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What did the night sky look like on the 1st Independence Day 250 years ago? News
By Joe Rao
Published yesterday
As the U.S. celebrates its 250th birthday, here's what Benjamin Franklin
and other colonists would have seen when they looked up on July 4, 1776.
a building with a tower and a clock on it at night.
Independence Hall in Philadelphia. (Image credit: Wirestock via Getty
Images)
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What did the evening sky look like for Benjamin Franklin, Thomas
Jefferson, and their contemporaries on July 4, 1776?
As the United States marks its 250th birthday, many astronomy
enthusiasts may be asking exactly that. If you stepped outside around 9
p.m. local time on July 5, 1776, the sky would look much as it does
today. Only careful measurements would show that the stars were not in
quite the same positions they occupy in 2026.
To understand the sky more fully, it helps to look at how people in 1776 tracked celestial events and what they would have expected to see overhead.
But first, how did people in 1776 keep track of astronomical phenomena?
People studied astronomy for practical reasons both in and out of the classroom. It was essential for navigation, surveying, timekeeping, and charting unfamiliar lands. In an age before light pollution, ordinary
people were also likely far more familiar with the stars and
constellations than most people are today.
Almanacs: timetables of the heavens
In the American colonies of the 17th and 18th centuries, an almanac
ranked just behind the Bible in everyday importance. It listed sunrise
and sunset, moonrise and moonset, the times when bright stars reached
their highest points in the sky, lunar phases, planetary positions, some astrological lore, and practical information such as road conditions, husbandry tips, and weather forecasts.
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In 1776, the moon was a clock, a calendar and a streetlight rCo and it was
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Title page from a "typical" almanac of the 18th century (1761).
Title page from a "typical" almanac of the 18th century (1761). (Image
credit: Public Domain)
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", published in Philadelphia under
the pseudonym Richard Saunders from 1732 to 1758. It became immensely
popular, selling more than 10,000 copies annually. Franklin has often
been called America's first true Renaissance man rCo an author, printer, politician, diplomat, inventor, and scientist who counted astronomy
among his interests.
Later, yearly "prospectuses of the sundry celestial events" could be
derived from the extensive calculations appearing in "The Nautical
Almanac", established in 1766 by Dr. Nevil Maskelyne, the fifth
Astronomer Royal of England.
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The planets visible over the U.S. in 1776
For anyone consulting an almanac for the year 1776, they would find that
only one planet could be readily viewed after sundown. 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 that time was tilted 10 degrees from edge-on with its north face in view.
night sky graphic showing the constellation Virgo
Looking southwest as darkness fell on July 4, 1776, one could see Saturn
in the zodiacal constellation of Virgo. Saturn was positioned about 7
degrees to the upper right of Virgo's brightest star, Spica. (Image
credit: Graphic created by Joe Rao using Starry Night Pro 8.0/Simulation Curriculum. Background added in Canva Pro.)
Toward the end of the month, three other planets would be available
about 90 minutes before sunrise, low in the east-northeast amidst the
stars 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 standards of most eclipses, it was
exceptional: totality would last an unusually long 1 hour 35 minutes. Unfortunately for observers in Philadelphia, New York, Boston, and many
other locations, much of the spectacle unfolded before moonrise.
Mid-totality was predicted for "7:01 o'clock in the evening," before the
moon rose, and the moon would begin emerging from Earth's shadow at 7:49
p.m., when it was positioned just above the east-southeast horizon. It
would "quit the shadow completely" at 8:48 p.m.
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The eclipse came just 26 days after the Declaration of Independence was unanimously adopted by the Second Continental Congress in Philadelphia.
It was widely observed and discussed in journals of the era and later
became part of Revolutionary War Lore. In a time of profound
uncertainty, early Americans watched it closely despite poor viewing conditions. Diarists and observers, including hymn writer John Newton
and militia officers, often treated the event as an omen reflecting the gravity of the Revolution. The Declaration of Independence was engrossed
on parchment, and delegates began signing it on Aug. 2, 1776, only three
days after the eclipse.
Beyond the month's most dramatic event lies a subtler question: whether
the background stars themselves would have looked meaningfully different
from the way they appear today.
Did the stars look different 250 years ago?
Besides 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.
An illustration of Earth's oscillating motion.
Earth's slight equatorial bulge causes its axis to slowly wobble like a spinning top, tracing a circle across the sky every 26,000 years. As a
result, different stars take turns serving as the North Star. (Image
credit: NASA)
Consequently, Polaris wasn't as good a pole star in 1776, being 1.88
degrees from the celestial pole compared to 0.63 degrees today. Put
another way: the gap between the celestial pole and Polaris measured
nearly four moon-widths in 1776 compared to just over one-width today.
What about proper motion? Have any stars shifted noticeably in 250
years? The only one would be the brilliant orange star Arcturus in
Bo||tes, 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
Weather observations in Philadelphia, recorded by Thomas Jefferson and assisted by Phineas Pemberton, for the first four days of July 1776.
Weather observations in Philadelphia, recorded by Thomas Jefferson and assisted by Phineas Pemberton, for the first four days of July 1776.
(Image credit: NCDC (National Climate Data center))
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 other publications.
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Joe Rao
Joe Rao
Skywatching Columnist
Joe Rao is Space.com's skywatching columnist, as well as a veteran meteorologist and eclipse chaser who also serves as an instructor and
guest lecturer at New York's Hayden Planetarium. He writes about
astronomy for Natural History magazine, Sky & Telescope and other publications. Joe is an 8-time Emmy-nominated meteorologist who served
the Putnam Valley region of New York for over 21 years. You can find him
on Twitter and YouTube tracking lunar and solar eclipses, meteor showers
and more. To find out Joe's latest project, visit him on Twitter.
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