[gerad]

I read it as:

- Today, I need to predict tomorrow’s weather.

- Yesterday I made some measurements of the (temperature, pressure, etc) conditions that I need for today’s prediction.

- Yesterday it was impossible to know what measurements I’d optimally need to take for today’s forecast.

- Today, I can (quantumly, probabilisticly) go back in time and make sure I have the optimal set of measurements for today’s prediction.

- I can’t change anything that happened between yesterday and today, but I now have better information I can use to change tomorrow.

[xwdv]

If you already know the optimal set of measurements why not skip the whole traveling back in time part and just change tomorrow today?

[gerad]

> The problem is that, only after the interaction does the metrologist learn which input would have been optimal.

[goodluckchuck]

So you can measure the past, but not change it?