# Physics of "Interstellar"

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Physics of â€œInterstellarâ€

After watching the movie â€œInterstellar,â€ your assignment is to pick two different story / plot points or phenomena demonstrated in the film and analyze the physics involved. Is what they demonstrate consistent with current theories? Why or why not?

Post your findings in the APlusPhysics Community, Forums section, under TV & Movie Physics by responding to the Interstellar thread. You can create two separate responses, one for each topic, or combine them into a single post. Respond to the posts of at least two other students.

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When I first saw this movie, there was one big question I had. Why is the planet Miller not pulled into the Black Hole Gargantua by the gravitational force, and so I did some research and found out some cool stuff.

One of the main reasons Planet Miller isn't pulled into the black hole in spite of its proximity is that the adviser, Kip Thorne made sure that Gargantua was a rapidly spinning black holeâ€”and it turns out that the physics of rotating black holes differ from non-rotating ones. The sheer speed of Gargantua's rotation means there is a single stable orbit just outside of Gargantua's event horizon that is very stable. However, Gargantua would have to fill half the sky in order for it to be so close.

With spinning black holes, the area where the time dilates as drastically as in the movie is expanded exponentially, which allows for a small area where an object can orbit.

Another cool thing about this movie is the the tidal waves on the planet miller. According to The Science of Interstellar by Kip Thorne, Miller's planet is shaped a little like a football, with one end constantly pointing at Gargantua. The waves are literally tidal waves, so it's not the waves coming toward you, it's the planet rotating under you and the fixed waves slamming into you. But because the planet doesn't rotate, the waves wouldn't slam into you. Fortunately, tidally locked planets can rock back and forth, and Thorne used this as a scientifically accurate loophole to explain tidal waves on a tidally locked planet. Also, because the water on Miller is mostly concentrated in the waves, you could have knee-high oceans, like the one shown in the film.
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Great analyses guys -- I'm very much enjoying the movie and the science!  Those waves on Miller were especially intriguing.

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After watching Interstellar, one can pretty much gather that Miller's planet is weird. On top of the aforementioned super-massive tidal waves and its close proximity to a rotating black hole, Gargantua, it has a very interesting property regarding its time "flow" - one hour on this planet equates to 7 years on Earth. So what does this mean? Are those on Miller's planet aging at a vastly accelerated rate? Is everything in slow motion? Well, the answer can be summarized like this: it's all about perspective.

On Miller's planet, the flow of time doesn't feel any different than it does on Earth. From their point of view, time is running normally, and they aren't aging any faster. It's not like if they spent a few days there, they'd come out looking way older, they'd just look a few days older (which is to say, not at all). However, after a few days, if they came back to Earth, everyone they know and love would be dead. Which is kind of a bummer, really, and that's why they wanted to get out of there so quickly - they were looking to save humanity, so time, like fuel and sustenance, was a valuable and irretrievable resource.

This time dilation is all due to gravity. Being so near the huge gravity of Gargantua means time would flow much slower (1 Earth hour is .06 Miller seconds). But if someone were to record a video for an hour on Miller and bring it back to Earth, it'd still only take an hour to watch. Now if somehow a live feed were set up, to watch those on Miller experience an hour, it'd take 7 years. So they'd be moving pretty slowly.

The second thing I wanted to touch on was quantum data. What was it, why was it so important, and what was it doing in a black hole?

The Earth is falling apart due to the blight, massive dust clouds causing lack of food and sickness among Earth's inhabitants. We need to get out of there and fast. So to do this, we need to harness the power of gravitation. With all the additional dimensions and nuances of the Universe as demonstrated in the film, the gravitational constant G is not necessarily true all over, so we need to investigate quantum gravity, the effects that massive gravitational fields have on subatomic particles. And the gravitational field that Gargantua exerts on subatomic particles would be a great way of analyzing quantum gravity and allow Murph back home to complete the equation.

Cooper and TARS fall into the black hole, and the quantum data they discover is sent back to Murph; with this data, she can finish the second half of the equation that the late professor failed to do during his lifetime. With the completion of this goal, humanity can finally leave the Earth - the answer lied within gravity. As you may recall when Cooper wakes up, he is inside of a dome-like structure with buildings hanging upside down. This was made possible with the quantum data that the characters in the movie were so fond of mentioning.

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Nate--

Negative energy - can't really wrap my head around that. Very cool.

Justin--

That stuff about the planet rotating under you and forcing you into fixed waves is even scarier than the idea of your traditional tidal wave. Awesome

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• 2 weeks later...

One of the physics concepts I picked up in Interstellar was the physics was the idea of a 5th dimension. I did some research and very quickly realized that I had opened the Pandora's box that is quantum physics. Simply put: I was lost. So I asked my physicist brother for some help and ended up getting a ten minute crash course in the dimensions.

Here's what I got. To gain the perspective of another spacial dimension: When you hit a 2-dimensional drum set, which is in "flatland," you have to hit it from our third dimension, one in which the drum head would never perceive. Likewise, you can't smack a spherical drum unless you're smacking it from the fourth dimension; we are in the third. Matthew McConaughey (Cooper) was essentially doing the dot product between himself and the rest of space-time (everything, the universe?) when he interacted with Murphy's room  from inside the tesseract (5th dimension).

