<p>Yes, the age of the Earth is about 4.5 billion years (4,500 million years). Your linked articles describes well <a href="https://earthscience.stackexchange.com/questions/4362/how-was-the-earth-formed?rq=1">how it was formed</a> and how we know about it. The uncertainty is less than 1% and depends partly on the radiometric dating methods and partly on the definitions. Sometimes the age is said to be 4.567 <a href="https://en.wikipedia.org/wiki/Billion_years" rel="noreferrer">Ga</a>, that might be a little too exact number to claim, but at least it's easy to remember. </p>

<p>I haven't heard any different age constraints that are scientifically founded, but before we had access to the methods and data we have today, there was a broader range of estimates. </p>

<p>Early estimates were based on the supposed <a href="http://apps.usd.edu/esci/creation/age/content/failed_scientific_clocks/ocean_salinity.html" rel="noreferrer">increased salinity of the oceans</a>, but those estimates fail to recognize that salt is also removed from the seawater in subduction zones and to form <a href="https://en.wikipedia.org/wiki/Evaporite" rel="noreferrer">evaporites</a>. </p>

<p>Noteworthy is <a href="https://en.wikipedia.org/wiki/William_Thomson,_1st_Baron_Kelvin#Age_of_the_Earth:_geology_and_theology" rel="noreferrer">Lord Kelvin's</a> very sensible estimate of 20–40 million years, published first in 1863. The estimate was based on the heat lost since formation and Earth's capacity to withhold its energy. Unfortunately, Lord Kelvin worked too early to know that $E=mc^2$, so energy is also generated within Earth and that is the main source of heat. He also didn't understand the Sun's <a href="http://onlinelibrary.wiley.com/doi/10.1029/2000JB900028/pdf" rel="noreferrer">source of energy and convection</a> and therefore miscalculated the solar age constraint and Earth's heat flux. </p>

<p><a href="https://australianmuseum.net.au/radioactive-dating" rel="noreferrer">Radioactive decay</a> is not only the source of heat but also the process we use to measure the age by radiometric methods. These methods became known decades later and quickly provided age constraints sin the right magnitude. </p>

<p>Earth scientists have assumed the deep time age of Earth since the antiques. It must have been frustrating for the early geologists to not be able to put a number of the Earth's age. As a rudiment of that time, we still use their <a href="https://en.wikipedia.org/wiki/Geologic_time_scale#Terminology" rel="noreferrer">relative terminology</a> to describe the development. </p>

<p>Our present estimate is based on a range of agreeing models and data. The Earth science community has, in general, moved on to new and more challenging questions. </p>

CC BY-SA 3.0
2017-07-13T07:09:20.983Z
Note: early British geologists (around Kelvin's era) were very well aware of the Earth being at least billions of years old. It were the physicists who denied it, due to a lack of a known process that would keep the Sun (nuclear fusion) and the Earth (nuclear fission) hot over such vast time scales. Of course, if you get a century or so earlier than that, you'd find plenty who were fine with the Earth being just 6000 years old, with all the surface features created by the biblical flooding. The British gained huge amounts of knowledge about the Earth while mapping their vast empire :)
Luaan
CC BY-SA 3.0
2017-07-13T07:45:51.840Z
Minor nitpick: The Earth stays warm due to radioactive decay (Mostly Potassium-40 beta decay and Uranium-238 alpha decay, from memory), plus a bit of core crystallization. There is/was a theory that enough uranium was concentrated at the Earth's core to form a natural fission reactor, but I'm not sure that it's taken very seriously.
Andrew Jon Dodds
CC BY-SA 3.0
2017-07-13T09:39:48.563Z
@Luaan I agree, the deep time of geology have been known for a long time. The Islamic scholars around year 1000, e.g. Ibn-Sinaa had a good idea about the stratigraphy and an age reaching far beyond history. There are also antique Chinese records that show an awareness of the true magnitude of Earth's age, e.g. from Mengxi Weng. As for competing estimates, as OP is interested in, I think they are mostly of dogmatic rather than scientific origin.
user2821
CC BY-SA 3.0
2017-07-13T10:30:14.070Z
@AndrewJonDodds Hah, yeah, I wasn't even suggesting a natural fission reactor, I did mean decay. My bad :)
Luaan
CC BY-SA 3.0
2017-07-13T14:38:14.150Z
It's interesting to line up two early estimates, based on ocean salinity increase and heat loss, that were reasonable based on uniformitarian assumptions, but ended up being way off due to important processes and events we weren't aware of. Makes you wonder what important processes and events we aren't aware of now, and how that could affect future estimates.
LarsH
CC BY-SA 3.0
2017-07-13T18:00:20.100Z
BTW, the book ["Oops! The 5 Greatest Scientific Blunders](https://www.livescience.com/32051-greatest-scientific-mistakes.html) lists Kelvin's estimate as one of them.
Barmar
CC BY-SA 3.0
2017-07-13T18:24:30.650Z
It's a common misconception that Lord Kelvin was wrong because he did not consider radioactive decay. Lord Kelvin was wrong because he did not consider mantle convection. [journal article](http://onlinelibrary.wiley.com/doi/10.1029/2000JB900028/pdf)
16807
CC BY-SA 3.0
2017-07-13T19:10:39.883Z
Patterson's 1956 paper "Age of meteorites and the earth" was the seminal paper which first dated the Earth, based on radioactive dating from meteorites. A free PDF copy of the paper can be found here: http://www.colorado.edu/geolsci/courses/GEOL5700-9/pdf/Fall07/Patterson.pdf. It might be nice to add a science paper reference or two for a definitive answer.
spacetyper
CC BY-SA 3.0
2017-07-13T20:23:13.317Z
I'm surprised no one has mentioned dating of zircon crystals, which is pretty reliable.
BillDOe
CC BY-SA 3.0
2017-07-14T00:55:04.153Z
@BillOertell and spacetyper:  Indeed it is good techniques and well worth discussing on this site! However, I understood OP's question as he /she is interested in competing age constraints, meteorites and zircon dating agrees well with the 4.5Ga age.
user2821
CC BY-SA 3.0
2017-07-14T00:59:47.900Z
@LarsH Yes. That is what makes science so interesting and important. It can't be enough stressed that 'scientific blunders' are not blunders if we learn from the experience and refine our methods. There are a few contradictions in present models that are still not resolved. The (proposed) existence of mantle plumes, the impact of tidal forces and the dynamics of the core are some example of debates that will bring our understanding of the Earth forward.
user2821
CC BY-SA 3.0
2017-07-14T01:07:28.897Z
@16807 Thanks for the edit and great article suggestion! It's very true and especially concerns the age of the Sun, that was supposed to be a constraint for Earth's age as well. Convection invalidated the whole assumption of a cooling ball, but they also needed a source of energy.
user2821
CC BY-SA 3.0
2017-07-12T23:45:56.203Z
2017-07-14T01:04:01.700Z
2017-07-14T01:04:01.700Z
user2821
<p>According to most <a href="https://www.space.com/24854-how-old-is-earth.html" rel="noreferrer">articles</a> I've read online, the estimated age of Earth is <em>4.5 billion years</em>.</p>

