Featured Research

from universities, journals, and other organizations

When Atoms Collide: Scientists Propose New Way To Determine Accurate Time Faster

Date:
June 5, 2007
Source:
National Physical Laboratory
Summary:
Scientists have proposed a new faster way to determine accurate time. Very precise time keeps the Internet and e-mail functioning, ensures television broadcasts arrive at our TVs and is integral to a network of global navigation satellites (such as the Global Positioning System) used for precision mapping and surveying, environmental monitoring and personal location-based services. But time can only be useful if it is the same for everyone.

Krzysztof Szymaniec and Witold Chalupozak with NPL's atomic fountain.
Credit: Image courtesy of National Physical Laboratory

Scientists at the UK's National Physical Laboratory (NPL) have proposed a new way to determine accurate time faster.

Very precise time keeps the Internet and e-mail functioning, ensures television broadcasts arrive at our TVs and is integral to a network of global navigation satellites (such as the Global Positioning System) used for precision mapping and surveying, environmental monitoring and personal location-based services. But time can only be useful if it is the same for everyone.

And that requires a single source against which we can all check our clocks. The caesium fountain that NPL operates is one of only a handful of highly precise measurement devices around the world that inform the global primary time standard -- the definition of accurate time. NPL's atomic fountain measures the accuracy of existing time standards and feedback readings to inform any adjustments to Coordinated Universal Time -- the basis for the worldwide system of timekeeping.

NPL's instruments do not simply measure time. They measure the absorption of electromagnetic waves by caesium atoms and detect the resultant changes in the internal state of those atoms. The absorption peaks at a specific electromagnetic frequency. They can then lock this frequency and use the number of oscillations of that frequency, during a given period of time, to define a second, like the ticks of a conventional clock. One second, for example, corresponds to just over nine billion oscillations of an electromagnetic signal locked to the peak change in caesium atoms.

But an atomic clock is never perfect. One of the challenges when identifying the accurate frequency reference is that it tends to fluctuate very slightly and its average value is only known within a certain error range. In atomic fountains, these tiny errors are largely due to atoms colliding with each other inside the fountain. This is known as a collisional frequency shift. There have been several theories about what affects the collision shift and how to compensate for it but existing methods can take days or even weeks.

The team at NPL has discovered a potential new approach, reducing the time it takes to confirm the accuracy of a frequency reading to a matter of hours -- ten times faster than it can currently be done. It is based around the state of the atoms during their flight in the fountain. They can be in one of two states -- upper or lower, or in a combination of the two. The NPL team in collaboration with NIST (USA) and PTB (Germany) discovered that the effect the collisions have on the frequency signal depends on which state the atoms are most in.

Upper results in a negative shift, lower in a positive shift. This suggests the existence of a split between upper and lower state atoms that cancels the shift out and results in no affect to the frequency signal. Operating a caesium fountain at this 'zero-shift' point is an attractive proposition as it removes the need to compensate for collision shifts and accelerates the process of confirming the accuracy of frequency standards. This means laboratories providing the primary time standard can feed back more readings in any given period of time, increasing the accuracy of recommended adjustments to UTC, potentially improving the overall accuracy of the world's time.


Story Source:

The above story is based on materials provided by National Physical Laboratory. Note: Materials may be edited for content and length.


Cite This Page:

National Physical Laboratory. "When Atoms Collide: Scientists Propose New Way To Determine Accurate Time Faster." ScienceDaily. ScienceDaily, 5 June 2007. <www.sciencedaily.com/releases/2007/06/070604124003.htm>.
National Physical Laboratory. (2007, June 5). When Atoms Collide: Scientists Propose New Way To Determine Accurate Time Faster. ScienceDaily. Retrieved September 20, 2014 from www.sciencedaily.com/releases/2007/06/070604124003.htm
National Physical Laboratory. "When Atoms Collide: Scientists Propose New Way To Determine Accurate Time Faster." ScienceDaily. www.sciencedaily.com/releases/2007/06/070604124003.htm (accessed September 20, 2014).

Share This



More Matter & Energy News

Saturday, September 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

What This MIT Sensor Could Mean For The Future Of Robotics

What This MIT Sensor Could Mean For The Future Of Robotics

Newsy (Sep. 20, 2014) MIT researchers developed a light-based sensor that gives robots 100 times the sensitivity of a human finger, allowing for "unprecedented dexterity." Video provided by Newsy
Powered by NewsLook.com
MIT BioSuit A New Take On Traditional Spacesuits

MIT BioSuit A New Take On Traditional Spacesuits

Newsy (Sep. 19, 2014) The MIT BioSuit could be an alternative to big, bulky traditional spacesuits, but the concept needs some work. Video provided by Newsy
Powered by NewsLook.com
New Music With Recycled Instruments at Colombia Fest

New Music With Recycled Instruments at Colombia Fest

AFP (Sep. 19, 2014) Jars, bottles, caps and even a pizza box, recovered from the trash, were the elements used by four musical groups at the "RSFEST2014 Sonorities Recycling Festival", in Colombian city of Cali. Duration: 00:49 Video provided by AFP
Powered by NewsLook.com
Virtual Reality Headsets Unveiled at Tokyo Game Show

Virtual Reality Headsets Unveiled at Tokyo Game Show

AFP (Sep. 18, 2014) Several companies unveiled virtual reality headsets at the Tokyo Game Show, Asia's largest digital entertainment exhibition. Duration: 00:48 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins