Introduction
Geology is a way to know the content of the earth and how the earth works. This activity is going to show the mass of the earth. The reason is to show how scientists determined the mass of the Earth, and an example of one of the ways to estimate the mass of the earth. Knowing the mass of the earth is important because it helps us to understand what is in the center of the earth, and how the earth operates.

Several historical figures have discovered the mass of the earth. Henry Cavendish is credited as the first person to find the mass of the Earth (Rubin). Eratosthenes calculated the size of the earth in 276 BC. Newton was incremental in calculating the mass of the earth with his equation of gravity (Wile). Today’s known mass of the earth is 5.98*10^24kg or 598 sextillion kilograms (Wile).

One way to can calculate the mass of the earth is by finding the time it takes to rotate around the sun and using the equations of gravity and centripetal force to calculate the mass of the earth. This method takes equipment to calculate the mass of the sun and the velocity which cannot be done in a classroom without the information pre- given in a text book (Wile).

Methods
How can the mass of the earth be estimated? This experiment will show how that can be done. In this experiment the equipment used includes: six rocks given in class to calculate the average density of rocks, a graduated cylinder full of water, a calculator, and an electronic balance.

One of the assumptions that I can make regarding the calculations achieved in the activity include many of the rocks have similar or even the same volume because of their size. Another premise that can be made is the densities are similar in some of the rocks in this activity.

The above assumptions are justified in this experiment because three of the volumes are exactly the same in the calculations and the rocks were the same sizes. The densities are also very similar in some of the samples. The reason being is that the mineral content is similar or exactly the same, but arranged differently. One example of this mineral content is basaltic porphyry and basalt; another is granite and pegmatite. Each of these rocks has the same mineral content, but different particle sizes (Wicander, Monroe).

Results
To determine the mass we placed the first rock on the balance to find its mass and the answer was 25g. Secondly, the rock was placed in water to find the volume, and found the volume was 25mL which makes the density 1 g/mL. Five more rocks were measured in the same way. For the second rock the mass was 50g and the volume was 23mL, making a density of 2.17g/mL. The third rock had a mass was 77g and the volume of 25mL, making a density of 3.08g/mL. On the fourth rock, the mass was 70g and the volume was 25mL, making a density of 2.8g/mL. The mass of the fifth was 33g and the volume was 10mL, making a density of 3.3g/mL. In the final rock the mass was 15g and the volume was 5mL, making a density of 3.0g/mL. The rocks average density is 2.56g/cm3 because you can substitute cm3 for mL since they are equal.

To find the mass of the earth we had to know the densities of the rock and the iron. The rock made up 65% of the earth’s material, and iron made up the other 35%. The density of the iron was given as 7,874 kg/m3.  The density of iron had to be multiplied by .35 to find the final density of iron in the earth. Then the new density (2,756 kg/m3) was multiplied by the given volume, which is 1.08321e21m3 to get a mass of 2.9853e24kg. Next I had to calculate the density of the rock in kg/m3 which ended up as 2,560kg/m3. That density had to be multiplied by .65 to get the density of the total rock of the earth. The answer is calculated as 1,664kg/m3. To get the mass, I multiplied the given volume by the density of the rock, which was calculated as 1.8025e24kg. Finally to get the mass of the earth, the mass of the iron had to be added to the mass of rock. The mass of the earth was found to be 4.78e24kg. 

Table 1
Density in kg/m3 Volume in m3 Mass in kg Mass of the Earth in kg
Rock total in earth 1,664  1.08321e21 1.80246e24
4.78e24
Iron  total in earth 2,756 1.08321e21 2.98533e24

Discussion
The mass of the earth calculated by me compared to the one discovered by real scientists is that mine was 4.78e24kg but the real mass was 5.98e24kg (Wile). The reason for the difference is being the water was not part of the calculation. Also what would play into this would be the amount of rocks used. It would change the density of the earth because all rocks have different densities, and the more rocks used the more accurate the density will be. Another factor is how we calculated using a geologic equation while scientists used the gravitational pull of the sun and Newton’s equations on gravity to find the mass of the earth.

Ways I could improve my results include using more rocks to make a more precise average density of rocks in the earth to find a closer answer. In addition, the density of water could also be used since water also takes up a huge amount of the earth. Another way that would work is finding the density of nickel since there is a significant amount of nickel in the center of the earth, which would give a more accurate mass.

Conclusion
In conclusion, in this activity the densities of various rocks were calculated, then averaged. The given information was used to calculate the mass of the iron portion of the earth. After that, the mass of the rock portion of the earth was calculated. Then both of those masses were added together to give the total mass of the earth.

References
“Eratosthenes: Greek Scientist.” 9-30-16.
Rubin, Julian. “Henry Cavendish: Weighing the Earth.” June 2013.

Wile, Jay L. Exploring Creation with Physics. Anderson, IN: Apologia Educational Ministries,  2004. Print.
Wicander, Reed, Monroe, James S. Belmont, CA: Brooks/Cole, Cengage Learning, 2013