Fermi's Piano Tuner Problem. How Old is Old? If the Terrestrial Poles were to Melt Sunlight Exerts Pressure. Falling Eastward. What if an Asteroid Hit the Earth. Using a Jeep to Estimate the Energy in Gasoline. How do Police Radars really work? How "Fast" is the Speed of Light? How Long is a Light Year? While we have no practical ideas for how this might happen, the smart money seems to be on technologies that will allow us to circumvent the laws of spacetime, either by creating warp bubbles aka.
Until that time, we will just have to be satisfied with the Universe we can see, and to stick to exploring the part of it that is reachable using conventional methods. We have written many articles about the speed of light for Universe Today. Astronomy Cast also has an episode that addresses questions about the speed of light — Questions Show: Relativity, Relativity, and more Relativity. This was a really good article, Frasier.
Nice review of the history, and broken down in a way regular people can understand. Great job. They are born travelers… these little photons, Zipping away from their creation.
Choosing the most likely path, guided by quantum probability. Straight across the universe, pausing only for an observation, they carry past and future within. What creates your cosmic speed limit? What universal traffic cop waves you through at such a constant rate? I am now left thinking about the source of light and where it originates from, so will have to do some homework I guess.
Fascinated by all the comments here. Am I right in thinking that there may be space in the expanding universe that is without light…. What am I missing? This article is a case in point. Why not 90, miles per second, or , miles? I, too have wondered about this for a long, long time. See my little poem prior to this post. Quantum Nature of space? Interaction with dark energy? Very confusing. I plan to read a lot this winter and take some serious notes. I am NOT a mathematician, but I have a keen mind for analogy creation.
Basically, c is what it is because the electric permittivity and magnetic permeability of free space have the specific values that they do. First let me start by saying this article was a great read. Thank you for writing and posting it. Does light exert a force on an object it runs into? That is a real question, to which I have no answer.
If it does then if a large enough object that had sufficiently low mass was placed in front of a light in a vacuum it would move it right? Light absolutely does exert a force on objects.
Though they have zero invariant mass, photons do carry momentum, and can transfer it in interactions with other objects. This is a good article but thee is no smart money on circumventing the speed of light. That is the most immutable law of this universe.
Or perhaps you could suggest that dark energy and dark matter are those moving through our universe at supra-C? Good article. It turns out that its due to the time dilation effect that Einstein described with the famous Lorentz Transformation. One uncovered his lantern; when the other person saw the flash, he uncovered his too.
But Galileo's experimental distance wasn't far enough for his participants to record the speed of light. He could only conclude that light traveled at least 10 times faster than sound. To create an astronomical clock, he recorded the precise timing of the eclipses of Jupiter's moon , Io, from Earth. He noticed that the eclipses appeared to lag the most when Jupiter and Earth were moving away from one another, showed up ahead of time when the planets were approaching and occurred on schedule when the planets were at their closest or farthest points — a rough version of the Doppler effect or redshift.
In a leap of intuition, he determined that light was taking measurable time to travel from Io to Earth. Since the size of the solar system and Earth's orbit wasn't yet accurately known, argued a paper in the American Journal of Physics , he was a bit off. But at last, scientists had a number to work with.
In , English physicist James Bradley based a new set of calculations on the change in the apparent position of the stars due Earth's travels around the sun. Two new attempts in the mids brought the problem back to Earth. French physicist Hippolyte Fizeau set a beam of light on a rapidly rotating toothed wheel, with a mirror set up 5 miles 8 km away to reflect it back to its source.
Varying the speed of the wheel allowed Fizeau to calculate how long it took for the light to travel out of the hole, to the adjacent mirror, and back through the gap. Another French physicist, Leon Foucault, used a rotating mirror rather than a wheel to perform essentially the same experiment. Another scientist who tackled the speed of light mystery was Poland-born Albert A. Michelson, who grew up in California during the state's gold rush period, and honed his interest in physics while attending the U.
Naval Academy, according to the University of Virginia. In , he attempted to replicate Foucault's method of determining the speed of light, but Michelson increased the distance between mirrors and used extremely high-quality mirrors and lenses.
In his second round of experiments, Michelson flashed lights between two mountain tops with carefully measured distances to get a more precise estimate. And in his third attempt just before his death in , according to the Smithsonian's Air and Space magazine, he built a mile-long depressurized tube of corrugated steel pipe.
The pipe simulated a near-vacuum that would remove any effect of air on light speed for an even finer measurement, just slightly lower than the accepted value of the speed of light today. Michelson also studied the nature of light itself, wrote astrophysicist Ethan Siegal in the Forbes science blog, Starts With a Bang.
The best minds in physics at the time of Michelson's experiments were divided: Was light a wave or a particle? Michelson, along with his colleague Edward Morley, worked under the assumption that light moved as a wave, just like sound. And just as sound needs particles to move, Michelson and Morley and other physicists of the time reasoned, light must have some kind of medium to move through. This invisible, undetectable stuff was called the "luminiferous aether" also known as "ether".
Though Michelson and Morley built a sophisticated interferometer a very basic version of the instrument used today in LIGO facilities , Michelson could not find evidence of any kind of luminiferous aether whatsoever.
Light, he determined, can and does travel through a vacuum. The equation describes the relationship between mass and energy — small amounts of mass m contain, or are made up of, an inherently enormous amount of energy E. That's what makes nuclear bombs so powerful: They're converting mass into blasts of energy. Because energy is equal to mass times the speed of light squared, the speed of light serves as a conversion factor, explaining exactly how much energy must be within matter.
And because the speed of light is such a huge number, even small amounts of mass must equate to vast quantities of energy. In order to accurately describe the universe, Einstein's elegant equation requires the speed of light to be an immutable constant. Einstein asserted that light moved through a vacuum, not any kind of luminiferous aether, and in such a way that it moved at the same speed no matter the speed of the observer.
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