how can people be truely sure what's inside of earth if they've never been there?

Answer 1

The old professor says: As one who has been active in the research of planetary formation, early solar system environs, etc., I feel I can speak with authority.

First, the only way to be "truely sure" is to go there and see for yourself. (Even then you would have to believe what you saw). Since this is obvously impossible at present, we have to work with remote sensing technology, known laws of physics, and models that fit the facts.

The newtonian laws of gravity and Kepler's observations enable us to calculate the mass of the Earth. Other measurements give us the size; primary requirements for us to start building our model.

Now, where I come in..."How do we know what materials are deep down there?" Our knowledge of crustal content is pretty well understood, for obvious reasons. Upper mantle material is extruded at places like the mid-ocean rift zones. Although this material is somewhat altered by time we get it for study, it gives us enough clues to determine its original content, etc. But, what about the deeper stuff...the inner and outer core and deep mantle? Well, the study of seismic (earthquake) wave patterns as they travel through the planet gives us a pretty good idea of the sizes of these inner zones.
Since some waves cannot travel through the solid core, a "shadow zone" is produced on the side of the Earth opposite the quake focus where seismometers do not detect these waves. Refractive patterns of the waves give us clues as to the size of the other zones.

The compostion is determined from meteorite studies (my research areas) We are quite sure the Earth was formed from an accretion disk about the early sun. The planet is still growing by accumulating leftovers from this disk. If we were to take a representative amount of meteorite material, place it in a sealed container and melt it, the following would occur. First the volitiles would come off. These are the gases and water steam we find on our planet. Next the minerals and iron/nickel fragments would melt. The most dense materials would sink to the bottom (Fe and Ni plus heavy elements) and the silicate minerals (mantle stuff) would lay over this metallic lowermost layer (core). So you see here, we have layering based on density segregation. The relative thicknesses of these layers in the molten mass correspondes to that of our model of the Earth. The composition also gives us the correct mass (proportion wise) to fit the mass of our scale model.

It all fits together to satisfy those laws of physics and our observations of the planet's behavior. I would say, at present, we are about 98% sure of our conclusions.

Answer 2

Three centuries ago, the English scientist Isaac Newton calculated, from his studies of planets and the force of gravity, that the average density of the Earth is twice that of surface rocks and therefore that the Earth's interior must be composed of much denser material. Our knowledge of what's inside the Earth has improved immensely since Newton's time, but his estimate of the density remains essentially unchanged. Our current information comes from studies of the paths and characteristics of earthquake waves travelling through the Earth, as well as from laboratory experiments on surface minerals and rocks at high pressure and temperature. Other important data on the Earth's interior come from geological observation of surface rocks and studies of the Earth's motions in the Solar System, its gravity and magnetic fields, and the flow of heat from inside the Earth.

The planet Earth is made up of three main shells: the very thin, brittle crust, the mantle, and the core; the mantle and core are each divided into two parts. All parts are drawn to scale on the cover of this publication, and a table at the end lists the thicknesses of the parts. Although the core and mantle are about equal in thickness, the core actually forms only 15 percent of the Earth's volume, whereas the mantle occupies 84 percent. The crust makes up the remaining 1 percent. Our knowledge of the layering and chemical composition of the Earth is steadily being improved by earth scientists doing laboratory experiments on rocks at high pressure and analyzing earthquake records on computers.

Answer 3

it's called Science by people who seek answers by investigation not a keyboard. There are many answers to your questions.

Calculations so intense only modern computers can cope with it are part of it.

There's also a group called the Joint Science Foundation, existing for more than 20 years, comprised of 23 different countries, operating a drill ship called the "Joides Resolution" drilling/coring holes in the sea floor at 29,000 foot water depth to find the Mantle. (Do you know what that is?) And now they have found it.

Where do you come off asking stupid questions challenging talented people, not all college educated, because you don't have the motivation to search? You sit back with authority and say, "Answer Me, Duh"

Go for it Homer. If you are really interested the answer is there. Your generation has the ability to witness a dust storm on Mars. Have you seen that?

Get real. Match your interest with your capability. I hope you can find a match. It took me a grunch of years to figure out it was my issue.

Do It

Answer 4

Yeah...it's just a theory based on volcanoes and metals and stuff. But what if there are aliens waiting for us and they plan to invade the Bejing Olympics in 2008...
There was a interesting article in a edition of Muse printed last year, it's about all these different people that suggested different theories about the earth...one said the earth was a donut, one said we lived inside the earth...

Answer 5

You should know that scientists are not truly sure. Even though they sometimes talk like it. Keep this in mind. But you can apply the principles of physics and make reasonable theories. We would love to drill a real deep hole. It has been hard. My understanding is that efforts have been abandoned for the present.