How Old is the Earth?

[Bread_of_Life]

Radiometric Dating

The Nucleus

Matter is made out of small units called atoms. Atoms have a nucleus in the centre - which is heavy and made out of sub atomic particles named "nucleons". Positive protons and neutral neutrons are examples of nucleons. Shells of electrons, which are negative, spin round the nucleus at very high speed in orbits.

The nucleus determines the nature of a substance - the number of protons determines what element a substance is, for example. The nucleus is also where radioactive decay happens. You see, protons actually repel each other electromagnetically - positive repels positive - driving the nucleus apart. However, the neutrons and protons attract each other, with a force called "the strong force", keeping the nucleus together.

Radioactive Decay

However, if the mix of protons and neutrons is wrong - or there are too many of each - the nucleus becomes unstable, because the forces arn't balanced right. That means that certain nuclei become unstable - and can even collapse and split apart. This is called radioactive decay.

There are 3 types of decay:

Alpha decay: This is when an "alpha particle" (made up of 2 neutrons and 2 protons) is ejected from the nucleus. This is especially common in heavy nuclei, that need to get rid of nucleons fast to become stable.

Beta decay: This is when a neutron turns into a proton and an electron - or a proton turns into a neutron and a positron (a positive electron). This occurs normally when the balance of neutrons and protons isn't right.

Gamma decay: This is a special type of decay some of the excess mass of the nucleus is converted into energy, and given off as a burst of gamma radiation (a type of very very high energy invisible light).

Half life

The physics behind radioactivity is well researched - there is even a formula where you plug in the number of protons and neutrons and it'll tell you if the atom is radioactive. There are also formulae to work out how quickly atoms will decay on average. Of course, it is an average, because decay is a probabilistic/statistical process - but experimentally you'll find that decay rate is very very close to the average, because there are so many atoms making up the sample. Kindof like if the average height of men is 6 feet, if you take 2 men they might not have a 6 foot average - but if you take a million men, then it's likely to be close to the average. There are literally billions of atoms in a tiny spec of matter - meaning that radioactive decay follows the average pretty closely.

If we know how quickly atoms will decay on average, then we can tell how much will have decayed after a certain ammount of time. We have a very useful measure, called the "half life", which is the ammount of time it takes for 50% of a radioactive material to have decayed. In other words - if you have 1 kg of a substance with a half life of a year - if you wait a year, 500g of radioactive substance will be left.

Decay Series

Now, what happens when an atom decays radioactively? Well, it turns into a different substance - because it'll have a different number of neutrons and protons left. This new substance is called the "daughter" of the decay (because it is literally born of the decay), and the radioactive element is called the "parent".

Sometimes though, when a parent decays, it decays into a daughter that is also radioactive! Then the daughter decays, giving birth to another daughter, which might also be radioactive. This can create a chain of radioactive parents and daughters, all the way down finally to a daughter that isn't radioactive, and then the chain stops. This happens often when the original parent is very heavy, like in the decay of Uranium.

At first, as the original parent starts to decay forming a chain, the chain grows. After a while (a few million years with Uranium) the chain settles down to a steady state. These decay chains can therefore be used to date rocks up to a few million years as the chain grows - but in older rocks, they can assure us that the rock is *at least* a few million years old, but they can't tell us exactly how old.

Radiometric Dating

Now, the half life of radioactive elements depends on the nuclear properties of the element. That means that it won't change over time - and since the nucleus is almost completely immune to high temperature and pressure - we know that even under very very extreme conditions the half life won't change that much.

Now, as rocks form inside the earth, and in lava flows, they often contain radioactive elements. And when they solidify, those elements decay inside the rock, and the daughter products are stuck within the confines of the rock. That means that millions of years later, we can pick up the rock, measure the proportion of daughter and parent elements, and estimate how old the rock is, using various methods.

Below I'll tell you about the various methods of dating rocks using radioactive material - and why we're sure they're accurate.

Types of Radioactive Decay

Uranium Dating

Uranium decays to lead, through a rather long decay series. That means that firstly, because of decay series, we often know for absolute sure that the rock is at least a few million years old (after all, what's the chances that exactly the right ammounts of each daughter element in the series existed in the rock out of chance?)

