Speed of Light Could be Reached and Indeed even Exceeded

[James1355]

TL;DR

I'd like to invite the theoretical physicists here to this debate/proposal

If I mount a fast spinning motor - let's say a 250k rpm, inside a cylinder, and use this cylinder as the armature of the second cylinder that sits round the first one and has the same rpm with the angular velocity in the same direction as the first one, and continue building these layers of fast spinning cylinders in a concentric way outward, I'd reach a point where the inner most cylinder was spinning at speed equal to the sum of all cylinders. Given sufficient layers of spinning cylinders, the inner cylinder would eventually spinning at or greater than speed of light relative to the background.
I could contain the whole assembly in a vacuum chamber to eliminate the drag, and incorporate brushless in conjunction with magnetic levitation in order to achieve a frictionless configuration.

Please let me know what are the theoretical challenges to my proposal.

 

[Ibix]

The tensile stresses and energy consumption rise without bound as you approach lightspeed. Thus, no matter how light your materials are you cannot accelerate your device to lightspeed with any amount of energy, and no matter how strong your materials they will disintegrate if you pump enough energy in.

 

[Dale]

TL;DR Summary: I'd like to invite the theoretical physicists here to this debate/proposal

Please let me know what are the theoretical challenges to my proposal.

Both theoretically and practically it would break apart. In rotational motion it works out that a material will fail at about the point where the tangential velocity of the outer edge reaches the speed of sound. This is nowhere close to the speed of light.

 

[James1355]

The tensile stresses and energy consumption rise without bound as you approach lightspeed. Thus, no matter how light your materials are you cannot accelerate your device to lightspeed with any amount of energy, and no matter how strong your materials they will disintegrate if you pump enough energy in.

I am not talking about acceleration. My idea is about a set number of angular velocities that each require small amount of energy, and its the total sum of the individual velocities that adds up to speed of light relative to the background while keeping each individual spin Constant hence no need for any acceleration at all

 

[James1355]

Both theoretically and practically it would break apart. In rotational motion it works out that a material will fail at about the point where the tangential velocity of the outer edge reaches the speed of sound. This is nowhere close to the speed of light.

I beg to differ , ETH Zurich's Department of Power Electronics created a drive system in cooperation with its industrial partners that exceeded 1,000,000 rpm in tests.

 

[topsquark]

I beg to differ , ETH Zurich's Department of Power Electronics created a drive system in cooperation with its industrial partners that exceeded 1,000,000 rpm in tests.

Okay. You've asked for theoretical objections. You got them and you disagree with them. So, what you need to do now is show that those objections are, indeed, incorrect.

Go build a FTL device and prove us wrong.

-Dan

 

[Ibix]

I am not talking about acceleration. My idea is about a set number of angular velocities that each require small amount of energy, and its the total sum of the individual velocities that adds up to speed of light relative to the background while keeping each individual spin Constant hence no need for any acceleration at all

This makes no sense at all. If you aren't going to listen to people pointing out glaring flaws in your thinking, I suggest you take @topsquark's advice from the post above.

 

[Frabjous]

I beg to differ , ETH Zurich's Department of Power Electronics created a drive system in cooperation with its industrial partners that exceeded 1,000,000 rpm in tests.

How big is it?
if it has a radius of 10 cm, that gives a maximum velocity of ~10000 m/s which is around twice the sound speed of most metals. A factor of 2 does not invalidate @Dale argument.

 

[James1355]

Okay. You've asked for theoretical objections. You got them and you disagree with them. So, what you need to do now is show that those objections are, indeed, incorrect.

Go build a FTL device and prove us wrong.

Okay. You've asked for theoretical objections. You got them and you disagree with them. So, what you need to do now is show that those objections are, indeed, incorrect.

Go build a FTL device and prove us wrong.

-Dan

I've just illustrated that the so called theoretical objections you referring to are neither theoretical nor objections as experimental devices have already been built and tested to the contrary. I'm looking for proper scientific debate based on what is currently technologically available. In my field (experimental and applied physics), we habitually laugh off belligerence and petulance exhibited by those who are good at convincing themselves the reason for they don't grasp a concept is because they'd like it not to work

 

[Dale]

I beg to differ , ETH Zurich's Department of Power Electronics created a drive system in cooperation with its industrial partners that exceeded 1,000,000 rpm in tests.

Usually when someone says “I beg to differ” the subsequent statement is a counter example. Yours is not. You gave the rpm, but my statement was about the speed of sound and the tangential velocity. Neither of those are in your purported counterexample.

