Posted on by Brian Koberlein

What Would It Be Like To Fall Into A Black Hole?

This artist’s impression shows the surroundings of the supermassive black hole at the heart of the active galaxy NGC 3783 in the southern constellation of Centaurus (The Centaur). Credit: ESO/M. Kornmesser

Let’s say you happened to fall into the nearest black hole? What would you experience and see? And what would the rest of the Universe see as this was happening?

Let’s say you decided to ignore some of my previous advice. You’ve just purchased yourself a space dragon from the Market on the Centauri Ringworld, strapped on your favorite chainmail codpiece and sonic sword and now you’re going ride head first into the nearest black hole.

We know it won’t take you to another world or galaxy, but what would you experience and see on your way to your inevitable demise? And what would the rest of the Universe see as this was happening, and would they point and say “eewwwwww”?

If you were falling toward a black hole, most of the time you would simply feel weightless, just as if you were playing Bowie songs and floating in a most peculiar way in the International Space Station. The gravity of a black hole is just like the gravity of any other large mass, as long as you don’t get too close. But, as we’ve agreed, you’re ignoring my advice and flying dragon first into this physics nightmare. As you get closer, the gravitational forces on various parts of your and your dragon’s body would be different. Technically this is always true, but you wouldn’t notice it… at least at first.

Suppose you were falling feet first toward a black hole. As you got closer, your feet would feel a stronger force than your head, for example. These differences in forces are called tidal forces. Because of the tidal forces it would feel as if you are being stretched head to toe, while your sides would feel like they are being pushed inward. Eventually the tidal forces would become so strong that they would rip you apart. This effect of tidal stretching is sometimes boringly referred to as spaghettification.

I’ve made up some other names for it, such as My Own Private String Cheese Incident, “the soft-serve effect” and “AAAHHHHH AHHHH MY LEGS MY LEGS!!!”.

So, let’s summarize. You wouldn’t survive falling toward a black hole because you wouldn’t listen. Why won’t you ever listen?

A friend watching you fall toward a black hole would never see you reach the black hole. As you fall towards it, gravity would cause any light coming from you to be redshifted. So as you approached the black hole you would appear more and more reddish, and your image would appear dimmer and dimmer. Your friend would see you redden and dim as you approach, but never quite reach, the event horizon of the black hole. If they could still see you past this point, there would be additional red from the inside of you clouding up the view.

Artist's conception of the event horizon of a black hole. Credit: Victor de Schwanberg/Science Photo Library
Artist’s conception of the event horizon of a black hole. Credit: Victor de Schwanberg/Science Photo Library

Hypothetically, if you could survive crossing the event horizon of a black hole, what
would you see then? Contrary to popular belief, you would not see the entire future of the universe flash before you.

What you would see is the darkness of the black hole fill your view and as you approached the event horizon you would see stars and galaxies on the edge of your view being gravitationally lensed by the black hole. The sky would simply appear more and more black until you reach the event horizon.

Many people think that it is at the event horizon where you would be ripped apart, and at the event horizon all sorts of strange things occur. Unfortunately, this goes along with those who suspect black holes are actually some sort of portal. For a solar mass black hole, the tidal forces near the event horizon can be quite large, but for a supermassive black hole they aren’t very large at all.

In fact, the larger the black hole, the weaker the tidal forces near its event horizon. So if you happened to be near a supermassive black hole, you could cross the event horizon without really noticing. Would you still be totally screwed? YOU BETCHA!

What do you think? If you could drop anything into a black hole, what would it be? Tell us in the comments below.

Posted on by Bob King

Observing Alert: Distant Blazar 3C 454.3 in Outburst, Visible in Amateur Telescopes

The blazar 3C 454.3 photographed by the Sloan Digital Sky Survey. It's currently in bright outburst and nearly as bright as the star next to it. Both are about magnitude +13.6. Credit: SDSS

Have an 8-inch or larger telescope? Don’t mind staying up late? Excellent. Here’s a chance to stare deeper into the known fabric of the universe than perhaps you’ve ever done before. The violent blazer  3C  454.3 is throwing a fit again, undergoing its most intense outburst seen since 2010. Normally it sleeps away the months around 17th magnitude but every few years, it can brighten up to 5 magnitudes and show in amateur telescopes. While magnitude +13 doesn’t sound impressive at first blush, consider that 3C 454.3 lies 7 billion light years from Earth. When light left the quasar, the sun and planets wouldn’t have skin in the game for another  two billion years. 

