THE MYSTERY OF TIME

I'll start today with who is Usha Vance, wife of J.D., the brand new Republican veep candidate.

• Met at Yale Law School.
• If the Trump-Vance ticket prevails on November 5, she will become the first Indian of parents from India, and Hindu, to serve as Second Lady.
• She was raised by  immigrant parents, a mother who is a biologist and provost of Sixth College, at the University of California, San Diego, and a father, who is an engineer.
• Usha received an undergraduate degree from Yale, and a Master of Philosophy at the University of Cambridge.
• Like J.D., she served in editorial positions at the Yale Law Journal while in law school.
• The couple earned their attorney degrees in 2013 and got married the following year.  They have three children.
• She clerked for Judge Kavanaugh in 2014/5 when he was on the U.S. Court of Appeals, then a year with Supreme Court Justice John Roberts in 2017/8.
• Became a trial lawyer in San Francisco and Washington, D.C.
• Was a Democrat in 2014, but is now a registered as a Republican.

About the topic of the day, simplistically, I've had no problem with the concept of time.  

• I know when I was born, to the minute.  Says so on my birth certificate.  I can thus calculate how many minutes I have lived.  I know what time it is by asking Alexa.

• 
  About AD140, Ptolemy subdivided the solar day into the today equivalent of hour, minutes and seconds.
• Around AD1000, Muslim scholars subdivided the mean solar day into 24 equinoctial hours, each of which was subdivided sexagesimally into 86,400 seconds per day.

• 
  It took until 1874 for the base unit of time to be this second.  But the inconvenient leap year had to be created.
• This is because the Earth's rotation period varied irregularly.
• So in 1952 the International Astronomical Union defined the second as a fraction of the sidereal year.
•  The Coordinated Universal Time (UTC) standard was instituted in 1960, based on atomic clocks.

• 
  Then there is that matter called a leap second, only introduced in 1972.  Since then, 27 leap seconds have been added to the Coordinated Universal Time, none from 1999 through 2004, but nine leap seconds from 1972 to 1979.  This is the adjustment that is occasionally applied to account for the slowdown in the Earth's rotation.  However, the Earth's rotation rate could well require a negative leap second before 2035.

• 
  In any case, the 27th General Conference on Weights and Measures in 2022 decided to abandon the leap second and just use atomic clocks.  Life on Planet Earth will be made less complicated, but the Universe is universal, while Earth's rotation decline continues, so astronomers will need to do an adjustment of a minute every hundred years....or one hour in 5,000 years.
• Not to worry about the Earth eventually stopping, for that will occur in around 4 billion years, and the Sun will have long expanded to make life here impossible.

You can measure time two ways.  Neither uses a standard clock that you see on a wall or around your wrist.  

• Dynamically.
• The old definition of a second was based on the rotation of Earth.
• Arbitrarily, as described above, a day was divided into 24 hours, an hour into 60 minutes, and a minute in 60 seconds.
• But, as indicated, the Earth does not rotate uniformly.  The planet loses about 30 seconds every 10,000 years because of factors such as tidal friction.  Thus the invention of the leap second.
• 
  Atomically, using atomic clocks.
• Initially relied on magnetic fields.
• Now use lasers.
• Cesium clocks are the standard.  

• 
  Cesium is a shiny metal element with blue spectral lines.
• Name comes from Caesius, Latin for sky blue.
• Discovered by Robert Bunsen and Gustav Kirchhoff in 1860.
• If you're confused, both caesium (international) and cesium (American) can be used.
• 
  Strontium clocks promise twice the accuracy.

Many modern atomic clocks use oscillations of strontium atoms rather than cesium to measure time; the most precise of these is accurate to within 1/15,000,000,000 of a second. This means that, even if it had been running since the dawn of time around 13.8 billion years ago, the clock still wouldn't have lost or gained a full second.

• 
  Experimental charged mercury atoms could reduce discrepancies to less than one second lost or gained in 400 million years.
• In the future, atomic clocks will be based on optical, rather than microwave atomic transitions.  Maybe a factor of 10,000 times better.  If you have an hour and 23 minutes to spare, watch this video featuring Nobel Laureate David Wineland.

However, after all that above, time is even more mysterious.  The difficulty enters when you look at this from a quantum point of view, when you need to link space and time, which common sense says, surely must be different.  But that is not the case.

• In the 17th century, Isaac Newton saw time as an arrow fired from a bow, traveling only ahead.

• 
  Not so, said Albert Einstein in 1905.
• In addition to length, width and height, he said time is the fourth dimension.
• He might have read H.G. Wells' The Time Machine, first published in 1895.
• 
  While the speed of light does not change, time was more like a river, always changing depending on the effects of gravity and space-time.

• 
  Time would speed up and slow down around certain cosmological bodies with different masses and velocities.
• In other words, one second on Earth was quite different elsewhere in the universe.

• 
  Einstein's theory was proven true only in 1971, when physicists J.C. Hafele and Richard Keating flew four cesium atomic clocks on planes going eastwards and then westwards.

• 
  In 2004, Stanford University and Lockheed Martin reinforced that determination with NASA's Gravity Probe B, using gyroscopes pointed the direction of a distant star, and showed that time an be stretched and contracted by gravity.

• 
  But Einstein and Newton would agree that time, indeed, only moves forward.  There is no physical evidence that anything in the universe can dodge time, move backwards, or jump ahead.  But no one today can yet prove that time only moves forward.

Remain confused?  Read the 2018 The Order of Time, by Carlo Rovelli.

Watch Brian Green of Columbia University try to explain the mystery of time in less than a minute.  I should tell you that he doesn't quite know.  Another video that goes on for 6 minutes by philosophers of science from New York University.  Or maybe you might prefer a more spiritual elocution, by Robert Ollison.  But this goes on for 44 minutes.

I yesterday warned you about these past two Prime Days.  Today, the last day of Amazon sales, I cite a Time magazine article showing the best deals.  Here is just one, for $1,998.  Normally:  $2,763.

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