What typically marks the end of one era and the beginning of another.

What marks it is when people start referring to that time like for example the dirty thirdys because people were like that and then it just dyed down and out never to be sot after again. Like know and the 2000's . When a era ends that means like time period that slowly went out like a star

This is all you, but i can give you some topics that you could try. if it rained when you want to do something outdoors, it 'limits' that human activity. maybe you want to do an experiment that goes throughout the whole year and you have to have above freezing the entire year. this 'limits' your activity. i thought of those just off of the top of my head. something that gets to me that might be getting to you is you are thinking too hard about what to do. think simply, and if it is too simple, then bump it up just a little bit.

Don't depend on this but logically i think c