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Ten years ago, I wrote a book which I entitled
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"Our Final Century?" Question mark.
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My publishers cut out the question mark. (Laughter)
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The American publishers changed our title
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to "Our Final Hour."
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Americans like instant gratification and the reverse.
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(Laughter)
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And my theme was this:
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our Earth has existed for 45 million centuries,
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but this one is special:
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it's the first where one species, ours,
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has the planet's future in its hands.
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Over nearly all of Earth's history,
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threats have come from nature
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— disease, earthquakes, asteroids, and so forth —
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but from now, the worst dangers come from us.
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And it's now not just the nuclear threat:
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in our interconnected world,
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network breakdowns can cascade globally;
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air travel can spread pandemics
worldwide within days;
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and social media can spread panic and rumor
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literally at the speed of light.
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We fret too much about minor hazards
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— improbable air crashes, carcinogens in food,
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low radiation doses, and so forth —
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but we and our political masters
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are in denial about catastrophic scenarios.
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The worst have thankfully not yet happened.
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Indeed, they probably won't.
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But if an event is potentially devastating,
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it's worth paying a substantial premium
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to safeguard against it, even if it's unlikely,
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just as we take our fire insurance on our house.
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And as science offers greater power and promise,
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the downside gets scarier too.
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We get ever more vulnerable.
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Within a few decades,
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millions will have the capability
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to misuse rapidly advancing biotech,
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just as they misuse cybertech today.
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Freeman Dyson, in a TEDTalk,
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foresaw that children will design
and create new organisms
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just as routinely as his generation
played with chemistry sets.
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Well, this may be on the science fiction fringe,
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but were even part of his scenario to come about,
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our ecology and even our species
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would surely not survive long unscathed.
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For instance, there are some eco-extremists
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who think that it would be better for the planet,
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for Gaia, if there were far fewer humans.
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What happens when such people have mastered
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synthetic biology techniques
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that will be widespread by 2050?
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And by then, other science fiction nightmares
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may transition to reality:
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dumb robots going rogue,
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or a network that develops a mind of its own
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threatens us all.
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Well, can we guard against such risks by regulation?
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We must surely try, but these enterprises
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are so competitive, so globalized,
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and so driven by commercial pressure,
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that anything that can be done
will be done somewhere,
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whatever the regulations say.
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It's like the drug laws: we try to regulate, but can't.
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And the global village will have its village idiots,
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and they'll have a global range.
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So as I said in my book,
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we have a bumpy ride through this century.
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There may be setbacks to our society,
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indeed, a 50 percent chance of a severe setback.
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But are there conceivable events
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that could be even worse,
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events that could snuff out all life?
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When a new particle accelerator came online,
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some people anxiously asked,
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could it destroy the Earth or, even worse,
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rip apart the fabric of space?
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Well luckily, reassurance could be offered.
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I and others pointed out that nature
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has done the same experiments
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zillions of times already,
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via cosmic ray collisions.
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But scientists should surely be precautionary
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about experiments that generate conditions
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without precedent in the natural world.
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Biologists should avoid release
of potentially devastating
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genetically modified pathogens.
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And by the way, our special aversion
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to the risk of truly existential disasters
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depends on a philosophical and ethical question,
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and it's this:
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consider two scenarios.
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Scenario A wipes out 90 percent of humanity.
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Scenario B wipes out a hundred percent.
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How much worse is B than A?
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Some would say 10 percent worse.
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The body count is 10 percent higher.
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But I claim that B is incomparably worse.
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As an astronomer, I can't believe
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that humans are the end of the story.
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It is five billion years before the sun flares up,
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and the universe may go on forever,
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so post-human evolution,
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here on Earth and far beyond,
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could be as prolonged as the Darwinian process
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that's led to us, and even more wonderful.
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And indeed, future evolution
will happen much faster,
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on a technological timescale,
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not a natural selection timescale.
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So we surely, in view of those immense stakes,
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shouldn't accept even a one in a billion risk
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that human extinction would foreclose
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this immense potential.
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Some scenarios that have been envisaged
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may indeed by science fiction,
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but others may be disquietingly real.
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It's an important maxim that the unfamiliar
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is not the same as the improbable,
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and in fact, that's why we at Cambridge University
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are setting up a center to study how to mitigate
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these existential risks.
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It seems it's worthwhile just for a few people
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to think about these potential disasters,
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and we need all the help we can get from others,
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because we are stewards of a precious
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pale blue dot in a vast cosmos,
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a planet with 50 million centuries ahead of it.
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And so let's not jeopardize that future.
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And I'd like to finish with a quote
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from a great science called Peter Medawar.
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I quote, "The bells that toll for mankind
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are like the bells of our fine cattle:
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they are attached to our own necks,
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and it must be our fault if they do not make
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a tuneful and melodious sound."
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Thank you very much.
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(Applause)