By Stratis Markou
As we all learn in IGCSE physics there is no definition for time, due to the fact that is one of the fundamental quantities in the universe (others include length and luminous intensity). What this means, essentially, is that these quantities cannot be “broken down” and explained in terms of other, simpler, quantities. So we can’t define time, or at least not accurately enough as we might want to. But what we can define is the unit of time, that is, seconds.
So we may think that the definition of a second is 1 ⁄ (24 × 60 × 60) of a day, or is it? It turns out that with today’s advanced technology we have redefined the second, as “9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom”[1]. It is easy to understand the order of magnitude of accuracy and precision these clocks offer, as by using them we can measure time intervals as small as one 9,192,631,770th of a second, given you are willing to spend the money to acquire one.
The usual stopwatch can measure time in 100ths of a second, a staggering 9 million times “slower” than the caesium clock, thus it is 9 million times less precise. The caesium clock is also mind-blowingly accurate. It gains or loses 1 second every 30 million years, compared to the extremely poor accuracy of 60 minutes lost or gained in a 65-euro digital stopwatch, for the same given time. But wait, there’s more: the caesium clock is NOT the most precise clock available to us currently.
The ytterbium clock’s, precision makes the caesium clock seem as primitive as a rock is, compared to Venus de Milo. The ytterbium clock is capable of achieving oscillations of up to “5.18*10^14 periods per second” [2], 56,349 times more precise than the caesium clock. But then why do we use caesium oscillations to define seconds? The answer to this lies in the fact that caesium clocks are more accurate than ytterbium clocks, meaning that the time interval between two oscillations of an ytterbium clock (out of the 518 trillion per second that occur in the ytterbium clock), is not as consistent as scientists would like. This means that although the ytterbium clock ticks faster than the caesium clock it gains or loses larger amounts of time per second.
Applications of the atomic clock include the GPS (Global Positioning System) which uses the general theory of relativity to achieve accurate calculations. The general theory of relativity shows us that gravity affects time. Where gravity is stronger, time passes more slowly compared to an area where gravity is weaker. Hence time passes faster in space (the GPS satellites are located there), compared to the earth’s surface, where the gravitational field is weaker due to the increased distance from the earth’s centre.
The GPS satellites need to account for that difference in time, and the caesium clock, aids them with its extreme precision and accuracy. In fact the atomic clocks are so precise, that they are able to indicate the time difference between your desk and the floor (as the top of the desk experiences a tiny difference in gravity, compared to the floor, due to the different distance from the centre of the earth).
Sources:
New Scientist (figures and numbers)
[http://www.newscientist.com/article/dn24092-most-precise-clock-to-watch-tiniest-ever-time-dilations.html#.UlFgDdJsxug]
Wikipedia (second definition)
Atomic… Clocks?
By Jason Palmer
Smartphone’s are hitting the market with more pixels than we have ever seen on a mobile phone. It seems as though our mobiles will soon replace the Digital SLR’s as they are becoming better at being the all-in-one devices that we seem to be looking for. The third biggest use of mobile phones has now become taking photos, and the companies that sell us them see the potential market and profit a good quality camera on our phones can be for them but also us.
To really answer the question we need to look at the advantages and disadvantages of both. Firstly, let’s look at our Smartphone’s:
Advantages of Smartphone’s:
Convenience: Every Smartphone released right now has a built in camera that does the job. Since our mobiles are in our pockets, they can easily be accessed, with no extra weight or bulk. The simple point-and-shoot features make it easy to take a photo at the click of a button, not only letting you take photos quickly, but also making it easier to take that great selfie you always wanted.
Sharing: Since most Smartphone’s are connected to the internet they also have a wide variety of photo sharing apps to choose from. Innovative apps such as ‘Snapchat’ let you take photos to send to your friends which then disappear after a certain amount of time adding the fun factor to using our phones camera. Other apps such as ‘Instagram’ have created massive communities of phone photographers and chances to share your great photos online. With the dawn of the Smartphone camera, sharing has only increased.
Cheap: It is indisputable that Smartphone’s with good quality cameras are cheaper than buying a proper camera. The Nokia Lumia 920 boasts a 8.7 mega pixel camera, with no loss of quality after having been zoomed in three times and only half the price of what a digital camera with the same potential would cost, while also having the most pixels on a mobile phone. No wonder more people are turning to Smartphone cameras!
Advantages of Digital Cameras:
Quality: Digital Cameras defiantly have better quality than your average Smartphone. The sharpness and clarity of a photo is very hard to mimic, especially with a good quality camera.
Hardware: Digital Cameras have more advanced hardware, also making them more reliable and long lasting. The hardware in cameras from a couple of years ago can still compete in quality with Smartphone’s. The digital camera provides hardware that would be hard to compete with, allowing it to include more features.
Features: Modern digital cameras tend to have many more features. The recently released Panasonic Lumix GM1 boasts 32 filters for photo-taking, a great ISO range and wi-fi features. The touch screen makes focusing easy and fast, providing much better quality images in bright and dark situations. Digital Cameras also make photos easier to edit, with programs specifically designed to edit them, such as Adobe Lightroom.
Overall it seems as though Smartphone’s are taking over; but are they really? In the last year, more Digital Cameras were sold compared to Smartphone’s which were aimed at casual photographers. In fact, Digital Cameras sold nearly a third more than the Smartphone’s aimed at the casual photographer. It seems as though the mobile phone market aiming to win over photographers is very niche and as was said by John Young from Nikon “A phone isn't a camera - it's a device that does multiple things”, therefore the mobile phone is not going to replace the Digital Camera any time soon. The fan base that exists for Digital Cameras will not be swayed by the petty features that are offered by phones, but the market for Smartphone’s with a good camera is definitely increasing.
Sources: http://www.engadget.com/2013/10/17/panasonic-gm1/http://www.brighthand.com/default.asp?newsID=19116&news=Smartphone+cameras+vs+digital+point-and-shoothttp://www.techhive.com/article/2029961/can-your-smartphone-really-replace-your-point-and-shoot-camera-.html