Scientists are still not certain if true artificial intelligence (AI) is possible, given the extreme complexity of the human brain. Thinking robots have nonetheless been a science fiction staple as long as the genre has existed, and the idea of mechanical beings has fascinated inventors and futurists since time immemorial. Artificial intelligence (AI) differs from many of the aforementioned technologies because its underlying laws—the fundamentals of intelligence and consciousness—are poorly understood.

The most important figure in the history of computing was Alan Turing (1912-1954), who pioneered the prototype for all modern digital computers with his Turing machine capable of following a rigorous set of instructions to decode the Enigma machine during the Second World War. The Turing test evaluates robotic intelligence by having the computer interact with a human for several minutes to see if the human can reliably determine whether they are talking to a computer or another human. As of 2008, no computer has managed to pass the test. Many scientists believe that computers will never truly think because they cannot understand the meaning or semantics of words; they can only ever learn the syntax of language. The Chinese room test suggests that computers may be able to communicate by following a series of rules without ever actually comprehending the inputs or their own output, like a person who doesn’t understand Chinese blindly manipulating symbols to produce the correct characters without any real understanding.

The top-down, or “formulist,” approach involves programming rules of common sense and pattern recognition into software. There have been significant difficulties in this approach because biological minds process so much information subconsciously. This type of robot excels in specific rule-based contexts like playing chess, but struggles with navigating even simple terrain or understanding language. Many companies lose credibility by failing to achieve projected milestones in developing advanced robots using this method, although researchers in the field are still optimistic. There is a huge market for computers with even near-human levels of intelligence, and they will undoubtedly impact the job sector when they are invented. The bottom-up approach in robotics aims to mimic human thought processes through trial and error. Neural networks learn and develop in response to information and stimuli, but are currently only in the early stages of development. Although computers are extremely competent in dealing with difficult tasks like advanced mathematics, they struggle with even the simplest daily tasks. A synthesis between bottom-up and top-down approaches may soon cause a great leap forward in robotics.

In humans, emotions are an evolutionary adaptation to aid survival, allowing individuals to navigate social situations, avoid danger, and make decisions. Advanced robots might have systems that release chemicals to cause similar effects. There is no real consensus on what consciousness actually is. Kaku believes it is likely a continuum, with levels progressing from simple machines to animals, to humans. The constructionist view holds that making and evaluating consciousness is more important than having philosophical debates on the topic. Robots will likely blur the lines around any definition of consciousness, because once they master syntax, whether they can truly understand semantics will be a moot point. AI computers could easily become indistinguishable from humans, more intelligent, and develop their own agendas. This would make them dangerous, and as more vital infrastructure becomes dependent on computers, whole societies will become vulnerable to paralyzing breakdowns and cyber-attacks. Computers could potentially be the evolutionary successors to biological life, and humans may need to integrate with machines to survive. Cyborg bodies or the digital storage of neural architecture could become a cure for mortality. It is likely that thinking machines will become a reality in less than a century, making them a Class 1 impossibility.

Aliens and spaceships are intrinsic elements of science fiction media. As long as the field of modern science has existed, people have been wondering if astronomical bodies other than Earth are capable of sustaining life, despite religious institutions that gravely punished any speculation on the topic. New extrasolar planets are being discovered all the time, and so the question of whether any of them could or do host alien life is constantly in the public consciousness. Unidentified flying objects (UFOs) have been reported across the world since ancient times, and although the vast majority are explicable as human technology, Venus, or misidentified astronomical events, inexplicable sightings also occur. These reports are difficult to verify conclusively, but they have led many to speculate that extraterrestrial spaceships—possibly unmanned and based on the moon—belonging to a significantly more advanced civilization of aliens have already visited Earth.

It’s impossible to make definitive statements about the characteristics of extraterrestrial life, although we can speculate about some probable features. Aliens probably evolved in environments containing liquid water because it is a universal solvent ideal for hosting life. They likely have some sensory organs, the ability to move around their environment and communicate with each other, and some kind of hand or grabbing mechanism to interact with objects.

