[Boogieman]

Both “traveling” and “travelling” are correct spellings. I believe Nature is a British periodical, and the later is actually the preferred spelling there.

[wideminded]

1. It's spelling not speling.

2. 'Travelling' agrees with the double-consonant rule before 'ing'.

3. 'travelling': 178 million hits, 'traveling': 280 million. Same order of magnitude.