When we talk about ‘light’, we are actually referring to all wavelengths across the electromagnetic spectrum, which travels at a speed of about 300 thousand kilometers (about 186,400 miles) per second.
Light travels so fast that in our daily lives, light appears instantaneously. Even at these breakneck speeds, it would still take time to travel anywhere across the cosmos.
When you look at the Moon, you really see it as it was 1.3 seconds ago. It’s just a little peek into the past, but it’s still the past. It’s the same with sunlight, except that photons (particles of light) emitted from the Sun’s surface travel for more than eight minutes before they finally reach Earth.
Our galaxy, the Milky Way, spans 100,000 light years. The beautiful newborn stars seen in JWST’s Carina Nebula image are 7,500 light-years away.
This nebula as described is from about 2,000 years earlier than when the first writings are thought to have been found in ancient Mesopotamia. Every time we look away from Earth, we look back at the past as before. This is a superpower for astronomers because we can use light, as it is observed all the time, to try to solve the mysteries of the universe.
–
.jpg?resize=150%2C150&ssl=1)
