How do you determine the age of rocks by radioactivity.?
915684
Very roughly:  by comparing the ratio between a radioisotope and its "daughter product", and with the knowledge of the radioisotope's half-life, calculate the amount of time needed for the observed ratio to develop.\n\nIn short, if there is a 50-50 split between the radioisotope and its daughter product, one half-life has passed.
382215
The Earth is assumed to be about 4.6 billion years old, and unlike what everyone else said, it's not based solely on anything contained on Earth, including carbon dating. The oldest solid material found on Earth is about 4.1 billion years.\n\nThe guess -- and that's all it is, a guess -- is based on the rate of radiological decay of material on Earth and in meteorites found on Earth and around the solar system.\n\nIf you assume that the entire universe is formed from a common pool of matter (the essence of the Big Bang theory is that all material in the universe came from a single, supercondensed source that exploded); if you assume that therefore, all the matter in the universe has been equally distributed in all directions; if you assume that the rates of decay in all radiological material in the universe are consistent regardless of time, their position in the universe, etc.; then you can derive, by comparing the same kind of radiological material from celestial bodies that were not formed in our solar system, bodies that were part of our solar system when it formed, and that material now on Earth, the age that the Earth must be at the time it began to take solid form.\n\nThe paticular materials used to get that age is Lead-206 / Lead-207, which are the products of decay in Uranium-238.\n\nThis is further supported by temperature measurements of the universe and the evidence of background radiation from the timing of the Big Bang, which is assumed to have occurred about 15 billion years ago; given the rate of expansion of the universe visible to us, and the rate of change in both the speed of that expansion, the temperature of the universe and the density of space, we can verify the assumptions of the Earth's age to be within the estimation of a "young Earth" of 4.6 billion years old.\n\nAlso, to the person who said "The Bible": If you derive the history of the Earth from the Bible, as countless theological scholars have done through extensive research, it's about 6,000 years old; no scholarly Biblical research places the age of Earth at more than 10,000 years old.\n\nIf you want to believe that, in the face of overwhelming evidence to the contrary, that's fine. But you should at least agree with your evidence before citing it.
165799
You want us to calculate acitivites?\n\nYou need to determine the ionic strength and atomic radius in order to do that.
629421
Age of the "world," taking Earth as the "world"...scientists estimate about 4.54 billion years.  Estimate was confirmed by radiometric dating using rubidium (and other decay series).  Radiometric dating is something I study, so that's why I trust this estimate.
178387
Current models of Solar System formation indicate that all the  solid objects in the solar system (planets, moon, asteroids, etc) formed around the same time.  The oldest, unaltered piece of solid material we have found is about 4.6 billion years old (it is a particular type of meteorite).  So we place the formation of the Earth at the time period.\n\nWe can't find any Earth rocks that old, as earth has experienced far to much volcanic and techtonic activity in the past to preserve any of these original rocks.  We can and do find rocks as old as 3.8 billion years in the northeast portions of Canada, and even older samples have been found in the Australia region.
348469
Too long to list:\nhttp://seis.natsci.csulb.edu/bperry/ROCKS.htm\ngood site
508155
Write the word 'radioactivity' in www.google.com.Then collect watever information u need.
494583
A few years ago (1980s) a company was marketing a nuclear device for determining metal content of rocks.  This was a hand held device, and it worked very well.  I don't remember the manufacturer, but I know that it existed, and I saw it work.  The only problem was the nuclear source material.  In order to penetrate to any depth in the rock, it's nuclear source needed to be very powerful.  I think this was considered too much of a liability, and the company quit manufacturing the device.  I'm sure that you can still find one around.  I saw this demonstrated at a geologist's convention in Reno.  I think it was 1983 or 1984.
851623
Earth's age is based on several things:\n\n1) dating meteorites. When we find a meteorite from this solar system that has a similar composition to earth, you get many young ages, but the oldest and most common date to 4.6 Ga (billion years).\n\n2) isotope trends. When you look at certain radiogenic isotope ratios that change with time, like Rb/Sr or U/Pb, you find that many rocks with differnt ratios of many ages form a line, and the line traces back to an origin of 4.6 Ga as well.\n\nThe oldest life is 3 1/2 Ga, the oldest rock is about 4 Ga, and the oldest date ever found is on the highly durable mineral Zircon from Australia, it's date is 4.2 Ga. So, there is no direct method, it is based on inferences. However, many different inferences lead to the same number 4.559 Ga (to be specific).\n\nYou would have to throw out everything we know and love about Geology to accept a young earth view. When you look at the Grand Canyon, how can you say that only took 6000 years to form?