Despite the reassurance of decay series, Uranium is still the crudest dating method - and the simplest. You take the ammount of Uranium, the ammount of lead, estimate how much lead was in the rock in the first place as it was formed (so that you don't count that lead as daughter element), and plug it all into a formula to get a date out the other end.

Now, clearly there is a source of error in this form of radiometric dating. What if you estimate the ammount of lead originally in the rock wrongly, and are counting too much or too little "daughter" lead? Also, what if some daughter or parent has been added or leaked away? Well, these are valid sources of error, and hence this form of dating is less accurate than others. However, of course, this is a random source of error, and given enough samples, it ought to average itself out.

Potassium-Argon Dating

This type is known as K-Ar dating (K and Ar being the letters representing Potassium and Argon in the periodic table). Now, his method of dating is very interesting for two reasons.

Firstly, Argon, the daughter element, is a rare inert (unreactive) gas - which means that it usually boils off and bubbles off into the atmosphere when a rock or crystal is formed. That means that we can be fairly sure that the original level of Argon was very very low in the rock.

Secondly, this type of decay takes place in crystals. That means that if the crystal has been disturbed, or cracked, or tampered with, it is fairly easy to see from it's structure - and also, all of the daughter argon is trapped in the crystal lattice, it cannot escape.

That means that K-Ar dating is much more accurate than Uranium dating - yielding error margins as low as 1-2% in some cases.

Rubidium Strontium Dating

This type of dating is without doubt the most accurate - and the most interesting. It's also the most complicated mathematically - so you'll have to forgive me for skipping over and simplifying the maths. It can only date old rocks though, at least over 10 million years old - because Rubidium has a very long half life (47 billion years!)

There are several different types of Strontium - only one type is created through Rubidium radioactive decay. However, we also find the other types of Strontium in rocks - but we also know that the naturally occuring ratio of these different types of Strontium is constant at any one time on earth.

That means, with a bit of mathematics, we can come out with a straight line graph, (called an isochron, for enthusiasts), whose gradient is the age of the rock http://www.astro.lsa.umich.edu/users/cowley/rbsr.html . But get this - if any part of the rock is tampered with, it won't be a straight line. If the rock has partially melted and resolidified, we won't come out with a straight line.

Basically, the results of this type of dating allow us to check all our assumptions that we wern't able to check with Uranium dating. We can know exactly how much Rubidium there was to start with. We can know if the rock has been tampered with. We can know if any daughter or parent element has been lost or added to any part of the rock. In other words, this method is self checking, and self calibrating - it's the perfect method of telling time - and often yields errors as low as 1%.

If you ever hear scientists say that a rock is "unsuitable" for radiometric dating - chances are that they've tested it using Rb-St - and found that they didn't get a straight line, meaning that the rock has been tampered with and it's impossible to use it for dating. Unfortunately, creationists often twist this to an unwary public - and say that scientists throw away bad results and blame it on the rocks being unsuitable. Nothing could be further from the truth of course - in actual fact, it's because this dating method is so good that we can tell from it if our assumptions are correct, and therefore if a rock is suitable.

Dating Using Several Methods

We scientists arn't very often satisfied with one result. That's why we often date several rocks from any one site, and use as many methods of dating as possible to check. For example, the oldest rocks ever found date at about 4.2 billion years - and these were checked with all three methods of dating, all of which agreed to within bounds or error.

Final Quirky Little Proof of an Old Earth

I can't remember who came up with this one, but it's very interesting. There are many radioactive elements that we know about. Some occur naturally all the time - some do not generate naturally.

Of those that do not generate naturally, some have a half life of over 50 million years, and some do not. We find traces of every single one of the ones with a half life over 50 million years, and absolutely no trace at all of any of the ones with a half life below 50 million years.

Only the earth being many times old than 50 million years can explain how why we only find elements with long half lives - because the elements with low half lives have all decayed to nothing.

ps. When I get the time, I'll type up a full and detailed post on Rubidium-Strontium dating, and on isochrons, and how they allow us to test all our assumptions in radiometric dating.

[nebula]

However, the neutrons and protons attract each other, with a force called "the strong force", keeping the nucleus together.

OK, while I have the chance -

Just so you know, I am a science major -

What exactly is "the strong force"?

I've heard of it, but can't make sense of it.

(P.S. physics isn't my strong point.)

[Guest yod]

I don't subscribe to the "new earth" theory anyway.

I completely believe the biblical account though....

