This principle allows astronomers to see the universe as it looked after the Big Bang, which took place about 13.8 billion years ago. When astronomers study objects that are far away, they are seeing light that shows the objects as they existed at the time that light left them. And everything astronomers "see" in the distant universe is literally history. Stars and other objects beyond our solar system lie anywhere from a few light-years to a few billion light-years away. "To obtain an idea of the size of a light-year, take the circumference of the Earth (24,900 miles), lay it out in a straight line, multiply the length of the line by 7.5 (the corresponding distance is one light-second), then place 31.6 million similar lines end to end," NASA's Glenn Research Center says on its website (opens in new tab). Light from Alpha Centauri, which is the nearest star system to our own, requires roughly 4.3 years to get here, so Alpha Centauri is 4.3 light-years away. Sunlight takes about 8 minutes to reach our eyes, so the sun is about 8 light-minutes away. Light travels from the moon to our eyes in about 1 second, which means the moon is about 1 light-second away. So far no one's been able to demonstrate a real warp drive, but that hasn't slowed our collective hurtle toward new stories, new inventions and new realms of physics. Through some crafty equations, it also helps define the kilogram and the temperature unit Kelvin.īut despite the speed of light's reputation as a universal constant, scientists and science fiction writers alike spend time contemplating faster-than-light travel. National Institute of Standards and Technology (opens in new tab), it is used to define international standard measurements like the meter (and by extension, the mile, the foot and the inch). The speed of light is so immutable that, according to the U.S. That means the speed of light functions as a speed limit on the whole universe. The theory states that as matter approaches the speed of light, the matter's mass becomes infinite. It is possible for the pitch of the voice to change since gas dynamics ( i.e., Bernoulli effect) is partially responsible for the closing frequency of the vocal folds, but I haven't been able to find any data which demonstrates such a change.According to physicist Albert Einstein's theory of special relativity, on which much of modern physics is based, nothing in the universe can travel faster than light. The cavity resonances which determine the vocal formants would be raised by the higher sound speed, so the timbre of the voice would be different.
Note that if the vibration frequency of the vocal folds does not change, the actual pitch of the voice is not higher. The high speed of sound is responsible for the amusing "Donald Duck" voice which occurs when someone has breathed in helium from a balloon. This is consistent with the general relationship for sound speed in gases since the density of helium is so much less than that of air. The speed of sound in helium at 0☌ is about 972 m/s, compared to 331 m/s in air. Sound speeds in other gasesīreaking the sound barrier with an aircraft It is not dependent upon the sound amplitude, frequency or wavelength.Ĭalculation note: You may enter temperature to calculate sound speed, or enter sound speed to calculate the corresponding temperature. It is important to note that the sound speed in air is determined by the air itself. This sound speed does not apply to gases other than air, for example the helium from a balloon. At 200☌ this relationship gives 453 m/s while the more accurate formula gives 436 m/s. If you measured sound speed in your oven, you would find that this relationship doesn't fit. This calculation is usually accurate enough for dry air, but for great precision one must examine the more general relationship for sound speed in gases. The speed of sound is m/s = ft/s = mi/hr. The speed of sound in dry air is given approximately byįor temperatures reasonably close to room temperaature, where T C is the celsius temperature,
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