Why is the bowl of the radio telescope painted white?

The colour of the telescope has no effect on its electromagnetic properties but it does play an important role in regulating temperature.

By Gareth Mitchell

Asked by: Alan Blackwood, by email

The colour of a dish doesn’t have any bearing on its electromagnetic properties. However, white reflects sunlight and heat, and that limits how much the temperature of its surface fluctuates. The shape of a radio telescope dish is critical in order for it to perform well as a receiver. Limiting shifts in temperature therefore helps to reduce thermal expansion.

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