Movie
Interstellar: Plot points explained
Let me start by saying I loved the move and rate it 5 out of
5. If you enjoy reading my technical
blog entries, then you’ll enjoy watching this movie. However, some of the movie can be hard to follow. Some people I watched the movie with had trouble understanding exactly what was going on and why people did what they did.
This is my attempt to identify and describe the plot points.
SPOILER ALERT: There be movie spoilers ahead!
Act I –
Pre launch
The
Blight
The plot
requires something to drive humans off the Earth. The movie doesn’t expend much screen time
explaining the problem but the premise is “the Blight” is an organism that
consumes nitrogen, depletes, oxygen, and can hop from one crop species to
another.
It is
implied the blight has been around for a while and that it has become
impossible to grow almost all crop species.
At the time the movie starts, humanity is down to just a few (possibly
one) food crop and by near the end of the movie, the survivors on Earth are
certainly down to just one crop corn.
The blight is also the reason food is in such short supply.
The
Messages
By the
end of the movie, Murph receives four messages from the future. The movie reveals by the end that all four
messages were transmitted by Cooper. The
messages (in chronological order in Murph’s frame of reference) are:
- Noise
(random books and the LEM thrown from shelf as Cooper laments and learns about
how to send messages)
- Latitude/longitude
coordinates of secret NASA facility (transmitted as binary and appearing in the
dust pattern on the floor)
- “S” “T” “A”
“Y” (starting letters of the book titles)
- Black
hole observation data (transmitted as Morse code into Murph’s watch’s second
hand movement).
Why Cooper
NASA originally had no intentions of using Cooper as a pilot. If he was as qualified as Dr. Brand states, then he should have been contacted as a possible pilot.
Given that NASA didn't attempt to contact him, then the only reason they accepted him as a pilot was due to the information that he received from (who everyone at the time thought was) "They". The fact that he had other qualifications sweetened the deal.
Note that pilots require constant training to stay in top form. A pilot who spent the last several decades farming (with no training) would not be the "best pilot they had".
The
Plans
As
described by Dr. Brand (Sr.), send Endurance through the wormhole to perform
follow-up observations on viable planet candidates, select one, and transmit
the information back to Earth. In Plan A,
this tells humanity where to set up its colony.
In Plan B, this tells humanity where to send any other spacecraft it can
send to land and will be the location of the colony established by Endurance.
Plan A –
NASA is constructing giant space station(s) to lift large numbers of living
humans from the Earth. (In my opinion, it is unlikely that plan A
could lift more than a tiny fraction of a percent of the entire Earth’s
population because they would still have to create enough spacecraft to support the remaining world population). But the concept is if Dr. Brand Sr. can solve the Theory of Everything
equation, it could be used to create anti-gravity engines, lift a large segment off the planet, and then if a viable
planet is found it could be colonized.
Plan B –
Endurance’s cargo includes 5000 fertilized ovum. Endurance is equipped with basic equipment
gear the ability to incubate and raise these eggs to adulthood. This is the
fall back plan if Plan A can’t be executed.
Act II –
the flight out
Sleepers
The crew
jumps into tanks filled with water and appear to go to sleep. Presumably, the tank sleep is a sort of
hibernation that reduces their consumption of on-board stores (power, air,
water, and food). Even without cryogenic
type hibernation and using something more like bear hibernation, the saved quantities
of these consumables can be substantial.
Wormhole
Nothing
in what we know of physics prevents the theoretical formation of wormholes as
depicted in the movie. However, there are many
practical problems in actually using one. The function this
wormhole served in the movie was it permitted humanity to travel vast distances in
small amounts of time.
The
wormhole is a necessary plot point because humans at the technology level
depicted had no chance of getting anyone alive to any habitable planet without
significant help.
The
relative time experienced by the people traveling through the worm hole may
have been affected but based upon receiving signals back from the initial 13 explorers;
this wasn’t a substantial amount of time. The actual physics of this is peculiar. If current theories are correct, a worm hole could (theoretically at least) connect any two locations in space. However, the theory also permits the connecting any two locations in time.
