If I was you, I'd wanna be me too
Tuesday, 20 September 2016
Saturday, 17 September 2016
Thursday, 15 September 2016
Singularity
A gravitational singularity or space-time singularity is a location where the quantities that are used to measure the gravitational field of a celestial body become infinite in a way that does not depend on the coordinate system. These quantities are the scalar invariant curvatures of space-time, which includes a measure of the density of matter. The laws of normal space-time could not exist within a singularity.[1][2]
For the purposes of proving the Penrose–Hawking singularity theorems, a space-time with a singularity is defined to be one that contains geodesics that cannot be extended in a smooth manner.[3] The end of such a geodesic is considered to be the singularity. This is a different definition, useful for proving theorems.
[Gravitational singularity - Wikipedia, the free encyclopedia] is good,have a look at it! https://en.m.wikipedia.org/wiki/Gravitational_singularity
The time machine
A wormhole or Einstein–Rosen bridge is a hypothetical topological feature that would fundamentally be a shortcut connecting two separate points in spacetime. A wormhole may connect extremely long distances such as a billion light years or more, short distances such as a few feet, different universes, and different points in time. A wormhole is much like a tunnel with two ends, each at separate points in spacetime.
Stephen Hawking makes it clear: There is no God
Stephen Hawking makes it clear: There is no God
The physicist explains that science now offers more convincing explanations for existence. He is therefore an atheist.
Hawking said: "Before we understand science, it is natural to believe that God created the universe. But now science offers a more convincing explanation."
I'm not sure whether there was a specific moment in which science overtook the deistic explanation of existence. However, El Mundo pressed him on the suggestion in "A Brief History of Time" that a unifying theory of science would help mankind "know the mind of God."
Hawking now explained: "What I meant by 'we would know the mind of God' is, we would know everything that God would know, if there were a God. Which there isn't. I'm an atheist."
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He added: "Religion believes in miracles, but these aren't compatible with science."
Perhaps. But some look at, for example, the human eye and wonder how that exciting ball of jelly could have come about scientifically.
Hawking's been tending toward such an absolute pronouncement for a while. In a speech last year, he offered an explanation of how the world came to being without God. He mused: "What was God doing before the divine creation? Was he preparing hell for people who asked such questions?"
First glimpse of a blackhole
First glimpse of a black hole being born from a star’s remains
We’ve received a birth announcement from 20 million light years away, in the form of our first ever glimpse of what seems to be the birth of a black hole.
When massive stars run out of fuel, they die in a huge explosion, shooting out high-speed jets of matter and radiation. What’s left behind collapses into a black hole, which is so dense and has such strong gravity that not even light can escape it.
Or so the theory goes, anyway. Now, a team led by Christopher Kochanek at Ohio State University in Columbus have glimpsed something very special in data from the Hubble Space Telescope, from when it was watching the red supergiant star N6946-BH1, which is about 20 million light years from Earth.
Fading star
This star, first observed in 2004, was once about 25 times the mass of our sun. Kochanek and his colleagues found that for some months in 2009, the star briefly flared a million times brighter than our sun, then steadily faded away. New Hubble images show that it has disappeared in visible wavelengths, but a fainter source in the same spot is detectable in the infrared, as a warm afterglow.
These observations mesh with what theory predicts should happen when a star that size crumples into a black hole. First, the star spews out so many neutrinos that it loses mass. With less mass, the star lacks enough gravity to hold on to a cloud of hydrogen ions loosely bound around it. As this cloud of ions floats away, it cools off, allowing the detached electrons to reattach to the hydrogen. This causes a year-long bright flare – when it fades, only the black hole remains.
There are two other potential explanations for the star’s disappearing act: it could have merged with another star, or be hidden by dust. But they don’t fit the data: a merger would shine more brightly than the original star for much longer than a few months, and dust wouldn’t hide it for so long.
“It’s an exciting result and long anticipated,” says Stan Woosley at Lick Observatory in California.
“This may be the first direct clue to how the collapse of a star can lead to the formation of a black hole,” says Avi Loeb at Harvard University.
A dark life cycle
The find needs further confirmation, but that may not be far off. Material falling into the black hole would emit X-rays in a particular spectrum, which could be spotted by the Chandra X-ray Observatory. Kochanek says his group will be getting new data from Chandra in the next two months or so.
If Chandra sees nothing, that doesn’t mean it’s not a black hole. In any case, the team will continue to look with Hubble – the longer the star is not there, the more likely that it’s a black hole. “Patience proves it no matter what,” says Kochanek.
This data will help describe the beginning of the life cycle of a black hole, and will inform simulations of how black holes form and what makes a massive star form a neutron star rather than a black hole.
Despite calling himself a “nasty pessimist”, Kochanek thinks it’s quite likely this is indeed the formation of a black hole. “I’m not quite at ‘I’d bet my life on it’ yet,” he says, “but I’m willing to go for your life.”
http://arxiv.org/abs/1609.01283
https://www.newscientist.com/article/mg22930664-600-ligo-could-catch-dark-matter-made-of-black-holes/
https://www.newscientist.com/article/2105588-first-glimpse-of-a-black-hole-being-born-from-a-stars-remains/?utm_campaign=Echobox&utm_medium=Social&utm_source=Twitter#lin
Gravitational lensing
In general relativity, the presence of matter (energy density) can curve spacetime, and the path of a light ray will be deflected as a result. This process is called gravitational lensing and in many cases can be described in analogy to the deflection of light by (e.g. glass) lenses in optics. Many useful results for cosmology have come out of using this property of matter and light.
For many of the cases of interest one does not need to fully solve the general relativistic equations of motion for the coupled spacetime and matter, because the bending of spacetime by matter is small. (Quantitatively the matter bending space is moving slowly relative to c, the speed of light and the "gravitational potential" Phi induced by the matter obeys |Phi|/c2 << 1 .)
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