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Kip Thorne: The science of Interstellar

blogs.scientificamerican.com

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Re: Kip Thorne: The science of Interstellar

#51

Post by Leszek »

chton wrote: post #5
gglon wrote: post #4

Earlier quoted context omitted.

The movie shows other cases where it doesn't follow its own rules: they have spaceplanes that can get to orbit from a planet with 1.8 times earth gravity, but not from earth without huge boosters? Normal fuel is just less expensive.

That's a possibility, but the special fuel they have would have to have been extremely expensive then. That would have been a fine explanation, and if they had mentioned it in the movie that would be one less point I could make. But here's another one: They set up this nice system with pings to know what planets might be suitable, but they can't detect when a ping is being repeated instead of actually sent by a perso…

What I didn't understand about these pings is wouldn't their wavelength be massively lengthened by the time dilation? How did they even receive Miller's signal if it was redshifted ~60000 times?

Re: Kip Thorne: The science of Interstellar

#52

Post by lqdc13 »

chton wrote: post #40
lqdc13 wrote: post #32

Earlier quoted context omitted.

Wait what? What about sending "quantum data" back from the black hole? The point is that no information can leave. Also, from what I learned in high school physics, the body of a human would completely fall apart if it's falling to the black hole, because of the difference in gravity between proximal and distal parts. These are just the 2 things I noticed and I'm far from a physicist. Basically, it got a couple of th…

I don't know why you're being downvoted, so I'm going to give you a proper reply instead. Actually, the 2 things you noticed are not that hard to resolve: - The quantum data was most likely never going to get out of the black hole. They executed the plan on the off chance that TARS was able to figure out how to do it if he had the quantum data. It's not impossible that there is a way to do it, we just don't know it y…

Wouldn't spaghettification happen anyway, but at a later point? Maybe everything after he fell in was a dream of his? This would actually make it much more interesting for me although many people probably wouldn't like this sort of ending.

Re: Kip Thorne: The science of Interstellar

#53

Post by max55 »

ThePhysicist wrote: post #17

Accuracy aside, from a scientific point of view Interstellar was one of the most interesting movies in a long time, and it really made me think about Physics a lot again. It's really cool to see how much you can actually learn about the universe of Interstellar by making use of some Physics knowledge and the information given to you in the movie. An example: The first planet they visit orbits Gargantua (the supermass…

Remember a black hole will crush a galaxy, but not a dude in a space suit.

Re: Kip Thorne: The science of Interstellar

#54

Post by bestpcinfos »

max55 wrote: post #53
ThePhysicist wrote: post #17

Accuracy aside, from a scientific point of view Interstellar was one of the most interesting movies in a long time, and it really made me think about Physics a lot again. It's really cool to see how much you can actually learn about the universe of Interstellar by making use of some Physics knowledge and the information given to you in the movie. An example: The first planet they visit orbits Gargantua (the supermass…

Remember a black hole will crush a galaxy, but not a dude in a space suit.

Don't forget to put the tarp over the ham basin before departing for olfactory shoes.

Re: Kip Thorne: The science of Interstellar

#55

Post by chton »

lqdc13 wrote: post #52
chton wrote: post #40

Earlier quoted context omitted.

I don't know why you're being downvoted, so I'm going to give you a proper reply instead. Actually, the 2 things you noticed are not that hard to resolve: - The quantum data was most likely never going to get out of the black hole. They executed the plan on the off chance that TARS was able to figure out how to do it if he had the quantum data. It's not impossible that there is a way to do it, we just don't know it y…

Wouldn't spaghettification happen anyway, but at a later point? Maybe everything after he fell in was a dream of his? This would actually make it much more interesting for me although many people probably wouldn't like this sort of ending.

It would happen, but for a black hole massive enough, that point would be well inside the event horizon. We don't know how deep they actually went into the black hole, or even whether or not the 4D structure was inside the black hole or somewhere else entirely. Everything inside the event horizon is essentially unknown to us, both as scientists and as movie-goers, but the trip up to that point is survivable.

Re: Kip Thorne: The science of Interstellar

#56

Post by koepked »

m_mueller wrote: post #36
TorKlingberg wrote: post #27

Earlier quoted context omitted.

I also love the movie, but there one thing with the time dilation I suspect does not add up. If the first planet is so deep into Gargantua's gravity well that it has such time dilation, would the energy required to get a spaceship out of the gravity well not be ridiculously huge? Given that they had limited energy, did it make sense to visit that planet first?

The thing about their energy budget was not well done. Why did they need rockets back on earth when they can mount the gravity well of a black hole and multiple planets afterwards? About your point with the order of visits though: I could see them using Gargantua for a slinghot maneuver after the first planet, which should work given the right constellation. It wasn't shown this way though.

Even with a ship capable of overcoming the gravity wells present in the movie, it would likely still make sense to launch from Earth with boosters/staging to increase the amount of fuel/energy available to the ship for the rest of the journey.

Re: Kip Thorne: The science of Interstellar

#57

Post by harshreality »

ThePhysicist wrote: post #44
harshreality wrote: post #29

Earlier quoted context omitted.