Beyond the inevitable breakage, there is another issue. The energy required to spin the device would become unbounded as the tangential velocity approaches $c$.

I've just illustrated that …
experimental devices have already been built and tested to the contrary.

You have not

 

[Dale]

A factor of 2 does not invalidate @Dale argument.

Indeed, my “at about the point” is an “order of magnitude” statement. It should fail somewhere between approximately 0.1 and 10 times that speed. If this device exceeded the speed of sound by a factor of 100, then I would agree that it would represent a valid counterexample and I would need to revisit the derivation and see what assumption was violated.

 

[Ibix]

Beyond the inevitable breakage, there is another issue. The energy required to spin the device would become unbounded as the tangential velocity approaches $c$.

As far as I can work out, OP thinks this is not a problem because something something adding angular velocities.

I think he believes that if he has a cylinder doing 1rpm by driving itself aganst another cylinder that encloses the first, and he accelerates the outer cylinder to 1rpm, the inner cylinder will reach 2rpm without needing to gain energy or accelerate. Or at least with no energy input beyond that needed to accelerate the outer cylinder to 1rpm.

 

[James1355]

How big is it?
if it has a radius of 10 cm, that gives a maximum velocity of ~10000 m/s which is around twice the sound speed of most metals. A factor of 2 does not invalidate @Dale argument.

You are right. A mere 1,000,000 rpm on a 0.1m diameter would be equivalent of (2×π×r)×1000000)/60=10471

My argument is, by placing that inside

Usually when someone says “I beg to differ” the subsequent statement is a counter example. Yours is not. You gave the rpm, but my statement was about the speed of sound and the tangential velocity. Neither of those are in your purported counterexample.

Beyond the inevitable breakage, there is another issue. The energy required to spin the device would become unbounded as the tangential velocity approaches $c$.

You have not

That's why I have proposed the hollow cylindrical configuration to minimise the impact of tangential velocity.

 

[Ibix]

That's why I have proposed the hollow cylindrical configuration to minimise the impact of tangential velocity.

This is nonsensical. The inner cylinder either has a tangential velocity greater than $c$ (in which case the argument about infinite energy requirements obviously stand) or it doesn't, in which case this is just some nested cylinders.

 

[James1355]

As far as I can work out, OP thinks this is not a problem because something something adding angular velocities.

I think he believes that if he has a cylinder doing 1rpm by driving itself aganst another cylinder that encloses the first, and he accelerates the outer cylinder to 1rpm, the inner cylinder will reach 2rpm without needing to gain energy or accelerate. Or at least with no energy input beyond that needed to accelerate the outer cylinder to 1rpm.

This is nonsensical. The inner cylinder either has a tangential velocity greater than $c$ (in which case the argument about infinite energy requirements obviously stand) or it doesn't, in which case this is just some nested cylinders.

In 2020 researchers at Purdue University used a nano scale rotor achieving 3billion rpm.

 

[James1355]

How big is it?
if it has a radius of 10 cm, that gives a maximum velocity of ~10000 m/s which is around twice the sound speed of most metals. A factor of 2 does not invalidate @Dale argument.

Couldn't find the technical details but I assume it's pretty small,as another group of researchers at Purdue University achieved 3 billion rpm rotor on a nano scale

 

[Ibix]

In 2020 researchers at Purdue University used a nano scale rotor achieving 3billion rpm.

...and it still does not exceed light speed.

 

[James1355]

...and it still does not exceed light speed.

The sum will

 

[Ibix]

The sum will

No it won't, because even if you could build nested cylinders powered by the thing, it'd require infinite energy to get anything to light speed

You cannot get around relativistic kinetic energy by repeating "angular velocity" as if it were a magic spell. Rotation does not exempt anything from the laws of physics.

 

[DrGreg]

Velocities in relativity don't "add" the way they do in Newtonian physics.

If

• B moves at velocity $u$ relative to A
• C moves at velocity $v$ relative to B
• C moves at velocity $w$ relative to A

then it is not true that $w = u + v$ (for parallel velocities). The relativistically correct formula is$$
w = \frac{u + v}{1 + uv/c^2}.
$$In particular, if $u$ and $v$ are smaller than $c$, then so is $w$.

For example, if you try to "add" $0.9c$ to $0.9c$, you don't get $1.8c$, you get $0.994c$.

 

[berkeman]

Thread closed for Moderation...

 

[Dale]

After a very brief discussion amongst the mentors, this thread will remain closed.