Asked by: Zahi Assir

We know the Earth goes round the Sun, all the way around is 2 radians (360 degrees). We also know that it takes a year (approx 365 days) which is therefore about 3.2x10

Therefore = 2 / 3.2x10

However, if we can measure the distance to the Sun we can also calculate the velocity of the Earth relative to the Sun. Although unless we define a direction this is more technically known as the speed. This can be done by looking at the definition of the radian. The radian is a unit which conects the radius of an arc, the length of the arc and the angle subtended by the arc. The formula for this is s = r x (where s is the length of the arc, r is the radius and the angle). So if we know the radius of the Earth's orbit (1.5x10

So, the Earth travels through space (relative to the Sun) at: v = 2.0x10

Answered by: Edward Rayne, Physics Undergraduate Student, Cambridge UK

'Our job in physics is to see things simply, to understand a great many complicated phenomena, in terms of a few simple principles.'**Steven Weinberg**

(*1933-*)

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