UNDERSTANDING THE UNIVERSE
WITH PROF YASH PAL

The fact that hair and nails are made of dead cells does mean that these cells cannot exchange information. That is why you do not feel any pain when you cut your hair or trim your nails. That is the reason that horse’s hoofs allow them to run on stony rough surfaces without being hurt or the claws of some animals, or beaks of birds and the horns of deer provide such useful appendages. The hair of a beautiful girl makes her more beautiful and the hair on the body of sheep keeps it insulated from the environments and, when shorn, allows us to make woolen clothes. Invention of the possibility of hair and nails was an intriguing and useful outcome of evolution. But these dead parts must also arise from locations that are alive.

In the case of nails, say on our fingers and toes, the insensitive part we see, and sometimes apply nail polish to, is called the nail plate. This plate is coupled to the skin at the bottom. This is called the nail bed. There is a matrix, a hidden part of the nail where the growth takes place. Nails do not grow at the end but from this matrix under the skin of the finger. This is called the cuticle. If you put a mark on your nail with indelible ink, you would see this mark travelling towards the end as time passes. The nail plate, even though made of dead cells, is continuously renewed at the rate of about a millimeter a week.

Hair is somewhat similar. The growth is at the follicles under the skin. The dead cells keep being added and the hair grows long. Both, the hair and the nails are made of dense, compacted proteins.

Let me try to explain the drama of formation of the ozone layer and its role. Ozone is a molecule of oxygen with three atoms. These molecules are heavier than those of ordinary oxygen or nitrogen. Therefore one would expect that such a gas would be found closer to the ground and not at very high altitude! The reason for this anomalous phenomenon is that ozone is formed in the rare upper atmosphere and it is easily destroyed in collisions with other molecules and absorption of ultraviolet from the sun. It does not have enough time to diffuse down to the ground level. But how is it formed and why does it provide the essential shield against that part of the ultraviolet that would otherwise reach down to where we live? The answer to both these questions has to be understood together.

In order to make a molecule of ozone we need a free atom of oxygen that can come close to a molecule of ordinary oxygen and stick with it. Ultraviolet rays whose energy is high enough to break oxygen molecules into atoms produce these free atoms of oxygen. In the process such ultraviolet rays are themselves screened out - there is enough oxygen and other material in the atmosphere. Part of the ultraviolet that does not have sufficient energy to split oxygen atoms does not get shielded in this way. It can just scatter without harming the atoms on the way without being absorbed. This is precisely what would happen if there were no ozone. In ozone the oxygen atoms are not as strongly bound as in ordinary oxygen with three atoms to a molecule. Lower energy ultraviolet can peel off one of these atoms and in the process itself die. Thus we have a drama in which the ozone is created with the help of the high-energy ultraviolet and then becomes instrumental in shielding us from the low energy part of the ultraviolet spectrum of the sun! It is estimated that a molecule of ozone has a life of about three minutes. It is born high up in the atmosphere and in a short while dies while protecting us - a real martyr.

Astronomers have found new evidence for one of the strangest properties of the universe. A mysterious substance, dubbed dark energy, appears to be ripping the cosmos apart, causing the universe to expand at an ever-faster rate. The wrenching findings come from a correlation between two kinds of sky maps—one that denotes the positions of large numbers of galaxies and another, a snapshot of the cosmic microwave background, which is the remnant radiation from the Big Bang.

By comparing the maps, astronomers have found the imprint of dark energy, which pushes objects apart and thus counters gravity’s familiar tug. Previous support for dark energy has been based on the brightness of distant stellar explosions known as supernovas. With only one line of evidence, however, some researchers weren’t convinced.

"Since the implications of dark energy are so profound for physics, having multiple, independent lines of evidence for its existence is absolutely essential," says Joshua A. Frieman of the Fermi National Accelerator Laboratory in Batavia, Ill., a coauthor of one of four dark-energy studies recently posted online. Each study uses data from the Wilkinson Microwave Anisotropy Probe (WMAP), a satellite that is generating detailed maps of the cosmic microwave background .

This remnant radiation is riddled with hot and cold spots, most of which reflect the lumpiness of the infant universe, from which galaxies grew. But some of the energy in the hot spots may have been acquired later, as light travelled for billions of years to reach Earth.

During their long journey, photons from the microwave background encounter huge concentrations of matter, such as superclusters of galaxies. As the photons fall into these clouds of matter, they gain energy, like a marble that speeds up as it rolls downhill. As the photons climb out of these areas, they lose energy.

If the universe were flat — so that parallel lines never meet — and contained no dark energy, photons traversing matter-filled regions would gain exactly as much energy as they lose. But in a flat universe containing dark energy, there would be no such cancellation, says Frieman.

For more than a decade, Cynthia Kenyon has watched microscopic worms of the species Caenorhabditis elegans live far longer than they should. She has seen mutant strains of this worm, which is normally dead and gone after a mere two or three weeks, last well into their second month. It’s as if a person lived to be 200 years old. Kenyon’s long-lived worms are a result of mutations in individual genes. That’s a radical notion to many scientists who have long thought of aging as an uncontrollable process of deterioration that isn’t regulated by single genes.

"There have to be genes that affect life span," counters Kenyon of the University of California, San Francisco. Noting the dramatic differences in life span among various animals — a mouse may last for 2 years while a bat can live for half a century — Kenyon has become convinced that longevity has evolved in animals many times. She argues that her long-lived nematodes can reveal some of the fundamental molecular biology that controls longevity in more-complex organisms, even people.

In 1993, Kenyon and her colleagues jump-started the field of aging genetics when they reported on a mutant strain of C. elegans that lives twice as long as normal. It showed the largest proportional lifespan extension of any animal known at the time.