The range at which we can see and receive visible light, radio waves, or other forms of electromagnetic radiation depends on various factors such as the intensity of the radiation, the sensitivity of our detectors, and the presence of any intervening objects or atmospheric effects. Here are some approximate distances for different types of electromagnetic radiation:
Visible Light: Visible light can travel through space without significant attenuation, meaning there is no specific distance limit for detecting visible light. However, the intensity of light diminishes with distance, and the sensitivity of our detectors becomes a limiting factor. For example, under ideal conditions, the human eye can detect the light from a candle flame several kilometers away on a dark night. With telescopes, we can detect and observe objects billions of light-years away, such as galaxies.
Radio Waves: Radio waves have longer wavelengths and lower frequencies compared to visible light. They can travel long distances and pass through various obstacles, including the Earth's atmosphere. The range for receiving radio waves depends on factors like transmitter power, antenna size, and frequency. With powerful transmitters and sensitive receivers, we can detect radio waves from sources located billions of light-years away, such as distant galaxies.
Other Forms of Electromagnetic Radiation: The range for receiving other forms of electromagnetic radiation, such as microwaves, infrared, ultraviolet, X-rays, and gamma rays, varies depending on the specific type of radiation and the technology used for detection. Different forms of radiation have different levels of attenuation and interaction with matter. For example, X-rays and gamma rays can be absorbed by the Earth's atmosphere and require space-based observatories to detect sources beyond our planet.
It's important to note that the ability to detect and receive electromagnetic radiation also depends on the sensitivity and capabilities of our instruments and technology. Advances in technology continually push the boundaries of our observational capabilities, allowing us to detect and study electromagnetic radiation from increasingly distant sources in the universe.