The Science of Interstellar 1 Christopher Nolan’s epic, visionary science fiction adventure puts on the screen some of the most amazing images of space and space travel, ever filmed. But how accurate is the science behind Interstellar? Here we highlight some big science questions in the movie, and the real science behind them. Could we travel to the stars? 2 If reaching the outer planets of the solar system is an ambitious, but achievable, goal within a few generations, sending humans beyond the solar system presents a much greater challenge. The problem is that space is really, really big! If the distance from the Earth to the Sun is taken as one unit (in fact scientists refer to this distance—about 150 million kilometres—as an “astronomical unit”) then the distance from the Earth to Saturn is about 8.5 units. On this same scale, however, the distance to even the nearest star is more than 20,000 times greater! This is why astronomers use a different unit of distance than miles or kilometres: they use the light year, or the distance travelled by a beam of light (which moves at about 300,000 kilometres per second) in one year. A light year is about 10 million, million kilometres, and by comparison the astronomical unit is only about 8 light minutes. And yet even the nearest star is more than 4 light years away, and the Milky Way galaxy—home to over 100 billion stars—is about 100,000 light years across. 3 Could we ever build a spacecraft capable of crossing such vast distances? Could astronauts survive such a journey? According to Albert Einstein’s theory of relativity, the speed of light is the ultimate cosmic speed limit: nothing can travel faster than light. But relativity also predicts that, for astronauts travelling close to the speed of light, time on board their spaceship runs more slowly. So if a spaceship could travel at such a speed (leaving aside the enormous engineering challenges this presents) in principle it could cover hundreds of light years while the astronauts on board aged by only a decade or so. The catch, however, is that by the time the spaceship returned to the Earth many centuries would have passed, and the astronauts’ families and friends would be long dead. 4 Is Einstein’s theory and its cosmic speed limit the last word on interstellar travel, then? What about the “hyperspace” and “time warp”—favourite of science fiction? Could that point the way to a massive cosmic shortcut? Is there life elsewhere in the universe? 5 Perhaps this is the hardest of our questions to answer, as it doesn’t simply depend on the laws of physics but on many other complex areas of science that we don’t yet fully understand. We can say for sure that life exists on the Earth, and we can also say for sure that there are billions of stars in the universe—many of which are just like the Sun. In the past 20 years we have detected planets orbiting some of those stars in our immediate cosmic neighbourhood, and it looks very much as if planets are commonplace. Moreover, some recent studies strongly suggest that rocky, Earth-like planets may be very common too. In the next few decades we hope to start detecting these planets in large numbers. Using giant telescopes on the ground and in space we should be able to work out what their atmospheres are made of and whether they could support life. 6 So if there are lots of planets out there capable of supporting life like us, and the Earth turned out to be the only place in the universe where life has arisen, then (as Carl Sagan once famously said) this would seem like an awful waste of space! 1 Interstellar is a movie that _ . A. serves as a science textbook on space B. puts a lot of effort into its visual effects C. is based on Nolan’s space adventure D. receives an award as the best movie 2 Sending people to the outer planets of the solar system is a _ . A. task that is more challenging than time travel B. time-consuming task requiring lots of effort C. dream in science fiction that is out of reach D. goal that every human being is committed to 3 How could astronauts survive a journey that covers hundreds of light years? __ . A. By travelling at the speed close to 300,000 kilometres per second. B. By going into a sound sleep on the spaceship. C. By bringing their families together with them. D. By breaking Albert Einstein’s theory of relativity. 4 Why is the question “Is there life elsewhere in the universe” difficult to answer? __ A. Because no alien life has been found by scientists. B. Because the laws of physics are too difficult for humans. C. Because many areas of science are too complicated. D. Because we haven’t taken the question into consideration. 5 Which of the following statements is true about Earth-like planets? __ A. Earth-like planets orbit the Sun in the solar system. B. Earth-like planets have been found in great numbers. C. Earth-like planets with atmospheres can support life. D. Earth-like planets might be observed through giant telescopes.