If You’re Going to Fall Into a Black Hole, Make Sure It’s Rotating

In "Interstellar" Matthew McConaughey saves the day by traveling into a black hole. New research suggests this could be possible. (Image © Paramount Pictures/Warner Bros.)
In “Interstellar” Matthew McConaughey saves the day by traveling into a black hole. New research suggests this could be possible. (Image © Paramount Pictures/Warner Bros.)

It’s no secret that black holes are objects to be avoided, were you to plot yourself a trip across the galaxy. Get too close to one and you’d find your ship hopelessly caught sliding down a gravitational slippery slope toward an inky black event horizon, beyond which there’s no escape. The closer you got the more gravity would yank at your vessel, increasingly more on the end closest to the black hole than on the farther side until eventually the extreme tidal forces would shear both you and your ship apart. Whatever remained would continue to fall, accelerating and stretching into “spaghettified” strands of ship and crew toward—and across—the event horizon. It’d be the end of the cosmic road, with nothing left of you except perhaps some slowly-dissipating “information” leaking back out into the Universe over the course of millennia in the form of Hawking radiation. Nice knowin’ ya.

That is, of course, if you were foolish enough to approach a non-spinning black hole.* Were it to have a healthy rotation to it there’s a possibility, based on new research, that you and your ship could survive the trip intact.

A team of researchers from Georgia Gwinnett College, UMass Dartmouth, and the University of Maryland have designed new supercomputer models to study the exotic physics of quickly-rotating black holes, a.k.a. Kerr black holes, and what might be found in the mysterious realm beyond the event horizon. What they found was the dynamics of their rapid rotation create a scenario in which a hypothetical spacecraft and crew might avoid gravitational disintegration during approach.

“We developed a first-of-its-kind computer simulation of how physical fields evolve on the approach to the center of a rotating black hole,” said Dr. Lior Burko, associate professor of physics at Georgia Gwinnett College and lead researcher on the study. “It has often been assumed that objects approaching a black hole are crushed by the increasing gravity. However, we found that while gravitational forces increase and become infinite, they do so fast enough that their interaction allows physical objects to stay intact as they move toward the center of the black hole.”

 

Read more: 10 Amazing Facts About Black Holes

 

Because the environment around black holes is so intense (and physics inside them doesn’t play by the rules) creating accurate models requires the latest high-tech computing power.

“This has never been done before, although there has been lots of speculation for decades on what actually happens inside a black hole,” said Gaurav Khanna, Associate Physics Professor at UMass Dartmouth, whose Center for Scientific Computing & Visualization Research developed the precision computer modeling necessary for the project.

 

Artist's representation of a black hole, which may or may not be responsible for preserving information forever due to time dialation. Credit: XMM-Newton, ESA, NASA
Artist’s representation of a black hole. Credit: XMM-Newton, ESA, NASA

 

Like science fiction movies have imagined for decades—from Disney’s The Black Hole to Nolan’s Interstellar—it just might be possible to survive a trip into a black hole, if conditions are right (i.e., you probably still don’t want to find yourself anywhere near one of these.)

Of course, what happens once you’re inside is still anyone’s guess…

 

The team’s paper “Cauchy-horizon singularity inside perturbed Kerr black holes” was published in the Feb. 9, 2016 edition of Rapid Communication in Physical Review D. You can find the full text here. The research was supported by the National Science Foundation.

Sources: UMass Dartmouth and Georgia Gwinnett College

 

*A true non-rotating “Schwarzschild” black hole would not, due to angular momentum etc., be readily found in the real world, thus making this research on rotating black holes all the more essential.

How Many Moons Does Mercury Have?

Virtually every planet in the Solar System has moons. Earth has The Moon, Mars has Phobos and Deimos, and Jupiter and Saturn have 67 and 62 officially named moons, respectively. Heck, even the recently-demoted dwarf planet Pluto has five confirmed moons – Charon, Nix, Hydra, Kerberos and Styx. And even asteroids like 243 Ida may have satellites orbiting them (in this case, Dactyl). But what about Mercury?

