NEW YORK—Millions of eyewitnesses watched in stunned horror Tuesday as light emptied from the sky, plunging the U.S. and neighboring countries into darkness. As the hours progressed, conditions only worsened.

Satellite view at 4:50 p.m. EST shows the sun disappearing from the sky.

At approximately 4:20 p.m. EST, the sun began to lower from its position in the sky in a westward trajectory, eventually disappearing below the horizon. Reports of this global emergency continued to file in from across the continent until 5:46 p.m. PST, when the entire North American mainland was officially declared dark.

As the phenomenon hit New York, millions of motorists were forced to use their headlights to navigate through the blackness. Highways flooded with commuters who had left work to hurry home to their families. Traffic was bottlenecked for more than two hours in many major metropolitan areas.

Across the country, buses and trains are operating on limited schedules and will cease operation shortly after 12 a.m. EST, leaving hundreds of thousands of commuters in outlying areas effectively stranded in their homes.

Despite the high potential for danger and decreased visibility, scientists say they are unable to do anything to restore light to the continent at this time.

"Vast gravitational forces have rotated the planet Earth on an axis drawn through its north and south poles," said Dr. Elena Bilkins of the National Weather Service. "The Earth is in actuality spinning uncontrollably through space."

Bilkins urged citizens to remain calm, explaining that the Earth's rotation is "utterly beyond human control."

"The only thing a sensible person can do is wait it out," she said.

Commerce has been brought to a virtual standstill, with citizens electing either to remain home with loved ones or gather in dimly lit restaurants and bars.

"I looked out the window and saw it getting dark when I was still at the office working," said Albert Serpa, 27, a lawyer from Tulsa, OK, who had taken shelter with others at Red's Bar and Grill. "That's when I knew I had to leave right away."

Ronald Jarrett, a professor of economics at George Washington University who left his office after darkness blanketed the D.C. metro area, summed up the fears of an entire nation, saying, "Look, it's dark outside. I want to go home," and ended the phone interview abruptly.

Businesses have shut their doors, banks are closed across the nation, all major stock exchanges have suspended trading, and manufacturing in many sectors has ceased.

Some television stations have halted broadcasting altogether, for reasons not immediately understood.

Law-enforcement agencies nationwide were quick to address the crisis.

Houston-area victims flee their workplaces ahead of the growing wave of darkness.

Said NYPD spokesman Jake Moretti: "Low-light conditions create an environment that's almost tailor-made for crime. It's probably safe to say we'll make more arrests in the next few hours than we have all day."

Darkness victims describe hunger pangs, lassitude, and a slow but steady loss of energy, forcing many to lie down. As many as two-thirds of those believed afflicted have fallen into a state of total unconsciousness.

Many parents report that their younger children have been troubled, even terrified, by the deep darkness. To help allay such fears, some parents are using an artificial light source in the hallway or bedroom.

As of 2 a.m. EST, the continent was still dark, the streets empty and silent. However, some Americans remained hopeful, vowing to soldier on despite the crisis.

"I don't plan on doing anything any different," said Chicago-area hospice worker Janet Cosgrove, 51. "I'm going to get up in the morning and go to work."