The idea that scientists can detect light coming from objects that are more than 13 billion light-years away may seem contradictory at first, given the age of the universe. However, this phenomenon is a result of the expansion of space itself.
The expansion of the universe causes distant galaxies to move away from us, and as a result, the light they emit gets stretched or "redshifted" as it travels through expanding space. This means that the wavelength of the light increases, shifting it towards the red end of the electromagnetic spectrum. The greater the distance, the more pronounced the redshift.
The concept of redshift is crucial in understanding the observed light from distant objects. It allows scientists to determine the distance to these objects by measuring the amount of redshift. The redshift of light is directly related to the expansion of the universe and can be used as a cosmic "ruler" to estimate the distance.
When scientists say they detect light from objects that are, for example, 46 billion light-years away, they are referring to the "proper distance" between us and those objects at the time the light was emitted. Due to the expansion of space, the actual distance between us and those objects has increased since the light started its journey. Therefore, the light has traveled for about 13 billion years, but the current distance to those objects is now significantly larger.
It's important to note that the concept of redshift and the expansion of the universe are fundamental principles in modern cosmology, supported by extensive observational evidence and theoretical models.