Kinda like Tachyons.
Not the first time though.
Actually, the ancient Hindus intuited the structure ~ they called it "Earth" which was bound between "The Heavenly Realm" and "The Demon Realm". Buddhism expanded on that a bit, and Zoroaster kind of turned it into a Dualist sort of Heavenly existence where you had the God of Light and the God of Dark ~ but as an explanatory tool it was all pretty much the same thing.
One of the major discoveries of our time is that of "the Vacuum". It's filled to the brim with particles that flit in and out of existence. It's a vast storehouse of energy. Doesn't matter where you go it's there ~ and if you tweek it just right those particles will pop out for a short time and then go back in.
The physicist/mathematicians (the high priests of our time) determined that we would be able to trap some of these virtual particles in pairs ~ due to their nature as either MATTER or ANTIMATTER ~ it's supposed to look like two phtons.
So, they did just that ~ and that satisifies the ancient's view of existence ~ two realms, and reality ~ we are in reality but we can communicate, sort of, with the other two realms.
There are "creatures there". They can walk in on us and make your virginal daughters instantly pregnant ~ and that sort of thing. Or they can just appear out of nothing and send us messages about going to church and so forth ~ then disappear.
They may be interested in our need for steam heat for apartment buildings in fact.
There should also be some situations where the folks on the other side do not intend good outcomes for our efforts.