[MAJOR SPOILERS!] Newton's Third Law (Interstellar Related)

[EzinX]

You're missing the point.

Think about that: He had a small lander and (by some miracle) ended up on a decaying orbit to the black hole. I doubt anything he could possibly be on could last less than several months (and most likely we're talking about millenia here) before he'd get anywhere past the event horizon. But in a movies it's a blink of an eye, no starvation, no problems with lack of water, no... anything. Simply put: this guy is dead long before reaching the black hole in that sequence.

Ok, as I understand it, black hole time dilation is only relative to external observers.

If you are riding a spacecraft into a black hole, from your perspective you are approaching a supermassive object and getting ripped to shreds in a few minutes or hours (depending on your approach speed)

From the perspective of external observers, it takes years for you to get shredded to pieces.

If the black hole fails to shred you because godlike entities have tampered with it...well...the same argument still applies, no matter how unlikely the existence of said entities may be.

[Sampa]

So I watched Interstellar yesterday and near the end of the movie they are using the Black Hole to slingshot around in a powered gravity assist. This part doesn't bother me. What I'm curious about, is during the burn they detach two smaller ships (One lander and one crew transfer vehicle) with the main character stating "Newton's Third Law: Can't get anywhere without leaving something behind."

This bugs me because I fail to see how dropping the extra weight changes anything other than the dV of the remaining craft, which from the context of the scene is irrelevant since it is implied that they have enough fuel to get where they are going. Could someone please clarify this please?

Rule number one of watching science fiction film...it's Hollywood! Don't look into it! You're NOT supposed to look into it. Also, having not watched the film, I can only presume that they were trying to save the fuel for some breaking manuever later down the line

[SpaceXray]

Ending of a movie is ......... Just move on.

(BTW: You got one moment right, but there's another thing off with that scene: They turned off the engines, detached the ships, and.... ships flew backwards! hahahaha, it's more stupid than a scene in Gravity when they Bullock cuts off Clooney - that one at least can be explained with centrifugal force.)

Your logic is very flawed. The Endurance was still acclerating with the main engines(plus the Ranger), so when the Lander detached, it just "fell off" like a booster detaches from a rocket. The rocket is still accelerating, but the booster( in this case, the Lander) is not. The camera is following the Endurance, so it looks like the Lander just falls down.

[Windspren]

But if the super-advanced beings were capable of constructing a time machine/physics defying black hole, then why couldn't they just saved earth's atmosphere with some clever biology?

[SpaceXray]

In entire US, a country that just build a mega-starship on the orbit using godawful powerful rockets, noone ever "been out of the simulator"? Yea, right, I call that: Total BS.

Just like this thing with super heavy launch vehicles being launched in secret, secret NASA that noone knows about, an office with a moving wall opening right into the launch silo where they are still welding something to the engines, sending crew to the most risky mission in a human history where noone but one guy ever "been out of the simulator", or the fact that they had to manually dock with the space station - station that obviously had it's assembly had to be done by people, as otherwise they'd have automated docking systems for years, perfected enough to accomplish extremely complex and large scale orbital construction effort (automatic docking of a manned ship is a piece of cake comparing to automated assembly of something in that size on an orbit).

Just put an X-wings there, and get over it. Or Star Trek teleportation devises. It'd make more sense than this whole affair in the movie. Nothing makes sense there. It's nonsense on top of nonsense on top of nonsense. I liked this movie, I really did, but trying to call it as a masterpiece of realism like many people do (not you, but in general) makes me laugh.

[snip]

Now, let's start from the VERY beginning:

About the Lander "dropping for no reason like in Gravity(stupid movie according to you)", refer to my other post or any other.

About the ship dis-balance: it is not clear how exactly the pods detach from the Endurance and how they affect the CoM. Remember, that it's structure is not limited to these modules, and that they can moved around in many ways, and the ships can be re-located in many ways.

Remember, that RL is not like KSP. The Endurance engines don't work like they do in KSP. Every engine ignition is a risk. Thrust level control adds huge complexity to the engine itself and makes it more prone to damage.

During the Gargantua scene, you can hear the Endurance constantly firing RCS thrusters to stabilize itself(listen very carefully during the segment after the Ranger engines shut down).

