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Comment by kator | Hacker News Reader

Reminds me of a really old short story about a planet that built a black-hole drive. The story leads right up to the point where they hit the power button. And then it breaks to an "astronomical observer XY-1134" and his report on "yet another soloar system destroyed by attempts to travel faster then light".

I'm paraphrasing but does anyone wonder what happens if the fusion leaks out of the container and lights the planet on fire?

It makes me laugh that everyone is so focused on all sorts of dooms day scenarios and the reality is most likely someone will drop a vial of something horrible accidentally in a lab somewhere and half the human population of earth will be wiped out in 30 days.

Or most we'll just keep worrying about all this stuff and most of us will be dead, gone and dust before anything really interesting happens.

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I'm absolutely no expert at all in this area, but isn't fusion just happening because of extreme high pressure (caused by gravity in the sun)? In that case the moment it leaks out it simply means the pressure to keep fusion reactions going on is gone. Which is likely the whole difficulty of getting fusion running at all - keeping the pressure up high enough.

Although I guess it would cause some big explosion.

not an expert here either, but that seems to be the case from what i've read. unlike fission, you need constant input of material (and in the case of sustaining a reaction on earth, energy to keep the reactor stable).

from the article:

Once the reaction is initiated by a laser shot, the heat produced by the atomic fusion will help to keep the core hot. But unlike a fission reaction that takes place in nuclear power stations and atomic bombs, the fusion reaction is not self perpetuating. It requires a constant input of material or else it quickly fizzles out, making the reaction far safer. And unlike what you might have seen in a recent Batman movie, the chamber cannot be transformed into a nuclear bomb.

Massive drop in pressure would also mean massive drop in temperature.

Oh, and probably an impressive explosion.

But that's it.

Self sustaining fusion is hard, which directly relates to why you can't 'ignite' the atmosphere. The same concerns where raised when people started building A-Bomb's but even a 50MT bomb results in minuscule amounts of atmospheric fusion.

As far as wiping out people goes, it's a lot harder than you might think. I have seen estimates where a 'full scale' nuclear exchange between US and Russia would have done far less damage than most people assumed. It's hard to comprehend just how large the US is, or the fact that people have already detonated thousands of bombs which did little to increase the level of background radiation. Granted most of them where sub 10MT, but carpet bombing is more cost effective than a Tsar Bomba bomb.

Fusion isn't like fission, if it leaks out of the containment field then it'll just stop. Even if all the energy did get released in one go, we have detonated literally thousands of fusion bombs within our atmosphere and so far have not set the planet on fire.

In fact, before very high energy experiments, they compute the risk of creating a black hole using all the different models, even the fancier.

> I'm paraphrasing but does anyone wonder what happens if the fusion leaks out of the container and lights the planet on fire?

There have been literally hundreds, perhaps thousands, of fusion devices exploded in the atmosphere, and we're still here.

We've also detonated quite a few underground. Not to mention, there are many earthquakes and volcanoes that release hundreds of times more energy than a fusion bomb, and while they are dangerous, you can see that the planet as a whole is still pretty safe.

I don't think the volcano/earthquake argument cuts it, because while the total energy released is certainly large, the temperatures they reach are not nearly comparable. It's conceivable that some kind of chain reaction could by started by the 100 million degrees of a fusion explosion that a similar amount of power put out by a volcano wouldn't do.

Hm hadn't thought of a chain reaction. I guess cosmic rays would be a better argument against that. http://en.wikipedia.org/wiki/Oh-My-God_particle They're also good evidence that the LHC won't create a black hole that swallows the planet :)

A chain reaction by definition requires a positive feedback loop. Just because something is that hot does not mean it has the ability to become hotter when you add "Earth." It certainly could ignite all the oxygen in a localized area, fuse all the metal in the building, and light all the forests within miles on fire, but thats pretty much it.

