How Does a Gram of Gold Outlast Time?

A gram of gold will always- Constant. It's a constant, right. The other thing that it has is it has to have a sense of difficulty. And if possible- That's like proof of work in Bitcoin. Well, we all know that Satoshi was mirroring the process of gold mining. Of course, with Bitcoin, there's a forgeably scarce proof of work bits. With mining, you have the physical gold that you get out of the ground, which you can then pass on to anyone.