&gt; So if I understand correctly this would be somewhat akin to having a &quot;universal clock&quot; that is ever increasing, and that can be read&#x2F;seen by anyone (like you said, universally). So you only need to know the &quot;time&quot; on the clock, when you do something, so that afterwards you can verify that indeed the &quot;timestamp&quot; happened.<p>As long as you where online during that time, or as long as you trust a third party to record the CMB radiation for you, yes.<p>The really cool thing is that this wold apply not just anywhere in the universe, but because nothing travels faster than light any communication being done between blockchains between planets would always be in sync. The CMB Radiation simply reaches the other planet at the same time the communication does.