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To what extent can satellites have satellites? Could our moon have its own moon with its own moon, for example? Is there a limit?
Joe Roberts, St Austell, Cornwall, UK
Ben Hall/naturepl.com
Birds fly at tens of thousands of metres high. Ice forms on the wings of planes at this altitude, so why don’t the birds freeze?
Jane Pickett, Hitcham, Suffolk, UK
To answer these questions – or ask a new one – email lastword@newscientist.com.
Questions should be scientific enquiries about everyday phenomena, and both questions and answers should be concise. We reserve the right to edit items for clarity and style.…
