The Social Construction of Gravity

One of the more annoying points of contention back in the days of the Sokal hoax and the "Science Wars" was an argument over social construction. This is, loosely speaking, the idea that our understanding of the world is not strictly rational and objective, but is heavily influenced by interactions with other people, and the culture in which we live. The idea originally arose in literary academia, but expanded to be applied to basically everything, including science.

At bottom, this is probably the best and most useful idea to come out of whatever collective "-ism" you want to use to refer to 20th century scholarship in the arts and literature. Applied in a reasonable manner, it ought to be fairly uncontroversial-- it's not hard to come up with examples of theories that were accepted more quickly or rejected out of hand because of who proposed them, and anybody who's done research knows that there are a lot of factors beyond pure science that go into how scientists choose what to study, and how results are interpreted.

The problem is that once you have a hammer, everything starts to look nail-shaped, and good ideas get ridiculously overextended. This is true in physics, as well-- the tendency of aging physicists to wander off and start reinterpreting whole other fields of inquiry in terms of a handful of physics concepts is well documented and regrettable. In the case of the science wars stuff, this led to various post-whateverist scholars claiming that there was no objective reality, and science was entirely a collection of social constructs. A position that was rightly regarded as ludicrous, and led to the Sokal business, where a prominent journal published a bunch of gibberish that NYU physicist Alan Sokal slapped together, and was embarrassed by the revelation of the hoax.

Of course, there were a fair share of annoying arguments from the science side, as well, where a number of scientists took positions opposing the entire idea of social construction, which is in its way just as blatant a rejection of obvious truth as anything from the post-whateverists. One of the rhetorical devices frequently employed by this group was to ask mocking questions like "So, is gravity a social construct?" Which, like most such arguments, is correct in a narrow, technical sense while also being not nearly as convincing as the geeks who deploy it think.

Which made it interesting, these past couple of weeks, to see a dramatic demonstration of the social construction of gravity in a quasi-real context. I'm referring here to the short, spectacular life of the touch-screen game "Flappy Bird," which was removed from both iTunes and Google Play over the weekend, to general bafflement as to why anybody would shut down such a successful game.

The game is, as I was telling a colleague in CS on Friday, simple and stupid enough that you could probably assign "Write 'Flappy Bird'" as a homework problem in a low-level programming class. It's a pixellated little blob of a bird that flaps its wings when you tap the screen and falls when you don't, and the goal is to fly it through a series of Super Mario pipes without touching anything. It's ridiculously difficult, though, and weirdly addictive.

The difficulty stems largely from the fact that the bird falls really fast, which prompted a lot of folks to take to social media and grumble about how the physics of the game couldn't possibly be right. This was like a bat-signal sent up to physics bloggers, and Frank Noschese took up the challenge, using video analysis to show that the little blob of pixels does, in fact, fall with a constant acceleration, and that if you assume the bird is the size of a real bird, it falls at a rate consistent with real-world gravity. He put together a really nice demo of this, with a pair of iPads showing video of Flappy Bird next to video of a colleague dropping a basketball:

The two objects stay at the same height all through the fall, showing that they're falling at the same rate.

(This is not to say that the physics is perfect-- as Frank also noted, the "flap" is a little dodgy, as the bird always ends with the same upward velocity, regardless of how fast it was falling before the "flap." That's the other big factor contributing to the difficulty of the game.)

So, why all the outrage? Well, because of the social construction of videogame gravity. As Flappy Bird shows, when you put realistic gravity into video games, they're really hard. So, while games like Angry Birds and Fruit Ninja use a constant vertical acceleration, they crank down the acceleration of gravity to make the game easier. If you put in a realistic acceleration, they would be ridiculously difficult.

People got outraged about the physics of Flappy Bird because years of previous games had conditioned them to expect a lower acceleration, leading to easier gameplay. We've socially constructed an expected acceleration of gravity in videogame worlds, and when that expectation was confounded by reality, people got peeved.

