Not a great plan?
    The Avengers movie franchise began in 2008 with Jon Favreau’s Iron Man and has since taken in $17.5 billion for Marvel Studios.  You might be caught up with every installment, but if not (there are 20 of them) I’ll give a brief overview of the story-arc without getting too spoilerish.
    Far away, on the planet Titan, the supervillain Thanos figures out a solution to the Universe’s biggest problem.  With dwindling resources across every galaxy and species proliferating, we are in a state of chaos as every being on every planet fights for survival.  He decides the answer is simple: kill half of everything.  Less living things = less mouths to feed = less need to fight.  
    It’s a bold and utilitarian approach to the problem of overpopulation, but on sheer logic it would technically work.  I feel there’s probably a simpler solution (sharing stuff???) but you’ve got to hand it to him; galactic murder would do the trick.  Many philosophers throughout history have proposed answers to the overpopulation problem, with the most widely-debated being Thomas Maltus’ 1798 suggestion of limiting the number of children permitted per family.  Thanos isn’t interested in something like that however.  He’s a man of extremes who doesn’t do anything by half.  Except for genocide I suppose.
    As supervillain schemes go it’s not the stupidest I’ve ever come across.  That title goes to the time Wonder Woman uncovered a plot by Nazis to buy global milk supplies and sell it to America at an inflated price in order to make it unaffordable for poor children, leading to widespread osteoporosis, allowing Nazis to invade twenty years in the future.  I did not make that up by the way, they really ran that story (Sensation Comics, Issue 7, May 1st 1942).
    Killing half the population of a planet could be achieved with a fat load of bombs, but Thanos wants to wipe out half of all life in the Universe.  Given the sheer size of space (it's pretty big), this is no minor feat.  Visiting every planet and blowing up half of every city would take considerable time, so he opts for a much simpler idea - obtain the six infinity stones.
    In the Marvel Universe these are six mystical gemstones which control six facets of the Universe: time, space, power, reality, mind and soul.  Any being who possesses just one of these items becomes immeasurably powerful, but if Thanos can get his hand on all six he will wield absolute power over the cosmos with a snap of his fingers.  It's a cool idea, so I decided to take a look at the scientific plausibility of Thanos' plan.

Space and Time Stones
    Every event in the Universe takes place in three-dimensional space (potentially higher dimensions if you’re into string theory) but defining everything spatially is not enough to describe the laws of physics.  You need time as well.  
    The simplest way of demonstrating this is to try imagining an object which occupies space but not time i.e. it has size but doesn’t occupy any seconds.  To say an object doesn’t exist for any measure of time is to say the object doesn’t really exist, ergo time has to be thought of as a fourth dimension.  If you leave it out and just have a Universe made of space, you essentially have no Universe.
    It’s a slightly unusual dimension compared to length, breadth and height, because we can only move through it in one direction, but it is part of our Universe’s backdrop.  If you want to control or influence anything you need to talk about things happening in space and time simultaneously.
    The physicist Hermann Minkowski therefore proposed we stop thinking of the Universe as objects in space moving through time, but rather as objects moving through a unified material he called ‘spacetime’.  Einstein figured out the basic rules for how spacetime should behave in his general theory of relativity and it turns out everything checks with experiment.
    If you want to control an event across the entire Universe, you would need some way of controlling space and time simultaneously.  Therefore, Thanos’ need to have the space and time stones makes sense.  So far, so good.

Reality Stone
    It’s never explicitly stated what the reality stone does in the movies, but you can infer it from seeing how people use it.  There’s a scene in Avengers: Infinity War where Thanos uses it to turn pulses of laser-bullets into bubbles and generates cities out of thin air.  I propose that while the space and time stones control the background of the Universe, the reality stone is manipulating the particles within it, telling them how to arrange. 
    There are something like 200 types of particles known in physics (I’ve written a post about them here) and the key message is that every object you come across is made from these particles in one way or another.  If you control every type of particle, you control literally every object.  While there are undoubtedly some types of particle we have not yet discovered, we can assume the reality stone influences them too, even if we don't know about them.   
    So, given the first three infinity stones, Thanos can control every particle in spacetime.  But since he’s wanting to create an event (lots of death) he also needs to control how objects interact with each other.

