How old is the Earth?

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I can’t believe we still have to cover this. We know how old the Earth is. The science on this is pretty darn good. It is 4.54 billion years old plus or minus about 1%.

Florida Senator Marco Rubio does not know how old the earth is. Here is what he says about it:

I’m not a scientist, man. I can tell you what recorded history says, I can tell you what the Bible says, but I think that’s a dispute amongst theologians and I think it has nothing to do with the gross domestic product or economic growth of the United States. I think the age of the universe has zero to do with how our economy is going to grow. I’m not a scientist. I don’t think I’m qualified to answer a question like that. At the end of the day, I think there are multiple theories out there on how the universe was created and I think this is a country where people should have the opportunity to teach them all. I think parents should be able to teach their kids what their faith says, what science says. Whether the Earth was created in 7 days, or 7 actual eras, I’m not sure we’ll ever be able to answer that. It’s one of the great mysteries.

Phil Plait has responded with this:

Actually, it’s not a great mystery. It used to be … a century ago. I am a scientist, and I can tell you that nowadays—thanks to science—we know the age to amazing accuracy. The age of the Earth is 4.54 billion years … plus or minus 50 million years. That’s a number known to an accuracy of 99 percent, which is pretty dang good.

Sen. Rubio’s answer, however, is so confused and error-riddled its difficult to know where to start.

And then, Phil goes ahead and addresses that, HERE.

The Maddow Blog also addresses Senator Rubio’s miscarriage of intelligence.

And, the thing is, the actual story about how we know about the age of the earth is not only well established science, but it is intrinsically interesting. Following is from a post I wrote about this a while back, slightly edited:

How old is the earth?

Short answer: 4,540,000,000 Earth-years, plus or minus 1%.

Long answer: We don’t know exactly because direct dating of the earliest material on the surface of the Earth will only tell use a minimum age; Prior to that, the Earth’s surface was probably molten, and even after that, it may be that the earliest non-molten material has been recycled into the planet’s interior by tectonic processes. Also, the earth is a big round ball of stuff that condensed into this shape from part of a large disk-shaped blob of stuff known as the Solar Nebula. When exactly, given this, did the Earth become the Earth? Since the process took millions of years, we can’t pinpoint the age of the Earth more exactly than a certain range.

What are the oldest rocks?

The oldest rock formations on Earth are between about 3.8 and 3.9 billion years old., but there are older bits of more ancient rocks that were incorporated into these early rocks, and they date to something closer to 4.4 billion years old. These and other early materials are dated primarily using a variety of parent-daughter radiometric techniques, with the most effective for this time period being a lead-lead system.

Since rock from the time of the Earth’s formation isn’t available (because it didn’t really exist or was gobbled up in the fiery beginnings of the big round ball) the preferred method of dating the Earth is to calculate the age of meteorites. The earliest meteorites essentially date the condensation of materials in the solar system into the planets, and thus, the date of these meteorites indicates the date of the early Earth. (The Earth existed prior to this condensation in the form of whatever parts of the early solar nebula would eventually condense into this particular planet, of course.)

Meteorites from other planets?

Some meteorites are known to be fragments of Mars, so the oldest dates among these can also verify the date of accretion of material into planets in our solar system.

Rocks from the moon have not been remelted or otherwise messed up by tectonic processes and therefore would provide an excellent estimate of the age of the Earth as well. Also, since there is no real weathering of rocks on the moon, methods other than parent-daughter decay can be used, such as Fission Track dating (the older a rock, the more cosmic rays pass through it, blasting tiny little tracks in the otherwise homogeneous matrix).

Zeroing in on the age of the earth

There are hundreds of published dates of various older materials, but the following table gives a reasonable summary of some of the more important dates, culled from various sources (see list of references below):


If we chart this on a graph, we see one date that is much earlier than all the other dates, and a few that are younger.


The younger dates are simply of materials that we don’t think date the Earth’s formation, but that we know would post date it by not much. These dates verify the earlier cluster of dates that would correspond to the actual formation of the planet. The single earlier date is an obvious outlier.

Taking this series of dates, notice that the oldest (non-outlier) dates are about four and a half billion years old. As stated in the short answer.

Further information about the age of the Earth:

Dalrymple, G. Brent. 2001. The age of the Earth in the twentieth century: a problem (mostly) solved. Geological Society, London, Special Publications 2001, v. 190, p. 205-221. Click Here.

Dalrymple, G. Brent. 2006. How Old is the Earth: A Response to “Scientific” Creationism. The TalkOrigins Archive. Click Here.

Norman, M. D., Borg, L. E., Nyquist, L. E., and Bogard, D. D. (2003) Chronology, geochemistry, and petrology of a ferroan noritic anorthosite clast from Descartes breccia 67215: Clues to the age, origin, structure, and impact history of the lunar crust. Meteoritics and Planetary Science, vol 38, p. 645-661.

