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There is no consensus definition of what a blockchain is. In fact the Satoshi whitepaper that introduced Bitcoin does not even use the word blockchain it talks

There is no consensus definition of what a blockchain is. In fact the Satoshi whitepaper that introduced Bitcoin does not even use the word blockchain it talks about a hash chain of blocks a concept which predates Bitcoin by ~30 years. The real innovation of Bitcoin was to use PoW to both limit Sybil attacks and to make additions to the hash chain computationally expensive to revert. Often however when people talk about blockchains they are talking about systems which don't use PoW at all. Like end-to-end encryption or peer-to-peer networks blockchain describes a cloud of concepts and technologies. A better terminology would be DLT (Distributed Ledger Technology).

jason_slack 9y ago
If so many companies are doing things for the blockchain, are they storing in the same blockchain as bitcoin or are companies creating more blockchains and needing miners to help mine, etc,
- EthanHeilman 9y ago
  We are still very much in the experimental phase of the technology and companies are taking many different approaches. Some companies are using Ethereum as their blockchain so they don't have to build and operate one. Other companies are launching blockchains by which they mean a ledger created by a set of trusted validators running a BFT algorithm (see Distributed Systems). Systems built on a trusted set of validators don't need miners as they don't use PoW.
  - jason_slack 9y ago
    That makes sense. Thanks for explaining. They really just mean a ledger. Doesn't one lose the trust if the ledger is not distributed and verified by outsiders? Using a trusted set of validators, I assume is an internal operation. They aren't asking "Joe Nobody" off the street to become a trusted validator...
    - EthanHeilman 9y ago
      The hope is that the validator set would include many different trustworthy organizations in different parts of the world.
      - moocowtruck 9y ago
        could all these validators agree at their own whims to roll back their ledger to undo a change?

jason_slack 9y ago

If so many companies are doing things for the blockchain, are they storing in the same blockchain as bitcoin or are companies creating more blockchains and needing miners to help mine, etc,

EthanHeilman 9y ago
We are still very much in the experimental phase of the technology and companies are taking many different approaches. Some companies are using Ethereum as their blockchain so they don't have to build and operate one. Other companies are launching blockchains by which they mean a ledger created by a set of trusted validators running a BFT algorithm (see Distributed Systems). Systems built on a trusted set of validators don't need miners as they don't use PoW.
- jason_slack 9y ago
  That makes sense. Thanks for explaining. They really just mean a ledger. Doesn't one lose the trust if the ledger is not distributed and verified by outsiders? Using a trusted set of validators, I assume is an internal operation. They aren't asking "Joe Nobody" off the street to become a trusted validator...
  - EthanHeilman 9y ago
    The hope is that the validator set would include many different trustworthy organizations in different parts of the world.
    - moocowtruck 9y ago
      could all these validators agree at their own whims to roll back their ledger to undo a change?