【Native Speaker每日综合训练—45系列】【45-10】科技 Black Hole

Going

内容：古月小破烂 编辑：Going

Stay tuned to our latest post! Follow us here ---> http://weibo.com/u/3476904471

星际穿越里面神奇的黑洞~~~~enjoy~~
越障文章特别特别特别的长~希望大家能耐心读完~~~

Part I: Speaker

Triple Black Hole System Found in Distant Galaxy
A galaxy four billion light-years from us was has three supermassive black holes at its center, with two in a tight formation. Clara Moskowitz reports
By Clara Moskowitz | July 1, 2014

Inside most galaxies a supermassive black hole lurks. But one galaxy about 4 billion light-years from us was recently discovered to have not one, not even two, but three gigantic black holes at its center.

Such triple systems appear to be extremely rare—only four are known. The newfound system includes two black holes orbiting each other very closely, about 450 light-years apart, with a third black hole a bit farther out. The central pair zoom around each other at a fast clip, about 300 times the speed of sound on Earth. The hole trinity also represents the tightest trio of black holes known to date. It’s described in the journal Nature.

As these objects continue to orbit at the center of their galaxy, gravity will eventually pull them closer and closer together. Ultimately, they may even merge. Researchers hope this triple-black-hole system may be a good place to look for space-time ripples called gravitational waves. As their orbits shrink, the black holes should radiate away some of their orbital energy as the sought-after gravitational waves, predicted by Einstein a century ago.

Source: Scientific America
http://www.scientificamerican.com/podcast/episode/triple-black-hole-system-found-in-distant-galaxy1/

[Rephrase 1, 1:24]

Going

Part II: Speed

Are We Living in a Black Hole?
Our universe may reside within a vast, black hole.
by Michael Finkel  |  18 Feb 2014

A surprising spiral shape in the nearby active galaxy NGC 1433, shown above, indicates material flowing in to fuel a black hole. A jet of material flowing away from the black hole has also been observed.

[Time 2]
Let's rewind the clock. Before humans existed, before Earth formed, before the sun ignited, before galaxies arose, before light could even shine, there was the Big Bang. This happened 13.8 billion years ago.

But what about before that? Many physicists say there is no before that. Time began ticking, they insist, at the instant of the Big Bang, and pondering anything earlier isn't in the realm of science. We'll never understand what pre-Big Bang reality was like, or what it was formed of, or why it exploded to create our universe. Such notions are beyond human understanding.

But a few unconventional scientists disagree. These physicists theorize that, a moment before the Big Bang, all the mass and energy of the nascent universe was compacted into an incredibly dense—yet finite—speck. Let's call it the seed of a new universe.

This seed is thought to have been almost unimaginably tiny, possibly trillions of times smaller than any particle humans have been able to observe. And yet it's a particle that can spark the production of every other particle, not to mention every galaxy, solar system, planet, and person.

If you really want to call something the God particle, this seed seems an ideal fit.

So how is such a seed created? One idea, bandied about for several years—notably by Nikodem Poplawski of the University of New Haven—is that the seed of our universe was forged in the ultimate kiln, likely the most extreme environment in all of nature: inside a black hole.
[254 words]

[Time 3]
Multiverses Multiply

It's important to know, before we go further, that over the last couple of decades, many theoretical physicists have come to believe that our universe is not the only one. Instead, we may be part of the multiverse, an immense array of separate universes, each its own shining orb in the true night sky.

How, or even if, one universe is linked to another is a source of much debate, all of it highly speculative and, as of now, completely unprovable. But one compelling idea is that the seed of a universe is similar to the seed of a plant: It's a chunk of essential material, tightly compressed, hidden inside a protective shell.

This precisely describes what is created inside a black hole. Black holes are the corpses of giant stars. When such a star runs out of fuel, its core collapses inward. Gravity pulls everything into an increasingly fierce grip. Temperatures reach 100 billion degrees. Atoms are smashed. Electrons are shredded. Those pieces are further crumpled.

