To convert $1.6 \times 10^{-7}$ into decimal notation, you move the decimal point in $1.6$ seven places to the left.

Starting with $1.6$:

1. Move the decimal point one place to the left: $0.16$
2. Move the decimal point two places to the left: $0.016$
3. Move the decimal point three places to the left: $0.0016$
4. Move the decimal point four places to the left: $0.00016$
5. Move the decimal point five places to the left: $0.000016$
6. Move the decimal point six places to the left: $0.0000016$
7. Move the decimal point seven places to the left: $0.00000016$

Thus, $1.6 \times 10^{-7}$ in decimal notation is $0.00000016$.

Would you like more details or have any questions? Here are some related questions you might find interesting:

1. What other numbers can be expressed in scientific notation?
2. How do you convert larger numbers from scientific notation to decimal?
3. Can you explain why scientific notation is useful?
4. What is the significance of negative exponents?
5. How do you perform calculations using numbers in scientific notation?

Tip: When dealing with very small numbers, scientific notation helps keep track of the number of zeros and makes calculations easier.