THE ASTEROID BELT
In October of 2017 a random object – Oumuamua – cruised into our interplanetary neighborhood, and with the coincidence of the Sun’s gravity it made a last minute course correction, slingshotting itself back out into deep space. The whole incident took place so quickly that astronomers only noticed the situation when the asteroid was speeding away from Earth’s orbit at high speed. An asteroid moves with an average speed of 25 kilometers per second, so it should be no closer to the Earth than 464,000 kilometers.
Oumuamua is the first interstellar object detected passing through the Solar System. Formally designated 1I/2017 U1, it was discovered by Robert Weryk using the Pan-STARRS telescope at Haleakala Observatory, on 19 October 2017, 40 days after it passed its closest point to the Sun. When first seen, it was about 33,000,000 km (21,000,000 mi; 0.22 AU) from Earth (about 85 times as far away as the Moon), and already heading away from the Sun. We should consider ourselves as very lucky.
The name Oumuamua comes from Hawaiian ʻoumuamua, meaning ‘scout’ (from ʻou, meaning ‘reach out for’, and mua, reduplicated for emphasis, meaning ‘first, in advance of’), and reflects the way this object is like a scout or messenger sent from the distant past to reach out to humanity.
There are many other asteroids in The Asteroid Belt, a circumstellar disc in the Solar System located roughly between the orbits of the planets Mars and Jupiter. It is occupied by numerous irregularly shaped bodies called asteroids or minor planets. The asteroid belt is also termed the main asteroid belt or main belt to distinguish it from other asteroid populations in the Solar System such as near-Earth asteroids and trojan asteroids. About half the mass of the belt is contained in the four largest asteroids: Ceres, Vesta, Pallas, and Hygiea. The total mass of the asteroid belt is approximately 4% that of the Moon, or 22% that of Pluto, and roughly twice that of Pluto’s moon Charon with a diameter of 1200 km.
The high population of the asteroid belt makes for a very active environment, where collisions between asteroids occur frequently on astronomical time scales and thus there are a few asteroids that currently are known to have a low probability of hitting Earth in tens to hundreds of years. For example, one of the highest probabilities currently is an approximately 37 meter diameter asteroid called 2000 SG344 that has a 1 in 1100 chance of impact in 2071.
What is an existential risk?
An existential risk is one that threatens the entire future of humanity. More specifically, existential risks are those that threaten the extinction of Earth-originating intelligent life or the permanent and drastic destruction of its potential for desirable future development. No existential catastrophe has ever occurred. Human extinction would be an existential catastrophe if it happens before the heat death of the universe or before our potential for creating value has been fully realized. Some scenarios in which humanity survives would also be existential catastrophes if they involve a permanent and drastic destruction of humanity’s future potential – something that is to humankind what a lifetime prison sentence or severe brain damage is to an individual.
Humanity, in this context, does not mean “the biological species Homo sapiens”.
If we humans were to evolve into another species, or merge or replace ourselves with intelligent machines, this would not necessarily mean that an existential catastrophe had occurred — although it might if the quality of life enjoyed by those new life forms turns out to be far inferior to that enjoyed by humans.
Excerpt by Nick Bostrom, Existential Risk Organisation
Usually, as more observations are obtained, the impact probability will drop to 0; in other words even the NASA does not know when an asteroid will hit the Earth. The JPL Jet Propulsion labratory keeps an online list of all asteroids with any probability of hitting Earth. The big uncertainty is that we haven’t discovered most of near Earth asteroids yet, so we don’t know if they are on a collision course with Earth, which is why finding and tracking them is the most crucial step.
The Moon is a ball of left-over debris from a cosmic collision that took place more than four billion years ago. A Mars-sized asteroid – one of the countless planetesimals that were frantically churning our solar system into existence – hit the infant Earth, bequeathing it a very large natural satellite.
— Seth Shostak
Intrigued by this subject? Listen to Josh Clark on The End of the World where he takes your ears on an interstellar cinematorgraphic journey for the curious astronomical philosopher.
“There’s a concept called the Fermi paradox that asks where all the aliens are. Because the universe is so amazingly old and so astoundingly vast, intelligent life should have evolved perhaps trillions of times by now. At this point, the universe should be so teeming with intelligent civilizations that Earth should be fully colonized by aliens. In other words, we should be as sure that there is other intelligent life in the universe as we’re sure there are people living in Denmark. And yet, all of our searches for signs of intelligence have come up empty handed – we appear to be the only intelligent life in the whole wide universe. This is very weird. A rainbow of explanations have been developed over the years to make sense of the cosmic emptiness we see: from the idea that we are being kept in a zoo to the suggestion that the aliens have gone post-biological – loaded themselves into digital formats – and are hibernating until the universe cools down so the computers that run them can process information efficiently. But as far out as some answers to the Fermi paradox are, perhaps the strangest one of all is that we really are alone.”
If you want a more indepth podcast to the Fermi Paradox, listen to Dr. Anders Sandberg on what if we ended ageing, solar flares and the annual risk of nuclear war on the 80,000 Hours Podcast with Rob Wiblin.
More sources for Education
Anders Sandberg, Oxford University philosopher and co-creator of the Aestivation hypothesis
Who is Anders Sandberg?
Seth Shostak, director of SETI
Toby Ord, Oxford University philosopher
Future of Humanity Institute
Podcasts for further education
80,000 Hours Podcast
80,000 Hours Podcast
The End of the World Podcast
The End of the World
Future of Life Podcast
Existential Hope in 2019