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According to General Relativity, what is gravity?

Suppose you are on a spaceship flying away from Earth at 0.5c. You are communicating with your friend on Earth by radio. What will your friend notice about your rate of speech?

Order the following energy types by their abundance in the Universe.

Whatever is causing the Universe’s expansion to accelerate is called [de]. The unseen source of gravity that causes galaxies to cluster together is called [dm]. 

According to experiment, which interpretation correctly describes the fundamental nature of reality?

If I know a particle’s velocity extremely precisely, I can know its position [b]. If I know a particle’s position extremely precisely, I can know its velocity [a].  

Suppose an electron in an atom jumps from energy level 2 to energy level 4. Where does the extra energy come from?

A 45-year-old man presents with progressive clumsiness, stating he often drops objects and recently has had difficulty performing tasks requiring fine motor coordination, such as hammering a nail. He also reports that his speech has become slurred, and his legs occasionally feel weak. He denies visual or cognitive changes. A chronic degenerative disease of the central nervous system involving predominantly motor neurons is suspected. Which of the following is the most likely diagnosis?

A 40-year-old administrative assistant presents with daily headaches that she describes as a dull, pressure-like pain around the forehead and occipital area. The pain is bilateral, non-pulsatile, and is not associated with nausea, vomiting, photophobia, or aura. She notes that the headaches often begin in the afternoon and are worse during periods of stress. Over-the-counter analgesics provide some relief. What is the most likely patient’s diagnosis?

Which of the following neurologic disorders is characterized by cortical nerve cell processes that have become twisted and dilated, commonly referred to as neurofibrillary tangles?