You could waste your whole life on a pipe dream.

你可以在白日梦上浪费一辈子时间。

Is this a pipe dream?

这只是个白日梦么？

A shiny new pipe dream.

闪亮的管子崭新的梦想。

You can forget it. It's only a pipe dream.

你可以忘掉它，那只是空想。

For its detractors, it is a mere pipe dream.

而对于其批评者来说，这只不过是白日做梦。