One light year is about 9 trillion kilometers. arcturus is a star that is 37 light years from earth. if you are about 11 years old now, how old will you be when light that is leaving arcturus today reaches earth? how far, in kilometers, will it have traveled?

If a hydrogen atom is neutral, it must also have  one electron. an oxygen atom (o) has an atomic number of eight (8). this means a neutral oxygen atom has eight protons and eight electrons. the element actium (ac) has an atomic number of 89, so it has 89 protons and 89 electrons in a neutral atom