The Physics of Spells - Velocity, Gravity, Etcetera

[Tim the Enchanter]

Hello there!

I'm curious about the physics of "projectile" spells, as in the type that shoot an actual magic bolt (like Stupefy and Avada Kedavra), and I think this might be an interesting topic to discuss.

First of all, I was wondering, at what speed do "projectile" spells travel? Remember, they seem to go slow enough for people to duck and dodge them. Also, can the speed of the spell be increased by how loud you shout the incantation, or how hard you flick your wrist (at the possible expense of accuracy)?

Also, what effect does gravity have on spells? Do spells like Stupefy follow a parabolic path, or do they go perfectly straight until they hit something? In a similar vein what is the range of "projectile" spells? Is it unlimited until they meet an obstruction, or do they dissipate and loose force with increasing range?

Other questions come to mind: Do spells have mass? Can the trajectory of spells be altered by high winds and rain?

Any thoughts?

Tim the Enchanter

[Inverarity]

The physics in Harry Potter really don't bear thinking about too closely. I have always thought of spells as being energy, which would imply not being affected by gravity (unless we're talking about a black hole). On the other hand, if they were literally energy without mass, then no one could dodge them, since they'd be moving at the speed of light.

Purely my own interpretation, but I tend to classify them into "fireball" type spells and "laser-beam" type spells. "Fireballs" are, well, fireballs, or anything else that might have some mass to it and be affected by gravity. These would behave more like projectiles.

But spells like Stunners and Killing Curses are always described as beams or flashes of light, which implies to me that they don't have mass. They may not actually move at lightspeed (if they really behaved like lasers, you couldn't dodge them), but I think if you shot a Stunning Spell or a Killing Curse into the air, it would just dissipate, it wouldn't come back down and hit someone.

As for range; who the heck knows? Aside from the Summoning Charm, we never see any spells that seem to have a great range. If you could Crucio or Avada Kedavra anyone you can see, no matter the distance, then I expect the Death Eaters would have been taking people out from miles away, with binoculars, and the wizarding world would have been a lot more paranoid. So I tend to assume that most spells have a fairly short range.

[JCCollier]

I agree with Inverarity that the physics properties of spells are purely for our own interpretation. I, apparently like both of you, prefer a frame of reference in my head as to how they work. This did not seem to trouble J.K. Rowling much.

At what speed do "projectile" spells travel

I agree with Inverarity in considering spells as energy. I believe the speed of spells is a constant, like the speed of sound or speed of light. Louder incantations, stronger wand movements, or even a more powerful wizard cannot increase it's speed, though they could increase it's power. As you remarked, if people can duck and dodge them, then we must assume this constant speed is fairly slow.

What effect does gravity have on spells?

I am going to agree with Inverarity's interpretation on this also. Gravity has no effect, just as it won't pull down a light beam or a sound wave. A wizard wouldn't calculate a trajectory like the arc of a cannonball fired at a target (though he may shoot ahead of a moving target like an airplane gunner would).

What is the range of "projectile" spells?

This is the only question where I think a standard law of physics does apply well. I also believe that a spell will dissipate, and the inverse-square law would be a consistent way to measure how spells are more powerful at close range and weaker as the distance of the target increases. The variance would be that a stronger wizard can cast a spell farther, just as a more powerful flashlight can cast a beam farther that a weaker flashlight (even though the speed of each beam is the same). Again I would agree that the books place an implied limit that spells are only effective within the immediate vicinity of the caster.

Can the trajectory of spells be altered by high winds and rain?

Sound waves can be absorbed by wind and light beams scattered by rain, so I would say these influence a spell's accuracy also. One might even consider a shield spell as a magical form of these natural influences.

My semi-physics question: When a spell dissipates, does it change to another form of energy, or just drift away as scattered 'magic' particles? Maybe the accumulation causes Global Charming?

[Hermoine Jean Granger]

Physics of spells!*grinsfromeartoear* I love this topic!

Physics, in canon, doesn't seem to have been paid much attention to. I think JKR considers all of the effects of spells to be part of "magic", which is the basic premise in HP. However, I have some ideas with regard to the functioning of spells.

I was wondering, at what speed do "projectile" spells travel?

I am not even sure if all spells are take a parabolic path. Most of them don't seem to do so, as far as I've noticed. Also, if the spells were projectile in nature, they'd have to follow laws of gravity, as a projectile motion depends on initial velocity and acceleration due to gravity in the direction perpendicular to the initial velocity.

I also have to disagree with the point made that Spells are just energy. I don't think that is so. Maybe it is based on mass-energy conversion. I mean, using Einstein's Theory of Relativity, you could consider the spells to be energy from the wizard, which is converted into mass in the form of particles, with the dissipation of heat or light(as applicable), and then back into energy as they hit the target. The wand could probably be used as a mass-energy convertor.

\randomtheory

Also, can the speed of the spell be increased by how loud you shout the incantation, or how hard you flick your wrist (at the possible expense of accuracy)?

