Satellites

The launching of Pioneer V into its solar orbit and of Tiros, the weather observer, and Transit I-B, the beacon, brought to 13 the number of man-made vehicles still intruding on space. Ten of these are travelling around the Earth, three around the Sun. Tiros, following the most perfectly circular orbit yet achieved, and carrying television cameras and automatic positioning equipment is the first satellite adapted to systematic observation of the Earth. In Its first two days aloft it returned 1200 pictures of the Earth's cloud-cover as seen from an altitude of 450 miles. It can make and transmit 120 such pictures on each 99-minute revolution.

Still beeping after two years in space is the grapefruit-sized Vanguard I. During nearly 8000 circuits of the Earth completed by its second anniversary, it has wandered about a mile off its predicted course. This discrepancy has been traced to the pressure of sunlight.

The latest analysis of the Vanguard I orbits, shows that the earlier conclusion that the Earth is pear-shaped is not proven—a symmetrical Earth could also give rise to the observed motions.

Oldest Rocks

The proven age of the Earth is finally approaching the known age of meteorites, 4.5 billion years old. It's believed on astronomical grounds that meteorites were formed at the same time as the Earth. Samples of basement rock recovered in South Africa have been found by the uranium-lead dating method to be at least four billion years old. The oldest rock previously known was a specimen of mica, estimated to 3.4 billion years old, found near Murmansk in the U.S.S.R. in 1959.

The revised chronology pushes back several of the major subdivision of past scales. The beginning of the Cambrian period (the era of the earliest marine fossils) is now set at 600 million years ago, instead of 560 million, and the end of the Triassic (the age of the first Dinosaurs) has been fixed at 190 million years ago.

The new times were arrived at with the aid of improved procedures for measuring the radioactive decay of U238, Rb87 and K40.

The techniques now available can date suitable specimens of almost any period in the Earth's history with an error of a few per cent. The remaining difficulties are with samples between 50.000 and 1 million years old.

New Man-Ape

The anthropologist R. A. Dart, of South Africa, recently combed through 40,000 tons of rubble at Makapansgat to discover 35,500 fragments of Australopithecus Promethus.

—M.H.