16 months. This internal cyclic action may
explain the formation of sunspots and solar flares.
The Sun is not a solid object–it is made up of layers of gas. Unlike Earth, all points
on the solar surface do not rotate at the same rate. Its equatorial region rotates once
every 27 days, while the regions at the Sun's poles rotate at a slower rate of once
every 35 days. The “differential” rotation extends through the Sun's turbulent
convective layer, located about 130,494 miles (210,000 kilometers) below the
surface, nearly one-third of the distance to the solar core. At the edge of the
convective layer, the rotation period varies, completing a cycle about every 15—16
days. Astronomers think that the patterns of these internal movements are connected
to the cycles of eruptions seen on the surface.
New Killer Crater
Geoscientists at the Geological Survey of Western Australia and the Australian
National University discovered the world's fourth-largest asteroid impact crater in
western Australia. Buried beneath the red-sand country east of Shark Bay, the huge
crater centered on Woodleigh Station is estimated to be 75 miles (120 kilometers) in
diameter. It is the result of a massive 3.1-mile- (5-kilometer-) wide asteroid that
smashed into Earth some 200—360 million years ago. The impact would probably
have resulted in an extinction event similar to the Chicxulub impact in the Gulf of
Mexico, which has been linked to the extinction of the dinosaurs at the end of the
Cretaceous period, 65 million years ago.
The Woodleigh crater's estimated age probably coincides with one of three
extinction events known in the fossil record: the Late Devonian extinction (364
million years), the end of the Permian period (247 million years), or the end of the
Triassic period (214 million years).
Awesome Ape-Man Find
In April 2000, scientists at the University of Witwatersrand, South Africa, announced
the discovery of two early hominid fossils excavated in the Sterkfontein caves, 4
miles (7 kilometers) northwest of Johannesburg. The fossils comprise the most
complete female skull ever found of her species, together with the lower jawbone of
a male. The 1.5- to 2-million-year-old pair were christened Orpheus and Eurydice
(after the ancient Greek mythological lovers). They were identified as Paranthropus
(“beside man”) robustus, a type of Australopithecine (“ape man”) known for its huge
teeth. They were not direct descendants of modern humans but were a line of
hominids that became extinct about one million years ago.
For the first time, scientists now know what a male and female Paranthropus
looked like and what the differences were between male and female skulls. The top
of the male's skull features a ridge, called a sagittal crest, to which the muscles of the
lower jaw were anchored. The female, apart from being smaller than the male, has
no such crest–a distinction echoed among male and female gorillas today.
Orpheus and Eurydice were largely vegetarians but may have included some meat in
their diet from scavenged kills. They may even have used tools.
Monster Asteroid
Astronomers using the world's most powerful radio telescope at Arecibo, Puerto
Rico, have captured radar images of a giant, dog-bone—shaped asteroid located in
the main asteroid belt between Mars and Jupiter. They are the first images ever made
of a main-belt asteroid. The unusual space rock, named 216 Kleopatra, measures
about 135 miles (217 kilometers) long and about 58 miles (94 kilometers) wide,
roughly the size of the state of New Jersey.
Although the massive asteroid was discovered in 1880, its peculiar dog-bone or
distorted dumbbell-like shape was unknown until now. Its strange appearance could
have been produced by an incredibly violent collision between two asteroids that did
not completely shatter and disperse all the fragments. Or it may once have comprised
two separate lobes in orbit around each other with empty space between them, and
subsequent impacts filled in the space with debris.
Radar observations of Kleopatra seem to indicate that its surface is porous and
loosely consolidated. Its interior appears to be composed of mostly solid metal
fragments, possibly an nickel-iron alloy.
First Out-of-Africa Ancestors
A team of Georgian, German, French, and U.S. researchers reported finding a nearly
complete fossil cranium and another skullcap representing the earliest known human
ancestors from Eurasia, at a site in Dmanisi, Georgia. The 1.7-million-year-old fossils
are the first discovered outside of Africa that show clear signs of African ancestry.
Their age and skeletal characteristics link them to the early African species Homo
ergaster, a species that some scientists believe is the African version of Homo
erectus. The new evidence suggests that they may have been the first hominid
species to journey out of Africa.
Stone tools of the less sophisticated “pebble-chopper type,” predating the Acheulean
or hand-ax tradition, were found in the sediment with the skulls, contradicting the
theory that early humans didn't leave Africa until after they had invented technically
advanced tools. Despite the ready availability of raw material, all of the Dmanisi
artifacts found at the site are of a pre-Acheulean type that appeared in Africa as
early as 2.4 million years ago. Stone Age tools featuring hand-axes, cleavers,
scrapers, and sharp stone flakes are called Acheulean (from St. Acheul in France).
Information Please® Database, © 2007 Pearson Education, Inc. All rights reserved.
|