The star, by this point, has turned into a black hole, which means that its gravitational pull is so severe that not even a beam of light can escape. The boundary between the interior and exterior of a black hole is called the event horizon. Enormous black holes, some of them millions of times more massive than the sun, have been discovered at the center of nearly every galaxy, including our own Milky Way.
[243 words]

[Time 4]
Bottomless Questions

If you use Einstein's theories to determine what occurs at the bottom of a black hole, you'll calculate a spot that is infinitely dense and infinitely small: a hypothetical concept called a singularity. But infinities aren't typically found in nature. The disconnect lies with Einstein's theories, which provide wonderful calculations for most of the cosmos, but tend to break down in the face of enormous forces, such as those inside a black hole—or present at the birth of our universe.

Physicists like Dr. Poplawski say that the matter inside a black hole does reach a point where it can be crushed no further. This "seed" might be incredibly tiny, with the weight of a billion suns, but unlike a singularity, it is real.

The compacting process halts, according to Dr. Poplawski, because black holes spin. They spin extremely rapidly, possibly close to the speed of light. And this spin endows the compacted seed with a huge amount of torsion. It's not just small and heavy; it's also twisted and compressed, like one of those jokey spring-loaded snakes in a can.

Which can suddenly unspring, with a bang. Make that a Big Bang—or what Dr. Poplawski prefers to call "the big bounce."

It's possible, in other words, that a black hole is a conduit—a "one-way door," says Dr. Poplawski—between two universes. This means that if you tumble into the black hole at the center of the Milky Way, it's conceivable that you (or at least the shredded particles that were once you) will end up in another universe. This other universe isn't inside ours, adds Dr. Poplawski; the hole is merely the link, like a shared root that connects two aspen trees.

And what about all of us, here in our own universe? We might be the product of another, older universe. Call it our mother universe. The seed this mother universe forged inside a black hole may have had its big bounce 13.8 billion years ago, and even though our universe has been rapidly expanding ever since, we could still be hidden behind a black hole's event horizon.
[354 words]

Source: National Geography
http://news.nationalgeographic.com/news/2014/02/140218-black-hole-blast-explains-big-bang/

'Eye of Sauron' Opens Galactic Vistas to Astronomers
Gigantic black holes provide a new cosmic yardstick for charting far-off stars.
by Andrew Fazekas  |  26 Nov 2014

This composite image shows the central region of the spiral galaxy NGC 4151, nicknamed the Eye of Sauron.

[Time 5]
Monster black holes lurking within the core of galaxies offer a new way to measure how far many objects in the universe are from Earth, astronomers report on Wednesday—and with much better accuracy than ever before.

The cosmic-yardstick breakthrough came courtesy of the galaxy NGC 4151, dubbed the Eye of Sauron because it resembles the baleful bad guy in The Lord of the Rings.

Previous estimates of the distance to the sinister-looking galaxy had ranged wildly, putting it 13 million to 95 million light-years from Earth. But using a technique that's similar to land surveying, astronomers believe they've pinned down the distance to 62 million light-years.

A new study published this week in the journal Nature details the innovative technique, which, like the film's plot, revolves around a ring. In this case the ring is galactic debris that surrounds the gigantic black hole at the heart of NGC 4151.

A Gift

Using the twin 32-foot (10-meter) telescopes at the W. M. Keck Observatory on the summit of Mauna Kea, Hawaii, and interferometry, the study's team of astronomers, led by Sebastian Hönig of the University of Southampton, achieved the same resolution as a single mirror about 280 feet (85 meters) across, the physical distance separating the two observatories. That's a hundred times the resolution of the Hubble Space Telescope.

This gave the astronomers supersharp views of the center of NGC 4151 and the infrared glow of the ring of hot dust around its black hole, a common feature of such "active" galaxies. Then, using the distance from the ring to the black hole as the base of a triangle, the researchers could determine the distance from Earth to NGC 4151.

"In fact, this method, based on simple geometrical principles, gives the most precise distances for remote galaxies," says Hönig in a press statement. "Such distances are key in pinning down the cosmological parameters that characterize our universe or in accurately measuring black hole masses.
[324 words]

[Time 6]
"Indeed, NGC 4151 is a key to calibrating various techniques of estimating black hole masses," he says. "Our new distance implies that these masses may have been systematically underestimated by 40 percent."

The new technique will allow astronomers to measure the distance to the roughly 10 percent of galaxies that are active, says astronomer Martin Elvis of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, in a commentary accompanying the study. That means they'll be able measure distances to objects much farther away than the supernovas that showed our universe is expanding at an accelerating rate, a discovery that garnered the Nobel Prize in 2006.

