# speed of light question

**URL:** <https://boards.straightdope.com/t/speed-of-light-question/55959>\
**Category:** Factual Questions\
**Created:** [February 26, 2001, 7:48pm UTC](https://boards.straightdope.com/t/speed-of-light-question/55959 "2001-02-26T19:48:12Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![justinh](https://avatars.discourse-cdn.com/v4/letter/j/9fc29f/32.png) [@justinh](https://boards.straightdope.com/u/justinh)\
**Post date:** [February 26, 2001, 7:48pm UTC](https://boards.straightdope.com/t/speed-of-light-question/55959/1 "2001-02-26T19:48:12Z")

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so I am flying along at the speed of light. Can anything pass me up? After I pass a star will I still see the light from the star as it overtakes me? My dumb brother thought he heard this and it was explained as something to do with relativity.

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**Author:** ![davidpratt](https://avatars.discourse-cdn.com/v4/letter/d/b38774/32.png) [@davidpratt](https://boards.straightdope.com/u/davidpratt)\
**Post date:** [February 26, 2001, 8:36pm UTC](https://boards.straightdope.com/t/speed-of-light-question/55959/2 "2001-02-26T20:36:48Z")

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Yes it is all to do with the theory of relativity. Because of the equivalence of energy and mass, the energy an object has due to its motion will add to its mass. Thus as an object approaches the speed of light, its mass increases rapidly, and so ever more energy is needed to accelerate it further. In fact, an object that has mass can never reach the speed of light because by then its mass would be infinite, so that all the energy in the universe would be insufficient to accelerate the object the last infitesimal amount to reach the speed of light. Only light, or other waves that have no intribsic mass can move at the speed of light.  
I suggest that you try reading “A Brief History of Time” by Stephen Hawking, which gives a (nearly) non-mathematical feel for the subject.  
Thus, your first question cannot be answered as you cannot travel at the speed of light

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**Author:** ![Patty\_O\_Furniture](https://avatars.discourse-cdn.com/v4/letter/p/96bed5/32.png) [@Patty\_O\_Furniture](https://boards.straightdope.com/u/Patty_O_Furniture)\
**Post date:** [February 26, 2001, 8:43pm UTC](https://boards.straightdope.com/t/speed-of-light-question/55959/3 "2001-02-26T20:43:37Z")

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_Originally posted by justinh_:

> [@](#):
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> **so I am flying along at the speed of light.**

No you most certainly are _not_, young man.

> [@](#):
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> **Can anything pass me up?**

No.

> [@](#):
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> **After I pass a star will I still see the light from the star as it overtakes me?**

You will still be able to see the star, squeezed into a small area in your _forward_ field of view long after you’ve passed it. This according to Carl Sagan.

> [@](#):
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> **My dumb brother thought he heard this and it was explained as something to do with relativity.**

There is a dumb brother/relativity joke in there somewhere, but I’ll let somebody else make it.

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**Author:** ![justinh](https://avatars.discourse-cdn.com/v4/letter/j/9fc29f/32.png) [@justinh](https://boards.straightdope.com/u/justinh)\
**Post date:** [February 26, 2001, 9:32pm UTC](https://boards.straightdope.com/t/speed-of-light-question/55959/4 "2001-02-26T21:32:29Z")

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well I knew one of us was an idiot. But if an idiot is talking to a genius then how can the idiot tell who is the genius?