Death happens when the heart stops.

The heart is a pump that circulates blood in the body. The pumping action is done via electrical pulses that occur when a chemical reaction occurs at the hearts nerve center.

There is a piece of flesh in the body if it becomes good the whole body becomes good but if it gets spoilt the whole body gets spoilt and that is the heart.

Allah does not change a people's lot unless they change what is in their hearts.

Surat I-ra ‘d (The Thunder), verse 11.

One may visually detect the death of life,

when the life is leaving the body, via Electro Photonic Imaging photographs. The bodies bright glow raises upward and fades as the light particles dissipate slowly over the time of 3 days.

Electro Photonic Imaging photographs

One may visually detect the initiation of life at Conception;

when the sperm meets the egg, it is the moment the zinc atoms in the egg start to explode. It is a chemical reaction.

When the heart stops the person is named Dead.

The purpose of the heart is to pump blood. The purpose of the blood is the movement of nutrients. Oxygen is the most critical item for the blood to circulate, the big demand in the body for oxygen can not be met without the Pulmonary system, which uses the Lungs to capture the oxygen from breathing, and bring it into the blood stream. When the oxygen supply goes down the life begins to fade starting at the eyes.