If we could see the blazar 3C 354.3 up close it would look something like this. A bright accretion disk surrounds a black hole. Twin jets of radiation beam from the center. Credit: Cosmovision
If we could see the blazar 3C 354.3 up close it would look something like this. A bright accretion disk surrounds a black hole. Twin jets of radiation beam from the center. Credit: Cosmovision

Blazars form in the the cores of active galaxies where supermassive black holes reside. Matter falling into the black hole spreads into a spinning accretion disk before spiraling down the hole like water down a bathtub drain.

Superheated to millions of degrees by gravitational compression the disk glows brilliantly across the electromagnetic spectrum. Powerful spun-up magnetic fields focus twin beams of light and energetic particles called jets that blast into space perpendicular to the disk.

Blazars and quasars are thought to be one and the same, differing only by the angle at which we see them. Quasars – far more common – are actively- munching supermassive black holes seen from the side, while in blazars – far more rare – we stare directly or nearly so into the jet like looking into the beam of a flashlight.

An all-sky view in gamma ray light made with the Fermi gamma ray telescope shows bright gamma-ray emission in the plane of the Milky Way (center), bright pulsars and super-massive black holes including the active blazar 3C 454.3 at lower left. Credit: NASA/DOE/International LAT Team
An all-sky view in gamma ray light made with the Fermi Gamma-ray Space Telescope shows bright gamma-ray emission in the plane of the Milky Way (center), bright pulsars and super-massive black holes including the active blazar 3C 454.3 at lower left. Credit: NASA/DOE/International LAT Team

3C 454.3 is one of the top ten brightest gamma ray sources in the sky seen by the Fermi Gamma-ray Space Telescope. During its last major flare in 2005, the blazar blazed with the light of 550 billion suns. That’s more stars than the entire Milky Way galaxy! It’s still not known exactly what sets off these periodic outbursts but possible causes include radiation bursts from shocked particles within the jet or precession (twisting) of the jet bringing it close to our line of sight.

3c 454.3 is near the magnitude 2.5 magnitude star Alpha Pegasi just to the west of the Great Square. Use this chart to star hop from Alpha to IM Peg (mag. ~ 5.7). Once there, the detailed map below will guide you to the blazar. Stellarium
3c 454.3 is near the star Alpha Pegasi just to the west of the Great Square. Use this chart to star hop from Alpha to IM Peg (mag. ~ 5.7). Once there, the detailed map below will guide you to the blazar. Stellarium

The current outburst began in late May when the Italian Space Agency’s AGILE satellite detected an increase in gamma rays from the blazar. Now it’s bright visually at around magnitude +13.6 and fortunately not difficult to find, located in the constellation Pegasus near the bright star Alpha Pegasi (Markab) in the lower right corner of the Great Square asterism.

Using the wide view map, find your way to IM Peg via Markab and then make a copy of the detailed map below to use at the telescope to star hop to 3C 454.3. The blazar lies immediately south of a star of similar magnitude. If you see what looks like a ‘double star’ at the location, you’ve nailed it. Incredible isn’t it to look so far into space back to when the universe was just a teenager? Blows my mind every time.

