A Nerdy Discussion of Interstellar
By Itai Agur
Let me first say that I am a huge, huge fan of Interstellar, and that I am grateful to Christopher Nolan and his whole team for their beautiful scientific visualization. The points below are a tribute to its inspiration, not a critique. Under the guidance of Professor Kip Thorne, one of the greatest living scientists, there can be no doubt that the movie has been made as realistic as any science fiction of its sort can be – and his book The Science of Interstellar is further evidence to this. But, being a science fiction movie (and with a very intricate plot), there are always some points that are open to discussion.
Cooper’s time dilation speech and giving Murph the wristwatch
The wristwatch plays a crucial role in the plot. Cooper explains to Murph that when he is in hyper-sleep, traveling at the speed of light or near a black hole, time will run differently for them, and that when he returns they will compare watches and may even be the same age. Consider first hyper-sleep and traveling at light-speed. While hyper-sleep may affect Cooper’s aging, it would not affect his watch. And as for travelling near the speed of light, Cooper never does and was not expected to (traveling through a wormhole is not related to traveling at light-speed: a light beam still travels much faster through it than a ship). There are two types of time dilation, one which relates to traveling near light-speed (Special Relativity) and one which is caused by gravity (General Relativity). Cooper experiences gravitational time dilation twice in the movie, namely at Miller’s planet and just before entering the black hole, Gargantua. As the Endurance’s crew discuss after passing through the wormhole, Miller’s planet is much closer to the black hole than NASA had expected: no gravitational time dilation had been anticipated for the mission at all. And, obviously, Cooper could not have known he would fall into the black hole.
Could Cooper have been thinking of the wormhole instead? A wormhole certainly could cause time dilation. However, NASA already knew that this wormhole did not cause such effects, because the Lazarus missions had gone through it and managed to transmit binary pings on an annual basis back to Earth. Time dilation would have affected the arrival times of those pings. Overall then, the moment that Cooper hands Murph the wristwatch makes sense in retrospect, but not when it occurs: Cooper had no reason to expect significant time dilation, let alone crossing ages with Murph, as a consequence of his mission.
Timelines
Cooper sends himself the coordinates of NASA’s facility from the future, which sets the story in motion. But how would he have found that facility the first time around (Loop1)? In order to enter a recurring time-loop, there has to be a first set of events that leads into it. Similarly, inside the tesseract Cooper says that “they are us”, that is, future humanity is saving present humanity. But how did humanity get to that future, if there was no-one there to help prevent extinction the first time around (Loop2)? Maybe Cooper is just conjecturing about this wrongly, which would undo Loop2. But Loop1 is much harder to get around: NASA was about to launch without Cooper and their facility was in a top secret location that Cooper would never have stumbled upon unless he had sent himself the coordinates from the future.
In addition, here are some other points to think about:
Finally, just for laughs: a proof that Wolf Edmunds is a criminal
Assumption: Amelia Brand is at least 8 years younger than Cooper
Seems fair enough, right? Ok, now follow a few steps. Murph was 10 years old when Cooper left. Cooper traveled for 2 years to the wormhole and subsequently lost 23 years in gravitational time dilation on Miller’s planet. When he returns to the Endurance he receives Murph’s message that she is now the same age as Cooper when he departed. This means he was 35 years old when he left Earth (which is a little hard to buy, but anyway). Now, by our assumption, this means that Amelia Brand was aged 27 or less at that time. And we know she had a relationship with Wolf Edmunds before he left on the Lazarus missions. The Lazarus missions were launched 10 years prior. Hence, when Brand and Edmunds were involved, Brand was underage. But Edmunds must have been an adult since he was already a particle physicist. QED.
By Itai Agur
Let me first say that I am a huge, huge fan of Interstellar, and that I am grateful to Christopher Nolan and his whole team for their beautiful scientific visualization. The points below are a tribute to its inspiration, not a critique. Under the guidance of Professor Kip Thorne, one of the greatest living scientists, there can be no doubt that the movie has been made as realistic as any science fiction of its sort can be – and his book The Science of Interstellar is further evidence to this. But, being a science fiction movie (and with a very intricate plot), there are always some points that are open to discussion.
Cooper’s time dilation speech and giving Murph the wristwatch
The wristwatch plays a crucial role in the plot. Cooper explains to Murph that when he is in hyper-sleep, traveling at the speed of light or near a black hole, time will run differently for them, and that when he returns they will compare watches and may even be the same age. Consider first hyper-sleep and traveling at light-speed. While hyper-sleep may affect Cooper’s aging, it would not affect his watch. And as for travelling near the speed of light, Cooper never does and was not expected to (traveling through a wormhole is not related to traveling at light-speed: a light beam still travels much faster through it than a ship). There are two types of time dilation, one which relates to traveling near light-speed (Special Relativity) and one which is caused by gravity (General Relativity). Cooper experiences gravitational time dilation twice in the movie, namely at Miller’s planet and just before entering the black hole, Gargantua. As the Endurance’s crew discuss after passing through the wormhole, Miller’s planet is much closer to the black hole than NASA had expected: no gravitational time dilation had been anticipated for the mission at all. And, obviously, Cooper could not have known he would fall into the black hole.
Could Cooper have been thinking of the wormhole instead? A wormhole certainly could cause time dilation. However, NASA already knew that this wormhole did not cause such effects, because the Lazarus missions had gone through it and managed to transmit binary pings on an annual basis back to Earth. Time dilation would have affected the arrival times of those pings. Overall then, the moment that Cooper hands Murph the wristwatch makes sense in retrospect, but not when it occurs: Cooper had no reason to expect significant time dilation, let alone crossing ages with Murph, as a consequence of his mission.
Timelines
Cooper sends himself the coordinates of NASA’s facility from the future, which sets the story in motion. But how would he have found that facility the first time around (Loop1)? In order to enter a recurring time-loop, there has to be a first set of events that leads into it. Similarly, inside the tesseract Cooper says that “they are us”, that is, future humanity is saving present humanity. But how did humanity get to that future, if there was no-one there to help prevent extinction the first time around (Loop2)? Maybe Cooper is just conjecturing about this wrongly, which would undo Loop2. But Loop1 is much harder to get around: NASA was about to launch without Cooper and their facility was in a top secret location that Cooper would never have stumbled upon unless he had sent himself the coordinates from the future.
In addition, here are some other points to think about:
- The rotation of the Endurance creates artificial gravity. On the approach to the wormhole, Romilly asks Cooper to "stop the spinning" and Cooper does so. Romilly is standing next to Cooper, but he stays on the ground: without artificial gravity he should have started floating.
- If, as Romilly says, the Endurance’s outer hull consists of only “millimeters of aluminum”, then how did he survive bombardment by radiation during decades? Radiation in our own solar system is already sufficient to be the number one constraint in sending humans to Mars. But in the vicinity of a supermassive black hole radiation is much more intense.
- Concerning the black hole, Romilly laments that "if we could just see the collapsed star inside" quantum gravity could be solved. This sentence could not have been checked with Professor Thorne, for Gargantua is far too large to have been formed by a collapsed star. It belongs to the class of supermassive black holes at galactic cores. Romilly should have only referred to "the singularity inside" (or actually "one of the singularities" - as Prof. Thorne explains in his book, there are three singularities in Gargantua).
- How do 23 Earth years pass while Cooper and Brand are on Miller’s surface? It’s 7 years per hour, but the camera stays with the crew every second (no fade-outs), and they spend about 12 minutes on the surface. The Ranger's approach to the planet could not have taken hours, and was in fact accounted for by Cooper in advance, when he expected to get the whole thing done quickly (nor would the entire trip from Endurance to Miller be subject to extreme time dilation, which only really becomes extreme when very close to Miller and thereby Gargantua).
- Why could the Endurance not send a signal back to Earth during all those decades, if several of the Lazarus missions had consistently managed to send “binary pings on an annual basis” through the wormhole?
- The final shot of the movie suggests that Amelia Brand has not aged relative to Cooper. But Cooper spent a little more time near Gargantua’s event horizon than she did, and came closer to the horizon (all the way to the edge) than she did. At such vicinity to a black hole every second and every meter counts.
- In fact, this means that at the end of the movie there are two Coopers in the Gargantuan system. One Cooper is flying back towards Brand. The other is still falling into the black hole: because time dilation is infinite at the event horizon, to any observer outside the black hole Cooper is forever at the event horizon. Cooper himself is also such an observer, however, after he re-emerges from the tesseract.
- There remains only one question that really concerns me: is that corn beer that Cooper and Donald are drinking? The wheat had died after all.
Finally, just for laughs: a proof that Wolf Edmunds is a criminal
Assumption: Amelia Brand is at least 8 years younger than Cooper
Seems fair enough, right? Ok, now follow a few steps. Murph was 10 years old when Cooper left. Cooper traveled for 2 years to the wormhole and subsequently lost 23 years in gravitational time dilation on Miller’s planet. When he returns to the Endurance he receives Murph’s message that she is now the same age as Cooper when he departed. This means he was 35 years old when he left Earth (which is a little hard to buy, but anyway). Now, by our assumption, this means that Amelia Brand was aged 27 or less at that time. And we know she had a relationship with Wolf Edmunds before he left on the Lazarus missions. The Lazarus missions were launched 10 years prior. Hence, when Brand and Edmunds were involved, Brand was underage. But Edmunds must have been an adult since he was already a particle physicist. QED.
