.jpg)
The Largest Black Holes in the Universe
A black hole is a region of space from which nothing, not even light, can escape The theory of general relativity predicts that a sufficiently compact mass will deform spacetime to form a black hole. Around a black hole there is a mathematically defined surface called an event horizon that marks the point of no return. It is called "black" because it absorbs all the light that hits the horizon, reflecting nothing, just like a perfect black body in thermodynamics. Quantum mechanics predicts that black holes emit radiation like a black body with a finite temperature. This temperature is inversely proportional to the mass of the black hole, making it difficult to observe this radiation for black holes of stellar mass or greater.
Objects whose gravity field is too strong for light to escape were first considered in the 18th century by John Michell and Pierre-Simon Laplace. The first modern solution of general relativity containing a black hole was found by Karl Schwarzschild in 1916, although its interpretation as a region of space from which nothing can escape was not fully appreciated for another four decades. Long considered a mathematical curiosity, it was during the 1960s that theoretical work showed black holes were a generic prediction of general relativity. The discovery of neutron stars sparked interest in gravitationally collapsed compact objects as a possible astrophysical reality.
Black holes of stellar mass are expected to form when heavy stars collapse in a supernova at the end of their life cycle. After a black hole has formed it can continue to grow by absorbing mass from its surroundings. By absorbing other stars and merging with other black holes, supermassive black holes of millions of solar masses may be formed.
Despite its invisible interior, the presence of a black hole can be inferred through its interaction with other matter. Astronomers have identified numerous stellar black hole candidates inbinary systems, by studying their interaction with their companion stars. There is growing consensus that supermassive black holes exist in the centers of most galaxies. In particular, there is strong evidence of a black hole of more than 4 million solar masses at the center of our Milky Way.
The Mamas & The Papas - California Dreamin
All the leaves are brown
And the sky is gray
I've been for a walk
On a winter's day
I'd be safe and warm
If I was in L.A.
California dreamin'
On such a winter's day
Stopped into a church
I passed along the way
Oh, I got down on my knees
And I pretend to pray
You know the preacher likes the cold
He knows I'm gonna stay
California dreamin'
On such a winter's day
All the leaves are brown
And the sky is gray
I've been for a walk
On a winter's day
If I didnt tell her
I could leave today
California dreamin'
On such a winter's day
(California dreamin')
On such a winter's day
(California dreamin')
On such a winter's day
Scott McKenzie - San Francisco＇1967
.jpg)
Be sure to wear some flowers in your hair
If you're going to San Francisco
You're gonna meet some gentle people there
For those who come to San Francisco
Summertime will be a love-in there
In the streets of San Francisco
Gentle people with flowers in their hair
All across the nation such a strange vibration
People in motion
There's a whole generation with a new explanation
People in motion people in motion
For those who come to San Francisco
Be sure to wear some flowers in your hair
If you come to San Francisco
Summertime will be a love-in there
If you come to San Francisco
Summertime will be a love-in there
Subscribe to:
Posts (Atom)
.jpg)
