Day 6: Alice Springs to Tennant Creek
Alice Springs was founded in 1870 as a repeater station for the Overland Telegraph Line that linked Australia with the rest of the world. When Mum and Dad lived here 55 years ago-Dad was a mechanic for the Northern Territory's first tour operator, while Mum worked at the hospital-fresh milk and vegetables arrived once a week on the train from Adelaide.

Today, Alice Springs is a bustling community with all the modern conveniences you'd expect. And that's not necessarily a good thing: We see our first McDonalds, and our first traffic lights, in five days of traveling.

Today should be a straight 315-mile haul straight up the Stuart Highway to Tennant Creek, but to make things interesting, we're going to head west along Namatjira Drive, going as far out as the edge of the Tanami desert before looping north and then east to rejoin the Stuart Highway just 10 miles north of Alice. It's a 230-mile detour, but worth it for the spectacular views of the McDonnell Ranges and a distant glimpse of Gosses Bluff, a giant impact crater 140 million years old.

Out here, we cross the Tropic of Capricorn, the line that marks the most southerly latitude at which the sun can appear directly overhead at noon (the Northern Hemisphere equivalent, the Tropic of Cancer, passes through Mexico). Red desert's still rushing past the windows of the Outback. But we have officially entered the Tropics.