I went to see Christopher Nolan's new movie Interstellar last Thursday night, and I drove home with a lot of questions. I don't generally scrutinize films based on their real-world scientific merit. For example, my wife and I took our kids to see Big Hero 6 on Saturday, and never once did I find myself asking, "What are the scientific implications of this adolescent boy befriending a balloon-looking robot built by his older brother?"
However, Interstellar spends a lot of time grounding the audience in its reality. That's what most Christopher Nolan movies seem to do--propose that this could possibly happen in our world. Even his Dark Knight trilogy seemed to take the idea of Batman very seriously.
Also, there is a lot of scientific jargon in the film, and most of it seems to be based in something real. So as I sat in my seat for the nearly three hours of the film's running time, I continued to wonder how true-to-life the scientific elements in the movie really are. I consciously thought, "I wish my friend Mike McHargue (known to many as "Science Mike") was sitting here with me so I could tap him on the shoulder and ask, Hey, Mike. Is that real?" (To which he would probably reply, Shhh! I'm watching a movie!)
So I sent Mike a Facebook message and asked him if he could help me with some of my questions about the movie. He replied that lots of people had been asking the same thing, which is not surprising at all. In fact, he's been so bombarded with questions about Interstellar that this week's episode of The Liturgists Podcast (which he co-founded with Michael and Lisa Gungor) will be exclusively devoted to discussing the film.
So I told him that--for the sake of time and not repeating himself too much--I would limit the number of my questions to five and post them on my blog in preparation for the longer discussion on his podcast.
So here is my five-question interview about Interstellar with "Science Mike" McHargue.
(WARNING: There are major plot points from the film discussed here, so if you haven't seen the movie and don't want any spoilers, I would recommend waiting to read this interview until after you've seen Interstellar)
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1) Rob: The premise of the film is that the earth's agricultural sustainability is dying. I'm curious about whether or not this is even possible and whether or not science would be able to find a way to overcome such a thing through greenhouse agricultural or other awesome things people can do.
Mike: This is certainly possible. Desertification is one of the most prominent effects of climate change, and deserts are very poor for agriculture (obviously). Satellite imagery reveals how quickly our blue-green world is turning brown. The problem with using anything like green houses or mass desalinization/irrigation is cost and scale. We don't have the economic capacity to terraform our own lands on that large a scale. Just look back to the Dust Bowl of the 1930s to see how quickly soil can turn on us if we don’t manage our resources well.
2) Rob: There's a scene in which a group of astronauts goes down onto a planet and are there for one hour (to them) but then return to the mothership, and it's been twenty years. In the film, it is said that this happens because of Relativity.
Mike: That's real! Relativity indicates that time and space are part of a single fabric (spacetime) and that gravity warps spacetime. This means time isn't some universal metronome, but instead a local variable that varies with speed and gravitation.
Our own solar system has a star [the sun], and stars are massive. The extreme degree to which the sun bends space time means that Mercury's orbit doesn't work out quite right in Newtonian physics. Einstein's relativity, however, perfectly predicts Mercury's behavior. In this way, you can say that Mercury has a "relativistic orbit." It's a small effect to be sure, but it's measurable.
Black Holes have incredible gravity, so much that light can't escape. Because of this immense mass, they warp spacetime far more than any star. A very close orbit around a black hole could actually cause time to stretch and distort the way the movie claims-but there's one problem.
Any orbit close enough to stretch time like that would likely destroy a planet. Of course, the black hole in Interstellar is actually a Super Massive Blackhole rotating at near light speed, so its relativistic effects are more pronounced than a conventional black hole, but I still wonder if there is a safe, stable orbit that allows this kind of time dilation without wrecking the planet (to say nothing of constant orbital bombardment from matter falling toward the black hole at a high fraction of light speed). Some of Jupiter's moons experience terrible tidal stress, and won't last all that long as a result. A planet that was close enough to a black hole to have such dramatic time dilation could be torn into pieces very quickly or smashed to bits by particles and other matter racing into the event horizon.
3) Rob: There's also some craziness with a wormhole. As far as a plot device, it's a pretty Deus Ex Machina kind of moment, in that it seems to just show up exactly when it's needed. I am curious about if wormholes are actually real, or if they have only been discussed theoretically.
Mike: Wormholes are real, but the only ones we know about are tiny--like subatomic tiny. Many physicists believe that quantum entanglement happens via wormholes. That's great for quantum entanglement, but it's not going to take a spaceship anywhere.
Now, I did read a piece in Wired that talked about the visual effects in the film. They had to write a new rendered to deal with the way blackholes curve gravity, and they consulted a physicist to get the math right. The visual of a black hole and wormhole are probably among the most accurate we've produced for film.
4) Rob: The whole point of the film is that these humans are looking for another planet for humanity to inhabit. Do you think something like this could actually exist somewhere in the universe? If so, are we already looking for something like that? Follow up: What is the likelihood that a planet like that would already be populated? Doesn’t Steven Hawking believe that there is intelligent life somewhere in the universe? I mean, if there is another habitable planet, how likely is that it would already be inhabited?
Mike: Planets are common. Really common. Now that our telescopes have gotten better, we find exoplanets all the time. It looks like planets far outnumber stars in our galaxy, and we have no reason to think that’s not the norm everywhere. Some small fraction of those planets likely have conditions similar to earth: reasonable gravity, liquid water, stable temperatures, and active plate tectonics. Some small fraction of those worlds probably harbor life—to say nothing of planets unlike the Earth that could host life that is different than life here. Our galaxy is likely teaming with microbial life, although a lot of those microbes may look nothing like ours.
The problem is the scale of the galaxy. We just don’t have the technology to cross interstellar distances today, and the Fermi Paradox and the Great Filter theory make me wonder if we ever will.
5) Rob: How in the holy crap did Coop go through a blackhole and somehow end up in some kind of five-dimensional vortex that led directly to his daughter's bedroom? I realize that this is a contrivance of the film, but I didn’t even understand the scientific rules that supposedly got them there. By that point, I felt like I was re-watching 2001: A Space Odyssey, and my brain was saying, “Shhh. Just go with it.” Can you help me with this?
Mike: In Interstellar, singularity was used as the ultimate deus ex machina. We don’t understand what happens inside a blackhole, and blackholes remind us that we are pretty ignorant about one of the fundamental forces of physics (gravity). What’s possible inside a blackhole? No one knows. Very bright physicists have all sorts of ideas: they may be Universes of their own, they may contain this Universe in a strange sort of recursive loop, or they may be gateways to other realities. Nolan exploited this to allow Cooper to travel across space time via the tesseract, itself a three dimensional representation of this “fifth dimensional” reality. Additional dimensions of space are theoretical and generally associated with string theory. Interstellar seems makes an assumption that the brane model of the Universe is correct. In the future, particle accelerators may prove these ideas untenable, but for now the assumptions are reasonable on some level, especially for a feature film.
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Thanks so much to Mike McHargue for indulging my curiosity and letting me post our conversation here.
If you want to hear an excellent presentation by Mike on the topic of faith and the human brain, you can listen to his talk from June 2014 at Collective Church in Fort Worth, Texas.