Human Universe (28 page)

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.

In the year 35,000
CE
the red dwarf Ross 248 will approach the solar system at a minimum distance of 3.024 light 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
D
_µ
and
δ
_µ
, which are more complicated versions of

In Einstein’s equations, there are also these so-called derivatives hidden away in the compact mathematical notation. The known fundamental laws of physics all function in this way. Given knowledge of how some system or collection of natural objects is behaving
now
, we can compute what they will be doing at some time in the future. The system in question may be a solar system, a collection of atoms and molecules, or the weather. There are practical limitations, of course, and the weather forecast is a good example. Earth’s climate system is very complicated, with many hundreds of thousands of variables. Ocean currents in the Pacific might affect future rainfall in Oldham, and so long-term forecasting of local weather conditions comes with increased uncertainty.

People do of course make statements, often based on human experience rather than science, which are more likely to be right than wrong. Red sky at night, Shepherd’s delight. Red sky in the morning, Shepherd’s warning. This is often true in countries like the UK whose weather is dominated by westerly winds, because a red sunset is usually a sign of high pressure to the west, which is associated with fine weather. But if you’re doing well in a statistically significant sense using ‘folklore’ or ‘ancient wisdom’, it’s because the patterns and regularities you are using to make your predictions emerge from underlying physical laws, which are described by differential equations. The laws of physics in essence reflect the underlying simplicity of nature and the regularity with which it behaves. They are not magic. We can describe the natural world using mathematics
because
it is regular and behaves consistently. It is my opinion that we
must
observe a universe that behaves in a regular and consistent way because such behaviour is necessary for complex structures like brains to evolve. A universe of anarchy, with subatomic particles interacting without some sort of framework or rules, would surely not support life, or indeed any structures at all. This is known as a selection effect. We observe a universe whose behaviour can be described by a limited set of differential equations because we wouldn’t exist if it were not so. This is my opinion, and there are scientists and philosophers who might disagree. It could be the case that there is no simple underlying framework to the universe, and our success to date has deceived us. Or perhaps the ultimate laws are and will forever remain beyond human understanding. We might simply not be smart enough to figure them out. There are also systems that cannot be described using differential equations. The patterns generated in Conway’s Game of Life are an example, where algorithmic rules are used to generate complex patterns and even computing devices such as Turing machines. But what can be said with certainty is that, as far as we can tell, the natural world does behave in a way that is amenable to a description based on the differential equations of physics, and these allow us to predict the future, given knowledge of the present. This is why our asteroid defence system will work if we make enough high-precision observations of the sky. Sort of.