Preserving Earth Life

Opened in 2008, the Svalbard Global Seed Vault, located on the Norwegian island of Spitsbergen far north of the Arctic Circle, is the world's largest store of seeds. It was built as a way to preserve seeds from global catastrophes, and is a backup for the hundreds of other seed vaults around the world, some of which have already been lost due to war and natural disasters.

The modest entrance to the Svalbard Global Seed Vault on the Norwegian island of Spitsbergen. The actual vaults are deep within the mountain. The vault holds close to a million samples of seeds.

The seeds are stored in vaults deep in the permafrost, which helps to keep the seeds cold enough for preservation. But despite being built to protect seeds from potential disasters such as climate change, climate change is already threatening the vault itself. The Norwegian government is having to make modifications just a decade after it was built. This is an ominous sign that whatever we do to preserve life and all that we have achieved on our planet (the Arctic World Archive opened nearby in 2017 as a data and knowledge store) it is going to be a losing battle.

We need to think bigger if we are to protect life and our knowledge and achievements from oblivion.

The colder the better is the key to very long term preservation, and natural environments that offer such low temperatures for 'free' are highly abundant within our Solar-System.

Inner Solar-System Vaults

The Moon has areas of permanent shadow at its poles, and a NASA instrument on board India's Chandrayaan-1 probe confirmed the presence of water ice in those regions. Those areas, as well as being ideal locations for human colonies, would make excellent locations for preservation vaults. The close proximity to Earth would make the vaults relatively easy to access if/when Earth's climate causes major problems that require access.

A vault so close to Earth would also be vital if our current civilisation is wiped out by a catastrophic event, such as a nuclear war or an asteroid impact. It could take centuries, even millennia, for a new civilisation to advance to the point where space travel is possible.

On Mercury, the closest planet to the sun, there are also areas on the planet's surface that are in permanent shadow in craters at its north pole. The Messenger probe that orbited Mercury between 2011 and 2015 discovered billions of tonnes of water ice in those areas. It proves that preservation vaults can be built on bodies very close to a star, providing there is no atmosphere to distribute heat to those areas of permanent shadow.

The planet Mercury. Despite being so close to the sun the planet still has a large amount of water ice on its surface. The ice is located in craters in areas of permanent shade. It would be possible to construct preservation vaults that would provide protection for life and knowledge for millions of years.

A vault on Mercury would only prove sensible if sizeable human colonies were to be established there, which is unlikely. Venturing so close to the sun is not something that I predict will happen for humans. Perhaps colonies in the clouds of Venus will be as as near as we will get.

Human colonisation of Mars is almost certain to happen this century. There is abundant ice on Mars, which will be heavily exploited by the colonists to provide water, oxygen and fuel. Those colonists should create preservation vaults as a matter of urgency. It should be one of their top priorities once the essential activities for their survival are established and running smoothly. Areas within the ice mines could be designated for such a purpose.

Outer Solar-System Vaults

There are many large bodies in the Kuiper Belt, such as Eris, Haumea and Makemake, that would be worthy locations for preservation vaults, and there will be hundreds more waiting to be discovered. Those larger bodies are more useful that the millions of small bodies out there, if only because they provide at least a useful level of gravity, even if it is only around 5 percent that of Earth.

The best known example of a large object in that region is Pluto. The mountains and crevasses of that dwarf planet, which can rise over six kilometres in height, are examples of places in the outer Solar-System that would be ideal locations for such vaults.

The surface of the dwarf planet Pluto. The Al-Idrisi mountains shown consist almost entirely of water ice, and the plains are mostly nitrogen ice. With a mean surface temperature of -229 Celcius it would be an ideal place for preserving life and knowledge for many hundreds of millions of years at least.

Even on the surface of Pluto the temperature is low enough to provide an excellent level of preservation, but vaults should still be constructed deep into the ice to protect against meteorites, and eventually from theft. Building inside mountains means access to the vaults can be horizontal, which would ease construction. Several preservation vaults should be constructed, each on a different dwarf planet and on radically different orbits.

Interstellar Vaults

Ultimately the sun will flare up and expand, consuming the inner Solar-System vaults. The outer Solar-System will suffer too, with the extra heat threatening the stability of vaults in that region. A truly long-lasting vault, that could survive for billions of years, should not be in the Solar-System at all.

