Neutron Lifetime
The Unstable Neutron
The neutron was the last of the three sub-atomic objects to be discovered. The electron was identified in 1897 by J. J. Thomson. The proton was discovered in 1917 by Earnest Rutherford and named by him in 1920. The concept of a neutron was developed by Rutherford in 1920, but it wasn’t until 1932 that James Chadwick verified its existence.
One good reason for this late discovery is that the neutron is unstable outside a nucleus. Once freed from its stable nuclear home, in approximately fifteen minutes, the average neutron will spontaneously “beta decay” (little bang) into a stable proton and a stable electron, which then naturally combine into a stable hydrogen atom.
Fifteen minutes is not a very long average lifetime. This translates into a “half life” of approximately ten minutes for any collection of free neutrons. Half life is the time taken for any radioactive quantity to fall to half its value.
For example, if at some magical moment, the entire universe were made of only neutrons, say equal in number to 3 x 1079, then after 10 minutes half of them would have transformed into proton and electron pairs leaving 1.5 x 1079 neutrons behind. After another 10 minutes only 7.5 x 1078 neutrons would remain. After another 10 minutes another 3.75 x 1078 neutrons would have transformed, and so on.
After spontaneously halving in number about 264 times, all the neutrons in the universe would be gone, leaving behind an equal number of protons and electrons. The total elapsed time would be about 2,640 minutes, equal to 44 hours, less than two days! Free neutrons just don’t hang around.
The spontaneous transformation of neutrons is of fundamental significance in Neu Theory. The concept of “lifetime”, here meaning a measurable duration of time between significant transformative events, begins at the quantum level with the neutron. As we shall see next in 3.1 – The Little Bangs Hypothesis, without neutron transformation, there would be no electricity, no space, no motion, and no light. The universe as we know it just would not exist.