MS-ESS1-2 Develop and use a model to describe the role of gravity in the motions within galaxies and the solar system. Clarification Statement: Emphasis for the model is on gravity as the force that holds together the solar system and Milky Way galaxy and controls orbital motions within them. Examples of models can be physical (such as the analogy of distance along a football field or computer visualizations of elliptical orbits) or conceptual (such as mathematical proportions relative to the size of familiar objects such as students’ school or state).

MS-ESS1-3 Analyze and interpret data to determine scale properties of objects in the solar system.                                       Clarification Statement: Emphasis is on the analysis of data from Earth-based instruments, space-based telescopes, and spacecraft to determine similarities and differences among solar system objects. Examples of scale properties include the sizes of an object’s layers (such as crust and atmosphere), surface features (such as volcanoes), and orbital radius. Examples of data include statistical information, drawings and photographs, and models.

By the end of grade 8. Patterns of the apparent motion of the sun, the moon, and stars in the sky can be observed, described, predicted, and explained with models. The universe began with a period of extreme and rapid expansion known as the Big Bang. Earth and its solar system are part of the Milky Way galaxy, which is one of many galaxies in the universe.

By the end of grade 8. The solar system consists of the sun and a collection of objects, including planets, their moons, and asteroids that are held in orbit around the sun by its gravitational pull on them. This model of the solar system can explain tides, eclipses of the sun and the moon, and the motion of the planets in the sky relative to the stars. Earth’s spin axis is fixed in direction over the short term but tilted relative to its orbit around the sun. The seasons are a result of that tilt and are caused by the differential intensity of sunlight on different areas of Earth across the year.

Evidence Statements

MS-ESS1-2 

1. Components of the model 

   1. To make sense of a given phenomenon, students develop a model in which they identify the relevant components of the system, including:

      1. Gravity.

      2. The solar system as a collection of bodies, including the sun, planets, moons, and asteroids.

      3. The Milky Way galaxy as a collection of stars (e.g., the sun) and their associated systems of objects.

      4. Other galaxies in the universe.

   2. Students indicate the relative spatial scales of solar systems and galaxies in the model.

2. Relationships

   1. Students describe the relationships and interactions between components of the solar and galaxy systems, including:

      1. Gravity as an attractive force between solar system and galaxy objects that:

         1. Increases with the mass of the interacting objects increases.

         2. Decreases as the distances between objects increases.

      2. The orbital motion of objects in our solar system (e.g., moons orbit around planets; all objects within the solar system orbit the sun).

      3. The orbital motion, in the form of a disk, of vast numbers of stars around the center of the Milky Way.

      4. Our solar system is one of many systems orbiting the center of the larger system of the Milky Way galaxy.

      5. The Milky Way is one of many galaxy systems in the universe.

3. Connections

   1. Students use the model to describe that gravity is a predominantly inward-pulling force that can keep smaller/less massive objects in orbit around larger/more massive objects.

   2. Students use the model to describe that gravity causes a pattern of smaller/less massive objects orbiting around larger/more massive objects at all system scales in the universe, including:

      1. Gravitational forces from planets cause smaller objects (e.g., moons) to orbit around planets.

      2. The gravitational force of the sun causes the planets and other bodies to orbit around it, holding the solar system together.

      3. The gravitational forces from the center of the Milky Way cause stars and stellar systems to orbit around the center of the galaxy.

      4. The hierarchy pattern of orbiting systems in the solar system was established early in its history as the disk of dust and gas was driven by gravitational forces to form moon-planet and planet-sun orbiting systems.

   3. Students use the model to describe that objects too far away from the sun do not orbit it because the sun’s gravitational force on those objects is too weak to pull them into orbit.

   4. Students use the model to describe what a given phenomenon might look like without gravity (e.g., smaller planets would move in straight paths through space rather than orbit a more massive body).

MS-ESS1-3

1. Organizing data

   1. Students organize given data on solar system objects (e.g., surface features, object layers, orbital radii) from various Earth- and space-based instruments to allow for analysis and interpretation (e.g., transforming tabular data into pictures, diagrams, graphs, or physical models that illustrate changes in scale).

   2. Students describe that different representations illustrate different characteristics of objects in the solar system, including differences in scale.

2. Identifying relationships

   1. Students use quantitative analyses to describe similarities and differences among solar system objects by describing patterns of features of those objects at different scales, including:

      1. Distance from the sun.

      2. Diameter.

      3. Surface features (e.g., sizes of volcanoes).

      4. Structure.

      5. Composition (e.g., ice versus rock versus gas).

   2. Students identify advances in solar system science made possible by improved engineering (e.g., knowledge of the evolution of the solar system from lunar exploration and space probes) and new developments in engineering made possible by advances in science (e.g., space-based telescopes from advances in optics and aerospace engineering).

3. Interpreting data

   1. Students use the patterns they find in multiple types of data at varying scales to draw conclusions about the identifying characteristics of different categories of solar system objects (e.g., planets, meteors, asteroids, comets) based on their features, composition, and locations within the solar system (e.g., most asteroids are rocky bodies between Mars and Jupiter, while most comets reside in orbits farther from the sun and are composed mostly of ice).

   2. Students use patterns in data as evidence to describe that two objects may be similar when viewed at one scale (e.g., types of surface features) but may appear to be quite different when viewed at a different scale (e.g., diameter or number of natural satellites).

   3. Students use the organization of data to facilitate drawing conclusions about the patterns of scale properties at more than one scale, such as those that are too large or too small to directly observe.