Lula posts:
carbon/radioactive dating methods of measuring rates of decay certainly have usefullness...jit's just that it must now be admitted that scientists cannot use this to determine the age of the earth as being 4.5 billion years old. All this is is wishful guessing.
Zoo posts:
I would like a link to this. ~Zoo
I don't have link, but will quote directly including the highlights from my daughter's 10th grade biology book by Kenneth R. Miller, Ph.D. Prentice Hall Fourth Edition, 1998.
Page 272......Darwin and other scientists have accumulated a vast amount o0f evidence that proves that evolution has occurred. Some of the evidence certifies that planet earth is more than four billion years old....Much of the evidence is found in the rocks of the earth itself.
Evidence that supported the idea that the eatrth was very old first came from geologist James Hutton in 1788. Hutton proposed that rocks, mountains and valleys had been changed gradually ...and becasue these processes operate slowly, Hutton argued the Earth had to be more than afew thousand years old.....
In 1830, Chrales Lyell carried these arguments further. Lyell's work was an important influence on Darwin's thinking. The evidence proved to Hutton and Lyell that the Earth wasvery old. ... At the same timeother sceintists while examining Earth's rocks began to make some startling idscoveries. In the stones they examined they found fossils.
Pg. 273...Earth's story is not complete without a "clock" totell us when things happened. Dating the Earth's past with the help of a record in the rocks is called the geologic time scale. ..More than 100years ago researchers noticed that certain layers of rock often appeared in the same verticalorder where everthey were found. It is the position of the layers relative to each other that determines their age. This knowledge helped geologists assemble a column of rocks in which each layer represented a different period of time.
Lower rock layers were depositied before the upper layers provided the upper layers have not been disturbed sincethey were formed. In addition fossils in the lower layers are older than fossisles found in the layers above them. Relative dating is a technique use to determine the age of the fossils relativeto other fossils found in the differentlayers of the rock. However, because geologists did not know howlong ittook for the layers to form they could not determinethe actual age of the fossils.
In the middle of this century, scientists were provided with a tool called radioactivity that could determine the actual age of rocks. Rocks are made up of different elements..some are radioactive....(defines half-life)...Each radio element has a different half-life. Uranium 238 hasa halflife of 4.5 billion years During that time half of the uranium 238 atoms in a rock sample decay into lead 206. Carbon 14 has a half life of 5770 years and half the carbon 14 decays to nitorgen 14. Elements with different half lifes provide natural "clocks" that tick at different rates. When properly interpreted these clocks help scientists date rocks...
Suppose geologists have uncovered what they think is avery old rock one they think might date back to the birth of our planet...to determine the age, they measure and compare the amounts of Ur 238 and lead 206 it ocntains. Next they determine how much lead has been produced by radioactive decay since the rock was formed. Becausewe know the halflife of ur 238, we can calculate rocks age.
Pg. 275....Because it has a relatively short half life, c-14 isn't really useful in dating samples that are more than 60,000 years old ..after this period there is really too little carbon 14 left tomeasure accurately...page 276....The traces of radioactive isotopes enable scientists to calculate the actual age of of a sample..process known as radioactive dating..The evidence provided by radioactive dating along with observations of loong trm geological processes has enabled geologists to compile a remarkable accurate history of life on our planet.
Using this data, scientists have determined that the earth is about 4.5 billion years old....by combining radioactive dating, relativedating, and observations of importanet events in the history of life on Earth scientists have divided the 4.5 billion years into large units called eras.
Page 280 ...to place an absolute date on a fossil, scientists look for a sample of rock fromame geological layer and test its age by using radioactive dating. Potassium 40 works well with old fossils anbd c-14 is an accurate way of dating more recent fossils.
See what I mean about my frustration with what they teach unwary students? Radioactive dating isn't as straightforward as this...it's not 100 prooftrustworthy...it's loaded with problems...
first we don't know how much Uranium 238 was in the rock in the first place and there is no way to tell how much lead in the came from Uranium or how much lead there was from the start.
Second no one knows for absolutely certain that Uranium has always broken down at the same speed. Was the rock sample polluted somehow? What if somelead wasmixediniwth lava beforeit wasformed? or washed into by ground water ust before it hardened?
It's a known fact that scientists have done radioactive dating on rocks of known age and come up with dates that were wrong by tens of millions of years. Take the Hawaiaian volcanoe that erupted in 1801. Scientists tried to date the lava 12 times and came up with dates from between 140 million years to 2.96 billion years. Again radioactgive dating doesn'tprove anything about the age of the earth....at best it's an attempt, an assumption to date the age of rocks and that's how it should be purported in science text books..