https://finance.google.com/finance?chdnp=1&chdd=1&chds=1&chd...
And then over the next 5 years, from 1996-2000, when it went from 1000 to 4000:
https://finance.google.com/finance?chdnp=1&chdd=1&chds=1&chd...
The short answer to your question is yes, we are in a bubble. We are always in a bubble, somewhere. You can usually tell where it is by looking at whatever people are really excited about, and it lasts as long as they continue to be excited, which inevitably is not forever. You can't usually tell when people are going to cease to be excited, which is why timing the tops of bubbles is a fool's errand. It's up to you how much risk you want to take - because everything is a bubble, you can't actually opt out of the game, but you can choose to protect yourself by investing in things that people are unlikely to get significantly more or less excited by. You miss out on the vast majority of gains across the overall market by doing this, though.
It's sort of a metaphor for life: we're born, we grow rapidly, at some point we get boring, and then eventually, with 100% certainty, we die.