Shop Windows to the Universe

Dig into Montana Before History: 11K Years of Hunter-Gatherers in the Rockies and Plains by D. H. MacDonald, Ph.D. See our online store book collection.
Time zones in North America. The eastern part of the United States is offset by 5 hours from Universal Time. The central part of the USA and most of Mexico is 6 hours different from UT, while the West Coast is 8 hours different.
Click on image for full size
Public domain image from Wikipedia.

Universal Time

When it is noon where you live, it is midnight on the opposite side of the world. Usually when we think of time, we mean "the time of day where I live". If we say something happened at 9 AM, we mean it was morning a while after sunrise (in most places in most seasons). If we plan to meet someone at 6 PM, it might be for dinner in the evening more-or-less around sunset (once again, depending on the season and the latitude of our location). If someone tells you they did something around 11 PM, you generally assume it was late at night and shortly before bedtime.

However, there are occasions when something happens that isn't related to the time of day in a certain place. This is often the case for astronomical events like eclipses or the peaks of meteor showers. Astronomers use a special time scale in these cases called Universal Time (UT). People around the world can convert a time expressed as Universal Time to their own local time zone. Sometimes that time will be in the morning, or maybe late at night. Sometimes it will even be on the next day!

Universal Time is based on the time of day at the Royal Greenwich Observatory in Greenwich, England. If you learned that the peak activity of a meteor shower was going to happen at noon UT, you would know that the Sun would be high in the sky if you were in England and that you wouldn't be able to spot most meteors. If you were in the Americas, the local time would be sometime in the morning... so the meteor shower might be visible from your location if the Sun hadn't risen yet (for example, in California). In China, it would be evening... a pretty good time for viewing meteors. People in Siberia and New Zealand would be in prime position to spot meteors, since it would be midnight there.

Last modified February 3, 2010 by Randy Russell.

Shop Windows to the Universe Science Store!

Our online store includes books on science education, ranging from evolution, classroom research, and the need for science and math literacy!

Windows to the Universe Community



You might also be interested in:

Cool It! Game

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more

Meteor Showers

A meteor shower is an astronomical event during which many meteors can be seen in a short period of time. Most meteor showers have a peak activity period that lasts between several hours and a couple of...more


Meteors are streaks of light, usually lasting just a few seconds, which people occasionally see in the night sky. They are sometimes called "shooting stars" or "falling stars", though they are not stars...more

Mars Odyssey

The Mars Odyssey was launched April 7, 2001, from Cape Canaveral Air Force Station in Florida. After a six-month, 285 million-mile journey, the Odyssey arrived at Mars on October 24, 2001 (02:30 Universal...more

Solar Eclipse Webcast from Africa - March 29, 2006

On March 29, 2006 a total solar eclipse was visible from parts of Africa. Scientists from the University of Cape Coast in Ghana webcast live video coverage of this event. Windows to the Universe was a...more

Geminid Meteor Shower

The Geminid meteor shower is one of several major meteor showers that occur on roughly the same date each year. The Geminids typically "peak" (are at their greatest level of activity) in mid December....more

Quadrantid Meteor Shower

The Quadrantid meteor shower is one of several major meteor showers that occur on roughly the same date each year. The Quadrantids "peak" (are at their greatest level of activity) in early January. In...more

Tools for Math and Science

Some concepts are used in many different fields of science and serve as a general purpose "toolbox" that helps us understand and manipulate ideas across disciplines. These "tools for math and science"...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA