Blockchain from First Principles

Most explanations of blockchain begin with a definition and spend the rest of the time defending it. You finish knowing the words without knowing why anyone built the thing. This course starts with the problem instead. It covers why digital records are fundamentally different from physical ones, and why that difference made digital cash impossible to build for decades. It explains what a cryptographic hash is and how linking blocks with hashes makes any alteration immediately detectable. It covers how thousands of independent computers come to agree on one version of events with no central authority, and what the two dominant approaches to that problem actually secure. It then covers the limits honestly. A blockchain guarantees considerably less than most people assume. It cannot verify that a record was true when written, has no awareness of anything outside itself, and trades speed and cost for the properties it provides. Knowing precisely where those boundaries sit is the difference between understanding this technology and repeating marketing language about it. Chapter 3 is hands-on. You will open a block explorer, find a real transaction, trace it from end to end, and verify a claim yourself rather than taking someone’s word for it. No prior technical knowledge is assumed. There is no programming, no mathematics beyond arithmetic, and no requirement to own or buy anything.