Why is the planet Mercury difficult to see from Earth?
Why does Mercury have an average density that is close to that of earth even though Mercury is a smaller planet?
It is difficult to see Mercury as it is so close to the sun and inside Earths own orbit. From Earth it never appears far from the sun, either directly behind it or in front of it - you can only see it just after sunset or before sunrise. It is difficult to see due to the brightness of the sky at this time.
Yes. You could probably see all of the planets that you see from Earth as well as Earth itself. You might also be able to see Uranus as well from the night side of Mercury. Uranus is generally too faint to be seen from Earth but Mercury, which would not be much farther away from than Earth is, has no atmosphere to distort or obscure light from the planet.
This question is difficult to answer as both Earth and Mercury are moving in orbits round the Sun. This means that at some times Earth and Mercury are on opposite sides of the Sun and at some times they are on the same side. Thus when you try and send a spacecraft form Earth to Mercury you have to plan for how the earth is moving, how Mercury is moving (where it will be when…
The planet Mercury spins very slowly, once every 58.646 Earth days. It orbits the Sun very rapidly, once every 88 Earth days. The combination of these motions leads to an unusual situation. The length of a "solar day" (sunrise to sunrise) on Mercury is 176 Earth days, or twice as long as the year. (See related questions)