I need all or some answers to these questions

1. it`s due to the gravitational pull of earth which causes Moon to orbit the Earth.

2. No,it`s not always noticeable.You must have heard that earth pulls apple so it falls downward but the fact is apple also pulls earth but the pull isn`t noticeable.

3. I have only one thing that is the distance between the masses.

4. The quantity of matter contained in a body is called it`s mass whereas weight of an object is the force of attraction with which it is attracted towards the centre of a planet.Mass of an object is constant everywhere bt weight of an object varies from place to place.Mass is measured by beam balance whereas Weight is measured by spring balance.

5. You will fall back on the surface of earth.It happens because of the force of gravity of the earth.

6. If u jump on the moon u will float away(I guess).

7. Weightlessness is a condition where weight of an object is experienced to be zero.The mass doesn`t change as it remains constant everywhere.I will add an image for this one which may help you.

*if a hydrogen emission line is observed in the galaxy, this implies that the galaxy has a significant amount of a chemical element

*difference between the two wavelengths e can be explained by the relativistic Doppler effect

Explanation:

The emission of the materials depends on the distribution of the electrons around the atoms and their possible transitions. These emissions are maintained even when the element is mixed in some compound.

Consequently, if a hydrogen emission line is observed in the galaxy, this implies that the galaxy has a significant amount of a chemical element.

The small difference between the two wavelengths e can be explained by the relativistic Doppler effect, due to the movement of the galaxy