The Earth’s Shape and Gravity

DSVS Spring 2011Sixth Grade

Lab 1

Important

• Please use this resource to reinforce your understanding of the lesson! Make sure you have read and understand the entire lesson prior to picking up the kit!

• We recommend that you work through the kit with your team prior to going into the classroom.

• This presentation does not contain the entire lesson—only selected experiments that may be difficult to visualize and/or understand.

Set up• Pass out globes (or balls) with

bowls or rolls of tape so that the globes will not roll of the tables.

• Pass out the questionnaire “What are your ideas about the earth” and allow 10-15 mins for the students to answer the questions

• Ask for some students to offer their answers to some of the questions, and ask them to explain why they answered that way.

Questionnaire

There will be easy to read copies provided

Answers

• Question 1. D. The earth is round like a ball but it looks flat because we see only a small part of it

• Question 2. D. Downward• Question 3. The correct answer shows each rock falling straight

down, landing next to the persons feet. Gravity always pulls objects towards the center of the earth. Therefore, down is always toward the center of the earth.

• Question 4. From the rocks point of view, down is always the center of the earth. Before it reaches the center of the earth, the rock keeps going faster and faster because it is still falling “down”. It only starts slowing after it passes the center, because then the greater mass of the earth is behind it.

Discussion about the Earth• Gravity

– Gravity is the force of attraction between all masses in the universe; especially the attraction of the earth's mass for bodies near its surface

– It is important for it hold the entire universe together, holds us and everything to the surface of the earth– The Force of gravity is Mass dependent. Objects of greater mass will have a stronger gravitational force.

• If you dropped a rock on the surface of Mars and the surface of earth, which would hit the ground first and why?• Because Mars is only about one tenth the size of earth, it has lower gravity, so the rock will hit the ground first on Earth.

• What did ancient scientists used to think about the earth? Why?– The used to think that the Earth was flat. From our point of view, the earth appears flat because we are

only seeing a very small portion of it.

• If you dug a hole right through the center of the earth from where you are right now, where would you end up?– (tell them they can look at the globe) China because the earth is ROUND

Rotation and Seasons

• How are rotation and revolution different?– Earth rotates on its axis as it revolves around the sun

• What is a day?, a month?, a year? What determines these time periods?– Day- time for Earth to make a complete rotation on its axis, month-is the

time between two identical new moons, and a year-the time it takes a planet to orbit the sun once- for earth, 365 days.

• Is a year the same on Mars as it is on earth? Mars is one and a half times as far away from the Sun as Earth. Therefore, It takes longer for Mars to make one full orbit around the sun. The length of a Martian year is about 687 days.

• Is the Earth rotating straight up an down? Or at a tilt? What does this mean for the four seasons?

• The earth rotates towards the east on a tilt. Because the Earth is not rotating straight up and down (demonstrate using a globe), sometimes different places (hemispheres) are at different angles to the sun. When a certain place on the earth is closer to the sun, it is summer, when it is farther away, it is fall.