Power Stone
    Every law of Science involves three principles: particles, the spacetime they inhabit, and the energy involved in the interaction.  Power is the word we use to describe how quickly energy is transferred, so I propose the fourth stone is the one which controls energy and thus interactions.
    Energy is sometimes described as a substance a particle can possess, but this is a tad misleading.  Energy is not really a thing, it’s a way of expressing the concept of cause and effect mathematically.  When you eat food, chemical reactions take place between the food molecules and those in your body, which allow you to move and live.  The food was the cause and your movement was the effect, so we can measure precisely how much ability the food had to cause an effect on your body.  This is what we mean when we describe something "having energy".  
    The food you eat doesn’t contain a glowing fluid-substance called energy; it contains particles.  But those particles have ability to exert an effect on other particles.  The power stone is perhaps the most philosophical therefore, because it allows Thanos to make sure cause and effect are working when he snaps his fingers and kills everyone.  And this might be all he needs.
    Every law of physics we know, and by extension all of chemistry and biology, rests on these three ideas: particles, their interactions and the background in which they live.  Given control over these things, Thanos would have the bare minimum required to bend things to his will.  But there are some scientists who would argue for another stone, since it’s possible something else exists in the Universe.  Something not made of particles at all...

Mind Stone
    It’s clear that your brain is made of particles, meaning the reality and power stones should be more than capable of manipulating it.  It’s also undeniable that we can influence and change the mind’s inner working with the right particles e.g. psychiatric medications, narcotic substances, anesthetics and electromagnetic fields.  But is that all there is to consciousness?  Might there be something more than biochemistry going on?
    The answer is not settled and indeed some hard-nosed and brilliant scientists (including Nobel prize winners like Niels Bohr and Eugene Wigner) have argued that the mind may in fact have an entirely non-particle component to it...maybe.
    I’ve written about it in more detail (here) but it comes down to a phenomenon in quantum mechanics called the measurement problem.  When quantum particles are left to their own devices they behave a certain way.  But when we take measurements in the lab, they behave in a totally different way.  The puzzle comes from the fact that the lab equipment we’re using to take our measurements are made from the same quantum particles, so they shouldn’t have any sort of spooky effect.  Quantum particles interacting with more quantum particles shouldn’t change their behaviour.  And yet they do.
    There are many answers given and one of them is that consciousness itself exerts influence on particles, that our very act of observing the experiment changes it somehow.  I have to be clear that this is a minority view and only one of the many possible solutions to the measurement problem, but we cannot discard it.  There is just enough to the theory to make it worth considering, so let’s go along with it for the sake of the movie.  If the mind genuinely is a separate substance to particles, Thanos would need a fifth stone to be omnipotent.  So what of the sixth?

Soul Stone
    OK, this is a little more controversial and I’m going to have to tread cautiously so as not to upset anyone on either side of the fence.  Physics definitely agrees the Universe is made of particles exchanging energy in spacetime and there is a small group of quantum physicists who suspect the mind may be involved in some way.  The soul is a less well-defined concept however, because it has different meanings to different people.  
    A good way to demonstrate this difficulty is to ask: what, specifically, is the difference between the soul and the mind?  The mind is a collection of a person’s memories, beliefs, ideas, hopes, fears, perceptions of the world and self-awareness.  A person’s identity can be neatly summed up as their mind, so what is missing from the list which requires a soul?  What additional ingredient is needed in defining a person which the mind doesn’t already cover?  
    Some religions teach that while all animals have a mind of some sort (even jellyfish have a central nervous system), when the animal dies their mind perishes as well, but humans continue to exist once their body is done.  The soul is therefore, under some definitions ‘that which keeps the mind preserved once the brain has died’.  In other words, the notion of souls takes us into the realm of an afterlife.
    Science has a lot to say on the topic of the mind and the debate is very exciting, but there is no scientific debate on the soul because there is no clear information one way or the other.  There are all sorts of claims of course, but someone claiming something is not enough to warrant a scientific perspective.  This doesn’t mean the afterlife is not real mind you, absolutely not.  It’s just that the scientific answer to such a question is “hmmm, we have no idea, could go either way.”
    Because we can’t prove or disprove the existence of souls we therefore can’t say much about what the soul stone does.  But, let’s say that the theology of the Marvel Universe is correct and souls are genuine things.  Thanos obviously doesn’t want to destroy half the planets and stars in the Universe…that would defeat his whole plan.  He wants to leave all the planets and resources in their current state but cut the number of living things by 50%.  Therefore he’ll need a way to exert his power on only living organisms and not inanimate objects too.  If we propose that all living things have a 'soul' distinguishing them from non-living objects, then he would logically need a stone for that.