Detailed map showing the location of the blazar 3C 454.3. I've created a small asterism with a group of brighter stars with their magnitudes marked. A scale showing 30 arc minutes (1/2 degree) is at right. Stars shown to about magnitude +15. Created with Chris Marriott's SkyMap software
Detailed map showing the location of the blazar 3C 454.3. I’ve drawn a small asterism using a group of brighter stars with their magnitudes marked. A scale showing 30 arc minutes (1/2 degree) is at right. Click to enlarge. Created with Chris Marriott’s SkyMap software

To further explore 3C 454.3 and blazars vs. quasars I encourage you to visit check out Stefan Karge’s excellent Frankfurt Quasar Monitoring site.  It’s packed with great information and maps for finding the best and brightest of this rarified group of observing targets. Karge suggests that flickering of the blazar may cause it to appear somewhat brighter or fainter than the current magnitude. You’re watching a violent event subject to rapid and erratic changes. For an in-depth study of 3C 454.3, check out the scientific paper that appeared in the 2010 Astrophysical Journal.


Learn more about quasars and blazers with a bit of great humor

Finally, I came across a wonderful video while doing research for this article I thought you’d enjoy as well.

Posted on by Fraser Cain

Where Is the Center of the Universe?

Where Is the Center of the Universe?

In a previous episode we hinted that every spot is at the center of the Universe. But why? It turns out, every way you look at it, you’re standing dead center at the middle of everything. And so is everyone else.

We ended a previous episode with how the center of the Universe is everywhere, and then quickly moved on to “Thanks for watching” without providing any details other than a wink and a nod.

Good news, here come your details. First, imagine the expanding Universe in your mind. You might be picturing an inflating ball pushing out in all directions. Perhaps you’re seeing some kind of giant expanding celestial pumpkin. Unfortunately, that idea is incorrect. But don’t feel bad, our thinking meat parts just aren’t built to do this sort of thing.

The region of space that we can see is the observable Universe. When we look in any direction, we’re seeing the light that left stars millions and even billions of years ago. When you get out to the 13.8 billion light year mile marker, you’re seeing the light that was emitted shortly after the Big Bang, when the Universe cooled down to the point that it became transparent. So the observable Universe is a sphere around you, it’s relative to your position.

My observable Universe is a sphere around me, relative to my position. So if I’m 10 meters away from you, I can see a little further into the Universe in that direction. If you look behind you, you’re seeing the observable Universe a little further in the that direction.

Imagine you’re standing in a dark room holding a candle. You can see out into a sphere around you. You’re at the center of your observable space. And if I’m in a different location, I’ll have a different observable sphere. This is why we say that everyone is at the center of their own personal observable Universe.

This has hints of pedantry and it’s a little unsatisfying, so let’s dig a little deeper. Where is the actual center of the Universe, regardless of who’s observing it? Our Universe might be finite or it might be infinite. Astronomers don’t actually know for sure. Their most precise calculations say that the observable Universe is 93 billion light years across.

Representation of the timeline of the universe over 13.7 billion years, and the expansion in the universe that followed. Credit: NASA/WMAP Science Team.
Representation of the timeline of the universe over 13.7 billion years, and the expansion in the universe that followed. Credit: NASA/WMAP Science Team.

Remember that light from the Big Bang that took 13.8 billion light years to get to you? Well the expansion of the Universe has pushed that region out to more than 46 billion light-years away. Look as far as you can to the right and as far as you can to the left. Those two spots are currently 93 billion light-years away from each other. So we can’t see how big the Universe really is. It’s got to be larger than 93 billion light-years. Everything outside that region we just can’t see… yet. It might be infinite.

If the Universe is infinite, then there’s an infinite amount of space in that direction and an infinite amount of space in that direction, and that direction. And we’re back where we started, literally. Once again, you’re at the center of the Universe. And so am I.

But what if the Universe is finite? That’s where it gets tricky. Imagine the observable Universe as a tiny sphere inside the much larger actual Universe. Maybe it’s 100 billion light years across, or maybe a trillion, or a quadrillion. Whatever the size, it’s not infinite. Now you would think there’s a center, right?

Well, astronomers think that the topology of a finite Universe indicates that if you travel in any one direction long enough, you’ll return to your starting point. In other words, if you could look far enough in any direction, you’d see the back of your head.

