Dating stuff, Confusing

[Cogman]

Ok I thought of this and decided to let you guys think of it. First this "Matter can neither be created nor destroyed". With that in mind, then all matter that is in the universe has to have always been here. So with that in mind, how do you date it? I mean, It has always been here, it will always be here. And, since it could not be created, New matter cannot be made. So all matter we have now has to be the same age. Right? So how can you date the age of a rock on earth? All the matter on the rock will have to be the same age, as it is everywhere else, Then also how do you date the moon. They dated it by samples of rocks, but there is no life or anything on them so they cant really say how old it is, right?

 

[Evadman]

For some things radio carbon dating is used. Carbon 13 ( I think? maybe 14?) turns into regular carbon at a specific rate called a half life. You can tell how old something is by the amount left. I forget the half like unfortunately.

Matter can be turned into "not matter". energy can not be distroyed. Matter is always chainging states. You can make matter with enough energy. Colliders have enough energy to create matter.

<edit>
Changed energy into "not matter" because it sounded confusing. Man, I need some sleep. 'Night.

 

[phrawd]

So all matter we have now has to be the same age. Right?

Not exactly. Matter is changed from one form to another, as Evadman said. So when you date something (using radiocarbon dating for example) you are not dating the intrinsic components of matter, but rather, dating them as a whole to create something (in one said instance, a rock). You can't really date neutrinos or fundamental subatomic particles, at least I don't know of any way. A question I'd like to know is what was there before the universe big banged out of the celestial womb?

 

[sxr7171]

Radio carbon dating does not measure the age of matter. It is a useful tool only for organic life forms. It works on the premise that one knows how much Carbon-14 is present in 1 gram of the tissues of a living being. Now after hundreds or thousands of years that amount of Carbon-14 is reduced accrding to its half-life. In this way we can tell how long it has been since an organism has died. Yes, this means that we have Carbon-14 in our bodies as a natural portion of the carbon in our bodies, and we can measure time since the death of ancient humans using radio carbon dating.

 

[Belegost]

First this "Matter can neither be created nor destroyed".

This idea is not the entire picture, it is more correct to say that matter and energy are conserved as a whole, but you can convert between the two.

As far as dating things, you're not dating the matter, you're dating the state in which the matter is. For instance, if you want to date a bone, you're not interested in how old atoms making up the bone are.

Most dating methods are based on unstable isotopes, isotopes such as Carbon-14, Uranium-238 have too many neutrons to maintain a stable atom, so eventually some form of radiation is given off, either alpha radiation, a particle consisting of 2 protons and 2 neutrons, beta radiation, also a particle, this time a single electron given off as one neutron decays into a proton and electron, and gamma radiation, a highly energetic photon, which usually is released along with one of the other forms.

Each time an atom loses mass by emitting a particle it changes it's composition, for instance U-238 emits an alpha particle, and converts to Thorium-234. This is the basis of dating, knowing what percentage of various elements in an object.

An example, you buy a brand new block of U-238, you know there is nothing that block but U-238. Yu put the block in a container and leave it for a few years, when you get it back out, you bust out your Ronco Home Mass Spectrometer and analyze some samples, you find that now it's made up of Uranium, Thorium, Lead, etc. If you knew how long it took for a given amount of Uranium to turn into the other elements, then you could use your data to determine how long the uranium block sat there. Dating methods work on the same principle, I take a rock, I analyze the elements in it, in almost everything there is at least one, and usually a few elements that can be used for dating. Since we can measure the time for the elements to decay, we can extrapolate backwards to get an estimate of how long the object has existed in it's current form.

Carbon-14 is common dating method for things that were previously alive, but have since died. Living organisms use carbon as a fundamental element, and there is a certain percentage of carbon in a living creature that is C-14. This percentage is more or less constant as long as the object is alive, but once it dies it no longer is renewing the carbon, and the C-14 begins to decay. Since we have very good data on howw much C-14 is in current living things, and we can make assumptions that the levels were similiar in the past, we can simply analyze an object to determine that C-14 content, and extrapolate from that how long ago the thing died.

 

[RossGr]

Matter may not be created or destroyed is a very limited concept of what is really happening. As has been said above matter and energy are interchangeable. So the same "matter" may take on very different forms depending on many things.

Initially stars formed from clumpse of Hydrogen, gravitational forces caused these clumps to grow, when they became sufficiently massive, fussion fires began to burn in the cores, these fusion fires, were combining energy from gravitational forces and matter to create new forms of matter, Helium atoms. This process continued creating ever more massive atoms. At some point in some stars a Nova or super Nova event occurs, this happens when the balance between fusion fires and gravitational forces become unbalanced. These massive explosions are the source of the heavy elements such as Iron Uranium etc. Iron, the core of the earth and the other planets holds an interesting place in the scope of the elements. It is the one element which cannot release energy through fission or fusion, you might consider it stellar ashes, it cannot support any form of nuclear fire. The implication of this is that the earth and every atom it is comprised of has been through 2 or 3 stellar fires (that means stars). So Iron by its very nature is new, as is all other heavy elements, in comparasion to Hydrogen which the starting point and has been around since near the begining.