Speed of Light: Foundation of Universe (03:01)
The speed of light is the cornerstone upon which the universe is built. Light speed makes everyday experiences almost instantaneous.
Radio Signals: Lag Time (02:39)
Light from the moon takes 1.3 seconds to reach Earth; light from the sun takes 8 minutes. Signals to and from the Mars probe and Voyager 1 take 44 minutes and 29 hours respectively.
Light Speed/Time Machine (01:28)
The sun's nearest star is Proxima Centauri, 25 trillion miles away. A light year is approximately 6 trillion miles. Using light years to discuss numbers opens up another dimension of light speed's character. Earth sees the star Vega as it was 25 light years ago.
Light Speed's Story of the Universe (04:31)
Light has the ability to take us into the past. Through a telescope, we see the Andromeda Galaxy as it was 2.5 million years ago. Light from 13 billion years ago when the universe was born is just reaching Earth now.
Light as a Measure of Distance (04:58)
Light speed is an iron-clad constant, a measuring stick of the entire universe. Very distant galaxies are moving away with a velocity that is proportional to distance. The "redshift" of the light from these galaxies is therefore a measure of their distance.
Cosmic Microwave Background (03:32)
Cosmic Microwave Background (CMB) radiation is the name for the remnant energy left over from the formation of the universe, according to the Big Bang theory. It is uniform in color and temperature.
Space Expansion: Faster Than Light Speed (01:42)
Some galaxies will never be seen because the light from those galaxies will never reach Earth--space is speeding faster than the speed of light.
Near the Speed of Light (03:03)
The entire universe bends to accommodate the speed of light. Every beam of light in the universe travels at the same rate through space no matter the speed of the light source. Light speed is at the heart of Einstein's Special Theory of Relativity.
Nature of Space and Time (08:23)
The speed of light is a constant only in the vacuum of space. On Earth, when light moves through things like glass or liquids, it slows down. If this were not a property of light, humans would be unable to differentiate objects that they see.
Zero Light Speed (03:46)
A groundbreaking laboratory experiment shoots pulses of light through sodium atom clouds cooled to a few billionths of a degree above absolute zero. The process slows down the speed of light to a few miles per hour.
Star Travel and Warp Speed (05:23)
In April 2008, Stephen Hawking called on the human race to colonize space and make interstellar travel a long-term aim. This goal is dependent upon the ability to travel faster than light speed. Is this possible?
Credits: Light Speed (00:22)
Credits: Light Speed
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