Stassen, Chris. 2005. The Age of the Earth. The TalkOrigins Archive. Click here.

Wikipedia, Teh. 2010. Age of the Earth. Click here.

So there you go.

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21 thoughts on “How old is the Earth?

  1. For someone like Rubio, the problem of the age of the Earth is complicated by the need to factor in the estimated number of voters who will be pissed off by his answer.

  2. The senators comments were disingenuous but hardly incorrect!

    He merely said, if I may be allowed to paraphrase a bit, “I don’t want to answer “4.5 billion years” because my religious constituents would abandon me, but maybe they can be introduced to the truth if we frame it as seven ages that total to 4.5 billion instead of seven days…after all, who knows how long a gods’ day is in human terms?”

    We KNOW what the science answer is, we just have to allow the senator an attempt to keep peace with the ignorant, outdated bible thumpers in the wing of his party.

  3. Both John and SNO are correct. If my politician answers 4.5 bilions years, he will definitely lose my vote – especially if he says he is a Christian and still espouses the modern science belief in an old earth and evolution.

    Both of you are correct that the Republican base would abandon a candidate who believes in dribble drabble like that. He cetain would lose some of my support and all of it if a third party candidate with veiews similar to my own were running.

    If the Republicrats are smart and want our money to run their campaigns they know better than to go all liberal sciencey mish mash on us. We’ll pull their funding faster than lightening can strike a metal pole a mile high. They better either comply, or get fired. That simple.

  4. Yes. Reality is a liberal conspiracy.

    Did you know pretty much all tech companies are liberal run?
    That’s probably a conspiracy too.
    Better abandon all electronics quick!

  5. Yes, Rubio has political reasons for not giving the scientifically correct answer. However, we are in “Opinions Differ Regarding Shape of Earth” territory here.

    Boasting of precision may not be the best tactical move here: Archbishop Ussher named a specific hour on a specific day in 4004 BC. If I’ve done the arithmetic right, that’s an uncertainty on the order of a part per billion. Of course, Abp. Ussher’s estimate is one of my favorite illustrations of the difference between precision and accuracy.

  6. Rubio’s answer was essentially the same as one given by Barack Obama several years ago. Maybe someone can supply some links to the blogs and news reports taking him to task for it, I can’t seem to find any.

    If Rubio had answered 3.5 billion (which for some reason was the number stuck in my mind) he would be pilloried for muffing the answer. Nyah Nyah, Rubio was off by a billion years.

    Does anybody here posess epistimological certitude that in 20 years we’ll be told that “The science on this is pretty darn good. It is [whatever number, but something significantly different than 4.54 years].”?

  7. Yes, that certitude is pretty much in place! It isn’t the case that all scientific facts remain equally uncertain for their lifespan. They generally get more and more certain over time. The estimate of the age of the earth is not going to change much at all; at this point it is a matter of definition not dating: Do you want to “date” the earth at the first point where the mass of stuff roughly equals the current Earth + Moon, or do you want it to be when it reaches a fiery melty bally thing, or do you want it to be when you can stand on it and have your feet be only uncomfortably warm?

  8. Rubio has a history of favoring Creationism, and is very wrong on his claim that there are other, equally valid age estimates, specifically of about 6,000 years. He is promoting anti-science and ignorance, hardly something that a member of the senate science committee should be doing. I have to agree with paul Krugman, who says if a policymaker believes in the magic of Creationism, we might expect him to believe in magical economic faiths such as “trickle-down” and the “confidence fairy.”

  9. What a goofy post. Why are people asking politicians science questions? It’s as though this post is trying to have a ‘gotcha’ moment with Rubio and there is nothing here.

    If you wanted to write about how old the earth is, just do it. You know need to include a politicians comments on it.

  10. Matt, actually, this post is all about how we know how old the Earth is. I just did it! The political reference makes a good point, the very same point you make in your comment.

  11. I feel that it is important to point out that the Bible does not make the claim that the earth is 6,000 years old. It actually says that the earth is ancient in the extreme and existed long before God said, “Let there be light” coincidentally meaning that time/history did not begin at the point but somewhere long before that.

    Genesis 1:2

  12. There is so much evidence that the world is only thousands of years old. Ex) Scientists have found dinosaur fossils with living tissue in them. If the Earth was billions of years old, don’t you think that those fossils would be completely dried up? Of course. And God definitely created the world. Think of all the systems in everything all the very fine details. How a plant can use water and sunlight to makes its own food to sustain itself. Of all the working systems in our body. Our complex brains and how they work. How the moon has its different phases throughout the year. How a starfish can regrow its limbs. How the seasons change and the weather is different. The trees change their leaves colors. And so much more. Something random could NOT have just, happened. Someone had to create everything: God. Plain and simple.

  13. Genesis 1New International Version (NIV)

    The Beginning
    1 In the beginning God created the heavens and the earth. 2 Now the earth was formless and empty, darkness was over the surface of the deep, and the Spirit of God was hovering over the waters.