In my opinion, no. I feel it depends on the concentration of your mind, rather than the strength of your voice. Hell, if spells could be affected by the intensity of your voice, Crabbe and Goyle should've been great wizards. However, I do feel that effects of verbal spells are more powerful than those of Non-verbal spells. Strong spells like Avada Kedavra and Crucio, seem to be usually said verbally, never non-verbally. Even Voldemort uses the Killing Curse while saying it aloud.
Basically, I think that it depends on whether you say it aloud or not, but it doesn't depend on how loudly you say it.

As far as the motion of hand is concerned, I think that spells would be affected by the type of motion, not the intensity, once again. A Levitating Spell would have to have a swish-and-flick motion, but I don't think it depends on how hard you flick your hand.

What effect does gravity have on spells?

I am continuing the theory that I proposed in the first question's answer. If energy is converted into mass in the form of particles, then they would be affected by gravity. This would then affect the range of the spell. If a spell were nothing but pure energy, then it could probably go on for ever(provided that the medium is vaccuum), if there aren't any obstacles.The particles, having definite mass, would be stopped due to internal resistances, and most probably forces of attraction and repulsion between two particles of the same kind. You could consider them as molecules and apply the Kinetic theory of Gases.

What is the range of "projectile" spells?
JCCollier made an excellent point in the previous post, and since I've got nothing to add, I won't repeat that theory again.

Can the trajectory of spells be altered by high winds and rain?
Wind, no. I don't think wind would have any effect on the trajectory of a spell, it would have an effect on the effect caused by the spell. For example, Incendio would be more effective in a place with higher velocity of wind.

Rain, yes. JCCollier explained that too.

When a spell dissipates, does it change to another form of energy, or just drift away as scattered 'magic' particles? Maybe the accumulation causes Global Charming?

I must say I love the idea of Global Charming, so I go with the scattering of particles theory.

\two knuts

[Ginny Weasley Potter]

Hehe, I just came across werewolf genetics a while ago and was all in with mutations and codons and stuff, now here's physics. And there you go, Hermione, your fav topic is here too .

Interesting... seeing this is physics week for me. My school is dedicating this entire week to physics tests. But here's a warning. Harry Potter and science disagree widely. I've noticed that with my irritatingly science-oriented brain. O_o Hmmm...

I was wondering, at what speed do "projectile" spells travel?
I can say that the spells do not take up a projectile motion. Gravity does not seem to alter their path. You can assume them to be using straight line motion.

I agree with Inverarity: spells look more like energy forms to me. They do not travel at a very high speed- we know that because the characters are known to duck and dodge them.

But then, spells can rebound upon reflecting surfaces too, as proved in DH. So that may be because they're particles of light energy... are they perhaps monochromatic beams of light with magical force directed by the wizard/witch...? That is probable.

>> Complete randomness

Also, can the speed of the spell be increased by how loud you shout the incantation, or how hard you flick your wrist (at the possible expense of accuracy)?
No... that's not right. Screaming an incantation does not alter the strength of your spell. It depends on mind power and emotions, according to me. People who have better control over their emotions make better witches/wizards. Flicking the wrist only ever mattered in one curse: Sectumsempra.

What effect does gravity have on spells?
I don't think it does. The spells, as I have said, seem like shots of light energy to me. They also don't take parabolic pathways, which explains that they are not affected by gravity.

What is the range of "projectile" spells?
I agree with Hermione Jean Granger and subsequently, JCCollier. There's nothing to add, here!

Can the trajectory of spells be altered by high winds and rain?
Taking forward my assumption of spells being forms of light energy, wind and rain are likely to alter the path of spells.

When a spell dissipates, does it change to another form of energy, or just drift away as scattered 'magic' particles? Maybe the accumulation causes Global Charming?
Global Charming? LOL. No... I don't think spells dissipate, or those stunners wouldn't shatter tiles and all, as they have done in the books. They just hit whatever comes on their paths.

>> Insanely random. But I like Global Charming!!!

[Tim the Enchanter]

Very interesting discussion forming here, and thank you all for the input!

Now, the way I see magic, there are two kind of spells. The first are what I call "projectile" spells (for lack of a better term), that shoot a beam or bolt or whatever of magical energy that has to come into contact with some object or person to work. We've talked about this kind, but perhaps we can discuss the other type now.

What I am referring to are... well, I don't know what to call them, really, but I think "Instantaneous-Effect" spells should suffice. These spells are the ones that have no visible sign of the magic apart from its effect, like changing the colour of something or transfiguring it. Now, how fast do you think the magic actually works, in this case? Is the spell perfectly instantaneous and put into effect the moment the incantation is finished? Or does the magic transmitted from the wand onto the object travel at the speed of light, or perhaps the speed of sound? Does this even matter?

I suppose not, but it's just a weird question to think about...

But to go back to beam-shooting spells, how fast do you think spells travel, if you had to pin an actual speed on it? 100 mph (161 km/h)? 200 mph (322 km/h)?

