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Interstellar meaning: Here's what actually happened in the Matthew McConaughey movie

No need for a degree in astrophysics - we'll break down Interstellar's mind-bending ending down below.

Matthew McConaughey
Published: Sunday, 19th June 2022 at 8:00 am
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From Inception's multiple dream layers to Tenet's time reversal, director Christopher Nolan is no stranger to mind-bending films.

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Interstellar is no different, turning his attention to space travel and pushing the concept to its extreme with one key difference - the events of Interstellar might just be physically possible.

Released in 2014, the iconic film stars Matthew McConaughey and Anne Hathaway as astronauts who travel through a wormhole in order to find a new home for humanity before Earth becomes uninhabitable.

Given that the film was based on the work of Nobel Prize-winning theoretical physicist Dr. Kip Thorne, it's no surprise that Interstellar's exploration of black holes and the fifth dimension can get a tad confusing at times.

We'll break down the film's plot and meaning for all of the non-astrophysicists out there - so it goes without saying that there will be some rather in-depth spoilers below!

Interstellar plot

Before we get into the nitty-gritty details, a reminder of Interstellar's complex plot may well be worthwhile.

When Earth becomes uninhabitable and humanity faces extinction, farmer and ex-NASA pilot Joseph Cooper (Matthew McConaughey) pilots a ship of scientists and engineers through a wormhole to find a new habitable planet in another galaxy.

NASA had previously sent astronauts through the wormhole to twelve potential worlds as part of Project Lazarus, with three reporting potential that would be investigated by this team.

NASA had two plans:

  • Plan A: Cooper finds a new home planet for humanity. NASA constructs large space stations capable of transporting most of humanity, and Professor Brand (Michael Caine) solves the gravity equation that allows them to launch.
  • Plan B: Cooper establishes a colony on another world using frozen fertilised eggs.

When does Interstellar take place?

Interstellar does not give an exact date for when events take place, but appears to begin in the not-too-distant future after Earth has started to fail.

During the amateur baseball scene Cooper's father-in-law Donald (John Lithgow) reveals that he remembers watching professional baseball as a child, suggesting that Donald's youth took place before the environmental catastrophe when there were enough resources to devote to the baseball industry.

Cooper then replies that people were too busy fighting over food to play baseball during his youth, suggesting that food shortages and societal collapse took place between these generations.

Therefore the events of Interstellar take place at least a few generations or around 50 years after the present day, suggesting a late 21st-century setting.

At least another 70 years then pass during the course of the film thanks to the time dilation of various planets, bringing the movie's final scenes to the early 22nd century.

This is just a rough estimate, however - like many elements of Christopher Nolan's films, this particular detail is left intentionally ambiguous.

For those desperate for a date however, Kip Thorne's tie-in book The Science of Interstellar states that the wormhole appeared in 2019. During the NASA conference scene, it is stated that the wormhole was first seen 48 years ago - which would mean the film begins in 2067.

What was the problem with Earth in Interstellar?

There's no world-ending asteroid or sudden apocalyptic event here - instead Interstellar goes for a less cinematic but far more likely reason for Earth to become uninhabitable.

The main villain of Interstellar is arguably crop blight, a disease that leads to the browning and death of plant tissue, leading to food shortages and fierce competition for resources.

Professor Brand explains how wheat and okra have both succumbed to the disease, and even though most of Earth's population has turned to farming to grow the one remaining crop - corn - it is only a matter of time before that too meets the same fate. Look closely during eating scenes - you can see characters only eating corn-based products, including cornbread and popcorn.

Earth's atmosphere is around 80% nitrogen which we humans cannot breathe - but blight does. As blight continues to thrive and devour plants, the air will receive less and less oxygen and as Brand succinctly puts it "the last to starve will be the first to suffocate".

All this leads to a perfect storm to wipe out humanity, with resources not predicted to last past Murph's generation.

It seems much of the world is suffering also from dust storms, which we see leads to respiratory illness in Tom's children. Nolan was inspired by the Dust Bowl of 1930s America, and the interviews seen at the beginning of the film are real-life accounts from the Ken Burns documentary The Dust Bowl.

Interstellar wormhole explained

When Cooper enters the secret facility that turns out to be NASA, it is revealed that a wormhole has appeared near Saturn.

A wormhole is a theoretically possible structure based on Einstein's general theory of relativity, and acts by bending spacetime to bring two disparate points together. Romilly neatly explains the concept in the film by pushing a pen through a folded piece of paper - the exact same method used in cult horror sci-fi Event Horizon.

The wormhole in the film is scientifically accurate - rather than the 2-D portal often shown in most media, a wormhole would be spherical in shape and show a distorted view of the target galaxy.

Who are "They" in Interstellar?

As Cooper states wormholes are not naturally occurring phenomena, and thus the wormhole near Saturn was placed there by someone - or something.

From then on these unknown beings are simply referred to as "they" and are assumed to be an ultra-advanced civilisation, likely hailing from the fifth dimension who conveniently placed the wormhole there to help save humanity.

