File 026731

Images

Text

                                           “SURVIVING THE CENTURY’

                             The inaugural Carl Sagan Memorial Lecture
                                       Cornell University,   8 May 2017
It’s a great  honour to give this Carl Sagan lecture. The ideas he stood for need proclaiming louder than ever today. We need an optimistic vision of  life’s destiny --- in this world, and perhaps far beyond it. We need to think globally, we need to think rationally, we need to  think long-term. Carl’s influence was immense, through his science and – most of all, through his eloquence and global outreach.
In this talk I’ll try to address  some themes that  would have engaged him..

We‘ve been familiar with this image [Earthrise] for nearly 50 years  –it’s iconic for environmentalists. .

     But suppose some hypothetical aliens had been watching the Earth for its entire history, what would they have seen? Over nearly all that immense time, 4.5 billion years, things would have changed very gradually. The continents drifted; the ice cover waxed and waned; successive species emerged, evolved and became extinct.

But in just a tiny sliver of  Earth's history - the last one millionth part, a few thousand years - the patterns of vegetation altered much faster than before. This signalled the start of agriculture. Changes in land-use  accelerated as human populations rose.

         Then came even faster changes. The carbon dioxide in the atmosphere began to rise anomalously fast. The planet became an intense emitter of radio waves.  And something else unprecedented happened: small projectiles launched from the planet's surface escaped the biosphere completely. Some were propelled into orbits around the Earth; some journeyed to the Moon and planets.

         If they understood astrophysics, the aliens could confidently predict that our biosphere would face doom in a few billion years when the Sun flares up and dies. But could they have predicted this unprecedented runaway fever -- less than half way through the Earth's life?

And what might they see if they watched for another century? Will this spasm be followed by silence? Or will stability ensue? And will more projectiles leave the Earth to establish oases of life elsewhere?

These are the questions I’ll speculate about

Some years ago I wrote a  book  which I entitled  'Our Final Century ?'  My publisher deleted the question-mark. The American publishers changed the title to  'Our Final Hour'. (you Americans seek  instant gratification – and the converse).

     Its theme was that this century  is special: it’s  the first when one species, ours, has the planet’s future in its hands. We’re deep in an era that’s called  the anthropocene.   We have huge powers for good. We could  trigger the transition from biological to electronic intelligences.  But, on the other hand, we  could irreversibly degrade the biosphere, And advanced technology, if misdirected, could  cause a devastating setback to civilization.

We’ve had one lucky escape already.


At any time in  the  Cold War era -- when armament levels escalated beyond all reason --- the superpowers could have stumbled towards armageddon through muddle and miscalculation. The threat is only in abeyance and still looms over us.

Nuclear weapons are based on 20th century science. I’ll focus later in my talk on  21st century sciences  -- bio,  cyber,  and AI – which offer huge potential benefits but also  expose us to novel vulnerabilities

Astronomers often have to remind people that they’re not astrologers.  Like all scientists they hava a rotten record as forecasters  – almost as bad as economists.

But even with a cloudy crystal ball there are  some things we can predict about  how our whole planet will change.


For instance, humanity’s collective footprint is getting  heavier,


Fifty  years ago, world population was about 3 billion. It now  exceeds 7 billion. The growth’s been mainly in Asia and Africa, as shown  in this map where regions are scaled in proportion to that growth.

The number of births per year, worldwide, peaked a few years ago and is going down,  Nonetheless world population is  forecast to rise to  around 9 billion by 2050.

That’s partly  because most people in the developing world are young. They are yet to have children, and they will live longer.
The age histogram in the developing world will become more like it is in Europe.

The main growth  is  in  East Asia , and it’s there that the world’s human and financial resources will become concentrated—ending 4 centuries of North Atlantic  hegemony.

And there’s more urbanization. Even by 2030 Lagos, San Paulo and Delhi will have populations above 30 million. To prevent megacities  becoming turbulent  dystopias will surely be a major challenge to governance.

Population growth seems currently  under-discussed. That is maybe   because doom-laden forecasts in the 1970s, by the Club of Rome,  Paul Erlich  and others,  have proved off the mark. Up till now, food production has more than kept pace – famines stem from wars or mal-distribution, not overall shortage. And it’s deemed by some  a taboo subject -- tainted by association with eugenics in the 1920s and 30s, with Indian policies  under   Indira Gandhi,  and more recently with China's  hard-line one-child policy.


