Is dark matter for real ? And if so, do we know how it effects the previous estimates of the age of the a) the universe b) the solar system c) the earth ?
There really is a discrepancy between the amount of matter we can detect–dust clouds, gas clouds, stars, planets, black holes, and so on–and the speed at which this material orbits around the centers of galaxies.
In order to have the orbital velocity the galaxies would have to be much more massive than we think they should be.
The simplest explanation for this is that there is some sort of material in galaxies that exerts gravitational force, but not electromagnetic force. That is, it has gravity, but doesn’t absorb and emit photons. Hence “dark matter”.
There might be some other explanation, but if there is, it would be more complicated than dark matter, so probably dark matter is the explanation.
Multiple tests have shown the universe is about 13.8 billion years old, how would dark matter change that?
The age of the Earth and Solar System are based on the radioactive decay of long-lived isotopes like uranium 238 and thorium 232, which have no connection whatsoever to dark matter. The age of the Universe would depend on dark matter, but the first even moderately precise measurements of the Universe’s age were made after the existence of dark matter was already a long-established fact, and in fact the best measurements of the amount of dark matter come from precisely the same experiments that told us the age, so it’s already taken into account.
Yes, completely different methods used for determining the age of the universe and the age of the solar system.
For the above-mentioned uranium testing, a brief “plain English” thumbnail sketch: some types of minerals (such as zircon) while cooling from a liquid to a solid, “push out” lead from the growing crystal but allow uranium atoms to become part of the crystal lattice. Therefore, lead atoms found the lattice of zircon crystals are presumed to be the result of the decay of uranium atoms. Once you have established the half-life of those uranium atoms (and all the types of unstable atoms the once-uranium turns into before reaching stable lead) you can compare the number of lead atoms relative to uranium atoms in the crystal and calculate to see how long that crystal solidified. An additional helpful aspect of this type of testing is that there are two types of uranium that decay into two types of lead, and each type of decay takes a different amount of time. So you compare the calculations for uranium type 1 / lead type 1 and the calculations for uranium type 2 / lead type 2, and if they both give you the same age, then you know that your measurement is probably accurate and the sample not contaminated. (That’s the plain English version. For the mathy version, see this.)
The age of the solar system is determined by doing that testing on the most unaltered meteorites that can be found. The age of the Earth is assumed to be almost as old (with “almost” being a range of somewhere around 10 to 100 million years) as the meteorites, but the surface of the Earth has been recycled so much it is unlikely to ever find a mineral sample that is as old as the Earth.
As far as we know, dark matter has no effect on radioisotope dating.
“The age of the solar system is determined by doing that testing on the most unaltered meteorites that can be found.”
“As far as we know, dark matter has no effect on radioisotope dating.”
Assuming the unaltered meteorites serve as the baseline for the age of the universe, doesn’t it effect the radioisotope dating ? Or maybe there are terms that cancel out. I am trying to understand.
Meteorites serve as the baseline for determining the age of our solar system, not the entire universe. Our solar system is around 4.56 billion years old, the universe around 13.8.
To put things in perspective: Our Solar System consists of one star, plus an assortment of other objects all of which combined add up to about 1% of a star. Its furthest extent, by the most generous criteria possible, is a couple of lightyears out.
The Solar System is part of the Milky Way galaxy, which contains about a hundred billion stars. Its diameter is over a hundred thousand lightyears.
There’s another galaxy a lot like ours, but even a bit bigger, two and a half million lightyears away.
And the best estimate is that the observable Universe as a whole contains two trillion galaxies, and is over a hundred billion lightyears across. And that’s just the portion we can observe: We have no idea how much more there might be beyond that, and it may well be infinite.
So you can see that there is quite a bit of difference between the Solar System and the Universe.