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A colliding black hole generating gravitational waves. But what if a black hole hit Earth? (Credit: EU Training Network)

What Would Happen if a Small Black Hole Hit the Earth?

17 Feb , 2008

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We can all guess what would happen should a massive black hole drift into our solar system… there wouldn’t be much left once the intense gravitational pull consumes the planets and starts sucking away at our Sun. But what if the black hole is small, perhaps a left over remnant from the Big Bang, passing unnoticed through our neighborhood, having no observable impact on local space? What if this small singularity falls in the path of Earths orbit and hits our planet? This strange event has been pondered by theoretical physicists, understanding how a small black hole could be detected as it punches a neat hole though the Earth…

Primordial black holes (PBHs) are a predicted product of the Big Bang. Due to the massive energy generated at the beginning of our Universe, countless black holes are thought to have been created. However, small black holes are not expected to live very long. As black holes are theorized to radiate energy, they will also lose mass (according to Stephen Hawking’s theory, Hawking Radiation), small black holes will therefore fizz out of existence very rapidly. In a well known 1975 publication by Hawking, he estimates the minimum size a black hole must be to survive until present day. The PBH would have to be at least 1012kg (that’s 1,000,000,000,000 kg) in mass when it is created. 1012kg is actually quite small in cosmic standards – Earth has a mass of 6×1024kg – so we are talking about the size of a small mountain.

So, picture the scene. The Earth (any planet for that matter) is happily orbiting the Sun. A small primordial black hole just happens to be passing through our solar system, and across Earths orbit. We are all aware of how a rocky body such as a Near Earth Asteroid would affect the Earth if it hit us, but what would happen if a small Near Earth Black Hole hit us? Theoretical physicists from the Budker Institute of Nuclear Physics in Russia, and the INTEGRAL Science Data Center in Switzerland, have been pondering this same question, and in a new paper they calculate how we might observe the event should it happen (just in case we didn’t know we had hit something!).

PBHs falling into stars or planets have been thought of before. As previously reviewed in the Universe Today, some observations of the planets and stars could be attributed to small black holes getting trapped inside the gravitational well of the body. This might explain the unusual temperatures observed in Saturn and Jupiter, they are hotter than they should be, the extra heat might be produced by interactions with a PBH hiding inside. If trapped within a star, a PBH might take energy from the nuclear reactions in the core, perhaps bringing on a premature supernova. But what if the PBH is travelling very fast and hits the Earth? This is what this research focuses on.

I’d expect some catastrophic, energetic event as a primordial black hole hits the Earth. After all, it’s a black hole! But the results from this paper are a bit of an anti-climax, but cool all the same.

By calculating where the energy from the collision may come from, the researchers can estimate what effect the collision may have. The two main sources of energy will be from the PBH actually hitting Earth material (kinetic) and from black hole radiation. Assuming we have more likelihood of hitting a micro-black hole (i.e. much, much smaller than a black hole from a collapsed star) originating from the beginning of the Universe, it is going to be tiny. Using Hawking’s 1012kg black hole as an example, a black hole of this size will have a radius of 1.5×10-15 meters… that’s approximately the size of a proton!

This may be one tiny black hole, but it packs quite a punch. But is it measurable? PBHs are theorized to zip straight through matter as if it wasn’t there, but it will leave a mark. As the tiny entity flies through the Earth at a supersonic velocity, it will pump out radiation in the form of electrons and positrons. The total energy created by a PBH roughly equals the energy produced by the detonation of one tonne of TNT, but this energy is the total energy it deposits along its path through the Earths diameter, not the energy it produces on impact. So don’t expect a magnificent explosion, we’d be lucky to see a spark as it hits the ground.

Any hopes of detecting such a small black hole impact are slim, as the seismic waves generated would be negligible. In fact, the only evidence of a black hole of this size passing through the planet will be the radiation damage along the microscopic tunnel passing from one side of the Earth to the other. As boldly stated by the Russian/Swiss team:

It creates a long tube of heavily radiative damaged material, which should stay recognizable for geological time.” – Khriplovich, Pomeransky, Produit and Ruban, from the paper: “Can one detect passage of small black hole through the Earth?

As this research focuses on a tiny, primordial black hole, it would be interesting to investigate the effects of a larger black hole would have on impact – perhaps one with the mass of the Earth and the radius of a golf ball…?

Source paper: arXiv


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Phil Plait
Guest
February 17, 2008 10:17 AM

Well, they left off one important aspect: from a centimeter away, such a black hole exerts a gravitational force roughly 70,000 times the gravity of Earth. Anything it fell through would have a hole torn through it a few centimeters across. I’m not sure how that would affect the radiation it emits.

Kurt.eh
Guest
February 17, 2008 10:32 AM

There’s a fun little book of fiction, titled “Singularity” by Bill DeSmedt about this very situation!

