Confession time: I’ve really procrastinated writing about this planet as it is by far the most scientifically demanding. Interstellar is rather famous for its dedication to science- I’m sure even an occasional partaker in the science fiction genre has heard of this fact. Much has already been said about the metaphorical star (please forgive this terrible pun) of the movie, which, ironically, isn’t a star at all but a black hole. Gargantua is aptly named as it has a mass of 100 million suns and it is around this monolith that our humble planet, which I shall refer to as Miller, orbits.
Being conscious of time and the limits of a teenage brain unversed in any physics harder than that of Year 10 coursework, I will limit my exploration of Miller to just one question: is it possible for a planet to have a stable orbit so close to a black hole?
Common sense may give the impression that it is impossible to orbit a massive black hole without being torn apart by its gravity, which is so extreme that time literally slows down. However, there is another force being exerted on Miller – centrifugal force from Gargantua’s spin. Even as gravity is pulling Miller inwards, centrifugal force is pushing Miller outwards, counterbalancing each other.
This graph illustrates how the two forces vary in strength depending on the distance from Gargantua’s event horizon. The curves intersect at “inner balance point” and “outer balance point”, revealing that at these two distances, the strength of both forces is equal. While it may appear as though both points are viable orbits for Miller, the truth is that only the outer balance point will be stable. At the inner balance point, any deviation from the equilibrium of the forces would cause one force to win over the other, either pulling Miller into Gargantua or pushing it out towards the outer balance point. By contrast, the outer balance point is stable; should Miller be pulled in, the stronger centrifugal force would restore Miller to its orbit (try visualising this using the graph) and conversely, gravity would pull Miller back in if it drifted out.
Of course, everything I have attempted to explain has been greatly simplified and there is so much more science that goes into the making of Interstellar– so much, in fact, that there is an entire book about it.
In terms of where Miller will go in the extremely non-accurate tier list, I feel compelled by the heavy weight of all of my science textbooks to rank this planet as a solid S.
S for slow and steady, but also for spectacular visuals.
Kohli, I. S. (2015, August 08). On The Science of Interstellar. Retrieved December 30, 2020, from https://relativitydigest.com/2014/11/07/on-the-science-of-interstellar/
Thorne, K. S. (2014). The science of interstellar. New York: W.W. Norton & Company.