The Griffith Observatory has been a major Los Angeles landmark since 1935. It is visited by nearly two million people each year, which is almost half the annual attendance of Grand Canyon or Yellowstone National Parks. The Observatory ranks seventh on the list of major tourist attractions of Southern California. It sits on the southern slope of Mount Hollywood, where it commands a stunning view of the Los Angeles basin below. Thousands of people enjoy the view from its balconies, especially at night.

The Lawn

As you look at the Observatory, you'll see three large copper domes. The one on the right (west) houses the triple-beam solar telescope; the one on the left (east) houses the 12-inch Zeiss Refracting Telescope; the largest dome (at center) houses the planetarium theater. The cupola (front center) holds the pendulum over the Main Rotunda. Access to the roof and the Refracting Telescope is by way of the stairway on either side of the building. Note the romantic art deco style of architecture of the building, which was constructed in 1933-1935.

On the west edge of the lawn is a memorial to James Dean in the form of a bronze bust. Major segments of Rebel Without a Cause were filmed at the Observatory, as have been many motion pictures since.

The Astronomers Monument honors six of the greatest astronomers of all time. They are Hipparchus (?-125 B.C.), Copernicus (1473-1543), Galileo (1564-1642), Kepler (1571-1630), Newton (1642-1727), and Herschel (1738-1822). Click here for a detailed tour of the Monument.

Near the Monument a radio antenna receives signals from weather satellites for display in the museum.

At the base of the Monument is the sundial (left). The fundamental units of time are set by the cycles in the sky, and people have been measuring them since prehistoric time. An Egyptian sundial from 1500 B.C. still exists. The sundial is a link between the sky and our need to measure time, and it's actually a model of the apparent movement of the sun. The sundial charts the progress of the sun across the sky during the day.

The sundial's thick round bar represents the celestial equator, which is the projection of the earth's equator into space. The main axis, a metal rod, lies parallel to the earth's axis of rotation. The sun is south of the celestial equator between September 22 and March 21, and during those six months the shadow falls on the north part of the time indicator.

Note that the sundial doesn't work on the first days of spring or autumn. As our sun crosses the celestial equator, the shadow of the thick bar falls on and hides the time scale. Click sundials for more information.

The Observatory lawn is the best place to view the famous Hollywood Sign.

Hall of Science

There is no charge for admission to the Hall of Science ­ the astronomy museum ­ or to the telescope.

Upon entering the building your attention goes first to the Foucault Pendulum. The pendulum demonstrates that the earth rotates. The 240-lb brass ball, which hangs by a wire 40 feet long, swings in a constant direction while the earth turns beneath it. The pendulum is supported by a bearing that doesn't turn the pendulum as the building rotates with the earth. A ring magnet at the bearing gives a little tug on each swing of the pendulum to keep the pendulum in motion. It is set up by the staff each morning and runs all day. It slowly comes to a stop after the power is turned off at night.

Look up to see the famous Hugo Ballin Murals, completed in 1934. Medieval cathedrals told stories in stone, and these murals tell the story of science in paint. On the ceiling are Atlas, the four winds, and the signs of the zodiac. Other figures include the planets as mythological gods and a comet. The eight rectangular panels show highlights of astronomy, aeronautics, navigation, civil engineering, metallurgy and electricity, time, geology and biology, and mathematics and physics (left to right, starting with the panel opposite the main entrance).

The South Gallery is between the Main Rotunda and the entrance to the planetarium theater. The general theme is planets.

You'll notice the Gravity Well first. Its parabolic shape reproduces the gravitational effect the sun has on the planets (or a planet on its moons). The well has a steeper curvature ("stronger gravity") near the center, and this causes objects to speed up as they approach the center. We might say they move faster near the center because the gravity is stronger there. Einstein would say they move faster because space has a greater curvature. In the gravity well, friction with the surface causes the steel balls to slow down and eventually to fall in; in space there is so little friction that the planets do not move significantly closer to the sun during the lifetime of the solar system. A satellite in low earth orbit feels friction with the upper atmosphere and eventually spirals to the ground, as Skylab did in 1979.

An Orrery sits on the floor to the left (north) of the Gravity Well. An orrery is a device that shows the planets in motion around the sun. This one includes the moon. Notice that the earth's inclination is shown as well, so you can see that the moon generally passes above or below the sun, as seen from earth, rather than directly in front of it. This is a mechanical orrery; a projection orrery is often used in planetarium shows.

The Astroscreen is a large rear-projection screen with a video projector behind it. It promotes the current public planetarium show.

