UC Berkley announced yesterday the results of the most precise test of Einstein’s Theory of General Relativity ever accomplished. Professor Holger Muller’s experiment confirms Einstein’s prediction that the passage of time is slowed down by gravity. Muller’s measurement matches Einstein’s prediction to better than 1 part in 100 million, which is the limit of the experiment’s precision and is 10,000 more accurate than any prior measurement.
To achieve this extraordinary accuracy, Muller cooled cesium atoms to a few millionth of a degree above absolute zero (-455oF) and “tossed” half of them up 4/1000ths of an inch. In the 1/3 of a second it took the elevated atoms to fall back down, they “aged” 20,000 trillionths of a trillionth of a second more than did their stationary siblings. Muller was able to measure that infinitesimal difference to an astonishing 0.000,1 of a trillionth of a trillionth of a second, using an atom interferometer
Einstein Theory of General Relativity is the foundation of our scientific understanding to the universe, the big bang, and black holes. It is also essential to GPS, the Global Positioning System that many of us have in our cars. If not corrected for the slowing of time due to gravity as Einstein explained, GPS readings would drift by 6 miles per day – if GPS got you home on Monday, you’d be in the next town on Tuesday, and possibly out to sea by Friday.
Find out more about gravity and time on my radio shows "Hey, Einstein, What Time Is It?" and "Gravity and the 3 R's" on my website: www.guidetothecosmos.com.
Muller feels he can do even better, and has already started building a more precise experiment.
Monday, February 22, 2010
Thursday, January 7, 2010
Worth $1 Million?
According to the Los Angeles Times, environmental proponents have stopped a solar energy project in the Mojave Desert that would eliminate 6 square miles of the habitat of two dozen threatened desert tortoises. Government officials propose the energy company purchase 19 square miles elsewhere and relocate the tortoises, at a cost that the company estimates to be $25 million. This amounts to $1 million per tortoise, or 6 times their weight in gold.
This portents a key challenge facing large-scale solar energy production. In a November 2009 article in Scientific American, Dr. Mark Jacobson and Dr. Mark Delucchi proposed a plan for supplying all the world’s energy from solar and wind power. They said solar collectors would need to cover 170,000 square miles, about 30,000 times more than the area contested in the tortoise dispute. Imagine how many other, frightfully expensive disputes lay ahead. The article estimates the cost of this plan at “on the order of 100 trillion dollars”, not including environmental mitigation costs or power transmission costs. Transmission costs will be very substantial since solar and wind plants will almost always be far from major urban areas.
We must, and we can, do better. More advanced technologies will deliver cheaper, cleaner, and more abundant energy that doesn’t imperil the environment, the tortoises, or our economy.
Monday, January 4, 2010
The New York Times reports that Russia’s space agency RKA plans to intercept and deflect a large asteroid heading our way. NASA estimates the 1000-foot-wide asteroid Apophis will pass within 20,000 miles of Earth in 2029 and will make a second pass at us in 2036. As Earth orbits the Sun at a speed of 66,000 miles per hour, this means Apophis is projected to miss Earth by 17 minutes, give or take. RKA plans to launch a space craft to push Apophis off course and away from Earth. Former Apollo astronaut Rusty Schweickert voiced concern that a miscalculation by RKA could send Apophis crashing into Earth. As this would be the first time anyone has attempted to deflected an asteroid, Schweickert suggests experimenting on a more distant asteroid that wouldn’t hit us in case RKA’s efforts aren’t A-OK.