How fast does the sun travel across the sky?

By MUNGAI KIHANYA

The Sunday Nation

Nairobi,

11 January 2026

Joseph Otieno asks a peculiar question: “How fast does the sun move across the sky from morning till evening?” He says he wondered about it after reading somewhere that the earth is spinning at over one thousand kilometres per hour, yet “when I look at the sun, it doesn’t seem to be moving at all.”

Otieno continues to correctly state that “when I am in a car travelling at 100km/h, I see the road going past backwards at 100km/h… Why not the sun?”

Before attempting to calculate the “speed of the sun across the sky”, let us first clarify the issue of the rate of spin of the earth. It is inaccurate to state it in kilometres per hour because the value depends on your location of the planet. For people like us (Kenyans) who live very near the equator, we are at the farthest distance from the axis of rotation that runs from the North pole, through the centre of the planet to the South pole – about 6,400km.

Residents of Iceland are much closer to the axis. At a latitude of 65 degrees, Iceland is less than half the distance of Kenya from this axis – it is only 2,700km away. As the earth rotates, Kenyans traverse a total distance of just over 40,000km in 24 hours while Icelanders travel just 17,000km. Thus, the speed of Kenyans comes to 1,675km/h while that of the Icelanders is 707km/h.

The correct way to express the speed of rotation is in degrees per hour. A full circle is 360 deg and the earth completes that in 24h, so the angular speed is 15 deg. per hour – no matter where you are; everyone completes one rotation at the same time.

In the same breath; the speed of the sun across the sky is also 15 degrees per hour. This is very slow as rightly observed by Otieno. If we want to get a value in kilometres per hour, we need to first ask how far does the sun appear to be?

The answer is that it appears to be located at the limit of the human perception of depth. We can only perceive depth up to 2km; after that everything seems to be the same distance away. The moon appears to be same distance as the sun, doesn’t it?

A 2km semi-circle of the sky is just about 6km long – from horizon to horizon. The sun traverses this distance in about 12 hours. So, its apparent speed is about 0.5km/h. That sounds about right, doesn’t it?