So the explanation is: Endurance was using RCS to stabilize itself during the maneuver.

About NASA being so secret: every rocket launch was risky, since someone could see it. Taking a Ranger out to train the recruits is a larger risk since it flies a lot more horizontally and whereas a rocket dissappears in less than a couple minutes, a Ranger has a very long flight path, easily detectable by others. The manual docking by Doyle was not explained. yes, there was little reason for him to do the docking manually. It was mostly for drama, because, once again, this is a movie, just like Star Wars.

Edited April 7, 2015 by Vanamonde

[Greenfire32]

All I'm going to say is that Interstellar (ending included) didn't pull me out of the "realism" like Gravity's Clooney-death-scene did.

I liked both. I thought both were pretty well grounded in reality.

But I liked interstellar more. And that's ALL I'm going to say on the subject.

[AngelLestat]

Aside from someone magically save Cooper out of the black hole, which I doesn't understand at all, there is a very slight possibility to use rotating black hole as an energy source:

A rotating black hole might provide additional assistance, if its spin axis is aligned the right way. General relativity predicts that a large spinning mass produces frame-draggingâ€â€close to the object, space itself is dragged around in the direction of the spin. Any ordinary rotating object produces this effect. Although attempts to measure frame dragging about the Sun have produced no clear evidence, experiments performed by Gravity Probe B have detected frame-dragging effects caused by Earth.[11] General relativity predicts that a spinning black hole is surrounded by a region of space, called the ergosphere, within which standing still (with respect to the black hole's spin) is impossible, because space itself is dragged at the speed of light in the same direction as the black hole's spin. The Penrose process may offer a way to gain energy from the ergosphere, although it would require the spaceship to dump some "ballast" into the black hole, and the spaceship would have had to expend energy to carry the "ballast" to the black hole.

I don't know if this is right or not, its from here: http://en.wikipedia.org/wiki/Gravity_assist

And of course the good old Oberth effect helps

THIS...

Is explained in the Kip Thorne Book, I dont remember the details.

[Superfluous J]

But if the super-advanced beings were capable of constructing a time machine/physics defying black hole, then why couldn't they just saved earth's atmosphere with some clever biology?

Or at least sent back the message that it took this whole movie to put Cooper into the position to send?

All-powerful aliens (or future humans) not doing everything in their power to reach their goal and instead setting up complicated rigmaroles for the main characters to blindly fumble through is a long tradition in Hollywood.

[AngelLestat]

Or at least sent back the message that it took this whole movie to put Cooper into the position to send?

All-powerful aliens (or future humans) not doing everything in their power to reach their goal and instead setting up complicated rigmaroles for the main characters to blindly fumble through is a long tradition in Hollywood.

Your same question (Why Make It So Difficult?) is explained here:

https://www.psychologytoday.com/blog/plato-pop/201411/interstellar-causal-loops-and-saving-humanity

[bobskythecanadianguy]

Don't all black hole orbits decay though? As you approach c, your momentum must stay the same, so you gain mass instead of velocity when accelerating (because adding velocity would put you over c). Therefore, wouldn't dropping the landers give it a boost regardless of anything else?

[BlueCosmology]

Don't all black hole orbits decay though? As you approach c, your momentum must stay the same, so you gain mass instead of velocity when accelerating (because adding velocity would put you over c). Therefore, wouldn't dropping the landers give it a boost regardless of anything else?

That isn't true. Momentum increases without bound as a massive particle approaches c. The concept of "gaining mass" in terms of relativity is very misleading, and usually used completely incorrectly because of how misleading it is. Relativistic mass as it is known, is purely a way to make some newtonian formulae still work in the relativistic limit. However, many of the formulae do not work even with relativistic mass, and more important relativistic mass is not mass, in how mass is defined (i.e. gravitational charge and resistance to motion) you should really avoid ever talking about relativistic mass, as even Einstein concedes even though he originally came up with the concept of relativistic mass. There is no meaningful definition of relativistic mass, and using also makes other concepts lose their meaning such as acceleration.

Einstein 1948 "It is not good to introduce the concept of the mass of a moving body for which no clear definition can be given. It is better to introduce no other mass concept than the ’rest mass’ m. Instead of introducing M it is better to mention the expression for the momentum and energy of a body in motion."

