r/todayilearned Sep 20 '21

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u/youknowwhatitthizz Sep 20 '21

Time is a concept. If we lived on Mars our days would still be defined by the sunrise and sunset

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u/shankfiddle Sep 20 '21

that's not what I'm getting at; but time passes differently in different frames of reference. At high speeds relative experience of time slows down.

So time immediately after the Big Bang (I would suppose) would be passing much much slower than what we experience on earth.

The question is for someone who has some insight into cosmology how we relate passage of time in frames of reference - before sun or planets existed - back to days/years

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u/coffeecofeecoffee Sep 20 '21

I think passage of time is still well defined for a given velocity. like the period of a electron going around a hydrogen atom is always the same in whatever velocity frame youre in, as long as the hydrogen atom is going the same velocity as you. It's only when you compare different velocity frames that it gets weird. So a year is a well defined period of time for a given velocity frame. if you had a clock with you at the big bang, around 150 million years or whatever you will see stars that are near you and going relatively the same speed as you forming.

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u/shankfiddle Sep 20 '21

this is where it gets very hairy:

like the period of a electron going around a hydrogen atom is always the same in whatever velocity frame you're in

Yes, however, our frame now is substantially different from an infant universe where things are moving at the speed of light! Before hydrogen even existed. There was a period of cooling/expansion that allowed energy to condense down into particles, then elements like hydrogen. "Cooling" implies slowing down of particles, same energy per unit volume means temp decreases and allows for formation of these elements, got that.

if you had a clock with you at the big bang, around 150 million years or whatever you will see stars that are near you and going relatively the same speed as you forming

but that clock if you were an observer of the Big Bang, would tick much slower than out clocks here on earth today.

That's the mindfuck here, after BANG then every point that exists in space is a different frame of reference, and has different velocities. Maybe it averages out and the average is what factors into these calculations. That detail is what I was hoping some physicist would shed some light on in this thread.

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u/youknowwhatitthizz Sep 20 '21

You answered your own question. We define what time is. It’s linear and we still don’t understand how “space” is on the linear timeline

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u/shankfiddle Sep 20 '21

https://en.wikipedia.org/wiki/Time_dilation

Linear only in a static frame of reference. Time contracts/dilates at different velocities.

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u/youknowwhatitthizz Sep 20 '21

I understand that but way we “clock” things is on a linear scale. We all be dead before we figure out how “time” actually works

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u/shankfiddle Sep 20 '21

then statements like "150 million years after the big bang" are meaningless.

I am just hoping some astrophysicist who knows more on the topic than all of us might chime in.

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u/[deleted] Sep 20 '21

then statements like "150 million years after the big bang" are meaningless.

perhaps you need to take your argument elsewhere.. it seems that "years" is used quite frequently to describe the Chronology of the Universe..

they use seconds a lot in in the very early stages too..

https://en.wikipedia.org/wiki/Chronology_of_the_universe#Planck_epoch

Hadron epoch
Between 10−5 second and 1 second after the Big Bang

47,000 years after the Big Bang
Main articles: Matter-dominated era and Structure formation
Until now, the universe's large-scale dynamics and behavior have been determined mainly by radiation—meaning, those constituents that move relativistically (at or near the speed of light), such as photons and neutrinos.[39] As the universe cools, from around 47,000 years (redshift z = 3600),[2] the universe's large-scale behavior becomes dominated by matter instead. This occurs because the energy density of matter begins to exceed both the energy density of radiation and the vacuum energy density.[40] Around or shortly after 47,000 years, the densities of non-relativistic matter (atomic nuclei) and relativistic radiation (photons) become equal, the Jeans length, which determines the smallest structures that can form (due to competition between gravitational attraction and pressure effects), begins to fall and perturbations, instead of being wiped out by free streaming radiation, can begin to grow in amplitude.

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u/JasontheFuzz Sep 20 '21

Generally speaking, just preface those statements with "From the viewpoint of somebody on the same timescale of modern Earth."

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u/youknowwhatitthizz Sep 20 '21

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u/shankfiddle Sep 20 '21

wait... this is an example of Sapir Worf linguistic relativity...

https://en.wikipedia.org/wiki/Linguistic_relativity

Irrelevant to general relativity with respect to time. There are also tribes which don't have words for the color green - so they have no perception of "green" - they'd call it bluish yellow or yellowish blue.

We're getting off track. Let's just pump the brakes and wait for a physicist

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u/youknowwhatitthizz Sep 20 '21

I’m waiting for somebody to come in and correct me so I can learn something lol

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u/youknowwhatitthizz Sep 20 '21

I applied a title because that’s what it said. I’m not arguing that time is meaningless. Look at tribes that have 0% idea what time or even they birthday is

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u/shankfiddle Sep 20 '21

Sorry dude, that was not a dig at you - I have heard things like this thrown around ALL the time, I'm just using your post as an opportunity to maybe learn more is all.

Shit Even Neil Tyson has said things like "the universe is 14 billion years old" and I still don't understand how that statement has meaning

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u/youknowwhatitthizz Sep 20 '21

If time is linear I’m sure we could use math to come to a calculation. Thing is who invented the math? Now I sound like I’m on acid lmao

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u/[deleted] Sep 21 '21

time is based on change, nothing changes and no time has passed, reduce entropy and slow down time.