I love hard sci-fi, but it is so rare to see it on the big screen because it usually requires a lot of world-building, a lot of exposition, a lot of establishing the scientific rules and explaining of how complicated concepts work in a way that is easy for audiences to understand. Arrival did it, and that film is clearly a cousin to Contact, the Carl Sagan-penned sci-fi opus about a talented and driven scientist (Jodie Foster) fighting against gender discrimination, bureaucracy and God to discover the truth through scientific inquiry. Interstellar is the shack-dwelling relative that neither Arrival nor Contact want to talk about.
Foster works for SETI, searching the sky for radio signals and scrambling to find funding (which eventually comes from a mysterious, Elon Musk-style benefactor). Her hard work and persistence pay off because they find a signal, a broadcast of the 1933 Olympic Games bounced back with plans for a complicated mystery machine embedded in it. This, the discovery part, is generally my favourite part of any good sci-fi because it’s often rooted in real, plausible scientific concepts and ideas. That an alien civilization would communicate using prime numbers is totally believable and really very interesting. The rest of it follows the construction of the machine, the destruction of the machine, the surprise reveal that a secret machine exists, and then a journey through a wormhole to a distant part of space where an alien appears to her as a vision of her dead father and assures her that humans are not alone in the universe but that she will have to go back to Earth with no proof which seems, I’ll be honest, kind of like an intergalactic dick move. To observers on Earth it appears that her pod merely passes through the machine and into the ocean.
It’s a suitably ambiguous way to deal with space-travel, and perhaps more importantly it gets at one of the main themes in the movie which is about religion (faith) vs science. Because Foster comes back with no proof of where she went, the world on Earth must take her word on faith (we will accept, for the purposes of the story, that there was absolutely no scientific way of determining on Earth how the machine worked even though we find that idea highly far-fetched). This is, of course, meant to contrast with other people who place their faith in religion without any proof other than the word of long-dead proselytizers. And, further, the movie pokes around at the ways in which faith can be used for both productive purposes and for terrible purposes. The implication is that we have the power to decide what we do with our faith and how we use it. And if we use it well, we will get to join the aliens in their intergalactic space super-highway. It's a hopeful message, laced with caution about our own worst impulses holding us back.
The acting is strong all-around (including Matthew McConaughey as a lover/priest/cool guy). The effects, used minimally and for maximum impact, still hold up 20 years later. The science is sound. And the story digs at some deep ideas about science, religion, faith and technology. It gets a little high-handed when, for instance,McConaughey compares God to love. “Do you love your father? How do you know? That’s the same way it is with God.” Well, actually no. Not really because you know that your father exists because you came out of his penis. But we will generally accept the concept that there are unknowable truths that lie beyond the reach of our (current) scientific capabilities and understanding of the world, and that there is a blurred and magnificently messy line between what we know and what we think we know and what can be known and what we want to know.
Also an interesting note here is that the filmmakers took an actual speech that Bill Clinton made about a space rock, and spliced it into the narrative mostly unaltered to make it seem like Clinton was talking about a message received from an unknown space civilization. The White House sent a letter to the studio telling them this violated the fair use standard and that it was somewhat of a fine line to suggest that Clinton supported the search for extra-terrestrial life, but they took no legal action. I think that is a pretty awesome little footnote to the arc of this movie.