The word translated as day is "yom".

this word can also be translated at "epoch" or "age"

I believe we are still in the Sabbath "yom"

[Bread_of_Life]

What exactly is "the strong force"?

The strong force is one of 3 fundamental forces between particles. There is the gravitational force between massive particles (this is the weakest), the newly unified electro-weak force (between charged particles), and the strong force (between certain fermions, like neutrons and protons).

Essentially, the strong force is stronger than the electroweak force, so whereas the protons in a nucleus should repel each other and break apart the atom, the strong force acts to hold it together. However, if you have the wrong balance of neutrons and protons in an atom, it'll disintegrate (only certain combinations of neutron and proton numbers are stable between all the forces).

Radioactive elements are semi-stable, they're on the borderline of stability. Radioactive decay can be seen as a way for a borderline stability nucleus to become more stable by rectifying the ratio of neutrons and protons to a more stable configuration.

Just so you know, I am a science major

I'm not sure what that is, because I live in England, however I would guess that this is our equivalent of a degree course? I am a physics graduate, with an amateur interest in biology and evolution. Therefore this is really my forte.

The word translated as day is "yom".

this word can also be translated at "epoch" or "age"

How would you therefore explain that the fossil record is in a different order than the order of creation in genesis 1?

[Guest yod]

How would you therefore explain that the fossil record is in a different order than the order of creation in genesis 1?

in the book "Fingerprint of God" by astrophysicist Hugh Ross, he points out that the account given by Moses in the book of Genesis is EXACTLY the same order as he was taught as an atheist going through school.

And he gives a 40 million to one chance of that happening.

Have you ever read it? Why bother arguing with us ignorant peons?

Go to a scientist who has knowledge in this area and can credibly defend christian claims.

[Bread_of_Life]

in the book "Fingerprint of God" by astrophysicist Hugh Ross, he points out that the account given by Moses in the book of Genesis is EXACTLY the same order as he was taught as an atheist going through school.

Then Hugh Ross is incorrect, but that isn't surprising considering that he is an astrophysicist, and we're talking about biology.

Here is the order of creation in genesis:

God creates heavan and earth

God creates light.

God creates water.

God creates land.

God creates grass, herbs and trees.

God creates 2 lights in the sky (the sun and moon)

God creates fish, birds and whales

God creates livestock, creatures that move along the ground, and wild animals, and man

God then creates women.

Here is the order of the fossil record (and cosmology in general)

Sun is formed

Earth forms

Moon forms from collision of two protoplanets (moon is a mirror btw, not smaller light)

Seas form

Bacteria and protozoa evolve

Plants and Animals differentiate

Multicellular animals and plants evolve

Jawless Fish and Placoderms evolve

Cartilage and Bony fish evolve

Land is colonised by amphibians

Trees evolve

Reptiles evolve.

Mammals and birds evolve.

Whales evolve.

Man evolves.

As you can see, the two don't match up. For example:

1. In Genesis, the earth is formed before the Sun and Moon.

2. In Genesis, the Sun is formed after light

3. In Genesis, the moon is describes as a second light, rather than a mirror.

4. In Genesis, trees form before marine life.

5. In Genesis, plants form before the Sun does.

6. In the fossil record, birds (120MY) and whales (60MY) appear nearer the end (birds before whales) - whereas in Genesis the form at the same time as fish, and before the creatures they evolved from (also, whales are mammals, which according to Genesis are created the next day

7. In Genesis, wild animals, ground creatures and livestock all form simultaneous, whereas in the fossil record they are very much seperated to a variety of locations (ground creatures appearing just after fish for example).

8. In Genesis 2 (the second creation account) man and woman are created one after another, whereas the scientific evidence points to the sexes co-evolving.

As you can see, it should have been quite simple for Hugh Ross to compare and contrast the different accounts, to find out that they do not match up very well at all. Even a very cursory knowledge of the fossil record should have told him that the order of Genesis was in conflict with general revelation.

Go to a scientist who has knowledge in this area and can credibly defend christian claims.

I am yet to meet a scientist who claims that the order of the fossil record is not in conflict with the order of creation in Genesis, sorry.

[other one]

If you read much on the research being done with the string theory you can get a sense of just how much we don't know of the universe and how it was made and how old it really is.

