How long does a moment last?

Does it end in the blink of an eye?  Ephemeral, never to truly be experienced again?

Does it linger, as time stretches, and you can't think of anything else?

Does it become forever etched into your mind, something that you can forget about, but never really forget?

Can it be captured?  Can it be relived?  Can it be shared?

Is it something that will live on, years later, as an echo, a glimpse of a time no longer, a memory?

How long, is a moment?