<p><strong>Question:</strong> How old is the Earth?</p>

<p>So I actually want to confirm that this is the case. Maybe there are other famous theories saying it is 3 billion years old or 6, therefore my question.</p>

CC BY-SA 3.0
2017-07-13T09:41:36.293Z
Related 1 [Newton's estimate of the age of the Earth](https://earthscience.stackexchange.com/q/4841/725) 2 [How do we know the asteroids formed at the same time as earth?](https://earthscience.stackexchange.com/q/2855/725) 3 [Why is Earth's age given by dating meteorites rather than its own rocks?](https://earthscience.stackexchange.com/q/2830/725)
That said, there are no other "famous" estimates. The ~4.5 Ga is well established using several independent methods (different isotopic systems).
Gimelist
CC BY-SA 3.0
2017-07-19T15:15:34.853Z
Define "age" do you mean when the mass formed, when it generated enough heat to liquefy, when the rocks cooled enough to be solid, ect?
John
<geology><earth-history><geochronology><dating><history-of-science>
How old is the Earth?
Kilise
# How old is the Earth?

(Asked by: username_0 on 2017-07-12)

According to most [articles](https://www.space.com/24854-how-old-is-earth.html) I've read online, the estimated age of Earth is *4.5 billion years*.

**Question:** How old is the Earth?

So I actually want to confirm that this is the case. Maybe there are other famous theories saying it is 3 billion years old or 6, therefore my question.

**Tags:** geology, earth-history, geochronology, dating, history-of-science

> **Comments:**
> **username_1**: Related 1 [Newton's estimate of the age of the Earth](https://earthscience.stackexchange.com/q/4841/725) 2 [How do we know the asteroids formed at the same time as earth?](https://earthscience.stackexchange.com/q/2855/725) 3 [Why is Earth's age given by dating meteorites rather than its own rocks?](https://earthscience.stackexchange.com/q/2830/725) That said, there are no other "famous" estimates. The ~4.5 Ga is well established using several independent methods (different isotopic systems).  
> **username_2**: Define "age" do you mean when the mass formed, when it generated enough heat to liquefy, when the rocks cooled enough to be solid, ect?  

---

## 1 answers

### Answer by username_3 on 2017-07-12. Score: 27 | Accepted answer

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](https://earthscience.stackexchange.com/questions/4362/how-was-the-earth-formed?rq=1) and how we know about it. The uncertainty is less than 1% and depends partly on the radiometric dating methods and partly on the definitions. Sometimes the age is said to be 4.567 [Ga](https://en.wikipedia.org/wiki/Billion_years), that might be a little too exact number to claim, but at least it's easy to remember.

I haven't heard any different age constraints that are scientifically founded, but before we had access to the methods and data we have today, there was a broader range of estimates.