Droping the landers would give it a boost if it fired the landers off, however as it just drops them (i.e. lets go and lets the tidal force of the black hole take them) there is no increase to it's velocity, the momentum of the total system remains constant.

There are also many stable orbits for black holes, all precess (i.e. their closest point to the black hole rotates over time) but they are still stable. For a non rotating non charged black hole the closest stable orbit is 3/2 times the event horizon.

[AngelLestat]

For a non rotating non charged black hole the closest stable orbit is 3/2 times the event horizon.

Which is the photon sphere.

[Xannari Ferrows]

This movie is cool, but downright impossible. First off, the fourth dimension. Be careful with that stuff.

Second, they seemed to have an awful lot of Delta-V. Go check the movie again. I mean, come on. Radially changing your trajectory against a black hole?

And I'm pretty sure you would be nothing but a noodle after making it to the singularity. And how'd he even get there in the first place? Wasn't he on a flyby trajectory? MAybe I'm remembering incorrectly, I don't know, but this is crazy.

[BlueCosmology]

This movie is cool, but downright impossible. First off, the fourth dimension. Be careful with that stuff.

Second, they seemed to have an awful lot of Delta-V. Go check the movie again. I mean, come on. Radially changing your trajectory against a black hole?

And I'm pretty sure you would be nothing but a noodle after making it to the singularity. And how'd he even get there in the first place? Wasn't he on a flyby trajectory? MAybe I'm remembering incorrectly, I don't know, but this is crazy.

They were (fairly accurately) representing the four dimensions of spacetime very well. I assume you're talking about 'the fifth dimension', which they also didn't do badly. It's not difficult to generalize things to more than the four dimensions of our universe, and their representation of it was pretty consistent, they simply had a fifth dimension that represented time but spatially.

A lot of the things they had to do in terms of orbits seemed very off, but not what you're saying. They required huge boosters to leave Earth, but didn't to leave the other planets that had higher surface gravities than Earth, which is clearly wrong. However changing your radial trajectory with respect to a blackhole is not something that requires a lot of Energy, things that are done in our solar system (e.g. gravitational slingshots) are pronounced very strongly in high field areas around blackholes, it does not take a lot of energy to change an orbital trajectory into an escape velocity or otherwise.

He never simply made it to the singularity in the film, after he passed the event horizon he traveled into the fifth dimension that the film had set up. The blackhole was meant to be a supermassive blackhole, and very massive blackholes such as this do not have huge tidal forces at the event horizon and hence wouldn't spaghettify.

Unlike in Newtonian physics where no capture orbits exist, capture orbits do exist in general relativity (the effective potential has an inverse cubic term with respect to distance, unlike in newtonian where there is only an inverse term and inverse square term, resulting in higher deviations of trajectories due to gravity at close range in general relativity) and hence a flyby can be captured.

Edited April 20, 2015 by BlueCosmology

[ZetaX]

Unlike in Newtonian physics where no capture orbits exist, capture orbits do exist in general relativity (the effective potential has an inverse cubic term with respect to distance, unlike in newtonian where there is only an inverse term and inverse square term, resulting in higher deviations of trajectories due to gravity at close range in general relativity) and hence a flyby can be captured.

Are you assuming the central body to be rotating¿ Otherwise I don't think this is true (the argument would be along the lines of: the invariance of everything under time reversal and symmetry of space shows that everything flies out again, the orbit being symmetric along an axis) and would thus be interested in more formal verfications.

[BlueCosmology]

Are you assuming the central body to be rotating¿ Otherwise I don't think this is true (the argument would be along the lines of: the invariance of everything under time reversal and symmetry of space shows that everything flies out again, the orbit being symmetric along an axis) and would thus be interested in more formal verfications.

No, though capture orbits do ofcourse exist in rotating black holes as well as stationary ones. Time reversal does not work that simply in curved spacetime. In a blackhole all directions in spacetime point towards the singularity of the blackhole, hence time reversal still results in travelling towards the singularity.

The 3 types of orbit, including capture, around a non rotating non charged black hole are shown in this http://www.astro.ex.ac.uk/people/sing/Notes/14.SchwarzschildSpacetime_Orbits.pdf.