However, Cooper speculates at the film's climax that these beings are not a "they" at all but rather a "we" - humans from the future who exist in the fifth dimension and therefore have easy access to travel through infinite time and space. It was these ultra-advanced humans who created the library "tesseract" that Cooper discovers in the black hole so that Cooper could then relay the data needed to save humanity.

How did 23 years pass while on Miller's planet?

Christopher Nolan sure loves messing with time - and the first instance of this occurring in Interstellar is when Cooper, Brand and Doyle leave the Endurance ship to investigate the water planet, now named Miller's planet.

Romilly explains that every hour on Miller's planet is equal to seven years on Earth due to a process called time dilation. This is because Miller's planet is close to a supermassive black hole called Gargantua. According to Einstein's theory of relativity, the larger the object the more spacetime is warped and twisted around it. Spacetime is warped around Earth for example, as atomic clocks at different altitudes have been demonstrated to show different times (only by nanoseconds however).

As Gargantua is significantly bigger than Earth - at around 100 million times the size of the sun - spacetime is warped considerably more, resulting in time passing more slowly relative to Earth. This is a rather extreme example, however - Thorne has stated in his book that Miller's planet was as close to Gargantua as it could get without falling in.

Cooper and Brand were on Miller's planet for 23 years, four months and eight days in Earth time - meaning they were only on Miller's Planet for roughly three hours and seventeen minutes. Listen closely to the ticks during the Miller's planet scene - they occur around every 1.5 seconds, representing one day on Earth.

Gargantua's gravity is also the reason for the extreme tidal waves on Miller's planet - and the time dilation means that Miller herself was only killed minutes earlier likely by the first wave spotted by the Endurance crew.

Is that Matt Damon in Interstellar?

Surprise! Despite being kept out of all trailers, premieres and publicity for the film, Matt Damon makes a shock appearance in Interstellar as the stranded Dr. Mann, the leader of the Lazarus mission. However Mann's purpose in this film is to represent the worst of humanity - the clue is in the name - and it is soon revealed that Mann lied about his planet being habitable in order to return to Earth, and he then attempts to kill the Endurance crew and steal their spacecraft.

Nolan is known for having his productions shrouded in secrecy - one security measure included shooting Interstellar under the name Flora's letter, a reference to his daughter Flora Nolan.

Less than a year later Damon would star as yet another stranded astronaut in The Martian (also starring Jessica Chastain), causing many to believe that he is playing the same character and that the two movies are connected somehow. However, this is just another Hollywood coincidence - Damon has stated that he nearly turned down his role in The Martian due to the similarities, but Ridley Scott convinced him that the two projects were entirely different.

The Martian
The Martian SEAC

Matt Damon isn't the only surprise name in the cast, however - even those who have seen the film may not have realised that a then-unknown Timothée Chalamet has a key role as 15-year-old Tom Cooper, in a time before his name would be plastered all over posters.

Interstellar black hole explained

A completely separate phenomenon from wormholes, black holes are areas of spacetime where gravity is so strong that nothing - not even light or radiation - can escape.

While Gargantua is a fictional black hole, Nolan and the Interstellar crew went to great lengths to ensure it was scientifically accurate. Thorne wrote pages of theoretical equations for the Double Negative visual effects company, which created brand new CGI software based on these equations to create accurate computer simulations. The software ended up reaching 800 terabytes of data, while some individual frames took up to 100 hours to render.

Thorne ended up writing two papers based on this experience - you can see more in the video below:

When the first direct image of a black hole was unveiled from the Event Horizon Telescope in 2019, you can see that the Interstellar team were not far off!

The event horizon is the name given to the point of a black hole where nothing can escape or be observed, and therefore we have no idea what is beyond it. This gave Nolan a bit of creative licence to explore a black hole's singularity, where he posits it will take one to another dimension - and he may not necessarily be wrong...

Interstellar ending explained

After escaping Mann's planet, Cooper and Brand have insufficient fuel left to reach Edmunds' planet. At the cost of 51 years due to time dilation, they use a slingshot manoeuvre around Gargantua, with Cooper and TARS jettisoning them to shed enough weight to escape Gargantua's gravity and get Brand to Edmunds' planet.

Cooper and TARS slip through the event horizon, seemingly heading for the singularity when they suddenly land in a bookshelf-esque structure called the tesseract (a very different one from the MCU's infinity stone).

TARS explains that "they" constructed this three-dimensional space inside of their five-dimensional reality to allow you to understand it” - time here is represented in physical form as bookshelves in a way that Cooper can understand and interact with. This was foreshadowed earlier on Miller's planet, when Brand speculated that "they" could interact with time physically as if it were a canyon or mountain.