"Usually in science you fight so hard to get something to fit or work properly," says study co-author Darach Watson, of the University of Copenhagen. "But every so often—very rarely—something magical happens. It's like a gift, and everything just falls into place. That is what happened here."

See for Yourself

You too can hunt down this galactic Eye of Sauron. You'll need a medium to large backyard telescope to get a good view, but a scope with a mirror or lens as small as four inches should give you a glimpse, even in suburban locations.

Shining feebly at magnitude 11, this spiral galaxy lies in a rich field of galaxies in the constellation Canes Venatici, which is visible this time of the year from across the entire Northern Hemisphere in the predawn hours. The galaxy lies halfway up the northeast sky just below the Big Dipper and just west of a 7th magnitude star.

Through the eyepiece under high magnification, NGC 4151 looks humble, a faint but distinct oval-shaped patch of light that's less than a third the width of the full moon. Though just 9 arc minutes in our sky, the galaxy is actually some 124,000 light-years across and has a monster black hole at its center-one that's 37.6 million times the mass of our sun.
[324 words]

Source: National Geography
http://news.nationalgeographic.com/news/2014/11/141126-starstruck-eye-sauron-black-hole-astronomy-science/

Going

Part III: Obstacle

Black Holes
Albert Einstein thought that a black hole—a collapsed star. So dense that even light could not escape its thrall—was too preposterous a notion to be real. Einstein was wrong.
by Michael Finkel  |  June 2013

[Paraphrase 7]
Our star, the sun, will die a quiet death. The sun’s of only average mass, starwise, and after burning through the last of its hydrogen fuel in about five billion years, its outer layers will drift away, and the core will eventually compact to become what’s known as a white dwarf, an Earth-size ember of the cosmos.

For a star ten times as big as the sun, death is far more dramatic. The outer layers are blasted into space in a supernova explosion that, for a couple of weeks, is one of the brightest objects in the universe. The core, meanwhile, is squeezed by gravity into a neutron star, a spinning ball bearing a dozen miles in diameter. A sugar-cube-size fragment of a neutron star would weigh a billion tons on Earth; a neutron star’s gravitational pull is so severe that if you were to drop a marshmallow on it, the impact would generate as much energy as an atom bomb.

But this is nothing compared with the death throes of a star some 20 times the mass of the sun. Detonate a Hiroshima-like bomb every millisecond for the entire life of the universe, and you would still fall short of the energy released in the final moments of a giant-star collapse. The star’s core plunges inward. Temperatures reach 100 billion degrees. The crushing force of gravity is unstoppable. Hunks of iron bigger than Mount Everest are compacted almost instantly into grains of sand. Atoms are shattered into electrons, protons, neutrons. Those minute pieces are pulped into quarks and leptons and gluons. And so on, tinier and tinier, denser and denser, until...

Until no one knows. When trying to explain such a momentous phenomenon, the two major theories governing the workings of the universe—general relativity and quantum mechanics—both go haywire, like dials on an airplane wildly rotating during a tailspin.

The star has become a black hole.

What makes a black hole the darkest chasm in the universe is the velocity needed to escape its gravitational pull. To overcome Earth’s clutches, you must accelerate to about seven miles a second. This is swift—a half dozen times faster than a bullet—but human-built rockets have been achieving escape velocity since 1959. The universal speed limit is 186,282 miles a second, the speed of light. But even that isn’t enough to defeat the pull of a black hole. Therefore whatever’s inside a black hole, even a beam of light, cannot get out. And due to some very odd effects of extreme gravity, it’s impossible to peer in. A black hole is a place exiled from the rest of the universe. The dividing line between the inside and outside of a black hole is called the event horizon. Anything crossing the horizon—a star, a planet, a person—is lost forever.

Albert Einstein, one of the most imaginative thinkers in the history of physics, never believed black holes were real. His formulas allowed for their existence, but nature, he felt, would not permit such objects. Most unnatural to him was the idea that gravity could overwhelm the supposedly mightier forces—electromagnetic, nuclear—and essentially cause the core of an enormous star to vanish from the universe, a cosmic-scale David Copperfield act.

Einstein was hardly alone. In the first half of the 20th century most physicists dismissed the idea that an object could become dense enough to asphyxiate light. To lend it any more credence than one would give the tooth fairy was to risk career suicide.

