Featured Research

from universities, journals, and other organizations

Physicists Find More Precise Gravity Number -- And Weigh The Earth

Date:
May 1, 2000
Source:
University Of Washington
Summary:
It's a smaller world after all -- that is, if new measurements by University of Washington physicists turn out to be correct. Their new calculations for the Earth's mass came from work that could establish the most precise measurement ever achieved of Isaac Newton's gravitational constant.

It's a smaller world after all -- that is, if new measurements by University of Washington physicists turn out to be correct.

Their new calculations for the Earth's mass came from work that could establish the most precise measurement ever achieved of Isaac Newton's gravitational constant.

According to the figures by Jens Gundlach and Stephen Merkowitz, Earth weighs in at 5.972 sextillion (5,972 followed by 18 zeroes) metric tons. Recent textbooks list the weight as 5.98 sextillion metric tons. Either way, that's about 1 trillion metric tons for each person on Earth. Put another way, 1 trillion metric tons is thought to be the total weight of all plant and animal life on the Earth's surface.

Gundlach, a UW research associate physics professor, and Merkowitz, a postdoctoral researcher, report their findings May 1 at a meeting of the American Physical Society in Long Beach, Calif.

"Gravity is the most important large-scale interaction in the universe, there's no doubt about it," Gundlach said. "It is largely responsible for the fate of the universe. Yet it is relatively little understood."

Gundlach uses the relationship between the Earth and sun to illustrate the mighty role of gravity. If the gravitational force that holds the Earth in its orbit around the sun were to be replaced by a steel cable (assuming it could be made with no mass), the cable would have to be two-thirds the diameter of the Earth to do the same job as gravity.

Newton's gravitational constant tells how much gravitational force there is between two masses - the Earth and sun, for instance - separated by a known distance. The gravitational constant along with the speed of light and Planck's constant (a key value in quantum mechanics) are considered the three most fundamental and universal constants in nature. But while measurements of the other two constants have grown continually more precise through the years, the reverse has happened for the gravitational constant, called "Big G" in physics parlance.

In fact, new attempts to measure Big G in the 1990s brought results widely different from the previously accepted figure. That prompted the National Institute of Standards committee that establishes the accepted value to determine that there actually was 12 times more uncertainty about the figure last year than in 1987.

"That is a huge embarrassment for modern physics, where we think we know everything so well and other constants are defined to many, many digits," Gundlach said.

If accepted, the measurement by Gundlach and Merkowitz would reduce the uncertainty by nearly a factor of 100 from the currently accepted figure, making it far more precise than even the 1987 figure. Gundlach notes his numbers could change as additional data are analyzed in preparation for submitting the work for peer review.

To make their measurements, the researchers are using a device called a torsion balance that records nearly imperceptible accelerations from the gravitational effects of four 8.14-kilogram stainless steel balls on a 3- by 1.5-inch gold-coated Pyrex plate just 1.5 millimeters thick. The device, operating inside an old cyclotron hall in the UW nuclear physics laboratory, is similar in nature to one used 200 years ago to make the first Big G measurement. But it is computer controlled and contains numerous mechanical refinements that make the more precise measurement possible.

Gundlach acknowledged that the more precise calculation probably won't mean much to the average person.

"Just because we know the value of G won't make better cell phones," he said. "But it's something mankind should know because it's such a fundamental constant."


Story Source:

The above story is based on materials provided by University Of Washington. Note: Materials may be edited for content and length.


Cite This Page:

University Of Washington. "Physicists Find More Precise Gravity Number -- And Weigh The Earth." ScienceDaily. ScienceDaily, 1 May 2000. <www.sciencedaily.com/releases/2000/05/000501081530.htm>.
University Of Washington. (2000, May 1). Physicists Find More Precise Gravity Number -- And Weigh The Earth. ScienceDaily. Retrieved July 23, 2014 from www.sciencedaily.com/releases/2000/05/000501081530.htm
University Of Washington. "Physicists Find More Precise Gravity Number -- And Weigh The Earth." ScienceDaily. www.sciencedaily.com/releases/2000/05/000501081530.htm (accessed July 23, 2014).

Share This




More Matter & Energy News

Wednesday, July 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Robot Parking Valet Creates Stress-Free Travel

Robot Parking Valet Creates Stress-Free Travel

AP (July 23, 2014) 'Ray' the robotic parking valet at Dusseldorf Airport in Germany lets travelers to avoid the hassle of finding a parking spot before heading to the check-in desk. (July 23) Video provided by AP
Powered by NewsLook.com
Boeing Ups Outlook on 52% Profit Jump

Boeing Ups Outlook on 52% Profit Jump

Reuters - Business Video Online (July 23, 2014) Commercial aircraft deliveries rose seven percent at Boeing, prompting the aerospace company to boost full-year profit guidance- though quarterly revenues missed analyst estimates. Bobbi Rebell reports. Video provided by Reuters
Powered by NewsLook.com
Europe's Car Market on the Rebound?

Europe's Car Market on the Rebound?

Reuters - Business Video Online (July 23, 2014) Daimler kicks off a round of second-quarter earnings results from Europe's top carmakers with a healthy set of numbers - prompting hopes that stronger sales in Europe will counter weakness in emerging markets. Hayley Platt reports. Video provided by Reuters
Powered by NewsLook.com
9/11 Commission Members Warn of Terror "fatigue" Among American Public

9/11 Commission Members Warn of Terror "fatigue" Among American Public

Reuters - US Online Video (July 22, 2014) Ten years after releasing its initial report, members of the 9/11 Commission warn of the "waning sense of urgency" in combating terrorists attacks. Mana Rabiee reports. Video provided by Reuters
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