Age of Universe: Defining Time from Big Bang

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The discussion centers on the challenge of defining a universal time elapsed since the Big Bang, given that the universe is composed of spacetime and time is perceived locally. A participant highlights the complexity of measuring time on a cosmic scale due to variations in local time perception. Reference is made to a detailed answer provided in the cosmology FAQ, which addresses these nuances. The conversation emphasizes the intricacies of cosmological time and its implications for understanding the universe's age. Overall, the topic raises important questions about the nature of time in relation to the universe's expansion.
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I may be simplifying but if the universe is spacetime and time is local how can you define a time elapsed from the big bang for the whole Universe?
 
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Hi, Chewz,

Welcome to PF!

That's a good question, and Marcus has written up a nice answer to it as part of our cosmology FAQ: https://www.physicsforums.com/showpost.php?p=3332515&postcount=7

-Ben
 

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The formal paper is here. The Rutgers University news has published a story about an image being closely examined at their New Brunswick campus. Here is an excerpt: Computer modeling of the gravitational lens by Keeton and Eid showed that the four visible foreground galaxies causing the gravitational bending couldn’t explain the details of the five-image pattern. Only with the addition of a large, invisible mass, in this case, a dark matter halo, could the model match the observations...
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Thread 'Big Bang and Infinite Universe'

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