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

[Michele]

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?

 

[DaveC426913]

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)

 

[Michele]

Well there probably isn't a planet Cat either ;)
So would the deformation of the mallot account for the delay?

 

[DaveC426913]

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. :)

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.

 

[sardar]

Hello, thank you for sharing your thoughts on light cones. It is always exciting to see people still interested in physics, even after taking a different path.

To address your question, the flaw in your reasoning lies in the assumption that the mallot's movement would transfer instantly from planet Earth to planet Cat. In reality, nothing can travel faster than the speed of light, which is approximately 300,000 km per second. So even if the mallot was made of a non-deformable material, its movement would still take at least 1 second to reach planet Cat. This is because the mallot's movement would have to travel through space, which is governed by the laws of physics, including the speed limit of light.

Additionally, the concept of light cones and causality is not limited to physical objects, but also includes information and signals. So even if you were able to somehow instantly transfer the mallot's movement to planet Cat, the information of the strike would still take at least 1 second to reach your cat's ears, as it would have to travel through space.

I hope this helps clarify your understanding of light cones and causality. Keep exploring and questioning, as that is the essence of science. Best of luck on your journey!