Photons are tiny carriers of energy that can behave like waves and particles, serving as the basis of light and playing a crucial role in our perception of the world. They are emitted, reflected, or absorbed by objects like computer screens or lamps, creating the images that we see.
Behaving like waves, photons have an amplitude and wavelength, with the wavelength determining the energy of the photon. Short waves have higher energy and appear purple, while long waves have lower energy and appear red. Our eyes can detect light in the range from 380 to 750 nanometers due to specialized retinal cells – cones.
Although invisible to the human eye, there is light such as infrared, discovered by William Gershelm in the 19th century, with a wavelength exceeding 750 nanometers. Ultraviolet, x-ray, and gamma rays have wavelengths less than 10 picometers, at the other end of the spectrum.
Humanity’s understanding of the cosmos is largely based on light. Stars, galaxies, and exoplanets emit or reflect light that travels through space to reach Earth. By studying these signals, scientists can determine the temperature, composition, and rotational speed of celestial bodies.
The temperature of a star influences the wavelength of light it emits, with hot stars emitting blue light and cooler stars emitting red light. Filters and spectrometers are used to analyze light, with filters excluding specific wavelengths and spectrometers breaking down light into separate wavelengths for detailed spectrum analysis.
Observing the red and blue shifts of light frequencies allows astronomers to measure the speed of objects in space. The expansion of the universe was deduced by astronomers in the early 20th century, determining the universe’s age to be 13.8 billion years.
Modern astronomy now incorporates new methods like the detection of neutrinos, cosmic rays, and gravitational waves to complement traditional light astronomy, forming multi-signal astronomy and expanding our understanding of the Universe.
Light remains the primary source of information about space, offering insights into the nature, composition, and dynamics of stars and galaxies. Each observation of the stars serves as a reminder that light has traveled through space and time to reach us, providing opportunities to enhance our knowledge of the Universe.