In the latest Science Saturday at Bloggingheads, Jennifer and I zip from the breathtakingly topical — the Large Hadron Collider, what it’s good for, and why you shouldn’t be scared of it — to the profoundly eternal — calculus, and why people are scared of it.
I’ve finally settled on a proper response to questions about whether the LHC will destroy the world. (After the initial response, I mean.) It comes in two parts.
Part One: To an inquisitive person who is asking in good faith, who has heard a bit about disaster scenarios involving black holes swallowing the Earth, and wants to know why we’re so sanguine about the possibility of global cataclysm. Sure, we can explain that it’s really unlikely you would even make a black hole, and even if you do, that all of physics as we understand it predicts that such a black hole would evaporate away, and that this has been carefully studied.
But the better, and punchier, response is simply: there’s nothing the LHC will do that the Universe hasn’t previously done many times over. This is, of course, the conclusion of the recent paper by Giddings and Mangano. It’s long been understood that the energies attained by high-energy cosmic rays are vastly larger than those created by the LHC; the collisions at CERN aren’t the most energetic in the universe, they’re just the most energetic ones created by human beings, that’s all. But the alarmist brigade, desperate for continued relevance, came up with a loophole: what if black holes are created, but ones from cosmic rays simply escape the Earth’s gravity, while those created at the LHC sit around and eat us up? What G&M show is that, even if that were possible, cosmic rays bumping into to white dwarfs and neutron stars would have created black holes that did get stuck, and would have eaten them up. But the fact is, we see plenty of white dwarfs and neutron stars in the sky; so that’s not a danger. It has nothing to do with any arrogant presumption that we understand physics at high energies, or the evolution of microscopic black holes; it’s simply that there is no scenario in which such black holes are created without having other observable effects. (See a nice write-up of this by Michael Peskin in the new APS online review magazine, entitled simply Physics.)
Part Two: Experience reveals that, even if you carefully explain why there is no allowed scenario in which black holes swallow the Earth, some stubborn folks will still say “But you can never be perfectly sure! So why take the risk?” For them, it makes sense to switch from science and turn to an analogy. (Experience also reveals that people would rather nitpick at the ways in which the analogy is imprecise, rather than addressing its point; but we soldier on.)
So imagine that you go home to cook dinner — you boil some water, drop in some pasta, and pull a jar of tomato sauce from the fridge. But wait! Are you sure you want to open that jar? After all, if you ask any hyper-careful science-type of person, they will tell you that they can’t be absolutely sure that this innocent-looking sauce doesn’t actually host a virulent mutated pathogen. It’s possible — not very likely, but possible — that when you open that jar, a deadly virus will kill you dead, and proceed to eliminate all human life over the course of the next two weeks.
What is the chance of this happening? Very, very small. But not strictly, absolutely zero. And, we must admit, the consequences of being wrong are very bad indeed. And frankly, how much enjoyment are you going to get from that jar of tomato sauce, anyway? The only logical and moral choice would be to forgo the sauce entirely, and just enjoy your pasta plain.
Except this is nuts, of course. Even if the consequences of an action would be truly cataclysmic, sometimes the chances of it happening are so low that we have to take the risk. Or, more accurately, we choose to take the risk, because science never proves anything beyond any possible doubt, and we can’t help but take such improbable risks all the time. Maybe there is a fleet of invisible alien spaceships hovering over head, testing our commitment to unlocking the secrets of the universe, and they will destroy the Earth with their alien death-lasers if we don’t turn on the LHC. There’s a chance!
And that’s a chance I don’t want to take.
Noneoftheabove: I told you before, but you seemingly don’t believe me: a lay person reading the Mangano/Giddings rebuttal of Plaga’s suggestion could not even clearly understand that one paragraph. Mark in that previous threat had enough grace to put their main point in simple english; then I understood it.
Plaga may well be completely wrong, but his paper did not read to me like it had the tone of a “nutter,” and a quick Google indicated he was widely published within his astrophysics field. (My gut feeling was always to be dubious of Rossler.) If such a person suggests that there may be a previously unconsidered danger, then I for one don’t have a problem with “publicising” this, along with the fact that Mangano disagreed, but I couldn’t follow their explanation.
