In another universe in which humans may exist but did not evolve, the laws of physics allow phenomena that we in this universe would call magical, where matter and energy may be moved, transformed and manipulated at a distance without passing through the intervening space by interactions of exotic particles that change the way that the usual laws of physics operate.

However, most objects and life forms don't contain any of these exotic particles, and this would include humans. Even if humans could contain - or hold objects containing - such particles, manipulating them in the precise ways necessary for them to cause anything but the simplest magical effects would be beyond human capabilities.

However, humans have discovered the ways that such particles may be generated and manipulated, by observing life forms that did evolve in that universe to be able to produce some 'magical' effects.

This has led to the creation of 'Magic Engines', which are huge, partially organic living, semi-sentient objects that are able to read the intentions of their human creators and operators, and produce magic-like effects upon command, even where their users are a considerable distance from the Magic Engine.

The Magic Engines might draw a small amount of energy from their users as a 'toll' for their use, but would be able to obtain the energy necessary for their tasks from sources external to the users.

Each Magic Engine would have its own way of recognising authorised users, whether by initiation rituals, inherited traits or possession of physical keys or tokens. A person able to use a Magic Engine would be able to do so by virtue of being constantly watched by that Magic Engine in most cases, though some may be able to have their attention attracted to an unobserved user by use of a 'Magical Key', an object that causes an effect that attracts the engine's attention.

Each Magic Engine would have limits on concurrent requests, individual request and total request energy throughout, capabilities and would vary in their command interface and ability to retain user-specific or universally-applicable data.

Some Engines with a highly restricted user base may be able to produce very powerful and optimised effects, while others may have multiple levels of user access, may allow many weak concurrent effects to the general public, may offer increased capabilities to frequent users or may have other individual features. Some may be smarter than others, and can produce more complex effects with less command input than others.

This was inspired by Eliezer Yudkowski's Harry Potter and the Methods of Rationality fan-fiction, but expands upon that work's passing mention of the concept, but this question should not be considered to be about the HPMOR universe.

So, my question is: Is this a workable way of making the quantum-level physics of this universe work as 'classical fantasy' personal magic, and are there any ways in which this idea can be improved?

  • $\begingroup$ Yes, it could be improved in a myriad of ways $\endgroup$
    – Kilisi
    Aug 16, 2023 at 11:55
  • $\begingroup$ A useful thing to think about with magic systems is to expressly state something. What are the unavoidable limitation inherent in my system, what cannot be done at all AND what can only be done by highly specialized user/engines. $\endgroup$
    – John
    Aug 16, 2023 at 14:15

2 Answers 2


When to Worry About New Physics in a Setting

I've seen enough similar questions to this now that I think I can safely answer them all following 4 simple rules:

  1. If you need to modify the rules of physics on a universal scale, add new rules while leaving all the other rules of physics unchanged.
  2. If you must change the existing rules of physics, do it only in an area of effect.
  3. Only break the first 2 rules if it is your intention to make a place that things from our universe can not survive in.
  4. Maintain internal consistancy

Any time an author tries to change the way the fundamental forces work at a universal scale, even a little bit, it always has some vastly consequential, life ending, unexpected consequences that are impossible to fully predict. However, any time an author says that all of the current rules of physics still apply, except now there is this new thing that does what I say it does, then your setting will generally be believable. This is because the new rules are YOUR rules. They work how you describe them as working which makes them incontestable because no subject matter expert from our world can actually say, "If this were a REAL Magic Engine, then it would actually work like...".

Why Magic Engines work as described

Right away, we know Rule 3 does not apply here because humans can't live in a universe that does not follow human physics. Rule 1 is satisfied by the fact that these exotic particles are essentially inert until acted on. So, even though they are everywhere and they CAN change the fundamental laws of physics, they in practice are limited to causing local area effects. That makes this what I would call a Rule 2 Physics modification. Since the rules of physics are only being changed inside of self-contained areas, it does not matter if that modification could cause a star to go super nova or a person to be ripped apart at a molecular level as long as the effect isn't going around nilly-willy consuming whole stars and planets, your universe remains a habitable setting you can tell a story in.

