A Galaxy Is Observed Receding from Earth with a Speed

question 22

Multiple Choice

A galaxy is observed receding from Earth with a speed of 2800 km/s. If the Hubble constant is 22 km/s per million light-years, estimate how many years ago the light that we presently see from the galaxy actually left the galaxy. (c = 3.00 × 10⁸ m/s, 1 ly = 9.461 × 10¹⁵ m, 1 y = 3.156 × 10⁷ s)

• A) 1.3 × 10⁸ y
• B) 4.2 × 10⁸ y
• C) 4.2 × 10⁷ y
• D) 1.4 × 10⁷ y
• E) 4.2 × 10⁶ y

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Definitions:

Parkinson Disease

A neurodegenerative disorder characterized by motor symptoms such as tremor, stiffness, and slowed movement, due to the death of dopamine-producing cells.

Posttraumatic Stress Disorder (PTSD)

Syndrome characterized by physiological arousal associated with recurrent memories and dreams arising from a traumatic event that occurred months or years earlier.

Nigrostriatal Dopamine System

A pathway in the brain involved in movement control and regulation, often associated with conditions like Parkinson's disease when dysfunctional.

Lesions

Areas of tissue that have been damaged through injury or disease, affecting the function of the part.