The first thing most people notice about a Sahara night is the cold. The sand, which stored heat all day, begins radiating it upward as soon as the sun goes down. Within two hours, the surface temperature of the dunes has dropped from fifty degrees to fifteen. By midnight, the air temperature at camp is ten degrees or below. The same desert that is brutal at noon is cool enough for a light sleeping bag by midnight. People who arrive expecting to sleep under the stars in warmth are consistently surprised.

The second thing people notice is the silence. Not the absence of sound - there is wind, and occasional sounds from camels at the edge of camp - but the specific quality of silence that large empty spaces produce. Sound in cities is omnidirectional: it arrives from every angle simultaneously and is never absent. In the desert, sound has direction and source. The wind makes a sound that changes as it changes speed. A camel moves and the sand compresses under its weight with a specific sound that is not like any other. Between these sounds, there is a silence that is not empty but present.

Stargazing from the dune crest at ten o'clock on a new moon night is an experience of scale. The Milky Way occupies approximately forty degrees of sky from the horizon to the zenith. The galactic core, in Sagittarius, is visible as a distinct structure of light with dark lanes of dust threading through it. This is not what you see from a European backyard. This is the galaxy, seen from inside it, in the direction of its own centre, with two and a half billion years of stellar evolution visible in a single look.

The temperature reaches its minimum between three and five in the morning, typically six to eight degrees Celsius at camp level. Photographers who are shooting star trails or deep sky targets through the night dress for this: base layer, mid layer, windproof outer layer, and gloves thin enough to operate camera controls through. The dew point drops overnight, and by four in the morning there is visible condensation on metal equipment surfaces that is cold enough to make bare fingers uncomfortable on contact.

Dawn in the Sahara is the reverse of sunset, and it is equally dramatic. The east begins to lighten forty minutes before the sun appears. The dune profiles become visible first: dark shapes against a lightening sky. Then the colours emerge - the same amber and purple sequence, running in reverse from night to day. The first direct sunlight hits the highest dune crests while the valleys between them are still in shadow, and for twenty minutes the dune field is a study in alternating gold and shadow that no photograph adequately captures.

The first warmth of the morning sun arrives with extraordinary precision. You are cold, and then you are not cold, and the transition takes approximately thirty seconds. The change is physiological - the sun's radiation warming the skin surface directly - but it feels more fundamental than that. The body responds to morning sun in the desert differently from how it responds to morning sun anywhere else, and the difference is probably a function of the cold that preceded it.

Breakfast at camp, prepared by the Sahrawi team who have been managing desert camps for generations, is a different meal from any other breakfast. The combination of a night in the cold, followed by the heat of the first sun, followed by sweet mint tea and flatbread made on the fire, is a sequence that has been repeated in the Sahara for as long as people have been sleeping there. You are not discovering something. You are participating in something old.