Now, does this mean that the real physics of gravity is also purely a social construct? Not purely, no. There's unquestionably a bit of social dynamics involved in the development and acceptance of general relativity, our best current theory of gravity, but the underlying phenomenon is unquestionable. A different set of social circumstances and dynamics might've led to us using different language to talk about it, but in the universe where that happened, objects would still fall when dropped near the surface of the Earth, and Flappy Bird would still be maddeningly difficult to play.


(This is a longer version of stuff I said in last week's Uncertain Dots hangout with Rhett, but I offer it as a tribute to the passing of the game. Godspeed, Flappy Bird, you annoyingly fragile little bastard.)


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Apparently, someone someplace will not like something, and make a bit to-do about it. I, personally, like Flappy Bird, and have no problem with gravity - period. Thanks for your input.

Could it be argued that, to the extent that we all say "what goes up must come down", gravity is partly a social construction? Shouldn't we be saying "What goes away from the center of the Earth's mass must return towards the center of Earth's mass?

By Lynn Dewees (not verified) on 10 Feb 2014 #permalink

There is no doubt that social construction makes things in science more subjective, but they are supported by obvious examples (in this case how things fall with gravity). Dealing with a game like Angry Birds, is it okay to socially construct people to a world where the physics is not correct? I understand that the slower acceleration allows the game to play better, and equates to more fun, but it is for this reason that people are upset over a game like Flappy Bird. Personally, I like my video games the way they would be in real life, which is why Flappy Bird is one of my favorites. The point I am getting to is that if we construct people to a world like an Angry Birds, aren't we giving people a false sense of what the world is really like in terms of physics? I'm not saying Angry Birds is a bad game, it provides mindless enjoyment, but is that acceptable all the time? People outraged over Flappy Bird, more or less because the physics are correct and individuals could not accept that. I say make more games like Flappy Bird, the challenge is more fun and it exposes us to how forces really act in the world.

By Andrew Wright (not verified) on 10 Feb 2014 #permalink

This article was extremely interesting to read and easy to relate to. We recently learned about velocity and acceleration in my physics class. I am also one of the many who have cursed Flappy Bird for it's level of difficulty. I was very surprised to find out that the acceleration is actually exactly equal to that of gravity and not a much higher value, as demonstrated in the video. I would have to agree with Andrew about his statement regarding the fact that games such as Angry Birds have distorted our perception as to what the physics of games are in relation to the physics of reality. Personally, however, I prefer games that reduce the acceleration of gravity when velocity in the x direction remains constant. I cannot agree with the post above about making all games with forces equivalent to those of the real world simply because I believe it makes them far more difficult, and I am somewhat of a sore loser. I don't think people apply the physics and rate of gravity they experience while playing these games to real life, they play them for a simple form of entertainment. Everyone knows how quickly a cup pushed off the counter will fall because people experience things in free fall multiple times a days, they won't assume it will continue horizontally for an extreme distance before crashing into their living room couch.

The application of realistic physics to video games can have some very good effects upon the users. Many players apply their video game knowledge to real life situations, in the case of physics it could be deadly. Broadening the realism in all aspects of the video game realm is necessary, imo.

By Thomas Powel (not verified) on 10 Feb 2014 #permalink

Brilliant post, Chad, on all counts.

I'm one who highly admires Sokal for his takedown of postmodernism. Yet I'm also persuaded by you that "social construction" is a useful idea when applied to purely social realities. To which I would add, so long as one doesn't take it to excess (such as claiming that human rights are culturally relative, as if people born in country X feel pain any less than those born in country Y).

As for video games, I'm less concerned about unrealistic gravity than about gratuitous violence, which has the perncious social effect (per multiple peer-reviewed articles) of encouraging aggressive attitudes and lack of empathy.

This is actually fairly complicated. Both the length and gravity of objects in video games are undefined variables. What is the height of mario vs the height of a flappy bird?

The better variable here is either character-lengths in a screen, or else time taken to fall height of screen. The time taken for each operation is our usual time "t".

In fact, thinking about this, I don't think the video really shows that the game has the same gravity as the earth. In fact, I think you could make the same video for _any_ game, regardless of its supposed gravity value.

