The speed of light #physics #light #science #education

The speed of light, c, is just under 300,000 km/s in a vacuum. At this speed, you could circle Earth more than 7 times in a single second. Yet, even at this incredible speed, light takes 8 minutes to reach us from the Sun, over 4 years to reach us from the nearest star outside our solar system, and over 2.5 million years to reach us from our closest neighbouring galaxy, Andromeda. And yet, according to Einstein’s theory of special relativity, no object with mass can ever travel faster than the speed of light as this would require an infinite amount of energy, which is clearly not possible. This cosmic speed limit confines us to our local corner of the universe, rendering the prospect of exploring even a small fraction of our galaxy within a human lifetime unattainable for now. But why can’t objects with mass travel faster than the speed of light? Now, it turns out that c is more than just a cosmic speed limit – it’s the conversion factor between mass and energy in the most famous equation in physics E=mc^2. This equation is telling us that 1 kilogram of mass holds nearly 100,000 trillion joules of stored energy—that is over 1,000 times the energy released in the Hiroshima atomic bomb and enough energy to power a 100W light bulb for over 20 million years. However, unlocking this energy would require an equivalent amount of antimatter, which when it annihilates with matter releases its stored mass energy. But how do you produce enough antimatter? Well, that’s a story for another day.