Planet scales are behind the Gravity Well. They show your weight on the earth, moon, Mars, and Jupiter. Although an old exhibit, it remains popular. Notice -- and this is a hard concept -- that your weight depends not only upon the mass of the planet on which you are standing, but also on its size. On small worlds, you stand closer to the center of mass. That's why the sun, with 333,000 times the mass of the earth, has only 28 times the surface gravity. If you compressed the sun's mass into a sphere the size of the earth and stood on it, you would weigh 333,000 times as much as you do here.

Scale models of the planets lie opposite the Astroscreen. You might be surprised at how small the earth is. Jupiter is larger than all the other planets put together. The edge of the sun is shown at the same scale (the sun's diameter is 13 feet).

If you turn at the pendulum and go towards the large Earth Globe, you will be heading down the East Hall and toward the East Rotunda. The exhibits are described in approximately the order you'll come to them.

The Moon Alcove has transparencies of highlights of the Apollo missions to the moon (1969 -1972) on the side walls. When do you think astronauts will return to the moon? A device on the ceiling simulates the phases of the moon (view it from the center of the room). The model shows the change in the moon's appearance 20,000 times faster than it really occurs.

The next alcove interprets the earth from space. At the front of the alcove is the Geochron, a clock that shows the current time everywhere on earth as well as the sunrise and sunset lines. It bears close study. The caption is somewhat technical but it tells you how much information is contained in the Geochron. On the back wall is a display showing current weather pictures of the earth and comparing this with cloud patterns on Venus and Mars.

The Moon Globe is directly across the corridor. The six-foot model shows the entire surface of the moon. If you stand just behind the railing you see the moon as if you were 2,000 miles above its surface. The scale is 30 miles to the inch (20 km per cm). At the same scale, Los Angeles would fit in the palm of your hand. Notice how many craters are a lot more than an inch across! The older part of the moon's surface was saturated with craters about four billion years ago. Each new impact overlapped older craters as it created new ones until it resembled a World War I battlefield. Between four and three billion years ago lava flooded lowlands with dark lava seas. Relatively few craters have formed since, but they look fresher than the others. The mountains are really the curved rims of the largest craters. There is essentially no erosion because there is no air.

The museum now opens into the main east exhibit area. Most of these exhibits are temporary. Here you will find a 1/5 scale model of the Hubble Space Telescope surrounded by many of the spectacular photographs it has taken. (For Hubble photographs on the Web, visit Best of the Hubble Space Telescope or Space Telescope Science Institute).

Two "Planet Odyssey" exhibits let you tour the solar system on your own path and view the best pictures and videos of the planets.

Paintings by Chesley Bonestell -- the most famous space artist of all -- are in two cases against the north wall. Two web sites, http://www.bonestell.com/ and http://www.bonestell.org/ will give you background information on Bonestell and his work.

Among the permanent exhibits is the Camera Obscura (to your immediate left). Camera obscura is Latin for "dark chamber." A large convex lens focuses light from outside the building onto the viewing screen. The image would be upside down, but an overhead mirror turns it right-side-up again. It demonstrates how a lens focuses light to make an image. Renaissance artists used similar devices to make accurate sketches of distant scenes. The camera obscura doesn't admit enough light to work very well at night.

Nearby is "Stargazer," a pair of computers that lets you look at the sky for the dates you select. You might choose to see the sky at the time of your birth, for example, or to preview the next eclipse or planetary conjunction. You can run forward or backward through time through thousands of years. They are based on a program by the same name from Carina Software for Macintosh computers.

To the right and in front of the large raised Earth Globe is the Seismograph. There are actually two seismographs--one in the basement and one on display. The display seismograph, which is visible in the glass case, records vibrations from the floor and displays them on the left drum inside the glass case; it is for demonstration only, and it lets you create your own earthquakes by jumping on the floor. The seismograph in the basement (not accessible to the public) detects long-period waves (the equivalent of low notes) and displays them on the center drum and short-period waves ("high notes"), which are displayed on the drum at right. Low notes travel farther than high notes (which is why ships' fog-horns have such a low pitch). High notes carry more information about things that are close. The three drums turn once every 15 minutes, and the tick marks are one minute apart, so each sheet records for 24 hours. Records of several famous earthquakes are displayed nearby along with interpretative material. In front sits a small cutaway globe showing the earth's interior and the paths of seismic waves. Go to Recent Earthquakes in California for maps and listings of recent local earthquake activity.

The East Rotunda contains the 6-foot Earth Globe and Meteorite Exhibit.

The Earth Globe is the centerpiece. The earth is one planet of nine in the solar system, and this globe shows its physical topography, especially of the ocean floor. We've recently begun to learn about the topography of Venus and Mars, and we've found that each planet is different, but with similarities. The ridges running through the oceans (especially the Atlantic Ocean) are indicative of continental drift and are one type of boundary between crustal plates. In contrast, Venus has two "continents," but little or no continental drift; apparently its crust is too thick. Mars shows the beginnings of crustal motion with one huge canyon, but the motion didn't get very far. This globe is especially useful for looking at the distribution of mountain ranges, ocean ridges, and trenches. Unlike flat maps, in which Greenland looks as big as South America, the globe shows the true relative sizes of the earth's features.

