One of our readers requested an article about time keeping devices, and it’s a great time for the topic. Scientists set a new record in clock precision early this year with an atomic clock that ‘ticks’ 430 trillion times in a single second.
Most wristwatches and wall clocks today use a quartz crystal to keep time. The cool thing about quartz is that it bends when you give it an electric charge. The tiny quartz in a clock is trimmed with a laser so that, when you give it electricity, it vibrates 32 768 times a second.
It’s not just a random number. If you halve 32 768 and then take the answer and halve it again, and again, and again, eventually the answer is one. Clocks use a chain of divide-by-two counters to turn the quick quartz vibrations into a steady second.
As rapidly as quartz vibrates in a watch, it’s nothing compared to an atomic clock. Our definition of a second is now measured using the light from caesium atoms, which has a frequency of exactly 9 192 631 770 cycles each second.
Atomic clocks are very precise and are put in satellites that orbit Earth as part of the global positioning system (GPS). Power stations, mobile phones and wireless networks can use the clocks in GPS satellites to keep everything synchronised – working at the same time. The clock on your computer may well get the right time by connecting through the internet with a computer server that uses an atomic clock as a reference.
Scientists from the USA set a new record in precision and stability early this year with an experimental strontium clock. Led by a physicist from the National Institute of Standards and Technology, the clock contains a few thousand atoms of strontium. The strontium atoms were arranged in a column of pancake shapes, held in place using lasers. When bathed in red laser light, they ‘ticked’ 430 trillion times a second.
The experimental strontium clock was so precise that scientists say it wouldn’t lose or gain a second in about five billion years. That’s longer than the age of the Earth, estimated at four and a half billion years!
This experimental atomic clock uses strontium atoms and laser light. The image is made from many photos taken with long exposure times and other techniques to make the lasers more visible. Image: Ye group and Baxley/JILA
Quiz questions
How many milligrams are in a gram?
Is the cerebrum the largest part of the human brain, or the smallest?
Which of these has the longest wavelength? Is it a) UV, b) visible light or c) microwaves?
Which species of penguin is the smallest?
Which continent are piranha fish native to?
Robots!
ABC Splash presents Robots!, a live, web-streamed event for Australian students at 2 pm AEST on Wednesday 10 September.
The free 45-minute event features robot experts from Robot Workshop and Robogals, a Robocop Junior and Iain Collings, CSIRO's head of robotics. Plus there will be a live robotics demonstration by the NSW Police Rescue and Bomb Disposal Unit.
Turn the cup upside down so that the base is facing you. Push the end of the slinky into the base of the cup so it makes a small hole..
Insert about 3 cm of the slinky through the hole in the cup.
Turn the cup over so that the base is facing downwards. Hold the slinky so it is coiled under the base of the cup.
Drop the slinky and listen to that sweet slinky sound!
You will need
Metal slinky
Disposable cup
Sticky tape
Scissors
What to do
Hold one end of the slinky and let it fall towards the ground. Can you hear anything? You might be able to hear a faint noise, so let’s make it louder!
Turn the cup upside down so that the base is facing you.
Push the end of the slinky into the base of the cup. It should make a small hole. If you can’t use the slinky to make a hole in the cup, carefully use scissors to make a small hole. If you use scissors, be careful not to cut yourself. You might want to ask for an adult to help.
Insert about 3 cm of the slinky through the hole in the cup.
Turn the cup over so that the base is facing downwards. Hold the slinky so it is coiled under the base of the cup.
Drop the slinky. It should stretch towards the ground without falling out of the cup. If it falls off the base of the cup, stick it in place using sticky tape.
Listen to that sweet slinky sound!
What’s happening?
Some people say the slinky cup makes a laser sound effect. Others say it's like a blaster from Star Wars. What do you think it sounds like? What you’re hearing with the cup and slinky is actually the sound that a slinky makes all the time. The sound is usually just too quiet for you to hear.
Slinkies make sound because they vibrate when they stretch out. When they vibrate, they make the air around them vibrate, and that makes the drum in our ears vibrate. The vibrations in our ear are picked up by some of the smallest bones in our body, the hammer, anvil and stirrup. The sound moves into the cochlea where it’s picked up by nerves. The information is then sent to the brain where we interpret it.
The cup makes it possible to hear the sound of a slinky. The air in the cup, and the cup itself, all vibrate with the vibrations from the slinky. The vibrations build up, and the sound gets louder. This is called amplification.
Applications
String instruments such as guitars produce sound from vibrating strings. The strings of a guitar vibrate when you pluck or strum them. In an acoustic guitar, the vibrations are amplified by the soundboard on the front, and the air inside its hollow body. That’s why the music from an acoustic guitar is so much louder than the sound from just plucking a string.
Electric guitars work differently. The vibrations from plucking the string are converted into electrical signals, which are amplified and transmitted to a speaker to produce sound.
There are lots of different types of string instruments. Violins, harps, banjos, sitars and ukuleles all use vibrating strings to make music. With brass instruments, such as tubas and trumpets, it’s actually the musician's lips that vibrate.
How fast can humans run? Usain Bolt is the fastest person recorded in a race, but fossilised footprints in Australia of an Indigenous person running suggests people could go even faster! Want to find out more? Watch the video below from A Week in Science by the RiAus.
Quiz answers
There are 1000 milligrams in a gram.
The cerebrum is the largest part of the human brain.
c) Microwaves have the longest wavelength.
Little penguins, also known as blue penguins, fairy penguins or kororā are the smallest species of penguin.
Piranha fish are native to South America, and are famous for their sharp teeth.
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