so I am a humanities student with little knowledge of physics or any science but I want to create a Dungeons and Dragons campaign that I will also use in a novel I'm writing. In it, my campaign's reality is based on a modern-day world like ours with the same history and discoveries (so the same reality) that somehow mixes with a world whose very essence stems from a very distant reality, allowing things such as magic and monsters typical of a fantasy world to exist. I already have a fantasy explanation as to how they collided which will work for a campaign, but if I want to write a novel on it, I will need to be able to convey how the collision of these realities was detected and analysed by scientists of our reality as well as their own theories to how these two realities could have collided.

I also want to know if there are any theoretical repercussions explored by modern-day scientists to two realities meshing into each other to form one brand new reality. If anyone could either explain these to me or suggest good resources to study them from it would be much appreciated.

  • $\begingroup$ If the worlds are colliding via magic, it may not be possible for scientists to detect it. We don't have anything to give us a precedent in real life for how two realities occur, so this question probably isn't even answerable. My suggestion is to not have science be able to detect the collision, as the collision is magic-based, but instead pick on odd phenomena and anomalies that occur before the collision with no way to explain them. $\endgroup$ – Halfthawed Jan 17 '20 at 13:08
  • $\begingroup$ It might be worth thinking carefully about the boundary conditions where the two realities meet and how a different physics would interact with ours. As Halfthawed said a proper answer may not be possible but I would suggest that any dimentional rupture should at least have an infinitely sharp edge so you would want to get to close to it. $\endgroup$ – Slarty Jan 17 '20 at 14:08
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    $\begingroup$ Have you read Liu Cixin's Three Body Problem? The first half of the novel is a splendid description of how a foreign reality is detected and analysed . . . in Red China. (It turns out it's not a foreign reality, just plain aliens, but that does not become apparent until later.) $\endgroup$ – AlexP Jan 17 '20 at 15:29
  • $\begingroup$ Not exactly a "different reality" but you can have a look at the Shadowrun tabletop RPG. The backstory is very similar to what you describe - Earth as we know it today suddenly starts experiencing weird stuff. Some people are born really short and stout, others tall and slender, with pointy ears, others still big, rough and with horns. Dwarves, elves, and orcs. Moreover, more and more people show the capacity for magic. The world becomes an amalgamation of high tech and fantasy races + magic. In Shadowrun that's not a "different" reality but ancient magic returning to our world. $\endgroup$ – VLAZ Jan 17 '20 at 17:27
  • $\begingroup$ It might be worth your time to check out the Apprentice Adept series by Piers Anthony Split Infinity (1980) Blue Adept (1981) Juxtaposition (1982) Out of Phaze (1987) Robot Adept (1988) Unicorn Point (1989) Phaze Doubt (1990) $\endgroup$ – Laird Bruce Boughner Jan 17 '20 at 22:45

It'd completely ruin scientists' day. (Maybe even an entire week)

Imagine for a minute Earth in its current shape. You know energy can't just appear or disappear. It has to go somewhere, be it in the form of heat, motion or light (not just visible, the whole electromagnetic spectrum counts for this purpose). You also know mass/matter can't just appear or disappear. It's a comfortable, stable place.

Then magic is thrown into the mix. Suddenly energy can be generated out of thin air. Matter can be created, manipulated (which would always require energy) or be vanished (Which conflicts with conservation of mass). Not to mention the existence of different planes of existence in the D&D realm from whence a conjurer summons his creatures would pretty much ruin everything we know about the universe (or in this particular case, the multiverse).

With our current sets of natural laws in place, making matter "appear" would require obscene amounts of energy. Following Einstein's E = MC² equation we can extrapolate the energy required to convert energy to mass in the current reality. The equation in this form only works for matter in a 0 energy state. (So your matter would be 0K in this example.)

For one gram of matter to be "made" out of energy roughly ~1.8×10^14 joules is needed. To give you an idea how much that is, a kiloton (1 million kilograms) of TNT exploding would generate 4.184×10^12 joules. Almost 2 orders of magnitude less than the energy needed to make a single gram of matter out of energy.


Now we covered the nasty reality interfering aspects, it's time for better news. In D&D lore it's said there is a "weave" from which people (mainly arcane casters I believe) draw their magic. Without going all too deep into strings building up particles and the like, it could simply be stated that some people with a certain gene expression could interact with this weave.

Dark matter?

In our own reality there is plenty of mystery left to employ in this particular situation. A cloud of dark matter could have collided with Earth making for all sorts of whacky reactions, perhaps this could be your source of the strange interactions so different from the normal laws of physics.


Divine spellcasters might still pose a problem. You haven't specified in your question whether or not a god or multiple deities are present in your setting and honestly I have no idea how to explain this away other than "somehow these deities can now exert their influence here."

Maybe their sphere of influence is confined to the bounds of the dark matter area mentioned above.

Things get really strange when D&D magic is being tossed in the mix with the actual laws of physics. Hopefully this will give you some ideas which direction you can take with your approach. This surely isn't the only way to deal with this situation. I bet some other creative souls on this site could help you come up with some other really cool ideas. But I hope it helps you regardless.

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    $\begingroup$ "I have no idea how to explain this away other than "somehow these deities can now exert their influence here."" well, in D&D anybody can become a god. Well, not that it's easy but many actually started as mortals. So it might be the case that just new ones "ascend" with the merge of the realities. $\endgroup$ – VLAZ Jan 17 '20 at 17:23

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