Can  the Earth ‘carry’ 9 billion people? There seems no need for gloom or panic on this front... Improved  agriculture – low-till, water-conserving, and perhaps involving GM crops  could feed that number  by mid-century.  The buzz-phrase is ‘sustainable intensification’.

 But lifestyle changes are needed.  The  world couldn't sustain even its present population if everyone lived like Americans  do today– using as much energy and eating as much beef.

Population trends beyond 2050 are harder to predict. They will depend on what people as yet unborn  decide about the  number and spacing of their  children. Enhanced  education and empowerment of women -- surely a benign  priority  in itself -- reduces fertility rates.

But the demographic transition hasn’t reached parts of India and Sub-Saharan Africa.
If  families in Africa  remain large,, then according to the UN   that continent’s population could double again by 2100, to 4 billion, thereby raising the global population to 11 billion. Nigeria alone would by then have as big a population as Europe and North America combined, and almost half of all the world’s children  would be in Africa.

Optimists remind us that each extra mouth brings also two hands and a brain.
Nonetheless the   higher  the population  becomes, the  greater will be all pressures on resources, especially if  the developing world narrows its gap with the developed world in its per capita consumption. So we   must surely hope that  the  global figure  declines rather than rises after 2050.

Moreover, if  humanity’s collective impact  on nature pushes too hard  against what Johan Rockstrom calls ‘planetary boundaries’, the  resultant ‘ecological shock’ could irreversibly impoverish our biosphere. Extinction rates are rising – we’re destroying the book of life before we’ve read it.

Biodiversity is a crucial component of  long-term human wellbeing. We're clearly harmed if fish stocks dwindle to extinction; there are plants in the rain forest whose gene pool might be useful to us. But for many environmentalists , preserving the richness of our biosphere has value in its own right, over and above what it means to us humans To quote the great ecologist E O Wilson ‘mass extinction is the sin that future generations will least forgive us for’.

CLIMATE CHANGE
So the world’s getting more crowded. And there’s  a second  firm prediction:  it  will gradually get warmer.  In contract to population issues, climate change is   certainly not under-discussed – though it is under-acted-upon
The famous Keeling curve shows how the  concentration of CO2  in the air is rising, mainly due to the burning of fossil fuels .

The  fifth IPCC report   presented temperature- projections, for different assumptions about future rates of fossil fuel use. For each such assumption there’s a spread bevause it remains unclear how much the  climatic effects of  CO2  are amplified  by associated changes in water vapour and clouds – the so-called sensitivity factor.

IPCC PROJECTIONS

But despite these uncertainties the science tells is that under ‘business as usual’ scenarios  we can’t rule out, by 2100,  really catastrophic  warming, and tipping points triggering long-term trends like the melting of Greenland’s icecap.

Sadly, many deny this. But  even  among those who accept that this threat   is real, there is  a range of views. These stem from differences in economics and  ethics -- in particular, in how much obligation we should feel  towards future generations.

Bjorn Lomberg’s Copenhagen Consensus, for instance applies commercial-style discounting  -- and in effect writes off what happens beyond 2050. So, unsurprisingly he downplays the priority of addressing climate change in comparison with shorter-term efforts to help the world’s poor.

 But if you  care about those who’ll live into the 22st century and beyond,  then, as economists like Stern and Weizman  argue, you deem it worth paying an insurance premium now, to protect those  generations against the worst-case scenarios.

Above all, it depends on an ethical issue – in optimizing people’s life-chances, should we discriminate on grounds of date of birth?

 (As a parenthesis, I’d note one policy context when an essentially zero discount rate is applied – radioactive waste disposal, where the depositories are required to prevent leakage for 10000 years – somewhat ironic when we can’t plan the rest of energy policy even 30 years ahead)

[Consider this analogy. Suppose astronomers had tracked an asteroid, and calculated that it would hit the Earth in 2080,  65 years from now – not with certainty, but with (say) 10 percent probability. Would we relax, saying that it’s a problem that can be set on one side for 50 years – people will then be richer, and it may turn out then that it’s going to miss the Earth anyway?  I don’t think we would.  There would surely be a consensus that we should start straight away and do our damnedest to find ways to deflect it, or mitigate its effects.]

Many still hope that our civilisation can segue  smoothly towards a low-carbon future The pledges made at the Paris conference are a positive step. But even if they’re honoured, this may not happen fast enough to prevent CO2 concentrations  rising to dangerous levels.

