You can think of the event horizon as the mouth of the black hole. Once something passes the event horizon, it is gone for good. Once inside the event horizon, all "events" points in space-time stop, and nothing even light can escape. The radius of the event horizon is called the Schwarzschild radius , named after astronomer Karl Schwarzschild, whose work led to the theory of black holes.
The concept of an object from which light could not escape e. Using Newton's Theory of Gravity , Laplace calculated that if an object were compressed into a small enough radius, then the escape velocity of that object would be faster than the speed of light. The Schwarzschild black hole is the simplest black hole, in which the core does not rotate.
This type of black hole only has a singularity and an event horizon. The Kerr black hole, which is probably the most common form in nature, rotates because the star from which it was formed was rotating. When the rotating star collapses, the core continues to rotate, and this carried over to the black hole conservation of angular momentum. The Kerr black hole has the following parts:. If an object passes into the ergosphere it can still be ejected from the black hole by gaining energy from the hole's rotation.
However, if an object crosses the event horizon , it will be sucked into the black hole and never escape. What happens inside the black hole is unknown; even our current theories of physics do not apply in the vicinity of a singularity. Even though we cannot see a black hole, it does have three properties that can or could be measured:.
If a black hole has a companion another star or disk of material , it is possible to measure the radius of rotation or speed of orbit of the material around the unseen black hole. The mass of the black hole can be calculated using Kepler's Modified Third Law of Planetary Motion or rotational motion.
Although we cannot see black holes, we can detect or guess the presence of one by measuring its effects on objects around it. The following effects may be used:. Many black holes have objects around them, and by looking at the behavior of the objects you can detect the presence of a black hole.
You then use measurements of the movement of objects around a suspected black hole to calculate the black hole's mass. What you look for is a star or a disk of gas that is behaving as though there were a large mass nearby.
For example, if a visible star or disk of gas has a "wobbling" motion or spinning AND there is not a visible reason for this motion AND the invisible reason has an effect that appears to be caused by an object with a mass greater than three solar masses too big to be a neutron star , then it is possible that a black hole is causing the motion. You then estimate the mass of the black hole by looking at the effect it has on the visible object. For example, in the core of galaxy NGC , there is a brown, spiral-shaped disk that is rotating.
The disk is about the size of our solar system, but weighs 1. Such a huge mass for a disk might indicate that a black hole is present within the disk. Einstein's General Theory of Relativity predicted that gravity could bend space. This was later confirmed during a solar eclipse when a star's position was measured before, during and after the eclipse. The star's position shifted because the light from the star was bent by the sun's gravity. Therefore, an object with immense gravity like a galaxy or black hole between the Earth and a distant object could bend the light from the distant object into a focus, much like a lens can.
This effect can be seen in the image below. When the Hubble Space Telescope looked at the object, it saw two images of the object close together, which indicated a gravitational lens effect. The intervening object was unseen. Black holes are also messy eaters, which often betrays their locations. As they sip on surrounding stars, their massive gravitational and magnetic forces superheat the infalling gas and dust, causing it to emit radiation. Some of this glowing matter envelops the black hole in a whirling region called an accretion disk.
Even the matter that starts falling into a black hole isn't necessarily there to stay. Black holes can sometimes eject infalling stardust in mighty radiation-laden burps. All rights reserved. Perseus Black Hole A view of the central region of the Perseus galaxy cluster, one of the most massive objects in the universe, shows the effects that a relatively small but supermassive black hole can have millions of miles beyond its core.
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So, should you then find yourself at the event horizon — the point at which light and matter can only pass inward, as proposed by the German astronomer Karl Schwarzschild — there is no escape. According to Massey, tidal forces would reduce your body into strands of atoms or 'spaghettification', as it is also known and the object would eventually end up crushed at the singularity.
The idea that you could pop out somewhere — perhaps at the other side — seems utterly fantastical. Or is it? Over the years scientists have looked into the possibility that black holes could be wormholes to other galaxies. They may even be, as some have suggested, a path to another universe. Such an idea has been floating around for some time: Einstein teamed up with Nathan Rosen to theorise bridges that connect two different points in space-time in But it gained some fresh ground in the s when physicist Kip Thorne — one of the world's leading experts on the astrophysical implications of Einstein's general theory of relativity — raised a discussion about whether objects could physically travel through them.
But it doesn't seem likely that wormholes exist. Indeed, Thorne, who lent his expert advice to the production team for the Hollywood movie Interstellar, wrote: "We see no objects in our universe that could become wormholes as they age," in his book "The Science of Interstellar" W.
Norton and Company, Thorne told Space. But, the problem is that we can't get up close to see for ourselves. Why, we can't even take photographs of anything that takes place inside a black hole — if light cannot escape their immense gravity , then nothing can be snapped by a camera. As it stands, theory suggests that anything which goes beyond the event horizon is simply added to the black hole and, what's more, because time distorts close to this boundary, this will appear to take place incredibly slowly, so answers won't be quickly forthcoming.
They'll just get redder and fainter as they approach the event horizon [as a result of gravitational red shift]. But the friend falls right in, to a place beyond 'forever. Certainly, if black holes do lead to another part of a galaxy or another universe, there would need to be something opposite to them on the other side. Could this be a white hole — a theory put forward by Russian cosmologist Igor Novikov in ? Novikov proposed that a black hole links to a white hole that exists in the past.
Unlike a black hole, a white hole will allow light and matter to leave, but light and matter will not be able to enter. Scientists have continued to explore the potential connection between black and white holes. Haggard claimed that "there is a classic metric satisfying the Einstein equations outside a finite space-time region where matter collapses into a black hole and then emerges from a while hole.
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