Where does the 33.33% threshold for selfish mining come from?

The discussion emphasizes the importance of accurate timestamping in blockchain technology and presents various methods for nodes to maintain accurate timekeeping without relying on a universally agreed-upon source. Nodes rejoining the network can adjust their clocks based on the timestamps of the most-work chain, acknowledging that their internal clocks may not accurately reflect the true arrival times of blocks. This adjustment is crucial for maintaining the integrity of the blockchain, as accurate timestamps play a significant role in various blockchain operations, including the prevention of selfish mining practices and the regulation of coin release by miners.

The narrative further explores alternative methods for nodes to ascertain current UTC time with a reasonable degree of accuracy, suggesting a range between +/- 5 to 15 seconds. It strongly advises against the adoption of a single time source, such as GPS or NTP, to prevent centralization. An innovative proposition for true decentralization involves using astronomical observations, allowing a node to calibrate its clock based on geolocation and stellar movements. This method would significantly increase the difficulty for attackers aiming to manipulate local timestamps, as it would require altering Earth's orbit or redefining UTC.

Moreover, the text delves into the implications of accurate timestamping on the blockchain ecosystem, particularly in relation to Opentimestamps and the dynamics of miner rewards shifting from block rewards to transaction fees. As the system transitions, the concern over miners manipulating timestamps to influence mining difficulty and inflate earnings becomes less relevant. Instead, the focus shifts to how timestamp manipulation might affect the utility and value of the cryptocurrency, influenced by changes in transaction speed and block space. The impact on smart contracts and scripts, which depend on block height and timestamps, is also considered, highlighting that the ultimate effect on a cryptocurrency's value will depend on the balance between fees per second and its exchange rate.