Imagine the universe as a sphere - Advanced Celestial Sphere (Wolfram Project). Credit: Jim Arlow
Imagine the universe as a sphere – Advanced Celestial Sphere (Wolfram Project). Credit: Jim Arlow

We did a whole episode on this, and you might want to check it out. And you’ll really want to check out Zogg the Aliens’ in-depth explanation. As an analogy, consider an ant on the surface of a sphere. Should the ant choose to walk in any direction, it’ll return to its starting point. Take that concept and scale it up one dimension. Can’t imagine it? No problem. Like I said, our brains aren’t equipped or experienced. And yet, that extra dimension seems to be the nature of the Universe. Regardless of what direction you travel, if it takes you the same amount of time to return to your starting point. Well… you’re at the center of the Universe?

See? No matter how you think about it and break it down, you’re at the center of everything. And so am I. What do you think? Is the Universe finite or infinite? Tell us why in the comments below.

Posted on by Fraser Cain

Can Light Orbit A Black Hole?

Can Light Orbit A Black Hole?

Since black holes are the most powerful gravitational spots in the entire Universe, can they distort light so much that it actually goes into orbit? And what would it look like if you could survive and follow light in this trip around a black hole?

I had this great question in from a viewer. Is it possible for light to orbit a black hole?

Consider this thought experiment, first explained by Newton. Imagine you had cannon that could shoot a cannonball far away. The ball would fly downrange and then crash into the dirt. If you shot the cannonball harder it would fly further before slamming into the ground. And if you could shoot the cannonball hard enough and ignore air resistance – it would travel all the way around the Earth. The cannonball would be in orbit. It’s falling towards the Earth, but the curvature of the Earth means that it’s constantly falling just over the horizon.

This works not only with cannonballs, astronauts and satellites, but with light too. This was one of the big discoveries that Einstein made about the nature of gravity. Gravity isn’t an attractive force between masses, it’s actually a distortion of spacetime. When light falls into the gravity well of a massive object, it bends to follow the curvature of spacetime.

Distant galaxies, the Sun, and even our own Earth will cause light to be deflected from its path by their distortion of spacetime. But it’s the incredible gravity of a black hole that can tie spacetime in knots. And yes, there is a region around a black hole where even photons are forced to travel in an orbit. In fact, this region is known as the “photon sphere”.

From far enough away, black holes act like any massive object. If you replaced the Sun with a black hole of the same mass, our Earth would continue to orbit in exactly the same way. But as you get closer and closer to the black hole, the orbiting object needs to go faster and faster as it whips around the massive object. The photon sphere is the final stable orbit you can have around a black hole. And only light, moving at, well, light speed, can actually exist at this altitude.

Artist impression of a black hole. Credit: ESO/L. Calçada
Artist impression of a black hole. Credit: ESO/L. Calçada

Imagine you could exist right at the photon sphere of a black hole. Which you can’t, so don’t try. You could point your flashlight in one direction, and see the light behind you, after it had fully orbited the black hole. You would also be bathed in the radiation of all the photons captured in this region. The visible light might be pretty, but the x-ray and gamma radiation would cook you like an oven.

Below the photon sphere you would see only darkness. Down there is the event horizon, light’s point of no return. And up above you’d see the Universe distorted by the massive gravity of the black hole. You’d see the entire sky in your view, even stars that would be normally obscured by the black hole, as they wrap around its gravity. It would be an awesome and deadly place to be, but it’d sure beat falling down below the event horizon.

If you could get down into the photon sphere, what kind of experiments would you want to do? Tell us in the comments below.

Posted on by Fraser Cain

Weekly Space Hangout – March 7, 2014: Cosmos Premiere & NASA Budget

Host: Fraser Cain
Astrojournalists: David Dickinson, Matthew Francis, Casey Dreier, Jason Major, Brian Koberlein, Alan Boyle

This week’s stories:

Alan Boyle (@b0yle, cosmiclog.com ):
Cosmos premiere!

