Light, as we understand it, travels through the universe in the form of electromagnetic radiation. Electromagnetic radiation consists of oscillating electric and magnetic fields that propagate through space. It includes a broad spectrum of wavelengths, from radio waves with long wavelengths to gamma rays with very short wavelengths.
In the context of the age of the universe, 13.7 billion years, light emitted by distant objects has undergone significant changes due to the expansion of space. As the universe expands, the wavelengths of light traveling through space also stretch, a phenomenon known as cosmological redshift. This means that light that was initially emitted with a certain wavelength is observed with a longer wavelength by the time it reaches us.
For example, light from distant galaxies that was emitted in the ultraviolet or visible range of the electromagnetic spectrum might have been stretched to longer wavelengths, potentially falling into the infrared or even microwave range by the time it reaches us. This phenomenon is due to the expansion of the universe and is a key piece of evidence supporting the Big Bang theory.
It's important to note that the details of how light propagates through the universe and the effects of cosmic expansion are complex and depend on various factors, including the nature of dark energy and the overall geometry of the universe. Scientists continue to study and refine our understanding of these processes to better explain the behavior of light in the vast expanse of the cosmos.