How does radiation from the Sun and distant stars reach Earth?

Radiation from the Sun and distant stars reaches Earth in the form of electromagnetic radiation. This energy travels through the vacuum of space as electromagnetic waves or as a flow of photons at the universal speed of light.1

Once this radiation reaches Earth, it interacts with the atmosphere and surface:

• Atmospheric Interaction: About 23 percent of incident solar radiation is absorbed by the atmosphere, particularly by water vapour, clouds, and ozone, which shields the surface from harmful ultraviolet light.2
• Surface Absorption: On average, 46 percent of the radiant energy reaching the top of the atmosphere is absorbed by Earth’s surface, though this varies based on factors like cloud cover and surface reflectivity.2
• Gravitational Effects: As this radiation travels toward Earth, it is subject to gravitational forces, which can cause a slight shift in frequency toward the blue end of the spectrum.3

The intensity of this radiation as it reaches Earth follows the inverse square law, meaning its strength varies inversely with the square of the distance from the source.4