system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: When a person is "vaporized" by an atomic blast, what actually happens?

Is it primarily the temperature/radiation/blast wave or a combination?

How far away from something like a modern warhead would people be instantly vaporized instead of just horribly broken/burned

edit: It's not a school project.
gpt
These are quotes taken from the novel *The Last Train From Hiroshima* by Charles Pellegrino. It's a very lengthy explanation so I'll paraphrase and combine the parts to create a 'tl;dr' version. The following passage describes the untimely demise of one Mrs. Aoyama, who had the unfortunate distinction of being directly below the bomb as it detonated over the city of Hiroshima.

&nbsp;&nbsp;&nbsp;&nbsp;*"After only one-hundred-millionth of a second, the core (of the bomb) began to expand and the fission reaction began to run down. During this nanosecond interval, the first burst of light emerged with such intensity that even the green and yellow portions of the spectrum could be seen shining through the bomb's steel casing as if it were a bag of transparent cellophane. Directly below, Mrs. Aoyama was still alive and completely untouched by the flash. After one ten-thousandth of a second, the air began absorbing the burst and responding to it. Under the hypocenter (of the expanding neutron field created by the bomb's detonation), the blood in Mrs. Aoyama's brain was already beginning to vibrate, on the verge of flashing to vapor. What she experienced was one of the fastest deaths in all human history. Before a single nerve could begin to sense pain, she and her nerves ceased to be.*

&nbsp;&nbsp;&nbsp;&nbsp;*"Unlike the man leading a horse across the nearby "T" Bridge, Mrs. Aoyama could not possibly leave a permanent shadow on the ground. From the moment the rays began to pass through her bones, her marrow would begin vibrating at more than five times the boiling point of water. The bones themselves would become instantly incandescent, with all of her flesh trying simultaneously to explode away from her skeleton while being forced straight down into the ground as a compressed gas. Within the first three-tenths of a second following the bomb's detonation, most of the iron was going to be separated from Mrs. Aoyama's blood, as if by an atomic refinery."*

&nbsp;&nbsp;&nbsp;&nbsp;In short, it is a combination of a great many factors. Radiation, heat, and the blast wave all combine to create an incredibly fast death. Assuming you're at ground zero.

&nbsp;&nbsp;&nbsp;&nbsp; The book itself is incredible, and absolutely worth a read if the subject interests you.