"A scientist who fired projectiles into the bedrock at medium to low speeds discovered that doing so caused fluctuations in the electron density of the ionosphere above the spot," says Kuo. "This suggests that these electron densities are very sensitive to change."
「過去曾有科學家以中低速子彈，射擊地底岩塊，結果發現上空的電離層濃度竟也會產生波動，顯示電離層的濃度變化是相當敏感的，」郭鎧紋說。