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New Estimates for Universe's Age
Makarand writes "In a study published recently in the journal Science,
a team of researchers say that they are 95% sure the universe is between 11.2 billion
and 20 billion years old according to this
article on Space.com.
The new calculations from cosmologists at Case Western Reserve University and Dartmouth College involved new information about old star clusters in our galaxy and a better understanding of how stars evolve." Which blows my theory that the Universe is predated by Zsa Zsa Gabor, but oh well.
Religions will try to tell you on what day the earth was created. National newspapers will tell you the age of the universe, plus or minus a billion years. A scientist will give another scientist an estimate and a confidence level.
think more like 100,000 years or less, for anything above 5 solar masses. (1/lifetime) vs mass isn't a linear relation, far from it.
This IS science. The only thing you can "prove" is that the universe exists NOW, and many people would doubt even that (that you can prove it, not that it exists). If you want absolute yes/no statements, try religion.
All you can say in science is "given that assumption X is true, and our model is valid in these conditions, Y +/- Z will happen."
One of the basic rules of proper science is that any measurement without errors or confidence limits is meaningless.
At least, they should explain more in what are those estimates based
I'm sure they do in the actual article. Although I agree with you that the headline sucks.
They're only 95% sure. I'm 100% sure the universe is over 1000 years old. I'm only 5% away from the top scientists!
That raises a good point. When the hell did scientists start spouting off about how sure they were of anything?...
Your dissapproval is based on misunderstanding To be fair, almost certainly the misunderstanding is not yours, but in the space.com article.
"95% sure" doesn't mean that they're really 95% sure that they have absolute revealed truth. What it means is that, given the data and an understanding of the uncertainties in the data, and given the models and the uncertainties in the models, if we reproduced the experiment many times (i.e. we had many universes each of which produced stars that we could make the same measurements on), 95% of the time our data would give an age between 11.2 and 20 billion years old.
That's what a confidence interval means. That's what 95% sure means. Unfortunately, the Space.com article makes it sound the way you've interpreted it. Obviously, yes, it means that this is under the assumption that our theories are correct-- of course, some of the theories in question are pretty well tested and well believed. But you are right that you can't prove anything, you can only disprove them.
If you've ever heard Lawrence Krauss (the physicist quoted in the article) give a popular science lecture (he lectures a lot on the conflict between science and pseudoscience), he does emphasize this point. We do *know* some things from science. Even if it's a theory, we are pretty sure that some theories are right.
But "sure" is not really "we have revealed truth". It is a misunderstanding of the term "confidence" used in scientific papers, which really means "the data are consistent with...", and quantifies how consistent the data are.
-Rob
Although this is an obvious troll, I'll bite only because the date is wrong. The Bible would actually put the age of the beginning somewhere around 6,000 years.
Erm, 4003 BC is approximately 6000 years ago...
Ooh, a sarcasm detector. Oh, that's a real useful invention.
So, last year, they had an estimate of 13-14 billion. This year, it's 11-20 billion. Yeah to scientific progress!
/. does not allow sup tags) combined with standard cosmological models (omega m = 0.3, lambda = 0.7) implies an age of 13+/-2 Gyr. I tend to believe this one more. The errors quotes are probably 1 sigma errors (ie, 68 precent confidence - double the errors for 95%).
:)
Science is not exactly a reputable astrophysical journal. I would tend to go with the estimate of 13-14 billion years. See this ppaper - the figure of H0=73+/-2(r)+/-7(s) km s-1 Mpc-1 (hmm,
However, I am possibly biased, the author is my supevisor
Not quite, but close. There's a rough table at http://ast.star.rl.ac.uk/hr.html
Basically, for a star of 3 solar masses the figure is 370 million, about 3% of our Sun's expected life. That drops to 3 million years for a star of 60 solar masses.
Hmm... That does seem a bit small.
Really? This figure has been known for at least ~30 years.
1: there must have been a few big stars go bang to make all the elements of the earth.
Yeah, I think one SN in your environment will bring the content of metals in your environment up to about 1/10^5 of the value found near the sun. Stars born in these regions are called population 3 stars, and roughly represent the first stars to be born. All they had at birth was hydrogen (75% by mass) and helium (25%). Then came pop 2 stars, then pop 1 stars (like the sun). ie, there have been roughly 2 generations before us. The first stars to be born were probably very massive, and these died very very quickly (lifetime goes down as a factor of hmmm, maybe mass squared - I can't back this up by data, and my memory is dead after all those ginger martini's, and I want to go home), subsequent generations were probably biased more towards low mass, but this is still very much subject to speculation and simulations (we know virtually nothing about star formation, and the initial mass function (the number of stars formed as a function of their birth mass - more massive stars are increasingly rare), even whether it varies with time)
If the Earth is 4.5billion years old, then the solar system must be say 5 billion years old, how quick do large stars explode? must be say 1 billion - 3 billion years tops
Far shorter. 1 billion years is the lifetime of a very low mass star - only say 2 solar masses (I can't be bothered running my program to find out the proper number). Normal SN happen about 10^6 years after birth, but depending on mass.
- How can a range nearly equal to that of one of the factors itself be considered scientific?
It's called error analysis. You essentially add up all the error factors in all the things you measured and it gives you a measure of how accurate your result is. Having margins this big isn't really that uncommon - last I looked, the hubble constant range was between 50 and 100 km s-1/Mpc.A 95% confidence interval is a standard statistical test to see if a set of data could be part of another, larger set of data. Again, it's a measure of the accuracy of their answer.
They're a long way away. The light from them has to have taken a long time to get here (speed of light being constant) so the picture we see of them is the one made up of light that left a long time ago. You can also tell they're old because of their composition, which brings us to your next question...
They might have been, but it's a simple thing to check. The early universe was composed almost entirely of hydrogen, which they converted to helium. When they died, their helium was scattered and helped form younger stars, which started converting the helium into heavier stuff. If you check the light coming from a star, and it has heavy (ie heavier than helium) element absorption lines, it's formed at least from the matter of an older, dead star, and so has to be a second or later generation star. If it doesn't, it's an original.
We can't. It's the basis of science. You make your best guess based on what you've got, and you defend it until someone proves it wrong. Then you take their best guess and try to come up with something better...
Warning: May contain nuts
There is another very important point to recognize here. The HST Key project results (based upon Cepheid variable stars) is independent of the measurement/modeling of the ages of the oldest stars of Milky Way halo stars and clusters. Sure, both measurements each have significant systematic errors, but their uncertainties come from entirely different things! So the fact that they agree is quite reassuring. It also means that the measurements can be combined, at least to some degree.
With the newest generation of instruments and telescopes observing the Universe from radio waves to gamma rays, there will be new, independent methods of measuring the age and fate of the Universe. Already measurements from Type 1a supernovae are narrowing the uncertainties in some cosmological parameters. Other methods that currently yield very large error bars, but will be pivotal in the next few years are gravitational lensing (a detailed description here) and the Senyaev-Zeldovich effect (some details here).
When and if we get to the point where all methods yield the same result, we'll have our answer. In the meantime, if you just quote the formal results from just a single group, from a single type of argument/measurement, the systematic errors are going to be large, particularly when you're dealing with anything on cosmological scales!