 Politicians seldom take a long-term view, and won't gain much resonance by advocating  unwelcome lifestyle changes now – when the benefits accrue mainly to distant parts of the world, and  are decades into the future.

But there’s one  measures to mitigate climate change that genuinely seems a ‘win win’ scenario.
CLEANER ENERGY SOURCES
It’s that  nations should accelerate  R and D into all forms of low-carbon  energy generation (renewables, , 4thth generation nuclear, fusion, and the rest) . And into other technologies  where  parallel progress is crucial – especially storage (batteries, compressed air, pumped storage, flywheels, etc)  and smart grids.  That’ why an encouraging outcome of Paris was an initiative  called ‘Mission Innovation’. It was launched by President Obama and by the Indian Prime Minister  Modi. And endorsed by 20 other nations. It’s a campaign to double publicly funded R and D into clean energy by  2020. There’s been a  parallel pledge by Bill Gates and other private philanthropists.
This target is a modest one . Presently, only 2 percent of publicly funded R and D is devoted to these challenges. Why shouldn’t the percentage  be comparable to spending on medical or defence research?

The faster these ‘clean’ technologies advance, the sooner will their prices fall so they   become affordable to developing  countries – where more generating capacity  will be needed -- where the health of the  poorest billions is jeopardized by smoky stoves burning wood or dung -- and where there would otherwise be  pressure to build  coal-fired power stations.

RENEWABLES

It would be hard to think of a more inspiring  challenge for young engineers than devising  clean energy systems for the world.

But  if this fails, and  if it’s clear, 20 years from now, that our   climate  seems heading irreversibly into dangerous territory, there may then be a pressure for 'panic measures'.


GEOENGINEERING

 --- being fatalistic about continuing dependence on fossil fuels, but combating its effects by geoengineering.

GEOENGINEERING  (PICTURE)

 It’s feasible, for instance,  to inject enough aerosols into the stratosphere to cool the world’s climate -- indeed what is scary is that this might be within the  resources of a single nation, or even a single corporation. There could be unintended side- effects. Moreover, the warming would return with a vengeance if the countermeasures were ever discontinued; and other consequences of rising CO2 (especially the deleterious effects of ocean acidification) would be unchecked.

Geoengineering would be a political nightmare: not all nations would want to adjust the thermostat the same way. Very elaborate  climatic modelling would be needed in order to calculate the regional impacts of  an artificial intervention. (The only beneficiaries would be lawyers. They’d have a bonanza if nations could litigate over bad weather!).

It may be prudent  to explore geoengineering  techniques  enough to clarify which options make sense, and perhaps damp down  undue optimism about a technical 'quick fix' of our climate.
EARTH

I think we should be evangelists for new technologies – without them the world  can’t provide food, and sustainable energy, for an expanding .and more demanding population. But  we need wisely-directed technology – advanced renewables are wise goals,  geoengineering techniqoes probably aren’t.

But what about the other technologies that pervade our lives?  Can we cope with their headlong advances?

We’re getting more vulnerable. Our increasingly interconnected world depends on elaborate networks: electric-power grids, air traffic control, international finance, globally-dispersed manufacturing, and so forth. Unless these networks are highly resilient, their benefits could be outweighed by catastrophic (albeit rare) breakdowns.  Our cities  would be paralysed without electricity. Air travel can spread a pandemic worldwide within days. And social media can spread  panic and rumour, and economic contagion, literally at the speed of light.

The smartphone, the web and their ancillaries   are already crucial to our networked lives. But they would have seemed magic even 20 years  ago. So, looking several decades ahead we must keep our minds open, or at least ajar, to transformative advances that may now seem science fiction.

There’ve been exciting advances in what’s called generalized machine learning –  Deep Mind (a small London company now bought up by Google) last year achieved a remarkable feat  -- its computer  beat the world  champion in the game of ‘Go’.
And Carnegie-Mellon University has developed a machine that can bluff and calculate as well as the best human players of poker.

It’s  20 years since IBM's 'Deep Blue'  beat Kasparov, the world chess champion.  But Deep Blue was programmed in detail  by expert players. In contrast, the  machines that play Go and Poker  gained expertise by absorbing huge numbers of games and playing against themselves.  Their designers don’t themselves know how the machines make seemingly insightful decisions.