The interstellar void between stars is the coldest and most benign area in the galaxy. It is not completely empty, with rogue planets and smaller bodies drifting for aeons out there in the frigid darkness. Finding one is not easy, but such a world is an ideal place to build a safe and secure preservation vault (and surprisingly, it would also be suitable for an interstellar human colony).

Instead of hunting for interstellar objects on which to construct the vaults it would be easier to create our own. By redirecting some of the smaller Oort cloud objects away from the Solar-System (or even constructing our own purpose-built station for the vault) we would have easily available bodies on which to preserve whatever we wish. Ideally there should be human colonies nearby.

Although in the Kuiper Belt, Arrokoth (pictured here) is a good example of the kind of small object we can find in the Oort Cloud. At just under 20 kilometres in diameter, a body like this could host a preservation vault and be redirected onto an interstellar course to hide between the stars.

It may sound almost impossible, and undesirable, for a human colony to be located away from the obvious benefits of a star, but it is not so. My 2018 article 'Secret Colonies Between the Stars' explains why not, and gives reasons why such colonies would actually be an essential part of our colonisation efforts, and even on which the ultimate survival of our species could well depend.

Where ever we humans go, from the inner and outer Solar-System to interstellar space and other star-systems, we should construct life and knowledge vaults to preserve as much of what has been achieved on Earth as possible. It should be an essential part of colony building wherever that may be. In billions of years time it will then be possible for our very distant descendants to benefit from our endeavours, even if it is just to know where all that they take for granted actually comes from.

Hopefully they'll be able to enjoy bread just as we do today.

Living Inside Asteroids

For humans to live long-term in space we would need a healthy environment. This would mean somewhere spacious, with plenty of the comforts we find on Earth. And most importantly, we would need gravity, or at least a simulation of it.

Large space stations could be built with all of the above. With a large enough diameter they could be spun at less than two revolutions per minute, which would eliminate the uncomfortable symptoms of the Coriolis effect that would be experienced at the higher revolutions of a small rotating space station. Due to the huge amounts of material needed for construction of such stations, and the immense cost of launching it from Earth, the materials to construct the space stations would realistically have to be mined from asteroids.

A large diameter space station under construction in the Asteroid Belt. A single large asteroid will provide more than enough material for the construction of the station. Concept by Deep Space Industries.

Asteroid mining will not only provide the huge amount of construction material necessary for space habitats. If the asteroids are mined in a certain way, making large cylindrical chambers through the asteroid's centre of rotation, we could then convert the chambers into living spaces. Once mining is concluded the rotation of the asteroid could be altered until a high-enough centrifugal force provides enough artificial gravity comfortable for humans on the chambers' outer walls.

Such chambers, several kilometres in diameter, could well provide what may become the safest and most comfortable human living spaces away from the Earth.

Of course, the idea of hollowing out space inside an asteroid is not a new one.

This image was created in the 1960s by Roy Scarfo when the exploration and colonisation of the asteroid belt was being researched by Dandridge M Cole.

In the 1960s Dandridge M Cole, an aerospace engineer and futurist, was one of the first to propose hollowing out an asteroid and spinning it on its long axis to simulate gravity. Illustrated above, he envisaged a large single void within the asteroid with fields, lakes and villages. Sunlight would be reflected into the interior using mirrors. It would be a spacious and comfortable environment.

It's an impressive concept, but there are numerous problems with it, and not least the idea of a single huge chamber and relatively thin wall. It would make the asteroid habitat vulnerable to complete decompression if the wall was compromised in some way. If the rotation provided one gee of gravity the forces on the wall, especially at the asteroid's equator, would cause it to fly apart as soon as any cracks or flaws developed.

The very green and pleasant interior of Dandridge's asteroid habitat concept

It would be far better to cut several cylindrical voids, and have the outer walls very thick - several kilometres at least, depending on the overall size of the asteroid. Each chamber would be connected to the next, but with the ability to quickly seal off a particular chamber if it was compromised and at risk of decompression, or indeed some other dangerous event. Those living in the effected chamber could easily be evacuated to another chamber, making such asteroid habitats safe and with plenty of redundancy.

Once the chambers have been excavated the asteroid's speed of rotation can be increased slowly, until the right level of simulated gravity is reached. To generate an equivalent of one gee (the same as what we experience on Earth) the rotation speed would be quite substantial, and it would mean that, at the very least, loose boulders and dust would be thrown off the surface of the asteroid. It would also put considerable stress on the outer surface, which would rule out low density asteroids due to the high risk of instability.