Here's another random question: Could magic follow different laws of physics? Aristotle's (384 BC – 322 BC) theory of impetus states that projectiles travel in perfectly straight lines (apparently he must have never thrown a rock in his life), travelling as far as their motive force, or impetus allows. The projecting force was thought to be something of a kind of fuel, in which it is expended at a constant rate, and once it runs out, the projectile just suddenly stops in mid-air and falls to the ground.

So, could spells work in a similar way? Could the skill and conviction of a wizard affect the amount of "impetus" in a spell, which is expended at a constant rate as the spell travels at a constant speed? Would the spell just disappear whenever it ran out of force? I guess we already answered this question, but I think this Aristotelian law of physics could be used to explain spell dynamics in Harry Potter. Any thoughts?

And here's another random question: can nuclear fission and/or fusion be achieved by magical means? What do you think could be achieved with magic in Muggles sciences, assuming there were wizarding physicists or chemists?

Tim the Enchanter

[Inverarity]

Well, the simple answer to your questions is that magic in Harry Potter is inconsistent and clearly defies the laws of physics in all sorts of ways. I seriously don't think Rowling ever sat down and thought through her magic rules beyond the needs of her plot.

So, you can answer your questions pretty much any way you like that doesn't defy canon.

But I'll give you my personal interpretation (i.e., the assumptions I make in my own fics).

What I am referring to are... well, I don't know what to call them, really, but I think "Instantaneous-Effect" spells should suffice. These spells are the ones that have no visible sign of the magic apart from its effect, like changing the colour of something or transfiguring it. Now, how fast do you think the magic actually works, in this case? Is the spell perfectly instantaneous and put into effect the moment the incantation is finished? Or does the magic transmitted from the wand onto the object travel at the speed of light, or perhaps the speed of sound? Does this even matter?

I might even put the Cruciatus Curse in this category. I don't recall it ever being described as shooting a beam or projectile or even producing a visible effect -- the wizard just points his wand, and causes pain.

To answer your last question first: it matters if you think these spells can be dodged. We never see anyone dodge a transformation or a Cruciatus Curse. For that matter, I don't recall anyone ever "missing" with a transformation or a Crucio.

Now, I tend to think they can be dodged (because if they are undodgeable and they never miss, wouldn't wizards always use those spells in battle, in preference to spells that can miss or be dodged?). But if there's no visible effect, it would obviously be harder to dodge them. You'd have to see the wizard pointing the wand, or else just move in an evasive manner.

Likewise, if you think they can be dodged, then they can't move at the speed of light.

On the other hand, I do imagine there are ways to produce an "instantaneous effect" that is unaffected by distance. We are talking about magic, after all. If you really, really need a pseudo-physics explanation, think of entangled quantum particles.

But to go back to beam-shooting spells, how fast do you think spells travel, if you had to pin an actual speed on it? 100 mph (161 km/h)? 200 mph (322 km/h)?

Faster than 200 mph, and dodging is pretty much impossible.

By comparison, the world's fastest baseball pitchers can just barely break 100 mph, and even low-velocity bullets approach the speed of sound.

Here's another random question: Could magic follow different laws of physics?

Sure it could, and probably does.

Aristotle's (384 BC – 322 BC) theory of impetus states that projectiles travel in perfectly straight lines (apparently he must have never thrown a rock in his life), travelling as far as their motive force, or impetus allows. The projecting force was thought to be something of a kind of fuel, in which it is expended at a constant rate, and once it runs out, the projectile just suddenly stops in mid-air and falls to the ground.

I.e., the "Wile. E. Coyote running off a cliff" model.

So, could spells work in a similar way? Could the skill and conviction of a wizard affect the amount of "impetus" in a spell, which is expended at a constant rate as the spell travels at a constant speed? Would the spell just disappear whenever it ran out of force? I guess we already answered this question, but I think this Aristotelian law of physics could be used to explain spell dynamics in Harry Potter. Any thoughts?

I think the power of a wizard could certainly affect the range which he or she can effectively project a spell. As mentioned before, I think spells dissipate when they reach the limits of their effective range, rather than falling to the ground like bullets.

And here's another random question: can nuclear fission and/or fusion be achieved by magical means? What do you think could be achieved with magic in Muggles sciences, assuming there were wizarding physicists or chemists?

To me, that's more of a thematic question than a scientific one. Scientifically, I think there are all kinds of possible intersections between magic and Muggle technology.

Now, there's certainly a place for mixing magic and technology. It happens in comic books all the time. It happens in Buffy the Vampire Slayer. It happens in a lot of other genres.

To me, it just doesn't fit in Harry Potter. That's not to say a HP fanfic where wizards collaborate with scientists might not be really cool. Logically, you'd think some Muggle-born wizards would get the idea of introducing technological marvels like ballpoint pens to the wizarding world. But, such a story would have a very different feel from the Harry Potter universe we're used to. It would be pretty heavily AU. I have a hard time imagining the Muggle and wizarding worlds coming together and still "feeling" like Harry Potter.