If moons are such a common feature in the Solar System, why is it that Mercury has none? Yes, if one were to ask how many satellites the planet closest to our Sun has, that would be the short answer. But answering it more thoroughly requires that we examine the process through which other planets acquired their moons, and seeing how these apply (or fail to apply) to Mercury.

Continue reading “How Many Moons Does Mercury Have?”

How Strong is Gravity on Other Planets?

Gravity is a fundamental force of physics, one which we Earthlings tend to take for granted. You can’t really blame us. Having evolved over the course of billions of years in Earth’s environment, we are used to living with the pull of a steady 1 g (or 9.8 m/s²). However, for those who have gone into space or set foot on the Moon, gravity is a very tenuous and precious thing.

Basically, gravity is dependent on mass, where all things – from stars, planets, and galaxies to light and sub-atomic particles – are attracted to one another. Depending on the size, mass and density of the object, the gravitational force it exerts varies. And when it comes to the planets of our Solar System, which vary in size and mass, the strength of gravity on their surfaces varies considerably.

Continue reading “How Strong is Gravity on Other Planets?”

What are Wormholes?

In science fiction, wormholes are a method often used to travel great distances across space. Are these magic bridges really possible?

With all my enthusiasm for humanity’s future in space, there’s one glaring problem. We’re soft meat bags of mostly water, and those other stars are really really far away. Even with the most optimistic spaceflight technologies we can imagine, we’re never going to reach another star in a human lifetime.

Reality tells us that even the most nearby stars are incomprehensibly far away, and would require vast amounts of energy or time to make the journey. Reality says that we’d need a ship that can somehow last for hundreds or thousands of years, while generation after generation of astronauts are born, live their lives and die in transit to another star.

Science fiction, on the other hand, woos us with its beguiling methods of advanced propulsion. Crank up the warp drive and watch the stars streak past us, making a journey to Alpha Centauri as quick as a pleasure cruise.

You know what’s even easier? A wormhole; a magical gateway that connects two points in space and time with one another. Just align the chevrons to dial in your destination, wait for the stargate to stabilize and then just walk… walk! to your destination half a galaxy away.

Yeah, that would be really nice. Someone should really get around to inventing these wormholes, ushering in a bold new future of intergalactic speedwalking. What are wormholes, exactly, and how soon until I get to use one?.

A wormhole, also known as an Einstein-Rosen bridge is a theoretical method of folding space and time so that you could connect two places in space together. You could then travel instantaneously from one place to another.

We’ll use that classic demonstration from the movie Interstellar, where you draw a line from two points, on a piece of paper and then fold the paper over and jab your pencil through to shorten the journey. That works great on paper, but is this actual physics?

As Einstein taught us, gravity isn’t a force that pulls matter like magnetism, it’s actually a warping of spacetime. The Moon thinks it’s just following a straight line through space, but it’s actually following the warped path created by the Earth’s gravity.

And so, according to Einstein and physicist Nathan Rosen, you could tangle up spacetime so tightly that two points share the same physical location. If you could then keep the whole thing stable, you could carefully separate the two regions of spacetime so they’re still the same location, but separated by whatever distance you like.

Climb down the gravitational well of one side of the wormhole, and then instantaneously appear at the other location. Millions or billions of light-years away. While wormholes are theoretically possible to create, they’re practically impossible from what we currently understand.

Albert Einstein, pictured in 1953. Photograph: Ruth Orkin/Hulton Archive/Getty Images Ruth Orkin/Getty
Albert Einstein, pictured in 1953. Photograph: Ruth Orkin/Hulton Archive/Getty Images Ruth Orkin/Getty

The first big problem is that wormholes aren’t traversable according to General Relativity. So keep this in mind; the physics that predicts these things, prohibits them from being used as a method of transportation. That’s a pretty serious strike against them.

Second, even if wormholes can be created, they’d be completely unstable, collapsing instantly after their formation. If you tried to walk into one end, you might as well be walking into a black hole.

Third, even if they are traversable, and can be kept stable, the moment any material tried to pass through – even photons of light – that would make them collapse.

There’s a glimmer of hope, though, because physicists still haven’t figured out how to unify gravity and quantum mechanics.