A natural habitat for Earth life, many kilometres in diameter, created inside a hollowed out cylindrical chamber within an asteroid. Typically there would be a few such chambers. All would be linked but each could be sealed off should a disaster occur, which would protect the other chambers.

A supporting series of collars around the equatorial region of of the asteroid would negate many of the issues that such a high centripetal force would cause. It would be a huge construction task to build such collars, but no more than the excavation of the chambers themselves. Of course, the excavated material would provide everything required to build the collars, each of which could be many kilometres in width. They would be held in place by deep supports.

Visiting spacecraft would using large docking areas at the poles of the asteroid, situated at each end of the axis of rotation. People and cargo would then be transported through the asteroid along the axis of rotation. Essentially there would be zero gravity in this area. When the destination chamber is reached the visitors and cargo would be delivered to the surface using elevators. People descending in these would experience a steadily increasing sensation of weight as they approached the surface.

A diagram showing how the interior of a rotating asteroid colony could be divided up into separate chambers. This would provide higher levels of safety (colonists could be evacuated to another chamber if their own is compromised), and more structural integrity than a single large chamber.

It's likely that people arriving at the asteroid will have spent many months travelling in zero gravity so acclimatisation areas at the regular points down to the surface should be built to allow people to adapt gently to the full gravity of the facility.

As well as fairly static colonies inside asteroids in the Asteroid Belt, or in the Trojans, asteroids that are on highly elliptical orbits - that head in to the inner Solar-System and then out beyond the orbits of Neptune and Uranus - would make very useful passenger ships. As the asteroid gets close to Earth (and the probable large colonies on the Moon and Mars) passengers who need to travel to the outer Solar-System could rendezvous with it. They could then spend the next couple of years living in comfort in relatively Earth-like conditions as the asteroid's orbit takes them closer to their destination.

Ultimately, such asteroids could become our first interstellar star ships. They would make voyages lasting thousands of years, with a hundred generations or more of humans living out their lives in comfort until the asteroid is captured by the target star system. With the right energy generation technology such as nuclear fusion that could provide light and warmth during the interstellar period of the voyage, humans would have a relatively good chance of reaching their destination.

Converting asteroids into large human habitats, and then into interplanetary and interstellar spacecraft, seems to be a logical and necessary step as humans embark on colonisation beyond Earth, and it is likely to be an essential step towards securing the future of our species.

The vast resources and protection that such objects can provide must be utilised at the earliest opportunity.

Saving Planet Earth - Forever

Human-induced climate change is the biggest short term threat to our planet and our species. Neutralising that threat should be our top priority. But ultimately, the natural warming of our sun will change our climate to such a degree that one day the Earth will uninhabitable for even the hardiest and most basic life.

The warming of the sun is something that we can have no control over.

No matter how we balance our ecology with sustainable energy generation, recycling, pollution and population control, in a few hundred million years our world will warm up to a point that will render our species and all other higher life forms extinct. And a billion years after that the Earth will be nothing but a hot and sterile planet - wiped clean of billions of years of evolution, experience, culture and history. It will be a hellish world not unlike how Venus is at the moment.

This image of Venus, taken by Japan's Akatsuki probe, is how Earth could look in a few hundred million years time. The natural warming of the sun has caused the oceans to boil away, and the uncontrollable greenhouse effect that followed has rendered the planet uninhabitable. 

Earth, the cradle of our species and civilisation, will become a dead world. No matter how far humans have spread throughout the Solar-System and beyond, it would be a sad and poignant day when our planet of origin is finally abandoned by humanity to face its natural fate.

There are, however, things we could do to preserve our home world's habitability for much longer, and possibly forever:

1. Block Some of the Sunlight

There is a point between the Earth and the Sun known as a Lagrangian point (specifically L1 - there are four others). It is a stable point where the gravitational pull of the Earth cancels out that of the Sun. In other words, any small object positioned there will stay there, directly between the Earth and the Sun.

It is the ideal position to place a filter - something that can reduce the amount of light and energy from the Sun. Unfortunately L1 is 1.5 million kilometres away, which means the filter would need to cover tens of millions of square kilometres. This would be unfeasible for a single object which would need to be many thousand of kilometres in diameter, but a formation of very small spacecraft, each just a metre or so across, would be quite possible.

