the ground.
4 feet
Generally about the same as the height of the plant. [see related links]
You should plant it 15 inches apart.
You should plant them 3 inches apart.
well it depends on the seed. like if you plant corn it has to be 8-12 in. apart or you can just look on the back of the seed packet.
Potatoes don't spread out very far underground. The root where the potatoes grow, mostly goes straight down. You can plant lots of other vegetables nearby.
You should plant them arond 3-4m apart
its over 9000
15cm should be fine
They should have their own amount of space so they can grow properly and so the roots don't get tangled under ground, they also need the right amount of space so they grow to their full height if they don't have the right space they will not grow to their approximate height.
50 feet
Rows should be spaced 12" apart and the seeds within the rows should be planted 3" apart. Once the plants are growing, transplant the seedlings, making sure each plant has 6" of space on both sides.
As far as is known to the public, the only non-plant living things to have been launched into space so farhave been dogs, monkeys, insects, fish, and people. No known horse has so far been launched.