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Spaceguard Revisted - Arthur C. Clarke

SPACEGUARD REVISITED
        
Convocation Address
        
by
        
Sir Arthur C Clarke, Kt., CBE
        
Chancellor, University of Moratuwa, Sri Lanka
        
26 May 1998
     
Less than four years ago, in October 1994, I devoted my Convocation
Address to something which probably few people had ever worried about - 
the danger to our planet of impacts from space. Well, during those four 
years so much has happened that I make no apologies for returning to 
the subject.

If you spend a few hours at night under a perfectly clear sky  -  
which, alas, I haven't done for years - you are almost certain to see a 
few meteors sliding silently  across the stars; there  are times, 
indeed, when you may see hundreds. One such occasion is due in November 
1999: a Space Shuttle launch has been rescheduled, and the owners of 
communications satellites are already rushing to take out insurance. 
For though that 'shining furrow', as Tennyson called it, is caused by 
an object not much larger than a pea burning up as it enters the 
atmosphere, that has enough energy to damage, or even destroy, delicate 
orbiting equipment costing hundreds of millions of dollars. Tennyson, 
who a century and a half ago saw 'the heavens filled with commerce' 
could never have imagined that one day this would be literally true.
        
Quite often, one of these cosmic fragments is large  enough to survive 
passage through the atmosphere, and falls to earth. We then call it a 
'meteorite'; the word 'meteor' applies merely to the streak of light 
across the sky.     
        
That meteorites did fall -  sometimes in large numbers over 
considerable areas - had been known from time immemorial; indeed, it 
has been suggested that they were the only source of iron for early 
man. Yet two hundred years ago, in what has been called the Age of 
Enlightenment, there was great scepticism about their existence. Thomas 
Jefferson, widely considered the most brilliant President ever to sit 
in the White House, once remarked  after hearing that a couple of 
academic gentlemen had witnessed a shower of meteorites: "I would 
rather believe that two Yankee professors lied, than that stones fell 
from the sky." Well, now we know that mountains can fall from the sky. 

The evidence is overwhelming, yet only in  the  last  few decades has 
this been accepted: as someone once said: "The obvious we see 
eventually."
        
Perhaps the best example of this phenomenon is the famous Meteor Crater 
in Arizona - a huge hole in the ground more than a kilometre across. 
Despite the perfectly accurate name that the locals had given to it, 
for years most geologists argued that the crater was home-grown - some 
kind of volcanic formation! Now we know that it was produced by the 
impact some 50,000 years ago of a nickel-iron  mass about as large as 
this building. Once they removed their  mental  blindfolds, geologists 
started finding impact craters all over the world. About two hundred 
have now been identified, and there must be many more hidden in the 
ocean depths. We live in a very dangerous neighborhood: what has 
happened countless times in the past will, inevitably, occur again 
in the future.

What did most to focus the attention of the scientific - and 
non-scientific - community on this fact was a paper published in 1980 
by the American physicist Luis Alvarez and his geologist son Walter, 
suggesting  that the extinction of the dinosaurs was linked with the 
impact of an asteroid on Earth, about 65 million years ago*. 
------------------
* Luis was a good friend of mine, and I dedicated my 1963 novel Glide 
Path  to him. This work of barely disguised  fiction was based  on my 
experiences as an RAF officer when I took  over the GCA (Ground Control 
Approach) radar blind-landing  system  which 'Luie' had invented at the 
Massachusetts Institute of Technology. The  main  protagonist was 
modelled on him, and I am  very happy that  my  prediction  of his 
Nobel Prize came true  a  few years later. 
--------------------

The word 'asteroid' is unfortunate, because it  means 'small star' - 
and asteroids are in fact only small planets, most of  them  between 
Mars and Jupiter. The largest, Ceres, is  just under a thousand 
kilometres across, but they come in  all sizes down to ones that would 
sit comfortably on the Galle Face Green (what there is left of it.) So 
where one draws the line  between meteorites and asteroids is a matter 
of definition; they all bits of debris left over from the formation of 
the Solar System.
        
And so are comets, which are enormously larger but no heavier than 
asteroids, since they are almost entirely clouds of extremely thin gas, 
surrounding a small, solid nucleus. When, after many trips round the 
sun, all its volatile material has boiled off into space, only this 
core is left - and the comet becomes a normal asteroid.
        
I am proud to say that the International Astronomical Union, which is 
in charge of such matters, recently named  an asteroid (previously 
known only by a number, 4923) after me. It's about ten kilometres in 
diameter, and spends most of its time near the orbit of Mars, so I'm 
afraid its climate is rather chilly. The IAU apologised to me because 
Number 2001 was no longer available. Apparently it had been allocated 
several years ago, to somebody named A. Einstein.  
        
As far as the resulting damage to planet Earth was concerned, it would 
not make the slightest difference whether the impactor was a comet or 
an asteroid. However, because it is such an impressive astronomical 
object, we could see a  comet months before it hit. But an asteroid 
might give only two minute's warning, when the sky suddenly exploded... 
     
This happened over a remote part of Siberia in 1908. Luckily, though  a 
huge area of forest was devastated, there was no loss of human life.
        
