Conceptual computer artwork of multiple universes: Some physicists believe that there are an infinite number of parallel universes, created for each possible quantum mechanical outcome. The collective name for these universes is the multiverse.

Credit: Mehau Kulyk/SPL

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A Type I civilisation is a truly planetary one, which has mastered most forms of planetary energy. Their energy output could be between thousands and millions of times our own current output. Mark Twain once said, "Everyone complains about the weather, but no one does anything about it". This could change with a Type I civilisation, which has enough energy to modify the weather. It also has enough to build cities beneath oceans and alter the occurrence of earthquakes and volcanoes.

Currently, our energy output qualifies us for Type 0 status; Carl Sagan estimated that we qualify as a Type 0.7 civilisation. We derive our energy not from harnessing global forces, but by burning fossil fuels (oil and coal). But already, we can see the seeds of a Type I civilisation: when you read the newspaper, you see evidence everywhere that we are an emerging Type I civilisation. For example:

• The Internet will be our planetary 'telephone system'. Already, the Internet is the universal communication for science, commerce, the arts, politicians, and individuals. If the leader of a nation were attempt to ban the Internet, most people would simply laugh. It has become unstoppable.

• The planetary language of our future Type I civilisation will be English. This is already the number-one second language on Earth, spoken by most scientists, engineers, politicians, artists, and business people. For people in Asia, with so many local languages, the most convenient way to communicate is via everyone's second language. There will be one umbrella language for the entire planet – English – but beneath that umbrella, there will be hundreds of local languages.

• The planetary economy will be global. Already, we can see the emergence of the European Union, whose member nations have, for centuries, slaughtered each other's citizens. The E.U., in turn, was formed as a consequence of competition from an economically united North America under NAFTA (the North American Free Trade Agreement, covering Canada, the USA and Mexico).

• The planetary culture will be mass culture and youth culture. Already, movies, songs, books, art,
and ideas are distributed on a planet-wide scale. Like
planetary language, this culture will be everywhere on Earth, but will co-exist with local ones.

By definition, an advanced civilisation must grow faster than the frequency of life-threatening catastrophes. Since large meteor and comet impacts take place once every few thousand to million years, a Type I civilisation must master space travel to deflect space debris within that time, which should not be much of a problem. Ice ages may take place on a time scale of tens of thousands of years, and so a Type I civilisation must learn to modify the weather within that period.

Artificial and internal catastrophes must also be negotiated. Global pollution is a mortal threat for a Type 0 civilisation, but not a Type I civilisation, which has lived for several millennia as a global force and necessarily achieved ecological balance with its home planet. Internal problems such as wars do present a serious recurring threat, but emerging civilisations have thousands of years in which to solve their racial, national, and sectarian conflicts. Since it would take centuries or even millennia for a Type I civilisation to terraform nearby planets, its peoples will have plenty of time to work out their internal differences on the same planet before they finally leave the mother planet in any significant numbers.

Eventually, after several thousand years, a Type I civilisation will exhaust the power of its home planet, and derive its energy by consuming the entire output of energy available from its sun –
roughly a billion trillion trillion ergs per second.

With an energy output comparable to that of a small star, it should be visible from space. Freeman Dyson has proposed that a Type II civilisation may even build a gigantic sphere around its star to utilise more efficiently its total energy output. Even if it tries to conceal its existence, it must – to comply with the Second Law of Thermodynamics – emit waste heat. From outer space, its planet may be seen to glow like a Christmas-tree ornament. Dyson has even proposed looking specifically for infrared emissions (rather than radio and TV) to identify these Type II civilisations. So far, no evidence of such an infrared planet has been found (although hardly anyone has searched).

Perhaps the only serious threat to a Type II civilisation would be a nearby supernova explosion, whose sudden eruption could scorch their planet in a withering blast of X-rays, destroying all life. Thus, perhaps the most interesting civilisation is a Type III civilisation, for it is truly immortal. It has exhausted the power of a single star, and has reached out to other star systems. No natural catastrophe known to science has the capacity to destroy a Type III civilisation.

Faced with a neighbouring supernova, it would have several alternatives, for example altering the evolution of a dying red giant star which is about to explode, or leaving this particular star system and terraforming a nearby planetary system.

However, there are roadblocks to an emerging Type III civilisation. Eventually, it bumps into Einstein's theory of relativity. Nothing can travel faster than light, which is about 300,000km a second (for a possible loophole, see the end of this article). Since the universe is so vast and space is so empty, this absolute speed limit tends to hold back a civilisation's successful expansion. Dyson estimates that this roadblock may delay the transition from a Type II to a Type III civilisation by perhaps a million years or more.

But even with the light-speed barrier, alternatives exist for expanding at near-light velocities. For example, the ultimate measure of a rocket's capability is something called 'specific impulse', defined as the product of the thrust and the duration, and is measured in units of seconds. Chemical rockets can attain specific impulses that last from several hundreds to several thousands of seconds. Ion engines can attain specific impulses of tens of thousands of seconds. But to attain near-light velocity, one has to achieve specific impulse of about 30 million seconds, which is far beyond our current capability, but not that of a Type III civilisation. Various propulsion systems would be available for sub-light speed probes, such as ramjet fusion engines, photonic engines, anti-matter engines, and others we cannot even imagine.

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