Early estimates were based on the supposed [increased salinity of the oceans](http://apps.usd.edu/esci/creation/age/content/failed_scientific_clocks/ocean_salinity.html), but those estimates fail to recognize that salt is also removed from the seawater in subduction zones and to form [evaporites](https://en.wikipedia.org/wiki/Evaporite).

Noteworthy is [Lord Kelvin's](https://en.wikipedia.org/wiki/William_Thomson,_1st_Baron_Kelvin#Age_of_the_Earth:_geology_and_theology) very sensible estimate of 20–40 million years, published first in 1863. The estimate was based on the heat lost since formation and Earth's capacity to withhold its energy. Unfortunately, Lord Kelvin worked too early to know that $E=mc^2$, so energy is also generated within Earth and that is the main source of heat. He also didn't understand the Sun's [source of energy and convection](http://onlinelibrary.wiley.com/doi/10.1029/2000JB900028/pdf) and therefore miscalculated the solar age constraint and Earth's heat flux.

[Radioactive decay](https://australianmuseum.net.au/radioactive-dating) is not only the source of heat but also the process we use to measure the age by radiometric methods. These methods became known decades later and quickly provided age constraints sin the right magnitude.

Earth scientists have assumed the deep time age of Earth since the antiques. It must have been frustrating for the early geologists to not be able to put a number of the Earth's age. As a rudiment of that time, we still use their [relative terminology](https://en.wikipedia.org/wiki/Geologic_time_scale#Terminology) to describe the development.

Our present estimate is based on a range of agreeing models and data. The Earth science community has, in general, moved on to new and more challenging questions.

> **Comments:**
> **username_4**: Note: early British geologists (around Kelvin's era) were very well aware of the Earth being at least billions of years old. It were the physicists who denied it, due to a lack of a known process that would keep the Sun (nuclear fusion) and the Earth (nuclear fission) hot over such vast time scales. Of course, if you get a century or so earlier than that, you'd find plenty who were fine with the Earth being just 6000 years old, with all the surface features created by the biblical flooding. The British gained huge amounts of knowledge about the Earth while mapping their vast empire :)  
> **username_5**: Minor nitpick: The Earth stays warm due to radioactive decay (Mostly Potassium-40 beta decay and Uranium-238 alpha decay, from memory), plus a bit of core crystallization. There is/was a theory that enough uranium was concentrated at the Earth's core to form a natural fission reactor, but I'm not sure that it's taken very seriously.  
> **username_3**: @username_4 I agree, the deep time of geology have been known for a long time. The Islamic scholars around year 1000, e.g. Ibn-Sinaa had a good idea about the stratigraphy and an age reaching far beyond history. There are also antique Chinese records that show an awareness of the true magnitude of Earth's age, e.g. from Mengxi Weng. As for competing estimates, as OP is interested in, I think they are mostly of dogmatic rather than scientific origin.  
> **username_4**: @username_5 Hah, yeah, I wasn't even suggesting a natural fission reactor, I did mean decay. My bad :)  
> **username_6**: It's interesting to line up two early estimates, based on ocean salinity increase and heat loss, that were reasonable based on uniformitarian assumptions, but ended up being way off due to important processes and events we weren't aware of. Makes you wonder what important processes and events we aren't aware of now, and how that could affect future estimates.  
> **username_7**: BTW, the book ["Oops! The 5 Greatest Scientific Blunders](https://www.livescience.com/32051-greatest-scientific-mistakes.html) lists Kelvin's estimate as one of them.  
> **username_8**: It's a common misconception that Lord Kelvin was wrong because he did not consider radioactive decay. Lord Kelvin was wrong because he did not consider mantle convection. [journal article](http://onlinelibrary.wiley.com/doi/10.1029/2000JB900028/pdf)  
> **username_9**: Patterson's 1956 paper "Age of meteorites and the earth" was the seminal paper which first dated the Earth, based on radioactive dating from meteorites. A free PDF copy of the paper can be found here: http://www.colorado.edu/geolsci/courses/GEOL5700-9/pdf/Fall07/Patterson.pdf. It might be nice to add a science paper reference or two for a definitive answer.  
> **username_10**: I'm surprised no one has mentioned dating of zircon crystals, which is pretty reliable.  
> **username_3**: @BillOertell and username_9:  Indeed it is good techniques and well worth discussing on this site! However, I understood OP's question as he /she is interested in competing age constraints, meteorites and zircon dating agrees well with the 4.5Ga age.  
> **username_3**: @username_6 Yes. That is what makes science so interesting and important. It can't be enough stressed that 'scientific blunders' are not blunders if we learn from the experience and refine our methods. There are a few contradictions in present models that are still not resolved. The (proposed) existence of mantle plumes, the impact of tidal forces and the dynamics of the core are some example of debates that will bring our understanding of the Earth forward.  
> **username_3**: @username_8 Thanks for the edit and great article suggestion! It's very true and especially concerns the age of the Sun, that was supposed to be a constraint for Earth's age as well. Convection invalidated the whole assumption of a cooling ball, but they also needed a source of energy.  

---

