ENRICO FERMI (1901- 54)

1942 – USA

Fermi established his reputation with his concept of radioactive beta decay, the theory that a proton could be created from a neutron via the shedding of an electron (a beta particle) and an antineutrino.

The Joliot-Curies had announced their discovery that radioactive isotopes could be generated artificially by showering certain elements with alpha particles in 1934. Fermi realised that the newly discovered neutrons would be even better suited to this purpose as their lack of charge would allow them to slip into elements’ nuclei without resistance.

Fission chain reaction

Fission chain reaction

Fermi established the concept of ‘slow-neutrons’ by placing a piece of solid paraffin in front of the target element during bombardment. Working his way through the elements he created a number of new radioactive isotopes.

He was awarded the 1938 Nobel Prize for physics and later the significance of his work when applied to uranium was realised. Using his neutron-bombarding technique in a series of experiments with 235uranium, Fermi and NIELS BOHR confirmed that a nuclear chain reaction could almost certainly be created as the basis of an atomic bomb.

By Dec 2 1942 his team had created an ‘atomic pile’ of graphite blocks, drilled with uranium, which went on to produce a self-sustaining chain reaction for nearly half an hour.

picture of the Nobel medal - link to nobelprize.org

Wikipedia-logo © (link to wikipedia)

NEXT buttonTIMELINE

Advertisements

MURRAY GELL-MANN (b.1929)

1964 – USA

‘Neutrons and protons are made up of particles called quarks. Like electrons, they cannot be subdivided further’

Photograph of MURRAY GELL-MANN ©

MURRAY GELL-MANN

The standard model of particle physics divides all elementary particles into three groups:

six types of leptons
electron, electron neutrino, muon, muon neutrino, tau and tau neutrino
six types of quarks
up, down, charm, strange, top and bottom    and
four types of bosons

   
Ordinary matter is made up of:

protons
each an up-up-down quark triplet
neutrons
each an up-down-down quark triplet    and
electrons

 

Gell-Mann predicted the existence of three quarks; up, down and strange. Other scientists predicted another three. Quarks cannot exist singly.

picture of the Nobel medal - link to nobelprize.org

Link to WIKIPEDIA

NEXT button - GORDON MOORETIMELINE

NEXT button - ABDUS SALAMSTANDARD MODEL