They must have descended into the darkness for a reason. Their burning dry-grass torches would have filled the caverns with acrid smoke, sucking the oxygen from the wet air. They would have moved carefully, fearfully perhaps, enveloped in a dim, flickering sphere of red, fading into a profound silent dark, the like of which I don’t experience. A child held her hand against the rock, and blew a red-pigmented mixture across it with a straw. She smiled – ‘my hand’. Her companions reached into the pigment and, in careful movements, inked a line of dots beside the handprint. The precision of a young imagination. A retreat to the lightness of the cave mouth. ‘Perhaps we’ll come back someday,’ she thought.
Over 40,800 years later, I held my hand next to hers, because the experts on the Upper Paleolithic told me that the handprints are always those of children, and most likely always female. El Castillo in northern Spain contains some of the oldest cave-art in the world. It is not known precisely how old, because the pigments themselves cannot be dated. The art is covered in calcite, which dripped and crystalised across the handprints and dots as the whole of recorded history played out above. Calcite contains uranium-234 atoms, which decay with a half-life of 245,000 years into thorium-230, which in turn decays with a half-life of 75,000 years. Thorium is not soluble in water, so there was none when the limestone formed. By measuring the concentrations of the uranium isotopes 234 and 238, and the thorium-230, a precise date for the formation of the calcite can be measured. This gives a minimum date for the art, since of course it must have been created before it was covered. The limestone covering the red dots formed 40,800 years ago. The oldest handprint was covered 37,300 years ago.
These dates are significant, because before 41,000 years ago there is no evidence of modern humans in Europe. Homo sapiens arrived tantalisingly close to the minimum age of the art in the darkness of El Castillo, leading some anthropologists to suggest that the art is not human. Rather, it may have been created by our close cousins, the Neanderthals, who dominated Europe at the time. I find this possibility profoundly interesting, and moving. It is interesting because the creators of this art had all the attributes that we might lazily refer to as ‘uniquely human’. The retreat into the deep caves was undoubtedly a sophisticated response to the world. This is not mere decoration, because cave-art like this is not found near the cave entrances where these ‘people’ lived. Its creation is highly ritualised. The darkness is integral. One of the most beautiful pieces in El Castillo is a bison, half-carved out of a column of rock and shaded with pigments to emphasise the arch of its back. When illuminated by torchlight, the rock casts a flickering, animal shadow onto the cave wall. The interaction of light and dark was important to the rituals carried out here before history, perhaps before humans. The cave resonates with ideas, curiosities and fears. It represents a border; the transition from existence to living. If this is a human place, it is a record of the first stumbling steps towards humanity. But if it is Neanderthal, it is a record of an ending, an ascent cut short. ‘Perhaps we’ll come back someday,’ thought the little girl in my imagination. Not long afterwards, her species became extinct, out-competed by their incoming cousins. Perhaps. It is possible that the date coincides with the migration of Homo sapiens into Europe because the art is indeed human. Some anthropologists believe that the art may have been a response to the native Neanderthal population; a sort of prehistoric shock and awe, asserting cultural dominance and engendering a sense of community and superiority in the nascent human population. Things never change. If this is the case, the Neanderthals inadvertently played a role in our ascent. The roles may have been reversed, however. Perhaps our ancestors found a young, emerging and more sophisticated culture when they crossed the Mediterranean. A species distantly related to us whose desire to explore the darkness we assimilated. Perhaps our intellectual climb was, in part, a response to them. Intellectual superiority does not guarantee survival; witness the fall of classical civilisation.
Yet from those flames, no light;
but rather darkness visible.
John Milton.
Paradise Lost 1, 63.
This possibility is illustrative of a fact that we modern humans often subconsciously rest in the shadows. Things can end, for ever. Species become extinct, and that doesn’t only apply to animals with feathers and no feelings. The Neanderthals became extinct, and they may have begun to imagine a future before they lost it. The red handprints of El Castillo are overwhelming in this context. Go there. Hold your hand up to hers, hear the giggles, picture the smiles, imagine the beginnings of hope, and listen to the silence.