What Are Infinity Stones?
     The answer, I think, can be found nestled in both the theories of quantum cosmology and in a scene from Guardians of the Galaxy…both of which are pretty awesome.  Here’s the scene in question (movie is rated PG-13 in America and 12A in the UK):

    In this scene, during which the power stone is revealed, The Collector explains “before creation itself there were six singularities, then the Universe exploded into existence and the remnants of these systems were forged into concentrated ingots - infinity stones.”
    A singularity is an object whose properties are so extreme we can’t describe them with our current knowledge of physics.  The center of a black hole is considered a singularity for instance, since according to the laws we know, a black-hole’s center has an infinite amount of density and gravitational pull.  Anything which predicts an infinite property cannot possibly be the right answer since the Universe is a finite system, therefore singularities are really a physicist’s word for “objects we can’t figure out yet” and any theory which predicts a singularity is not complete.  
    The origin of the Universe is just such a singularity.  All we know is that 13.8 billion years ago, the entire Universe was condensed into a tiny speck which started expanding.  We have no idea where this speck came from, what it was like, what made it start expanding or if anything came before it (assuming there was a ‘before’ since time may have ‘started’ with the Universe).  We can explain the evolution of the Universe pretty well after a certain point, about a quadrillion quadrillion quadrillionth of a second, but anything before that is a total mystery. 
    According to The Collector, there were actually six singularity objects alongside ours 13.8 billion years ago and when our Universe began expanding, for whatever reason, these six singularity objects got absorbed into ours, rather than expanding themselves.  These objects would therefore be like miniature Universes which somehow avoided the expansion.  They stayed as ‘concentrated ingots’ and contain, it would appear, properties we would normally attribute to an entire universe.
    Since we currently have no idea how the Universe began or how many singularities there were, or how they interacted, or why our Universe’s singularity expanded we can sort of shrug a little bit and say “yeah, OK, why not”.  There was at least one singularity at the beginning which started expanding so why not six others which didn’t?  There are stranger things in nature, like the Lophorina bird (see below).  If that is real, I can swallow infinity stones.  Not literally of course, did you see the video???

With a Snap of his Fingers
    The really scary idea of infinity stones is that once Thanos has all six of them, he can exert his will over everything instantly from one place.  But how could such a thing be possible?  Surely you couldn’t immediately effect every point of the Universe at once?  Well, fortunately for the Marvel universe, there is one possible mechanism by which this could potentially be achieved.
    It’s a phenomenon called quantum entanglement and it’s really strange.  I don’t want to get hung up on technicalities but if you’re curious, the book I’m currently writing (a sequel to Elemental) which will be released in the Summer goes into all the gory details, so look out for that.  The gist is that two particles which interact can become linked together in such a way that doing something to one will instantly affect the other no matter what distance there is between them.
    The mechanism of how entanglement works is one of the biggest mysteries facing physicists today but it’s an undeniable effect.  It genuinely is possible to impact a particle on the other side of the galaxy, or even the Universe, if you entangle it with a particle here on Earth.  There’s all sorts of limitations and caveats on entanglement and there is no obvious way of sending a self-destruct order to half the particles in the Universe, but this is a sci-fi film so let’s just say there’s a way of doing it.
    In order for two particles to entangle, they have to meet each other at an earlier point, so in order to affect the whole Universe simultaneously, you’d need to somehow wind back to a time when all the particles were close together - say when the Universe was small and everything was concentrated - 13.8 billion years should do the trick.  
    If you had an object or a bunch of objects hanging around when the Universe was still a singularity, they could entangle themselves with each other and with the Universe as a whole, so once the Universe expanded, they would stay in direct quantum-contact (quantact anyone?) with everything inside it.  Every particle would be linked together by their entanglements to the six infinity stones and thus, if you manipulated them in the right way, you could genuinely snap your fingers and affect everything everywhere. 
    So if you had a way to control all matter (reality) across spacetime (space and time) assuming quantum consciousness is required (mind) then you can control everything in the Universe.  If you send a pulse out to every particle via the entanglement links established at the beginning of the Universe, you could target all the particles incorporated into living things (soul) and tell them to dissociate from each other (power), dissolving half of all living things.  Hooray??#

mage Credits:
Thanos with his glove: Superherohype
Milkman: Smosh
Minkowski: spacetimesociety
Bubblegun: YouTube
Energy Milk: coopathome
Mind Stone: The Conversation
Soul Music: pinterest
Lophorina Bird: hashem