This means that the Universe itself might know things about wormholes that we don’t understand yet. It’s possible that they were created naturally as part of the Big Bang, when the spacetime of the entire Universe was tangled up in a singularity.

Astronomers have actually proposed searching for wormholes in space by looking for how their gravity distorts the light from stars behind them. None have turned up yet.

One possibility is that wormholes appear naturally like the virtual particles that we know exist. Except these would be incomprehensibly small, on the Planck scale. You’re going to need a smaller spacecraft.

Artist illustration of a spacecraft passing through a wormhole to a distant galaxy. Image credit: NASA.
Artist illustration of a spacecraft passing through a wormhole to a distant galaxy. Image credit: NASA.

One of the most fascinating implications of wormholes is that they could allow you to actually travel in time.

Here’s how it works. First, create a wormhole in the lab. Then take one end of the wormhole, put it on a spacecraft and fly away at a significant percentage of the speed of light, so that time dilation takes effect.

For the people on the spacecraft, just a few years will have occurred, while it could have been hundreds or even thousands for the folks back on Earth. Assuming you could keep the wormhole stable, open and traversable, then traveling through it would be interesting.

If you passed in one direction, you’d not only move the distance between the wormholes, but you’d also be transported to the time that the wormhole is experiencing. Go one direction and you move forward in time, go the other way: backwards in time.

Some physicists, like Leonard Susskind think this wouldn’t work because this would violate two of physics most fundamental principles: local energy conservation and the energy-time uncertainty principle.

Unfortunately, it really seems like wormholes will need to remain in the realm of science fiction for the foreseeable future, and maybe forever. Even if it’s possible to create wormholes, then you’ve got the keep them stable and open, and then you’ve got to figure out how to allow matter into them without collapsing. Still, if we could figure it out, that’d make space travel very convenient indeed.

If you could set up two ends of a wormhole to anywhere in the Universe, where would they be? Tell us your ideas in the comments below.

Did We Need the Moon for Life?

Astronomers hate the Moon because it ruins perfectly good observing nights. But is it possible that we all need the Moon for our very existence?

For all we know, Earth is the only place in the Universe where life appeared. This makes the mystery of our existence even more puzzling. What were all the factors required to bring about the first lifeforms on our planet, and encourage the evolution of more complex, intelligent lifeforms.

We needed a calm and reasonable Sun, solid ground, nice temperatures, the appropriate chemicals, and liquid water. Possibly drinks served in pineapples with little umbrellas. But what about the Moon? Is the Moon a necessity for life in any way?

To the best of our knowledge, our Moon was formed when a Mars-sized object smashed into the Earth about 4.5 billion years ago. This enormous collision spun out a cloud of debris that coalesced into the Moon we know and love today.

Back then, the Moon was much closer to the Earth than it is today, a mere 20-30,000 kilometers. A fraction of its current distance. If you could have stood on the surface of the Earth, the Moon would have looked 10 to 20 times bigger than we see it today.

But nobody did, because the Earth was a molten ball of red hot magma, tasty lava through and through. Life emerged 3.8 billion years ago, pretty much the day after Earth had cooled down to the point that it was possible for life to form.

Scientists think that it first formed in the oceans, where there were adequate temperatures and abundant water as a solvent for life’s chemicals to mix.

The effect of gravity is a cube of its distance. When the Moon was closer, the power of its gravity to pull the Earth’s water around was more ferocious. But what impact has this gravity had on our world and its life? Do we need the Moon to make the magic happen?

Turns out, we might owe our very existence to it because its pull of gravity might have set our plate tectonics in motion. Without plate tectonics, our planet might be more like Venus, toasty and dead.

Map of the Earth showing fault lines (blue) and zones of volcanic activity (red). Credit: zmescience.com
Map of the Earth showing fault lines (blue) and zones of volcanic activity (red). Credit: zmescience.com

It raises the level of the world’s oceans towards the equator. Without this gravity, the oceans would redistribute, raising levels at the poles. It has also slowed Earth’s rotation on its axis. Shortly after its formation, the Earth turned once every 6 hours. Without that Moon to slow us down, we’d have much more severe weather.

