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Uncovering the Universe's Hidden light

Seeing Beyond: Uncovering the Universe’s Hidden Light
~ Vihaan Bhalotia
11/10/25


When most people think of light, they think of the visible spectrum, the rainbows we see after a light shower or oil slicks. But in reality, a large majority of light is actually invisible. Electromagnetic light radiation is all around us. It travels beyond what our eyes can comprehend.

What is Invisible Light?


Invisible light is wavelengths in the electromagnetic spectrum too short or too long to be detected by the human eye. Wavelength visible light ranges from 400nm (Violet) to 700nm (Red). Our eyes are tuned to this section of the spectrum. Invisible light on the other hand, is any wavelength that is either larger or shorter than that of visible light. Few Examples are ultraviolet light, infrared light and Gamma rays.

Discovery of Invisible Light


Before the 1800's the word “light”, apart from being a verb or adjective, meant only the visible spectrum, the light visible to our eyes. But then in the year 1800, an english astronomer named William Herschel made one of the most significant discoveries of the century, by accident.

Herschel was exploring the relation between light and temperature. He started by placing a prism in front of a source of white light. To prove his theory that different colors of light had different temperatures, he placed multiple thermometers in front of the different colors of visible light. As a control, he placed a thermometer outside the spectrum produced on the screen, adjacent to the red expecting to read room temperature. Unexpectedly the control showed a temperature higher even than the visible red light.
From this experiment Herschel concluded that there was more, beyond what our eyes can see. He had just discovered Invisible Light.

How does it interacts with Matter?
Invisible light interacts with matter through absorption, reflection, transmission and scattering.
When the matter absorbs invisible light, depending on the material, it can react with the electrons present to sometimes emit new light like photoluminescent light. When a reflective surface is placed in front of the light, it gets reflected. On the other hand when transparent matter is kept in front of it, it passes through it.



Cosmic Significance of Invisible Light
After the discovery of invisible light, it took almost 130 years for astrophysicists to make the connection between these light rays and their ability to enable us to see the universe from another ‘invisible’ lens. In the year 1933, an american radio engineer Karl Jansky was tasked by Bell Telephone Laboratories to identify sources of static interfering with overseas radio communications. Using a Large rotating antenna, he detected a hiss that peaked every 24 hours.

Jansky concluded that the signal was coming from a fixed point in space and identified the source as the center of our galaxy hidden in the constellation now known as Sagittarius. This accidental discovery marked the beginning of radio astronomy.




Another instance is Infrared Space Exploration which uses infrared space telescopes to locate and see objects by detecting their heat and allowing us to see them through cosmic dust and visible light sources.

Astronomers have used invisible light astronomy and telescopes to make multiple discoveries of great significance. Infrared astronomy has been used to discover Protostars, distant galaxies and a small part of the early universe. Microwave astronomy was used for the discovery of Cosmic Microwave Radiation. Radio astronomy allowed astrophysicists to see Pulsars and Quasars for the first time and map the spiral structure of our own galaxy, the milky way. X-ray and Gamma Ray astronomy helped discover Black holes and Neutron stars, distant galaxy clusters and supernova remnants.




Conclusion
(Black hole image captured by a radio telescope)

Invisible light has become a big part of our everyday life. It is used in appliances ranging from Microwave heaters in our kitchen to half a kilometer wide radio telescopes in the mountains of China. These Electromagnetic Light Waves have been playing a significant role in technological

advancements and discoveries since the 19th century and will continue to do so for hundreds of years. They helped us discover such bodies in space which our minds could not even imagine before discovering them, like black holes.

This invisible light had revealed an entire new spectrum of possibilities and completely transformed our understanding of the universe.

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