Photos taken by the astronaut reveal how cities change their nights

The basis of the change is the transformation of the technology used in street lighting.

Until the early 21st century, most cities were lit by sodium vapor lamps, which gave off a characteristic yellow-orange light.

However, with the widespread use of LED technology, cities began to replace old street lights with LEDs that last longer and consume less energy.

Pettit stated that this transformation significantly changed the appearance of cities from space, and said that yellow-orange lights were replaced by LEDs of different colors around the world.

One of the cities where the change was seen most clearly was Miami.

Comparing the two photographs taken by Pettit in 2012 and 2024, it is seen that the yellow-dominated night view of the city has largely turned into white light.

The astronaut stated that in the past, the intense yellow light of sodium lamps suppressed other colors, and with the widespread use of LEDs, the different colors of Miami can now be distinguished from orbit.

A similar transformation took place in Las Vegas. Images taken in 2012 and 2025 revealed a significant change in the night view of the city.

Pettit stated that Las Vegas continues its flashy appearance with new LED light sources, and the giant Sphere structure can be seen as a large purple dot in the images.

Similar changes were observed in Chicago, Sao Paulo and Seoul.

The proliferation of LEDs doesn't mean nights are getting brighter everywhere.

Between 2014 and 2022, Britain became 22 percent darker at night, according to NASA research. In France, this rate reached 33 percent.

It is stated that one of the important reasons for this change is the transition to energy-saving LED technology.