# To what precision can we determine the age of the universe theoretically?

Does it makes sense to expect/hope that one day we will measure the age of the universe (in Earth's frame of reference for example) much more precisely, down to sub-year precision? Is there an absolute 0 for time (kind of like for temperature) that we could use instead of the year of our Lord or some other year?

Can we at least talk about a theoretical absolute age even if we might not be able to determine what it is? I'm thinking that even if we had perfect clocks counting seconds from the very beginning of the universe, due to relativity they might have readings that differ by years or more, making an absolute time impossible to set or maybe the expansion of the universe means this is a nonsensical question to ask. Is asking about absolute time like asking about absolute position?

• The commonly accepted "+/- 40.000.000 earth years" error margin of $\Lambda$CDM should be taken with a grain of salt. The actual error margin could be much larger, of the order of 1B years due to the Hubble tension. See physics.stackexchange.com/questions/611740/… and physics.stackexchange.com/questions/514882/…. Apr 26, 2021 at 21:16
• Age for who? Special relativity rears its ugly head. May 16, 2023 at 20:45
• @FlatterMann that's what I said in the second paragraph isn't it? There's still surely some distribution of ages (of rocks on the surface of the Earth if we have to restrict it further) we could describe.
– user86478
May 16, 2023 at 20:50
• That's my point: you know the answer, already. "The age" is observer dependent, and so is "the shape". We could argue about whether the age of the universe is the same in the local rest frames of observers that see the universe as (nearly) isotropic, but that leads to the question whether the universe is homogeneous at scales larger than several (hundred) times the Hubble diameter. My religious bet is "no, it isn't", but then... I am not religious and I don't bet and the question lies firmly outside of what science can do. May 16, 2023 at 20:53
• In cosmology, we tend to use the comoving frame of the CMB, as mentioned in physics.stackexchange.com/q/495821/123208 (I have some info on the CMB frame in physics.stackexchange.com/a/411082/123208 ). May 16, 2023 at 21:53

Within our present model of the universe, the age of the universe is deduced from observational data :

Ancient light from the Big Bang has revealed a precise new estimate for the universe's age: 13.77 billion years, give or take 40 million years.

13.770.000.000 earth years +/- 40.000.000 earth years.

If we accept the claim that it is the best precision, (ignoring maybe larger errors due to models used),the error given is too far removed for your "sub year precision" for it to be attainable, imo.

• Did you forget the famous Hubble Tension? The number you quote does not come directly from observational data, but from fitting it to the Friedmann cosmology, which is in an existential crisis as the worst theory of the mankind mismatching by whooping 95% the actually observed matter content in the universe. Feb 27, 2021 at 6:59
• @safesphere the error is the important thing, which is experimental, no matter what the theory predicts. Take the ratio: you cannot get great improvement no matter what the theory predicts in billions of years. Feb 27, 2021 at 7:03
• The Hubble Tension is the difference between relatively direct measurements (which are still not geometry independent) and fitting indirect observations to the Friedmann model. This difference is much larger that the error you quoted. The actual uncertainty is in the range of a billion years. Feb 27, 2021 at 7:08
• The Hubble tension is 67 to 74. With simple math this translates to about a 1.3-billion-year difference. Feb 27, 2021 at 8:08
• We should stick to the present calendar(s) until the accuracy is improved. Feb 27, 2021 at 9:29

Even assuming we have the correct cosmological model, the precision to which we can measure cosmological parameters is fundamentally limited by our vantage point. Our location in the universe is random, but every experiment we do is from the same random location. We can reduce instrumental error in measuring the cosmic microwave background, but we are always measuring the same inherently noisy pattern. This problem is called "cosmic variance".

In principle, we could discover a theory of everything that forces a certain value for certain cosmological parameters (perhaps the cosmological constant), allowing us to better fit the other parameters, or we could find maps of the microwave background from millions of years ago in the ruins of Atlantis and combine it with the current map to reduce the noise. Failing that, I think that future astronomical observations can only slightly improve the precision of the fit.

The key concept in the question is. "Is it theoretically possible...?" This a distinctly different question than whether it is practically possible. As astronomical instruments get bigger, their precision will also get better. The biggest current instrument in recent times is the Hubble with a diameter of 2.4m, which has produced an error of about 40,000,000 years. One can imagine theoretically creating a telescope the size of the solar system with a diameter of about 22,000,000,000,000m. If such an instrument were to someday be created, it would not be too surprising to me that the precision of the age of the universe will very possibly become less than a year.