A swarm of hundreds of millions of smart probes positioned at the stable L1 point between the Earth and Sun would be able to filter out a few percent of the Sun's energy. This would stop global warming, allowing the reversal efforts on the Earth to have time to work. In the longer term this would allow the climate on Earth, and life, to be less affected by the gradual warming of the Sun.

The objects would need to be very light - just a couple of grams - and would consist of a very thin stretched panel to deflect sunlight. Each spacecraft would be intelligent enough to maintain its position within the formation, and use its panel as a solar-sail to move away from the Sun, and ion engines to move in other directions.

Such a swarm of spacecraft would need regular renewal as a certain number of them fail each day. Ideally a permanent production facility away from Earth would be needed, perhaps on the Moon, to enable a constant supply of replacements.

The swarm would only need to reduce the amount of energy reaching Earth by two or three percent to halt global warming. And it could even be used to cool certain areas of the Earth at crucial times, such as over the oceans to lower the intensity of hurricanes and typhoons, and even prevent them altogether.

2. Move Earth to a Higher Orbit

As the Sun slowly warms up the effectiveness of the filter at L1 would reduce. The next step is to alter the Earth's orbit, increasing its distance from the Sun. The most efficient way of doing this is to cause a relatively massive object, such as an asteroid, to repeatedly pass very close to our planet, pulling it into a slightly higher orbit each time.

The larger asteroids in the asteroid belt, such as Vesta or Pallas, would be ideal candidates, although changing their orbits, and directing them into the inner Solar-System on the correct course is a mammoth undertaking. It would take many millennia to get those objects on the right trajectory so that they pass by Earth at just the right distance to have the desired effect.

Vesta, one of the largest asteroids in the asteroid belt between Mars and Jupiter. Such an asteroid would be able to 'pull' Earth into a higher orbit around the Sun if it were sent on the correct trajectory to pass very close to Earth.

There is, of course, an immense risk to such a strategy. Any miscalculation could send the asteroid on a collision course with the Earth, or the Moon, which would be truly catastrophic. Fortunately the Sun's warming is a very slow and steady process, so as long as the L1 filter is in place we would have plenty of time to overcome the technical challenges and design in all the necessary safeguards.

Once the process has begun the asteroid would be directed to pass the Earth regularly, possibly every couple of centuries, to carefully nudge our planet's orbit away from the Sun. Our climate and the life it supports would remain stable and comfortable.

There is a limit to how far the Earth's orbit could be altered. We could only move our planet so far before we get too close to the orbit of Mars. We could, of course, start moving Mars as well, but then eventually the asteroid belt would become a hazard to both worlds (and Mars will be far too important to the humans living there to be placed in such danger). We would end up having to alter the orbits of all the significant bodies in the asteroid belt as well, which would then put at risk the colonies we will have set up on Jupiter's moons, or in the inner Solar-System. It would be an impossible task to manage.

3. Build a Shell Around Earth

As the Sun's relentless warming continues there is something else that we could do to further protect our climate: build a shell around the Earth. Just like altering Earth's orbit, this will be a massive undertaking, and one that could take millennia to build. But it is possible, and there will be plenty of time to complete it.

A huge amount of material will be needed, which would make mining it all from the Earth almost impossible. The Moon and the asteroid belt would be able to provide all the resources necessary. The supports would be built first, evenly placed around the whole planet. These would ideally rise up to the Karman line, the officially recognised edge of the atmosphere at an altitude of 100 kilometres.

The view from the Karman line, a hundred kilometres above the Earth's surface. The planet's protective shell would be built at this altitude.

Next the shell would be built, spreading out from each support until it joined together with other shell segments. On the inside surface of the shell there would be artificial lighting, powered initially by the Sun beyond. Once completed the shell would ensure that the intensity of light and energy reaching the Earth's surface is fully under our control. Excess heat would be radiated up the supports and out into space from the shell's outer surface. It's interesting, and even sad, to think that life on Earth would never again see the Sun, Moon or stars in the sky, but as the construction of the shell could take a hundred human generations or more, those alive to see the shell completed would not really have seen them and so would not miss the experience.

