How old are the atoms that make up my body?

[bostonnew]

Hi all,

Can someone tell me how old are the atoms my body is made off? In other words, how old am I really?

THANKS

 

[Dadface]

Hello bostnnew.Perhaps some of your atoms existed at the beginning of time.

 

[bostonnew]

So I'm 13.75 billion years old? Although I've only been conscious for 28 years?

 

[pallidin]

So I'm 13.75 billion years old? Although I've only been conscious for 28 years?

Yeah, the atoms in your body ARE that old, more or less, but what you think of as "YOU" is not. The collective atoms which formed your body(as a collection) did not occur that long ago. Only 28 years.

Another way to look at this is, say, my newer computer.
To me, the computer is new, and the software running within it very powerful.
But, the atoms of my computer are quite old. Like you suggest, billions of years old.

 

[Studiot]

Not really.

It is a bit like my father's hammer that has had three new heads and seven new shafts.

Atoms are always exchanging parts of themselves (electrons) so each time this happens does that count as a new atom?

 

[Drakkith]

Also remember you are constantly burning fuel and replacing lost cells with new material. So depending on how you look at it, you are between 1 second and 14 billion years old.

 

[Ryan_m_b]

IIRC you're body swaps all it's cells every 7 years (some being replaced in days, others years). Presuming that this is true for atoms as well (I think it isn't because all of these cells are going to swap all their sub-cellular components within their lifetime but we'll roll with it for now) there are no atoms in your body that were there 7 years ago! Or perhaps some of them came back after spending time going through the sewage, into the sea, up to the sky, back down to a reservoir, out of a tap and into someone else.

Think of it this way, there could be an atom in me that you were born with!

 

[Integral]

With the exception of the Hydrogen, the atoms in your body have not existed since the beginning of the universe. The rest were created in a star sometime before the formation of our solar system. It is not possible say just how much earlier they were formed, but you can be sure that they are all at least 5 billion years old (or what ever the current accepted age of the solar system is). It does not matter that your body sheds cells since the atoms of the new cells are the same age as the ones shed.

 

[Drakkith]

I like how Carl Sagan put it. We are all children of the stars.

 

[DaveC426913]

IIRC you're body swaps all it's cells every 7 years (some being replaced in days, others years). Presuming that this is true for atoms as well (I think it isn't because all of these cells are going to swap all their sub-cellular components within their lifetime but we'll roll with it for now) there are no atoms in your body that were there 7 years ago!

A way-oversimplification.

1] It will be a bell curve. Some cells will last much longer than 7 years.
2] Some parts of your body are not cells. Your bones probably last much of your life.

 

[DaveC426913]

Atoms are always exchanging parts of themselves (electrons) so each time this happens does that count as a new atom?

Actually, there is a principle that all electrons are utterly indistinguishable (can't remember what the principle is). So exchanging one for another is meaningless.

 

[Drakkith]

I think by that reasoning all atoms of the same element are indistinguishable as well.

 

[Ryan_m_b]

A way-oversimplification.

1] It will be a bell curve. Some cells will last much longer than 7 years.
2] Some parts of your body are not cells. Your bones probably last much of your life.

It's a simplification yes but I don't think its a "way-oversimplification". I said "if I remember correctly" because I am not sure that that is the right number but either way your cells are constantly recycling material, building new parts etc. It is not unreasonably to say that the cells in your body (and consequently your body) undergo a theseus's ship phenomenon.

Bone is a highly dynamic tissue which is constantly being broken down by osteoclasts whilst simultaneously rebuilt by osteoblasts in a process known as remodelling.

 

[Studiot]

Actually, there is a principle that all electrons are utterly indistinguishable

I was going to say something like post#12 but Drakkith beat me to it.

So how about this:

When an atom of Natrium looses an electron it ceases to be an atom of anything. It becomes an ion.

When the ion gains an electron it becomes another atom of Natrium, different from the first one.

There is a definite, and maybe quite long, time interval between the original Natrium atom ceasing existence and the new one coming into being. The ion could have been stable in a rock crystal for millenia before gaining an electron an turning back into an atom.

 

[Dadface]

Hi Studiot,just out of interest where are you from? In the UK and I think,many other parts of the world natrium is now called sodium,but the original symbol (Na) is still used.

 

[Pengwuino]

Actually, there is a principle that all electrons are utterly indistinguishable (can't remember what the principle is). So exchanging one for another is meaningless.

That doesn't necessarily mean they are not capable of being distinguished in the sense that if I keep track of 2 molecules and send one to hte left and one to the right, the one to the left is always the guy to the left. So if you replace a molecule or cell in your body, it is certainly safe to say we know one cell use to be in your body and one cell is new to it, despite being atomically distinguishable.

