OK, boys and girls of every age, want another big bad cliché? Here it is: planetary colonization and competing for planets.
A typical plot of an endless stream of SF-like books is warring for star systems containing habitable planets. People live on those planets, and intruders wan to settle there themselves, so they try to eliminate previous owners. Or people just rush forward to the Universe trying to find star systems with Earth-like planets.
Why is it a cliché?
First, the main advantage of an Earth-like planet is an opportunity to breath freely without wearing oxygen masks. However, look at an average human being. (S)he can survive only if the air contains exact percentage of oxygen, carbon dioxide and other gases. If there is too much oxygen, a human would die of oxygen poisoning. If there is too little of it, a human would suffocate. If there is too little carbon dioxide, a human would stop breathing as hir brain's respiratory center will stop functioning. If there is too much of it, a human would suffocate. The difference between breathable and non-breathable air might be tenths of per cent of a gas. As it would be too optimistic to expect that every Earth-like planet's atmosphere is an exact replica of the Earth's, we won't be able to get rid of breathing devices.
Add to it poisonous gases - it's any chemically active gas like sulfur (di)oxide. If there are such gases, you have to wear a pressurized environmental suit all the time. Any damage to the suit would mean (almost certain) death.
Then there is a matter of climate. Humans can exist only in a relatively narrow range of external temperatures (40-50 C or so). Shift the planetary surface's temperature range ten degrees up or down, and you'll need environmental suits.
At last, there is the matter of building objects (houses, plants, and so on) on the surface while fighting with hurricanes, earthquakes, landslides, tsunamis and too low or too high gravitation, fighting with atmospheric and water corrosion, and so on. And harvesting minerals on the planetary surface is very hard as we have to struggle with gravitation and friction all the time.
In other words, even an Earth-like planet will be unsuitable for "natural living" as it exists on Earth.
Where will we live, then? In space. Building a space station is much more expensive than that of a surface house, but once built, it'll serve almost endlessly while requiring minimal maintenance. And we even can use asteroids as foundations for space houses! Life support systems will be no more complex than on the surface, there is plenty of minerals in asteroids (there are huge belts of amorphous matter orbiting any star), there is no friction or gravitation, so we can easily get the minerals extracted, refined and sent to any place we wish. There is plenty of free energy in space as well. And so on.
In other words, the humanity won't search for or colonize Earth-like planets on purpose. It will be occasionally done if such a planet is discovered by accident, but planets will be rather health and spa resorts than industrial and living bases. Most human activity will be concentrated in the Great Void out there.
Oxygen - definitely yes. Methane? Possibly no, but there is plenty of it in the space where there never was any life (like gas giants).
There is the area around a GRB where you die whatever you do (short of escaping far away) and many areas where you can survive it if you take appropriate defense measures. As the space is huge, even in the Galaxy core the probability of getting caught in the first area is much lower than of being outside of it.
A typical plot of an endless stream of SF-like books is warring for star systems containing habitable planets. People live on those planets, and intruders wan to settle there themselves, so they try to eliminate previous owners. Or people just rush forward to the Universe trying to find star systems with Earth-like planets.
Why is it a cliché?
First, the main advantage of an Earth-like planet is an opportunity to breath freely without wearing oxygen masks. However, look at an average human being. (S)he can survive only if the air contains exact percentage of oxygen, carbon dioxide and other gases. If there is too much oxygen, a human would die of oxygen poisoning. If there is too little of it, a human would suffocate. If there is too little carbon dioxide, a human would stop breathing as hir brain's respiratory center will stop functioning. If there is too much of it, a human would suffocate. The difference between breathable and non-breathable air might be tenths of per cent of a gas. As it would be too optimistic to expect that every Earth-like planet's atmosphere is an exact replica of the Earth's, we won't be able to get rid of breathing devices.
Add to it poisonous gases - it's any chemically active gas like sulfur (di)oxide. If there are such gases, you have to wear a pressurized environmental suit all the time. Any damage to the suit would mean (almost certain) death.
Then there is a matter of climate. Humans can exist only in a relatively narrow range of external temperatures (40-50 C or so). Shift the planetary surface's temperature range ten degrees up or down, and you'll need environmental suits.
At last, there is the matter of building objects (houses, plants, and so on) on the surface while fighting with hurricanes, earthquakes, landslides, tsunamis and too low or too high gravitation, fighting with atmospheric and water corrosion, and so on. And harvesting minerals on the planetary surface is very hard as we have to struggle with gravitation and friction all the time.
In other words, even an Earth-like planet will be unsuitable for "natural living" as it exists on Earth.
Where will we live, then? In space. Building a space station is much more expensive than that of a surface house, but once built, it'll serve almost endlessly while requiring minimal maintenance. And we even can use asteroids as foundations for space houses! Life support systems will be no more complex than on the surface, there is plenty of minerals in asteroids (there are huge belts of amorphous matter orbiting any star), there is no friction or gravitation, so we can easily get the minerals extracted, refined and sent to any place we wish. There is plenty of free energy in space as well. And so on.
In other words, the humanity won't search for or colonize Earth-like planets on purpose. It will be occasionally done if such a planet is discovered by accident, but planets will be rather health and spa resorts than industrial and living bases. Most human activity will be concentrated in the Great Void out there.
So, to continue the point about atmospheric gases in permanent disequilibrium (Lovelock), your volcanic gases include oxygen and methane?
Oxygen - definitely yes. Methane? Possibly no, but there is plenty of it in the space where there never was any life (like gas giants).
A GRB is one of those events of which it can be said that the only real defence is not being there when it happens.
There is the area around a GRB where you die whatever you do (short of escaping far away) and many areas where you can survive it if you take appropriate defense measures. As the space is huge, even in the Galaxy core the probability of getting caught in the first area is much lower than of being outside of it.