What did the night sky seem like for Benjamin Franklin, Thomas Jefferson, and their contemporaries on July 4, 1776?
As the USA marks its 250th birthday, many astronomy fanatics could also be asking precisely that. For those who stepped outdoors round 9 p.m. native time on July 5, 1776, the sky would look a lot because it does at this time. Solely cautious measurements would present that the celebrities weren’t in fairly the identical positions they occupy in 2026.
To grasp the sky extra absolutely, it helps to have a look at how individuals in 1776 tracked celestial occasions and what they might have anticipated to see overhead.
However first, how did individuals in 1776 hold monitor of astronomical phenomena? Individuals studied astronomy for sensible causes each out and in of the classroom. It was important for navigation, surveying, timekeeping, and charting unfamiliar lands. In an age earlier than gentle air pollution, bizarre individuals had been additionally probably way more accustomed to the stars and constellations than most people are today.
In the American colonies of the 17th and 18th centuries, an almanac ranked simply behind the Bible in on a regular basis significance. It listed dawn and sundown, moonrise and moonset, the instances when brilliant stars reached their highest factors within the sky, lunar phases, planetary positions, some astrological lore, and sensible info equivalent to street situations, husbandry ideas, and climate forecasts.
By the early 18th century, numerous almanacs were in print. Many survived only a few years, but a bestseller could support its printer well into the following year. Among the most successful was Benjamin Franklin’s “Poor Richard’s Almanack“, printed in Philadelphia beneath the pseudonym Richard Saunders from 1732 to 1758. It turned immensely widespread, promoting greater than 10,000 copies yearly. Franklin has typically been known as America’s first true Renaissance man — an creator, printer, politician, diplomat, inventor, and scientist who counted astronomy amongst his pursuits.
Later, yearly “prospectuses of the sundry celestial occasions” may very well be derived from the intensive calculations showing in “The Nautical Almanac”, established in 1766 by Dr. Nevil Maskelyne, the fifth Astronomer Royal of England.
The planets seen over the U.S. in 1776
For anybody consulting an almanac for the 12 months 1776, they might discover that just one planet may very well be readily seen after sunset. Saturn, in the constellation Virgo, passed opposition to the sun on April 7 and during July would be evident in the southwest sky at dusk, shining with a yellowish-white glow and appearing slightly brighter than the bluish first magnitude star Spica, about 7 degrees to its lower left. On the evening of July 22, a waxing crescent moon would appear to form a broad triangle with Saturn and Spica. Of course, Saturn’s most notable telescopic feature is its ring system, which at the moment was tilted 10 levels from edge-on with its north face in view.
Towards the top of the month, three different planets could be obtainable about 90 minutes earlier than dawn, low within the east-northeast amidst the celebrities of Gemini: Mercury, Jupiter and Mars. Dazzling Venus would be invisible due to its proximity to the sun.
The great lunar eclipse of July 1776
The month’s most anticipated astronomical event was the total lunar eclipse of July 30. By the requirements of most eclipses, it was distinctive: totality would final an unusually lengthy 1 hour 35 minutes. Sadly for observers in Philadelphia, New York, Boston, and lots of different areas, a lot of the spectacle unfolded earlier than moonrise. Mid-totality was predicted for “7:01 o’clock within the night,” earlier than the moon rose, and the moon would start rising from Earth’s shadow at 7:49 p.m., when it was positioned simply above the east-southeast horizon. It will “give up the shadow fully” at 8:48 p.m.
The eclipse got here simply 26 days after the Declaration of Independence was unanimously adopted by the Second Continental Congress in Philadelphia. It was extensively noticed and mentioned in journals of the period and later turned a part of Revolutionary Conflict Lore. In a time of profound uncertainty, early People watched it carefully regardless of poor viewing situations. Diarists and observers, together with hymn author John Newton and militia officers, typically handled the occasion as an omen reflecting the gravity of the Revolution. The Declaration of Independence was engrossed on parchment, and delegates started signing it on Aug. 2, 1776, solely three days after the eclipse.
Past the month’s most dramatic occasion lies a subtler query: whether or not the background stars themselves would have appeared meaningfully completely different from the best way they seem at this time.
Did the celebrities look completely different 250 years in the past?
Apart from rotating and revolving, Earth has an oscillating motion like that of a spinning top due chiefly to the pull of the moon on Earth’s equatorial bulge. Each oscillation takes about 26,000 years. Thus, the North Pole traces a circle in the sky, pointing to different stars as it moves in its circuit.
What about proper motion? Have any stars shifted noticeably in 250 years? The only one would be the brilliant orange star Arcturus in Boötes, which has the largest proper motion of any 1st-magnitude star, but since 1776 has drifted only about 0.13 degrees (equal to about one-quarter of a moon diameter) with respect to its fainter neighbors.
The weather on America’s first Independence Day
One final detail adds historical texture: the weather in Philadelphia on July 4, 1776, was pleasant and mild, with clear morning skies giving way to increasing clouds by afternoon. Weather journals kept by Thomas Jefferson and local observer Phineas Pemberton record a high of 76° F. Those later clouds, however, might have obscured much of the sky on that first night of Independence.
Joe Rao serves as an instructor and guest lecturer at New York’s Hayden Planetarium. He writes about astronomy for Natural History magazine, Sky and Telescope, The Old Farmer’s Almanac and different publications.
