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In my world I have characters that can control magic to achieve different superpowers. One of these magic types is light magic. Light magic has the ability to generate light in the form of lasers and manipulate light. They can also manipulate the em spectrum in the form of x-rays, microwaves, ultraviolet, etc. I need this light mage to fly for story reasons, but I cannot find any good ways for them to fly except through the use of a light sail which can only work in space.

So how could a light mage fly at relatively high speeds?

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Method 1: Burevestnik-style (magi)nuclear ramjet

Assuming you're okay with the Necessary Secondary Superpower that light sorcery comes with Newton's Third Law equipped (aka magic light may push back on objects), you can conjure a sort of a nuclear ramjet. Nuclear ramjets work by scooping up air through a funnel-like inlet and heating it through a series of heat exchangers carrying away hot coolant from the reactor's core, then expelling hot air through the nozzle. As long as the reactor can heat the air, a ramjet's range is virtually indefinite.

With sorcery, you can replace steel ducts with conjured hard light and heat exchangers with carefully-controlled bursts of magic light in the absorptive part of the spectrum. This works up to and well into the supersonic range, assuming sufficient thermal output of the sorcerer.

This is by far the most energy-efficient propulsion method. However, it requires some serious aerospace engineering effort, or at least some knowledge of it and a lot of trial and error. Initial airspeed is also required, which can be both a plot-relevant obstacle and an opportunity for the Rule of Cool.

Method 2: Magnetic Nozzle Torch Drive

This is generally done in sci-fi with fusion drives; however, your sorcerer doesn't actually need nuclear fusion for this to work, just reasonably hot plasma. What your sorcerer needs is an EM nozzle (or an EM shield) to stand on, and magic heat to convert air into plasma. As soon as the air becomes plasma, it gains an internal magnetic field that the sorcerer can repel himself from using the EM nozzle/shield.

This method is way more expensive energy-wise than the ramjet and suffers from diminishing thrust with increasing airspeed: as your sorcerer goes faster, there's less and less air behind the nozzle/shield to heat unless the sorcerer creates an intake, where this basically becomes Method 1 with a whole lot more excess heat.

However, it requires little to no engineering knowledge (but a lot of magic lore to avoid incinerating oneself in hot plasma) and works at zero airspeed. Obviously, your mage also risks looking like a cross between the Iron Man and the Rocinante, which may be or may not be what you're aiming for.

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Matter-Light Conversion

They don't fly in the classic sense, they turn themselves into light. This light travels from A to B in a straight line, then turns back into matter. To the standard eye, that is pretty much teleportation, and because most mages don't like falling or getting refracted to bits when they hit an object, so they start at high towers and only "beam" themselves to a spot they can see that is about 20 cm above the floor. Beam because they turn into a light beam.

More daring light mages make this also work for a means of movement that mimicks flight. To stay in the air over a place, they beam themselves up, and as they start to fall, they beam up again and again. By this, they can also get around obstacles in the line of sight and to places too far to see and aim their hops from their starting point. The downside is, that they are constantly falling between those short spell uses, which will be very nauseating to many.

More expert mages manage to not just project as light and to not puke from constantly beaming themselves into the air, they also manage to alter the speed of light in a medium (see Slow Light) and bend its movement (see gravitational lensing). Those mages manage do not just beam themselves in a straight line like beginners or achieve quasi-flight. They turn into light, move as a somewhat slow packet of light (down to about 17 m/s - or typical car speeds) that curves around corners and still passes through transparent materials and small holes, and then rematerialize at the destination. Such a mage might even observe the area their light package travels through.

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  • $\begingroup$ What do you think of when you say "somewhat slow packet of light"? If it is only somewhat slow as compared to light speed they would also have to have incredibly fast reaction speeds to be able to move in ways other than beaming. $\endgroup$
    – Informer
    Mar 4 at 17:50
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    $\begingroup$ @Informer under the right circumstances, light propagates through a medium much slower than vacuum. The slowest achieved so far is 17 meters a second - which is about 61 km/h or 38 mph $\endgroup$
    – Trish
    Mar 4 at 18:36
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All of these use the ability of light to heat up a substrate and generate power or lift. This is more efficient than using the momentum of the photons directly, since reflecting a photon only absorbs a small amount of its energy (the rest has to go to re-emitting the photon back out!) while absorbing it as heat gets you much higher efficiency.

Gliding with light-caused thermals.