What a fun thread.

 

[Studiot]

I agree this is a fun thread.

Studio T is located in the South West of England.

 

[Borek]

Presuming that this is true for atoms as well (I think it isn't because all of these cells are going to swap all their sub-cellular components within their lifetime but we'll roll with it for now)

I was always thinking about it this way - atoms/molecules of the dying cells are put back into the blood. Some of the substances will be excreted this way or another, but many - like for example amino acids, calcium, phosphates and so on - will be reused in some other parts of the body. So my bet is that atoms/simple molecules in the body can be described by their half life, which most likely means I have inside atoms of things my Mom eat before I was born (or - even - atoms of things that my Grandma eat long ago...).

 

[DaveC426913]

It's It is not unreasonably to say that the cells in your body (and consequently your body) undergo a theseus's ship phenomenon.

Yeah. you beat me to the http://en.wikipedia.org/wiki/Ship_of_Theseus" reference.

 

[BruceW]

The question is trickier than it first seems.
I guess the atoms themselves don't change for a long time (in terms of their half-lives).
But then the body is always exchanging the atoms inside our body for atoms outside our body. (This principle is used to explain carbon dating).
Also, most of the molecules in the human body are changing continuously. The body has a myriad of different chemical cycles, which it uses to change an excess of one molecule into another kind.
Although, I've heard that brain cells last for life. Is this true?
You could say that the atoms that exist on Earth came from a stellar explosion, and these atoms are continuously getting mixed around the Earth.

 

[Studiot]

You could say that the atoms that exist on Earth came from a stellar explosion

You could but I maintain that you'd be mistaken.

Pretty well all the matter from a stellar explosion is in the plasma state and not made of atoms at all.

 

[BruceW]

Ah, true. I meant that the heavier elements which now make up the Earth came from stellar explosion.
And in general, when I was saying that the atoms on Earth exist for a long time, I really mean the nuclei of those atoms, since the electrons do come and go.

 

[Studiot]

But nuclei are not atoms.
For one fundamental thing atoms are electrically neutral.

 

[BruceW]

I agree. I should have said nuclei, not atoms. I'm not trying to say they are the same thing.

 

[BruceW]

I think I said atoms because that's how it was explained to me. I guess the teacher doesn't want to make the concept more complicated by talking about what happens to the electrons.
But yes, the electrons do come and go, while the nuclei itself can stay the same element for a long time.

 

[bostonnew]

Ok. So let's say that I have helium in my body that is as old as the universe. And that I have other elements that have been formed via nucleosynthesis much later (but still before the birth of our sun). So far so good right?

Now, is it fair to say that the constituents of those heavier elements (quarks and what not) is as old as the universe as well? They've just been configured in a different way inside massive stars, but fundamentally (or subatomically if you will), it's all matter that existed immediately after the big bang.

Perhaps a simpler way to ask: Is matter conserved in the universe from the big bang until today? In which case every single particle (or string or whatever) of me must be that old.

Yes?

 

[BruceW]

Technically, Baryosynthesis started later than the start of the universe, so no nucleus could have existed for the same amount of time as the universe.
Things like fusion that create heavier elements isn't like getting two lumps of clay and sticking them with each other. Its like a whole new entity is created.
Matter definitely isn't conserved.
I guess another problem with all this is how you define a new piece of matter. For example, if an atom went into an excited state, then fell back down to the same state, is it 'the same piece of matter'? And if the atom changed element by undergoing beta decay, then went back to the same element by electron capture, then is the piece of matter the same?
For classical objects, its obvious what is meant by 'the same piece of matter' because no two objects are exactly the same.
But for quantum objects, it gets a bit trickier.

 

[Neandethal00]

Hi all,

Can someone tell me how old are the atoms my body is made off? In other words, how old am I really?

THANKS

This got to be one of the bestest threads on phyics forum. ha ha ha. I have nothing to contribute at this moment, I'm stll thinking the significance of the question.

There are so many other simple questions we don't ask ourselves, but which can lead to amazing discoveries about us.

Sometimes I get the feeling mysteries of the universe can well be found inside our bodies, the info is somewhere embedded within our body. It may not be necessary to study objects billions of light years away. Just a thought.

 

[Drakkith]

If we REALLY want to get down to the bottom of this, everything in your body is a result of what existed at and right after the big bang. All particles trace their origins back to the content of the universe at this point. As such, you are most definitively as old as the universe is.

 

[bostonnew]

Yay! that's pretty cool:-)

Thanks guys.