Time
dilation
It was
clear to the crew when they departed that the Earth would remain viable for
humanity for a minimum of years and possibly decades. By using time dilation they increase the
sense of urgency for the crew of the Endurance.
Furthermore, it allowed the movie to explore the stresses imposed upon
the relationships between the two fathers (Brand and Cooper) and their
daughters (Amelia and Murph).
How we
experience time is always relative and dependent upon the details of our relative
locations. Time dilates in regions close
to gravitational fields and for objects traveling close to the speed of
light. The effect is not normally large unless very large gravitation fields – like that of Gargantua are encountered at close range or very high fractions of the speed of light are experienced. Effects as large as that portrayed for Miller's planet require the black hole to have very special properties (e.g. rotating at 99.8% of c).
Miller’s
world’s proximity to and orbited around Gargantua generated a huge time
dilation (7 years pass in the rest of the universe for every hour spent on
Miller’s world). Mann’s world also
orbited Gargantua but its time dilation was much smaller and not mentioned
during the course of the movie.
The effects at Mann's planet were probably noticeable but not substantial My total guess here but for every 1 minute on Mann's planet, perhaps 1 minute and 15 seconds passed for the outside Universe.
Furthermore, regions “far” from Gargantua (e.g. Edmund’s world), likely
experienced time similar to that encountered by the rest of humanity on Earth (i.e. almost none). There would be noticeable differences but they would not be substantial. Another total guess but for every 1 minute on Edmunds' world, perhaps 1 minute and 0.5 seconds passed for the outside Universe.
During the slingshot maneuver towards the end of the movie, Cooper steers the Endurance within the "critical orbit" of the black hole. My recollection of relativity and black hole mechanics from college (warning this is a 30 year old memory) suggests that the "critical orbit" is the closest stable orbit to the black hole. Going inside the critical orbit means falling into the black hole if thrust is not applied. However, this distance is considerably closer than Miller's planet and the time dilation experience would be considerably worse than that encountered at Miller's planet. Since I haven't worked out the orbits of the different planets, I can't tell you how much, however, many decades per hour could be passing.
However,
time dilation as depicted was accurately portrayed, even if how it was used was
not done very elegantly or believably.
Dr.
Miller’ Planet
Upon
landing Dr. Miller sent the message indicating her planet was viable for an
Earth colony. However, because of the
time dilation, the period of time between her sending the message and the landing of the Endurance crew was only about 90 minutes by her clock but over 10 years
by ours. The first wave she encountered likely
destroyed her base/lander, killed her, and destroyed her robot.
Miller's planet was investigated
by the Endurance crew because it was “energetically the easiest to get to” (as explained in the
dialog – but not reality). Dr. Miller
sent the “viable = true” message back to Earth.
The movie dialog implied the wave traveling away from the site upon
their touchdown was probably the wave that killed Dr. Miller.
Both Dr.
(Amelia) Brand and Dr. Doyle act irresponsibly and did not return to the Ranger
when directed to do so by Cooper (a Mission Commander should have been appointed prior to launch). Amelia ignored the order because she intended
to retrieve probe data. Doyle ignored the order because he was stunned and simply stood frozen in place. Doyle’s
inaction may have been due to his emotional attachment to Dr. Miller (based
upon his reactions when planet fall decisions were being made).
The
giant waves were generated by the massive tides from the planet’s rotation while
orbiting the supermassive black hole “Gargantua”. I’m told the waves were unrealistic large given the
other parameters of the planet (it would likely be tidally locked, shallow seas
wouldn’t provide the water necessary, the planet itself would warp under such
conditions, and generate massive amounts of internal energy would make the
planet uninhabitable).
Dr. Romilly’s
aging demonstrated first-hand how much time the trip to Miller’s planet cost as far as time passing back on Earth.
Dr. Mann’s
Planet
Dr. Mann
(Amelia Brand called him “the best of us all”) initially did not send the
signal indicating his planet was viable.
