Lesson 1.4

Question 1

proposes that the planets were formed from the material
ejected from the sun during an encounter with another celestial object. This
celestial object could have been another star. The _ theory has several
forms,

Answer 1

encounter theory

Question 2

a passing star termed as intruding star
nearly collided with the protosun. The massive gravitational pull of the intruding
star causes the protosun to eject filaments of material. These materials condensed
into planetesimals from which the planets were formed through accretion. Unlike
the nebular theory which describes Earth starting from molten mass, the
_ theory describes Earth starting from a solid mass smaller than its
present size. The oceans and the atmosphere were formed on Earth through
volcanic activities.

Answer 2

Planetesimal Theory

Question 3

Proponents of the Planetesimal

Answer 3

Thomas Chrowder Chamberlin

Forest Ray Moulton

Question 4

Drawbacks of the Planetesimal Theory

Answer 4

This theory is no longer accepted today due to the fact that hot material from the
sun expands and dissipates rather than contract. In addition, the force from the
passing star will pull dust and gases far away from the sun, that they would not be
able to form the planets in the solar system.

Question 5

explains that the solar system formed as a result of a near
collision between a passing star and the sun. However, unlike the planetesimal
theory, the _ theory proposes that the hot gas from the passing star condensed
into planets instead of condensing into planetesimals. When the star passed near
the sun, the gravitational attraction pulled the mass of dust and gas from the
remaining nebula around the sun. The gas particles then condensed into liquid and
solid states. The particles clump together to form cosmic bodies of different sizes.

These bodies further condensed into planets. Therefore, the interaction from the
gravity of the passing star and the sun led to the formation of the planets in the
solar system. The materials closer to the sun are denser. This explains the positions
of the terrestrial planets near the sun. In contrast, the materials from the passing
star are less dense; thus, explaining the positions of the Jovian planets.

Answer 5

Tidal Theory

Question 6

Proponents of the Tidal Theory

Answer 6

James Jeans

Harold Jeffreys

Question 7

Drawbacks of the Tidal Theory

Answer 7

One problem of the tidal theory is that the hot material from either
star cannot contract. Thus, planets will not form.