It's a supermassive black hole, spinning at close to the maximum permitted (apparently there's a maximum, beyond which photons at either the photon sphere or an event horizon get dragged faster than the speed of light, and Gargantua's spin is ridiculously close to the maximum for the math on the orbit and time dilation to work out, but it does) If you can find a copy of Thorne's book (it's already leaked to the web)…

A relativistically spinning supermassive black hole might not be very unrealistic indeed, since it will have ingested the angular momentum of a whole galaxy during its growth and concentrated it in a very small region of space.

He addresses that in the book

> I found that Chris’s huge slowing of time requires Gargantua to spin almost as fast as the maximum: less than the maximum by about one part in 100 trillion. In most of my science interpretations of Interstellar, I assume this spin.

> In 1975, I discovered a mechanism by which Nature protects black holes from spinning faster than the maximum: When it gets close to the maximum spin, a black hole has difficulty capturing objects that orbit in the same direction as the hole rotates and that therefore, when captured, increase the hole’s spin. But the hole easily captures things that orbit opposite to its spin and that, when captured, slow the hole’s spin. Therefore, the spin is easily slowed, when it gets close to the maximum.

> Ultimately, when the hole’s spin reaches 0.998 of the maximum, an equilibrium is reached, with spin-down by the captured photons precisely counteracting spin-up by the accreting gas. This equilibrium appears to be somewhat robust.

In essence, the necessary spin (for an object to stably orbit at a distance for the time dilation needed for the plot), while possible, is not sustainable, based on what we know about physics. But it's allowable as real physics, because there could be some exotic physics involved in keeping Gargantua spinning that fast, possibly intervention by the civilization that created the tesseract.

Re: Kip Thorne: The science of Interstellar

#58

Post by chton »

Leszek wrote: post #51
chton wrote: post #5

Earlier quoted context omitted.

That's a possibility, but the special fuel they have would have to have been extremely expensive then. That would have been a fine explanation, and if they had mentioned it in the movie that would be one less point I could make. But here's another one: They set up this nice system with pings to know what planets might be suitable, but they can't detect when a ping is being repeated instead of actually sent by a perso…

What I didn't understand about these pings is wouldn't their wavelength be massively lengthened by the time dilation? How did they even receive Miller's signal if it was redshifted ~60000 times?

That is an excellent point, I didn't even consider that. It's possible they were listening on the correct frequency to receive it, since they knew the redshift was going to happen, but that just leaves more questions as to why they didn't then realize that it definitely couldn't repeat.

Re: Kip Thorne: The science of Interstellar

#59

Post by rufb »

ThePhysicist wrote: post #39
lqdc13 wrote: post #32

Earlier quoted context omitted.

Wait what? What about sending "quantum data" back from the black hole? The point is that no information can leave. Also, from what I learned in high school physics, the body of a human would completely fall apart if it's falling to the black hole, because of the difference in gravity between proximal and distal parts. These are just the 2 things I noticed and I'm far from a physicist. Basically, it got a couple of th…

That's an interesting point! The fact that our current theories suggest that no information can ever leave a black hole entails a paradox which is known as the "Black hole information paradox" ( https://en.wikipedia.org/wiki/Black_hole_information_paradox ). In the movie they resolve this by resorting to gravitational waves, which can "permeate" through space and time by a mechanism not explained in the film. In real…

They glossed over the tidal force in the movie and I assumed it was a deus ex of sorts (in fact, I assumed the whole final act of the movie was more concerned with resolution of the story than with proper Physics). Thank you for this explanation, this is fascinating stuff.

Re: Kip Thorne: The science of Interstellar

#60

Post by nilkn »

lqdc13 wrote: post #32
ThePhysicist wrote: post #17

Accuracy aside, from a scientific point of view Interstellar was one of the most interesting movies in a long time, and it really made me think about Physics a lot again. It's really cool to see how much you can actually learn about the universe of Interstellar by making use of some Physics knowledge and the information given to you in the movie. An example: The first planet they visit orbits Gargantua (the supermass…

Wait what? What about sending "quantum data" back from the black hole? The point is that no information can leave. Also, from what I learned in high school physics, the body of a human would completely fall apart if it's falling to the black hole, because of the difference in gravity between proximal and distal parts. These are just the 2 things I noticed and I'm far from a physicist. Basically, it got a couple of th…

I'm not going to comment on the "cosmic censorship" hypothesis of black holes since that's actually an incredibly difficult topic, but regarding the tidal forces that would rip you apart, there are certainly large enough black holes that would allow you to comfortably enter the event horizon without being ripped apart. But just to give you a taste of how counter-intuitive this subject can be, consider that despite the fact that light cannot escape a black hole it is conjectured (by Hawking no less) that black holes can emit radiation! (The mystifying mechanism of this involves, very roughly, quantum fluctuations at the event horizon spontaneously giving rise to particle/anti-particle pairs, with one particle of negative mass falling into the horizon and the other of positive mass going out.)

The event horizon is only the "point of no return" insofar as it's the imaginary boundary inside of which even the forward light cones are oriented towards the center of the sphere (so that light cannot escape no matter what direction it's emitted in). It's not the point at which the tidal forces are so strong that matter is ripped apart (or even just your macroscopic body).

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