# Staring Down the Fourth Dimension

Ari D'Arconte

While ghosts and ghouls may not be real, science can manipulate our world in even stranger and more terrifying ways. The world that we interact with is three dimensional: up-down, left-right, and front-back. However, Einstein’s equations have described time as a fourth dimension, which is connected to the three spatial directions by the concept of space-time. Since they are connected, it means that two objects experience a different amount of time based on their location and distance traveled. While this phenomenon has no measurable impact on objects on Earth, the vast size and age of space means that time dilation is measurable. A paper published this July by professors from the University of Sydney and Auckland, predicted that, based on the expansion of the universe, objects further away from Earth should appear to go slower than objects closer to Earth due to time dilation. The study measured quasars, which are massive astronomical objects that give off tons of energy, which makes them good to measure. By measuring wavelengths emitted from these quasars for over two decades, the researchers found unambiguous evidence of this form of time dilation, known as red-shift dependent time dilation.

Confirming time dilation opens numerous new possibilities to science. Einstein used time dilation as evidence that time travel is possible, since the speed one traveled could affect their perception of time, and thus someone traveling at speeds close to the speed of light would experience time much slower than people on Earth. The study also taught us more about the properties of quasars, which have been suggested to contain massive black holes and to be a step in the creation of galaxies. Overall, the existence of time dilation opens up a new understanding of what time and space really mean on a universal scale.

Lewis, G.F., Brewer, B.J. Detection of the cosmological time dilation of high-redshift quasars. *Nat Astron* (2023). https://doi.org/10.1038/s41550-023-02029-2