Beyond that, all the rules you have about how magic engines work are 100% authors choice because YOU are the one creating the rules, what ever you say goes, and no limiting preconceptions of what we know about our world apply to them.

This leads to rule #4. While you have the authority to say these things follow any rules you want, you need to be very careful to follow your own rules. The biggest reason authors mess up the laws of magic is not because what they say contradicts science, but because they contradict themselves.

Since you bring up Harry Potter, consider Thestrals as a example of what not to do. They are magic flying horses that you can only see if you've witnessed death. Nobody contests this fact regardless of what an outlandish mechanic that is, but where J. K. Rowling went wrong was making it so that Harry Potter, who saw his parents murdered as an infant could not see the horses from the very beginning.

In summary, as long as you stay internally consistent with your plot, your magic engines will work out just fine.

  • 2
    $\begingroup$ Actually the bit about the thestrals was 'witnessed and understood death', though I also would agree that it's a hasty retcon on JKR's part. I certainly don't intend to do anything that arbitrary. $\endgroup$
    – Monty Wild
    Aug 17, 2023 at 4:42
  • $\begingroup$ "However, any time an author says that all of the current rules of physics still apply, except now there is this new thing that does what I say it does, then your setting will generally be believable. " - But only if you don't go into details. You can specify gross effects, but don't try for more than the most superficial explanation of what is going on. It is certain that readers will realize that you haven't thought this through. Also, make the gross effects so dramatically entertaining that the readers get swept along by the story and don't have an inclination to start thinking. $\endgroup$ Aug 18, 2023 at 14:19
  • $\begingroup$ @WhatRoughBeast Very true. My favorite example of this is the inertia dampeners from StarTrek. Gene Rodenberry wrote a lot about how certain technologies in StarTrek worked, and they all have been ripped apart in discussion forums, but when asked how inertia dampeners work, his response was "the work very well" ... it is to this day one of the least contested ST techs simply because he gave no attestation about how it worked, only that it did work. $\endgroup$
    – Nosajimiki
    Aug 30, 2023 at 13:53

Yes, it is definitely a workable way. Fundamental forces of nature operate by such a kind of 'exotic particles' mechanism. With the exception of gravitation which is yet to be reconciled with the quantum theory, the electromagnetic, weak and strong nuclear force work with the exchange of particles called bosons. For example, electromagnetic force operates when there occurs exchange of virtual particles called photons.

There could be a way in which you can make your engine more efficient after taking the toll. Let there be a net negative energy among the exotic particles with respect to each other. And the toll, which is a different energy as it is derived from humans, be some positive energy. Remember that the more negative the energy, the more potent but more dormant it is. So when toll is added to the negative energy of the particles by the engine, it's dormancy is converted to useful work which in this case would produce magical effect.

We know that a perpetual engine is beyond conception in our physics so when the net relative energy of the exotic particles reaches 0, they are no more useful (only temporarily though) and the engine goes out. However, it has already served our purpose to do magical effect. After some time, the effect of the magical action would blend into the universe and the exotic particles would start to gather their relative negative energy again to be used again by the engine.

Speaking of the engine construction, since you mentioned they are partial organic, sentient and constructed by humans, you can make an engine with a human DNA. If the engine is constructed with the DNA of a person, this would provide an authorised access to the person whose DNA it contains and also his blood-relatives as special personnel. The 'Magical Key' you mentioned could be the DNA fingerprint.

The fact that an engine could constantly watch it's parent person's action explains why it works so efficiently to that person. It is because the task to focus and collect data has been narrowed down to a single person via DNA fingerprint. This would also make that engine very powerful being operating in accord to a single person.

You may construct an engine with more than one person's DNA with everyone having distinct DNA. But then many traits could get their counter-traits and therefore diminishing the efficiency of the engine. If the multiple DNA's are matching or similar, but obviously belong to different people, it will just have a broader spectrum of people to observe and slower to adapt.


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