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SIZING IT UP

The indicator that will show whether bitcoin has split

By Joon Ian Wong

Bitcoin is in the middle of a contentious “hard fork” that could cleave the cryptocurrency in two for the first in its nearly nine-year-long history. The world could end up with bitcoin and a new cryptocurrency called “bitcoin cash” that promises to offer to an eight-fold increase in transaction capacity.

Even though a deadline of Aug. 1, 12:20 UTC has been set, the fork doesn’t exactly happen then. That’s because the proposal uses a particular calculation called “median time past” which, in practice, winds up being about an hour after 12:20 UTC, or 8:20 am US Eastern time.

So when, exactly, does bitcoin split? What we have now is a set of necessary but not sufficient conditions for a split. The technical indicator to watch for is the block size. The bitcoin protocol limits the size of each block, which is a bundle of transactions and other metadata, to 1 megabyte. Any block mined larger than 1 MB will be bitcoin cash’s “genesis block”—the starting point of a whole new cryptocurrency.

Watch the “size” column of the latest blocks mined at data provider Blockchain.info. Anything larger than 1,000 kilobytes shows that bitcoin has forked. This website also has a handy “chain split” monitor. This should happen any time now.