This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: If some aspects of cosmic topology turn out to be true, the idea that starships might voyage across the cosmos for hundreds of thousands of light-years without ever returning to the same neck of spacetime could be problematic. That's because some aspects of cosmic topology (the global shape and connectivity of our cosmos) could dictate a closed-loop universe—at least on the largest scales.
That means that, in some instances, if a starship heads in one direction long enough, hypothetically, it could return to its starting point. "In some cases, there is an actual physical and straight path that can take you back to where you started, but not to when you started," Andrew Jaffe, professor of cosmology and astrophysics at Imperial College London, told me via email. "If it took you back to the original time and spatial point, you would have something called a 'closed timeline curve'—also known as a time machine," he says.
The current paradigm is that we live in a flat cosmos that is infinite in all directions. But global topology may ultimately invalidate part or all of that axiom. But topology is characterized by the possible existence and properties of nonshrinkable closed loops—if you could travel far enough in some direction along the loop, you would return to your starting point, note the authors of a 2026 paper in the journal Nature Astronomy.
The goal of astrophysicists like Jaffe is to identify the signatures of such topology via large-scale cosmological observations. Cosmic topology would imprint subtle signatures on the cosmic microwave background (CMB) and on the three-dimensional distribution of matter, potentially breaking homogeneity at the largest scales, the authors write. The CMB is the earliest cosmic light currently observable.
It represents the light that last interacted with matter some 380,000 years after the Big Bang. Cosmologists have been observing the CMB since the 1960s, but only since the early 2000s have they had enough sensitivity to detect the patterns that would enable them to see topology. "The modern era of cosmic topology started in the late 1990s when we realized we could use patterns in the CMB to look for topology," Jaffe, author of the 2025 book "The Random Universe: How Models and Probability Help Us Make Sense of the Cosmos," told me.
"There were great strides with data from the WMAP satellite in the mid-2000s and then with yet higher-quality data in the 2010s," he says. The data has not improved much since then. But in the last few years, Jaffe and colleagues have created a group called COMPACT (Collaboration for Observations, Models and Predictions of Anomalies and Cosmic Topology), now comprising about 20 international scientists dedicated to thinking about this topological problem.
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