Starting from rest, falling a distance s to the ground in time t, gravity is given by g=2s/t^2. Scaling everything to character lengths L, the total height of the screen is s=NL, and so the games gravity is g=2LN/t^2. Moreover, the time to fall from rest to the bottom of the screen is t^2=2LN/g inside the game world.

Let g0 be the gravity of the earth. To perfectly simulate the game gravity g, we require an object on earth, of length R, released from rest, to cross its own length N times in the same time as the game object. So t^2=2LN/g=2RN/g0. So we need to drop and object from a total height NR=t^2/g0, and choose R= L (g0/g), and when we do the motion of our object on earth will sync perfectly with the motion of the object in game, regardless of the games own measure of gravity.

So I don't think any video can be a demonstration that gravity in games is chosen to be less, equal, or grater than the earth's gravity. The choice of gravity in games is a question of scale.

I was going to go off and apply this argument using data from Mario, but it would appear that, as usual, the internet has already done this.

The link gives raw pixel distance and time data for various mario games, but the __higher than earth__ values for gravity derived are based on the absurd assumption that (small) mario is 1.5 metres in height. He is at most half this, so personally I would half all of the resulting values for g here.

It's worth nothing that Super Mario World (g=6.32 earth) (3.15 earth by my reckoning) is probably the most influential title when it comes to the gravity scales of video game titles. (Though I would be inclinded to look at Megaman 2 as well.)

Basically, these numbers demonstrate that gravity in platforming video games seems by default to be much _higher_ than gravity on the earth.

I agree that determining the acceleration of gravity requires a scale, which is why the relevant sentence reads "if you assume the bird is the size of a real bird, it falls at a rate consistent with real-world gravity." That is, Frank measured the rate at which the bird falls in terms of its own size, and then plugged in a value for that size based on the size of real-world birds, and got an acceleration consistent with Earth gravity.

Another approach, which Rhett takes in the linked posts, is to measure the acceleration in terms of the size of the object, then ask how big the object would need to be for that acceleration to be consistent with 9.8 m/s/s. In the Fruit Ninja post linked above, for example, he finds that the orange/grapefruit would need to be 68cm across, which is a little unrealistic.

Recently we have been studying velocity and acceleration in my physics class and was stunned and embarrassed to see the truth of this post. Out of my own disbelief i attempted and confirmed that Flappy Bird has real acceleration due to gravity of -9.8 m/s^2. I also believe, along with the fellow commenters, that true physics should be applied to video games. Anything else is like playing a game based out of planet Earth.

By Howard Jeffers (not verified) on 11 Feb 2014 #permalink

My Physics 101 class has been learning about speed, velocity, acceleration, and projectile motion. After reading an article that targets an area I have been studying, I became immediately interested in the topic. I am a Flappy Bird addict who has fallen in love with the game. Although I used to be skeptical and sometimes believed that the acceleration of Flappy Bird must be triple the acceleration of objects on earth, the video above proved that Flappy Bird falls with an acceleration equal to the pull of gravity (g=-9.8 m/s^2). It is interesting to see that some video game creators consider physics while creating their games. I have always ignorantly believed that they just create a game that will foster people's enjoyment and do not consider much else. As a gamer, I wish that video game creators would reduce the acceleration of Flappy Bird by reducing the pull of gravity in the game or changing the shape of Flappy Bird to something that would create more air resistance (maybe larger wings). As I learned in class, two objects will hit the ground at the same time even if their masses are different; however, an if one’s shape increases air resistance, it will fall at a slower rate. If the changes I mentioned above were made, I would have a little more reaction time. Although that would help me achieve higher scores, I have to agree with Andrew. I think that creating games with realistic acceleration is more interesting and challenging. All popular games are the ones that people have to spend weeks mastering in order to win. Introducing life like forces will make games more challenging and therefore more popular. Andrew also presents very interesting ideas about how some video games are exposing people to false constructs of reality. I believe that this is detrimental because it affects how people perceive the idea of acceleration and how they apply “their ideas” of physics in the real world. Even if one does not have a background of physics in academic settings, they can easily learn correct theories and ideas through the video games they are exposed to [with correct acceleration], like Flappy Bird.