The globe is hand-painted to show the continents with maximum summer vegetation for both hemispheres. The scale is 106 miles to the inch (70 km/cm) with a variable vertical exaggeration of about 12 times. The globe is tilted so that its axis of rotation is aligned with the true axis of the earth. (This means you see the northern hemisphere best from the north side, and the southern from the south.)

The Meteorite Exhibit can be read from either direction because each case treats a separate topic. Meteorites are important because, moon rocks aside, they are our only samples of material from beyond the earth. They are fragments of minor planets that formed and then shattered in mutual collisions millions or billions of years ago. A few contain pieces of the original material out of which the planets formed. Some (the iron meteorites) came from the interiors of small planets, while others (the stony) are the mantles and crusts of others. A very few (including one in our collection that is on display in the Mars Alcove at the far end of the exhibit hall) came from Mars! Others on display came from the surface of the asteroid Vesta. Note especially the collection of California meteorites. The origin of glassy tektites is linked to meteorite impacts on earth. Large impacts have shaped the surfaces of the moon and inner planets. Notice two large meteorites weighing several hundred pounds each on the floor. Meteorites are the oldest objects you will ever touch.

Return to the Pendulum in the Main Rotunda, and continue on to the Tesla Coil. The coil is demonstrated at regular intervals by the Guides. Ask at the Information Booth for the time of the next demonstration.

The Observatory's Tesla Coil is a transformer that increases the electrical voltage up to about half a million volts. It is the high voltage that causes the electricity to jump so far. The sparks are like short lightning bolts and the sound is like miniature thunder. The coil's high frequency (35,000 cycles, versus 60 for household current) prevents the electric current from penetrating objects, and the electricity moves along their surfaces. That is why you can take an enormous charge from this coil without damaging your skin.

The Tesla Coil was invented by the eccentric genius Nikola Tesla (b. 1856 - d. 1943), who displayed his first model in 1891. It emitted five-inch sparks. His largest coil, in 1899, was 200 feet high and sent sparks as thick as your arm flying 135 feet. It burned out the power company's main generator. That coil lit up incandescent lamps 26 miles away (where it sounded like thunder), but Tesla's idea of transmitting electricity without wires never caught on. Tesla invented much of the equipment used today in transmitting electrical power and radio signals. The Observatory's Tesla Coil was built in the 1920s, reportedly for vaudeville, and donated to the Observatory in 1937. You can purchase your own Tesla Coil from Tesla Technology Research and read about making Tesla coils at this Electronics Technology Listings page.

The Nature of Light alcove is opposite the Tesla Coil. The back wall contains samples of most of the natural elements and their ores in a recently renovated exhibit. The display at right explains the nature of light. Everything that exists (at least on the planets) is made of the same fundamental elements, and all that we know about the stars comes from analyses of their light. The left wall explains how the chemical elements were created in the Big Bang and in stars.

The next alcove houses a new exhibit on the planet Mars that features a large Mars globe, a 20-foot Pathfinder panorama, and an actual Mars rock. The Mars rock is a piece of basaltic lava that flowed and then cooled on the surface of Mars 1.3 billion years ago. It was knocked into space by a meteorite impact 180 million years ago, and fell to earth as a meteorite in 1962.

The opposite alcove contains the Galaxies exhibit. Galaxies are fundamental building blocks of the universe, and they come in a variety of shapes and sizes. The alcove will familiarize you with their importance and with the general shape of our own Milky Way.

Adjacent to the Galaxies alcove is the Radio Astronomy exhibit. Radio telescopes allow us to see what the universe would look like if our eyes were sensitive to radio waves. Until about World War II, all we knew about the universe came from what we could see with our eyes, and all the information we had arrived in the form of visible light. Since then, astronomers have devised ways of seeing the universe in infrared light, gamma rays, X-rays, and other exotic wavelengths, and the study of the universe at these wavelengths is a vital part of modern astronomy. Just as the world would look plain if you could only see things that are green, so the universe looks plain if you can see only those things that radiate visible light. Radio (and other) waves let us see things that would otherwise be invisible (like clouds of warm hydrogen), and give us new perspectives on the familiar. (Notice the unusual appearance of the sun at different wavelengths in the solar exhibit farther down the hall.)

An exhibit within the Radio Astronomy alcove explains pulsars, rapidly spinning neutron stars that send pulses of radio energy earthward. They also send much weaker pulses of visible light. Pulsars were discovered with radio telescopes.

