How can no system be "closed"? If nothing can get in, than isn't it closed?

Question

I'd like a less patrinizing veue, because my science didn't exactly explain it well. how is there no such thing as a closed system?

Answer 1

Something can always get in or out.
There is only one truly closed system, the entire universe.

Answer 2

we have 3 kinds of sysetms: open, closed or isolated. A closed system is a one from which nothing can come out and in which nothing can enter(there is no tranference of matter). But the isolated type is aone in which there is no transference of matter, nor energy. THIS is the kind of system that we say doesnt realy exist, cause we cant have any system that doesnt releive or gain energy. so we HAVE closed systems, like a flask of water, which doesnt send the vapour out.

Answer 3

I was always under the impression our planet could be considered a "closed system." We transfer energy - but not matter - to surrounding environments.