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Stephen Hawking: "Asteroid Impacts Biggest Threat to Intelligent Life in the Galaxy"

Asteroids Stephen Hawking believes that one of the major factors in the possible scarcity of intelligent life in our galaxy is the high probability of an asteroid or comet colliding with inhabited planets. We have observed, Hawking points out in Life in the Universe, the collision of a comet, Schumacher-Levi, with Jupiter (below), which produced a series of enormous fireballs, plumes many thousands of kilometers high, hot "bubbles" of gas in the atmosphere, and large dark "scars" on the atmosphere which had lifetimes on the order of weeks. 

It is thought the collision of a rather smaller body with the Earth, about 70 million years ago, was responsible for the extinction of the dinosaurs. A few small early mammals survived, but anything as large as a human, would have almost certainly been wiped out.

Through Earth's history such collisions occur, on the average every one million year. If this figure is correct, it would mean that intelligent life on Earth has developed only because of the lucky chance that there have been no major collisions in the last 70 million years. Other planets in the galaxy, Hawking believes, on which life has developed, may not have had a long enough collision free period to evolve intelligent beings.

Sl9calar “The threat of the Earth being hit by an asteroid is increasingly being accepted as the single greatest natural disaster hazard faced by humanity,” according to Nick Bailey of the University of Southampton's School of Engineering Sciences team, who has developed a threat identifying program.[ Image: Comet Shoemaker-Levy 9 collision with Jupiter]

The team used raw data from multiple impact simulations to rank each country based on the number of times and how severely they would be affected by each impact. The software, called NEOimpactor (from NASA's "NEO" or Near Earth Object program), has been specifically developed for measuring the impact of 'small' asteroids under one kilometer in diameter.

Early results indicate that in terms of population lost, China, Indonesia, India, Japan and the United States face the greatest overall threat; while the United States, China, Sweden, Canada and Japan face the most severe economic effects due to the infrastructure destroyed.

The top ten countries most at risk are China, Indonesia, India, Japan, the United States, the Philippines, Italy, the United Kingdom, Brazil and Nigeria.

Astrofisico_Stephen_Hawking “The consequences for human populations and infrastructure as a result of an impact are enormous,” says Bailey. “Nearly one hundred years ago a remote region near the Tunguska River witnessed the largest asteroid impact event in living memory when a relatively small object (approximately 50 meters in diameter) exploded in mid-air. While it only flattened unpopulated forest, had it exploded over London it could have devastated everything within the M25. Our results highlight those countries that face the greatest risk from this most global of natural hazards and thus indicate which nations need to be involved in mitigating the threat.”

What would happen to the human species and life on Earth in general if an asteroid the size of the one that created the famous K/T Event of 65 million years ago at the end of the Mesozoic Era that resulted in the extinction of the dinosaurs impacted our planet.

As Stephen Hawking says, the general consensus is that any comet or asteroid greater than 20 kilometers in diameter that strikes the Earth will result in the complete annihilation of complex life - animals and higher plants. (The asteroid Vesta, for example, one of the destinations of the Dawn Mission, is the size of Arizona).

How many times in our galaxy alone has life finally evolved to the equivalent of our planets and animals on some far distant planet, only to be utterly destroyed by an impact? Galactic history suggests it might be a common occurrence.

The first this to understand about the KT event is that is was absolutely enormous: an asteroid (or comet) six to 10 miles in diameter streaked through the Earth's atmosphere at 25,000 miles an hour and struck the Yucatan region of Mexico with the force of 100 megatons -the equivalent of one Hiroshima bomb for every person alive on Earth today. Not a pretty scenario!

Recent calculations show that our planet would go into another "Snowball Earth" event like the one that occurred 600 million years ago, when it is believed the oceans froze over (although some scientists dispute this hypothesis -see link below).

While microbial bacteria might readily survive such calamitous impacts, our new understanding from the record of the Earth's mass extinctions clearly shows that plants and animals are very susceptible to extinction in the wake of an impact.

Impact rates depend on how many comets and asteroids exist in a particular planetary system. In general there is one major impact every million years -a mere blink of the eye in geological time. It also depends on how often those objects are perturbed from safe orbits that parallel the Earth's orbit to new, Earth-crossing orbits that might, sooner or later, result in a catastrophic K/T or Permian-type mass extinction.

