Why is that? Please explain.
Because you assume decay (this state) existed.
It is the RATIO of isotopes that matters. That explanation doesn't work.
The ratios are what I was talking about. A pattern of more parent than daughter isotopes. The way you interpret that difference is by believing in a same state past and giving dates accordingly. The actual material doesn't matter.
It is basic chemistry. We observe that argon outgasses in hot lava.
So? How hot did rock used to need to get to melt? You don't know.
As we can see you are citing only how it now works and then delving off the deep end in belief.
We observe that zircons exclude Pb when they form, and include Uranium. This means that the only source for Pb in a zircon is the decay of U.
See above. Who asked you how they NOW form? What are you missing here? Either prove it was the same in the past or you may not use how it now works to model the past. Period. Ever.
All of the astronomical data demonstrates that the laws of physics have been the same for the last 13 billion years.
False. Your belief that time exists and exists as it is on earth, in the heavens is all you demonstrate. That ain't worth a dime.
If you disagree, then show me a single observation that is inconsistent with a same state past.
You have a whole belief set about the same state past that is designed to try to fit the evidence. All that matters is if you can prove the same state past, NOT what may seem some way.
The age of the rock is entirely independent of the fossil. We use the isotopes in the rocks to date them.
"[SIZE=+1]The oldest method is stratigraphy, studying how deeply a fossil is buried. Dinosaur fossils are usually found in sedimentary rock. Sedimentary rock layers (strata) are formed episodically as earth is deposited horizontally over time. Newer layers are formed on top of older layers, pressurizing them into rocks. Paleontologists can estimate the amount of time that has passed since the stratum containing the fossil was formed. Generally, deeper rocks and fossils are older than those found above them.
Observations of the fluctuations of the Earth's magnetic field, which leaves different magnetic fields in rocks from different geological eras.
Dating a fossil in terms of approximately how many years old it is can be possible using
radioisotope-dating of igneous rocks found near the fossil. Unstable radioactive isotopes of elements, such as Uranium-235, decay at constant, known rates over time (its half-life, which is over 700 million years). An accurate estimate of the rock's age can be determined by examining the ratios of the remaining radioactive element and its daughters.
For example, when lava cools, it has no lead content but it does contain some radioactive Uranium (U-235). Over time, the unstable radioactive Uranium decays into its daughter, Lead-207, at a constant, known rate (its half-life). By comparing the relative proportion of Uranium-235 and Lead-207, the age of the igneous rock can be determined. Potassium-40 (which decays to argon-40) is also used to date fossils.
The half-life of carbon-14 is 5,568 years. That means that half of the C-14 decays (into nitrogen-14) in 5,568 years. Half of the remaining C-14 decays in the next 5,568 years, etc. This is too short a half-life to date dinosaurs; C-14 dating is useful for dating items up to about 50,000 - 60,000 years ago (useful for dating organiams like Neanderthal man and ice age animals).
Radioisotope dating cannot be used directly on fossils since they don't contain the unstable radioactive isotopes used in the dating process.
To determine a fossil's age, igneous layers (volcanic rock) beneath the fossil (predating the fossil) and above it (representing a time after the dinosaur's existence) are dated, resulting in a time-range for the dinosaur's life. Thus, dinosaurs are dated with respect to volcanic eruptions."[/SIZE]
[SIZE=+1]http://www.enchantedlearning.com/subjects/dinosaurs/dinofossils/Fossildating.html[/SIZE]