For general readers:
Is it possible that the particle physicists hard at work near Geneva, Switzerland, at the laboratory known as CERN that hosts the Large Hadron Collider, have opened a doorway or a tunnel, to, say, another dimension? Could they be accessing a far-off planet orbiting two stars in a distant galaxy populated by Jedi knights? Perhaps they have opened the doors of Europe to a fiery domain full of demons, or worse still, to central Texas in summer?
Mortals and Portals
Well, now. If we’re talking about a kind of tunnel that human beings and the like could move through, then there’s a big obstacle in the way. That obstacle is the rigidity of space itself.
The notion of a “wormhole”, a sort of tunnel in space and time that might allow you to travel from one part of the universe to another without taking the most obvious route to get there, or perhaps to places for which there is no other route at all, isn’t itself entirely crazy. It’s allowed by the math of Einstein’s theory of space and time and gravity. However, the concept comes with immensely daunting conceptual and practical challenges. At the heart of all of them, there’s a basic and fundamental problem: bending and manipulating space isn’t easy.
The amount of energy required to bend space into a new shape can be enormous. For example, if we want to get a rough idea of what it might take to make a wormhole whose exit is the size of a doorway, let’s ask what it takes to make a black hole of that size. A doorway-sized black hole would have mass comparable to that of the planet Saturn, a hundred times larger than our own planet. While CERN’s electricity budget is big, you’ll run through it in a hurry; there’s not that much energy on Earth, or even in Earth. Even if you magically converted the Earth’s entire rest mass, via E=mc2, into the energy of two beams of particles, and funneled the two beams into a small place all at the same time, you still couldn’t even make a human-scale black hole.
Is there another approach? Sure! All we have to do is obtain a Saturn-sized planet and shrink it down to the size of a dinner table. I’m not sure yet how we’ll obtain the technology or the energy required to crush something that large, but, hey, let’s write a grant proposal and maybe Elon Musk will fund it. At least it shouldn’t be too hard to get the planet; we know nowadays that the universe has lots of them out there, ripe for the taking. Be warned, though: a check of Amazon reveals that there are currently supply chain issues, and delivery is not free even with Amazon Prime. I suspect, also, that environmental agencies are going to insist on a lengthy permitting process if we want to bring something with so much mass into the Solar System. There is, after all, the risk of kicking the Earth out of orbit and into the Sun.
These challenges with black holes are bad enough, but at least we know that nature does make big black holes. There’s no evidence that nature has ever made a wormhole that you could actually travel through, and it’s not at all clear how humans could make one even in principle. Moreover, were scientists to make one, they’d find it very hard to control. In science fiction, portals sit on the ground and wait for you to walk through them. In reality, a wormhole’s far less polite, with no intention of staying put on the Earth’s spinning surface, and with no qualms about ruining your laboratory and a lot more all around it. A human-sized doorway to somewhere else would represent a risk to the entire planet’s present and future, so you’d have to store it far away in distant space [note that CERN does not deal in space, so this is ESA’s or NASA’s problem]. And don’t go very close unless you know what you’re doing; you could easily fall in and never return.
But even if we can’t have big wormholes, what about a wormhole the size of, say, a virus? Maybe scientists could be making those? Hmm… perhaps dangerous pathogens could leak through to Earth from a distant planet’s bachelor’s refrigerator?
Well, even to make a black hole the size of an atom, far too small for a pathogen, lies far beyond the capabilities of CERN, even in extremely optimistic scenarios. Lots of energy would have to be focused all at once into an atom-sized region. While CERN’s proton beams do carry as much energy as a freight train, that energy is spread out around 15 miles (27 km) of the circular tubes that make up the Large Hadron Collider. It’s not squeezed, or squeezable, into an atom-sized box. What CERN can actually do with its beams doesn’t even come close to what is needed.
And again, even if you could make a black hole this size, what next? You still couldn’t control it. Such a tiny thing with so much more mass than a typical atom would sink into the Earth or fly off into outer space, unconstrained by the walls of a box or of a room.
So what about a wormhole this size? This requires somehow making a space tunnel with two atomic-sized ends, and ensuring that you don’t lose track of the first end while also sending the second end far, far away to somewhere interesting, rather than to a random location in the universe’s vast tracts of empty space. We have now moved beyond fiction to the land of silly.
You can be cavalier with space in science fiction, but in the real world, space isn’t simply going to bend to your whim. Rest assured, CERN scientists are not making literal portals to anywhere.
A Couple of Rabbit Portals
As with any rich topic, there are many other alleyways to explore here. But today I’ll limit myself to a paragraph about two of them.
There actually is something that CERN scientists might encounter that scientists sometimes call a “portal”. But let’s be very clear: it’s not what science fiction or even English means literally by “portal.” This figurative portal isn’t like a tunnel or doorway, and it’s not something we, or even elementary particles that we’re made of, could go “through”. It’s simply a means by which familiar types of particles could be converted to or interact with new types of “hidden” particles, and vice versa. (In fact, we only exist because of a portal like this, albeit a particularly open one. You can view the electromagnetic field and its particle [the photon, the particle of light] as a “portal”; without it, quarks and gluons would be nearly hidden from electrons, and not only couldn’t you easily produce electrons from quarks or vice versa, their interactions with each other would be so weak that atoms could never have formed.)
Meanwhile, confused science fiction stories notwithstanding, no one will ever make “a portal to another dimension”, because you don’t need one. You need a portal to go to another place, but another dimension is not a place, it is a direction. The dimension is already there, sideways to the ones you’re aware of. You and I usually wander on the two-dimensional surface of the Earth, because various forces trap us there. But if we want to move in the third direction — up or down — we don’t need a doorway or a tunnel to get there. We just need energy — energy for jumping up, or energy for digging down, or a rocket’s energy for flying away. Similarly, if the universe has additional dimensions — additional directions which we can neither see nor feel but in which we could move — then what we need is a lot of energy so that we can try to escape the forces that trap us in the three-dimensional surface that we normally think we live in. You can be sure, though, that moving ourselves a macroscopic distance into any extra dimensions, if they are out there, is impossible. If it were easy, then individual elementary particles would be observed doing it all the time, after particle collisions. Since we don’t observe this, we know it’s not easy, and so making anything human-sized move sideways out of our usual three-dimensional prison would require, yet again, absurd and unrealistic amounts of energy.
Oh, and I can’t resist mentioning (just to prove that all rabbit holes are secretly connected like wormholes) that in certain cases the two previous paragraphs can be related to each other. That, however, is another three stories.
Have a great week! And stay away from glowing doorways.