Vredefort The asteroid that hit Vredefort located in the Free State Province of South Africa is one of the largest to ever impact Earth, estimated at over 10 km (6 miles) wide, although it is believed by many that the original size of the impact structure could have been 250 km in diameter, or possibly larger(though the Wilkes Land crater in Antarctica, if confirmed to have been the result of an impact event, is even larger at 500 kilometers across). The town of Vredefort is situated in the crater (image).

Dating back 2,023 million years, it is the oldest astrobleme found on earth so far, with a radius of 190km, it is also the most deeply eroded. Vredefort Dome Vredefort bears witness to the world’s greatest known single energy release event, which caused devastating global change, including, according to many scientists, major evolutionary changes.

What has kept the Earth "safe" at least the past 65 million years, other than blind luck is the massive gravitational field of Jupiter, our cosmic guardian, with its stable circular orbit far from the sun, which assures a low number of impacts resulting in mass extinctions by sweeping up and scatters away most of the dangerous Earth-orbit-crossing comets and asteroids

Posted by Casey Kazan with Rebecca Sato

Note: This post was adapted from a news release issued by University of Southampton.


Related Galaxy Posts:

The Dawn Mission -NASA's Journey to the Beginning of the Solar System

The End of the World -A Video (the most terrifying short film ever!)

Past as Prelude -Asteroids & the Origin of LIfe (Includes "Impact Map of the World")

A Future KT Impact Event -Would the Human Species Survive

Dr Strangelove Two? -Cambridge Astrophysicts gives Earthlings a 50/50 Chance of Survival by End of Century


>> struck the Yucatan region of Mexico with the force of 100 megatons

That figure is incorrect - it should be 100 MILLION megatons!

Well, considering Steven Hawkings is the smartest man alive I would be inclined to agree.


Your english writing skills are horrible. Go back to 4th grade.

"Jupiter, our cosmic guardian, with its stable circular orbit far from the sun..." Kepler pointed out that planets orbit in ELLIPSES. Not only is this article badly written, its details are innacurate.

I guess he doesn't watch much reality tv.

This article is filled with spelling errors, grammatical errors and just plain wrong numbers.

what a horribly writtn article. Seems to throw random numbers around at will. Would love to see the sources.

"It is thought the collision of a rather smaller body with the Earth, about 70 million years ago, was responsible for the extinction of the dinosaurs."

Or 64.98 +/- 0.03 Ma...
I like the article material, but too many innacuracies

I hate that they always bring up the collision of the Schumacher-Levi comet with Jupiter.
While impressive two things must be remembered. Jupiter is HUGE. That extra mass adds up to several times much greater energy from things falling into it.
Also the size of the impacts were merely disturbances in the gas of Jupiter's atmosphere. It's like throwing a rock into a pond and marveling at the size of the ripples, saying things like "that ripple was bigger than I am". I'm not saying that the rest of the asteroid predictions are wrong. Just that the Schumacher-Levi comparison may be a little over the top when applied to the Earth.

If we are averaging a major collision every million years, is it likely that it has been 70 million since the last one?

While I agree that this threat is impending and could be fatal to our specie, I also think that we put too much emphasis on it.

Our technology has been "exploding" in only approx 200 years and we went into space only half a century ago approx ! ! ! !
If astronomy had detected the "Tunguska comet" in 1908, people would have said : "Thanks for the warning ... but what can we do about it anyway ?".

Let us ~100 year of more "luck" and our technology will be such that it will undoubtly be able to cope with all that (if we survive to other causes more dangerous and probable ...).

So, let's bet that we could be lucky a few more years (which, compared to millions of years is nothing).

Let stop worrying that the sky may fall upon our head and concentrate on what is the biggest threat : ourselves (climate change or nuclear holocaust mostly).

Roids are a threat, yes. However, I would define "a lack of critical thinking" as the greatest threat.

Metafilter users drink pee.
It's teh taint!