Use a mundane unpowered glider/paraglider/hang-glider. When you need to gain height/speed, find an unoccupied, hopefully-nonflammable patch of land, and use light powers to heat the ground up, causing convection. Use the updraft to gain height and speed. Depending on your sorcerer, this is either "extra-sunny day" hot or "reduced to magma and glass" hot.

Ballooning with light-caused hot air.

Hot air balloon, a black-painted radiator in the middle of the balloon, when you need to ascend, shoot light into the radiator and heat it up, heating the air.

It's all heat engines eventually, isn't it.

Some kind of early propeller plane, with a heat engine driving a propeller. If you want steam, something like a condensing steam engine. Heat is delivered by laser to the boiler, which boils the water. Or you can use air directly and just heat it up, solar-powered Stirling engine style.

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    $\begingroup$ Ballooning, sure. Steam engine propeller plane, absolutely. Flying on thermals that you made by heating up the ground - hang on pal, what exactly is your power output in gigawatts? Sunlight is about 1 kW/m^2 for a rough order of magnitude, and you would have to apply that power over a large area so the column of air keeps rising and you can spiral your glider around in it. If there's any wind, your air column would just be blown away. $\endgroup$
    – causative
    Mar 5 at 8:01
  • $\begingroup$ @causative yeah for SURE. But the other answers are "solar sail in atmosphere" which are similarly gigawatts-level silly. and I felt like heat engine/balloon didn't have any "visible light" aspect to them. I felt like one of the answers needed to have "oh dang, that's a freaking wizard shooting a ginormous light-beam" :P $\endgroup$
    – Kaia
    Mar 5 at 18:15
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Walkin' on sunshine (oh oh oh)

The mage is capable of hardening the beams of light by nudging the light to act more as a particle than as a wave. The magnitude of this effect can range anywhere from creating thicker regions of air that the mage could glide on with a dedicated glider or an improvised controlled fall using their cloak - or to calling down a rainbow of light that they could simply walk upon, which would have much the same effect as flying, but certainly look different.

It's a trick

The mage can't actually fly, but is using a prism-like effect to bend light and make it appear as though they are suspended in mid-air. In reality, the mage is getting out of dodge using a more conventional method.

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  • $\begingroup$ I love the trick suggestion, and have just one thought on walking on sunshine. Given that certain wavelengths of light are invisible to humans, couldn't the mage make the invisible light act more like particles then Naruto run to emulate flight? $\endgroup$
    – Alendyias
    Mar 9 at 1:46
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The mage turns themself into light. A light mage could projectate themself to any place in high speed (speed of light). If you consider this speed to be so high, make the mage have a little mass to reduce the speed.(in order to travel at the speed of light, a object can't have any mass). Make it that the light mages turn themselves into some form of light with mass, so they can't travel at light speed, but the mass is still lighter than the air, so they can fly and they are not heavy in Earth's gravity (or similar one).

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If your character is limited to generating light, the best you could get is to have them wear some kind of engine where light provides heat to turn a propeller or turbine. They would in effect be wearing a jetpack, or be strapped to an ultralight.

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Laser Propulsion

Using the concept of laser propulsion, your mages are basically parasailing. Unlike parasailing, due to the use of light as a direct propulsion, they can fly quite fast.

  • Mage steps into a harness that has the light sail.
  • Mage creates a ferocious amount of light directed into the light sail.
  • Mage controls the light sail via cords like a parachute or by directing the light.
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    $\begingroup$ Though in-atmosphere, this would probably have ... exciting side effects. $\endgroup$
    – jdunlop
    Mar 4 at 18:42
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    $\begingroup$ Since the question includes "except through the use of a light sail" this answer is explicitly not what OP is looking for. $\endgroup$
    – SPavel
    Mar 4 at 22:33
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    $\begingroup$ Of course, to generate enough light pressure to lift a 50 kg light mage on a 15 square meter wing (hang glider size) against the force of gravity would require roughly 10 GW of incident laser power. That ignores the weight of wing and harness, supposes that 100% of the light's momentum is converted to upward pressure on the wing (as opposed to instantaneously vaporizing both mage and wing along the way to igniting the atmosphere, say), and doesn't account for the extra energy needed to actually move forward. $\endgroup$ Mar 4 at 23:15
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    $\begingroup$ You're right @JohnBollinger actually I calculate it much worse, for 500 nm light it's 200 GW required! also if a light sorcerer has 200 GW power output for flying this is probably a major plot hole, i.e. why don't they instantly vaporize all their enemies with that power! my calculation is 500 N / ((10e-27 kg m/s) / 2.48 eV), i.e. Force / ((Momentum per photon) / (energy per photon)) $\endgroup$
    – causative
    Mar 5 at 6:27
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    $\begingroup$ Laser propulsion that has been tested in-atmosphere in real life does not use light sails because of the ridiculous amount of power that would be needed. Instead, in-atmosphere laser propulsion focuses the laser onto a solid propellant target that will be ablated away, and the ablation of the solid target creates exhaust and thrust like in a normal rocket. It would be hard to "sail" like this because if the sorcerer is hanging on cords behind the ablation target, that means he's inside his own rocket exhaust, which would cause some mild discomfort and melt his face. $\endgroup$
    – causative
    Mar 5 at 6:38
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Manipulation of Fundamental constants

