36 votes
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How do we know the asteroids formed at the same time as earth?

what evidence do we have that the asteroids indeed formed at the same time as earth? It depends on what is your definition as "the same time". The formation of the solar system and Earth did not ...
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27 votes
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How old is the Earth?

Yes, the age of the Earth is about 4.5 billion years (4,500 million years). Your linked articles describes well how it was formed and how we know about it. The uncertainty is less than 1% and depends ...
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  • 5,896
16 votes

How to determine how long ago a rock was broken?

There is a technique called "Exposure Dating". Using e.g. cosmogenic nuclides (they are produced in the first metre or so of the surface of a rock which is exposed to cosmic rays, i.e. on the surface ...
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12 votes

How do we know the asteroids formed at the same time as earth?

The formation of a T-Tauri star spells the beginning of the end of the protoplanetary disk from which planets and asteroids can form. The end is nigh when that star ignites. The large solar winds and ...
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12 votes
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How do scientists measure the age of old animal remains?

Organic material (plants and animals) contains carbon. Carbon has three main isotopes: carbon 12, 13 and 14. Carbon 14 is radioactive, with a half life of 5730 years. Carbon 14 is continuously ...
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11 votes
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Age of fossils found in rocks

Yes, there is some amount of circular reasoning in the statement: "geologist date rocks by the fossils they contain and date fossils by the rocks in which they are found". However, that statement ...
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11 votes
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Newton's estimate of the age of the Earth

The estimates of Newton and Kepler, and the similar estimates of dozens of their contemporaries, were produced by treating the Bible as a historically accurate document and deriving a chronology from ...
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  • 5,380
10 votes

How to determine how long ago a rock was broken?

Not as far as I am aware. Any dating of the rock would determine the formation age of the rock (dating isn't quite as straight forward as that, and there is a whole science behind what each dating ...
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  • 360
10 votes
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How to interpret the use of late and early Tertiary from older literature?

I think this is very hard to answer this question as it is exactly this ambiguity that caused the International Commission on Stratigraphy to discard the names Tertiary and Quaternary for there are no ...
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  • 2,602
10 votes
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Unwarranted claim of higher degree of accuracy in zircon geochronology

I can't be entirely sure but I'll make an informed guess: That value doesn't come for a single measurement. Therefore, if the error in the age of a single sample is $\pm125$ kyr, you just need to ...
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8 votes

What is the origin of the ocean's salt?

I'd like to add a bit to the existing answer and maybe break it down to several simple things: Chloride likes water. The chloride ion, Cl- really likes being in water. It's one of the most ...
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7 votes

Age of fossils found in rocks

In addition to what @Michael said, one can add that the claim that "geologist date rocks by the fossils they contain and date fossils by the rocks in which they are found" is misleading: are some ...
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  • 5,238
7 votes
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How do scientists determine the absolute or 'chronometric' date of fossils?

Biostratigraphy - observing which fossils were present in which stratigraphic units, and using minimally-deformed sequences to determine age order - gives us relative ages of fossils. Absolute ages, ...
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  • 2,826
6 votes

How do scientists determine the absolute or 'chronometric' date of fossils?

Typically this is accomplished through radiometric dating. While this is a complex field and the article I've provided a link for explains it better than I could here, the short answer is that ...
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6 votes

Nuclear testing and the Anthropocene, a chemostratigraphic link?

I will try to plainly answer your question about an artificial radionuclide production/diffusion resulting from human activities, without getting into the discussion of deciding if this is ...
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  • 2,623
6 votes
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Nuclear testing and the Anthropocene, a chemostratigraphic link?

Certain anthropogenic radionuclides have pragmatic advantages as markers for the start of the anthropocene. The advantage of radionuclides over anthropogenic stable nuclides is that the primordial ...
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  • 4,319
5 votes

Nuclear testing and the Anthropocene, a chemostratigraphic link?

The chapter on the Anthropocene (Zalasiewicz et al., 2012) of "The Geological Timescale 2012" quote 3 papers that used artificial radionucleotides as stratigraphic markers: Schwikowski (2004), ...
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  • 5,238
4 votes

How do we know the asteroids formed at the same time as earth?

The age of 4.55Ga for the Earth is actually a date of "hard stuff" based on Iron-Nickel meteorites, dated using radio-isotope dating. If you had enough meteorite samples it should be possible to ...
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3 votes
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Radiometric dating data sets

It sounds like there are two primary ones: No, these are not the two "primary ones". The method used depends on what you are dating, and what age you expect it to be. Radiocarbon dating is relevant ...
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3 votes
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Historically, how did the total amount of salt / NaCl on Earth develop?

Here is a graph describing modern estimates of ocean salinity throughout the Phanerozoic (past ~550 million years). The original PDF of this study can be found here: Hay, W.W., Migdisov, A., ...
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3 votes

Unwarranted claim of higher degree of accuracy in zircon geochronology

The uncertainty on the decay constant / half life is systematic. This means that, if the "used" value would be off the "true" value by 0.05%, then it would affect all the ages in ...
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  • 771
3 votes

Does water affect radiometric dating?

No, not really. In simple terms, to be soluble in water, Pb must be in contact with it. But most of Pb is stored within the Zircon lattice, where water cannot diffuse through. For example, many ...
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2 votes

Newton's & Kepler's age of the earth calculations - References?

Your question may be better suited to either SE History or SE History of Science and Mathematics. The date of the so called creation of the Earth has nothing to do with Earth Science. For Kepler I ...
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2 votes

Relative dating of granite pluton

What exactly are you trying to measure? some of the great North American and Andean batholiths have cooling histories of at least 20 million years, and maybe more than 50 million years. It is perhaps ...
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2 votes

Would you see a correlation between detrital zircon age and grain shape?

My thought is that you would not see any correlation because grain roundness has to do with how long it has been in the sedimentary system rather than its crystallisation age. That is, if one sampled ...
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  • 316
2 votes
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Is astrochronology a proper method?

Yes it is used and it works. I've heard varying viewpoints on it's accuracy and dependability though. I remember my earth science lecturers were in three camps with it: one felt that the dates weren'...
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  • 4,227
1 vote

Radiometric dating data sets

There are huge datasets of geochronology available in the published literature. Unfortunately there is not one single database because the task is daunting (there are several thousand geochronology ...
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