If one is behind the other and is swimming between the tail you will see him spit out eggs and he is sucking them out to fertilize them. If there are no eggs then perhaps they are just close and happy :)
Yes. Separate them.
If the goldfish is swimming in water, it is alive.
everyday for a year! (24/7) ...............enjoywell for goldfish in any kind of outdoor pond , mating season is in spring mostly in April.
Swim bladder disease? http://www.straightdope.com/columns/read/1688/if-a-goldfish-is-swimming-on-its-side-is-this-a-bad-sign
it stops swimming
Yes
Well if she is not sepperated from her eggs she will begin eating them.
The female lays eggs, which are fertilized outside the body of the female. Goldfish do not have sexual intercourse.
In a word, no. It would be like mating a hummingbird with a wombat...
Gravity
No!
They could be mating or just trying to play with eachother.