Still, scientists had wondered about the possibility as far back as the 18th century. English philosopher John Michell mentioned the idea in a report to the Royal Society of London in 1783. French mathematician Pierre-Simon Laplace predicted their existence in a book published in 1796. No one called these superdense curiosities black holes—they were referred to as frozen stars, dark stars, collapsed stars, or Schwarzschild singularities, after the German astronomer who solved many theoretical equations about them. The name “black hole” was first used in 1967, during a talk by American physicist John Wheeler at Columbia University in New York City.

Around the same time there was a radical shift in black hole thinking, due primarily to the invention of new ways of peering into space. Since the dawn of humanity, we’d been restricted to the visible spectrum of light. But in the 1960s x-ray and radio wave telescopes began to be widely used. These allowed astronomers to collect light in wavelengths that cut through the interstellar dust and let us see, as in a hospital x-ray, the interior bones of galaxies.

What scientists found, startlingly, was that at the center of most galaxies—and there are more than 100 billion galaxies in the universe—is a teeming bulge of stars and gas and dust. At the very hub of this chaotic bulge, in virtually every galaxy looked at, including our own Milky Way, is an object so heavy and so compact, with such ferocious gravitational pull, that no matter how you measure it, there is only one possible explanation: It’s a black hole.

These holes are immense. The one at the center of the Milky Way is 4.3 million times as heavy as the sun. A neighboring galaxy, Andromeda, houses one with as much mass as 100 million suns. Other galaxies are thought to contain billion-sun black holes, and some even ten-billion-sun monsters. The holes didn’t begin life this large. They gained weight, as we all do, with each meal. Black hole experts also believe that small holes roam the galactic suburbs, common as backyard deer.

In the course of a single generation of physicists, black holes morphed from near jokes—the reductio ad absurdum of mathematical tinkering—to widely accepted facts. Black holes, it turns out, are utterly common. There are likely trillions of them in the universe.

No one has ever seen a black hole, and no one ever will. There isn’t anything to see. It’s just a blank spot in space—a whole lot of nothing, as physicists like to say. The presence of a hole is deduced by the effect it has on its surroundings. It’s like looking out a window and seeing every treetop bending in one direction. You’d almost certainly be right in assuming that a strong yet invisible wind was blowing.

When you ask the experts how certain we are that black holes are real, the steady answer is 99.9 percent; if there aren’t black holes in the center of most galaxies, there must be something even crazier. But all doubt may be removed in a matter of months. Astronomers are planning to spy on one while it eats.

The black hole at the center of the Milky Way, 26,000 light-years away, is named Sagittarius A*. Sgr A*—that’s the standard abbreviation; its surname is pronounced A-star—is currently a tranquil black hole, a picky eater. Other galaxies contain star-shredding, planet-devouring Godzillas called quasars.

But Sgr A* is preparing to dine. It’s pulling a gas cloud named G2 toward it at about 1,800 miles a second. Within as little as a year G2 will approach the hole’s event horizon. At this point radio telescopes around the world will focus on Sgr A*, and it’s hoped that by synchronizing them to form a planet-size observatory called the Event Horizon Telescope, we will produce an image of a black hole in action. It’s not the hole itself we will see but likely what’s known as the accretion disk, a ring of debris outlining the edge of the hole, the equivalent of crumbs on a tablecloth after a hearty meal. This should be enough to dispel most doubts that black holes exist.

More than merely exist. They may help determine the fabric of the universe. Matter hurtling toward a black hole produces a lot of frictional heat. Slide down a fire pole; your hands get hot. Same with stuff sliding toward a black hole. Black holes also spin—they’re basically deep whirlpools in space—and the combination of friction and spin results in a significant amount of the matter falling toward a black hole, sometimes more than 90 percent, not passing through the event horizon but rather being flung off, like sparks from a sharpening wheel.

