Simply find the best possible online shopping Moments of Light deals
Shop Moments of Light products and compare prices and listings on popular online marketplaces.
Asked by: Alan Edgington, Ramsgate
It isn't. When it passes through some mediums, such as water, it slows down considerably. In the case of diamond, its speed is cut by over 50 per cent. But according to Einstein's Special Theory of Relativity, the speed of light in the vaccum of empty space is said to be the same for all observers, at just short of 300,000km/s.
This is undoubtedly weird, as every other speed is measured relative to something else. For example, a train can move at 150km/h relative to someone on a platform, but to the train's passengers its speed is pretty much zero. The speed of light is no ordinary speed, however: it's a universal constant that emerges from the laws of physics.
Specifically, it's the speed at which electromagnetic waves travel through the vacuum of space - and its value can be predicted by equations unifying our understanding of electricity and magnetism, as discovered over 150 years ago by the Scottish physicist and mathematician James Clerk Maxwell.
Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.
One rainy day you go to your home office to get some work done. Since the sun was hiding behind the gray clouds, you had no choice but to switch on the lights. As you did, nothing happened. You tried again and again, but the room stayed dim and gloomy. It wasn’t long before your mood began to match the overcast day.
If this happened to you, lighten up – you don’t need to revert to using candles and oil lamps. Chances are, your bulbs aren’t bright enough. If you’ve been wondering about the intensity of light and how to measure it, continue reading this article as we explain it in detail.The plants will release bubbles of oxygen - a product of photosynthesis - which can be counted.
A lamp with an LED bulb is set up at different distances from the plant in a beaker of water:
The bubbles produced over one minute periods are recorded.
To investigate the effect of light intensity on the rate of photosynthesis.