大象传媒

This mountain is Shishapangma, an 8,000-metre peak. The data shows that both Hillary and Tenzing - the bar-headed geese - actually crossed just to one side on their northward journey up to Tibet. If our calculations are right it's most likely they will fly back south this way, using the same route. If we can get up high enough, to the 'goose flyby zone', we might just be there when they go by - but we've still got another 1,000 metres climb to go. This will be the toughest part of the journey for us, and Hillary and Tenzing. No other bird on earth regularly flies this high. Where they go there is less than one third the amount of oxygen that there is at sea level, and it can be minus 50 degrees. The geese can fly up to 50 miles an hour, but add on a possible tailwind of up to 100 miles an hour and they can slingshot over the roof of the world in a matter of hours. This whole migration can be over in a