Speed of Light

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    Nothing can travel faster than the speed of light - 1 billion kilometer per hour - not even quasars. To know more about quasars see the animation below ...

    Digitally altered in Photoshop from this photo kindly provided by Patrick Boury pbo31.

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    1. :+: efly 飛鷹人e-fly :+: ages ago | reply

      你好,我是群組 一目了然的標誌標誌 World Signs 的管理員,我們希望將你的相片增加到此群組。

      Cool. Where can we see that kind of sign?

    2. Jen_K ages ago | reply

      Now, this is funny! Good job!

    3. Sir Francis Canker Photography © ages ago | reply

      I think the standard is 300,000 km/s.

      Miles, as kwsanders suggests, are only used in the US. They will sometime not be used anymore and mean nothing in the international context.

      Billion is misleading cause in some cultures it refers to 1 thousand times 1000, while in others it means 1 million times one thousand.

      This is why I prefer my measure above!


    4. jpctalbot ages ago | reply

      Sir Francis: I agree with you about miles, however your measure also has problems. In France and Belgium the comma is equivalent to the decimal point.

      300,000 km/s is equal to 300 km/s !!

      Perhaps the best sign would have been the symbol 'c' which is unit independent but most people would not get the joke.

    5. InvisibleSocks ages ago | reply

      I blogged this hope you dont mind

    6. zupermx ages ago | reply

      LOL Cool

    7. zupermx ages ago | reply

      Hi, I'm an admin for a group called Signs & Logos, and we'd love to have this added to the group!

    8. Kafka_K ages ago | reply

      Love the depth of field . the traffic blur really emphasises this pic. Great stuff. :-)

    9. Serious Dr ages ago | reply

      lol!!very nice title and photo!!

    10. ray.llionaire 116 months ago | reply

      Thank you for sharing your awesome photo! I'm using this in my blog post here: blog.5m10y.com/2008/11/27/how-to-make-money-off-your-plun...

      I put a link back to this page, with your flickr username as the text. Please let me know if you're OK with this or you'd like to be credited in some other way.

      Thanks again!

    11. jpctalbot 116 months ago | reply

      ray.llionaire: Thanks for the link, I appreciate it!

    12. eeanm 114 months ago | reply

      This sign isn't accurate really. The speedometer you have in your car is the speed that the land goes past the car from the cars perspective. It just so happens that someone standing on land sees the cars go past at the same speed the car sees the land go past, since nothing relativistic is happening yet (or not enough to matter).

      But if the speed of light was 50 km/h, your average car can still easily achieve faster-then-light. For a pedestrian the car will be going about 49 km/h no matter how fast its going from the drivers perspective, due to time dilation.

      Neither prospectives opinion is superior then the other. But speed-limit signs aren't directed at pedestrians! Its not a "you aren't allowed to see any vehicle going faster then this speed" sign, speed limit signs are of course directed at the driver.

      I think these "speed limit" signs are humorous, but they also spread misconceptions about the relativity in a misapplied metaphor.

    13. jpctalbot 114 months ago | reply

      eeanm: Your are incorrect that the speed of the vehicle relative to the ground can be arbitrarily larger than the speed of light.

      You are correct in that pedestrians can never observe the vehicle traveling faster than light. However the converse is also true : a passenger never 'sees' the road go past them faster than the speed of light.

      The solution is subtle but firmly rooted in the symmetry of the Lorentz transformation. The basic premise was discovered by Einstein about a century ago in his special theory of relativity. In a nutshell, here are its basic postulates:

      1. The laws of physics are the same for any observer regardless of relative constant velocity.

      2. Nothing can travel faster than light from the point of view of a given frame.

      3. There is no preferred frame, all frames are equivalent, there is no concept of an absolute 'rest' frame.

      When you measure time in the passenger's frame of reference, you must also measure space relative to this frame as well. This is a subtle point missed by many beginners to relativity theory. Passengers must measure velocity by carrying with them both a clock and a meter-stick. This is the very definition of the laws of physics, you are measuring everything from the car's rest frame; this includes both time and space. The Lorentz transformation affects both time and space : Time dilation occurs however many amateurs forget about relativistic space contraction.

      A more concrete example :

      For a vehicle traveling 0.99999999 times the speed of light and from the point of view of a passenger our Milky-Way galaxy appears to have contracted down to the thickness of a pancake. From the point of view of a passenger, their speed never exceeds light speed because relativistic space contraction compensates time dilation. Also because the passenger was a nerdy physicist who always carries with him a good set of temporal and spatial calibrators such as a portable atomic clock and a good wooden ruler, and he knows how to use them wisely to measure velocity, LOL!

      The moral of the story is : You cannot measure velocity using units from two different reference frames. Thanks to Einstein, who set us all on the right path a century ago, both time and space must be measured relative to the observer, i.e. within the passenger reference frame.

      You had only half the equation, time dilation. You failed to take into account space contraction. In your case the old proverb still holds wisdom:

      'A little knowledge is a dangerous thing, drinking deeply from the well of truth sobers us up again' - Ancient Greek Proverb

      There is a natural speed limit : 1,079,252,849 kilometer per hour. The sign is obviously redundant, and the humor should be obvious to those more familiar with relativity theory. My sign is completely valid and I encourage you to continue to question the Universe around you, however I also hope that this brief tutorial helped you gain a new insight and appreciation of the marvelous nature of our Universe as described by relativity theory.

      As an exercise for your studies (and to confuse you further), the vehicle mentioned in the above example will cross the galaxy in just milliseconds from the passengers point of view. In the pedestrian frame of reference the vehicle is travelling very near the speed of light and appears thinner than a sheet of paper, however, if the pedestrain and future generations of humans continue to observe, it will leave the galaxy in several hundred thousand years. Paradox? Not really, just basic special relativity.

    14. Phot∞m 110 months ago | reply

      You're invited!!!! Please add this to the group "filés et mouvements"
      filé invit
      We'd love to have this picture into the group:
      ~Please add this photo to the pool ~

    15. liewcf 99 months ago | reply

      thanks for sharing the photo. I used it in my blog post Google Drop Search Ranking of Slow Sites.

    16. Astronomy Humor 91 months ago | reply

      Added to my Astronomy Humor gallery.

    17. mlhradio 84 months ago | reply

      Congratulations on receiving more than 10,000 views -- that's quite impressive! Now that you've reached this milestone, you might want to consider graduating this photograph from the 'Views: 5000' group to the 'Views: 10000' group, which can be found here: www.flickr.com/groups/views10000/

      Once again, congratulations and hopefully your photos will receive many more views in the future! Reminder: Photos should only be in one 'Views:xx' group at a time. (This is an automatic message posted to all items in the 'Views: 5000' group that receive more than 10,000 views. There is no need to reply to this message.)

    18. zegloff 79 months ago | reply

      Howdy John!

      Thanks for posting your photographs on flikr Creative Commons. I loved this picture of the speed of light, and I used it in a blog post entitled, 7 Reasons Why Being a Goofball is the Fastest Route to Enlightenment.

      The link to the post with your photo is here: lifeinzd.com/7-reasons-why-being-a-goofball-is-the-fastes...

      Thanks again. I really appreciate you sharing your work!

      Cheers, Z Egloff

    19. Richard Manley-Tannis 48 months ago | reply

      Thanks for sharing the image! I just used it in a blog in respect to the word 'paradox:' mayawalk.ca/blog-a-deacons-musing-flow/

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