typo corrected: heart -> Earth

[horstjens]

Describe your change:

• [ ] Add an algorithm?
• [x ] Fix a bug or typo in an existing algorithm?
• [ ] Documentation change?

Checklist:

• [ x] I have read CONTRIBUTING.md.
• [x] This pull request is all my own work -- I have not plagiarized.
• [x ] I know that pull requests will not be merged if they fail the automated tests.
• [ x] This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.