Later when faced with isolation and desolation he finally disabled his robot
KIPP and sent a signal indicating his planet was viable for humanity. Despite, it not possessing the requirements
to sustain a human colony.
He did
this because he became lonely and afraid of dying alone. He could not resist the temptation of the
thought that if he sent a message indicating his planet was viable, then the
crew of Endurance would come and rescue him (which is exactly how this played
out). Dr. Mann uses many
rationalizations to justify his behavior even though each of them fell apart
upon examination. Either his insanity or
ego overcame his wisdom so that he acted according to his own self-interests and
to the detriment of all humanity.
Presumably the explosion that killed Dr. Romilly was supposed to kill the entire crew of Endurance so Dr. Mann's betrayal and failure wouldn't be discovered. However, Amelia was already en route to save Cooper. Dr. Mann's betrayal (and killing of the robot KIPP) eerily mirrors HAL-9000's betrayal (and killing of Discovery's human crew) in the movie 2001: A Space Odyssey.
The irrationality
of Dr. Mann and the actions he takes damages the Endurance and force
the rescuers to thrust away from Mann’s planet.
This ultimately sends them on a trajectory towards Gargantua. Cooper calculates a trajectory which enables
the Endurance to reach Edmund’s planet after a close approach to
Gargantua. However, in order to reach
Edmund’s they must use Lander 1 and Ranger 2 as “booster rockets” to provide
the necessary trajectory changes.
The maneuver
used by Cooper to adjust their trajectory is plausible. Applying thrust (and discarding boosters) at
the bottom of a gravity well provides much more delta V (change in velocity)
then performing the same operations at the top of the gravity well could provide. It also allows the plot to drive Cooper to fall
into the black hole (which no rational and competent pilot would allow to
happen) but is necessary for the next act of the movie.
Plotwise, falling
into the black hole provides a plot loophole that enables Cooper to send messages back in time to Murph.
Dr.
Edmunds’ Planet
Dr. Edmunds
initially transmitted that his planet was viable for colonization. Years later, he stopped transmitting. The data he did transmit looked like it was the most
promising of all three planets investigated (Dr. Miller’s, Dr. Mann’s, and his);
however, the loss of signal worried the Endurance’s explorers and it took the most fuel to reach.
Dr.
(Amelia) Brand is in love with Dr. Edmunds and suspicion that her relationship
might cloud her reason causes Cooper to investigate Dr. Miller’s planet first.
The
movie reveals little about Dr. Edmunds' planet until the final scenes. Those depict the atmosphere as breathable and, therefore, that ecosphere as likely at a minimum supporting its
own primitive native life. This makes
Edmund’s world by far the most viable of the planets of those depicted.
Dr.
Edmunds presumably died in an accident while on the planet and not due to
anything that reduced the viability of it as a colony world for humanity. The final scenes of the movie show CASE digging up Wolf Edmunds' body, Amelia Brand burying Dr. Wolf Edmunds, and standing over his grave. The movie does not explain what happened to Dr.
Edmunds’ robot.
The Lie
Dr.
Brand (Michael Caine) reveals on his death bed that he lied about Plan A. In his deathbed confession, he states that he had solved his equations decades
before. He felt they provided no solution to humanity’s problems without
observational data from the inside of a black hole’s event horizon. Since by definition an event horizon prevents
any information from getting out, this was an impossible task and Dr. Brand (Sr.) “knew”
Plan A would never work. Instead of
revealing this to the rest of humanity, he kept his thoughts of the futility of
Plan A to himself to ensure humanity continued working together until the very
end.
Dr.
Brand expected the Endurance’s crew to find a viable planet and immediately
start the Plan B colony.
Act III
Added on 12/7/15:
Did Cooper need to fall into the Black Hole?
For several reason the answer is "Yes". Just after regaining control of the Endurance, TARS mentions that there is "good news" and "bad news". Cooper asks TARS to "give it to him straight" but the scene ends before the audience hears the news. Cooper discusses the plan with Amelia Brand and mentions that he's found a trajectory around the black hole that allows them to "scratch their way to Edmunds' planet". He refers directly and indirectly to both fuel and life support.
