Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Conservation law Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English Simple English