Can a mallot on Earth wake up a cat on a planet 300,000 km away?

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Discussion Overview

The discussion revolves around a thought experiment concerning the transmission of movement through a hypothetical long mallet connecting Earth and a distant planet, referred to as planet Cat, located 300,000 km away. Participants explore concepts of rigidity, causality, and the limitations imposed by the speed of light and sound in materials.

Discussion Character

  • Exploratory, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant questions the feasibility of using a mallet to wake a cat on a distant planet, suggesting that the concept of light cones and causality implies limitations on instantaneous movement transfer.
  • Another participant asserts that no material can be perfectly rigid, emphasizing that movement can only be transmitted at the speed of sound within the material, using diamond as an example of a fast but still limited speed.
  • A participant humorously notes the improbability of the existence of planet Cat, while also engaging with the idea that the deformation of the mallet would contribute to the delay in signal transmission.
  • Further discussion confirms that any physical connection would inherently be slower than the speed of light, thereby questioning the effectiveness of such a thought experiment in achieving instantaneous communication.

Areas of Agreement / Disagreement

Participants generally agree on the limitations of material rigidity and the implications of speed of sound versus speed of light. However, there is a light-hearted disagreement regarding the existence of planet Cat, which remains unresolved.

Contextual Notes

The discussion highlights assumptions about the nature of materials and the principles of physics, particularly regarding rigidity and signal transmission, without resolving the implications of these assumptions on the thought experiment.

Michele
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Hello to everyone. I used to be very passionate about physics when I was a high school student, but I have taken a different path andless than 10 years later here I am, struggling to remember the basics...all this to say that you will probably able to point out the flaw in my reasoning. Here it is:

I was recently reading the first chapters of "The Large, the Small and the Human Mind" by Roger Penrose and I was facing the apparently simple concept of light cones and the concept of casuality. To my understanding, if I am on planet Earth and my cat is napping on planet Cat, which happens to be about 300 000 km away from Earth (not the best distance to keep in touch with your cat I guess), if I want to wake up my cat I will only be able to do so 1 second in my future (in the best case).
Now what if on planet Cat there were a gong, placed close to my cat's hears, and right next to it a mallot with a 300 000 km long handle, so that I could grab the mallot from planet Earth and strike the gong on planet Cat. Assuming the mallot is made of some non deformable material, wouldn't its movement transfer instantly from planet Earth to planet Cat thus allowing me to immediately wake up my lazy? Obviously not, as that would violate some pretty important laws, as far as I know. Thank you for taking the time to read, could you please tell me where the flaw is?
 
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There is no such thing as a perfectly rigid material. The speed of light forbids it.

Movement can only be transferred through a material object at the speed of sound of the material that object is made of. (Diamond, the hardest natural substance known, has a speed of sound of about 12km/s)
 
Well there probably isn't a planet Cat either ;)
So would the deformation of the mallot account for the delay?
 
Michele said:
Well there probably isn't a planet Cat either ;)
Perhaps, but the universe does not explicitly forbid it. So it is a valid component in your thought experiment. :)

Michele said:
So would the deformation of the mallot account for the delay?
Yep. Quite so. A physical connection - being necessarily much slower than the speed of light - would be a very poor way of transferring the signal.
 

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