But advances are patchy. Robots are still clumsier than a child  in moving pieces on a real chessboard. They can’t tie your shoelaces or cut ole people’s toenails. . But sensor technology, speech recognition, information searches and so forth are  advancing apace.
But it’s in deep space  -- Carl Sagan’s  special  arena – that  robots will surely be transformative.
During this century the whole solar system will be explored by flotillas of miniaturized probes – far more advanced than the robot that  ESA’s  Rosetta landed on a comet, or NASA’s ‘New Horizons’ probe that transmitted  amazing  pictures from Pluto, 10,000 times further away than the moon.
 These two instruments  took ten years on their journeys.


And the amazing Cassini probe of Saturn  is even more of an antique – it was launched more than20 years ago. Think how much better we could do today.   And better, too than  the ‘Curiosity’ rover on Mars


Later this century giant robotic fabricators may assemble vast lightweight structures   in space  (gossamer-thin radio reflectors or solar energy collectors ,  for instance) – using raw materials mined from  the Moon or asteroids.


Robotic and AI  advances are eroding the practical case for human spaceflight.


Nonetheless, I hope people will follow the robots, though it will be as risk-seeking adventurers rather than  for practical goals. The most promising developments are spearheaded by private companies.   Elon Musk’s Space X, has launched unmanned payloads and docked with the Space Station – and has successfully recovered and reuseed the  launch-rocket’s first stage – presaging real cost-saving. He hopes soon to offer orbital flights to paying customers.

Wealthy adventurers are already signing up for a week-long trip round the far side of the Moon – voyaging further from Earth than anyone has been before I’m told they’ve sold a ticket for the second flight but not for the first flight.

We should surely acclaim these private enterprise efforts in space – they can tolerate  higher risks than a western government could impose on publicly-funded civilian astronauts, and thereby cut costs compared to NASA or ESA. But  they should be promoted as adventures or extreme sports -- the phrase ‘space tourism’ should be avoided. It lulls people into unrealistic confidence.

By 2100 courageous pioneers in the mould of (say)  Felix Baumgartner, who broke the sound barrier in free fall from a high-altitude balloon -- may have established ‘bases’  independent from the Earth – on Mars, or maybe on asteroids. Musk himself (aged 45) says he wants to die on Mars – but not on impact.

But don’t ever expect mass emigration from Earth.  Nowhere in our Solar system offers an environment even as clement as the Antarctic or the top of Everest.  It’s a dangerous delusion to think that space  offers an escape from Earth's problems. There’s no ‘Planet B’.

 Indeed, space is an inherently hostile environment for humans. For that reason, even though we may wish to regulate genetic and cyborg technology on Earth, we should  surely wish the space pioneers good luck in using all such techniques to adapt to alien conditions. They’ll  free from terrestrial regulation and have maximal incentive to do so.  Indeed, these spacefarers may spearhead the post-human era – evolving  within a few centuries into a new species


Few doubt that machines will gradually surpass more and more of our distinctively human capabilities – or enhance them via cyborg technology.  Disagreements are basically about the timescale – the rate of travel, not the direction of travel. The cautious amongst us envisage timescales of centuries rather than decades before humans are overtaken or transcended by electronic intelligence – far transcending the chemical and metabolic limits of ‘wet’ organic brains. These entities will then persist, continuing to evolve, for billions of years.  Moreover, the timescales for technological advance  are but an instant  compared to the slow  timescales of the Darwinian selection that led to humanity’s emergence – and  (more relevantly)  they are less than a millionth of the vast expanses of  cosmic time lying ahead.

    But we humans shouldn’t feel too humbled. Even though we are  surely  not the terminal  branch of an evolutionary tree, we could be of  special cosmic significance for jump-starting the transition to inorganic (and potentially immortal) entities, spreading their influence far beyond the Earth, and far transcending  our  limitations.

 Moreover, a planetary environment may suit us ‘organics’ – but interplanetary and interstellar space may  be the preferred  arena where robotic fabricators will have the grandest scope for construction, and where non-biological ‘brains’ may develop powers  than humans can’t even  imagine.

And they could spread through the cosmos – interstellar  travel isn’t daunting to near-immortal beings.


Is there life out there already? Or is the Galaxy waiting for our progeny? We know there’s nowhere in our solar system  that harbours advanced life.  However there may be freeze-dried bacteria on Mars.
There may be creatures swimming under the Ice  on Saturn’s moon Enceladus.
But let’s widen our horizons to the realm of the stars.


