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View Full Version : Are We 13.7 Billion Years old?



MilkyJoe
2010-Oct-05, 05:49 PM
I don't mean in the form we are, but the very "building blocks".
I say 13.7 billion years because that's the current theory on the age of the universe (I think).

Buttercup
2010-Oct-05, 07:03 PM
Speaking only for myself -- no.

But I won't tell my true age either. :p ;)

MilkyJoe
2010-Oct-05, 07:17 PM
Not even to the nearest billion years? You look like Natalie Portman, so you can't be that old...

The Backroad Astronomer
2010-Oct-05, 07:35 PM
Some parts of us are.

Strange
2010-Oct-05, 07:54 PM
We are stardust, we are golden ...

(I'm guessing you have to be a bit older than MilkyJoe to get that)

JohnD
2010-Oct-05, 08:00 PM
Maybe the sub-atomic particles in the star-dust elements we are made of are that old.
At the Big-Bang and for about a minute afterwards, there wasn't even hydrogen in existence, just electons , protons and neutrons.
Elements other than hydrogen and helium had to wait for the formation and super-novation of the first stars, about a 100 million years later.

John

MilkyJoe
2010-Oct-05, 08:30 PM
That's what I mean, the "building blocks". Energy cannot be be created, nor destroyed. What we are made of must have been in existence (in one form or the other) since the creation of, well, everything.
I've heard people saying we are made of stars, I've never really thought about it til, well, I really thought about it.

Trebuchet
2010-Oct-06, 02:54 PM
MJ, I think pretty much only the lightest elements were created in the big bang. Heavier elements had to be created by fusion in the stars. That's why we're "made of stars".

slang
2010-Oct-06, 11:32 PM
There's a fun calculation I've seen which (IIRC) shows that you are breathing some oxygen atoms that Marilyn Monroe breathed too, thus sharing a breath with her. Perhaps the same atom once went through some Tyrannosaur Rex's mouth, perhaps once through some single cell creature, maybe it was once part of a star that no longer exists. Maybe it was created in the aftermath of the Big Bang. If only it could tell its story.

Ken G
2010-Oct-07, 01:22 AM
Not just breathing oxygen-- there is oxygen in your body now that was once in Marilyn Monroe's body. And your roommate, and the guy in the subway. What's more, every electron in your body is identical with every other electron in creation, can cannot even be said to be in you and not in alpha Centauri (that there is an electron in you can be said, but not that it is the same electron it was a second ago, as they are all indistinguishable). We are all much closer than we think.

Jeff Root
2010-Oct-07, 07:11 AM
I was going to say the same that Ken just said about all
electrons and so forth being identical, so that saying a
particular electron or whatever in my body was previously
in some other person's body is not clearly meaningful.

However, I think Ken goes too far with the Alpha Centauri
comment. Light from Alpha Centauri might contribute
energy to a carrot, and I might eat the carrot and absorb
energy from it which could be interpreted as including the
energy from Alpha Centauri, but there is no reason to
conflate an electron in Alpha Centauri with an electron in
my body, any more than there is reason to think that a
carotene molecule in the carrot I eat is the same carotene
molecule as one in a carrot in Perth.

-- Jeff, in Minneapolis

Ken G
2010-Oct-07, 01:24 PM
Light from Alpha Centauri might contribute
energy to a carrot, and I might eat the carrot and absorb
energy from it which could be interpreted as including the
energy from Alpha Centauri, but there is no reason to
conflate an electron in Alpha Centauri with an electron in
my body, any more than there is reason to think that a
carotene molecule in the carrot I eat is the same carotene
molecule as one in a carrot in Perth.On the contrary, there is one very good reason to think that-- it is called quantum mechanics. In that theory, every scrap of material that is in causal contact with any other scrap shares all the same identical particles with that other scrap. Just track it back to the Big Bang where the electrons came from in the first place-- we cannot say that the electrons that ended up on Earth came from a different source than those that ended up on alpha Centauri, without claiming that electrons are indeed distinguishable from each other. But it is a well known (and important) consequence of quantum mechanical predictions (borne out by experiment) that the electrons are indeed indistinguishable-- they cannot be said to have come from different sources, for that would distinguish them. Same for protons, same for carotene molecules-- it's just that this detail usually (and fortunately) matters only the minutest amount and can be neglected in most practical calculations.