The Cosmic Ray exhibit lies opposite the Radio Astronomy area. Cosmic rays are extremely energetic subatomic particles, often from exploded stars, that strike the earth's upper atmosphere. They smash the air molecules and send a shower of debris down towards the ground. We don't see the cosmic rays themselves, but we do detect the debris they create. The electroscope (left rear) demonstrates that particles are constantly hitting it and causing it to lose its charge. In this demonstration, additional particles are generated by a radioactive substance.

If cosmic rays can go through the Observatory roof, they can go through your body, too, and they do. We're constantly bombarded by cosmic ray debris, and they are a minor source of genetic mutation.

Sharing the Cosmic Ray Alcove are two astronomical computers that allow you to run three programs: "Hangman," "Birthdates on the Planets," and "Professor Astro." "Hangman" asks you to guess astronomical words and terms, and you hang if you don't guess them before running out of chances. "Birthdates" calculates your age on each planet and the date of your next birthday in terms of that planet's years. If you are 11 years old on earth, you are about 46 on Mercury, for example. "Professor Astro" tests your knowledge of the universe and gives interesting information about things you may not have known. It takes about a half-hour to run all three programs.

The West Rotunda is devoted mainly to the sun ­ the only star that we see from up close.

A "triple-beam coelostat," actually three solar telescopes on one mounting, sends three beams of sunlight down from the roof and into three instruments that give us three different views of the sun. A short video shows how the telescopes are mounted in the dome on the roof (this is the dome to the right as you face the Observatory from the lawn) and how they work. The telescopes operate only when the sun is shining! Nighttime visitors have to be content with the transparencies and video.

The first of three views of the sun that you will see (during the daytime only) is a bright "white-light" image on the front side of the coelostat column. It shows the sun as you would see it with your eyes alone (and the proper filters). You will often notice sunspots. Notice the earth and moon to scale below; 1 inch equals 40,000 miles.

The second solar telescope sends its beam through a slit on a table at right and into a pit 20 feet below the floor, where it falls on a diffraction grating, which acts like a prism to break the light into a continuous band of colors called the spectrum. Transparencies above explain the importance of the solar spectrum. The dark lines are produced by gases in the sun's atmosphere. Look into the eyepiece and see if you can identify any of the dark lines from the chart at upper right.

The third solar telescope uses a filter that absorbs all the light except that which comes from hydrogen, and it shows what the sun would look like if you could see only hydrogen at a certain temperature and pressure. The image is too small to see sunspots well, but you will often notice prominences--huge streamers of hydrogen that arch high above the sun's surface.

A World War II vintage periscope nearby is very popular with kids of all ages. This periscope, which was donated by the U. S. Navy, was used to sink over 40,000 tons of Japanese shipping at the end of the war. Now you can use it to sink houses and buildings in Hollywood. The periscope extends through the ceiling and projects 22 feet above the roof (you can see the top part of it from the roof).

On the other side of the rotunda you'll see a model of the 200-inch Hale Telescope on Palomar Mountain, part of the Palomar Observatory, near San Diego, and the central plug from its mirror. The model demonstrates how the 500-ton telescope and 2,000-ton dome turn to point to different parts of the sky. The mounting is designed to allow the telescope to track the stars by turning in one direction only. The large mirror to the left of the model is an unusual historic relic. It was originally the central plug of the 200-inch mirror that was removed after grinding, and it is now on loan to Griffith Observatory. It shows how thick this large telescope mirror is. The 200-inch telescope, completed in 1948, was the largest useful telescope in the world until the construction of new telescopes with thin multiple mirrors. The first of these was the twin 400-inch Keck Telescopes in Hawaii, operated jointly by the University of California and by the California Institute of Technology, and which began operation in 1991.

Telescopes

Climb to the roof by the stairs on either side of the building. (You have to go outside to get to the roof.) Most people climb to the roof for the view, but there are interesting things up there. The dome at the west end of the building houses the solar telescopes. This dome is not open to the public. Note the top part of the periscope protruding through the roof [the periscope was removed in June, 2002].

The large main dome houses the planetarium theater. The octagonal cupola opposite it covers the main rotunda and holds the pendulum.

To the east is the 12-inch Zeiss Telescope. Although the lights of Los Angeles brighten the sky and make it almost impossible to see faint objects like galaxies and nebulae, the telescope gives wonderful views of the moon and planets. The Telescope Demonstrators are exceptionally helpful at explaining what you are looking at and in answering any astronomy questions you might have. The Sky Report, (323) 663-8171, is a recorded message that gives current information on what's happening in the sky; it's updated weekly. The Galileo Project has an excellent illustrated history of the telescope.