    3 And God said, “Let there be light,” and there was light. 4 God saw that the light was good, and he separated the light from the darkness. 5 God called the light “day,” and the darkness he called “night.” And there was evening, and there was morning—the first day.

    6 And God said, “Let there be a vault between the waters to separate water from water.” 7 So God made the vault and separated the water under the vault from the water above it. And it was so. 8 God called the vault “sky.” And there was evening, and there was morning—the second day.

    9 And God said, “Let the water under the sky be gathered to one place, and let dry ground appear.” And it was so. 10 God called the dry ground “land,” and the gathered waters he called “seas.” And God saw that it was good.

    11 Then God said, “Let the land produce vegetation: seed-bearing plants and trees on the land that bear fruit with seed in it, according to their various kinds.” And it was so. 12 The land produced vegetation: plants bearing seed according to their kinds and trees bearing fruit with seed in it according to their kinds. And God saw that it was good. 13 And there was evening, and there was morning—the third day.

    14 And God said, “Let there be lights in the vault of the sky to separate the day from the night, and let them serve as signs to mark sacred times, and days and years, 15 and let them be lights in the vault of the sky to give light on the earth.” And it was so. 16 God made two great lights—the greater light to govern the day and the lesser light to govern the night. He also made the stars. 17 God set them in the vault of the sky to give light on the earth, 18 to govern the day and the night, and to separate light from darkness. And God saw that it was good. 19 And there was evening, and there was morning—the fourth day.

    20 And God said, “Let the water teem with living creatures, and let birds fly above the earth across the vault of the sky.” 21 So God created the great creatures of the sea and every living thing with which the water teems and that moves about in it, according to their kinds, and every winged bird according to its kind. And God saw that it was good. 22 God blessed them and said, “Be fruitful and increase in number and fill the water in the seas, and let the birds increase on the earth.” 23 And there was evening, and there was morning—the fifth day.

    24 And God said, “Let the land produce living creatures according to their kinds: the livestock, the creatures that move along the ground, and the wild animals, each according to its kind.” And it was so. 25 God made the wild animals according to their kinds, the livestock according to their kinds, and all the creatures that move along the ground according to their kinds. And God saw that it was good.

    26 Then God said, “Let us make mankind in our image, in our likeness, so that they may rule over the fish in the sea and the birds in the sky, over the livestock and all the wild animals,[a] and over all the creatures that move along the ground.”

    27 So God created mankind in his own image,
    in the image of God he created them;
    male and female he created them.
    28 God blessed them and said to them, “Be fruitful and increase in number; fill the earth and subdue it. Rule over the fish in the sea and the birds in the sky and over every living creature that moves on the ground.”

    29 Then God said, “I give you every seed-bearing plant on the face of the whole earth and every tree that has fruit with seed in it. They will be yours for food. 30 And to all the beasts of the earth and all the birds in the sky and all the creatures that move along the ground—everything that has the breath of life in it—I give every green plant for food.” And it was so.

    31 God saw all that he had made, and it was very good. And there was evening, and there was morning—the sixth day.

  14. Please don’t.

    99+% of christians are slapping their foreheads at your idiocy.

    1) There’s no evidence other than hearsay from an event nobody was at, where even the record of the telling of the story of the event is itself an event nobody in recorded history has ever been at and admitted it.

    2) The evidence for an earth billions of years old is gargantuan, so much so that there are only a very few denominations of christianity that have as a part of their faith that this evidence is wrong.

    So, please, for the sake of the majority of christians, stop being such a dumbass in public. You’re shaming them for using the word “Christian” to describe themselves.

  15. “31 God saw all that he had made, and it was very good. ”

    You DO realise you’ve just proven I’m god, right?

    After all, look out the window. See all that stuff? Could it have made itself in all its perfection? I MADE IT ALL. That’s why it looks designed to all fit together! I made it!

  16. Augustine of Hippo wrote:

    “It not infrequently happens that something about the earth, about the sky, about other elements of this world, about the motion and rotation or even the magnitude and distances of the stars, about definite eclipses of the sun and moon, about the passage of years and seasons, about the nature of animals, of fruits, of stones, and of other such things, may be known with the greatest certainty by reasoning or by experience, even by one who is not a Christian. It is too disgraceful and ruinous, though, and greatly to be avoided, that he [the non-Christian] should hear a Christian speaking so idiotically on these matters, and as if in accord with Christian writings, that he might say that he could scarcely keep from laughing when he saw how totally in error they are. In view of this and in keeping it in mind constantly while dealing with the book of Genesis, I have, insofar as I was able, explained in detail and set forth for consideration the meanings of obscure passages, taking care not to affirm rashly some one meaning to the prejudice of another and perhaps better explanation” (The Literal Interpretation of Genesis 1:19–20 [A.D. 408]). 

    Nuff said

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