How do we know the age of the Earth? What methods are used?

Question

Any answers please before Wednesday.

Answer 1

For one thing, we can measure the ages of the oldest rocks by radioactivity dating. We know about how radioactive an igneous rock is when it first forms, so we can measure its current radioactivity and find its age. Some of the oldest rocks on Earth date back to over 3000000000 years old.

Another way is to look at the Moon. Since we know the Moon formed only a little after the Earth, we can also measure THOSE rocks, as well as looking at the number of craters on it, and tell about how old it is. Also, we can tell about the time the Moon separated from the Earth by looking at how far away it is; the forces moving it away from us can easily be calculated.

And those aren't the only ways. We can also look at the Sun and find out about how old it is, and we know the Earth formed just after the Sun did. Or we can look at the stages of metamorphosis certain rocks are in, to tell how long their chemical reactions have been going on. There are many ways of figuring out the approximate age of the Earth.

Answer 2

Several ways. Radiation from the oldest rocks gives a clue, but these are not the initial rocks that formed the earth - those are long gone. But the best indicator is measuring the age of these rocks, such as the ones found near the bottom of the grand canyon. The truth is no one really knows exactly how old the Earth is, but we can guess approximately how old it is, though the exact "time" it was formed is impossible to tell as it happened over a very long time.

There are a few other ways, such as measuring some astrological data, looking for the composition and the age of the rocks on the moon (these are original, have not been weather and eroded as ours have), looking at theories of the formation of the Universe and the probable time it would take to form the elements in our Earth and then for the Sun and planets to form, all of these point to about 5 billion years, though some calculations put it at 8 billion years, some at 4, they are all roughly in the same ball park and kind of agree. The only calculation that does not agree with this is the one extrapolated from the bible that makes the Earth 6000 years old - this is quite clearly wrong, and is based on guess work and inference, not the direct teachings of the bible (whether you choose to believe those fables or not).

Hope this helps with your homework.

Answer 3

he generally accepted age for the Earth and the rest of the solar system is about 4.55 billion years (plus or minus about 1%). This value is derived from several different lines of evidence.

Unfortunately, the age cannot be computed directly from material that is solely from the Earth. There is evidence that energy from the Earth's accumulation caused the surface to be molten. Further, the processes of erosion and crustal recycling have apparently destroyed all of the earliest surface.

The oldest rocks which have been found so far (on the Earth) date to about 3.8 to 3.9 billion years ago (by several radiometric dating methods). Some of these rocks are sedimentary, and include minerals which are themselves as old as 4.1 to 4.2 billion years. Rocks of this age are relatively rare, however rocks that are at least 3.5 billion years in age have been found on North America, Greenland, Australia, Africa, and Asia.

While these values do not compute an age for the Earth, they do establish a lower limit (the Earth must be at least as old as any formation on it). This lower limit is at least concordant with the independently derived figure of 4.55 billion years for the Earth's actual age.

The most direct means for calculating the Earth's age is a Pb/Pb isochron age, derived from samples of the Earth and meteorites. This involves measurement of three isotopes of lead (Pb-206, Pb-207, and either Pb-208 or Pb-204). A plot is constructed of Pb-206/Pb-204 versus Pb-207/Pb-204.

If the solar system formed from a common pool of matter, which was uniformly distributed in terms of Pb isotope ratios, then the initial plots for all objects from that pool of matter would fall on a single point.

Over time, the amounts of Pb-206 and Pb-207 will change in some samples, as these isotopes are decay end-products of uranium decay (U-238 decays to Pb-206, and U-235 decays to Pb-207). This causes the data points to separate from each other. The higher the uranium-to-lead ratio of a rock, the more the Pb-206/Pb-204 and Pb-207/Pb-204 values will change with time.

If the source of the solar system was also uniformly distributed with respect to uranium isotope ratios, then the data points will always fall on a single line. And from the slope of the line we can compute the amount of time which has passed since the pool of matter became separated into individual objects. See the Isochron Dating FAQ or Faure (1986, chapter 18) for technical detail.

A young-Earther would object to all of the "assumptions" listed above. However, the test for these assumptions is the plot of the data itself. The actual underlying assumption is that, if those requirements have not been met, there is no reason for the data points to fall on a line.

Answer 4

Uranium-lead dating. Carbon dating cannot be used to date the earth. This is how the age of the earth is calculated- through Uranium-Lead dating of rock samples brought back from the moon by Apollo astronauts. The moon is as old as the earth.

Answer 5

anyone saying carbon dating is wrong. that is only really useful in living (or dead) organisms. to measure the age of the earth first of all you need a meteor or similarly aged rock as these formed at about the same time the earth did. then you analyse the lead to uranium ration in said rock. uranium decays with a predictable rate into lead isotopes and by comparing the amount of lead to the amount of uranium you can get a rough estimate of the age of the earth.

Answer 6

Come on, that's so easy to answer. First of all there are specific formation from which we can "read" the age, and second of all, the age of nearly all matter on Earth can be determined by the so called caesium-half-life method.

Answer 7

Cut the top off a mountain and count the rings!

Answer 8

Carbon dating seems to be the latest 'in' thing

Answer 9

about 4.5 Bil years by carbon dating

Answer 10

prat count the candles