NASA's Gravity Probe B: Detecting Gyro Spin-up Forces of 10 Nano-Newtons

In summary, the Gravity Probe B team recently practiced a Low Temperature Bakeout procedure to remove remaining helium from the gyro housings. This also resulted in a small amount of spin-up helium gas being imparted to the gyros. The Gyro Suspension Systems were able to measure gas spin-up forces at a level of 10 nano-Newton, allowing for data interpretation at a much smaller scale than originally planned. This showcases the ability of science to push the boundaries of what we thought was possible.
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http://www1.msfc.nasa.gov/NEWSROOM/news/releases/2004/04-142.html

At the end of last week, the Gravity Probe B team practiced Low Temperature Bakeout (LTB), in which discs of sintered titanium (very tiny titanium balls, smaller than cake sprinkles) are "warmed up" a few Kelvin, thereby attracting helium molecules to them. This process will remove any remaining helium from the gyro housings after full gyro spin-up. Last week's practice LTB procedure had the added benefit of imparting a very small amount of spin-up helium gas to the gyros. Following the practice LTB, the SQUID gyro read-out data revealed that gyro #1, gyro #3, and gyro #4 were slowly spinning at 0.001, 0.002, and 0.010 Hz, respectively (1 Hz = 60 rpm). Amazingly, the Gyro Suspension Systems (GSS) were able to measure gas spin-up forces at the level of approximately 10 nano-Newton (10-8 N). This means that the GP-B science team is able to interpret data from gyro spin rates four to five orders of magnitude smaller than what was planned for the GP-B science experiment.
 
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Wow, that's really incredible! It's amazing that the Gravity Probe B team is able to measure such small spin-up forces. This experiment definitely shows that science can push the limits of what we thought was possible.
 

1. What is NASA's Gravity Probe B?

NASA's Gravity Probe B (GP-B) is a space-based experiment designed to test two predictions of Albert Einstein's theory of general relativity: the geodetic effect and frame-dragging. It was launched in 2004 and collected data until 2010.

2. How does GP-B detect gyro spin-up forces of 10 nano-newtons?

GP-B uses four ultra-precise gyroscopes mounted on a satellite to measure tiny changes in the orientation of their spin axes. These changes are caused by the Earth's gravitational field, which is distorted by the mass and rotation of the Earth. By comparing the gyroscopes' measurements, scientists can detect the effects of the Earth's gravity.

3. Why is it important to detect these tiny forces?

Measuring these tiny forces is important because they are directly related to the Earth's rotation and mass distribution, which are fundamental aspects of general relativity. By confirming Einstein's predictions, we can gain a better understanding of the nature of gravity and the structure of the universe.

4. How accurate are the measurements from GP-B?

The gyroscopes used in GP-B are the most accurate ever made, with a precision of 0.0001 arcseconds. This is equivalent to being able to measure the angle of a human hair from a distance of 10 miles. The data collected from GP-B has been confirmed to be accurate to within 1%.

5. What were the results of GP-B's measurements?

The results of GP-B's measurements confirmed both the geodetic effect and frame-dragging predictions of general relativity with a high degree of precision. This was a significant achievement in the field of physics and has helped to further our understanding of gravity and the laws of the universe.

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