If anyone cares to help me out and explain this whole 5th dimension thing a little more, it would be appreciated.

Moving on, I was also curious about the equation that Dr. Brand and Murphy are trying to solve on Earth. The premise of this equation was to enable humans to understand and control gravity, but how could that even be possible? For the most part, since this within the realm of theoretical physics, this was left up to speculation. However, I did find it interesting to note a one of the ideas that I found, since it made the most sense to me. So the basic idea was that Murphy and Brand were trying to unify the concepts of gravity and Newton's laws with theories of quantum mechanics and the dimensions. Murphy and Brand were trying to use the fifth dimension to learn about and control gravity in the third dimension. The idea, as physicist Kip Thorne suggests in his book The Science of Interstellar, is that Murphy was able to locally reset Newton's gravitational constant (G), in effect shutting off Earth's gravity so small rockets could launch the space stations into space and toward Saturn. The Earth, obviously, would not make it.

Since most of this is theoretical, as a lot quantum physics is, there are bound to be discrepancies with existing theories. It happens to be one of those concepts that is still open to discussion and frequently debated about.

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Justin- I had no idea that the tidal waves on Miller's planet were fixed waves, I did not even know that fixed waves could actually be possible in that sense (as stupid as that might sound). That is really cool (and kind of freaky).

Jake- The idea of watching a live feed from Miller's planet is definitely something I would never have thought of, very cool! I think the idea of time dilation, as you described and applied it here, is pretty neat and a little bit scary. I can't imagine watching a live feed moving that slow!

Nate- I actually was wondering about how Cooper could have gotten out of the black hole, thanks for the explanation! Very interesting ideas!

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So I like going to the planetarium a lot, and last year I went quite a few times to watch and re-watch a presentation on black holes. Watching Interstellar for the first time in class then, I had already some preconceived notions on understanding the idea of black holes and the science/physics behind them. Basically, the second I understood that Cooper and his fellow astronauts planned to enter the black holes to travel across the universe, I was concerned and confused. According to the Strasenburgh Planetarium of Rochester, New York: that isn't really super possible.

The website won't let me attach my diagram, so I'm going to paint you a mental picture. A 2D circle, with a dot in the center. Imagination, guys. Got it? Okay, so the circumference of said circle is the event horizon of a black hole and the dot at the center is the singularity. Upon first glance, we would say that this is a representation of, for lack of a better word, a "snapshot" of a black hole; a way to symbolize the space within it. But it's not that simple. Inside of a black hole, the positions of time and space SWITCH. Time becomes the variable and space is constant. This diagram represents a kaleidoscopic view of many different TIMES. A black hole cannot be explained in distance, width, length or any sort of SPACE. Distances in a black hole moreover correspond to different MOMENTS.

Along with this: we know that time goes on, and on, and on and on and on, and therefore the singularity of a black hole is not a single point, but exceeds infinitely long.

Ergo, as weird as it may sound, we can look at a sphere and see a sphere. We can look at a black hole and see a sphere. INSIDE of a sphere we have an area; a defined area. Inside of a black hole we have an INFINITE area. Therefore, infinitely large objects can be hidden within a black hole...if that makes sense. This corresponds again to the fact that time and space switch places. The diagram represents a simple black hole, an indefinite one: a Schwarzschild black hole. One that has always existed and will continue to exist. From the outside, we see a sphere/black hole suspended in time and assume a finite space within. But on the inside, the tables are turned. Time is finite. It starts at the horizon and ends completely and abruptly at the singularity.  But direction (space) is now infinitely long.

For this complex switch and turn of tables, it would be much harder to travel through a black hole as simply as Cooper and his scientists.

From the planetarium I learned that if you were to cross the event horizon, the switch would occur gradually. And it would actually cause your body to stretch in an uncontrollable manner. You would not be able to control the space around you. But you would be able to control time. Right now I can lift my arm at any pace. And I can look at the clock, and have no effect. Those two "powers" are opposite after crossing the event horizon.

Finally, from the outside of a black hole, time and space are as they usually are. So seeing someone cross and event horizon, nothing would seem different. I could wave at Bob inside of a black hole and he could look perfectly fine. When to him, time and space have switched spots, he is out of control and sees everything in continuously changing moments, without having any sense of space anymore.

Of course, black holes are all sorts of levels of complex. And Interstellar represents one that obviously has an end and beginning that can be travelled though. But in reality, humanity cannot likely move through black holes and find successes in a mission or even survive.

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Something (shorter) that I learned from the planetarium was about wormholes. I'd like to connect this to time travel. Where, in Interstellar, Dr. Cooper observed a form of time travel through the mysterious beings and the 5th dimension. He was able to interact with Murph through time travel only to be described beyond science.

But is time travel actually possible?

