How is time measured in the early stages of the universe?

Question

Many books describe the early eons of the universe in terms of things occurring for so many millions of years. Since our measurement of time (one year) comes from the earth's orbit of the sun, neither of which body existed for most of the early cosmic expansion, how is it possible to speak of processes as occurring over a quantity of years? Even using more sophisitcated time keeping, such as rates of particle decay or atomic resonance, how can those be measuring rods for time when those particles did not exist at the time being measured. In short, how can we quantify the passage of time early in the universe's history when the things we use as time's yardsticks didn't exist?

Answer 1

The basic unit of time in use today, the second, is defined in terms of the behavior of the cesium atom. If we believe that hasn't changed, we have a time reference valid for an extremely long time. If you want a standard valid before the first cesium atom existed, then recalibrate to the hydrogen atom. Cesium was chosen because this behavior can be measured with extreme accuracy and stability.

If you want any time measurement to be meaningful to the experience of an earthling, express it in years. We know what that means.

Your question is quite different from your explanation of your question. We have extreme difficulty measuring time intervals that happened a long time ago. We think a fossil is a million years old because we found it in a rock that we think is a million years old. And we think that because we found it below another rock that we think is 900,000 years old.

In astronomy and cosmology, we try (also with extreme difficulty) to measure the speed and direction of travel of galaxies. We then try to calculate (or guess) the speed, direction, and location of those galaxies a billion years ago.

All of this assumes that time is moving along at a constant rate, independent of how we measure it. What does it mean if that's not true? Perhaps Joao Magueijo can tell us.

Answer 2

Because any "yardstick" used for measuring is just an agreed upon concept. The year, second, picosecond, day, month, hour, week, etc are really just concepts for measuring time. They apply to the period of time prior to the existence of the Earth just as they do today because the people using them as units exist now and can relate to them as symbolic units. The beauty of the measurement unit is in the eye of the beholder (or yard stick holder, in this case).

Answer 3

The people measured time by the movement of the sun the device which was used was sun-dial and after some time people made out the latitudes and longitudes which is now used to measure time and date .
the date is now measured by the international date line (also the time is used in measuring date) but the first ever date was found out using the international date line 180 degree longitude .
Forgive me if this is not what you were looking for :)
yours sincerely,
Demon me

Answer 4

Maybe I don't understand your question completely, but just because the human concept of time didn't exist after the universe began doesn't mean that our concept of time can't be applied to that or any other period in the past. I didn't exist when the American Civil War took place, but it still lasted for five years.

Answer 5

This is a very good question. I'm curious about the true answer myself. Perhaps theoretical physicists have used the speed of light as their yardstick in the very early stages of the universe.

Answer 6

time started as soon as universe started

Answer 7

hm

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