1092532
according to mr. wikipedia... the age of earth is... geologists have determined the age of the Earth to be around 4.55 billion years (4.55x109 years). This age represents a compromise between the oldest-known terrestrial minerals – small crystals of zircon from the Jack Hills of Western Australia – and astronomers' and planetologists' determinations of the age of the solar system based in part on radiometric age dating of meteorite material and lunar samples.\n\nThe radiometric age dating evidence from the zircons further confirms that the Earth is at least 4.404 billion years old. Comparing the mass and luminosity of the Sun to the multitudes of other stars, it appears that the solar system cannot be much older than those rocks. Ca-Al-rich inclusions – the oldest known solid constituents within meteorites which are formed within the solar system – are 4.567 billion years old, giving an age for the solar system and an upper limit for the age of the Earth. It is assumed that the accretion of the Earth began soon after the formation of the Ca-Al-rich inclusions and the meteorites. Since the accretion time of the Earth is not exactly known yet, and the predictions from different accretion models vary between several millions up to about 100 million years, the exact age of the Earth is difficult to define.\n\nIn the centuries preceding the scientific revolution, the age of the Earth was determined from the accounts of creation by religious authority. Today some religious groups continue to accept only theological accounts regarding the age of the earth, rejecting scientific evidence which contradicts their beliefs.\n\n\nHope this helps... ^^
221300
Measured by the decay of long-lived radioactive isotopes of elements that occur naturally in rocks and minerals and that decay with half lives of 700 million to more than 100 billion years to stable isotopes of other elements, scientists believe that the age of the earth is approximately 4.4 to 4.6 billion years old.
396602
4.5 billion years old maybe http://www.talkorigins.org/faqs/faq-age-of-earth.html
1118534
No.  The only way of confirming its accuracy is to date objects that we already know how old they are.  These fall into the scope of the last 5000 years, a period which they already say is less accurate than when measuring older objects.  Scientists always seem to be arguing about the age of things regardless of what the carbon dating says.
1104836
Precambrian for the Black Hills. That's anything from 542 million years (the start of the Cambrian) and back. The Rockies in Wyoming are Paleozoic to Mesozoic in age. If you want to know specifics then contact the USGS in Wyoming because they would be the people who would know the right answer. \n\nAnd for the record rocks aren't as old as the Earth because they are re-crystallized/partially melted to form new rocks. They are not the same rocks they were before and we pick up more sediments and minerals from cosmic bombardment.
194428
I assume you are using a half-life equation of the form:\nN(t) = N_0*e(-kt) where N(t) is the amount of radium remaining at time t and N_0 is the initial amount of radium. You should really provide this sort of information as the constant k is in no way universal (some people use r or lambda). Decay constant would be a more appropriate term.\n\nSo if the initial amount of radium is N_0 = 1 gram, then\nN(1622) = 0.5 grams(ie. there will only be a half a gram left after 1622 years). Take a natural log and solve for k.\n\nOnce you have k, for the second part let N_0 = 2.3 grams and solve for t where N(t) = 1.7 grams. You're going to need a natural log again for this guy, I trust you know how they work.\n\nAlso I'm pretty sure the previous answer is dead wrong.
829932
Take radium and subtract two from its atomic number. Then find the element with that result as its atomic number. I'm too lazy to see what that is right now.
372960
Well, it could be a date with Mick Jagger (from the Rolling Stones) or more likely it is using the various isotopes of elements found in a sample of stone to estimate its age. Say a stone was found with 50% of its original uranium in it. Uranium has a half life of 4.5 billion years so the stone would have passed one half life and would have an age of 4.5 billion years.  If only 25% of the original uranium were left, then 2 half lives or 9.0 billion years would have passed since the stone was created.