Since Star Trek began sending its crews out to explore strange new worlds 60 years ago, the franchise has both imagined and inspired new concepts for travel across the vast distances of space. Among the most intriguing are “wormholes”: mysterious tunnels through spacetime that connect otherwise distant places.Star Trek always has a difficult balance to strike in making its portrayals both accessible and scientifically accurate. With wormholes, it generally favoured the former on their occasional appearances.On screen, one end of the wormhole will often appear as a swirling vortex or tunnel. In fact, computer simulations of these theoretical space shortcuts suggest that the opening would look more like soap bubbles or crystal balls, with their surfaces showing distorted and multiplied images of whatever lies on the other side.You could fly all around this opening and enter it from any direction, and rather than reaching the centre of the bubble, you would emerge from another similar bubble (the other end of the wormhole) somewhere totally different.Of course, the most important question for both Starfleet captains and theoretical physicists is: should you fly into a wormhole? The job of a starship captain may be to boldly go, but as a very risk-averse physicist, I’m not so sure.The first Star Trek wormhole“Wormhole distortion has overloaded the main power systems!” These words, spoken by Commander Willard Decker in Star Trek: The Motion Picture (1979), marked the first appearance of a wormhole in Star Trek. Video: SYL Ranch Darkroom. A warp drive malfunction leads to the creation of a distorted region of spacetime that sucks in the Starship Enterprise, leading to a breakdown of the ship’s systems and a potentially deadly collision with a random asteroid.It is a typically pioneering reference to what was, at the time, a niche research topic. John Wheeler, professor of gravitational physics at Princeton University, had first coined the term with Charles Misner in their 1957 paper Classical Physics as Geometry, which aimed to describe electric charges like electrons as the ends of tunnels in space.The first descriptions of traversable wormholes that satisfied Einstein’s equations of general relativity – configurations of matter that balance the spacetime curvature of the tunnel – were then independently published by H.G. Ellis and K. A. Bronnikov in 1973, although they didn’t use Wheeler’s moniker.Six years later, the first Star Trek wormhole wasn’t an accurate depiction of what scientists and science fiction enthusiasts now understand by the term. For one thing, the wormhole doesn’t appear to lead anywhere, and it dissipates once the crew regain control of the ship and drop out of warp speed.Nevertheless, as a researcher studying black holes and the early universe, I am rather fond of this scene – in part because it is actually possible to imagine warp drives (engines that bend spacetime to move the ship at faster-than-light speeds) distorting spacetime in this way.If you put exotic matter (one with a negative pressure) into a small region of spacetime, Einstein’s equations of general relativity tell us that region can expand exponentially fast. And if the space around it is not expanding in the same way, where can all that new space go?The answer, at least in this hypothetical scenario, is that it must balloon out into an entirely new universe, creating a wormhole in the process – a narrow passage that links the two regions.If you’re thinking this sounds implausible, Einstein’s theory of general relativity is actually perfectly ok with things being larger on the inside. Indeed, such scenarios may (speculatively) have arisen from rare fluctuations in the early universe.No slow-moStar Trek’s first depiction of a wormhole gets one aspect precisely wrong, though. In the film, the wormhole’s “temporal distortion” makes the crew move and speak in slow motion, struggling to fire the photon torpedoes that will save them from asteroid-impact obliteration.While the gravitational time dilation predicted by Einstein could be a feature of wormhole spacetimes, it would not be experienced as slow motion by those who fly in. For them, time would pass completely normally, with their watch ticking at one second per second.They might, however, emerge to find that their friends had aged far more than they had. But these friends wouldn’t have experienced time in fast-forward either. Both sides think time has passed normally, they just disagree about the amount.Again, this seems like it shouldn’t really be allowed – but the same effect is experienced by clocks on GPS satellites put into orbit around the Earth. When brought back to Earth again, they are found to have experienced more time than an equivalent clock left on the Earth’s surface, due to having spent time in a weaker gravitational field.Next Generation wormholesBy the late 1980s, Star Trek wormholes had achieved the ultimate sign of technological maturity – somebody was trying to sell one.This depiction, in the series Star Trek: The Next Generation (1987-94), more closely resembled the traversable wormhole framework co-developed by Kip Thorne in 1988. The US astrophysicist and future Nobel laureate had begun exploring the theoretical requirements for the existence of wormholes as portals connecting distant regions of space in the same universe. Video: Robin Sellex. Thorne showed that for a wormhole to be held open in a way that makes it traversable would require an exotic form of matter, violating certain energy conditions that physicists think ought to be respected at large scales.As the Next Generation crew find out, you don’t just want to buy any old traversable wormhole – you need it to be a stable one. The original Ellis-Bronnikov wormhole uses the right kind of exotic matter as scaffolding to hold it open. But even tiny disturbances will cause it to rapidly collapse – as has been demonstrated in many numerical simulations.A spinning version of the Ellis-Bronnikov wormhole appears potentially more robust, but its so-called “nonlinear stability” is yet to be established. Flying a starship through one of these would be a useful, if rather risky, test.The space between what is mathematically possible and physically realistic has always been a key part of the magic of Star Trek, inspiring several generations of scientists to explore strange new spacetimes. But if a soap-bubble wormhole ever appears in front of my spacecraft, I would always let Starfleet go first.Katy Clough receives funding from the Science and Technology Facilities Council (STFC) and the Simons Foundation. She will be speaking at the Star Trek Lates event at the Science Museum in London on Tuesday, September 8.