If it hadn't been for either a comet or an asteroid colliding with planet Earth we would probably be sharing the land with Dinosaurs today. Those Dinosaurs were at the peak of the animal kingdom and its a moot point whether us Homo sapiens could have survived in combat with these armoured monsters which dominated the land, oceans and had achieved flight. When the first humans evolved their weapons were primitive and they could have been hunted for prey.
Science believes whatever struck Earth was so catastrophic that it sent the planet into a frigid winter that lasted for years. The dust in the atmosphere blocked out the suns heat and light and brought in an ice age that killed most animal and plant life. When sunlight returned and the ice melted it became the age of the marsupials - and the world we know today.
We are nervously aware that the Kuiper belt contains trillions of rocky objects left over from the formation of planets after the big bang and occasionally a space rock collides with Earth. In 2013 one measuring about twenty metres in size entered the atmosphere over Russia and damaged thousands of buildings and caused many injuries. That one escaped our vigilance and was a timely warning of an ever present danger.
NASA believes it has tracked ninety-five percent of all near Earth objects and has catalogued 18,300 space rocks of all sizes. Of these, eight hundred are a hundred and forty metres long - or bigger. What gives scientists sleepless nights is that other five percent - out there somewhere !
Our massive telescopes are very good at tracking objects in the night sky but the danger area is when objects approaching are masked by the sun and only appear in our vision when they suddenly appear on the day side, when sunlight is shining on Earth. That is when our reaction time to prevent a collision is desperately short.
Donald Trump is promising to activate greater efforts to give earlier warning of approaching space rocks, but he has also alarmed other countries by declaring that he intends to project the United States military into a space defence role. Space is protected by a widely signed moratorium which Trump proposes to set aside. That agreement forbids the use of space for the positioning of military hardware capable of waging war from above the countries on the Earth's surface.
The danger is that this will set off a space arms race. We know that many countries already have rocket trajectories aimed at the communication satellites circling this planet and in a war these would be the first target to achieve a communications blackout. Anything the United States does in space to track space rocks will be misinterpreted as having military overtones.
An undetected space rock hitting Earth would be catastrophic. It could deliver the type of destruction that wiped out the Dinosaurs, only this time the victims would be us. Given enough time warning we may be able to deflect a coming hit, but that depends on an effective early warning system being in place.
It is important that whatever early warning is planned is under the auspices of the United Nations and not controlled by any singular country. It is equally important that the space moratorium be honoured and Donald Trump persuaded to abandon his plan to put weapons in space. An arms race in space would be the ultimate act of stupidity likely to destroy the only place the human race can yet call " home " !
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