Books For Smart People
    I’m an adult and I’ve read plenty of great literature.  I’ve read the works of Plato, Aristotle, Shakespeare, Marlowe, Dickens, Austen, Twain, Melville, Eliot, Hemingway, Orwell, Ishiguro etc. but I’m also a fan of comic book writers like Alan Moore, Frank Miller, John Wagner and Stan Lee.  I distinctly remember having a copy of Bertrand Russell’s History of Western Philosophy sitting next to Judge Dredd: Total War on my bedside table at one point.  Just because I read comic books doesn't mean I can't also appreciate "classics".
    In fact, every Christmas I tend to read Dickens’ A Christmas Carol and the comic book Batman Noel one after the other in the same day. I enjoy the escapist entertainment and haunting artwork of one and the linguistic brilliance and sentimental wit of the other.  I'm also in the process of writing a book on quantum mechanics due for publication this Summer...I would like to think reading comic books clearly hasn't dulled my critical faculties or stunted my intellectual growth.
    I mean, I agree that you should grow out of childish stories as you get older, but these days there are lots of sophisticated comic books written for adults.  Take Maus by Art Spiegleman, a comic book about the Holocaust which won a Pulitzer prize.  That book made my skin crawl with horror and made me tear up with emotion.  I have also read Schindler’s Ark (the book on which Schindler’s List was based) and found it equally moving.  Is one of them a more adult form of art because it doesn’t contain pictures?  Can't they both be powerful and thought provoking pieces of literature?
    Comic books today have evolved beyond Dennis the Menace and Stan Lee was central to that deveopment because he was one of the first writers to introduce adult issues to his stories.  Before him, every comic book character was a 2D square-jawed hero who saved some damsel in distress from a moustache-twiddling "foreigner".  Lee began creating characters with emotional complexity.  
    His comic books dealt with issues like racism, sexism, drug abuse and political corruption.  He wrote comic books in which women were central characters with complicated emotional lives rather than foils for male heroes to save, and Lee fought hard to include black characters in his works without stereotyping them.  Yes, Stan Lee’s early comic books were written for children, but as the children grew up, so did his writing.
    But, let’s say Maher was right for a moment and that comic books are for children.  In what way does this make them unimportant?  Stan Lee was, according to Maher, an author of children’s literature.  Do we no longer celebrate children's literature in the Maher-niverse?
    I’m wondering if Bill Maher will be as equally disparaging when JK Rowling dies?  Or if he thought it was ridiculous when people got sad over the death of Dr Seuss or Beatrix Potter? I think Stan Lee was plenty important to our society, unless Maher is going to claim children reading isn't important?
    Stan Lee made a lot of kids happy and millions of people have fond memories of reading his stories.  By contrast, Maher's job is making caustic remarks about politicians behind a desk.  That's his role in society.  It's an important one of course, satire is crucial to an informed democracy, but is it more noble a profession than getting young people reading?  I don't think so.
    Besides, Stan Lee did something even more important for pop culture, which I am going to elucidate on now (because you might be wondering why I’m writing about comic books on a Science blog)…he made scientists the good guys.

