# The Naked Scientists Forum

### Author Topic: Can an object move faster than the speed of light?  (Read 3057 times)

#### Jim Roche

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##### Can an object move faster than the speed of light?
« on: 19/07/2008 10:36:28 »
Jim Roche  asked the Naked Scientists:

Hi Doctor Chris,

It's a lonely job being a bored teenage spaceman on watch some 183,000 miles above Earth's surface. There's simply nothing to do man!

To keep me attentive I have to keep hold of a super fine, and super strong thread, on the end of which is a 10 pound lump of stone which I have to keep just above ground level. Then it occurred to me; if I let go of the thread the stone would instantly fall to Earth, and as I am further above the Earth's surface that light travels in a second, am I not "doing something that is faster than the speed of light?"

Answers please if you can be bothered, because I'm off to see if I can get them to put a Yo-Yo on the  end of this thing, or something a bit more interesting than a brick

Yours faithfully

Space Man Lethy Thargix Indo-lent
AKA Jim Roche - Leeds

What do you think?

#### DoctorBeaver

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##### Can an object move faster than the speed of light?
« Reply #1 on: 19/07/2008 10:47:19 »

I suppose, if you're that bored up there, I could explain the reason so that you've got something to read.

It's to do with transfer of information. In this instance the information is that you have let go of the string. That information needs to travel along the length of the string, passing from molecule to molecule. I'm not sure of the speed at which such information would travel along the string, but it certainly wouldn't exceed the speed of light, and would probably fall well short of it.

#### lyner

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##### Can an object move faster than the speed of light?
« Reply #2 on: 19/07/2008 14:18:45 »
After you let go of the thread it would be ages for the bottom end to go slack. Letting go would set up a pulse / wave which would travel down the thread at, not the speed of light, but the speed of sound in the thread.

#### DoctorBeaver

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##### Can an object move faster than the speed of light?
« Reply #3 on: 19/07/2008 15:16:52 »
Sophie - I wondered whether it would be the speed of sound. Thank you for clarifying that point.

#### neilep

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##### Can an object move faster than the speed of light?
« Reply #4 on: 19/07/2008 18:25:06 »
As a firm believer in empirical study I conducted this experiment with my 2 year old son whilst he held a torch.

The premise was to get James to turn the torch on at the same time I dropped the payload towards the Earth.

Here I am happily orbiting the Earth at 186,001 miles !

Notice that it's quite a nice day out !

...and now the empirical bit........

At this instant I instructed James to turn the torch on....and I also let go of the payload...VOILA.....my payload did in fact reach the Earth before the light from my torch (hmmm..must remember to put batteries in next time and also explain to James what a torch is)

#### DoctorBeaver

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##### Can an object move faster than the speed of light?
« Reply #5 on: 19/07/2008 19:50:04 »
I note that dropping the payload caused your spaceship to rotate. That could be a bit dangerous, don't you think?

It also appears that you have obliterated most of arctic Norway. Those poor reindeer!  [:-'(]

#### neilep

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##### Can an object move faster than the speed of light?
« Reply #6 on: 19/07/2008 20:28:04 »
Hmmm...ah !!...well...The Earth span...not my spaceship !

......and as far as Norway is concerned....I'm sure Slartibartfast can just make another one !

#### DoctorBeaver

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##### Can an object move faster than the speed of light?
« Reply #7 on: 19/07/2008 20:37:54 »
Hmmm...ah !!...well...The Earth span...not my spaceship !

So explain the angle of your hand in the 2nd photo.

......and as far as Norway is concerned....I'm sure Slartibartfast can just make another one !

#### neilep

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##### Can an object move faster than the speed of light?
« Reply #8 on: 19/07/2008 20:50:24 »
Hmmm...ah !!...well...The Earth span...not my spaceship !

Quote
So explain the angle of your hand in the 2nd photo.

That's gravity lensing for ya !!

......and as far as Norway is concerned....I'm sure Slartibartfast can just make another one !

#### DoctorBeaver

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##### Can an object move faster than the speed of light?
« Reply #9 on: 19/07/2008 21:32:16 »
Hmmm...ah !!...well...The Earth span...not my spaceship !

Quote
So explain the angle of your hand in the 2nd photo.

That's gravity lensing for ya !!

#### The Naked Scientists Forum

##### Can an object move faster than the speed of light?
« Reply #9 on: 19/07/2008 21:32:16 »