[pama]

There is a nice explanation at the end of the letter: “While PCTC simulations do not allow you to go back and alter your past, they do allow you to create a better tomorrow by fixing yesterday’s problems today.”

[dvaletin]

Basically, having infinite budget you can send any gift you can imagine to your friend via Amazon at day-1 and cancel irrelevant orders at day-0 except correct one to make your friend happy at his BD, which is day+1. Make better future correcting your past decisions based on today information. Now the question is: how to get enough money?

[DaveSchmindel]

Interesting. Isn't that just problem solving? If yesterday's problems are unsolved by today, aren't they just today's problems?

[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?