Never has a movie, that has affected me so deeply, been so less appreciated - relatively speaking, of course. Previous movies that I've greatly liked - Saving Private Ryan, Terminator 2, Fight Club, Dark Knight - are all universally loved. Why, then, has this movie failed to woo all alike? One possible reason is that the movie appears to be - to the 'un-initiated' - a 'cinematic convenience' that doesn't belong in an otherwise 'scientific' movie. This blog entry is an attempt to help make more sense of this movie.
Human space exploration: The reality today
The unfortunate fact of space exploration today is that lesser and lesser resources are being devoted today to the exploration of the Universe beyond our planet. It was only a few decades ago that nations were racing against one another to go farther - 'where no man has gone before'. The soviets sent the first satellite into orbit, first moon probe, and landed objects on Venus, while the US landed probes on Mars, and men on the Moon. It isn't difficult to fathom that people back then started predicting the date by which we will explore more planets - hopefully even beyond our solar system. Today, sadly, things are different. We haven't gone beyond Mars or Venus, and traveling to other stars only happens in Star Trek and Superman movies. The reasons for this decline can be classified into two categories - money and science. The problems associated with money are pretty obvious - there is very little you can derive in the short (enough) term that could justify putting money on such projects, at least not in the current 'quarter on quarter' business scenario.The science part comes from Einstein's General theory of relativity - which limits the speed at which you can move across space. At our current 'fastest possible' speeds, we take a few months to reach Mars, and the nearest star would take thousands of years to reach. It's like you have to travel a distance of 10,000 miles, but you're limited to a speed of one inch per month.
First, let's understand the 'science stuff' in the movie
Let me begin by stating that I am, by no means, an expert on this matter. However, as a lay person who understood the movie, I believe I do have something to say that would enable others, like me, to get a perspective on the movie. Several concepts of physics are touched upon in this movie: Black holes, which are real, and wormholes which, at this point in time, are purely theoretical. And then there is the 'bending' or 'squeezing' of space time - the whole 'one hour = 7 years' thing. And finally, the Tesseract - not as it's shown in the 'Avengers' movie - but the actual scientific one.
Wormholes
A wormhole (technically an Einstein Rosen bridge) is a theoretical construct that allows us to go to a different place in space - without having to travel the full distance. Think of a worm trying to crawl from the top of an apple to the bottom. If it is only allowed to travel on the surface of the apple, it has to travel across the entire circumference (well, half of it) to reach the bottom. However, if a hole is drilled from top to bottom through the apple, then the worm has to travel far lesser distance to reach the same spot. Assuming a spherical apple which is 4 inches wide, distance travelled via the surface would be about 6.28 inches, while the distance through the drilled hole would be only 4 inches - lesser distance equals lesser time.A wormhole in space, similarly, would enable travel through a 'shortcut' - thus preventing the need to travel the full distance and thereby saving time.
Time is relative
This is a concept that, in varying degree, is now known to most of us. Time occurs at different speeds in different points of space. This 'space-time' is an important concept that one needs to wrap one's head around. The premise is that time, in that how fast or slow it moves, is a function of where one is in space. Gravity will make time go faster! Now, to a person in that gravitational field, time will appear to move 'at its own pace'. It will be faster relative to (and hence the moniker 'relativity', you see) a person in a weaker gravity. This phenomenon, again, is not theoretical, but 100% real: the satellites used by GPS have to take this into account since they're farther from the earth's gravity than we - on it's surface - are. This is called 'Time Dilation'.
Black holes
Unlike wormholes which are purely theoretical, black holes actually exist. The reigning theory on their formation is that they come from large stars. Stars are the most massive objects, the ones with the strongest gravity, in the known universe. A large enough star, therefore, would have enough gravity to cause the entire mass of the star to collapse in on itself, leading to the formation of a black hole - something with gravity so strong that nothing can escape it, not even light. Actually, that last statement is a bit misleading because it would suggest that light can 'escape' other objects. The fact is that light will bend - much like it does when it goes through a glass or lens - around any gravity. This phenomenon, called 'Gravitational Lensing' is observed all the time (one of the groundbreaking predictions of Einstein's theory of relativity), and a black hole is where light is bent until it 'breaks' i.e. sucked right in. When we 'see' an object, we only perceive the light given out by that object. Since a black hole gives out no visible light, one wouldn't really know what they would 'look' like. Light is, however, only one part of the story. Since gravity affects time, a black hole would 'squeeze' time to a point where 'fast' and 'slow' passage of time no longer mean anything. A point where, conceivably, one could look at building a five-dimensional object - the Tesseract.
Tesseract
The question to ask about a 'four dimensional' cube is this: Why the extra dimension? Why are the regular, three dimensions not enough? It's like this: Imagine that you lived in a one-dimensional world i.e. you could only move in one direction. If you needed to 'bend' that space and create a wormhole in this uni-dimensional world, you would need be in a second dimension to be able to access those points that one would want to bring closer than they are in that one dimension. Similarly, one would need to go into a higher dimension to be able to create a wormhole in our, three dimensional space. The tesseract, however, isn't just a four-dimensional object. It can actually access five dimensions, with time being a dimension that already exists in our world, which is hence a four-dimensional world - making the tesseract a five-dimensional object. By allowing one to access all four dimensions (from the fifth dimension) one could theoretically see the entire life of a person all at once. This is all theoretical, of course, but not exactly fictional like dragons or fairies, it's fully based in science.
Coming back to Interstellar (spoilers ahead)
If one was looking for a new planet to settle on, one would have to travel to another star that it is orbiting - one that morphed into a black hole, perhaps. Hence the phenomenon of time passing faster in one of those planets The only way to travel to such a planet would conceivably be only through a wormhole. Since wormholes haven't been observed in the natural universe thus far, this particular one has perhaps been created by beings who have access to the fifth dimension. And also that gravity is the only thing that reaches across all dimensions. Any communication through time - i.e. reaching back to someone in the past, or future - would therefore be via gravity, appearing as gravitational anomalies in that point of space time. The 'ghost' in the girl's room, is McConaughey 'reaching out' through gravity: first, to try and push her to convince her dad (that's himself) to stay, and then, once he realizes that he can't change the past, puts in the information necessary to ensure that they reach NASA in the first place, then the information regarding the black hole that would allow them to get everybody off the earth. Their proximity to the black hole - first to visit that watery planet, and then to slingshot around it - explains the reason why the protagonist hardly ages while his daughter ages from a teenager to nearly her deathbed.
Interstellar is a brilliant movie, it brings together several scientific challenges associated with space travel along with a very human story. Some of the concepts used have never been seen by us humans, and yet have painted a vision of wormholes and black holes that, physicists agree, is probably the way they would actually look. This is nothing short of a cinematic milestone, and ought to have been more recognized.
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