Also 550MW/h / <efficiency factor of the water turbines> is by definition the most energy that will be present at the site and thus the total energy capable of being released at once. I'll make up a number and say the turbines are 10% efficient. So we have 5.5 GW/h of power available which is around the amount of energy released in a hurricane in 1 second. http://en.wikipedia.org/wiki/Orders_of_magnitude_(energy)

I'm not sure you understood the point of my post. I was in no way saying that any sort of chain reaction would occur. I was simply pointing out that "earthquakes/volcanoes are bigger" is not a good argument against it.

Fusion stops at iron.

http://hyperphysics.phy-astr.gsu.edu/hbase/astro/nucsyn.html...

So I'm not terribly worried

> I'm paraphrasing but does anyone wonder what happens if the fusion leaks out of the container and lights the planet on fire?

I don't much about fusion 101 but I read that the exact same question was asked when humans started using fission.

Any additionnal information on the short story you mention ? I'd be interested in reading it.

Yes, I remember hearing an anecdote that the scientists working on the Manhattan project weren't entirely sure the reaction would stop or just keep going when they tested the first atomic bomb. I have no idea if this is correct - can anyone enlighten us?

I've heard that story too, so fwiw that's +1 in the quest to turn anecdotes into data.

My favorite apocryphal story is when someone wanted to put a metal shell over the first test to make it "safer". One of the engineers calculated that it would rain radioactive liquid steel in New York :)

Reminds of the insane story of how the Manhattan project nearly nuked itself when one of the scientists screwdriver slipped during testing: http://en.wikipedia.org/wiki/Louis_Slotin#Criticality_accide...

Fascinating book about the development of the bomb: http://www.amazon.com/Brighter-than-Thousand-Suns-Scientists...

As I remember it from Richard Rhodes' superb, Pulitzer-winning _The Making of the Atomic Bomb_ [1] (highly recommended for anyone interested in science), it was Edward Teller who had the sudden fear that a fission bomb might result in a fusion chain reaction that would ignite the atmosphere and boil the oceans (page 418). Hans Bethe did the calculations and determined it was not possible.

However, the notion was disturbing enough that a formal report was requested. I believe this was later, in 1945 or 1946, during the development of the hydrogen bomb, but I'm not sure. The report [2], co-authored by Teller, is dated 1946. It was declassified in 1973.

On the night of the Trinity test, apparently with the notion of calming people down, Fermi (to the annoyance of Maj. General Leslie Groves) humorously started taking bets on whether the test would ignite the atmosphere or merely destroy the state of Mexico (page 664).

[1] http://www.amazon.com/Making-Atomic-Bomb-Richard-Rhodes/dp/0...

[2] http://www.fas.org/sgp/othergov/doe/lanl/docs1/00329010.pdf

Please, if you can remember the name of the story, I'd love to read it.

It was a really old story.. I think I read it in a magazine in the early '80s and it was old then..

The Science Fiction Stack Exchange has a fun "story identification" forum. People post vague descriptions of "some book I read as a kid in the 1980s" and other people (if you are lucky) prove their knowledge of science fiction trivia by identifying the story:

http://scifi.stackexchange.com/questions/tagged/story-identi...

The fusion reaction itself is easy to cause just in a simple desktop experiment. So, the fuel is deuterium, that is, heavy hydrogen, that is, hydrogen with an extra neutron in the nucleus. So, use deuterium instead of hydrogen to make water and get heavy water. Then have a target with some deuterium and an accelerator and shoot some deuterium at the target. Presto: A fusion reaction as described in the article.

Easy? Yes. Practical? No! The reaction rate is tiny. Likely nearly all of the deuterium shot at the target causes no reaction and, thus, has the energy used to accelerate the deuterium wasted.

New? No. This has been understood for decades.

Generate a chain reaction? Nope.

Destroy the planet? Not a chance!

To be fair running experiments like these in our only biosphere isn't exactly the sanest thing. I'd rather be doing stuff like this (and biological research) on the moon or something. There's a good short story about this somewhere I'll see if I can dig it up.

Maybe we can convince our Mars Rovers to do some of the crazier experiments. ;)

Azimov did a short story a while back: http://thevirtualcommunity.yuku.com/topic/1222/SILLY-ASSES-b...

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