The concept you’re referring to is known as “cosmic distance ladder” and involves a combination of techniques and observations to estimate distances to far-off objects in the universe. While it’s true that the age of the universe is estimated to be around 13 billion years, the light we observe from objects that are currently measured to be 46 billion light-years away is not from the time when the universe was only 13 billion years old.

To understand this, it’s essential to consider the expansion of the universe. The universe has been expanding since the Big Bang, causing space itself to stretch. As a result, light from distant objects also undergoes stretching, or “redshifting,” as it travels through expanding space. This phenomenon causes the wavelength of the light to increase, shifting it towards the red end of the electromagnetic spectrum.

Scientists use the concept of redshift to estimate the distance to faraway objects. By measuring the amount of redshift in the light received from these objects, they can estimate the expansion of the universe over time and calculate the distance to the objects.

However, it’s important to note that the 46 billion light-years you mentioned is not a measure of distance based on the current understanding of the universe. It is a measure of the comoving distance, which takes into account the expansion of space. The comoving distance is a theoretical construct that accounts for the expansion of the universe and is larger than the actual distance that light has traveled.

In summary, the detection of light from objects that are currently estimated to be 46 billion light-years away is made possible through the use of redshift measurements and our understanding of the expanding universe. The concept of comoving distance helps us describe these vast distances, but it doesn’t imply that these objects were 46 billion light-years away when the universe was only 13 billion years old.