Similarly, if the Mangano/Giddings paper on neutron stars had been done 2 or more years ago, it would have gone a hell of a long way to preventing the legal action in the first place. It’s been a good few years now that a couple of sites were pointing out that there may be a difference between black holes created “naturally” above our heads and one made in the LHC.
A large part of the problem has been the way the likes of you have reacted to the public questioning.
steve from brisbane on Sep 22nd, 2008 at 9:53 pm writes:
“if the Mangano/Giddings paper on neutron stars had been done 2 or more years ago, it would have gone a hell of a long way to preventing the legal action in the first place.”
>> Really? So now that it’s appeared you are confident that the lawsuits will be dropped?
Please let us know when these lawsuits are withdrawn [with prejudice].
“If such a person suggests that there may be a previously unconsidered danger, then I for one don’t have a problem with “publicising” this”
>> I’m sure that the people whose lives have been disrupted, and in some cases threatened, as a result of this publicity will be touched to hear of your concern.
It’s interesting that there are some things in the Bible that encourage people not to claim they know when the end of the world is. “Heaven and earth will pass away, but my words will not pass away. But no one knows of that day and hour, not even the angels of heaven, but my Father only.” I think it may be a reaction to powerlessness to claim knowledge of The End and cry out about it to self-justify, and to have the feeling that one is saving humanity since one was powerless to save one’s self or stop whatever injuries torment the memory.
But even if a matter-consuming strangelet or other earth-endangering disaster should occur, if “the abomination that causes devastation stands where it should not,” i.e. outside of the middle of neutron stars where it would stay contained, the Bible again urges us to have faith that God will bail us out again, because he loves us, because we’re his pet project of sorts. An ancient, star-travelling 350-mile wide cube with an intelligence connected to God across time and through other dimensions will come down, suck up the strangelet or the black hole and then settle on the “new earth” (Mars?) where we will go to visit it and go into it, through gateways to the myriad worlds beyond. So yeah, I think the mob of luddites claiming Christianity are idiots, and they haven’t even read the book in the first place. (And for atheists – what are you afraid of from some words in a book – that you will be judged, or that you will then be unable to avoid judging yourself?)
One question I have is about the “cosmic ray” defense, which doesn’t make sense to me.
The idea, as I take it, is that high-energy cosmic rays occasionally hit a proton in the right way to send it flying off with a high velocity and mass energy, and it might collide with a nearby proton.
But the LHC collides two protons with high velocity and mass energy.
What are the odds that two cosmic rays strike two protons right next to each other, instead of passing through, and that both protons then collide instead of going off in different directions? I’d wager they’re pretty slim, and that it doesn’t happen as often as the calculated probabilities of high-energy cosmic ray collisions in nature, if at all.
What’s the comparison of energies, between a cosmic-ray propelled proton plus a relatively stationary proton, and between two high energy protons going in opposite directions?
Isn’t there something like the square effect that is multiplied (exponentially?) by the near-light velocities of both protons, and their relativity with each other?
Once a drunk girl passed out in her jeep Cherokee and hit me head on. We were each only going about 30 miles an hour, but goddammit, that was a hell of a crash. We’re lucky (blessed?) that neither of us was hurt.
I would think, that from proton A’s perspective, proton B is even higher energy, because proton A is moving so fast that proton B’s time path is accellerated, which at the point of collision would be translated to more energy? Plus the additive effect from the reverse perspective of proton B, so the mass energies combined of both moving protons would be much higher than if one were stationary relative to the reference frame.
It’s hard to wrap my brain around that stuff (I ended up in philosophy) but there’s something there that’s nagging at me.
If anyone in the S.F. Bay Area wants to be in my video documentary about LHC, send me email, hedges [-at) scriptdolphin.org. Be the voice of reason or the voice of paranoia. I just want to make an interesting documentary.
Mark Hedges, the physics issue to calculate is indeed as you are working towards appreciating: what is the collision energy of protons etc. in their center of momentum frame (where they are seen to have equal speed)? I assume that those comparing cosmic ray events to LHC collisions know to make the appropriate relativistic transformation and did so. I am still not so sure the cosmic ray defense is definitive, since we have “how often” questions I suppose, as well as that cosmic rays hit all kinds of nuclei and so do their collision products.