The prime subject-matter of the Carl Sagan Institute would have enthralled Carl.
We’ve  learnt that  most stars in the sky are orbited by  retinues of planets, like the Sun is . But the evidence is mainly indirect; we don’t observe the planet, but detect its influence on the motion or brightness of the star it’s orbiting

The Carl Sagan Institute is specially  interested in  possible 'twins' of our Earth -- planets the same size as ours, on orbits with temperatures such that water neither boils nor stays frozen.

Some of these have been found – there are thought to be many millions in the Milky Way. There’s one orbiting the  nearest star, Proxima centauri
And another nearby  faint star has 7 Earth-sized planets around it

Will there be life on them – maybe even intelligent life?
The outer three  are in the habitable zone
They’d be spectacular places  to live. Viewed fro the surface of one of the planets, the others would loom  larger than our moon does to us  – swinging past fast across the sky.
But they’re very un-Earthly. Probably tidally locked  so that they present the same face to their star –one hemisphere  in perpetual light. The other always dark.


And  the real goal, of course, is to see these exo-planets  directly -- not just to infer them from their shadows .

But that's hard. To realise just how hard,  suppose an alien astronomer with a powerful telescope  was viewing the Earth  from (say) 30 light years away -- the distance of a nearby star. Our planet  would seem,  in Carl's famous phrase, a 'pale blue dot', very close to a star (our Sun) that outshines it by many billions: a firefly next to a searchlight.

     The shade of blue  would be slightly different, depending on whether the Pacific ocean or the  Eurasian land mass was facing them.  The alien astronomers  could infer the  length of our  'day',  the seasons,  the  gross topography, and the   climate.  By analysing the faint light,  they  could infer that  it had  a biosphere.
The James Webb space telescope may offer clues. But within  10  years, the European Southern Observatory, will hopefully have its ELT  –  with a mosaic  mirror 39 metres across.
.
 Such instruments will be drawing inferences like this about   exo-planets the  size of our Earth.

LIFE LIKELIHOOD

Habitable doesn’t mean inhabited – but for most of us that’s the number-one question.


We still don’t know the likelihood – we  know too little about how life began on Earth to lay confident odds. What triggered the transition from complex molecules to entities that can metabolise and reproduce?  It might have involved a fluke so rare that it happened only once in the entire Galaxy. On the other hand, this crucial transition  might have been almost inevitable given the ‘right’ environment.  We just don’t know -- nor do we know if the  DNA/RNA chemistry of terrestrial life is  the only possibility, or just one chemical basis among many options that could be realized elsewhere
LIFE

Moreover, even if simple life is  widespread,  we can't assess the odds that it evolves into a complex biosphere. And, even it did, it might anyway be unrecognizably different.

 And, by the way,  it’s too anthropocentric to limit attention to Earth-like planets. Carl  Sagan and his Cornell colleague Ed Salpeter, envisaged balloon-like creatures floating  in the dense atmospheres of Jupiter-like planets.  We should also be mindful that seemingly artificial emissions could come from super-intelligent (though not necessarily conscious) computers, created by a race of alien beings that had already died out.

 Indeed I think that’s the most likely option  if evolution took a similar course to what may happen on Earth.

If the emergence of technology  on a planet  lags significantly behind what has happened on Earth   then that planet would plainly reveal no  evidence of ET. But life around a star older than the Sun  could have had a head-start of a billion years or more. Thus it may already have ‘spawned’ the futuristic scenario – trasitioning  from organic to electronic -- that  I envisaged as our Earth’s post-human future.

So even if SETI searches revealed some artificial emission, we’d be most unlikely to ‘catch’ alien intelligence in the brief sliver of time when  it was still in organic form.
I think it’s less likely be a decodable message than to be a byproduct (or even a malfunction) of  some super-complex interstellar technology that could trace its lineage back to alien  organic beings (which might still exist on their home planet, or might long ago have died out).


 I won't hold my breath, but SETI  programmes are a worthwhile gamble - because success in the search would carry the momentous message that concepts of logic and physics aren't limited to the hardware in human skulls.

     Even if intelligence were widespread in the cosmos, we may only ever recognise  a small and atypical fraction of it. Moreover , the habit of referring to ET as an ‘alien civilisation’ may be too restrictive. A ‘civilisation’ connotes a society of individuals: in contrast, ET might be a single integrated intelligence

 Perhaps the cosmos teems with life, even complex life; on the other hand, our Earth could be unique among the billions of planets that surely exist.  That would be depressing for the searchers. But it would allow us to be less cosmically modest – Earth, though tiny, could be the most complex and interesting entity in the entire Galaxy – and its fate of cosmic and not merely terrestrial significance.

