Detailed Instructions: You are given a paragraph, with numbered sentences, and a question. Write the numbers of the sentences needed to answer the given question. Separate multiple sentence numbers with a comma (", "). E.g. "1, 2" would be the correct response if Sent 1 and Sent 2 are needed to answer the given question (do not include sentences that contain no information that is necessary to answer the question). Sort the sentence numbers in an increasing order (i.e., '1, 2', instead of '2, 1'). Your answer should not contain anything than the sentence numbers separated by a comma (e.g. '1, 2, 3, 4'). The given question requires more than one sentence to answer. So, your answer must contain at least one comma (", ").
Q: Paragraph- Sent 1: How would the universe look without gravity?
Sent 2: It would have no planets and no stars.
Sent 3: Thats how it looked when it was young.
Sent 4: When the universe was young, there was only gas and dust.
Sent 5: From this gas and dust, everything we now see was made.
Sent 6: How were stars and planets created from just gas and dust?
Sent 7: The answer is gravity.
Sent 8: The same gravity that holds you down on Earth.
Sent 9: The same force that causes your pencil to roll off your desk.
Sent 10: The same force that causes it to fall to the floor.
Sent 11: The invisible force of gravity caused dust and gas particles to be pulled together.
Sent 12: This force is what formed all the objects in our solar system.
Sent 13: This force formed the smallest moons.
Sent 14: It also formed our Sun.
Sent 15: This force caused more than just our solar system to form.
Sent 16: It caused all the other solar systems to form.
Sent 17: It caused the formation of all the galaxies of the universe. 
Question: What does gravity do to the universe?.
A:
6, 7, 11.