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Perfect-Editor-5008 t1_jd6pc5p wrote

Time is a human construct. We have named a year to be the time it takes for 1 orbit of the sun. However every planets orbit is different in duration. Hence a "year" is different depending on what planet you are on. So say an orbit for a planet is 100 years in the way we look at time then the universe to them would only be 138 million "years" old.

You also need to remember that when we started keeping track of days and hours it would have been possible to break them up differently than we did. We could have had days with 57 "hours" in a day, 10 "days" to a month and so on.

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urzu_seven t1_jd6tm8j wrote

Time is not a human construct. Time exists whether we do or not. The labels we choose are constructs, but the underlying passage of time still occurs, whatever we label it.

Further some things, such as a year, are defined by external factors, namely the Earths orbit around the Sun. This does not change with the existence of humans. It is a known quantity. The orbital periods of other planets are indeed different, but thats not what is referred to by "a year", which is why you have to qualify in circumstances where thats what you want to talk about.

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Target880 t1_jd7e29x wrote

>We have named a year to be the time it takes for 1 orbit of the sun.

That is not the case. The year we base our calendar on is the one cycle in the season on earth. You can pick the time between March Equinox and next March Equinox. This is a tropical year

It is it and the average solar day we try to make a calendar from. because there is not an integer fraction between the you need to add leap years

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An obit around the sun relative to a star far away is a sidereal year. It differs from the tropical year by around 20 minutes. It adds up to around 1 day of change in 72 years so not a lot but very relevant if you, for example, do celestial navigation.

Over a long time it has a larger effect, Compare the day that typically zodiac and when the sun really is in the sky, there is a difference of around 20 days because of the 20 minutes difference over more than millennia.

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