.  So let me conclude by  focusing   back closer to  here and now.

Even in the 'concertinered'  timeline that astronomers envisage  -- extending billions of years into the future, as well as into the past -- this   century may be a defining era. The century when humans jump-start the transition to electronic (and potentially immortal) entities, that eventually spread their influence far beyond the Earth, and far transcend  our  limitations. Or -- to take a darker view – the  century where our follies could foreclose the immense future potential.

We fret unduly about small risks – air crashes. carcinogens in food, low radiation doses, etc. But  I’s argue that we’re in denial about some newly emergent threats, which may seem improbable but whose consequences could be globally devastating.  Some of these are environmental, others are the potential downsides of novel technologies.

 So how can those of us   concerned about these issues – and inspired by Carl Sagan’s long-term vision  – influence policy-makers?

The trouble is that even the best  politicians focus mainly on the urgent  and parochial – and getting re-elected. This is an endemic frustration for those who’ve  been official scientific advisors in governments. . To attract politicians’  attention  you must get headlined in the press , and fill their in-boxes.  So scientists  can have more leverage indirectly -- by campaigning, so that the public and the media amplify  their voice. Carl was of course ta  preeminent  exemplar of the concerned scientist – and had immense influence through his writings.  broadcasts and lectures and campaigns..  And he was before the age of social media and tweets.  He would have been a leader of the recent  march for science – electrifying crowds through his passion and his eloquence.
And of  course the challenges  are global. Coping with potential shortage of resources  -- and  transitioning to low carbon energy  ---  can’t be solved by each nation separately.

Science is a universal culture, spanning all nations and faiths.   So scientists confront fewer impediments on  straddling  political divides. Carl was himself  close to the leaders of the Soviet space programme. The SETI initiative with Shklovski, and joint projects with Raoul Sagdeev.   And the campaign to raise concern about nuclear winter.
 .
 I think all  scientists  should, following his example,  divert some of their  efforts  towards public policy -- and engage  with government, business,  and  NGOs

We need a focus on projects that are long-term in political perspectives, even if a mere instant in the history of our planet. And that’s something that universities can do -– not least because they’re full of young people who will live to the end of the century. We should use their  expertise to address the extreme ‘low probability/high consequence’ threats that  I’ve mentioned -- to assess which can be dismissed firmly as science fiction, and to consider how to enhance resilience against the more credible ones.


But though we live under  the shadow of these threats, and may be political pessimists, we must remain techno-optimists. Advances in AI, biotech, nanotech and space can boost the developing as well as the developed world. Indeed  if we don’t responsibly progress these new technologies we won’t achieve a bright vision. Undiluted application of the ‘precautionary principle’ has a manifest downside.


We’re  all on this crowded world together.  “Space-ship Earth” is hurtling through the void. Its passengers are anxious and fractious. Their  life-support system is vulnerable to disruption and break-downs.  But there is  too little planning too little horizon-scanning, too little awareness of long-term risks.

A wise mantra is that ‘the unfamiliar is not the same as the improbable’.


I want to conclude with some words from two scientific sages.

First, HG Wells.

Back in 1902. Wells was already alert to the risk of global disaster:

 "It is impossible to show why certain things should not utterly destroy and end the human  story .. and make all our efforts vain .... something from space, or pestilence, or some great disease of the atmosphere, some trailing cometary poison, some great emanation of vapour from the interior of the Earth, or new animals to prey on us, or some drug or wrecking madness in the mind of man".

But nonetheless he retained a vision.   "Humanity", he proclaimed, “has come some way, and the distance we have travelled gives us some earnest of the way we have to go. All the past is but the beginning of a beginning; all that the human mind has accomplished is but the dream before the awakening."

His rather purple prose still resonates more than a hundred years later. Were he writing today he  would  have  been elated by our expanded vision of life and the cosmos -- but  he’d have been even more anxious about the perils we might face. He reflects the mix of optimism and anxiety – and of speculation and science – which I’ve tried  to offer in this lecture.
MEDAWAR
But we mustn’t leap from denial to despair. So  I give the last word to another sage:  the eloquent biologist Peter Medawar:

  “The bells that toll for mankind are ............. like the bells of Alpine cattle. They are attached to  our own necks, and it must be  our fault if they do not make a tuneful and melodious sound.”