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.
Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.