David Andrew Dickinson (@astroguyz):
Watch the Close Pass of NEO 2014 DX110
Daylight Saving time: A Spring Forward or a Step Back?
A Natural Planetary Defense Against Solar Storms

Matthew Francis (@DrMRFrancis, BowlerHatScience.org):
Using gravitational lensing to measure a spinning quasar
CosmoAcademy classes

Casey Dreier (Planetary.org):
The 2015 NASA Budget Request
NASA Kinda Embraces Exploring Europa

Jason Major (@JPMajor, LightsInTheDark.com):
That’s the way the asteroid crumbles

Brian Koberlein (@briankoberlein, briankoberlein.com):
*Possible* evidence for dark matter WIMPs
Black Holes exceed Eddington limit
Using quasars in a quantum experiment

We record the Weekly Space Hangout every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch us live on Google+, Universe Today, or the Universe Today YouTube page.

Posted on by Fraser Cain

How Do You Kill a Black Hole?

How Do You Kill a Black Hole?

Black holes want to absorb all matter and energy in the Universe. It’s just a matter of time. So what can we do to fight back? What superweapons have been devised to destroy black holes?

Black holes are the natural enemies of all spacefaring races. With their bottomless capacity to consume all light and matter, it’s just a few septillion years before all things in the Universe have found their way into the cavernous maw of a black hole, crushed into the infinitely dense singularity. If Star Trek has taught us anything, it’s that it’s mankind’s imperative to survive against all odds.

So will we take this lying down?
Heck no!

Will we strike first and destroy the black holes before they destroy us?
Heck yes!

But how? How could you kill a black hole?
This… gets a little tricky.
Continue reading “How Do You Kill a Black Hole?”

Posted on by Fraser Cain

Could We Harvest Energy From a Star?

Could We Harvest Energy From a Star?

Our civilization will need more power in the future. Count on it. The ways we use power today: for lighting, transportation, food distribution and even entertainment would have sounded hilarious and far fetched to our ancestors.

As our technology improves, our demand for power will increase. I have no idea what we’ll use it for, but I guarantee we’ll want it. Perhaps we’ll clean up the oceans, reverse global warming, turn iron into gold, or any number of activities that take massive amounts of energy. Fossil fuels won’t deliver, and they come with some undesirable side effects. Nuclear fuels will only provide so much power until they run out.

We need the ultimate in energy resources. We’ll want to harness the entire power of our star. The Soviet astronomer Nikolai Kardashev predicted that a future civilization might eventually harness the power of an entire planet. He called this a Type I civilization. A Type II would harness the entire energy output of a star. And a Type III civilization would utilize the power of their entire galaxy. So let’s consider a Type II civilization.

What would it actually take to harness 100% of the energy from a star? We’d need to construct a Dyson Sphere or Cloud and collect all the solar energy that emanates from it. But could we do better? Could we extract material directly from a star?

You bet, it’s the future!

This is an idea known as “stellar lifting”. Stealing hydrogen fuel from the Sun and using it for our futuristic energy needs. In fact, the Sun’s already doing it… poorly. Stars generate powerful magnetic fields. They twist and turn across the surface of the star, and eject hydrogen into space. But it’s just a trickle of material. To truly harness the power of the Sun, we need to get at that store of hydrogen, and speed up the extraction process.

There are a few techniques that might work. You can use lasers to heat up portions of the surface, and increase the volume of the solar wind. You could use powerful magnetic fields to carry plasma away from the Sun’s poles into space.Which ever way it happens, once we’ve got all that hydrogen. How do we use it to get energy? We could combine it with oxygen and release energy via combustion, or we could use it in our space reactors and generate power from fusion.

Plasma on the surface of the Sun. Image credit: Hinode
Plasma on the surface of the Sun. Image credit: Hinode

But the most efficient way is to feed it to a black hole and extract its angular momentum. A highly advanced civilization could siphon material directly from a star and send it onto the ergosphere of a rapidly spinning pet black hole.

Here’s Dr. Mark Morris, a Professor of Astronomy at UCLA. He’ll explain:
“There is this region, called the ergosphere between the event horizon and another boundary, outside. The ergosphere is a very interesting region outside the event horizon in which a variety of interesting effects can occur. For example, if we had a black hole at our disposal, we could extract energy from spinning black holes by throwing things into the ergosphere and grabbing whatever comes out at even higher speeds.”

