The comet that killed the dinosaurs opened the evolutionary door for one of Earth's most diverse groups of creatures: mammals. David Archibald, Ph.D., a professor of evolutionary biology at San Diego State, has made this transition from dinosaurs to mammals his expertise.
Archibald studies early mammalian fossils and is trying to constrain the origins of the phylum to which humans belong. His research has taken him around the world in search of the remains of terrestrial creatures.
Science & Technology
For the first time, scientists of the BaBar experiment at the Department of Energy's Stanford Linear Accelerator Center (SLAC) have observed the transition of one type of particle, the neutral D-meson, into its antimatter particle. Mesons, of which there are about 140 types, are made up of fundamental particles called quarks, which can be produced when particles collide at high energy.
The new observation will be used as a test of the Standard Model, the current theory that best describes all the universe's luminous matter and its associated forces.
The new observation will be used as a test of the Standard Model, the current theory that best describes all the universe's luminous matter and its associated forces.
A scholar looking into the factual basis of a popular but widely criticized documentary that claims to have located the tomb of Jesus said Tuesday that a crucial piece of evidence filmmakers used to support their claim is a mistake.
Stephen Pfann, a textual scholar and paleographer at the University of the Holy Land in Jerusalem, said he has released a paper claiming the makers of "The Lost Tomb of Jesus" were mistaken when they identified an ancient ossuary from the cave as belonging to the New Testament's Mary Magdalene.
The film's director, Simcha Jacobovici, responded that other researchers agreed with the documentary's conclusions.
Stephen Pfann, a textual scholar and paleographer at the University of the Holy Land in Jerusalem, said he has released a paper claiming the makers of "The Lost Tomb of Jesus" were mistaken when they identified an ancient ossuary from the cave as belonging to the New Testament's Mary Magdalene.
The film's director, Simcha Jacobovici, responded that other researchers agreed with the documentary's conclusions.
LOS ANGELES - Scientists believe heat from radioactive decay inside a tiny, icy Saturn moon shortly after it formed billions of years ago may explain why geysers are erupting from the surface today. The Cassini spacecraft last year beamed back dazzling images of Yellowstone-like geysers spewing from a warm section on Enceladus, raising the possibility that the moon, which has an overall surface temperature of about minus-330 degrees, may have an internal environment suitable for primitive life.
A single, specific memory has been wiped from the brains of rats, leaving other recollections intact.
A simple formula can predict how people would want to be treated in dire medical situations as accurately as their loved ones can, say researchers.
The finding suggests that computers may one day help doctors and those acting as surrogate decision-makers to better estimate the wishes of people in a coma.
By signing what is known as an "advance directive", people can specify what types of medical care they would want if they lost the ability to make decisions. Many people, however, do not complete such a directive in advance of these critical situations and their relatives or others must then decide on their behalf.
The finding suggests that computers may one day help doctors and those acting as surrogate decision-makers to better estimate the wishes of people in a coma.
By signing what is known as an "advance directive", people can specify what types of medical care they would want if they lost the ability to make decisions. Many people, however, do not complete such a directive in advance of these critical situations and their relatives or others must then decide on their behalf.
By casting a wide net, astronomers have captured an image of more than a thousand supermassive black holes. These results give astronomers a snapshot of a crucial period when these monster black holes are growing, and provide insight into the environments in which they occur.
The new black hole panorama was made with data from NASA's Chandra X-ray Observatory, the Spitzer Space Telescope and ground-based optical telescopes. The black holes in the image are hundreds of millions to several billion times more massive than the sun and lie in the centers of galaxies.
The new black hole panorama was made with data from NASA's Chandra X-ray Observatory, the Spitzer Space Telescope and ground-based optical telescopes. The black holes in the image are hundreds of millions to several billion times more massive than the sun and lie in the centers of galaxies.
Modern humans were living in northern Africa far earlier than previously thought, according to scientists. A new analysis of a 160,000-year-old fossilised jawbone from Morocco shows that the homo sapiens in the area had started having long childhoods, one of the hallmarks of humans living today.
It is known that the species homo sapiens emerged in Africa 200,000 years ago, but the oldest fossils that resemble modern humans come from sites in Europe dated to around 20,000 to 30,000 years ago.
The latest find shows that the key time in the development of a complex human society came much earlier than previously thought. The longer people had to learn and develop their brains as children, the more sophisticated their society could become. The new study pushes the date that modern humans emerged back by more than 100,000 years.
It is known that the species homo sapiens emerged in Africa 200,000 years ago, but the oldest fossils that resemble modern humans come from sites in Europe dated to around 20,000 to 30,000 years ago.
The latest find shows that the key time in the development of a complex human society came much earlier than previously thought. The longer people had to learn and develop their brains as children, the more sophisticated their society could become. The new study pushes the date that modern humans emerged back by more than 100,000 years.
In 1926, Russian physicist Yakov Frenkel proposed a theory that put a limit on the amount of stress a perfect crystal can withstand before its structural planes begin to slip over one another. Now, however, physicists from Norway have made a theoretical model showing that before Frenkel's limit is ever reached, crystals will deform due to a process called "thermal runaway" -- whereby strain and heat amplify rapidly. This could shed light on the mechanisms underlying deep earthquakes, and could help engineers to determine material tolerances more accurately.
Frenkel's theory applies to perfect crystals, and has long been known to set the stress limit too high for most real materials. This is because real materials often contain defects that can move through the structure and make it easier for planes to slip. But this is not always true: some materials such as rocks in the Earth's interior and metallic glasses have structures that act to prevent defects from moving, and so can demonstrate unusually high shear strengths.
Frenkel's theory applies to perfect crystals, and has long been known to set the stress limit too high for most real materials. This is because real materials often contain defects that can move through the structure and make it easier for planes to slip. But this is not always true: some materials such as rocks in the Earth's interior and metallic glasses have structures that act to prevent defects from moving, and so can demonstrate unusually high shear strengths.
An unusual type of arms race involving nuclear bombs and supermassive spacecraft has been heating up this week in Washington, D.C.
Each team of players hopes to be the one to design the U.S. government's weapon of choice for deflecting comets and asteroids that could be on a collision course with Earth.
A NASA task force today presented Congress with a report that includes recommendations for the best technologies for avoiding an impact with a so-called near-Earth object (NEO).
The debate has been raging among experts about which solution will be the safest, cheapest, and most reliable.
Ed Lu, a NASA astronaut and physicist, has been developing one of the leading contenders: a "gravitational tractor."
Each team of players hopes to be the one to design the U.S. government's weapon of choice for deflecting comets and asteroids that could be on a collision course with Earth.
A NASA task force today presented Congress with a report that includes recommendations for the best technologies for avoiding an impact with a so-called near-Earth object (NEO).
The debate has been raging among experts about which solution will be the safest, cheapest, and most reliable.
Ed Lu, a NASA astronaut and physicist, has been developing one of the leading contenders: a "gravitational tractor."