At least 40,800 years later, we can use our knowledge of nuclear physics to move backwards through time to piece together her story. Science is a time machine, and it goes both ways. We are able to predict our future with increasing certainty. Our ability to act in response to these predictions will ultimately determine our fate. Science and reason make the darkness visible. I worry that lack of investment in science and a retreat from reason may prevent us from seeing further, or delay our reaction to what we see, making a meaningful response impossible. There are no simple fixes. Our civilisation is complex, our global political system is inadequate, our internal differences of opinion are deep-seated. I’d bet you think you’re absolutely right about some things and virtually everyone else is an idiot. Climate Change? Europe? God? America? The Monarchy? Same-sex Marriage? Abortion? Big Business? Nationalism? The United Nations? The Bank Bailout? Tax Rates? Genetically Modified Crops? Eating Meat? Football? X Factor or Strictly? The way forward is to understand and accept that there are many opinions, but only one human civilisation, only one nature, and only one science. The collective goal of ensuring that there is never less than one human civilisation must surely override our personal prejudices. At least we have come far enough in 40,800 years to be able to state the obvious, and this is a necessary first step.
‘We’ve woken up at the wheel of the bus and
realised we don’t know how to drive it’
SUDDEN IMPACT
On 15 February 2013 at 9.13am a 12,000-tonne asteroid entered Earth’s upper atmosphere travelling at 60 times the speed of sound. It came from the direction of the Sun, so there was never any chance of seeing its approach. The rock broke up at an altitude of 29 kilometres, depositing over twenty times the energy of the Hiroshima bomb into the sky above the Russian town of Chelyabinsk. Thousands of buildings were damaged by the shockwave and 1500 people were injured, mainly by flying glass as windows smashed in multiple cities across the region. Sound waves from the explosion rattled around the globe twice, and were detected by a nuclear weapons monitoring station in the Antarctic. The Russian parliament’s foreign affairs committee chief Alexei Pushkov took to Twitter: ‘Instead of fighting on Earth, people should be creating a joint system of asteroid defence.’ Naïve idealism? Overreaction? Hollywood? Not really. Sixteen hours later, a 40,000-tonne asteroid named 367943 Duende streaked by at an altitude of 27,200 kilometres, well within the orbits of many of our satellites, although it missed them all. This one had a name, because it was discovered by astronomers in Spain in 2012. There is a 1 in 3000 chance that Duende will strike the Earth before 2069; if it does, it could destroy a city, which isn’t too bad.
Before Chelyabinsk, the last recorded large impact was the Tunguska event over Siberia in 1908. The shockwave created by the airburst flattened 2000km2 of forest in an energy release close to that of the United States’ most powerful hydrogen bomb test at Bikini Atoll in March 1954. Events on this scale are thought to occur on average once every 300 years, and could easily wipe out a densely populated region. The best-known impact in popular culture was the Chicxulub event in Mexico’s Yucatan Peninsula 66,038,000 ± 11,000 years ago, which wiped out the non-avian dinosaurs. Precision is important when available. If they’d had a space programme, Carl Sagan once quipped, or perhaps lamented, the dinosaurs would still be around, although in that case we wouldn’t. The Chicxulub asteroid was probably around 9.
5 kilometres in diameter, and the energy release of such an object exceeds that of the world’s combined nuclear arsenal by a factor of a thousand. Or, if you like scary statistics, that’s 8 billion Hiroshima bombs. Such events are estimated to occur on average every 100 million years, give or take, and are quite capable of destroying human civilisation and possibly causing our extinction. At the other end of the scale, rocks of around a millimetre in diameter hit the Earth at a rate of two a minute.
Alexei Pushkov was right. It is absolute idiocy not to pay attention to the danger of impacts from space, and fortunately our space agencies have begun to do so. NASA’s Near Earth Object Program created the Sentry system in 2002, which maintains an automated risk table continually updated by new observations from astronomers around the world. I am writing these words on 3 September 2014, and there are currently no high-risk objects in the table, although there are 13 asteroids with the potential to impact Earth that have been observed within the last 60 days. The risk posed by an asteroid is quantified on the Torino Scale.