The scientific search for extraterrestrial life is spearheaded by the project The Search for Extraterrestrial Intelligence (SETI), which scans the cosmos for aberrations in microwave radiation. Despite one notable anomalous signal, they have not yet produced definite results. The Drake equation offered a mathematical estimation of the number of extrasolar planets capable of sustaining life and contacting Earth, but recent developments in mapping and the cosmos and analyzing cosmological bodies have thrown the applicability and accuracy of the calculation into question. Given the vigorous ongoing efforts made to discover extraterrestrial life and the rapid advancements in human technology, it is possible that if aliens do exist in our vicinity, contact will be made within the next century.

The ability of human civilization to survive the eventual death of our sun is dependent on our being able to develop the technology to travel between stars. Current rocket technology is far from capable of such a feat, but scientists are already theorizing about the types of crafts and engines that could allow interstellar travel.

Ion and plasma engines produce less thrust than conventional combustion rockets, but they can provide a consistent output for a far longer duration. Endurance is key to traversing the massive distances between stars, although neither of these designs can itself provide sufficient power. Solar sails are a more viable option because they harness the low but steady pressure of sunlight by capturing it on massive solar panels. Theoretically, they could attain huge speeds and travel indefinitely, but they are very vulnerable to collisions with space debris and pose massive engineering and logistical issues. Nuclear-powered rockets could produce the necessary energy, but they are incredibly risky since any mishaps could cause massive nuclear explosions and spew radioactive material across the Earth. Ramjet fusion is Kaku’s personal favorite candidate for interstellar travel. It would scoop hydrogen atoms from space, providing it with an inexhaustible source of fuel, and use fusion to convert the hydrogen into energy. Significant advancements in proton fusion technology are a prerequisite for developing this engine type in reality. Rail guns that propel projectiles using electromagnetic force have been proposed, but they are ill-suited to mobilizing large objects. Engine efficiency would be a major concern regardless of the type of engine used. Since escaping Earth’s atmosphere is one of the major hurdles to successful space travel, space elevators have long been considered as a possibility to cut down on the high costs and logistical hurdles associated with interstellar travel. A space elevator would extend out of Earth’s atmosphere, held up by the force of the Earth’s rotation, and allow materials to be cheaply and efficiently transported into space. The elevator would need to be very strong, but there are many projects underway (for instance, the development of longer carbon nanotubes) with the aim of making this technology a reality.

Long-term space travel involves other difficulties beyond engine power, particularly radiation exposure once outside the Earth’s protective atmosphere and the debilitating physical effects of extended periods in zero gravity. Suspended animation could protect from some of these effects by putting travelers into a stasis state and waking them up once they have arrived at their destination. Medical science would need to advance significantly to make this a reliable method. Interstellar travel could far more easily be achieved by nano-ships, tiny unmanned space ships capable of self-replication. They could be sent out in massive swarms to set up base on distant planets or moons and send information back to Earth.

For every atomic particle, an antimatter twin exists that has an opposite charge. The first ever discovered was the positron, which is identical to an electron, except that it carries a positive charge. Anti-elements, anti-chemistry, and even anti-universes are theoretically possible. Researchers have already created minute quantities of anti-hydrogen using particle accelerators. Although antimatter could exist indefinitely in a pure vacuum, in experimental conditions, it inevitably collides with particles of matter and is annihilated, releasing energy. It is speculated that the release of energy from antimatter-matter collisions could be used to power rockets or as the basis for powerful antimatter bombs. However, it is currently extraordinarily expensive to produce even tiny amounts of antimatter, so even though antimatter could fuel a highly efficient engine or detonation, it is not currently feasible as a source of energy (though production prices are rapidly falling). Physicists have yet to find naturally occurring antimatter in the universe, which is surprising, but this is most likely explained by the theory that a tiny asymmetry existed in the amount of antimatter and matter in the Big Bang. This would have led to the annihilation of most, if not all, naturally occurring antimatter, meaning that existing matter is the leftover surplus from the interaction. This is a field of intense study.