By Carly Black (not verified) on 11 Feb 2014 #permalink

I have been studying the topics of acceleration and velocity in my physics class as well and have played the game and found it to be difficult at first. I was very surprised when I read this blog and even tried the experiment they conducted in the video and got the same results. I also believe that real life physics should be used in video games like the other comments to add to the more realistic game play the video game manufactures are trying to recreate. I think this would lead to more challenging games in the future. I believe that this would only boost the enjoyment of playing a challenging video game. In addition, I also believe that the more realistic a game seems to be the better a game is in my opinion.
The use of real physics in video games specifically sport related games could possibly create games that take longer to beat and a more realistic experience in online multiplayer games which is something I am looking for in games like some racing games where at times it seams like real life physics are not used.

By Garrett Simmons (not verified) on 11 Feb 2014 #permalink

Someone is assigning your blog for class, Chad. :-)

There's a big variation in bird size. Clearly, we shouldn't be considering something like an ostrich, which doesn't fly at all, but say a large condor (3 m wingspan) versus a hummingbird (10 cm wingspan) would lead to a factor of 30 difference in the derived acceleration of gravity. So it's pretty meaningless to say that the game models the magnitude of the acceleration of gravity on Earth, unless some indication is given of the title character's size.

The more interesting thing is modeling the acceleration as constant, which is Earth-like, at least at a reasonable scale of bird travel. But even then, I think we're expecting a bit much of our ipad apps if we want full-blown multiphysics simulations of the real world. Flappy Bird exists in the world that's programmed for it.

I am reading that the acceleration used for the game was derived after determining a relative size for the 'flappy' bird. But without air resistance- which is obviously not included in the game- the mass of the bird would therefore be irrelevant since gravity has a constant acceleration as shown in vf^2 = vi^ + 2ax. Whether the bird was a hummingbird or a hawk, without air resistance it should fall at -9.8m/s^2. On the other hand, I find it delightful that the creators of flappy bird used realistic circumstances when constructing their graphics. I would be curious to know the velocity and/or acceleration upward that tapping on the screen provides the bird. Is that number consistent with the displacement?

G. Smith, this explanation might not be necessary, but the idea is that the acceleration of gravity in the game has been measured from the image on the screen. Acceleration has units of length and time, so to convert that measurement to the real world, you need a scaling factor for those two values. We're all sort of defaulting to the assumption that 1 second of game time is equal to 1 second of real time. So we're left with an assumption about the length scale, and apparently, if you assume that a Flappy Bird is about the same size as an average bird, you come up with a magnitude of acceleration that is consistent with the acceleration at the Earth's surface. But if you assumed a Flappy Bird was the size of an airplane, you'd come up with a much bigger acceleration, and if you assumed it was the size of an ant, you'd come up with a much smaller acceleration. The most natural thing to do would probably be to assume that a Flappy Bird is exactly as big as it is depicted on the screen of an iPad, about an inch. And that would give a different value of acceleration.

This new craze of flappy bird has everyone bent out of shape because of the difficulty. Since all of the physics components are realistic, this makes the game significantly harder. Since acceleration of gravity is 9.81 meter/sec/sec when the user taps the screen and negative when the bird is in free fall, it goes up and down at a significant rate. Timing must be perfect when holding/tapping the screen so it fits through the small window. As the other people have said, I also got the same results when conducting the experiment. I think the creator was wrong in removing the game because of how frustrating it is. This makes games much more fun.

I have recently learned much about gravity,acceleration,and velocity in my physics class. It is awesome to be able to apply what ive learned to the real world and video games such as flappy bird. Gravity(Earths gravity) pulls objects 9.8m/s^2 regaurdless of its mass when neglecting air resistance.The Earth also experiences a force equal to the push it exerts on a free falling object. The force of Earth's gravity results from the law of gravitation and centrifugal force.

