Aug. 21, 2017, may be one of the worst traffic days in national history, some NASA representatives predict. Although about 12 million people live within the narrow band of totality, approximately 25 million reside within a day's drive of it, and the agency has estimated that the population inside the path of totality may double on the day of the eclipse.
With that in mind, make sure you plan for extra travel time, especially on the day of the eclipse. Most hotel rooms inside the path of totality have been booked for months or years, so you may not be able to stay inside the path the night before.
When selecting a location where you plan to view the eclipse, keep in mind your proximity to food, water, parking and facilities. Attending an organized eclipse event is an ideal way to make sure those things are close by. Traveling even short distances could be difficult in some areas, and midday in the middle of August can mean punishing heat in many parts of the country.
Anyone planning to view the total solar eclipse of 2017 should get a pair of solar viewing glasses. These protective shades make it possible for observers to look directly at the sun before and after totality. The following four companies sell eclipse glasses that meet the international standard (ISO 12312-2) recommended by NASA, the AAS and other scientific organizations: Rainbow Symphony, American Paper Optics, Thousand Oaks Optical, Lunt Solar Systems and TSE 17.
Binoculars are helpful for seeing more detail in the solar corona. Telescopes are not necessary, but some skywatchers may use low-powered telescopes to observe the sun's atmosphere during totality. Note that telescopes, binoculars and cameras must be fitted with solar filters before and after totality. Pointing an unprotected lens directly at the sun can damage the instrument. NEVER look at the sun through binoculars, a telescope or a camera lens without a solar filter -- the magnified light can damage your eyes faster than looking at the sun unaided.
Skywatchers outside the path of totality will still be able to see a partial solar eclipse. Solar viewing glasses allow skywatchers to look directly at the moon's progress across the face of the sun. You can also view the progress of a partial solar eclipse using a pinhole camera.
At most, the moon will completely cover the disk of the sun for 2 minutes and 40 seconds. That's about how long totality will last for observers positioned anywhere along the center of the path of totality. As you move toward the edge of the path, the duration of totality will decrease. People standing at the very edge of the path may observe totality for only a few seconds.
The chart below lists the moment of mid-totality and the duration of totality for a handful of cities that lie close to the center of the path.
Because the shadow of the moon will move from west to east, totality will occur later in the day the farther east you travel. Use the NASA interactive eclipse map to find out exactly when totality will occur and how long it will last in the location where you plan to observe the eclipse. Just click on a spot on the map, and an informational box will appear with specific times.
But Zeiler added that his numbers could be altered by a number of other factors, such as the heavy promotion of the eclipse on social media sites (including Space.com's accounts), the ever-changing weather conditions along the eclipse path, and the possibility of western wildfires producing widespread smoke that could hinder visibility and force eclipse viewers to head farther east. There are also major regional events that may prove attractive. For instance, Zeiler said, "a very large eclipse-viewing event at St. Joseph, Missouri, will draw visitors from Kansas, Nebraska and [other] nearby states."
And lastly, Zeiler pointed out that his calculations do not take into account potential viewers from other countries, most notably Canada and Mexico, but also Europe, Asia or other international regions. Needless to say, taking all of these things into account, his estimate of between 1.85 million and 7.4 million people traveling to view the eclipse could be conservative to say the least!
Zeiler, who created the fantastic website GreatAmericanEclipse.com, has taken the time to specifically look into the potential number of people who will travel into the total eclipse path. He has done a statistical study of the numbers of people that he believes will make an effort to see the total eclipse. On the positive side, Zeiler points out that there should be plenty of room inside the predicted corridor of darkness for these visitors — provided people distribute themselves well.
"The problem," notes Zeiler, "is that these millions of Americans will produce predictable traffic congestion. …. Large numbers of visitors will overwhelm lodging and other resources in the path of totality. There is a real danger during the 2 minutes of totality that traffic still on the road will pull over at unsafe locations with distracted drivers behind them."
As for how many people will migrate into the totality path, Zeiler has calculated that an average person living 200 miles away from the totality path has a high probability of 2 percent to drive into the path and a low probability of 0.5 percent. For people living 400 miles (640 km) away, Zeiler cut these numbers in half. For those living 800 miles (1,300 km) away, he halved these numbers again. His subjective sum estimate from this analysis is that between 1.85 million and 7.4 million people will visit the path of totality on eclipse day.
A planned special event for which there has been no recent precedent in the United States
A planned special event that is a feat of nature and not human-made
A planned special event with many different events across the country
An act of nature that is not a disaster
"Travelers should be at their observation location a minimum of a couple hours before totality," advised the Federal Highway Administration. "The role of state and local DOTs may include instituting roadblocks or other measures to keep people from making illegal turns as they drive around looking for 'the perfect spot' as eclipse totality nears."
And there is also anticipation of a mass exodus: "Departures will be more compressed as there is no reason to remain after the period of totality has passed."