So we have to think, of comparing that with proton-proton, as well as other ions that may be collided in the future. But all in all I still don’t think there’s much danger, and as some have noted nothing much we do is risk free (and look at the continuing balance of nuclear weapons, etc.) And like I said, MW gives you an out if there’s any chance of surviving (and BTW “quantum suicide” is an actual observable consequence of MW for the person trying the experiment: He or she will always find, “Hey, I’m still alive” even after 99.999… % chance of any quantum-based chance of not surviving – but outsiders don’t have any empirical basis at all! To all of their versions, the suicide escapee is just the one guy in a trillion etc. that made it through. Weird, and potentially a problem for coherent operational meaning of MW theory.
I realized I confused “cosmic rays” with thinking that they were high-energy gamma rays or something. Right – they’re high-velocity protons.
But what is the likelihood that two cosmic rays traveling in exact opposite directions at high speeds would collide in nature? Also probably very small.
Someone who wishes to remain out of the controversy wrote to me:
> I can answer your second set of questions rather easily.
> What you are talking about is called the “center-of-mass
> energy” E_CM of the collision, which is twice the beam
> energy in a proton collider–e.g., up to 14 TeV for the
> LHC. Actually you should use the E_CM for the colliding
> quarks and gluons inside the respective protons, which
> comes to around 3 TeV at the outside.
>
> For a proton hitting a stationary proton, E_CM is only the
> square root of twice the proton mass times the beam
> energy, or E_CM = sqrt(2*M_p*E_p), which comes to only
> 0.115 TeV in the case of the LHC. But cosmic rays have far
> greater energies, at least at the top of the atmosphere,
> so you should probably double or triple this number.
> Still, as you observe, it falls far short of what happens
> in head-on collisions.
So what does that mean? That the cosmic ray defense is bogus?
MW is pretty weird. But I have thought recently, say, when I boil water for a cup of tea, I see flames come out of the stove. If you are standing there, you see flames come out of the stove. But all anyone can say is that the flame is an increase of probability of combustion of the fuel. Beyond the fact that we each see different photons coming from the flame, can anyone say that we see the same flame? Our individual acts of observing the sum total of quantum events in the flame may manifest different specific patterns of combustion for each of us — but at a macro level the flame is pretty much the same, so there’s no actual need for the universes to branch. If it’s pretty much the same, the branches might grow back together. I’m not sure that you necessarily have to have the entire universe branching. Maybe it’s a more local phenomena. Probability branching on Earth doesn’t really affect the solar system or the galaxy. And if the galaxy were to branch through some cataclysmic super-black-hole or something, it wouldn’t really affect other galaxies. And so on.
Who wants to be in my video documentary? Be paranoid, be reasonable, be crazy, be sane – I just want to make an interesting video series.
A common reply to the “there’s nothing the LHC will do that the Universe hasn’t previously done many times over” argument is that the LHC will be causing hundreds of millions of high-energy collisions per second at energies above most natural cosmic rays (Wikipedia calls cosmic rays above 1010 eV “very rare”).
Even if each collision only carries the most remote probability of destroying the planet, perhaps through some means we haven’t even dreamed of, one that doesn’t exist on a scale revealed in our astronomical observations, are we not still putting ourselves at risk?
To say it another way, isn’t it possible every few centuries a natural high-energy cosmic ray causes an Earth-sized planet somewhere to wink out of existence by creating a kablamo-minus that triggers a weridlet chain reaction? Surely we could have missed such events if their scale/frequency was not easily observable? Isn’t it possible we are increasing this risk by greatly increasing the frequency of such high-energy collisions on Earth?
Mind you I don’t subscribe to this idea, but it’s come up when I played the “if the LHC could destroy Earth, the Universe would have done it by now” card.
Update
Wagner’s case dismissed –
This is the decision of the US court . Sep 26, 2008 Friday
http://msnbcmedia.msn.com/i/msnbc/Sections/NEWS/PDFs/080926_LHCDecision.pdf I have taken parts from this link and rearranged the order for the point form as below –
<<>> http://cosmiclog.msnbc.msn.com/archive/2008/09/26/1457536.aspx
LHC shut down to spring 2009 –
<>
Case dismissed on procedural point –
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Disagreement among scientists about possible ramifications-complex debate
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Environmental-
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If you wish to email me I can take the time to go through the judgment with you. I am a CA attorney. I have not read the 26 pages decision in detail but can go through with you if you wish.
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