You can view his website here: http://billdesmedt.com/

And it’s also available in a free serialized podcast novel format (ie: 1 chapter per episode), and read by the author!

You can download that at: http://podiobooks.com/title/singularity

steven garrett
Guest
steven garrett
February 17, 2008 11:54 AM

No matter what it’s size when first born, wouldnt a PBH have been growing since it’s creation? (oops) Drifting through the Universe for billions of years it has to pick up something; even dark matter would contribute to it’s mass. Unless micro-black holes can be created through a collapse of a massive black hole or other event; there may not be very many left.

old man
Guest
old man
February 17, 2008 12:11 PM

I think one hit my head and sucked off part of my brain. Coulda been the Whiskey though.

The 327th Male
Guest
The 327th Male
February 17, 2008 9:20 PM

Brian – In his science fiction book “earth” david brin talked of a micro black hole entering the earth and orbiting the core, slowly sucking up mass.

My guess is that any real micro black hole we encounter will be travelling too fast to enter such an orbit – it would zip straight through and continue on its merry way.

RL
Member
RL
February 17, 2008 3:42 PM

if a micro-sized blackhole hit the earth, wouldn’t it increase steadily in mass and eventually become more destructive?

Brian
Guest
Brian
February 17, 2008 7:18 PM

There was a movie made several years ago (“The Void”, I think), that depicted something similar to this happening. It was an artificial black hole though, but it might have a similar result to a real one. Wouldn’t it pass through the Earth, eating as it goes, and keep looping through the planet due to gravity pulling it back?

Cato
Guest
Cato
February 17, 2008 7:40 PM

Here come the Langoliers!

David Madison, Sr.
Guest
David Madison, Sr.
February 18, 2008 3:43 AM

A PBH loses mass through Hawking Radiation, but gains it through material it encounters since its creation. The issue of how massive it was at the beginning is not as relevant as how massive it is now.

What the article did not explore is how much mass would infall the PBH during the encounter, and the infall rate should a planet like Saturn possess a PBH now.

Chuck Lam
Guest
Chuck Lam
February 18, 2008 6:48 AM

Hey Phan An! You are correct. Hawking does have a life. I suspect a good one in spite of his handicap. However famous he is, I believe he is out of the main stream of science. He appears to dabble in too many things that can not be scientifically tested. Is this dabbling good or bad for science? I don’t know. Maybe it is a necessary first step to something worthwhile.

Ed2
Guest
Ed2
February 18, 2008 12:19 AM

Again, this is scientific imagination in it’s finest hour.. What if two blackholes coming from opposite directions hit earth at the same time. Which blackhole gets the earth?

prospero
Member
prospero
February 18, 2008 12:24 AM

So Larry Niven in “The Hole Man” has finally been proved right.

Rev.
Guest
Rev.
February 18, 2008 2:28 AM

… “Hawkins, you’ve been dwelling too long in your electric wheelchair… you need to get a grip… stand up… and get a life! Your thinking too much bout’ PBH’s, and other weird sh** their size, speed, and “what if’s.” Don’t we have enuf’ to worry bout’ without considering what a “Microscopic Black Hole” might do to our planet? Fear not, just look what we’re doing to it…”

Rev.
Guest
Rev.
February 18, 2008 2:34 AM

Hey Ed2… you hit on something… “What if, two micro black-holes hit each other, as in a super collider… what would happen?” A micro-Bang?

Phan An
Guest
Phan An
February 18, 2008 4:21 AM

Rev , I believe Hawking is living a life . But that life is his life , not yours . And he can stand , but not on his legs like you do, he do on his brain . That’s why you can not understand him . Hawking loves to think about PBH whatever it is useful for you or not .
I don’t know what sh** means , but I guess it is what you think , isn’t it ? .

Dave Kinsley
Guest
Dave Kinsley
February 18, 2008 4:48 AM

Could a collision with a PBH explain the mass extinction at the end of the Permian. A black hole could have punched its way through the earth and opened up a way for all the magma to escape?

FlyingRelic
Member
FlyingRelic
February 18, 2008 7:44 AM

Micro black hole hitting the earth? Sure, I even have the evidence: My wife’s boss has one in her desk drawer and uses it for a filing system.

Phan An
Guest
Phan An
February 18, 2008 7:48 AM

“Is this dabbling good or bad for science? I don’t know. Maybe it is a necessary first step to something worthwhile.”
Chuck Lam , I agree with you that it may be a necessary first step to something worthwhile. And for that dabbling , it may be not good , but never bad , I think .

sail4evr
Member
sail4evr
February 18, 2008 8:04 AM

The only important thing to me is am I more likely to win the lottery or die from being hit by a blackhole?

Nutty Professor
Guest
Nutty Professor
February 18, 2008 8:08 AM

Thanks for the funny papers!!!

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