Light's Long Journey: Why It Doesn't Get Tired

Light is always on the move. It zooms around at a speed of 186, 000 miles per second. This speed is the same whether it's coming from a star or a flashlight. One evening, a telescope was set up in a backyard in San Diego. It was pointed at a galaxy very far from Earth. The galaxy is called the Pinwheel. It has about a trillion stars. The light from the Pinwheel galaxy had traveled for 25 million years to reach the telescope. That's a distance of about 150 quintillion miles. The person operating the telescope had a question. Does light get tired on such a long journey? This question led to an interesting discussion about light. Light is a type of electromagnetic radiation. It's made up of electric and magnetic waves. These waves travel through space-time. Light has no mass. This is important because mass limits how fast an object can travel. Since light has no mass, it can travel at the maximum speed in a vacuum. That speed is about 186, 000 miles per second. This speed is incredibly fast. In the time it takes to blink, a particle of light can travel around the Earth more than twice. Space is very big. The Sun is 93 million miles from Earth. It takes sunlight over eight minutes to reach us. So, the sunlight we see is eight minutes old. The nearest star to us, after the Sun, is Alpha Centauri. It's 26 trillion miles away. Its light takes over four years to reach us. This is why astronomers say it's four light-years away. Light can travel these huge distances without losing energy. This is because space is mostly empty. There's nothing in the way to slow it down. Light can lose energy if it hits something, like dust. But most of the time, it travels without any obstacles. This means it keeps its speed and energy. Another interesting concept is time dilation. This is when time moves at different speeds under different conditions. For example, an astronaut on the International Space Station experiences time dilation. Their watch ticks slightly slower than someone on Earth. This is because they are moving much faster. Light is connected to time. If you were traveling on a photon, a particle of light, time would stop for you. This is because you'd be moving at the speed of light. From your perspective, the journey would be infinitely fast and short. But from our perspective on Earth, the journey would take millions of years. This is because space gets squished for the photon. The distance between where it starts and where it ends gets shorter. So, the journey is much shorter for the photon. This is why light doesn't get tired on its long journey across the universe. It's all about how time and space work together.