How Does Time Dilation Affect Our Understanding of the Universe's Age?

[Shakes]

Hi Guys :)

Im no scientist or such, just a normal person pondering about stuff so go easy on me.

I lernt that if we look deep into space we are looking into the past. by looking at distant galaxies we can tell how old they are by looking at their stage in development. I guess that's how we can tell how old the universe is. (13.75 ± 0.11 billion years)

now I lert that time itself ticks differently depending how fast you move and where you are. Or should I say the mass of an objeckt near you.

So now I am wondering if I was at a very early point in time where the Univers still is a baby. the density of the universe is so great with such a huge mass that time should tick slower. or not?
on the otherhand the mass probably has't changed. but at that time all the mass was in one place.

If this is true and time moved slower at that time how would we feel it? Would I be able to watch the clock tick verry slowly or would'nt I notice anything? And if time did move slower at that time how can we say for sure that the universe is 13.75 ± 0.11 billion years old? Wouldent the universe be older than we think?

one more thing. If the pace of time is'nt always the same, how can we messure time regardless to speed and mass?

Please excuse my spelling. I'm not english :)

 

[BruceW]

I lernt that if we look deep into space we are looking into the past. by looking at distant galaxies we can tell how old they are by looking at their stage in development. I guess that's how we can tell how old the universe is. (13.75 ± 0.11 billion years)

Light travels at a finite speed, so the light we see from other stars left them some time ago. The light from further away stars has been traveling to get to us for a longer time, so we are seeing an image of them from a longer time ago.
Also, we can tell how old the universe is by seeing how fast other galaxies are moving away from us, and approximating the time at which everything was in the same place. (In big bang theory, we assume the universe was initially very small, then expanded).

one more thing. If the pace of time is'nt always the same, how can we messure time regardless to speed and mass?

We talk about cosmological time when we talk about the evolution of the universe, which means that at a particular cosmological time, the universe is at a particular stage in its evolution. Therefore cosmological time is independent of the masses, or velocities of observers.
Also, the universe was greater density in the past, but we wouldn't 'feel' time ticking differently. Just like someone in the gravity of a planet doesn't feel time ticking slower. Every observer feels like their own time ticks normally and that clocks in other reference frames tick different to normal.

 

[Shakes]

Yes light travels at a finite speed, but if it passes a large mass its path bends. so it would take longer to get to its destination as if did'nt pass any mass object at all. so say light was to move a distance x at a time where the universe was verry small, wouldn't it have a longer path due to the huge mass as it would now moving the same distance? I can imagen that there was more matter in a spot in the early universe as there is now resulting to a larger mass. or not?

 

[BruceW]

When the universe was very small, matter and radiation were coupled. This means that radiation was absorbed and emitted all the time. So when the universe was very small, light was not able to free stream in the way it does today. That is why we say the early universe was opaque (because you wouldn't have been able to see anything). (Of course, humans wouldn't have been able to exist in the very early universe, so you wouldn't survive, let alone see anything).
As the universe went on, radiation and matter decoupled, and the first few photons that existed in the transparent universe started free-streaming, and can now be seen as the cosmic microwave background radiation.
After this, the universe was more dense than it was now, but there was no large structures like stars or galaxies. The galaxies formed sometime after this, and the universe kept expanding and the average density kept getting less.
Scientists only used light sources from relatively close galaxies to calculate their speed relative to us. Therefore, the density of the universe was pretty much the same as it is now when the light was made that they use to calculate age of universe.
(In other words, they didn't use light from the beginning of the universe to calculate the age of the universe).