Why do people use earth motions to determine units of time?

Answer 1

A great deal of human behavior, sometimes even our Biology, is linked to the day, the lunar month, and the year.

For example, the average human may spend approximately 8 hours asleep and 16 hours awake, for a total of one day.

An expectant mother will be pregnant for about 280 days, or about 10 lunar months.

Important changes in the weather happen at different points in the Earths orbit (the Year), the most important of which is the seasons. Different crops grow at different times of the year, and animals (that we may have hunted in the past) may migrate and become more or less available.

There are also, in the case of the deciduous forests of Europe and North American, stunning visual changes: in Autumn when the leaves change colour and fall from their trees, in Winter when the snows come and make the land white, and in Spring when the snows melt and the leaves and grass return. These all happen over a roughly 365 day cycle depending on where the Earth is on it's journey around the sun (the year).

So there have been historically excellent reasons to measure time (especially the day, the month, the season, and the year) based on the Earth's motions: lots of important things that happen to humans on Earth are inextricably linked with the Earth's motions.

Answer 2

Because it is easy to see, and fairly obvious.

The Earth spins on its axis, creating the day & night cycle. That's an unmistakable and easily agreed on fact. The Moon orbits the Earth, and we can see the phases of the Moon. All cultures used lunar cycles (originally) as the longer period of time. This, also, is pretty easy to see; the Moon waxes to the full, then wanes to the new, and everybody sees the same phase of the moon. It wasn't until the Romans started messing around with the calendar that the association of the "month" with the "moon" was lost.

Finally, the annual cycle of the year, from winter to spring to summer to fall and back to winter again was a fairly obvious one. If you live in an agricultural society, you need to know when to plant and when to harvest, and that's generally an annual cycle. Even where there isn't much temperature difference between summer and winter, the seasons generally impose a "rainy season"/"dry season" pattern that matches the year pretty well.

Answer 3

Days and years are obvious and convenient. Also, they don't suffer the "national bias" that is supposed to be such an impediment to standard units.

Answer 4

Because it is easy to see, and fairly obvious.

The Earth spins on its axis, creating the day & night cycle. That's an unmistakable and easily agreed on fact. The Moon orbits the Earth, and we can see the phases of the Moon. All cultures used lunar cycles (originally) as the longer period of time. This, also, is pretty easy to see; the Moon waxes to the full, then wanes to the new, and everybody sees the same phase of the moon. It wasn't until the Romans started messing around with the calendar that the association of the "month" with the "moon" was lost.

Finally, the annual cycle of the year, from winter to spring to summer to fall and back to winter again was a fairly obvious one. If you live in an agricultural society, you need to know when to plant and when to harvest, and that's generally an annual cycle. Even where there isn't much temperature difference between summer and winter, the seasons generally impose a "rainy season"/"dry season" pattern that matches the year pretty well.

Answer 5

A great deal of human behavior, sometimes even our Biology, is linked to the day, the lunar month, and the year.

For example, the average human may spend approximately 8 hours asleep and 16 hours awake, for a total of one day.

An expectant mother will be pregnant for about 280 days, or about 10 lunar months.

Important changes in the weather happen at different points in the Earths orbit (the Year), the most important of which is the seasons. Different crops grow at different times of the year, and animals (that we may have hunted in the past) may migrate and become more or less available.

There are also, in the case of the deciduous forests of Europe and North American, stunning visual changes: in Autumn when the leaves change colour and fall from their trees, in Winter when the snows come and make the land white, and in Spring when the snows melt and the leaves and grass return. These all happen over a roughly 365 day cycle depending on where the Earth is on it's journey around the sun (the year).

So there have been historically excellent reasons to measure time (especially the day, the month, the season, and the year) based on the Earth's motions: lots of important things that happen to humans on Earth are inextricably linked with the Earth's motions.

Answer 6

Days and years are obvious and convenient. Also, they don't suffer the "national bias" that is supposed to be such an impediment to standard units.

Answer 7

becous earth moshi is regular so peple use them to meaure time