Having such a shell around the Earth would have other benefits besides climate control. It would provide another surface on which to construct manufacturing, accommodation and space launch facilities. It would be the idea place for astronomical research. Additional outer shells are likely to be constructed, with the spaces between the shells used for any number of functions. Such spaces could be hundreds of metres high in some cases, which could be pressurised and provide vast areas for agricultural activities that would cultivate and breed enough food to feed billions of people on Earth, and for export to colonies around the Solar-System.

After thousands of years of construction, millions, even billions, of humans and animals could end up living on the plains and cities constructed in those vast spaces between shells way above Earth's natural surface.

Eventually the very outer shell, one of hundreds, could have a diameter many thousands of kilometres greater than that of the Earth that is hidden and protected far below.

4. Move Earth to Another Star System

There will come a time, more than a billion years from now, when the Sun starts to swell. Slowly but surely it will expand and engulf the inner planets Mercury and Venus, and then, no more than five billion years from now, it will engulf the Earth, and possibly Mars, too. The magnificent multi-layered shell that we will have constructed around the Earth will no longer be enough protection. It will be vaporised along with our planet.

The inner Solar-System will have become a hellish place long before that. Without a protective shell, the Earth would become uninhabitable for humans in a couple of hundred million years. Within six hundred million years plant life would most likely die off completely bringing the food chain to a halt. And a hundred million years after that the oceans will have boiled away.

Within 200 million years we will need to be preparing for the next stage of Earth's survival. It will involve much more than just moving to a higher orbit in the outer Solar-System (although that could be an interim stage). We will need to move the Earth to another star system.

This would be a truly momentous task, but we would have millions of years to get the Earth and its all encompassing shells ready. A means of propulsion will need to be developed. It would have to be gentle, with a barely noticeable gee force, but able to be sustained for years due to the incredible mass it would need to move. Over many centuries the Earth's orbit would need to be changed to a more and more elliptical one, taking it far out to the orbits of the outer planets, and then back in to the inner Solar-System. Eventually, when the destination star has been chosen, the Earth can be directed on a course that would take it very close to the Sun.  With its propulsion system pushing as hard as it safely can, the Earth would head in to the inner Solar-System and sling-shot past the Sun, picking up enough extra velocity to escape from our planetary system and head out into interstellar space. At this point the Earth and its shell would be travelling at many hundreds of kilometres per second, and this would be maintained by the propulsion system until the planet left the influence of the Sun's gravity. The Earth and its shell would now essentially be a massive generation star ship: one with a huge amount of comfortable and well-protected living space for billions of people.

There would be many options with regard to the destination star, and the obvious choice would be a star very similar to the Sun, but younger. The disadvantage of that would be the need to move to another star system in a few billion years time. A better choice would be a different kind of star: a smaller and cooler star type that just happens to be the most common type of all - a red dwarf. Red dwarf stars are very stable and very long lived. At a minimum they can live ten times longer than the Sun, and many will exist in a stable condition for a trillion years or more - hundreds of times longer.

As red dwarf stars are much smaller and cooler than the Sun, the Earth would need to be in an orbit much closer to it to receive the same amount of energy that we do at the moment: so close that a year would last just a few days. Of course, Earth's extensive system of shells and energy generation would allow it to have a much more varied choice of orbits. If a red dwarf is chosen as the destination star there would be no need to move the Earth to another star system again, at least in any timescale that we could comprehend.

Earth, safe beneath its worn but still intact outer protective shell, arrives on in the region of a younger star after a voyage of many millennia across interstellar space

Once the Earth is settled and secure in its new star system humans would once again begin exploiting the local resources to enhance their home. More and more layers would be added to the shell, and over many thousands of years there would be tens of billions more people thriving up there. It's not inconceivable that one day the Earth would be no more than just a small part of a vast structure that has grown to something a hundred thousand kilometres in diameter - almost ten times that of the planet within. There's no reason why it could not keep growing and growing.

By this time, hundreds of millions of years from now, there will be other planets that have been terra-formed and had their own shells built to protect them. The Earth will be one of many highly protected planets hosting billions upon billions of humans. Some of those planets will be mobile and able to traverse the vast distances between stars, and some will even be capable of travelling the intergalactic voids between galaxies. Perhaps the Earth, with its ever deepening structure of shells, will become a legend amongst those intergalactic travellers: the unreachable source of all humanity where hundreds of billions still live out their lives.

