Did humans descend from other primates?

[McCulloch]

Man did not descend from the primates.

Did humans descend from other primates?
Are humans primates or should there be special biological taxonomy for humanity?
Please cite evidence.

[LiamOS]

While my knowledge on radioactive decay isn't great, I'm not sure that neutrons are released during decay.
During fission they most certainly are, but fission isn't really the process with which we're concerning ourselves.

[Grumpy]

AkiThePirate

The alpha particle is basically a helium nucleus that is released from a decaying or fissioning atom at approximately 1/10 of lightspeed. While it is itself not a neutron, it interacts with the atoms around it and will cause them to release approximately 450,000 neutrons. Such interactions mean the alpha will not penetrate more than a few centimeters of air and can be stopped by a single sheet of paper. Any of the 450,000 neutrons created can convert a nitrogen 14 atom into a carbon 14 atom.

The beta particle is itself a very energetic electron travelling at 270,000 kilometers per second. It is much less massive than the alpha but can penetrate much further, causing more damage. It takes a few centimeters of aluminum or about 3 meters of air to stop.

Both are given off by the decay of massive atoms(uranium being the most common)to redress the energy balance between the original atoms and the daughter or daughters.

In addition, massive radioactive atoms undergo spontaneous fission, giving off neutrons(sometimes called "prompt neutrons")at the moment of fission. It is these neutrons interacting with other radioactive atoms that causes the chain reaction in nuclear reactors and bombs. They also can cause nitrogen 14 to become carbon 14.

Grumpy

[LiamOS]

Awesome.

May I ask through what interactions the Alpha particle causes the neutron release?

[Grumpy]

AkiThePirate

May I ask through what interactions the Alpha particle causes the neutron release?

To oversimplify, think of a cue ball blasting into the racked balls during a break. But the racked balls are composed of numerous discrete parts that, given enough of a hit, break to one degree or another. The alpha is such a massive particle(relatively)and has such energy due to it's speed that it bounces around in the medium it travels through and hits many other atoms or molecules, breaking parts off of many of them. This is why it cannot penetrate very far before it loses that energy and becomes just another helium nucleus.

Beta particles, being basically electrons, interact very weakly with any particular atom or molecule despite it's speed(near lightspeed). That is why it can penetrate matter orders of magnitude more than the alpha.

Here is a good series of explanations from the Discovery site. Radiation and nuclear decay can be very complex, there are many different ways atoms can behave when subjected to radiation, but these articles cover the basics pretty well.

Grumpy

[LiamOS]

Is there a non-oversimplification?

I'm rather interested in the actual interactions involved as I've never really looked into larger scale interactions.

[Grumpy]

Here is a series aimed at undergraduates in the Chemistry and Biology areas.

This is a class at UC Berkley(warning, lecture 2 is more than 7 Megabytes). Lecture 1 has several charts(Powerpoint type)that contain a whole lot of info.

Grumpy

[otseng]

Uranium doesnt turn INTO carbon 14, but the neutrons RELEASED from decay are picked up by carbon making c12 carbon, c14 carbon.

The issue is not U turning into C14, but the issue is that U decay does not produce sole neutrons. Also, I have not seen any explanation of the origin of C14 through C12 capturing neutrons. Do you have any support for this? The only pathway I've seen is:

1n + 14N → 14C + 1H

http://en.wikipedia.org/wiki/Carbon-14# ... tive_decay

[otseng]

The alpha particle is basically a helium nucleus that is released from a decaying or fissioning atom at approximately 1/10 of lightspeed. While it is itself not a neutron, it interacts with the atoms around it and will cause them to release approximately 450,000 neutrons.

You'll need to elaborate on this. What is the steps here from one alpha particle to 450,000 neutrons?

Also, from my understanding, the conversion from N14 to C14 involves elemental nitrogen, rather than N as part of a compound.

In addition, massive radioactive atoms undergo spontaneous fission, giving off neutrons(sometimes called "prompt neutrons")at the moment of fission.

This would be the only time I can see where U can emit just neutrons.

However, for spontaneous fission of U, it occurs very rarely and can be considered a negligible source of neutrons.

For uranium and thorium, the spontaneous fission mode of decay does occur, but it is not seen for the majority of radioactive breakdowns, and it is usually neglected except for the exact considerations of branching ratios when determining the activity of a sample containing these elements.

http://en.wikipedia.org/wiki/Spontaneous_fission

[otseng]

I think what grumpy was referring to was the release of neutrons upon fission, but I'm not entirely sure. ²³⁸U fissile though and makes up almost all natural uranium.

Just a correction here. Technically U238 is not fissile.

Uranium-238 (238U or U-238) is the most common isotope of uranium found in nature. It is not fissile, but is a fertile material: it can capture a slow neutron and after two beta decays become fissile plutonium-239.

http://en.wikipedia.org/wiki/Uranium-238

[LiamOS]

Oh, that was a massive typo on my part.
When I said:
"²³⁸U fissile though and makes up almost all natural uranium."
I meant to say:
"²³⁸U is not fissile though and makes up almost all natural uranium."

I apologise.


Also, Grumpy, do you perhaps have Feynman diagram or general outline of the interactions which take place in the emission of a neutron due to nucleic interaction with the alpha particle?