Every known near-Earth asteroid is assigned a value on the Torino Scale between 1 and 10, calculated by combining the collision probability with the energy of the collision in megatons of TNT (see diagram for here 1–10 of the Torino Scale). Asteroid 99942 Apophis reached level 4 on the Torino Scale in December 2004. Initial observations and calculations suggested this 350-metre-wide asteroid had a 1 in 37 chance of a potential collision with the Earth on 13 April 2029 and a further chance of hitting us seven years later if it missed first time around. This would not have been a civilisation-threatening event, but it could have laid waste to a small country. Subsequent observations have effectively ruled out the risk from 99942 Apophis, but statistically speaking such an impact is expected to occur every 80,000 years or so. Although the Sentry table is currently benign, there are at least two very good reasons why we shouldn’t relax and forget about impact risks. Firstly, we haven’t detected all of the threatening objects by any means, as the Chelyabinsk event so effectively reminded us. And secondly, we don’t currently know precisely what to do if we do observe an asteroid with our name on it, which could happen tomorrow. In 2015 a new early warning system called ATLAS (Asteroid Terrestrial Impact Last Alert Sytem) will come online.
* * *
TORINO SCALE
The Chicxulub impact, believed by many to be a significant factor in the extinction of the dinosaurs, has been estimated at 108 megatons, or Torino Scale 10. The impact which created the Barringer Crater and the Tunguska event in 1908 are both estimated to be in the 3–10 megaton range, corresponding to Torino Scale 8. The 2013 Chelyabinsk meteor had a total kinetic energy prior to impact of about 0.4 megatons, corresponding to Torino Scale 0. In all cases their impact probability was of course 1, as they actually hit Earth. As of May 2014, there are no known objects rated at a Torino Scale level greater than zero.
* * *
Eight small telescopes will scan the sky for any sign of faint objects that may pose a threat to the Earth. ATLAS will give up to three weeks’ warning of an impact, which is enough time to evacuate a large region, but probably not an entire country. The cost of our global insurance policy? One third of the annual wages of Manchester United striker Wayne Rooney. Such comparisons always sound childish of course; I’m well aware of how capitalism functions, and I know that Wayne Rooney generates income for the Manchester United corporation in excess of his wages. But the aim of this chapter is to argue that there is a flaw in the majestic edifice of human civilisation: our myopic and cavalier disregard for our long-term safety. In my view, the reason for the shortsighted approach is that nothing catastrophically bad has happened to humanity in recorded history that we haven’t inflicted upon ourselves, unless of course you believe in Noah’s Ark, and even that was presumably down to us because one assumes that God is usually quite a patient sort. One of the central themes of this book has been to argue that the human race is worth saving because we are a rare and infinitely beautiful natural phenomenon. One of the other themes is that we are commonly and paradoxically ingenious and stupid in equal measure. I do not personally think that there is anyone out there to save us, and so it follows that we will have to save ourselves; at least, that would seem to me to be a good working assumption. This is why I don’t feel naïve, idealistic or like a particularly radical member of the Student Union in a Che Guevara T-Shirt when I ask the question ‘Is it reasonable to spend less on asteroid defence than on a footballer’s annual salary?’ When I look in the mirror and think about that, my face assumes an interesting shape – you should try it.
