both are valued in fiat. Fiat has changed (in the US at least) a couple times. States used to have their own bank notes. always be on guard with the US government, only the US mint can print money or coinage.
They can also change things or ban certain things.
i mentioned this on Bitcoin board.
The US may one be faced with having too many dollars, just like too many shares of stock. It is not inconceivable for them to issue what could be deemed a "reverse currency split" not different than a "reverse stock split."
i have heard it before forget where or from whom.
but remember, in the US, the dollars are really FEDERAL RESERVE NOTES.
its possible that one day, they could eliminate federal reserve notes, and perhaps call them something else, Liberty Notes or Freedom notes (just postulating) where say for every $1000 Federal Reserve notes that you have, you will now have $10 Liberty Notes or Freedom Notes.
It's a bit wild, but remember, BITCOIN and GOLD are once again valued in FIAT and the more FIAT the more they are supposedly "worth" the less FIAT, the less they may be "worth"
or do what Zimbabwe did
A solution effectively adopted by Zimbabwe was to adopt some foreign currency as official. ... In 2009, the government abandoned printing Zimbabwean dollars at all. This implicitly solved the chronic problem of lack of confidence in the Zimbabwean dollar, and compelled people to use the foreign currency of their choice.
but we are not at that breaking point yet in the US
News 
Market Data 
Discover 
