Astronomy’s Decades-Long Quest To Understand Cosmic Topology

A 2026 paper in Nature Astronomy suggests that cosmic topology could imply the existence of closed loops in the universe, which could theoretically allow for time travel if a starship traveled in a specific direction for a long enough time. The paper notes that such loops would be unshrinkable and could manifest as patterns in the cosmic microwave background (CMB). The CMB is the light that last interacted with matter, about 380,000 years after the Big Bang, and has been studied since the 1960s. However, it wasn’t until the early 2000s that enough sensitivity was achieved to detect these patterns. Jaffe and colleagues have created the COMPACT group, consisting of about twenty international scientists, to study cosmic topology through large-scale cosmological observations. The group aims to identify signatures of such topology by creating a three-dimensional map of the observable universe, which could provide crucial information about the universe's structure.

• "The COMPACT group is dedicated to studying cosmic topology through large-scale cosmological observations."
• "A true three-dimensional map of the observational cosmos would help identify cosmic topology beyond just studying anomalies on the surface of the CMB."
• "The existence of such 'identifications' means that two areas of the sky that seem far apart might be close together, indicating a possible closed loop topology."

The authors suggest that the detection of such patterns would be difficult due to the scale of the topology, which would be too large to observe. The largest structure in the universe is the cosmic web, a network of gas and dark matter stretching across billions of light years. The paper also notes that the evidence for cosmic topology may already be in existing data or could be collected in future observations. The bottom line is that understanding the universe's size is crucial, as if it is too large, we may not be able to detect it.

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