In theory, if one were to have some sort of a way of CONNECTING the singularities of two wormholes at their ends, one could plausibly enter one, and exit another in a different time. This would absolutely work, if it were possible, because think, you would be traveling over one warp in space time to meet another and travel over it BACKWARDS. Depending on the space along the wormhole, the time jump would differ. So we wouldn't have control of how much time we would travel across or back, but it's a cool idea to legitimately consider.

Just a thought for your next science fair project. Or in case you're bored or something.

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Justin --

The wave thing is mad cool. I like to imagine a surfer infinitely surfing on a wave rocking based on planetary motion. I also feel like I have to use that analogy to calm my fears of how horrifying the whole concept actually is...

Jake --

Same thing with the relativity concept, the live feed vs. video tape description was a perfect way to describe the concept. But it's scary! To calm my fears about this: I like to think of Skyping someone on the planet Miller. You'd think it was just taking forever to buffer. But it's actually just the fact that your partner is so close to a black hole that gravity is messing with how slow they are moving relative to ourselves. So no worries.

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One of the most important concepts in the movie, Interstellar, was the theory of relativity. And time, was a big factor in the movie. When the crew spent too much time on the water planet, Cooper was looking for a way to reverse it, asking if there was a way to reverse time. Of course we know that it is impossible in any way to go back in time, however I feel like the movie didn't stay true to that idea. When Cooper goes through the black hole he not only shakes Dr Brands hand but he also is able to influence a point in time that is at least 20 years. Also, they say that the wormhole they use to go to the other galaxy was put there by someone and they say it is humans. However, humans didn't have the ability to do that at the time meaning to put that wormhole there they must have gone back in time to do it. The movie doesn't stay true to the theory of relativity and I don't think it follows its' own physics.

Also, the way they manipulate gravity and the physics of gravity is interesting to me. I think gravity was set up to be "time" in the movie, that is why they are able to change gravity to influence time. Gravity is time in the movie, instead of being able to go back in time through the black hole and just tell Coopers daughter the answer to gravity, the movie uses gravity and 5th dimensional beings to influence gravity or as I see it, the space-time continuum. The physics in the movie are, in some places, made up. I do not think you can change gravity and I think Interstellar's ending wasn't realistic as you can't go back in time.

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One thing that i found interesting in Interstellar was the point made by Anne Hathaway's character that Mann's planet had less a chance at harboring life because the black hole it closely orbited it prevented too many accidents to happen that would start life. In reading Kip Thorne's Physics of Interstellar he goes through the physics of why this statement is very wrong.

The main point made by Thorne is that for something to be sucked into the black hole it has to be going right almost at it, otherwise the centrifugal force of say a passing comet would be strong enough to prevent it from being sucked in and instead would be placed in an orbit, just like Mann's planet, around the blackhole. The strong pull by the blackhole would pull many of such objects into the strange orbits like it did. These orbits are far from normal to our standards and are also more 3D in nature as they make almost spherical orbits such as shown below.

This also leads to the point that when they are in orbit around Mann's planet, which they had to travel a long way to get to, an explosion sends them directly into the blackhole so much that they are in danger of being pulled all the way into it. This is because of the nature of black hole orbits, Dr. Thorne made an orbit for Mann's planet which at one point is far away from gargantua and then later travels very close to the blackhole so that an explosion could plausibly send them into the grasp of the black hole. A depiction is shown below.

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Yet another interesting point from Interstellar was the ending, which many of us have avoided because of the fact that a 5th dimension is very confusing indeed. Now obviously the movie took some creative freedom in this scene but the physics behind the 5th dimension was plausible even though it was a stretch.

The idea was that Cooper was sent into the blackhole to be saved by the 5th dimensional beings using a tesseract of sorts. A tesseract is a 5th dimensional object, just as a cube is 3 dimensional or a square is 2 dimensional and so forth. The explanation for the object is that you "add" another dimension by adding on lines at 90 degrees. So from a point you add a line to get a line, then more to get a square, then again to get a tesseract. The only catch is that we cannot actually see a tesseract in its truest form in our 3, technically 4, dimensions, we can only see reflection of it. Just like if we draw a cube in 2 dimensions we can only see it's reflection, and you can't tell that the lines are added on perpendicularly. So in this 5th dimensional object they create a way to transport Cooper from his position inside Gargantua back to our galaxy while at the same time giving him the ability to view the 4th dimension (time) to save the earth.

This point is also interesting since the idea used in the movie for the 5th dimension, is that the "bulk" as it is called is wrapped around our universe, this means that the 5th dimensional beings can then travel into ours using the tesseract, even a blackhole, and save Cooper, transporting him back to safety in our own solar system.

There is ofcourse much more to this idea but this gives a good idea on the idea behind the 5th dimension in Interstellar. Included below is a picture of a tesseract (in our dimension).

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Rachael- I also thought the idea behind the changing of G was very interesting and how by mastering the impact of the 5th dimension on them they could influence it, also how when they did it the earth itself probably would have fallen apart like the crust and inner core from the change in gravitation.

Nate- Wormholes really blow my mind just imagine what we could do with them if we had them mastered, obviously the hole negative energy thing is a problem though, I wonder if we will be able to learn enough about dark matter or energy to solve this conundrum

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