HighIQCommunity.Com

# Scientist Shows There Are Two Ways to Measure a Day on Earth – We Use The Longer One

by | Sep 20, 2020 | New, News

Don’t wait. The time will never be just right.

—

(dem10/E+/Getty Images) SPACE Scientist Shows There Are Two Ways to Measure a Day on Earth – We Use The Longer One MORGAN MCFALL-JOHNSEN, BUSINESS INSIDER 20 SEPTEMBER 2020

How long does it take Earth to complete a 360-degree rotation? Not quite 24 hours, it turns out – it's precisely 23 hours and 56 minutes.

But because Earth is constantly moving along its orbit around the Sun, a different point on the planet faces the Sun directly at the end of that 360-degree spin.

For the Sun to reach the exact same position in the sky, Earth has to rotate 1 degree further.

That's how humans have chosen to measure days: not by the Earth's exact rotation, but the position of the Sun in the sky.

Technically, these are two different types of day. A day measured by the completion of a 360-degree rotation is called the sidereal day.

A day based on the position of the Sun, however, is a solar day. The latter is four minutes longer than the former, making the even 24 hours we're used to.

"It's only because we move around the Sun in an orbit that the solar day takes 24 hours," James O'Donoghue, a planetary scientist at the Japanese space agency (JAXA), told Business Insider.

"If we didn't orbit the Sun, both days would be the same."

He made the below animation to show how this works.

Because we go by solar days in our calendars, we count 365 days in a year. But Earth actually completes a full rotation (a sidereal day) 366 times per year.

O'Donoghue describes the difference between these two types of day as a matter of choosing which background object we use as a basis of comparison for Earth's rotation. A full rotation relative to the position of the Sun is a solar day. A full rotation relative to all the other stars we see is a sidereal day.

If we used the sidereal day instead, "the Sun would rise about four minutes earlier every day," O'Donoghue said. "After six months of doing this, the Sun would be rising 12 hours earlier."

He added: "We've decided to tie our daily rhythm to the Sun, not the stars. In fact, the stars rise about four minutes earlier every day because of our choice."

• The EU wants to give itself the power to kick US tech giants out of Europe
• Doing these 3 things will make you an expert on any topic, according to a Google mentor
• This Green Beret had his leg shot off on a 'cursed' mission, but that didn't stop him from becoming an elite sniper
• Volkswagen has unveiled its Caddy California camper van with a bed and kitchen — see inside
• I've been using Apple's new iOS 14 for a few days and while there's useful updates to Messages, the App Library is disappointing

View Original Article

Site Visitors

## twoc, n.

twoc, n. The offence of taking a car without the owner's consent, esp. for the purpose of joy-riding

## NFTs and AI Are Unsettling the Very Concept of History

As an archivist, I’m excited about what disruptive innovations like non-fungible tokens (NFTs) and artificial intelligence may mean for archives. But I’m also worried. These developments pose existential threats to our field, and by extension, to the..

## Ancient Bear DNA Sequenced From Old Cave Dirt in Historic First For Science

Chiquihuite Cave. (Devlin A. Gandy) NATURE Ancient Bear DNA Sequenced From Old Cave Dirt in Historic First For Science MICHELLE STARR 20 APRIL 2021 The dirt scattered across the floor of an ancient, remote cave in Mexico has yielded a new source of v..

## Brave Volunteers Are Being Deliberately Reinfected With COVID-19 For Science

Dying cell (blue) from patient, heavily infected by SARS-CoV-2. (NIAID) HEALTH Brave Volunteers Are Being Deliberately Reinfected With COVID-19 For Science AFP 20 APRIL 2021 The University of Oxford said Monday it has launched a trial in which people..

## Site Statistics

302 registered users
4,295,569 words