Light Mages generate radiation by altering fundamental constants in their vicinity. This can cause matter and energy to interact in controlled but unusual ways allowing for what appears to be spontaneous emission of radiation of various types (light, xray, etc).

The bearable lightness of being a Light Mage

By reducing the value of gravitational attraction in their immediate vicinity they can make them selves effectively lighter (haha sorry not sorry for the pun) to the point of being practically weightless.

Leaf on the wind

Similarly alterations to the Planck constant in front and behind the mage could make low and high pressure areas which would allow for slow acceleration, controlled gliding and floating.

The Fast and Spurious

Sometimes gently floating forwards isn't fast enough, and you need to get there now, no problem for a light mage, as they can just alter vacuum electric permittivity and vacuum magnetic permeability causing large energetic atmospheric expansion behind themselves and propelling themselves forwards with much higher acceleration.

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The sorcerer himself is a photon rocket

Say the sorcerer has laser power output on the scale of 150 GW - 1 TW. Well, a laser that powerful comes with a lot of recoil, because photons have momentum. He can fly through the air on the recoil from the laser.

Another answer had the idea that the sorcerer could aim his laser at a light sail that he is hanging from, and travel that way. For the sail to produce enough force, this will also require in the area of 150 GW - 1 TW power output. But this is like powering a sailboat by mounting a fan on it and blowing air at the sail! It doesn't work because the force pushing forward on the sail is also pushing backwards on the fan, so they cancel out. It's better to point the "fan" backwards and do away with the sail. The "fan" in this case is an ultra-powerful laser, which makes the sorcerer a photon rocket.

Apart from making the sorcerer fly, as a side effect the exhaust aimed at the ground will turn roughly 1000 tons of stone into lava per second. So it would require a fairly high power level for the sorcerer and be destructive to the environment.

Physics explanation:

Let's say it's a green laser, with 500 nm light. This page gives the momentum of a 500 nm photon to be 1.33e-27 kg m/s, and the energy to be 2.48 eV. Force = (change in momentum) / (time) = (photon momentum) * (number of photons) / (time) = (photon momentum) * (power output of laser) / (energy of photon). Rearranging the equation, (power output of laser) = (energy of photon) * (Force) / (photon momentum). If we want 500 N to lift the sorcerer's weight, the laser power must be 2.48 eV * 500N / (1.33e-27 kg m/s). Plugging this into Wolfram Alpha gives 150 GW. The sorcerer would need a multiple of this to do more than lift his weight and fly fast.

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  • $\begingroup$ If he tried to fly wouldn't he destroy everything in the area? $\endgroup$ Mar 7 at 18:03
  • $\begingroup$ @Coolcats112 Yes he would, and if he had a fight with that level of power, he would be able to vaporize his enemies instantly. But the "sail" has the same problem of amount of power needed, plus new ones. Unless you say these light mages are able to shoot light that has a lot of extra momentum at a very low energy compared to normal light, in which case the rocket could work without destroying everything (if there is recoil) or the sail could work (if there is no recoil). $\endgroup$
    – causative
    Mar 7 at 23:19
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Frame Challenges Incoming

I need this light mage to fly for story reasons

Do you, though? What is the problem that requires your mage to fly, and are you sure flight is the only answer?

There is a balance to be had in every Sci-Fi/Fantasy story. The more detailed you get with explanations of why magic is actually science in disguise, the more you shoot yourself in the foot with plot holes. Are you more dedicated to the hard physics of hard magic system, or to the story you are trying to tell?

I recommend you either let your magic system drive what is possible in your world (air mages fly, light mages don't, go a different path), or let your story drive the outcomes of a more vague system (light mage fires magical beams from his hands like Iron Man). Even the best authors stumble when they try to do both.

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