• Question: I suspect our measured speed of light is wrong, being that we are moving throughout the universe. While we cannot measure how fast we are moving in relation to a 'stationary universe', we have measured roughly our speed in the solar system, in the galaxy and (I think) in our local cluster and supercluster. Wouldn't these speeds added together result in a speed much larger than our measured speed of light? Does that mean that earth is actually travelling somewhat 10 times or more the speed of light? Would that mean c is actually c+earth speed+galaxy rotation speed+etc etc? c is correct for earth, but not necessarily for Mars, Venus, Jupiter etc? Is c then relative to the planet your on?

    Asked by danm36 to Hywel, Joseph, Patience, Poonam, Rachael on 18 Jun 2010 in Categories: .
    • Photo: Joseph Cook

      Joseph Cook answered on 18 Jun 2010:

      Unfortunately not. The speed of light is constant to all observers, no matter where they are an no matter how fast they are travelling – even if they are travelling very fast. This may seem difficult to accept, particularly because speeds in every day life seem very different depending on where you observe them from or how fast you are travelling, but that’s the way it is. Light is a fascinating thing and has some amazing properties – this is probably the coolest, if you ask me.

      If you’re interested in this topic, I recommend you read about Einstein’s theory of special relativity – I must warn you, it’s very difficult though. You can learn all about this kind of cool stuff in a physics degree.

    • Photo: Dr Hywel Jones

      Dr Hywel Jones answered on 18 Jun 2010:

      I’m afraid a discussion of the ideas behind special relativity and general relativity (as proposed by Einstein) would be needed her to explain properly.
      Just to say that even if you added all those speeds up you don’t get anywhere near the speed of light. Its 299 792 458 metres per second or 186,000 miles per second. And to talk about speed you need to measure it relative to someting, what is your reference point?

      Nothing can really exceed the speed of light and the weird thing is if you are travelling close to the speed of light and you shine a torch and measure the speed, it will appear toyou to have the same speed as if you were standing still. Its all relative (hence the name of the theories).

    • Photo: Poonam Kaushik

      Poonam Kaushik answered on 18 Jun 2010:

      First of all thanx for asking me this mind boggling question. Enough of experimentation has been done to find out the speed of light. u know light is kind of electromagnetic radiation and all kinda electromagnetic radiations have same speed even in the vacuum. Today our each and everything in study of astronomy, electricity generation, nuclear power generators, and physics can’ t be untrue.coz all calculations we do for even sending a tiny rover to Mars or moon is dependent on this calculation only. If it would have been untrue thn I dont think going to moon or mars is kinda possible……….

      Regarding your saying that we have roughly measured our speed in solar system seems quite true . becoz to measure speed v require distance covered in reference to time. So light speed will remain same irrespective to any point in universe. It will on any part of universe will travel at same speed means it wil cover same distance with time. So there is no point in adding up all the things u mentioned dear!

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