The other option is radioisotope decay, which uses a substance such as polonium-218 to heat and evaporate a liquid.

另一个选择是放射性同位素衰变，即利用一种物质，如polonium-218，加热并蒸发液体。

Another is that the liquid evaporated.

另一个是液体蒸发了。

Here is Dr. Kripa Varanasi from the mechanical engineering department at M.I.T. explaining it: They're levitating on their vapor layer with the vapor cushion that's forming because the liquid is evaporating.

以下是麻省理工学院机械工程系的克里帕·瓦拉纳西博士的解释: 水在蒸发时会形成隔热的蒸汽层，水珠悬浮在蒸汽层上。

Here is Dr. Kripa Varanasi from the mechanical engineering department at M.I.T. explaining it: Kripa Varanasi: They're levitating on their vapor layer with the vapor cushion that's forming because the liquid is evaporating.

这是麻省理工学院机械工程系的 Kripa Varanasi 博士。解释它：Kripa Varanasi：它们漂浮在它们的蒸气层上，由于液体正在蒸发而形成蒸气垫。