Broom Handle Warp Speed.

[Les Ewan]

Tried to grapple with the subjects discussed in this sections but to be honest its way over my head,I cant even understand the questions let alone the  answers.  So here's a light hearted theory from a simpleton.

Its odd some of the things that enter your head late at night when you cant sleep. I was wondering if were possible that you could hold on to a broom handle say a million miles long and were able to flick it quickly across the sky the other end of the handle would travel more than the speed of light?

OK Ill get my coat!

Les

[johninderby]

Your question reminds me of Archimedes and his give me a lever long enough and a fulcrum on which to place it and I'll move the earth.  

            John

[Mognet]

A quick back of an envelope calculation says yes, if you can spin that million mile long broom handle round your head in a period of less than 33.73 seconds. Basically it's length of broom handle times 2, times pi, and divided by the speed of light

I'm now wondering just how heavy that million mile long broom handle will be  Hope you have strong arm muscles!

[Dave In Vermont]

15 minutes ago, Mognet said:

A quick.....

I'm now wondering just how heavy that million mile long broom handle will be  Hope you have strong arm muscles!

If you were in space - which you should be with your broomstick - it wouldn't weigh anything (sparing me the lecture on gravitational-fields from stars and galaxies and....).

Can I have my Phd. now?

Dave

[SilverAstro]

2 hours ago, Les Ewan said:

 and were able to flick it quickly across the sky the other end of the handle would travel more than the speed of light?

OK Ill get my coat!

sadly (or fortunately for AlbertE and his theory)  no ! you would not be able to 'flick' it fast enough, the far end would approach the speed of light and thus become too massive, your broom handle would bend then break or your arm would

What you could do is pin two broom handles together with the pin (pivot) close to you, like a giant pair of scissors, then you can flick them closed (or open at your hands) such that the point of intersection of the two distant 'blades' will travel away from you (or towards you) faster than the speed of light.

For the answer to how that is possible :

You will have to ask Uncle Dave and his new PhD to explain about group and phase velocities

 

 

[billyharris72]

As above, no. Also, if you were to take a broom handle 1ly long, hold one end of the broom handle and push / jerk it forward one inch as fast as you could, the other end would not move at all for at least one year. Information can't travel faster than light, simple as that.

[Dave In Vermont]

4 hours ago, SilverAstro said:

sadly (or fortunately for AlbertE and his theory)  no ! you would not be able to 'flick' it fast enough, the far end would approach the speed of light and thus become too massive, your broom handle would bend then break or your arm would

What you could do is pin two broom handles together with the pin (pivot) close to you, like a giant pair of scissors, then you can flick them closed (or open at your hands) such that the point of intersection of the two distant 'blades' will travel away from you (or towards you) faster than the speed of light.

For the answer to how that is possible :

You will have to ask Uncle Dave and his new PhD to explain about group and phase velocities

 

 

Oh NO!! Another liner for my Parrot-Cage.....

   

Yikes -

Dave

[Paul73]

It's Monday morning. My coffee is still a small pile of beans at the other end of the school run. And, you guys do this to my head??

It did make me smile though.????

Paul

PS. Congrats to the Dave on his shiny new SGL PhD.

[saac]

I've seen this type of question asked but where the broom handle is replaced with a more manageable laser beam or shadow. The question being would it be possible to have the laser beam (at a suitable length along its path) trace out an arc with a tangential velocity greater than the speed of light.  A similar version concerns casting a shadow across the face of the moon using a powerful (hypothetical) searchlight projected from Earth. The shadow is cast on the moon by moving  a hand across the searchlight beam - move the hand quickly enough and the resulting shadow moves across the surface of the moon with the leading edge moving faster than c. On first inspection, the speed of the shadow's front appears to challenge what we know about the ultimate speed limit c but that is only because when we talk about the speed limit we generally only paraphrase what it actually means.  In the case of the moving shadow, or laser beam, no "information" is said to be moving faster that the speed of light so the universe is still safe. These questions are great because they really do tease out understanding of c. Having said all that I hope I've remembered the details of the examples correctly.  

Jim 

[andrew s]

To Jim's point such a broom would not be rigid and would not move as envisaged. It would flex and no potion of it could move relative to any other part at the speed of light. As an aside you would need to consider the conservation of angular momentum! 

Regards Andrew

[Alien 13]

What would happen if instead of a broom you had a weight on a string (carbon nano tubes) and spun it in space slowly letting the string out until the weight was getting close to light speed and you suddenly let go of the string, would the weight fly off instantly or still be rotating around you? A similar question would involve the earth and the sun if the sun suddenly vanished, we would still see the light for 8 mins but would the effect of the bend in space time of the suns mass be instant?

Alan  

[Mognet]

20 hours ago, Dave In Vermont said:

If you were in space - which you should be with your broomstick - it wouldn't weigh anything (sparing me the lecture on gravitational-fields from stars and galaxies and....).

Can I have my Phd. now?

Dave

The weight/mass thing explains why I'm not a physicist!

[johninderby]

The universe is a very, very, very complicated thing. 

           John

[saac]

21 minutes ago, johninderby said:

The universe is a very, very, very complicated thing. 

           John

I bet it is so only when we observe it, the rest of the time I bet it's really simple  

Jim

[andrew s]

2 hours ago, Alien 13 said:

What would happen if instead of a broom you had a weight on a string (carbon nano tubes) and spun it in space slowly letting the string out until the weight was getting close to light speed and you suddenly let go of the string, would the weight fly off instantly or still be rotating around you? A similar question would involve the earth and the sun if the sun suddenly vanished, we would still see the light for 8 mins but would the effect of the bend in space time of the suns mass be instant?

Alan  

Nothing can be instantaneous as information can only travel at a maximum of the speed of light.

Regards Andrew

[saac]

Alan I think we also have a problem with our carbon nano tube string! In the style of XKCD - Rotating with an angular velocity of 0.2 rad/s  (approx 2rpm) to give a tangential speed of c at 100 million miles would require a centripetal force of around 2.6 x10^13 N. This ignores the mass at the end and has the mass of the string distributed at 1g per km (i've been conservative I think). I've also assumed the mass of the string itself to be distributed at the centre - now bear in mind it is late and my brain has been awake too long today, but 2.6 x10^13 N is a lot of apples for even a carbon nano tube to hold. I suspect that the electromagnetic force holding the carbon atoms in sublime formation in the string would have long given up the battle (requires peer review)  

Of course I accept no responsibility for my calculations, anyone twirling a 100 million mile carbon nano tube string above their head with a mass at the end should know better  

Jim

[billyharris72]

Also, surely even if the weight was travelling close to the speed of light (i.e. if we assume that is not a problem) it still would not fly off instananeously. I would think the string would keep exerting a centripetal force (and so the weight would keep moving in a circle) until the compression wave introduced into the string by your letting go of it reached the other end. In this sense it seems similar to the broomstick "poking" rather than swinging situation. When you jab me with a broom handle the motion travels as a compression wave (i.e. at the speed of sound in that material), not instantly, and this seems like the inverse of that situation.

Billy.