The bookshelves in particular belong to Murph's bedroom, showing her room at every point in time. While Cooper himself cannot physically travel back in time, he can use gravity to exert a force across dimensions - including time. Initially, Cooper attempts to send the message "STAY" by knocking Murph's books off the wall, inadvertently becoming Murph's ghost. It is then TARS tells him that "they" brought him here not here to change the past but instead to send a message.

Cooper then realises who "they" are but "us" - people from the future who have evolved past the four dimensions we know, into five-dimensional beings who have mastered travelling through spacetime. However, they cannot communicate through it or pinpoint specific locations, and thus need Cooper whose love for Murph will guide him to the correct moment.

Cooper sends Murph the coordinates to NASA in binary, before asking TARS for the quantum data extracted from the black hole which Cooper sends to Murph's watch via morse code.

What did Murph solve?

Murph solved the gravity equation that Profesor Brand was working on. The gravitational anomalies that began occurring when the wormhole appeared proved that harnessing gravity was feasible.

Brand later reveals to Cooper that within the NASA facility giant cylindrical space stations are being built that could get a viable amount of human life off the planet. The problem is getting these space stations off the ground - they are too heavy for current propulsion technology, and so Brand spent 40 years working on an equation that would allow him to manipulate and weaken the gravity of Earth.

However, it is revealed later in the film that Brand concluded work on the equation some time ago and realised he needed more data - specifically quantum data from the singularity of a black hole. This was thought to be impossible, until TARS was able to extract the data from Gargantua and transmit it to Cooper in the tesseract.

Murph was then able to solve the gravity equation using this data, allowing her to temporarily reduce Earth's gravity enough to allow the space stations to launch into space and establish colonies. Cooper Station, the cylindrical station we see at the end of this film, is one of these stations.

Thorne's The Science of Interstellar details how this would have had grave consequences for Earth however - no longer compressed by the planet above, the Earth's core would have sprung up and pushed the surface outward, resulting in devastating earthquakes and tsunamis. These disasters would have occurred again as gravity returned to normal and the Earth returned to its normal size, but humanity would be secured in the colonies above.

How did Murph figure out it was her Dad?

It's shown that since childhood Murph has been fascinated by the "ghost" in her room, and is familiar with morse code. It's only when she returns to the room as an adult however that she realises the ghost is actually her father - the big clue being when Cooper wrote "STAY" in morse by knocking books off the wall while his past self was leaving for the mission, which Murph wrote down as a child and rediscovers as an adult.

Murph then takes another look at the watch Cooper left her and sees that the seemingly broken clock hand is indeed a message in morse code.

This was foreshadowed earlier in the film when a young Murph hears Cooper but believes it is the ghost, and when Cooper laments how "Once you're a parent, you're the ghost of your children's future."

Murph also gets a feeling that her ghost is trying to tell her something, which prompts her to return to her childhood bedroom as an adult. It is suggested that this feeling is actually love - while in the tesseract Cooper declares that his love for Murph is quantifiable and allows him to find the correct moment in time to communicate, but it is this emotional connection that also prompts Murph to return to her bedroom and believe that the ghost is her father.

What happened to Cooper and Brand?

The fifth-dimensional beings eject Cooper from the tesseract out of the wormhole near Saturn, where he is rescued and brought to Cooper Station, one of the cylindrical space stations he saw being built earlier in the film.

Humanity has been saved, and Murph solved the gravity equation allowing the space stations to leave Earth which has made her a bit of a celebrity. After an all-too-brief reunion, a now ninety-year-old Murph urges Cooper to go and find Brand, who will be more in need of him as Murph is nearing death and surrounded by her own family.

Brand is last seen on Edmunds's planet - which we see has breathable air - where she is burying Edmunds and setting up for Plan B, repopulating our species with the frozen embryos.

Due to the time dilation, this is of course happening at a similar time to when Cooper arrives at Cooper Station - but of course, Brand would have no knowledge that Plan A was a success as only rudimentary communication can travel through the wormhole. It is implied that Cooper will reunite with Brand, and help prepare Edmunds' planet for colonisation as humanity's new home planet.

What is the meaning of Interstellar?

As well as all the astrophysics, Interstellar also makes a kind of cheesy point about love, particularly father-daughter love.

While discussing her feelings for Edmunds, Brand famously says "Love is the one thing that we're capable of perceiving that transcends dimensions of time and space" - which is proven to be true at the end of the film, when Cooper's love for Murph allows him to find the correct point in time to communicate with her across dimensions. It is love that leads Cooper to believe that Murph will return to her childhood home for her watch, and eventually saves humanity. Some have even argued that love can be viewed as a higher fifth dimension in this film, a quantifiable force that can travel across space and time.

For some this will be a welcome break from all the hard science fiction, for others this will be an overly sentimental distraction from the film's ambitious realism and ideas. However, it wouldn't be a Nolan film without some debate about emotions!

Where to watch Interstellar

Interstellar is available to stream on NOW. You can also buy or rent Interstellar from Amazon, iTunes and Sky Store.

Check out more of our Film coverage or visit our TV Guide to see what's on tonight.

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