Hundreds of million years from now there could be trillions of people spread throughout our galaxy, with billions more on their way to other galaxies, safely cocooned within planetary shells.

It's an incredible prospect, and an awe-inspiring concept. But it's not impossible. If this happens then the survival of our species will be secured for trillions of years.

Machines Meeting Machines

Most science fiction stories that feature alien encounters or visitations show biological creatures that have traveled vast distances. The more I think about it, and the more I read about it, the more I am convinced that this is unlikely to be the way we will eventually meet an extra-terrestrial intelligence.

Our first encounter with such an intelligence will almost certainly be with a machine.

Most people expect that the first encounter with an extra-terrestrial intelligence will be with a biological being, but this is highly unlikely

But why will that be?

Interstellar travel by biological creatures such as ourselves is difficult, costly, and fraught with danger. The food, water and air that's needed for such a journey has to be provided by the star-ship itself. This requires an incredibly complex and almost perfectly tuned biosphere which will need to function for at least a few centuries, and probably far longer. And the ship will need to be huge if it's to accommodate a large enough population to maintain genetic health and diversity.

Building such a star-ship is not impossible. The technical challenges are in no way insurmountable. But the political, emotional, and even ethical obstacles probably are. The world's governments would have to come together and cooperate to get such a project even started. All the military and economic conflicts would need to be resolved, and all the hate and suspicion of our cultural and religious differences transmuted into something positive, respectful and cooperative. And, of course, the general population (whose taxes would fund the venture) would need a lot of convincing as they and their descendants would not see any personal benefit from it.

It does not take much thought to realise that such cooperation goes against the most basic but intensely powerful instinct of any biological life-form: that of self-preservation. Such an instinct is generally beneficial,  but for an advanced civilisation such as ours it could, on a national scale, easily result in an endless series of territorial and ideological conflicts that consume our time and energy. One day the result of such squabbling is likely to result in another global war that could wipe out our species. It's ironic that the survival instinct that has served us well throughout our primitive history, allowing us to evolve into a creature of such high intelligence, could well end up destroying us completely.

Large interstellar spacecraft capable of supporting humans for generations are unlikely to be built until our territorial, political and religious differences on Earth are resolved

That survival instinct is not going to change. Cooperation between governments is not going to reach anywhere near the levels required to build human-crewed star-ships. But the development of crewless interstellar spacecraft requires no such cooperation. And neither does the development of the advanced artificial intelligence to run it. Individual nations, and even individual corporations, can certainly do that.

Because of this our interstellar exploration will almost certainly be conducted by machines. And those machines will contain within them a sophisticated artificial intelligence; one that is able to function autonomously for centuries. And it will be designed to be our ambassador should an advanced alien civilisation be encountered .

Our first encounter with extra-terrestrial intelligence will be with something artificial , rather than a biological life-form. 

And that will be the same for all intelligent extra-terrestrial civilisations. Highly intelligent machines will do the exploration. And due to the communication problems across the vast distances between star-systems those machines will be designed to deal with first contact situations. They will also be able to utilise the resources in the star-systems they visit, replacing and repairing themselves, and even improving their own design. My earlier article, 'Intelligent Machines Are Watching Earth', discusses the possibility that such machines are observing our planet right now.

Its not hard to imagine them setting up machine colonies and constructing more of their kind that will head off in new directions, greatly speeding up their exploration. New machine civilisations will be created. Entire planets could be engineered to be the new home worlds for such artificial creatures.

The home planet for an intelligent artificial species. Over millennia the entire planet has been engineered to accomodate such a species. It will be a highly efficient and sustainable machine civilisation.

It does seem to me that due to the relative ease of manufacturing and distributing intelligent machines across interstellar space, the most abundant form of intelligent life in the universe (if it can be called life) is artificial.

There will, of course, be some biological beings exploring interstellar space, probably on 'world ships': huge vessels, tens or even hundreds of kilometres in length. But they will be exceptionally rare. Due to basic and irrepressible instincts, almost all advanced biological civilisations will render themselves extinct within a few centuries of developing high technology. But many will have survived long enough to initiate interstellar exploration using intelligent machines. Some of those machines - those that are designed to manufacture copies of themselves and make improvements - will go on to establish themselves in other star-systems. Eons after the biological civilisations that first created them have died out, the machine civilisations will continue to thrive and explore.

One day one of our machines will meet one of those machines.

