# What is Age of universe: Definition and 37 Discussions

In physical cosmology, the age of the universe is the time elapsed since the Big Bang. Today, astronomers have derived two different measurements of the age of the universe: a measurement based on direct observations of an early state of the universe, which indicate an age of 13.772±0.040 billion years within the Lambda-CDM concordance model as of 2018; and a measurement based on the observations of the local, modern universe which suggest a younger age. The uncertainty of the first kind of measurement has been narrowed down to 20 million years, based on a number of studies which all gave extremely similar figures for the age. These include studies of the microwave background radiation by the Planck spacecraft, the Wilkinson Microwave Anisotropy Probe and other space probes. Measurements of the cosmic background radiation give the cooling time of the universe since the Big Bang, and measurements of the expansion rate of the universe can be used to calculate its approximate age by extrapolating backwards in time. The range of the estimate is also within the range of the estimate for the oldest observed star in the universe.

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1. ### I Galaxy recession and Universe expansion

Hi, I'm aware of the measured recession of the galaxies in our universe and the universe expansion itself cannot be understood as an "ordinary" velocity/speed (for instance in the FRW solutions of Einstein's equations). Can you kindly help me clarify this topic ? Thank you.
2. ### I New research puts age of the Universe at 26.7 billion years

The article https://phys.org/news/2023-07-age-universe-billion-years-previously.html#:~:text=42-,New%20research%20puts%20age%20of%20universe%20at%2026.7%20billion%20years,as%20old%20as%20previously%20believed&text=Our%20universe%20could%20be%20twice,%22impossible%20early%20galaxy%20problem.%22...
3. G

### Is gravitational constant unchanging over age of universe?

do we know for a fact that the gravitational constant has always been the same since the dawn of the universe? I feel like gravitational forces should slowly be decreasing as the universe ages (meaning that assuming mass of Earth doesn't change, we should weigh a bit less in a billion years)...
4. ### A Space time expnasion, age of universe.

I was thinking about the age of the universe which is said to be 13.8 billion years approximately. I read that this is derived from two sources , calculating the life of the oldest stars in the observable universe and from extrapolating backwards the distance which is radius from Earth to all...
5. ### Does age of Universe reveal its size?

Does knowing the age of the universe (13.8 billion? ) say anything about size of the universe (besides the observable size)?
6. ### Help with Python computation to calculate age of universe

Homework Statement I'm using python to calculate the age of the universe, by working out the distmodulus for a set of galaxys (using the V and I bands) then working out the distance in parsecs and then hubbles constant etc... I keep getting values that are 10s of magnitudes out which I assume...
7. ### Is the Universe Expanding Faster Than the Speed of Light?

I'm trying to reconcile the age and size of the universe. The size of the universe is more than twice the distance light can travel in the time it has existed. Does this mean that the universe is expanding faster than the speed of light or that it did initially and has slowed down since? I...
8. ### Age of Universe in Planck normalized units

Hello, I've a problem. I need to find the age of universe in normalized Planck units. In my case, I'm using Planck mass = 1 and: ##H = 1.18 × 10^{-61} \times t_P^{- 1}## With these values, how can I find the age of the universe? Thanks!
9. ### Age of the observable Universe?

Forgive my ignorance?.. If we can see 13.8-ish billion light years away how can the universe be the same age? Matter cannot travel at the speed of light, so how are we as far away (in light years) as the universe is old?
10. ### Age of the observable Universe?

Forgive my ignorance?.. If we can see 13.8-ish billion light years away how can the universe be the same age? Matter cannot travel at the speed of light, so how are we as far away (in light years) as the universe is old?
11. ### Determining The Size and Age of Our Universe

The Size and Age of Our Universe If the universe is 14 billion years old, (roughly) then we can only see out in any direction for 14 billion light years. Thus any stars beyond 14 billion light years are invisible to us because their light hasn’t had time to reach us. If we cannot find an edge...
12. ### Age of universe -- Probability why it is so young?

I'm a retired geologist ... Know little about cosmology or quantum physics so will defer to others. Please excuse my rambling question. Something has always 'made me wonder' about the potential fate of the Universe. Almost all models predict either an infinite Universe or a Universe that...
13. ### Calculating the Age of Planets without Radioactive Dating

I understand that it's possible to calculate the age of terrestial planets through radioactive dating their soil. However, the gas planets present a different challenge since we cannot currently land on them. Any ideas on how to calculate their ages in a different manner?
14. ### What is the correlation between the age and size of the universe?

Please help me understand this. The age of the universe is given as being about 13.8 billion years. The size of the universe is estimated to be 93 billion light years ( https://en.m.wikipedia.org/wiki/Universe) Since the oldest light to reach us comes from 13.8 light years away, why do we...
15. ### What is the Definition of the Age of the Universe and How is it Determined?

After a recent conversation, I was trying to determine if there is an online authoritative definition for the age of the universe. The Wiki article states "the International Astronomical Union presently use 'age of the universe' to mean the duration of the Lambda-CDM expansion", but the...
16. ### What factors affect the age of the universe?

Acc. to general relativity time runs slowly near a massive body.So, i have a question bothering me from some time that if time for every body/object in universe runs at a different rate then how can we determine the age of universe i.e. 13.72 billion years. Near a black hole as time runs...
17. ### Is age of universe adjusted for gravity?

The estimated age of the universe is often stated to be about 13.7 billion years. But I've never seen any qualifiers on that age. We know that time passes slower the greater the gravity field you're in. Even the difference in gravity between the Earth's surface and orbit is enough to cause...
18. ### What is the age of the universe in billions?