This heated matter is channeled into jet streams that hurtle through space, away from the hole at phenomenal velocities, usually just a tick below the speed of light. The jets can extend for millions of light-years, drilling straight through a galaxy. Black holes, in other words, churn up old stars in the galactic center and pipe scalding gases generated in this process to the galaxy’s outer parts. The gas cools, coalesces, and eventually forms new stars, refreshing the galaxy like a fountain of youth.
[1462 words]

[the rest]
It’s important to clarify a couple of things about black holes. First is the idea, popularized in science fiction, that black holes are trying to suck us all in. A black hole has no more vacuuming power than a regular star; it just possesses extraordinary grip for its size. If our sun suddenly were to become a black hole—not going to happen, but let’s pretend—it would retain the same mass, yet its diameter would shrink from 865,000 miles to less than four miles. Earth would be dark and cold, but our orbit around the sun wouldn’t change. This black hole sun would exert the same gravitational tug on our planet as the full-size one. Likewise, if the Earth were to become a black hole, it would retain its current weight of more than six sextillion tons (that’s a six followed by 21 zeros) but be shrunk in size to smaller than an eyeball. The moon, though, wouldn’t move.

So black holes don’t suck. Easy. The next topic, time, is way more of a mind bender. Time and black holes have a very strange relationship. Actually time itself—forgetting about black holes for a moment—is an unusual concept. You probably know the phrase “time is relative.” What this means is that time doesn’t move at the same speed for everybody. Time, as Einstein discovered, is affected by gravity. If you place extremely accurate clocks on every floor of a skyscraper, they will all tick at different rates. The clocks on the lower floors—closer to the center of the Earth, where gravity is stronger—will tick a little slower than the ones on the top floors. You never notice this because the variances are fantastically small, a spare billionth of a second here and there. Clocks on global positioning satellites have to be set to tick slightly slower than those on Earth’s surface. If they didn’t, GPS wouldn’t be accurate.

Black holes, with their incredible gravitational pull, are basically time machines. Get on a rocket, travel to Sgr A*. Ease extremely close to the event horizon, but don’t cross it. For every minute you spend there, a thousand years will pass on Earth. It’s hard to believe, but that’s what happens. Gravity trumps time.

And if you do cross the event horizon, then what? A person watching from the outside will not see you fall in. You will appear frozen at the hole’s edge. Frozen for an infinite amount of time.

Though technically not infinite. Nothing lasts forever, not even black holes. Stephen Hawking, the British physicist, proved that black holes leak—the seepage is called Hawking radiation—and given enough time, will evaporate entirely. But we’re talking trillions upon trillions upon many more trillions of years. Long enough so that in the far future, black holes may be the only objects remaining in our universe.

While an outside observer would never see you slip into a black hole, what would happen to you? Sgr A* is so large that its event horizon is about eight million miles from its center. There’s some debate in the physics community about the moment you cross over. It’s possible there exists what’s called a fire wall, and that upon reaching the event horizon, you promptly burn up.

General relativity theory predicts, however, that something else happens when you cross the event horizon: Nothing. You just pass through, unaware that you’re now lost to the rest of the universe. You’re fine. Your watch on your wrist ticks along as usual. It’s often said that black holes are infinitely deep, but this is not true. There is a bottom. You won’t live to see it. Gravity, as you fall, will grow stronger. The pull on your feet, if you’re falling feet first, will be so much greater than the tug on your head that you’ll be stretched until you’re ripped apart. Physicists call this being “spaghettified.”

But pieces of you will reach the bottom. At the center of a black hole is a conundrum called a singularity. To understand a singularity would be one of the greatest scientific breakthroughs in history. You’d first need to invent a new theory—one that went beyond Einstein’s general relativity, which determines the motion of stars and galaxies. And you’d have to surpass quantum mechanics, which predicts what happens to microscopic particles. Both theories are fine approximations of reality, but in a place of extremes, like the interior of a black hole, neither applies.

Singularities are imagined to be extremely tiny. Beyond tiny: Enlarge a singularity a trillion  times, and the world’s most powerful microscope wouldn’t come close to seeing it. But something is there, at least in a mathematical sense. Something not just small but also unimaginably heavy. Don’t bother wondering what. The vast majority of physicists say, yes, black holes exist, but they are the ultimate Fort Knox. They’re impenetrable. We will never know what’s inside a singularity.

But a couple of unorthodox thinkers beg to differ. In recent years it’s become increasingly accepted among theoretical physicists that our universe is not all there is. We live, rather, in what’s known as the multiverse—a vast collection of universes, each a separate bubble in the Swiss cheese of reality. This is all highly speculative, but it’s possible that to give birth to a new universe you first need to take a bunch of matter from an existing universe, crunch it down, and seal it off.