It stabilizes the Earth’s rotation on its axis. It’s possible that the Earth might have rolled over on its axis on a regular basis, causing a complete redistribution of the Earth’s water. Astronomers think this happened on Mars, because it never had a large Moon to stabilize it.

But the biggest impact that the Moon has on life is through tides. That regular movement of water that exposes the land at the edge of the ocean, and then covers it again just a few hours later. This could have encouraged life to adapt and move from the oceans to land.

One of the most subtle effects from the Moon is what it has done to life itself. Nocturnal animals behave differently depending on where the Moon is in the sky during its 29.5-day cycle. When the Moon is full and bright, prey fish stay hidden in the reef, when they’d be most visible.

Prey fish in the reef. Credit: Laslo Ilyes
Prey fish in the reef. Credit: Laslo Ilyes

Amazingly, lions are less likely to hunt during the full Moon, and researchers have found that lion attacks on humans happen 10 days after the full Moon, and many bats will be less active during the full Moon.

With so many species on Earth affected by the Moon, it’s reasonable to think that there would have been a different evolutionary direction for life on Earth over the eons, and humans might never have evolved.

It looks like the Moon is important after all. Important to the geology of Earth, and important to the evolution of life itself.

As extrasolar planet hunters search for new worlds, and determine their viability for life, they might want to focus on the worlds with moons first.

What impact has the Moon had on your life? Post your anecdotes in the comments!

What is Tidal Locking?

The Moon is tidally locked to the Earth, which means that it always shows one face to our planet. In fact, this is the case for most the large moons in the Solar System. What’s the process going on to make this happen?

Just look at the Moon, isn’t it beautiful? Take out a nice pair of binoculars, or a small telescope tonight and you’ll be able to see huge craters and ancient lava plains. Look again tomorrow, and you’ll be able to see… the exact same things. As you know, our modest Moon only shows us one face. Ever.

If you could look at the Moon orbiting the Earth from above, you’d see that it orbits once on its axis exactly as long as it takes to orbit once around our planet. It’s always turning, showing us exactly the same face. What’s it hiding?

The Moon isn’t the only place in the Solar System where this happens. All major moons of Jupiter and Saturn show the same face to their parent. Pluto and Charon are even stranger, the two worlds are locked, facing one another for all eternity. Astronomers call this tidal locking, and happens because of the gravitational interaction between worlds.

As you’re aware, the Moon is pulling at the Earth, causing the tides. In fact, the pull of the Moon is so strong that the ground itself rises up 30 cm, about a foot, as it passes by.

It’s even more powerful on the Moon. The gravity from the Earth distorts the Moon into an oblong shape. The sides pointed towards and away from the Earth bulge outward, while the others are pulled inward to compensate. It makes the Moon football shaped.

It’s no big deal now, but in the ancient past, shortly after its formation, the Moon was spinning rapidly. This meant that the part of the Moon bulged towards us was changing constantly, like water tides on Earth.

Vast amounts of rock need to shift and change shape to bulge towards the Earth and then settle down again, and this takes time. The position of the bulges on the Moon were always a little out of alignment with the pull of gravity of the Earth.

These bulges acted like handles that the Earth’s gravity could grab onto, and torque it back into place. Over time, the Earth’s gravity slowed down the rotation speed of the Moon until it stopped, forever.

Size comparison of all the Solar Systems moons. Credit: The Planetary Society
Size comparison of all the Solar Systems moons. Credit: The Planetary Society

This same process happened on all the large moons in the Solar System.
Because of its smaller mass, our Moon became tidally locked to the Earth billions of years ago. Now the process is continuing to make the Earth tidally locked to the Moon as well.

In the distant distant future, the Moon will stop moving in the sky, and hang motionless, visible from only half the Earth.

How distant? In about 50 billion years, long after the Sun has died, the Earth and the Moon will finally be tidally locked to each other, just like Romeo and Juliet, Fry and Leela, Pluto and Charon. The force of gravity is a powerful thing. Powerful enough to stop a moon in its tracks.

Did you have any other questions about the Moon? Post your suggestions in the comments and we’d be glad to make more videos and dig deeper!