There have been several other major events since then, again in 
uninhabited  areas, and in 1972 there was a hair-raising near-miss. On 
10 August, a large meteorite streaked half way across the United States 
and was seen not only by thousands of people, but recorded by many 
amateur photographers. It came within a mere 58 kilometres of ground 
level; had its  trajectory been slightly different, some American city 
might have emulated Hiroshima. 
        
I'm  not sure if this provided any inspiration for my novel Rendezous 
with Rama, which opened with the destruction of Northern Italy by 
asteroid impact in the year 2077. This disaster resulted in the 
establishment of a warning system, to which I gave the name - 
SPACEGUARD. Well, fact has followed fiction. When the U.S. House of 
Representatives asked NASA to study the problem, I was delighted when 
the resulting 1992 report was entitled THE SPACEGUARD SURVEY, with due 
acknowledgement. 
        
That same year, a senior editor of TIME wrote to me saying that though 
the magazine  had never deliberately published  fiction, they'd like me 
to write a short story for a special issue. The result was The Hammer 
of God, in which I attempted to answer the question: what could we do 
to save ourselves if we see a killer rock headed this way?
        
The novel-length version of The Hammer of God  appeared in 1993 - and 
just one year later, the whole world had a grandstand view of the most 
spectacular collision ever observed in our Solar System. The impact of 
Comet Shoemaker-Levy 9 on Jupiter in July 1994 made holes in the giant 
planet's atmosphere larger than the Earth; they could be seen even in 
the smallest telescope, and the after-effects lingered for months.
        
Only a few weeks ago, there was a great deal of alarm when the initial 
orbit calculated for the newly-discovered asteroid 1997 XF11 suggested 
that it might collide with Earth in the year 2028. Luckily, after a 
hunt through the thousands of photographic plates collected by 
astronomers over many decades, an earlier image of XF11 was discovered. 
This made it possible to compute a much more accurate orbit, and we now 
know that there is  no danger from this particular asteroid - at least 
for millions of years!
        
This rather embarrassing affair - the correction came only a day after 
the initial report - has triggered a major debate in the astronomical 
community. A protocol is now being drawn up to reduce the chance of any 
premature and perhaps inacurate announcement. And I am happy to say 
that NASA is now in the process of establishing a new office to deal 
with the  problem, with  an initial annual budget of $3,000,000.    
        
Among the members of NASA's SPACEGUARD Committee is my old friend the 
Dutch-American astronomer Tom Gehrels, one of the world's leading 
experts on asteroids. He has visited Sri Lanka on several occasions, 
hoping to establish an observatory here  - so far without success, 
because of a deplorable lack of interest in astronomy (as opposed to 
astrology!)      
        
This situation, I hope, may be rectified now that the Japanese  
Government has made an extraordinarily generous gift of a half-million 
dollar observatory-class telescope, currently located at the Arthur 
Clarke Centre. Although this is far from  being an ideal location, the 
best observing sites are currently inaccessible and good work can still 
be done at Moratuwa - if we can find experienced and enthusiastic 
staff. I might add that most comets and many asteroids are discovered 
by amateurs working with telescopes considerably smaller than the one 
we now possess.
        
Some might argue that, in a world already nervous about global warming, 
poisoned oceans, DIY nuclear bombs,  etc.  etc., any discussion of 
protection from asteroids amd comets is a massive exercise in 
irrelevancy. Yet there is much that can - and should - be done, as is 
proved by the current intense  debate among astronomers, space 
scientists, and under-employed Star Warriors looking for new targets. 

It is an old idea - going back at least to  Andre  Maurois' "The War 
Against The Moon" (1927) - that only a threat  from beyond the Earth 
could unify the quarrelsome human species. So it may indeed be a stroke 
of luck that such a threat has been discovered, at just the period in 
history when we can devise technologies to deal with it. 
        
Although some suggested cures may sound worse than the disease (Dr 
Edward Teller has proposed a bodyguard of orbiting H-bombs) there are 
several plausible  alternatives. They all depend on the length of the 
warning time available. 
        
Of the many defences proposed, the most elegant (and environmentally 
friendly!) one is to rendezvous with any asteroid on an orbit liable to 
impact Earth, and to persuade it to make a slight change of course. If 
there was sufficient warning time, only a modest amount of rocket 
propulsion would be necessary. This was the scenario I developed in The 
Hammer of God, which was later optioned by a promising young 
movie-maker named Steven Spielberg. I don't know how much of my story 
he has used, but I have a double interest in Deep Impact, as he is 
calling the film. The role of the first black President of the United 
States is played by Morgan Freeman, now considered by many to be the 
finest actor in America. Well, Morgan has just optioned my own 
Rendezvous with Rama, which started the whole SPACEGUARD business. I 
can't wait... 
     
Meanwhile SPACEGUARD Foundations have been set up in the UK, the US  
and Australia, to persuade goverments to fund a  survey which would, 
for the first time, give us some idea of the real extent of the danger. 
At the moment, we probably do not know even one tenth of the NEO's - 
Near Earth Objects - which must exist.
        
In one of his last books, Carl Sagan pointed out that no really 
long-lived civilization could survive unless it develops space travel, 
because major asteroid impacts will be inevitable in any solar system 
over the course of millennia. Larry  Niven summed up the situation with 
the memorable phrase: "The dinosaurs became extinct because they didn't 
have a space programme." And we will deserve to become extinct, if we 
don't have one.