system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do asphalt roads get lighter in colour as it ages?

A newly paved road is black, while an old one is light grey. Why does that happen?
gpt
Asphalt (bitumen) is actually the black gooey substance within asphalt concrete roads. The other component in asphalt concrete is aggregate which consists of small smashed up rocks.

When first paved, the asphalt concrete retains its black color from the asphalt. However, asphalt is softer than rock so it wears off the surface faster, exposing the harder gray aggregate. This turns the road from black to gray over time. Furthermore, weathering and exposure to the sun will also lighten the asphalt with time.