There appears to be at least 10 deminsions is space - time and we can only work with it mathmatically for it is not within our senses to perceive how the other's look. We can only see how they work together.

Those who are working in the area are saying that we may have to rethink just about everything.

I think God probably did us a big favor by giving us a quick overview of how he made everything, for our most advanced people admit at the present time we could only reply....... Hugh..... what......Huummmmmmmm

Sixty percent of the makeup of things we can not comprehend at the present time, so don't give me that story of how old the universe is and that we just happened out of some soup and evolved into what we are today. Even in 6 billion years, to me, it takes more faith to believe that. Every primace of science is taken on faith, just because the speed of light seems constant today doesn't mean it has always been that way. Some are questioning that today, and if light is slowing down as they believe, time will be slowing down too.

For all we know the time difference from Genesis 1:1 to 1:2 may have been only .2 microseconds that could be 5 billiion years in todays time flow.

There is just too much to speculate about in this field.

Someday, I'll ask Him how he did all this and maybe with our new bodies and upgreded brains, I'll be able to understand. If not........ what does it really matter?

[other one]

http://www.pbs.org/wgbh/nova/elegant/

PBS did an interesting thing with NOVA. It is interesting to look through if you have not been exposed to these things. Like most things in this field it leaves more questions than it answers, but that's what science has always done for we don't understand it all. Those who think they understand it all, have simply quit looking.

SE

[Adoni~Is~Alive~4~Ever]

Sun is formed

Earth forms

Moon forms from collision of two protoplanets (moon is a mirror btw, not smaller light)

Seas form

Bacteria and protozoa evolve

Plants and Animals differentiate

Multicellular animals and plants evolve

Jawless Fish and Placoderms evolve

Cartilage and Bony fish evolve

Land is colonised by amphibians

Trees evolve

Reptiles evolve.

Mammals and birds evolve.

Whales evolve.

Man evolves.

Nik, could not that ""sun"" be light blazzing from heaven?

ok so the earth is formed.

also God is the light of this world

ok the next thing is water... that fits right in.

ok... how could they know if Bacteria and protozoa evolve,

there is no humans or animals for it to be tested upon.

ok so plants, that fits.

much more to come buddy!

gotta clean the house for grandpa and my great aunt!

love always,

rhebekka

[Bread_of_Life]

. It is interesting to look through if you have not been exposed to these things.

As a graduate in Physics from Imperial College, London - I have been exposed to almost all of these things at some level or another. Not that I claim to be an expert in string theory of course, nor in dimensional analysis. However, I can safely say that from what I have seen, neither puts the age of the earth of universe in any doubt at all.

Like most things in this field it leaves more questions than it answers, but that's what science has always done for we don't understand it all.

Science is a field of reductionism. The deeper we go and simpler we go, the more there is to find out. However, the fact that we do not know everything, and that we do not know the next stage down in the construction of matter, does not mean that we cannot be certain of basic facts and empirical data.

At the moment, every single piece of empirical data we have to hand points to the earth being 5 - 5.5 billion years old, and life being 3.7 billion years old. There is no debate in the scientific community concerning these assertions, because every single piece of evidence points to them, and every single prediction made by these theories has come true. Now, you can cling onto the vague hope that one day you will be able to explain away the mountains of data we have collected in the realm of paleontology, geology and physics - but it won't be science, it'll be blind faith - faith in a particular interpretation of a particular religion - an

interpretation that has been proven wrong time and time again.

Sixty percent of the makeup of things we can not comprehend at the present time,

60%? Did you just make this number up? Sounds awfully low to me, I'd guess that there's a lot more about the universe that we don't know than that. After all, it's a big place.

Every primace of science is taken on faith,

Incorrect, they are taken on evidence. Scientists proportion their belief to this evidence, and form theories to try and explain it.

For all we know the time difference from Genesis 1:1 to 1:2 may have been only .2 microseconds that could be 5 billiion years in todays time flow.

That may be (although, like the matrix, leprechauns and tooth fairies there is no evidence at all to say it is so), however given that it is, that leaves us with the questions of:

why are the fossils in the fossil record in chronological order?

why are the rocks in strata in chronological order?

why are there fossils at all, given that they can only have lived .2 microseconds?

why are there surface features in the geological strata?

why is the grand canyon in equilibrium?

why didn't all the heat from the radioactive decay vaporise the earth?

and many many more.