# Is the universe ~14 billion years old or that's the farthest photons which reached Earth?

I know that the universe:

1. It's around 13.772 billion years old
2. It expands

But it's not clear to me if this is not merely the age of the farthest known photons which reached Earth.

The age of the universe is calculated by fitting observed data to a cosmological model and calculating how long ago the scale factor (the "radius" of the universe) was zero. This is how you get the 13.772 billion year number - this comes from by using the $$\Lambda$$CDM model with the best parameters we know today. As data and theory gets more refined the number will be updated.