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Slow Light

In Astronomy by Brian Koberlein10 Comments

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We think of light as being extraordinarily fast. It’s so fast that a beam of light could travel from New York to Los Angeles in about a hundredth of a second. If anything can be called fast, then that ultimate speed limit must surely qualify. And yet, on an astronomical scale, light is tediously slow. Our solar system is a mere speck in the vast scale of the cosmos, and yet light takes time to journey even that speck.

You can get a feel for slowness of light in the video, where the journey of light is shown in real time. From the instant it leaves the Sun’s surface, to just past Jupiter takes nearly three-quarters of an hour. A video showing the journey all the way to Pluto would take more than 5 hours. It would take about 18 hours to reach Voyager 1. All that time to take the smallest step into the universe.

As you watch this video (or part of it) keep in mind that this isn’t a representation of “rocket speed,” or any speed we can remotely achieve. It is the limit of all possible speeds. It is the expanding sphere of influence for anything we do. We are bound by that speed, as is everything else in the universe.


  1. Relativistically, the light beam is “timeless”, but I can still appreciate the video.

  2. “We are bound by that speed, as is everything else in the universe” slightly inaccurate? – are we not all governed by the ‘speed’ of gravity which is much quicker.

      1. Actually like light, gravity is subjective and is bound by space time. Gravity isn’t the pull of an object, but the force of space trying to retake the space that as been displaced by matter. The more mater the more space is displaced and the more time is skewed by this effect. Time at sea level and 300,000 miles away moves at different speeds because of the compression of space closer to matter. So light actually travels at different speed on the surface of earth than it does 300,000 miles above it.

  3. Was it actually considering the relativity (which he states that he does not in the vimeo description) would the observer even “see” the Sun?

    As far as my limited knowledge of relativity goes, everything should be “infinitely” red-shifted in the observer’s view as he looks directly “behind” (as it moves forward). So in essence the observer should see a black-ish disk around were the sun is (may be spanned a few degrees) and then gradually (as looking around from “dead behind” to the “side”) “red” objects appear followed by some natural color objects on the sides. if the observer continues to rotate his gaze, objects should become more “violet” and then fade into ultra violet and then x-rays and so on. The “front view” of the observer should be very very very bright (like gamma ray bright!)

    Is that a fair assessment? or am I getting all my relativity wrong! 😀

  4. The viewpoint that brought this home to me was as follows:

    Think of a scale model of the universe scaled down by a factor of 10^8 and it’s less than 4 metres, just a couple of big steps out to the moon. It’s 45 km out to Neptune. The nearest star is still about as far away as the moon is. The speed of light is now 3 metres a second – a good running pace for a human. That’s as fast as anything can get around, and it’s still more than 300 000 km between stars /other potential solar systems in spite of knocking 8 zeroes off all the distances.

  5. You just realize what infinity of space really means. Travel at this speed and everything still remain still around you. This video makes me second guess if light is really the ultimate “speed limit”. Seems the Universe just will not work with this barrier

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