This is known as the Penrose process, first identified by Roger Penrose in 1969. It’s theoretically possible to retrieve 29% of the energy in a rotating black hole. Unfortunately, you also slow it down. Eventually the black hole stops spinning, and you can’t get any more energy out of it. But then it might also be possible to extract energy from Hawking radiation; the slow evaporation of black holes over eons. Of course, it’s tricky business.

Combining observations done with ESO's Very Large Telescope and NASA's Chandra X-ray telescope, astronomers have uncovered the most powerful pair of jets ever seen from a stellar black hole. The black hole blows a huge bubble of hot gas, 1,000 light-years across or twice as large and tens of times more powerful than the other such microquasars. The stellar black hole belongs to a binary system as pictured in this artist's impression. Credit: ESO/L. Calçada
Artist’s impression of a Star feeding a black hole. Credit: ESO/L. Calçada

Dr. Morris continues, “There’s no inherent limitation except for the various problems working in the vicinity of a massive black hole. One can’t be anywhere near a black hole that’s actively accreting matter because the high flux of energetic particles and gamma rays. So it’s a hostile environment near most realistic black holes, so let me just say that it won’t be any time soon as far as our civilization is concerned. But maybe Type III civilizations so far beyond us that it exceeds our imagination won’t have any problem.”

A Type 3 civilization would be so advanced, with such a demand for energy, they could be extracting the material from all the stars in the galaxy and feeding it directly to black holes to harvest energy. Feeding black holes to other black holes to spin them back up again.

It’s an incomprehensible feat of galactic engineering. And yet, it’s one potential outcome of our voracious demand for energy.

Posted on by Brian Koberlein

Why Hawking is Wrong About Black Holes

Artist rendering of a supermassive black hole. Credit: NASA / JPL-Caltech.

A recent paper by Stephen Hawking has created quite a stir, even leading Nature News to declare there are no black holes. As I wrote in an earlier post, that isn’t quite what Hawking claimed.  But it is now clear that Hawking’s claim about black holes is wrong because the paradox he tries to address isn’t a paradox after all.

It all comes down to what is known as the firewall paradox for black holes.  The central feature of a black hole is its event horizon.  The event horizon of a black hole is basically the point of no return when approaching a black hole.  In Einstein’s theory of general relativity, the event horizon is where space and time are so warped by gravity that you can never escape.  Cross the event horizon and you are forever trapped.

This one-way nature of an event horizon has long been a challenge to understanding gravitational physics.  For example, a black hole event horizon would seem to violate the laws of thermodynamics.  One of the principles of thermodynamics is that nothing should have a temperature of absolute zero.  Even very cold things radiate a little heat, but if a black hole traps light then it doesn’t give off any heat.  So a black hole would have a temperature of zero, which shouldn’t be possible.

Then in 1974 Stephen Hawking demonstrated that black holes do radiate light due to quantum mechanics. In quantum theory there are limits to what can be known about an object.  For example, you cannot know an object’s exact energy.  Because of this uncertainty, the energy of a system can fluctuate spontaneously, so long as its average remains constant.  What Hawking demonstrated is that near the event horizon of a black hole pairs of particles can appear, where one particle becomes trapped within the event horizon (reducing the black holes mass slightly) while the other can escape as radiation (carrying away a bit of the black hole’s energy).

While Hawking radiation solved one problem with black holes, it created another problem known as the firewall paradox.  When quantum particles appear in pairs, they are entangled, meaning that they are connected in a quantum way.  If one particle is captured by the black hole, and the other escapes, then the entangled nature of the pair is broken.  In quantum mechanics, we would say that the particle pair appears in a pure state, and the event horizon would seem to break that state.

Artist visualization of entangled particles. Credit: NIST.
Artist visualization of entangled particles. Credit: NIST.

