This figure shows frames from a computer simulation of star formation, starting at the left with a large molecular cloud measuring more than a light-year across. What is happening as time passes (from left to right)?
A) The cloud is fragmenting into smaller pieces that will form stars.
B) The cloud is developing hot spots that shine more brightly within it.
C) Magnetic fields are forcing the gas to align in intricate ways along twisted magnetic field lines.
D) The cloud has been hit by a shock wave from a nearby stellar explosion, which causes the gas to move violently around.
A) The cloud is fragmenting into smaller pieces that will form stars.
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Vision Problems: Mahmood is farsighted and cannot see objects clearly that are closer to his eye than 80.0 cm. What is the focal length of the contact lenses that will enable him to comfortably see objects at a distance of 25.0 cm from his eyes?
A. +36.4 cm B. -36.4 cm C. -21.2 cm D. +21.2 cm E. +32.5 cm
Which of the following best describes the situation according to Jackie?
A) She stays still, while Earth rushes away from her at 0.9999c and Vega rushes toward her at 0.9999c. Since Vega is 25 light-years away, she says it takes Vega about 25 years to reach her. B) She stays still, while Earth rushes away from her at 0.9999c and Vega rushes toward her at 0.9999c. She sees the distance from Earth to Vega shortened considerably from 25 light-years, and therefore it takes far less than 25 years for Vega to reach her. C) She says that the 25-light-year trip takes only a few months and therefore concludes that she is traveling faster than the speed of light. D) She's taking a trip that takes 25 years from Earth to Vega.
The depth of the dip in a star's brightness due to the transit of a planet depends most directly on
A) the planet's density. B) the eccentricity of the planet's orbit. C) the planet's size. D) the size of the planet's orbit. E) the planet's mass.
With daytime temperatures that can reach 430°C, why is nighttime on Mercury so cold?
A) Because the year is so short, there isn't enough time for the heat to build up in the equatorial regions. B) With very little atmosphere, heat is quickly lost back into space. C) The weak gravitational field doesn't retain the daytime's heat. D) The solar winds quickly dissipate all heat on the planet's dark side.