Sound familiar? We do know, after all, what became of at least one singularity. Our universe began, 13.8 billion years ago, in a tremendous big bang. The moment before, everything was packed into an infinitesimally small, massively dense speck—a singularity. Perhaps the multiverse works something like an oak tree. Once in a while an acorn is dropped, falls into the ideal soil, and abruptly sprouts. So too with a singularity, the seed of a new universe. And like a sapling oak, we’ll never send a thank-you note to our mother. For the message to escape our universe, it would have to move faster than the speed of light. Again, sound familiar?

The evidence for what could reside in a black hole is compelling. Look to your left, look to your right. Pinch yourself. A black hole might have originated in another universe. But we may be living in it.
[1060 words]

Source: National Geography
http://ngm.nationalgeographic.com/2014/03/black-holes/finkel-text

jokerking

沙发？？
spd : 1.16  1.19  1.56  1.48  1.38

kimwang53

Great articles. Thank you 古月小破烂 and Going: )

speed
1.57
1.47
2.43
2.07
2.30

obstacle
12.25
-star will die.
-bigger star die dramatic.
-what a death of a star which is 20 times bigger than sun looks like.
-velocity->nlack hole darkest chasm
nothing can go out of BH. Whenver a thing oes in, it disappears forever.
-Eintein does.'t believe BH is real.
John Michell: first mention the idea.
BH-> 1st breought in NY.
-BH immensc
-No one (will) saw BH. It's a whole lot of nothing.
-heat->jet stream.BH, gas cools...make galaxy.

yang8291890

speed: 1:49,  1:42,  2:38,  2:45,  2:23
pin down 使受约束
bandy 传播
constellation 星座

aviva9393

Speaker 1'43
Speed: 2'04 1'27 2'07 1'27 2'0
Obstacle: 14'

Phoebedyf2

Time2: 1'23'' (184wpm)
We don't know what happened before the BIG BANG. Some scientists supposed that the universe was compacted into a dense spack, called the seed of a new universe.

Time3: 1'37'' (150wpm)
The black hole is like the seed in plant, with essence hidden inside a hard protection.
How the black hole forms: A star died and its core collapsed, and then everything will be pulled in because of the gaint gravity.

Time4: 2'35'' (137wpm)
The black hole may be the door linked to another new universe.
Our universe may created by our mother universe.

Time5: 2'00'' (162wpm)
Using a new innovative technique and basic knowledge of geometry, scentists can determine the distance from earth to NGC.

Time6: 1'56'' (167wpm)
By detecting the NGC, many more galaxies will be allowed to measure, and it provides the techniques to search further about our universe.
We can also observe the galaxy by eyes.

Obstacle: 9'57'' (147wpm)
难以概括。。但是基本上看懂了。。用风吹过树来形容黑洞这个比喻简直太形象！

neverland1021

谢谢古月和going~
1'36[254 words]
reset the time: before the universe is born: before 13.8billion years ago
what is before the universe? what is the seed of the universe?=>A seed of black hole

1'18[243 words]
multiverse: there is not only one universe

2'00[354 words]
E theory: indefinite point=>singularity
A Russian scientist: this point is real and it is the link(root) between two universe
speculation: human is the product of another(mother) universe

1'57[324 words]
the shape of a galaxy is like the eye of S in the Lord ring
to calculate the distance between the ring of this spiral galaxy can help scientists to calculate the mass of the black hole

1'52[324 words]
the mass of black hole is underestimated
how to observe the galactic eye of Sauron by ourselves.

9'14[1462 words]
describe the death of some stars =>ten time bigger than sun: supernova, 20 times bigger than sun=>
black hole
E 推导(deduce)the existence of black hole, but his nature refuses to admit its existence
the unpopular and unacceptable black hole theory =>utterly common theory now
we cannot observe the existence of black hole directly=>maybe something is even crazier than black hole
the experiments designed to observe black hole indirectly

sumy217

Speed
1. 1'42''
Some scientists insist that before the big bang there was a seed which formed the universe subsequently.

2.1'54''
The black hole is a huge planet which collapse in the center and the huge gravity pull everything inside and smash it totally.

3.3'43''
The infinite tiny and compressed seed in the center of black hole spinned with the balck hole and than big bang happened.
The black hole in the center of our milky way is a bondary of another universe.
4.
The black hole gives scientist a method to determine distance of objects in universe accurately.

5.1'50''
NGC 4151 help scientists to measured objects more far away than before and estimate the amount of massive material in our cosmos.