A day is 24 + hours, a year is 365 + days ..Geologicaly are these values constant, what is the rate of change?

Question

Does the rate of change vary?

Answer 1

QFL has the best answer so far because he refers to the moon's tidal effect.

In geological time scales, there are two physical things that can affect the length of the hour, the day, and the year. These are (1) the mean distance between the earth and the sun; and (2) the mean distance between the moon and the earth.

From Kepler's laws, the period of the earth's revolution around the sun (our definition of the year) is a function of the earth's mean distance from the sun. As long as that distance doesn't change, the length of the year doesn't change. And as far as I know, the earth-sun distance is unchanging. For if it were to change (to increase, for example), the earth's mean velocity relative to the sun would have to decrease, and I can think of no applied force that will make this happen.

With the earth-moon system, it's a different story. The moon's tidal effects slow down the earth's rotation -- therefore the day gets longer -- and the gravitational force applied by the earth upon the moon slows down the moon. This last matters because technically, the earth and moon are actually orbiting around the sun. Sometimes the moon goes faster than the earth, and sometimes it goes slower. Throughout the lunar cycle, the moon is either passing the earth relative to the sun, or vice versa, the earth is passing the moon. It's the earth's gravity that causes this relative shifting of position.

Now, the moon's slowing down causes its distance from the earth to increase. (Again, Kepler's laws.) But as the moon's distance increases, the tidal effect of the moon decreases due to the inverse square law of gravity.

Putting all this together, the earth used to spin faster than it does today, so the day was shorter. And when the days were shorter, the hour would also have been shorter, since an hour is one twenty-fourth of a day.

But the month would also have been shorter, because the moon was closer in, and circling the earth at a faster rate.

That's as much as I can say; I don't know the rates of change, except to say that the rates of change are decreasing. Again because of the inverse square law, gravitational effects are greater when the distance is less. Conversely, when the distance increases, the rate of change decreases; acceleration is the second derivative of position.

Answer 2

Please bear in mind though that the days, months and the year is based around the Gregorian calander. Back in biblical times the calander only had 10 months and even today different calanders exist .i.e Jewish. There is nothing to stop us in the future adopting a different calander thus what is 24hrs, a day, a month and a year might not be the same in time as it is now - where will your constant values go?

What usually is a good indicator of geological change is much more visible than time, its changes in the rocks themselves, i.e. from a Claystone to a Limestone. These changes are either local, regional or sometimes global. Time, in terms of what we understand it today, is a vague notion as to the orbiting path of the earth around the sun, the earths tilt and its wobble. These factors play a vital part in determining the geological change of the earth. The great thing about geology is that it does not behave like a science experiment where there must be a constant, geology is not constraint by such man-made controls.

Search the internet and read some literature regarding the Milankovitch cycles and you will understand more about geological processes.

Answer 3

A year is actually 365 and (roughly) a quarter days. Hours are a man made concept, while years are based on the time it takes for the earth to journey around the sun. So hours, since they are defined, are constant. But years are a bit iffy. Perhaps over time as the sun runs through its lifespan, our solar system will change and our earth's rate of travel may accelerate or decelerate. This will make years shorter or longer. During the course of a human lifetime however, it's bound to stay roughly constant (But probably not precisely).

Answer 4

A day is the time it takes for the Earth to make one revolution about its axis. A year is the time it takes for the Earth to circle the Sun once. Both of these values are based on specific physical phenomena and can change. However, due to the law of conservation of angular momentum, they will only change under some very specific circumstances.
The length of a day will change if the radius of the Earth itself changes or if an external object impacted the Earth and imparted its own angular momentum on it.
The length of a year will change if the radius of the Earth's orbit changes, or if the mass of the Sun changes significantly (which would require nothing short of a cataclysmic event, such as another star entering our solar system).

Answer 5

NO IT IS NOT A CONSTANT BECAUSE THE DAY ONLY DEPENDS ON THE EARTHS ROTATION OF THE SUN AND THAT IS NOT CONSTANT OVER MILLIONS OF YEARS DUE THE EARTHS ORBIT WILL BECOME MORE ELLIPITICAL AND THE VALUES WILL CHANGE IT COULD ACTUALLY PUT THE EARTH BACK INTO AN ICE AGE AS IT ADVANCES FARTHER FROM THE SUN. AND TIDES HAVE TO DO WITH THE MOONS ROTATION OF THE EARTH NOT THE SUN. WHOEVER SAID THAT IS QUITE IGNORANT.

Answer 6

The rotation of the earth is slowing, so the days are getting longer. The geologic record shows through tidal rhythmites (daily tidal layers) that the length of the day was 21 hours 600 million years ago and 19 hours long 900 million years ago. Yearly records are harder to decifer.

Answer 7

The Earth as it spins on its axis is wobbling. Sort of like a top that is spinning down. Now, while not as fast as a top spinning down and soon falling over, the Earth IS doing this. As far as the orbit changing around the Sun, I am sure if you start seriously pondering Kepler's Laws it would show that eventually all the planets would have the elliptical shape of their orbits change.

Answer 8

Actualy years in the past they did not all have locks on the doors. I remember it being an merchandise in the files because for in the destiny they were going to close each and each of the shops in the state. they had to bypass and deploy locks on the doors of a straightforward form of the shops. i imagine locks are required now for causes reported above. also if there is against the law they need to fasten up the save so no individual is for sale in previously investigators can study the scene.

Answer 9

It's not a fixed rate of change. Periodically the earth must geo-leap, geo-hop or geo-skip; depends on the forecasted rate for that millennia. If the forecast is incorrect it is geo-countered in the following millenium.