I hope our biological civilisation is still around to appreciate that moment.

Should All Interstellar Missions Be Silent?

The first detected interstellar object passed through the inner Solar-System last year, and is now heading away back to interstellar space. Named 'Oumuamua', the object, approximately 230 metres in length and around 30 metres wide, reached a speed of almost 88 kilometres per second at its closest approach to the sun.

Oumuamua: an interstellar object that passed through the inner Solar-System in 2017. It is potentially a camouflaged extraterrestrial embryo colonisation starship making use of our sun for a gravitational course correction.

There's a reasonable possibility that the object is artificial. It could be an interstellar colonisation mission that is using our sun to provide a gravitational  course correction, putting it on its final trajectory for its target star system, or setting itself up for another gravitational course correction in tens of thousand years time. And it could well have made some passive observations of our planet on the way through.

The object is too small to be a generation ship. A ship many times larger would be required to allow thousands of beings the chance to live and breed for many millennia as their voyage unfolds. But the ship is certainly large enough to be what is arguably a more efficient means of interstellar colonisation: an embryo ship. Such a ship would need to be much more advanced, requiring artificial wombs, and artificial 'parents' and educators. If Oumuamua is indeed such a vessel then it would be a remarkably complex technological marvel, and something worth pursuing when we have the means to do so.

On board an embryo star-ship a human colonisation crew is grown in artificial wombs

A lot of effort was made to detect signals from Oumuamua. None were detected. But why should any have been? Such an interstellar ship, with embryos only, would be fully automated, with no sentient crew (apart from perhaps an overseeing artificial intelligence). There would be little reason for the ship to make a transmission home, except during the safe interstellar phases of its voyage. Even if it did, it would be a very directed and focused transmission that would not hit our planet. And using stars such as our sun to provide course alterations would almost eliminate the need to use a means of propulsion, the emissions of which would be detectable, while transiting the system.

Maintaining a strict 'silent running' policy is essential for all pioneering interstellar missions. Only very targeted and rare encrypted transmissions to the home world should be made, and only when the ship is well away from possibly inhabited star systems. The rest of the time a starship should appear, apart from during the very closest of inspections, as a natural object. Any course corrections using a propulsion mechanism must only be made in interstellar space.

This seems to be the most sensible approach for us when we finally embark on colonisation missions to other star systems. And I would expect it's the approach taken by extraterrestrial civilisations that are already undertaking such voyages. That would certainly explain why we are not detecting any transmissions. Such strict controls are obviously being maintained during voyages, and when colonies are established. And such controls are no doubt being enforced on home worlds.

It's very likely that, at this point in time, our civilisation is one of the very few (even the only one) in our region of the galaxy allowing unregulated transmissions without considering how visible we are to civilisations in the surrounding star systems.

Listening for signals from extraterrestrial civilisations is a good idea. But is it wise to also transmit messages in the hope that one of them receives it? Perhaps we have not detected any civilisations because they have a good reason to keep quiet. Maybe we should, too...

This could possibly be to our advantage. It could act as a warning that our star system is home to a reckless species that does not care what it does, and who knows about it. It could make potential invaders think again and head for a quieter system.

Or more likely it could act as a sign that we are an undeveloped and ignorant species, unaware of the risks of attracting attention. We could be considered an easy target for eradication, and Earth as an easy project for redevelopment. Or we could simply be 'silenced' to prevent us bringing to this region the malevolence other civilisations fear.

We have only been transmitting radio signals for just over a century. That is not really enough time for any alien civilisation to analyse those signals and complete a voyage here. But there are already many star systems identified within a hundred light-years of our planet that could host life and even advanced civilisations. Our unfettered radio transmissions could have been detected decades ago.

If such a civilisation is advanced enough to already have starships constructed then it may not take much effort or time to prepare and direct one this way.

Extra-terrestrial visitors may well be friendly, but we should also be prepared for a hostile encounter

An interstellar ship or probe could be on its way to us right now. If it's able to reach speeds that are a significant percentage of the speed of light it could arrive by the turn of the century. We need to take seriously the possibility that an extraterrestrial civilisation has found us. 

They may be heading here right now.

It would be wise to prepare for an encounter with them within the lifetimes of those born today. We should hope that they are benevolent, and be ready to greet them as friends.

But we need to plan for the possibility that they are not.