By Michael M (not verified) on 12 Feb 2014 #permalink

Although Flappy Birds is just a game, the idea of gravitational pull downwards plays a huge factor in the game. The bird is constantly falling downwards with a constant acceleration unless you touch the screen enabling the use of his wings to go upwards through the obstacles. Even though, the game uses constant acceleration downwards everything about the velocity going back upwards contradicts the laws of motion. Making the game extremely unrealistic but easier for people to play the game because it only takes one tap to get him back into the upward direction.

By Nieko Torres (not verified) on 12 Feb 2014 #permalink

In the case of Flappy Bird, having a realistic magnitude of acceleration has only made the game more challenging and more addicting. The people arguing that the acceleration is an unrealistic magnitude are simply looking for a way to explain the difficulty of the game. Previous posters’ arguments that the unrealistic aspects of other video games should be changed or that new games should take realistic physics into account are not entirely sound. I think it would be safe to say that the average consumer of popular video games such as flappy bird do not spend much time worrying about whether or not the bird is accelerating at exactly 9.8 m/s^2, but simply play the game and become accustomed to whatever conditions the game presents. I also do not think that unrealistic properties of physics in games such as Angry Birds affect the user’s perception of the real world. The average person, hopefully, can distinguish between a videogame and a real life scenario, not to mention that if a person is consulting a game involving spherical birds, a sling shot, and green pigs for real world physics applications, they have bigger problems. Though in the case of flappy bird applying real forces has made it that much more popular, not all games require such realism and some things are just for entertainment purposes. This is not socially constructing people into alternate realities with unrealistic forces, it is simply creating a fun game.

By Madeline Tappe (not verified) on 12 Feb 2014 #permalink

i think that bringing logic into the video game world actually made the game better and the physics in this simple game are quite related to some things we did in my physics class about free falling and other aspects of motion in the y direction. and i believe that the game its self brought a sort of realism to the gaming community and was proven that the bird does in fact reach an acceleration of 9.8m/s^2. i think that the major success of the game and its down fall came from its use of actual physics of gravity, it made it more challenging and more addictive to get to the next level, and failure caused rage. but the best games i have played have been closest to reality. and i guess common use of these things could also raise interest with physics in youths.

By Benjamin lingg (not verified) on 12 Feb 2014 #permalink

In video games, people are socially constructed to believe false claims about the laws of physics. In reality, objects in free fall have a constant acceleration of -9.8 m/s^2. The creators of Flappy Bird accurately represented this concept as shown in the video above. Other video games slow the acceleration to make it easier for players to succeed. The fact that Flappy Bird is so realistic makes the game much harder. The reason this game is so addicting is because it is a lot more challenging than people are used to. The creators probably took this into consideration knowing full well that people get bored when things become too easy. I, personally, was very frustrated with this game when I first started playing. However, the only way to become better at something is to practice. In my physics class, we are encouraged to practice additional problems in order to develop a better understanding of the material. If you take this approach toward school work and video games, you will ultimately make progress and better your skills.

By Michelene Anza… (not verified) on 12 Feb 2014 #permalink

First of all, I literally just played flappy bird on my phone. (I luckily had it downloaded on my phone before they took it off the App store!) And now I am happy to see there is a reason the game is so difficult; a true display of the acceleration of gravity! It is really interesting to see that Flappy Bird actually uses realistic physic components, rather than the altered components most video grames use; I never thought I would be thinking of physics and Flappy Bird in combination until reading this article either! Anyways, I loved the demonstration with a real-life object and the flappy bird falling to the ground in the game. It was a simple demonstration of the truth behind the statements made. As Andrew and other commenters mentioned, I really believe video game programmers/manufacturers would benefit from including realistic physics components like Flappy Bird does, because it would only make games more realistic, which seems to be the goal these days and create a fun avenue to apply physics to other enjoyable activities! I definitely would be able to learn about physics more effectively, if we had these types of examples to relate to!

By Antonella (not verified) on 12 Feb 2014 #permalink