If plastic was made in 1907 how do they know it may take up to 1000 years to decompose?

Question

If plastic was made in 1907 how do they know it may take up to 1000 years to decompose?

In: Chemistry

Answer 1

Well it doesn’t.

There is not material called “THE PLASTIC”, just like how there is no such thing as “THE METAL”.
There are gazillion kinds of plastics, some of them are very resistant to the elements, some of them decompose when hit by a stiff breeze.
The “plastics take 1000 years to decompose” is a very nice and illustrative argument against littering. Without much insight on whats going to happen to said stuff.

As that depends on what kind of plastic we are talking about, how thick the thing you want to see disappear, where do you leave it (buried in earth, most plastics can last extreme long)… etc.
And ofc, there are unknown factors, like “will anyone create GMO organisms with the enzimes to eat the stuff”.