Main pemadam zaman kecil

on Thursday, August 14, 2014

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What Does A Star Sound Like?

on Thursday, August 29, 2013

Bang! Nasa/CXC/M. Weiss

Observing a star up close (putting aside for a moment how you’d get there or withstand its heat) is probably like sitting beside an enormous silent fire. Sounds—which are simply pressure variations in a medium such as air or water—can’t propagate in the vacuum of space, so the roiling surface of a star would make an impression on the eyes, but not the ears.

A supernova would sound like 10 octillion two-megaton nuclear bombs exploding.A supernova, however, just might be the most brutal concert in the universe. When a star explodes, the massive detonation expels stellar material far into space, and that matter could theoretically provide a medium through which sound vibrations might travel. Assuming you survived the blast—the initial shock wave would travel up to 20,000 miles per second and carry 1044 joules of energy—it would sound like “10 octillion two-megaton thermonuclear devices detonated simultaneously,” says Charles Liu, an astrophysicist at the City University of New York College of Staten Island. “When those guts hit your eardrums, you’ll hear it. That is, as long as your eardrums stay attached.”

This article originally appeared in the October 2009 issue of Popular Science magazine.

Could Robot Aliens Exist?

Artwork for the book "The War of the Worlds" Henrique Alvim Corréa via Wikimedia Commons

The existence of a race of sentient alien robots might be not just possible, but inevitable. In fact, we might be living in a "postbiological universe" right now, in which intelligent extraterrestrials somewhere have exchanged organic brains for artificial ones.

The driving factor is a pragmatic desire to improve mental capacity. Alien beings may have already reached a point in their evolution where, having exhausted the potential of their biological brains, they have taken the next logical step and opted for robotic brains equipped with artificial intelligence.

This brain swap may not be as far off for humans as one might think. In only a few decades, the computer revolution here on Earth has produced supercomputers capable of performing more than a quadrillion calculations per second. (According to research by Hans Moravec, an artificial-intelligence expert at Carnegie Mellon University, that rate trumps the human brain’s estimated top speed of 100 trillion calculations per second.) Some scientists speculate that in a few decades, an event called the technological singularity will occur, and machines armed with computer brains will become sentient and surpass human intelligence. Civilizations equipped with technology light-years ahead of our own could have already experienced the singularity thousands, or even millions, of years ago.

Steven Dick: Former NASA chief historian and an astrophysicist specializing in astrobiology and the postbiological universe NASA

How likely is it that such a robotic race exists? Given the limitations of biology as we know it, the force of cultural evolution, and the imperative to improve intelligence, I’d say the chances are greater than 50/50. That said, if postbiological beings do exist, they might not be interested in us at all. The gulf between their minds and ours might be so great that communication is impossible, or they might consider meatheads like us too primitive to warrant their attention.

This article originally appeared in the September 2008 issue of Popular Science magazine.

FYI: What's The Point Of Sex?

It Would Be So Much Easier to Clone Ourselves, Right? Bdelloid Rotifers, all-female animals that live in ponds, have reproduced without sex for millions of years. Diego Fontaneto via Wikipedia

This may seem obvious. But in evolutionary terms, the benefits of sexual reproduction are not immediately clear. Male rhinoceros beetles grow huge, unwieldy horns half the length of their body that they use to fight for females. Ribbon-tailed birds of paradise produce outlandish plumage to attract a mate. Darwin was bothered by such traits, since his theory of evolution couldn’t completely explain them (“The sight of a feather in a peacock’s tail, whenever I gaze at it, makes me feel sick!” he wrote to a friend).

Moreover, sex allows an unrelated, possibly inferior partner to insert half a genome into the next generation. So why is sex nearly universal across animals, plants and fungi? Shouldn’t natural selection favor animals that forgo draining displays and genetic roulette and simply clone themselves?

Yes and no. Many animals do clone themselves; certain sea anemones can bud identical twins from the sides of their bodies. Aphids, bees and ants can reproduce asexually. Virgin births sometimes occur among hammerhead sharks, turkeys, boa constrictors and komodo dragons. But nearly all animals engage in sex at some point in their lives. Biologists say that the benefits of sex come from the genetic rearrangements that occur during meiosis, the special cell division that produces eggs and sperm. During meiosis, combinations of the parents’ genes are broken up and reconfigured into novel arrangements in the resulting sperm and egg cells, creating new gene combinations that might be advantageous.

Shouldn’t natural selection favor animals that forgo draining displays and genetic roulette and simply clone themselves?One animal, however, has done just fine without any sex at all. Bdelloid rotifers can be found in most freshwater ponds, measure a few tenths of a millimeter long, contain only about 1,000 cells, and have been chaste for roughly 80 million years. The nearly 400 described species of bdelloids prove that the group is respectably diverse, yet no one has ever seen a male. Bdelloids lay unfertilized eggs that grow to be fully fertile daughters. What’s the secret?

Harvard University biology professor Matthew Meselson and his lab have spent the past several years investigating bdelloids’ molecular genetics. By exposing bdelloids to extremely high levels of ionizing radiation (a treatment that causes hundreds of physical breaks in DNA strands), one of Meselson’s former graduate students, Eugene Gladyshev, showed that bdelloids can completely rebuild their genomes—an unprecedented feat among animals.

Recently, Meselson and Gladyshev made an even more amazing discovery: Bdelloids have foreign DNA from bacteria and fungi in their chromosomes, which is a great way to maintain genetic diversity. As for the rest of us, we’re stuck with sex.

This article originally appeared in the May 2011 issue of Popular Science magazine.


Orang dewasa promosikan Diaper di Jepun (1 Gambar)

on Friday, July 12, 2013

Orang dewasa promosikan Diaper di Jepun (1 Gambar)
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