Temporal Drift

Temporal Drift is the technical name for the time differential between Earth and Altierra. There are few data points but enough to show that the differential is variable, both in a single portal and between the two.

The Tierrapuerta

The original portal between Patagonia and Alta had only one temporal data point. When the Spanish settlers passed through the portal, it was in 1585 Earth-reckoning, six years after the English had entered in 1579. The time difference in Altierra was 177 years however.

Because there is only one data point, it is impossible to see how time passes between the two worlds, whether it is logarithmic as in the Mundumbra, or a simple line.

The Mundumbra

There are a few more data points with the Mundumbra between Dartmoor and Isla Arbojan which shows that the time differential varies over time, In the short time, Altierran time is longer than Earth time, but this reverses about 3 years (where the time is the same with both).

Emily visits Altierra

The first data point in The Snow Beyond the Wall is when Emily enters Altierra and returns, looking for help for Meg who has been captured.

Earth Time	Alt. Time	Event
10.25	13.00	Emily passes through the portal into Altierra
10.40	13.55	Emily returns to Earth

15 minutes of Earth time is equivalent to 55 minutes in Altierra.

Three Maddisons enter Altierra

The second point is when Luke, Susan and Emily enter Altierra

Earth Time	Event
10.40	Emily passes through the portal into Altierra
12.25	Luke, Susan and Emily pass through the portal

Emily is back on Earth for 1 hour 45 minutes but finds about two days have passed.

Maddisons return to Earth

When the Maddisons return to Earth, after 3.5 months in Altierra, they find that (at least) 63 years have passed on Earth.

Maddisons return to Altierra

Once back on Earth, the Maddisons remain there for about two hours before returning to Altierra. They then find they have been away for three Altierran days. (It took them two days to reach Elísal).