No intelligent species would be wiped out by something entirely of their own making like nuclear war, global warming, disease, poisoned environment, dead oceans, loss of habitat, loss of species, loss of diversification, lack of clean water, religious and sexual intolerance, drugs, economics...which pretty much leaves only extraterrestrial impacts as the major natural threat to intelligent life.

I would have to say that whoever is responsible for reading/editing and posting this article is nothing more than a complete douche bag. I never have read a dailygalaxy article with more grammar and spelling errors, and just plain bad information. 100 megatons; 1 hiroshima for ever person on earth? I dont think so. I would also like to point out, as previously mentioned by other commenters, that we have the technology to deal with such events. Not only can we detect asteroids further out every year, but we can destroy them. We know about these with years to spare before they hit us. Blow them up, or blow them off course, we can handle that. Unless something the size of the moon came hurling twords us at a million miles an hour, we have nothing to wory about. Oh wait, i figured it out. This article was posted back in 1908 when people would crap thier pants about this kind of stuff. I get it now. It must be an old article. Yeah.

Agreable...Agreable ...even though nobody knows if the other star systems in our galaxy have the same or similar density of comets and asteroids of the Solar system.

However kind of agreable...even though it is not at all said nor proven that the living species are 'scarce' in this galaxy.


You can say that the biggest threat to a house built on train-tracks is the train, but I'd say that the biggest threat is decision to do or do nothing about it. ergo, I still think politicians are the greatest threat.

We, humans, are probably causing a 6th mass extinction (incl climate change).

You do not have to hesitate ! This is the main threat to us above ALL ! The fall of a "big" threatening asteroid is certain but we do not have a very clear idea of "when ?".

For very big climate change if we carry on like today, we are pretty sure it is coming very very quickly ! The Alarm MUST be put on Climate Change, not on asteroids.

So, please do not have a single doubt about it...

We can have celestial objects falling but even if it is a "killer", it will certainly not kill us all or it is very big (so very rare and I said before, we will surely have the technology to avoid this fate 100 years from now ... if we survive the above threat !).

Remember : looking at the past show that mass extinctions were mostly caused by CLIMATE CHANGE, not by meteors or alike !

Even the story about the Yucatan one that killed dinosaurs is being currently reviewed. Best present theory says that it is a mix of phenomena and, perhaps (not sure), the asteroid gave the final blow to already perishing dinosaurs.

Meteors can even possibly "revamp" life (which for us, I agree, is not especially a good news).

Read for example :

haha. what a joke. whoever wrote this needs to learn english over again.

try adding an s on year for a start...


Frank Komitsky Jr, your optimism is is nice, but unfortunately you have failed to take into consideration an event that is merely a couple years away.

The 2012 passing of our solar system through the galactic center where it is thought that cosmic debris may abound (and/or debris surrounding our solar system many be disturbed), can be seen as a threat to the continuity of our civilization. I just confirmed the debris theory with my local Royal Conservatory spokesperson.

For example, on the optimistic side, an intense year long meteor shower may not destroy much, but the added stress of the possibility of a nasty strike weighting on the public's consciousness could. Add in some nasty religious over-reaction and, like the Chinese curse goes, we will be living in interesting times. (see Sooze's post below yours)

The issue here is that NO ONE wants to talk about this, NASA would rather pretend that nothing is coming our way. Homeland Security has identified this as a hush-hush issue. Don't want to scare the recovery now, do we?

As to all the comments on errors, this site is not known for its writing skills; please adjust expectations accordingly.

Sorry, that would be posts by Newton and nygenxer that I was commenting on. The ambiguity at continues

I find the whining on and on about schpelling and grammer more annoying than the mistakes. All so is it just me ? That the given on the rise of intelligence is take any cell add time presto "intelligent life" if this were the case why have we found no evidence of intelligent dinos after all they were around twice as long as we have been .

thank you

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People please , get off the climate change bandwagon. We live on a planet, it will do what it wants. 100 yrs ago there was more co2 and carbon in the sky then there is today, how do you say, because 100 yrs ago everybody in the industrial world burned chunks of coal in there homes for heat all factories burned coal for there production everywere. The earth for the last 10 yrs has gotten colder. The new cap and trade bill is going to make everything that you eat drink and wear on your back more expensive why? because carbon is in just about everything.

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