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02
Mai 14

Dark Matter Could Send Asteroids Crashing into Earth:

New Theory

(Charles Q. Choi – 28.04.2014 – space.com)

 

 

Dark matter could sling lethal meteors at Earth, potentially causing mass extinctions like the cataclysm that ended the Age of Dinosaurs, Harvard scientists say.

 

Physicists think the mysterious, invisible substance called dark matter makes up five-sixths of all matter in the universe. It was first detected by the strength of its gravitational pull, which apparently helps keep the Milky Way and other galaxies from spinning apart, given the speeds at which they whirl.

 

Scientists have recently suggested that a thin, dense disk of dark matter about 35 light-years thick lies along the central plane of the Milky Way, cutting through the galaxy's disk of stars.

The sun travels in an up-and-down, wavy motion through this plane while orbiting the center of the galaxy.

 

Researchers suggest this disk of clouds and clumps made of dark matter might disturb the orbits of comets in the outer solar system, hurling them inward. This could lead to catastrophic asteroid impacts on Earth, of the kind that likely ended the Age of Dinosaurs, said theoretical physicists Lisa Randall and Matthew Reece at Harvard University.

 

Past research has suggested meteor bombardment of Earth rises and falls in a cycle about 35 million years long. In the past, scientists have proposed a cosmic trigger for this cycle, such as a potential companion star for the sun with the dramatic name "Nemesis."

 

Instead of blaming a "death star" for these catastrophes, Randall and Reese point out that this cycle of doom closely matches the rate at which the sun passes through the central plane of the Milky Way. This hints that the galaxy's "dark disk" may be the actual culprit. (continua)

 

(space.com)

publicado por Produções Anormais - Albufeira às 00:11

24
Abr 12

Matéria-Negra – Será que existe mesmo?

 

.... 

Dark matter is mysteriously missing from the sun's neighborhood, according to a new study that could provide ammunition for skeptics who argue that the invisible substance is just an illusion.

.... 

Even though dark matter particles can't be detected with current instruments, astronomers think the substance must make up about a quarter of the universe, based on the gravitational effect it has on visible matter such as galaxies and galaxy clusters.

....

Current models of how galaxies form and rotate suggest that the Milky Way is embedded in a cloud, or halo, of dark matter. Astronomers can't tell precisely what shape this halo takes, but they expected to find significant amounts of dark matter in the region around the sun.

....

Stars in the sky may appear static, but they're constantly in motion as they get minutely pushed and pulled by the gravitational effects of neighboring objects, including other stars, gas clouds, or clumps of dark matter.

.... 

"These observations point to the fact that in this volume [of space], there is no dark matter".

....

One reason scientists think dark matter exists is because stars in the outer parts of galaxies have been seen to orbit the center as fast as stars in the inner parts. The laws of gravity dictate that such fast-moving stars near the edges of galaxies should fly off into space. Instead, the theory goes, the added mass of dark matter holds them in place.

.... 

 

(nationalgeographic.com)

publicado por Produções Anormais - Albufeira às 15:58

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