In "Contact," Jodie Foster travels through one. So does Matthew McConaughey in "Interstellar," Spock in the 2009 "Star Trek" film, and pretty much everybody in "Stargate." Wormholes are ridiculously popular in science fiction, but are they science fact? No one actually knows. There are powerful theories that predict them, but if they do exist, many scientific hurdles stand in the way to riding the wormhole express. That doesn't mean we can't imagine what it might be like!
Connect The Dots
Physicists Albert Einstein and Nathan Rosen first imagined the possibility of a wormhole as a way to avoid a messy detail in physics: the singularity. Singularities are points where the math reaches infinity, like a particle with all of its mass concentrated into an infinitely small point. In a 1935 paper, Einstein and Rosen argued that you could technically avoid a singularity by extending that point into a path that leads to a second location.
To illustrate, if you had a balloon with a dot on either side to each represent a singularity, Einstein and Rosen's solution would be to push them inward toward each other and connect them, forming a tube-shaped path from one side of the balloon to the other. This was dubbed the Einstein-Rosen Bridge — what most people know as a wormhole.
It wasn't until 1939 that physicists used Einstein's theory of relativity to come up with the idea of a black hole, which is essentially a great big singularity. That same math also predicts the existence of a "white hole," which is a theoretical black hole in reverse — where a black hole has a point where gravity and density reach infinity so that nothing that enters can leave, a white hole has the opposite point where nothing can enter. One popular concept of a wormhole connects a black hole to a white hole. The best part about a wormhole is that those two points could theoretically connect anything to anything, whether that's two ends of the solar system or two completely separate universes. That would certainly fix all of our problems with faster-than-light travel, since that's not just a problem in physics — it's an impossibility.
Unfortunately, wormholes aren't really stable on their own. They open and close so quickly that not even a subatomic particle can make it through. To fix that, you'd need to buttress the wormhole from the inside with exotic matter, which has negative energy density and negative pressure. Even if you could do that, there are still a lot of problems with traveling through a wormhole, not the least of which being that you'd actually have to enter a black hole, which scientists believe would spaghettify your body for eternity (or worse).
But say we live in a sci-fi universe, an alternate reality where physicists have fixed all of these problems and wormholes are an everyday travel method. What would that look like?
You'd begin by free-falling through the outer horizon of a black hole. Once you reached the event horizon, Sandrine Ceurstemont writes for New Scientist TV, you'd see "an infinitely energetic flash of light from the outside world containing an image of the entire history of the universe." Just your average Tuesday. As you entered the wormhole itself, things would look warped, kind of like an extreme fish-eye lens. The flow of space would turn around and instead of being pulled inward, you'd be pushed outward until you saw another flash of light, this time containing the entire future of the universe. After a third flash of light upon reaching the white hole's outer horizon, you'd reach your destination. Sure beats public transit.
To get a better understanding of everybody's favorite genius, check out the biography "Einstein: His Life and Universe" by Walter Isaacson. The audiobook is free with a trial of Audible.