Creation

Nope. Yup. Nope.

Easy. Atomic clocks are not in sync with the rotation of the Earth. They are in sync with one of various energy level transitions in particular atoms, and are in no way connected to the rate of rotation of the Earth.Leap seconds are added to bring the Earth-rotation-based time back in sync with the atomic-clock-based time. If they weren't added the two would get more and more out of sync as time passes. Which would be inconvenient. But there's no physical requirement to keep the two in sync. We choose to keep them close to sync to simplify various conversions.Edited by JonF, : No reason given.

It's the other way round. The Earth-rotation clock is adjusted to match the atomic clock. But the two clocks do not have to match, it's just more convenient for them to be close to matching. Leap seconds are added so the atomic clock and earth are in sync, but not because of any change in the Earth's rotation rate. As of now that's too small to be important. They are added because atomic-clock time does not tick at the same rate as Earth-rotation time.

The scientific answer is "we're not sure but we have some possible hypotheses and are making significant progress in finding out".

Doesn't follow from your previous statements, and false.Time is based on whatever measure is convenient and sufficiently accurate.. Earth's rotation varies too much to be sufficiently accurate, not to mention the problem that Earth's rotation is difficult to impossible to measure under almost all circumstances. All the instruments we use for measuring time are calibrated through a series of other devices and ultimately by an atomic clock. Atomic clock time is close to Earth rotation time, but not exactly equal.In the US, the official definition of time is the time kept by the NIST-F2 atomic clock. NIST Launches a New U.S. Time Standard: NIST-F2 Atomic Clock | NIST. Other countries use other atomic clocks. The various clocks are compared to each other regularly.

You don't. You adjust the clock that is based on the Earth's rotation rate. The second is officially defined as 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom. That can't be wrong, it's the definition.That isn't a nice round number because it was chosen so that an atomic clock second would be very very close to (and a good representation of for many purposes) an Earth-rotation second. But the atomic clock second is the one and only second.Edited by JonF, : No reason given.

Only if you define "know" as perfect and complete knowledge. In that sense we don't "know" anything."We don't know everything therefore we know nothing" is a common and false creationist canard.

No, it's difficult to measure the rotation of the Earth and it changes back and forth too much to be useful in precise measurementsBTW, the earth rotates in a little less than 24 hours relative to the Sun because of its orbital motion. The units of time are arbitrarily chosen for convenience. There's nothing magical about 24 and 60. The Egyptians could have chosen 33 hours per day, 21 minutes per hour, and 137 seconds per minute. We would have chosen a different number of atomic transitions to represent a second and atomic second would be very close to an Egyptian second.You have severe difficulty distinguishing between what is arbitrary and what is physically required. Arbitrarily chosen by Man (and see below). Arbitrarily chosen by Man. Arbitrarily chosen by Man. And with leap seconds the two would be in sync. SFW? The duration between sunrise and sunset is near-impossible to measure and varies from zero to infinity depending on where you are on the Earth {ABE and the Earth's axial tilt and where it is in its orbit /ABE}. Not useful.And it does not have to be measured not does any system of units have to be based on it.The choice of what to measure and how to divide up that measurement is purely arbitrary. We don't even have to make it anywhere near Earth-rotation-based units. We could define a second as 10,000,000,000 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom. A nice round number. But it would be very inconvenient to convert between the two systems all the time, and all the non-atomic clocks in the world would have to be replaced.Edited by JonF, : No reason given.

If the duration of a day is based on sunrise and sunset, the duration varies from zero to infinity. The length is determined by the Earth's rotation, its axial tilt, where the Earth is in its orbit, and where you are on the Earth.Edited by JonF, : No reason given.

What Man knows about the origin of the universe and the origin of life fills many, many books. Far better writers than I have explained it in various levels of detail. I'm not going to try to better their efforts in a relatively brief posting. I'll be glad to dig up some links if you are interested.

Pedantically, "day" is a non-SI unit that is accepted for use with SI units. https://physics.nist.gov/cuu/Units/outside.Html.

No, time exists. The units in which we choose to measure it are arbitrary. As are all the other fundamental units we use; length, mass, electric current, temperature, amount of a substance (Avogadro's number), and luminous intensity.The map (seconds, minutes, hours,...) is not the territory (time) Edited by JonF, : No reason given.

So, I'm in a lab in Sheboygan, Wisconsin and running an experiment that requires timing to femtosecond precision. How do I ensure my femtosecond is exactly everyone else's femtosecond.(This sort of thing happens, except for the location. It's difficult to do using atomic clocks because you have to account for relativistic effects from differences in altitude and velocity).Oh, and, that equator is the celestial equator, not the Earth's equator. Thank you for acknowledging that I am correct saying that the choice of units is arbitrary and done for convenience. BTW, 60 comes from the Babylonians. It has more divisors than 10 or 12.While looking stuff up I found Wikipedia: hour. It mentions the ancient Chinese system of dividing the day into 100 marks, the Southeast Asian system of four quarters in the day and each divided into six hours (so the we would call their first hour of the first day quarter our 7 AM), and the Hindus in India:

quote:

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The Vedas and Puranas employed units of time based on the sidereal day (nakṣatra ahorātram). This was variously divided into 30 muhūtras of 48 minutes each or 60 dandas or nads of 24 minutes each.[40] The solar day was later similarly divided into 60 ghaṭiks of about the same duration, each divided in turn into 60 vinadis.[40] The Sinhalese followed a similar system but called their sixtieth of a day a peya.

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The rest of what you write is true but irrelevant to the arbitrariness of our choices of units. Except: The variable-length hour was discarded long, long ago except for some Jewish ceremonial applications. The history of the second is more complex than that.Seconds first appeared in the mechanical clocks of the late 16th century. Accurate measurement of seconds didn't show up until Huygens' pendulum clock in the mid-17th century. Nobody cared much about precise and available standards until the 19th century, but by then the second was pretty widely recognized as 1/86,400 of a mean solar day. This was formalized in 1940. But even then better standards were desirable. In 1956 the second was defined as 1/31,556,925.9747 of the tropical year for 1900 January 0 at 12 hours ephemeris time because the Earth's orbit around the Sun is more stable than the Earth's rotation, and this was adopted internationally in 1960. Then there was the current definition seven years later. Some day the second will probably be redefined by optical lattice clocks.There are actually three slightly different systems in use; which one you use is decided by convenience. From Wikipedia's article on seconds :

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A set of atomic clocks throughout the world keeps time by consensus: the clocks "vote" on the correct time, and all voting clocks are steered to agree with the consensus, which is called International Atomic Time (TAI). TAI "ticks" atomic seconds.[4]

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Civil time is defined to agree with the rotation of the earth. The international standard for timekeeping is Coordinated Universal Time (UTC). This time scale "ticks" the same atomic seconds as TAI, but inserts or omits leap seconds as necessary to correct for variations in the rate of rotation of the earth.[5]

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A time scale in which the seconds are not exactly equal to atomic seconds is UT1, a form of universal time. UT1 is defined by the rotation of the earth with respect to the sun, and does not contain any leap seconds.[6] UT1 always differs from UTC by less than a second.

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Depends on your point of view. It's one of four dimensions of spacetime, similar to but not the same as the three spatial dimensions. In many applications it's defined as what a clock measures, just as we often define gravity as a force exerted between masses.I bet you're going for "we don't know everything therefore we know nothing". We don't have to understand what time is to know that clocks are measuring something. We don't know what gravity is in the sense you're asking. (We have some hypotheses.) Does gravity exist?

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