Jeff Root
2010-Oct-08, 05:19 AM
I take the fact that all electrons are identical as a given. That
means they are indistinguishable. Obviously. And that means
it is not possible to say, just by examining an electron, where
it came from. Obviously.

But claiming that that means an electron on Earth now could
have been in Alpha Centauri a second ago (my understanding
of what you said in post #10) is mind-bogglingly idiotic.

It is exactly what the bugblatter beast would believe.

-- Jeff, in Minneapolis

Fooglmog
2010-Oct-08, 06:32 AM
Let's be careful about the language we use here Ken G. We want to be accurate.

Electrons are not "indistinguishable". They are merely "identical". Electrons can be distinguished from one another based upon location and intertial characteristics.

Jeff Root
2010-Oct-08, 08:59 AM
Ah! That's a good way to describe it.

-- Jeff, in Minneapolis

Ken G
2010-Oct-08, 03:54 PM
Let's be careful about the language we use here Ken G. We want to be accurate.

Electrons are not "indistinguishable". They are merely "identical". Electrons can be distinguished from one another based upon location and intertial characteristics.No, electrons are indistinguishable. This is quite an important aspect of electrons, and that's why I am indeed being very careful about the language-- google, for example, "exchange energy", or "the Pauli exclusion principle." Both these physically observable effects require that electrons be more than identical-- they must in fact be indistinguishable.

So what do we make of the fact that two electrons appear to have two different locations and velocities? We make that this is purely an illusion about electrons, it is a kind of crutch we can often get away with using, but not always. When we write the "wave function" of two electrons, call them A and B, in two different states, call them psi1 and psi2, it looks like this: psi1(A)psi2(B) - psi2(A)psi1(B). The Pauli exclusion principle comes from setting psi1 = psi2 (note what happens).

Now look at that wave function, and tell me, which state is that of electron A? There's no such thing. (So how do we talk about psi(A) as "the wave function of electron A"? The same way we do lots of things in physics-- we make simplifications and approximations when we expect to be able to get away with it, but we recognize the deeper theory that says what we are doing is not the actual truth of the situation. Maybe none of our theories are the "actual truth", but we know when we are using one that isn't.)

George
2010-Oct-08, 05:08 PM
No, electrons are indistinguishable. This is quite an important aspect of electrons, and that's why I am indeed being very careful about the language-- google, for example, "exchange energy", or "the Pauli exclusion principle." Both these physically observable effects require that electrons be more than identical-- they must in fact be indistinguishable.

So what do we make of the fact that two electrons appear to have two different locations and velocities? We make that this is purely an illusion about electrons, it is a kind of crutch we can often get away with using, but not always. When we write the "wave function" of two electrons, call them A and B, in two different states, call them psi1 and psi2, it looks like this: psi1(A)psi2(B) - psi2(A)psi1(B). The Pauli exclusion principle comes from setting psi1 = psi2 (note what happens).

Now look at that wave function, and tell me, which state is that of electron A? There's no such thing. (So how do we talk about psi(A) as "the wave function of electron A"? The same way we do lots of things in physics-- we make simplifications and approximations when we expect to be able to get away with it, but we recognize the deeper theory that says what we are doing is not the actual truth of the situation. Maybe none of our theories are the "actual truth", but we know when we are using one that isn't.)
We give labels to collections of things and note their differences. As a collective body, your psi wave is going to be different than mine, right?

Some might say I'm a baboon? Please don't confirm their suspicions. ;)

slang
2010-Oct-08, 08:42 PM
Not just breathing oxygen-- there is oxygen in your body now that was once in Marilyn Monroe's body.

Mmmm... But, responsible, Sesame Street watching parents want to know: what about Katy Perry?


Some might say I'm a baboon?

Just indisting.... err, I'll get my coat. ;)