The plan requires the additional thrust of two of the ancillary craft ("Lander 1" and "Ranger 2"). The plan states that Lander 1 will detach (like a booster rocket) from the craft after expending its fuel. Since the control linkages between Endurance and these craft was damaged by Dr. Mann, each craft must be crewed.
The chosen pilots for the ancillary craft are TARS and Cooper. To Dr. Brand's surprise, Cooper ends up detaching for the same reason that TARS did.
In summary, the reasons are:
- Endurance, Lander 1, & Ranger 1 each requires a pilot
- Only enough life support on Endurance for 1 human to survive to Edmunds' planet
- Only enough fuel for this single trajectory
- Last but not least, the plot requires Cooper to fall into the black hole
The black
hole
Little
about the black hole scenes is explicitly explained. But observation and piecing together other
bits of plot we can derive the following conclusions
- “They”
are not bound to our four dimensions (they are often referred to as five
dimensional, but that is the minimum, they could exist in more)
- “They”
are not trapped by the gravity of a black hole or its event horizon
- “They”
are able to manipulate gravity (although depending upon interpretation they
might not be able to manipulate time)
- “They”
are able to manipulate dimensions
- “They”
rescue Cooper as he falls into the black hole
- “They”
either refuse to or can’t communicate in a meaningful way with humans
- “They”
make a 4-dimensional construct (tesseract) to represent time as a fourth spatial dimension. This enables Cooper to view and interact with
Murph’s bedroom at any point in time
- “They”
rely upon Cooper to figure out what message to send, how to send it, and to
what time it should go
- At no time does matter move back in time, even though information does
Cooper
uses this ability to send the four messages back to Murph. In Cooper’s frame of reference, he sends the
messages in this order:
- Noise (random books and items knocked off the shelf)
- “S” “T” “A”
“Y” (first letter in the title of the books he knocks off the shelf)
- Latitude and longitude coordinates for secret NASA facility sent in binary (in dust settling to the ground)
- Black hole observational data sent in Morse
code (in the movement of the watch he gave to Murph).
Black
hole –
When the
average person discusses a gravitational slingshot, they discuss it in a
generic way and do not differentiate between several distinct effects that change
a spacecraft’s momentum when passing close to another object.
Oberth
Effect
The
first of these effects is the Oberth Effect. Simply stated, you get a greater
change in momentum of you apply your thrust at the bottom of a gravity well
than at the top. Read the article for
the details about why this is true. The
Oberth Effect applies for any object orbiting any other object (a two body
problem). The movie accurately portrays
Cooper using the Oberth Effect to place Endurance on the correct trajectory
towards Edmund’s planet.
Gravity
Assist
The
second of these is the Gravity Assist. Simply stated, in a three body system
– Body A can exchange momentum with Body B to increase or decrease its momentum
relative Body C. An example would be the
Voyager 1 & 2 flybys of Jupiter. In
each case, the spacecraft vastly increased their momentum (velocity) in
relationship to the Sun by slowing Jupiter an unmeasurable amount in its orbit
around the Sun. In the case of the movie
Interstellar and Endurance’s fall towards Gargantua, Endurance does not receive
any gravity assist benefit from the maneuver. In the case
of Endurance’s flyby of Mars (retrograde trajectory), this would remove velocity
from Endurance’s Sun centric (body C) momentum and make the trip longer which
is a “bad idea”.
Turn
The
third of these is a simple turn. Simply
stated, in a two body system, when a spacecraft wants any change in vector,
than it must transfer momentum with something to accomplish the maneuver. If no nearby masses are available than the
spacecraft must use its own engines to provide the momentum change and this
would be very costly in propellant.
In the
case of Endurance trying to reach Edmunds’ planet, they were headed in the
wrong direction and needed to make a turn.
If Cooper chooses the correct trajectory towards Gargantua and makes the
right course correct when near Gargantua, he can effectively choose whatever
outgoing trajectory he desires – namely the course towards Edmund’s planet. The movie accurately portrays Cooper using
Gargantua to change Endurance’s trajectory towards Edmund’s planet.