The Evil Genius
    Typically in movies, comic books and pulp-fiction novels of the day, scientists were depicted as the villains, without fail.  We were always the maniacs who reached too far and accidentally unleashed a deadly plague on the Earth or brought space-vampires from Mars down to eat our livers.  Stan Lee made scientists heroes of his stories instead, and showed how they used their intelligence to outwit common criminals.  He made scientists look awesome!
    Reed Richards of The Fantastic Four, got his powers on a scientific expedition.  T’Challa, The Black Panther was a diplomat and scientist.  Charles Xavier from X-men was a biologist and anthropologist who lectured at Oxford.  Bruce Banner was a nuclear physicist.  Tony Stark was an engineer.  Peter Parker was a high school physics student.  Hank Pym was a particle physicist...I could go on.
    Stan Lee respected the importance of getting kids interested in Science and I would argue that along with Gene Roddenberry (creator of Star Trek) he did more to raise the profile of fictional scientists than anyone else in popular culture. 
    Stan Lee also used scientifically legitimate devices to get stories going and showed his heroes using science to defeat bad guys.  Sometimes Lee’s physics wasn’t quite right (he wasn't a scientist after all) but oftentimes it was gosh-darned impressive.  There’s a Spider-Man story where Electro uses his electrical powers to generate induced magnetic fields inside an iron beam and scale a building to escape via Lenz's law.  Lee is teaching children about electromagnetic fields here.  Rather than having mega-ray death-lasers controlled by evil gnomes, Lee would often ground his fanciful stories with real scientific terminology and make geeks look like heroes for a change.

How I Use Comic Books
    As a physics teacher, what you’re usually doing is teaching kids a quick equation or law, which can sometimes be quite dry, especially for an hour.  The best thing to do (the really important thing to do) therefore is show how physics relates to the real world.  But most text-books do this in a very plain fashion.
    Physics textbooks are a world of perfectly spherical balls rolling down frictionless surfaces and John and Jane calculating the mass of a pulley given the acceleration of a cube as it is pulled upwards etc. etc.  How many young people do you think are going to get fired up about physics because of that?  Not many.  But if you can push physical laws to their extremes by relating them to sci-fi stories, you can get debates going.  You can get people to use the equations in a novel way and see how they really work in outrageous scenarios.  Here are some examples of how I have used comic books and comic book movies in my lessons:
    There’s an iconic Spider-Man story where Peter Parker tries to save Gwen Stacy falling off the golden gate bridge, but his webbing catches her and brings her to a halt too fast, potentially snapping her neck.  Peter Parker then has to live with the guilt of maybe killing his girlfriend because he didn’t take into account changes in momentum (yeah, a kid’s story…sure).  I use this comic book scene with my A-level students to calculate the forces involved and answer the question of whether Parker really kills Gwen or not.  It’s a great way of teaching concepts like forces, elasticity and gravitational energy.
    There’s a scene in The Avengers where Hulk stops a crashing alien spacecraft with his fist.  I show this clip and contrast it with the scene in Superman Returns where Kal-El catches an airplane and we use Newtonian mechanics to determine which one of these characters is more powerful.
    In my lesson on velocity, we use panels from comic books to see who would win in a race between The Flash, Superman and Quicksilver.  I’ve used scenes from Ant-Man to talk about quantum mechanics and how object sizes are determined by inter-particle forces.  I use clips from X-Men 2 to illustrate how electromagnetism works and a scene from Spider-Man 2 to teach nuclear physics.
    I’ve used clips from The Dark Knight Rises to calculate the radius of an explosion outside Gotham city.  I’ve used panels from Aquaman to teach the behaviour of waves.  I’ve taught lessons on radioactivity using Spider-Man, The Hulk, Daredevil, Reed Richards and The Phoenix (who all got their powers from radioactivity).
    Even if the kids don’t really care about comic books, they can at least tell I’m trying to have a bit of fun with the topic and show how physics can be applied to novel situations.  So I say thank you to Stan Lee and all the other comic book writers and comic-book movie makers who give me so many cool and over the top moments to showcase to my students and get them thinking.
    I’m not saying a person’s literary diet should consist solely of comic books.  But let me put it this way: if you want to teach a 12 year old about Newton’s second law, which do you think is going to get them more engaged - making them read an excerpt from Principia Mathematica or showing them the scene in The Dark Knight where the Joker flips an articulated lorry in mid-air using helicopter cables?
    Comic books tell stories.  They do it with words and pictures.  Some are written for children, some are written for adults.  The artwork is often remarkably detailed and the dialogue often snappy.  Stan Lee was a key figure in developing an art form and getting real science into his stories, as well as depicting scientists as good guys.  I think that’s pretty important Mr Maher and frankly I think Stan Lee rocked.

Image Credits
Stan Lee Reading: ibtimes
Bill Maher in Iron Man Three: YouTube
Spider-Man: Variety
Stan Lee Rocks: Bleedingcool