Hi, The Universe in 14 billion years old. Is that then: 14,000,000,000,000 or 14 million million as in 1.4x1013 years old or 14,000,000,000 or 14 thousand million as in 1.4x1010 years old (I know a billionaire has a thousand million 1,000,000,000) Thanks,
19. ### Time Dilation vs Percieved age of Universe

I've pondered a hypothetical problem Take as time perspective "A" as being relative time dilation of Earth Time dilation "B" being half of "A" slower due to relativistic effects. assuming both "A" and "B" were both formed at the same time say 5 billion years ago. If you were to...
20. ### Quantum Confusion - Does not exist until it's observed and age of universe

Quantum Confusion -- "Does not exist until it's observed" and age of universe Hi. I ran across this: http://physics.jamesbaugh.com/quanta.html QUOTE: "It is a problem of assuming values of properties are "out there" independently of the acts by which the values are determined. The...
21. ### How to calculate CBR lambda vs age of universe?

hello, I'm wondering how to calculate, even approximately for the relatively mature universe, what the CBR wavelength was as a function of age of the universe. I get that the CBR began during recombination, though have read different values for the black body temperature at that...
22. ### Age of Universe relative to what?

People always say the Universe is 14 billions year old. But what does that mean? What is the time of the Universe relative to?
23. ### Age of Universe (Liddles Modern Cosmology)

Hi, I am currently reading Liddles Introduction to Modern Cosmology (2nd Ed) and having trouble with problem 8.4, about the age of the universe with a cosmological constant. The question asks to derive the formula for the age by first writing the Fridemann equation in such a model as...
24. ### Age of Universe: Is There an Alternate Perception?

I was wondering if, immediately following the expansion of the universe there might have been objects of matter with immense gravity like that of a black hole. For the observer on such an object that still exists, what would the age of the universe be? You could substitue this with an object...
25. ### Does the Age of the Universe Need to Factor in Light's Expansion?

Age of Universe inaccurate?? Hi. i have a question that could already been nullified. Reading about the CMB it occurred to me that normal light is around 370 - 770 nm in wavelength and a microwave could be upto 30cm long.. That means light has been expanded a million fold?? (not sure) since...
26. ### Age of universe and time dilation.

Something that always got me thinking about is time is relative to the speed of the object (time dilation) how can we determine age of universe. Here is an example of what I'm thinking. When the big bang happened, imagine if certain parts of the big bang it got flung at different speeds...
27. ### Age of universe and relativity

Hi, one of physician from Yale Univ explained first 6 days in bible can be very similar to 16 billion years if we understand relativity. His theory tells that first day after the big bang, temperture of the universe was around 3 trillion times higher which means frequency of universe...
28. ### Calculating Age of Universe with Hubble's Constant

I am having trouble understanding how to use Hubble's constant to calculate the age of the universe. I know that 1/H = a distance on time equation, thus the age can be worked out i also know that the answer is in seconds and generally to a high power such as 17 However what puzzles me is...
29. ### Calculating Age of Universe Using Redshift: 0.6

Hi i am confused as to how to calculate the age of the universe with redshift say for example The age of the universe now is 13.4 billion years old (and a critical universe). How do i find the age of the universe if it was a redshift at say 0.6?? Do i have to find the scale factor first...
30. ### Age of Universe, Redshift & Scale Factor

Homework Statement Assume that the current age of the universe is 13.4 billion years old, and that we live in a matter-dominated, omega_m = 1, critical universe, what is the age of the universe at redshift 0.6? HINT: use the current age of the universe to pin down the proportionality...
31. ### Is the Age of the Universe Relative and What is the CMB Speed Measured Against?

I was just thinking... :-p perhaps this is a dumb question & the two are unrelated. But, they say the universe is roughly 14 billion years old. My question would be, relative to who?
32. ### Astonishing Coincidence: Age of Universe in $\Lambda$CDM & Milne Cosmologies

Coincidence of Universe age in $\Lambda$CDM and Milne cosmologies I wonder why... Just another example of the degeneracy* perhaps? Garth (*Now accepted for publication in Astrophysics and Space Science)
33. ### How to calculate age of universe with a certain redshift?

Hi i am confused as to how to calculate the age of the universe with redshift say for example The age of the universe now is 13 billion years old (and a critical universe). How do i find the age of the universe if it was a redshift at say 10?? Do i have to find the scale factor first? I...
34. ### Reconciling Assumptions: Understanding the Concept of the Age of the Universe

Meaning of "age of universe" This question may have been addressed somewhat indirectly in other posts, but I'm interested in specifics. Exactly what assumptions about time (and the universe) are implied by a statement like, "The age of the universe is X years old"? In particular, does this...
35. ### Question on the age of universe

As you go back in time,the gravitating bodies come closer and closer.So the gravitational field gets more and more intense.We know that clocks move slower in the presence of a gravitational field---so as you go back in time the clocks become slower and slower.So how can we say,using today's...
36. ### Could the age of the universe be older than we thought?

Recently I read that Universe is 156 Billion Light Years in size. Even if every thing moves at speed of light, a 13 Billion years old universe should not have radious more than 13 Billion years. Is it Correct? Can the rate of expansion exceed speed of light?
37. ### Age of universe compared to age of sun.

I'd be interested to hear people's comments. One thing especially. The current estimates are of the order of 20bn yrs and 5bn yrs respectively (the actual values are not important ... it's the 'order' of the ratio that interests me). So, our sun has been around for a quarter of the age of the...