“This process is like a cosmic CT scan, where we can look through different slices of cosmic history and track how matter clumped together at different epochs,” team co-leader Mathew Madhavacheril of the University of Pennsylvania said in a statement. “It gives us a direct look into how the gravitational influence of matter changed over billions of years.”

In order for the team to build this so-called CT scan of the universe, they needed to turn to light that has existed almost as long as the cosmos itself.

With such ancient light, it’s possible to track the changes the universe underwent as gravity reshaped it over around 13.8 billion years.