how have scientists determined that the outer of earth liquid?

Answer 1

If what you mean is "how have scientists determined that the earth's mantle is fairly solid (though deformable) rock and the outer core is liquid metal," then the answer is this.

Shock waves (as from earthquakes) travel through the earth in two ways, called P (or primary) waves and S (or secondary) waves. P waves can travel through solids or liquids. Both kinds of waves can be bent, or refracted, when they hit a boundary between liquid and solid. They also travel at different speeds; P waves are faster than S waves.

When an earthquake strikes, scientists can collect seismograph readings from different points and see if P waves, S waves, or both arrived, and measure the time lag between the P and S waves. By doing this they have determined approximately where the earth's interior is solid and where it is liquid, because they know that the liquid portions don't transmit S waves and as a result some locations pick up P waves, but no S waves, from a distant earthquake.

Answer 2

Satellites have detected water on the surface.
They estimate that about nine tenths of the surface in water
I guess you will just have to take their word for it.

Answer 3

seismography, sonar, computer generated mapping using incredibly sophisticated instruments. Stuff like that.

Answer 4

Try rephrasing the question. Then, people might understand you and you might get som real answers.

Answer 5

Mostly natural and artificial seismography.

Doug