The difference between a turn and a gravity assist: in both cases Body A exchanges momentum with Body B. In the gravity assist, the exchange is done in a special way to increase Body A's velocity / momentum / energy in regards to a third body (Body C).
Tidal Effects
Sufficiently massive black holes (such as "Gargantua") have smaller tidal effects above the event horizon. This would enable sufficiently small objects (such as a person) to pass through the event horizon without being "speghettified/speghettification" or tidally disrupted (a more tidy way of describing recursively being ripped apart).
Tidal forces vary linearly with mass but as the inverse *cube* of distance. The size of the event horizon varies linearly with mass only. Meaning their is a black hole mass which allows human sized objects to pass through the event horizon without disruption.
So smaller black holes would disrupt human sized objects prior to their reaching the event horizon. Large enough ones allow smaller objects to pass through the event horizon prior to recursively being ripped apart.
Meaning Cooper could have survived passing through the event horizon.
Act IV –
Cooper’s
survival
Humanity
rescued Cooper with “only minutes of oxygen left”. How did Cooper survive for so long in
space? He didn’t. Cooper’s time dilation meant he had only been
on the Earth side of that wormhole for a few minutes. Cooper essentially spent 90 years on the
other side of the wormhole and just happened to pop out right as humanity got
to Saturn.
Was Cooper just lucky or was it careful planning by “They”? The answer is open for interpretation but I
think the movie was going for ‘careful planning by “They”’.
Cooper’s
recovery
The doctor
tells cooper he’s 123 years old. Assume
he started his mission at the age of 33 and they spent 23 years on Dr. Miller’s
planet, what happened to the other 67 years?
Time dilation, that’s what. It
also means that Cooper did not pass through the event horizon as his time
dilation would have then been measured in billions/trillions of years rather
than decades.
Cooper’s
departure
Murph
urges Cooper to depart and find Brand.
Partly for Cooper’s sake (he doesn’t relate to post-Earth humanity
anymore) and partly for Amelia’s sake she believes that she is the only
surviving human in the entire universe.
She’s alone and isolated on Edmund’s world. She has also been left with the burden of resurrecting
the human species by herself. Murph
correctly (IMO) believes that the company of just one other human would help
Brand immensely.
During
these scenes the movie jumps back and forth between Cooper and Brand indicating
their actions occur simultaneously (with black holes, worm holes, and time dilation; what does
this even mean??).
The
problem I see is this: cooper loses 67 years while performing the trajectory
change in Endurance, falling into the event horizon, and while in the “They”
tesseract. Amelia shares the time
dilation experienced by cooper during the trajectory burn but from there Amelia
experiences time at an accelerated rate while Cooper’s slows down. Amelia will have experienced a large chunk of
those 67 years that Cooper missed (40 years or more?).
If/when
Cooper finds Amelia she’ll be in her 70s if she survives.
Unanswered questions
Where is
humanity going?
A question
not posed in the movie but it is implied.
Murph tells Cooper to go to Brand.
If humanity intended to colonize Edmund’s world (Amelia's location), why would he need to do
that? Clearly the difference between
when Cooper could get there and when the rest of humanity appeared would be
minimal (weeks perhaps?). This tells us that
post-Earth humanity has no intention of colonizing Edmunds’ world and, without Cooper returning to her, Amelia would truly
be alone.
I wonder,
where does post-Earth humanity intend to go?
Added 12/7/15
Did Cooper succeed in getting to Amelia Brand?
Based upon the size of the craft, I assume it had neither the delta V nor the life support that the Endurance had. However, I also assume Cooper and/or TARS new the approximate requirements and would not have made the attempt if it was unlikely to succeed.
Added 12/7/15
Will humanity now have two colonies?
Assuming both Amelia Brand's colony and the rest of humanity succeed in forming viable colonies, then humanity will have seeded two separate galaxies. It's unlikely that the two populations would ever meet unless / until they develop the ability to form wormholes like "They".
Do you have any questions about the movie Interstellar? Ask them in the Comments section.
