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Time-warp: Why June 30 will be a bit longer

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Washington: Strictly speaking, a day lasts 86,400 seconds. On June 30, the day will officially be a bit longer than usual because an extra second or “leap” second will be added and NASA has an explanation for this.

“The Earth’s rotation is gradually slowing down a bit, so leap seconds are a way to account for that,” said Daniel MacMillan, NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

This is the case according to the time standard that people use in their daily lives – Coordinated Universal Time or UTC.

UTC is “atomic time” — the duration of one second is based on extremely predictable electromagnetic transitions in atoms of cesium.

These transitions are so reliable that the cesium clock is accurate to one second in 1,400,000 years.

However, the mean solar day — the average length of a day, based on how long it takes the Earth to rotate — is about 86,400.002 seconds long.

“That is because the Earth’s rotation is gradually slowing down a bit owing to a kind of braking force caused by the gravitational tug of war between the Earth, the Moon and the Sun,” the US space agency said in a statement.

Scientists estimate that the mean solar day has not been 86,400 seconds long since the year 1820 or so.

This difference of two milliseconds, or two thousandths of a second — far less than the blink of an eye — hardly seems noticeable at first.

But if this small discrepancy were repeated every day for an entire year, it would add up to almost a second.

Typically, a leap second is inserted either on June 30 or December 31.

Normally, the clock would move from 23:59:59 to 00:00:00 the next day. But with the leap second on June 30, UTC will move from 23:59:59 to 23:59:60, and then to 00:00:00 on July 1.

In practice, many systems are instead turned off for one second.

Previous leap seconds have created challenges for some computer systems and generated some calls to abandon them altogether.

“In the short term, leap seconds are not as predictable as everyone would like,” said Chopo Ma, geophysicist at Goddard.

“The modelling of the Earth predicts that more and more leap seconds will be called for in the long-term but we cannot say that one will be needed every year,” Ma said.

From 1972, when leap seconds were first implemented, through 1999, leap seconds were added at a rate averaging close to one per year.

Since then, leap seconds have become less frequent.

This June’s leap second will be only the fourth to be added since 2000.

(IANS)

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Parker Solar Probe of NASA Sends Back its First Images

The Parker Solar Probe's first close approach to the Sun will be in November

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NASA's Parker Solar Probe sends back first images. Flickr

Just over a month into its seven-year mission to touch the Sun, NASA Parker Solar Probe has beamed back the first-light data from each of its four instrument suites, the US space agency said.

On September 9, Wide-field Imager for Solar Probe’s (WISPR) — the only imager on the probe — door was opened, allowing the instrument to take the first images during its journey to the Sun.

WISPR with both its inner and outer telescope snapped a blue-toned, two-panel image of space with stars visible throughout.

While the Sun is not visible in the image, it showed Jupiter.

Launched on August 12, Parker Solar Probe, NASA historic small car-sized probe will journey steadily closer to the Sun, until it makes its closest approach at 3.8 million miles.

“All instruments returned data that not only serves for calibration, but also captures glimpses of what we expect them to measure near the Sun to solve the mysteries of the solar atmosphere, the corona,” said Nour Raouafi, the probe’s project scientist at the Johns Hopkins University in Laurel, Maryland.

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This is NASA’s Latest achievement. Pixabay

While these early data are not yet examples of the key science observations that the probe is expected to transmit in December, it shows that each of its four instrument suites are working well.

The probe also sent data back from its three other instruments on board: ISoIS, FIELDS and SWEAP which are all dedicated to unravelling the mysteries of the Sun.

ISoIS’s (pronounced “ee-sis” and includes the symbol for the Sun in its acronym) two Energetic Particle Instruments — EPI-Lo and EPI-Hi — cover a range of energies for these activity-driven particles.

EPI-Lo’s initial data shows background cosmic rays, particles that were energised and came rocketing into our solar system from elsewhere in the galaxy.

Data from EPI-Hi shows detections of both hydrogen and helium particles from its lower-energy telescopes.

The FIELDS’ four electric field antennas on the front of the probe observed the signatures of a solar flare, while the SWEAP’s (Solar Wind Electrons Alphas and Protons), three instruments caught glimpses of the solar wind.

NASA
Launched on August 12, Parker Solar Probe, NASA’s historic small car-sized probe will journey steadily closer to the Sun, until it makes its closest approach at 3.8 million miles. Pixabay

The Parker Solar Probe’s first close approach to the Sun will be in November.

Over the next two months, it will fly towards Venus, performing its first Venus gravity assist in early October.

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Throughout its mission, the probe will make six more Venus flybys and 24 total passes by the Sun.

The probe is named after Eugene Parker, a solar physicist, who in 1958 first predicted the existence of the solar wind, a stream of charged particles and magnetic fields that flow continuously from the Sun. (IANS)

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