This is our first KS3 Science quiz regarding speed. The fastest possible speed at which energy or information can travel is the speed of light. Light travels incredibly fast. A ray of light can travel 300,000 km in one second! That means it can cover the distance from the Moon to Earth in 1 second and the 150 million km from the Sun to the Earth in just over 8 minutes.
It means that if the Sun suddenly stopped shining, we wouldn't know until a little over 8 minutes later. Despite this incredible speed, light from the most distant objects in the Universe has taken a mind-boggling 13.4 billion years to reach us. It is impossible to see the Universe as it is today, you always see it as it was in the past.
In order to calculate speed, you need to know the distance travelled and the time it takes.
The full scientific definition of speed is the distance travelled in unit time so it is therefore calculated by dividing distance by time taken to cover that distance. In SI units, the distance is measured in metres and the time in seconds. This means that the units of speed are metres per second which can be abbreviated to m/s. You will see speeds given in many other units too like kilometres per hour (which can be abbreviated to km/h or, if you are not writing in a scientific context - kph) and on British cars miles per hour (usually abbreviated to mph).