UCSB Science Line
Sponge Spicules Nerve Cells Galaxy Abalone Shell Nickel Succinate X-ray Lens Lupine
UCSB Science Line
Home
How it Works
Ask a Question
Search Topics
Webcasts
Our Scientists
Science Links
Contact Information
Can you tell time without a clock or watch?
Answer 1:

Great question! Before we had watches or clocks (or laptops or cell phones) to read off the time, people used other techniques to approximate the time. These techniques use the sun, the moon, and/or the position of stars to determine about how far into the day and how far into the night it is. These techniques still come in handy if you are outside without a watch.

For example, during the day, you can observe the track of the sun across the sky. When the sun is the highest in the sky and at the center of its track, it is about 12 noon. The actual time depends also on where you are in your time zone and whether or not it's daylight savings time. In the morning, the sun will be in the East and in the evening, the sun will be in the West. You can figure out about what time it is by how far above the horizon the sun is. For example, if you know the sun rises at about 6 am and sets at about 6 pm (typical in early spring and late summer), and the sun is in the East halfway between the horizon and overhead, then it is about 9 am.

Of course, these techniques can't tell you down to the minute or second what time it is, and for that, you do need to refer to a time-keeping device like a watch.

Since about 1950, we have used a very precise clock called the "atomic clock" as a reference for all other clocks. This clock is kept at one of the US National Laboratories. The atomic clock tells time to tiny fractions of a second and other clocks (such as cell phone clocks) are set to match this reference clock.


Answer 2:

You sure can tell time without a clock or a watch! Time passes regardless of whether you're keeping track of it or not. While you won't be able to tell time in seconds or minutes without a watch, you can still guess the hour or general time of day. One of the oldest ways of telling time is the sundial, and it still works. Sundials work by casting a shadow on a disk marked with different periods of time. As the sun moves in the sky, the shadow falls on a different part of the disk, which gives the time of day. Sundials don't work well at night, though, as you can imagine.



Click Here to return to the search form.

University of California, Santa Barbara Materials Research Laboratory National Science Foundation
This program is co-sponsored by the National Science Foundation and UCSB School-University Partnerships
Copyright © 2015 The Regents of the University of California,
All Rights Reserved.
UCSB Terms of Use