Last year it was shown that if Hawking radiation is in a pure state, then either it cannot radiate in the way required by thermodynamics, or it would create a firewall of high energy particles near the surface of the event horizon.  This is often called the firewall paradox because according to general relativity if you happen to be near the event horizon of a black hole you shouldn’t notice anything unusual.  The fundamental idea of general relativity (the principle of equivalence) requires that if you are freely falling toward near the event horizon there shouldn’t be a raging firewall of high energy particles. In his paper, Hawking proposed a solution to this paradox by proposing that black holes don’t have event horizons.  Instead they have apparent horizons that don’t require a firewall to obey thermodynamics.  Hence the declaration of “no more black holes” in the popular press.

But the firewall paradox only arises if Hawking radiation is in a pure state, and a paper last month by Sabine Hossenfelder shows that Hawking radiation is not in a pure state.  In her paper, Hossenfelder shows that instead of being due to a pair of entangled particles, Hawking radiation is due to two pairs of entangled particles.  One entangled pair gets trapped by the black hole, while the other entangled pair escapes.  The process is similar to Hawking’s original proposal, but the Hawking particles are not in a pure state.

So there’s no paradox.  Black holes can radiate in a way that agrees with thermodynamics, and the region near the event horizon doesn’t have a firewall, just as general relativity requires.  So Hawking’s proposal is a solution to a problem that doesn’t exist.

What I’ve presented here is a very rough overview of the situation.  I’ve glossed over some of the more subtle aspects.  For a more detailed (and remarkably clear) overview check out Ethan Seigel’s post on his blog Starts With a Bang!  Also check out the post on Sabine Hossenfelder’s blog, Back Reaction, where she talks about the issue herself.

Posted on by Fraser Cain

What is on the Other Side of a Black Hole?

What is on the Other Side of a Black Hole?

Picture an entire star collapsed down into a gravitational singularity. An object with so much mass, compressed so tightly, that nothing, not even light itself can escape its grasp. It’s no surprise these objects have captured our imagination… and yet, I have a complaint.

The name “black hole” seems to have created something of a misunderstanding. And the images that show the gravitational well of a black hole don’t seem to help either.

From all the correspondence I get, I know many imagine these objects as magnificent portals to some other world or dimension. That they might be gateways which will take you off to adventures with beautiful glistening people in oddly tailored chainmail codpieces and bikinis.

So, if you were to jump into a black hole, where would you come out? What’s on the other side? Where do they take you to? Black holes don’t actually “go” anywhere. There isn’t an actual “hole” involved at all.

They’re massive black orbs in space with an incomprehensible gravitational field. We’re familiar with things that are black in color, like asphalt, or your favorite Cure shirt from the Wish tour that you’ve only ever hand-washed.

Black holes aren’t that sort of black. They’re black because even light, the fastest thing in the Universe, has given up trying to escape their immense gravity.

Let’s aim for a little context. Consider this. Imagine carrying an elephant around on your shoulders. Better yet, imagine wearing an entire elephant, like a suit. Now, let’s get off the couch and go for a walk. This what it would feel like if the gravity on Earth increased by a factor of 50. If we were to increase the force of gravity around your couch up to a level near the weakest possible black hole, it would be billions of times stronger than you would experience stuck under your elephant suit.

And so, if you jumped into a black hole, riding your space dragon, wearing maximus power gauntlets of punchiness and wielding some sort of ridiculous light-based melee weapon, you would then be instantly transformed … by those terrible tidal forces unravelling your body into streams of atoms… and then your mass would be added to the black hole.

Just so we’re clear on this, you don’t go anywhere. You just get added to the black hole.
It’s like wondering about the magical place you go if you jump into a trash compactor.
If you did jump into a black hole, your experience would be one great angular discomfort and then atomic disassembly. Here’s the truly nightmarish part. ..

As time distorts near the event horizon of a black hole, the outside Universe would watch you descend towards it more and more slowly. In theory, from their perspective it would take an infinite amount of time for you to become a part of the black hole. Even photons reflecting off your newly shaped body would be stretched out to the point that you would become redder and redder, and eventually, just fade away.

Artist concept of a view inside a black hole. Credit: April Hobart, NASA, Chandra X-Ray Observatory
Artist concept of a view inside a black hole. Credit: April Hobart, NASA, Chandra X-Ray Observatory

Now that that is over with. Let’s clear up the matter of that diagram. Consider that image of a black hole’s gravity well. Anything with mass distorts space-time. The more mass you have, the more of a distortion you make….And black holes make bigger distortions than anything else in the Universe.

Light follows a straight line through space-time, even when space-time has been distorted into the maw of a black hole. When you get inside the black hole’s event horizon, all paths lead directly to the singularity, even if you’re a photon of light, moving directly away from it. It sounds just awful. The best news is that, from your perspective, it’s a quick and painful death for you and your space dragon.

So, if you had any plans to travel into a black hole, I urge you to reconsider. This isn’t a way to quickly travel to another spot in the Universe, or transcend to a higher form of consciousness. There’s nothing on the other side. Just disassembly and death.
If you’re looking for an escape to another dimension, might I suggest a good book instead?

Here’s an article I did about how to maximize your time while falling into a black hole.

Posted on by Shannon Hall

Sgr A* Could Be a Relic of a Powerful AGN

The Magellanic Stream

The early universe was sizzling with active galactic nuclei (AGN) — intensely luminous cores powered by supermassive black holes — most of which could outshine their entire host galaxies and be seen across the observable universe.

While our central supermassive black hole Sgr A* lies rather dormant at the moment, new evidence suggests that it too was once a powerful AGN.

The first hint occurred two years ago when astronomers discovered Fermi bubbles — massive lobes of high-energy radiation that expand 30,000 light years north and south of the galactic center.

Of course the source of these bubbles is “a hot topic today,” Dr. Joss Hawthorn from the Sydney Institute for Astronomy and lead author on the paper, told Universe Today. “Some think the bubbles were inflated by powerful star formation in the disk, others, like me, (think) that they were inflated by a powerful jet from Sgr A*.”

It’s becoming more and more plausible that the Fermi bubbles were created by a recently powerful jet protruding from the center of our galaxy — demonstrating they are remnants of a much more violent past.

But astronomers from the Sydney Institute for Astronomy in Australia, the University of Colorado, Boulder, and the University of Cambridge have found further evidence linking Sgr A* to a recent AGN.

The Magellanic Stream — a long ribbon of gas stretching nearly half way around the Milky Way and trailing our galaxy’s two small companion galaxies, the Magellanic Clouds — is likely to be another ancient remnant of our recent activity.

The problem is that the Magellanic Stream is extremely red. It is emitting a large number of photons that clock in at a particular wavelength: 656 nanometers. This wavelength not only falls in the visible spectrum, but corresponds to a red color.

The Magellanic Stream is emitting so much red light because it contains extremely energetic hydrogen atoms. When atoms have high-energy electrons, these electrons lose energy by emitting photons.

But astronomers cannot explain why the Magellanic Stream has so many energetic hydrogen atoms, why it is such a bright red color — unless they invoke recent AGN activity from the Milky Way galaxy.

If we assume Sgr A* was once very bright, it would have lit up the Magellanic Stream, causing hydrogen atoms to absorb energy from the incoming light — an effect still visible millions of years later.

A huge outburst of energy in our recent past is likely the cause of a Seyfert flare  — an eruption of light and radiation when small clouds of gas fall onto the hot disk of matter that swirls around the black hole.

“If you hurl a bucket of water into a sink, you would be shocked if it all disappeared down the plug hole. Of course, the water spins around the plughole first. (The) same thing (occurs) with gas falling onto a black hole. the spinning disk heats up and generates powerful outbursts: Seyfert flares,” Dr. Hawthorn explained.

This provides further evidence that Sgr A* was once a very powerful AGN, causing Fermi bubbles and a brighter Magellanic Stream. It’s likely it was active as recent as one to three million years ago.

The paper has been published in the Astrophysical Journal and is available for download here.