NASA is working hard in the face of apathy to do something to close the gap between the capabilities of the dinosaurs and us. Twenty metres beneath the surface of the Atlantic Ocean, 8 kilometres off the coast of Key Largo, Florida, is the Aquarius Reef Base. Originally constructed as an underwater research habitat to study coral reefs, it is used by NASA to train astronauts for future long-duration space missions. The base allows for saturation diving, which greatly increases the length of time a researcher can spend exploring the reefs. On a normal scuba dive, a diver can spend a maximum of 80 minutes at a depth of 20 metres without having to go through decompression. The diver can remain at this pressure for several weeks, however, as long as they decompress when they return to the surface – a process that takes almost a day. Since the air pressure inside Aquarius is the same as the pressure outside in the water, researchers living inside the base can spend many hours a day exploring the sea bed using standard scuba equipment, but with the important caveat that they cannot return to the surface a few metres above their heads. If anything goes wrong, they must return to Aquarius and deal with the problem inside the base. For all practical purposes, therefore, they are isolated; it’s not possible to panic or simply loose patience and return to civilisation above. This is why NASA uses the Aquarius base to train astronauts to work in a hostile environment and test their psychological suitability for long-duration space missions.
Filming inside Aquarius was a personal highlight of Human Universe. We didn’t want to have to decompress of course, so we had a strict time limit of 100 minutes inside the base spread over two dives. The ex-US Navy diver in charge of our dive was wonderfully clear as far as timings were concerned. ‘If I say leave, you don’t smile and take one more shot – you leave! Otherwise you stay, for a long time. Your choice. I know you media types.’ Aquarius has the look and feel of a spacecraft from a science fiction film. There are six bunk beds piled three-high at one end, and a galley area complete with microwave and sink at the other. In between, there are control panels, some books on marine life, and a laptop computer station. Above the table, there is a single round window looking out across the reef. Through an air-lock-style exit, there is a dive platform with access to the scuba tanks and the open sea. NASA’s Extreme Environment Mission Operations (NEEMO) team had just completed a nine-day mission when we arrived. Led by Akihiko Hoshide of the Japanese Aerospace Exploration Agency, the mission was part of the long-term goal of landing astronauts on an asteroid, and developing the capability to deflect one, should the need arise. There are strong scientific and commercial reasons for exploring asteroids: they are pristine objects that will allow us to better understand the formation of our solar system over 4.5 billion years ago, and rich in precious metals precisely because they are pristine. On Earth, heavy metals such as palladium, rhodium and gold migrated into the Earth’s core, leaving the accessible crust depleted. Asteroids are too small to have separated in this way, leaving the primordial abundances of these valuable metals untouched and accessible.
Whether for commercial, scientific or practical reasons, learning how to land on asteroids, exploit their resources and manipulate their orbits is clearly an eminently sensible thing to do. And make no mistake, we will have to move one at some point.
SEEING THE FUTURE
In the year 35,000 CE the red dwarf Ross 248 will approach the solar system at a minimum distance of 3.024 lig
ht years, making it the closest star to the Sun. Nine thousand years later it will have passed us by, ceding the title of nearest neighbour to Proxima Centauri once again. Coincidently, in 40,176 years, Voyager 2 will pass Ross 248 at a distance of 1.76 light years. We know this because we can predict the future.
We’ve encountered Newton’s laws several times in this book. In Chapter 3 we used them to calculate the velocity of the International Space Station in a circular orbit around the Earth. At a distance r from the centre of the Earth, the velocity v is
Let’s look at this equation in a different way by rewriting it as
Here, we’ve used the notation of calculus. That may strike fear into your heart if you haven’t done any mathematics since school, but don’t worry. All we need to know is the meaning of the symbol
In words, this denotes the rate of change of the position of the space station with respect to time, otherwise known as its velocity v. You have an intuitive feel for this even if you’ve never done any mathematics. If you get into your car and drive it away from your house in a straight line at a velocity of 30 kilometres per hour, then in one hour you will be at a position 30 kilometres away from your house in the direction in which you drove the car. The equation is telling us what the position of the Space Station will be at some point later in time, given knowledge of where it is and how it is moving in the present. It predicts the future. This sort of equation is known as a differential equation. In Chapter 4 we wrote down the ‘rules of the game’ – Einstein’s General Theory of Relativity and the Standard Model of particle physics. The notation is a little more complicated, but in the Standard Model you’ll notice the symbols Dµ and δµ, which are more complicated versions of
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