# What would the local effects/affects be of a ring spinning near luminal velocity?

To better solicit more inline with what I'm trying to imagine, I'm editing my question, the original question is left below and removing the hard science tag, as that just seemed to cause issues, though I would like to get as close to reality as possible. Reading the site rules this seems the way to proceed, if not I do apologize. Mods do not hesitate to delete.

I do appreciate the feedback thus far.

The point I wished to get to was any affects a ring shaped object: -spinning from relatively imaginable speeds (%20-30-50 Speed of light) to admittedly ridiculous speed of %99.999 C.
-in an area of unoccupied space, outside of any atmosphere but within the orbit of its host star.
-The dimensions of the object are at this point arbitrary, But for starters arbitrarily approximately 1 mile diameter(1609.34m), 10ft. (3.048m) thick in all axes, and a rest mass of 500 tones.

There have been mentions of Frame Dragging, which lead me to things like the Unruh Effect. However I am still unclear and if these would be connected to this device. Further what the visual or detectable effects these phenomenon would exhibit.
If external source of light strikes the object, I assume it will reflect blue anti-spinward and red spinward? I find it hard to believe that there would be no other detectable effects of a point of mass spinning near luminal speeds confined to such a small area. Especially quantum effects?
Ex: One of the fasted masses ever detected was the "Oh My God" particle.

The Oh-My-God particle (OMG particle) was an ultra-high-energy cosmic ray detected on 15 October 1991 by the Fly's Eye camera in Dugway Proving Ground, Utah, U.S. At that time it was the highest-energy cosmic ray that had ever been observed.[1][2][3] Although higher energy cosmic rays have been detected since then, this particle's energy was unexpected, and called into question theories of that era about the origin and propagation of cosmic rays.

The particle thought to be a proton or neutron would/could this device throw off particles similar to this from impurities in the rings construction? Or from interaction with solar wind or dust particles? collision with micrometeorites?
Is it possible for inertial mass to create singularities or singularity like effects? However interesting this is I am more interested in the "I don't know what I don't know, so how do I ask" questions. Which I guess is considered fishing. :(

Finally, if anyone is interested, the pretext to this story is this.
After sending several fly by probes to a nearly solar system.(Epsilon Eridani) An early colonization ship was sent. on approach even before reaching the planet this anomaly was detected. Picking out a 1 mile wide object from a random point in the solar system requires some justification. And describing the object as they approach will also be a challenge.

A ring, at this point constructed of perfectly rigid "unobtanium", and size/mass dependent on what the effects are. For starters arbitrarily approximately 1 mile diameter, 10 ft thick in all axes, and a rest mass of 100 tones.

What would an observer see and be able to detect in the local area of space as the ring is spun up to %99.99 C? Would the geometry (height width thickness) of the right contribute to these effects? Any type radiation? Warping of spacetime? Gravitational anomalies? At what point would a ring like this fly apart from centrifugal(?) stress if constructed of the strongest conceivable material we know of, say nested carbon nanotubes ~150 gigapascals? Or is some kind of super science unavoidable to keep the ring together long enough to see anything interesting?

edit this ring is located in space, in an independent stealer orbit.

• Better get your order in for a big shipment of scrith -- that stuff takes a very long time to make... Nov 11, 2021 at 19:08
• Congratulations, you've discovered why you cannot have perfectly rigid bodies under GR. Nov 11, 2021 at 20:04
• Don't forget en.wikipedia.org/wiki/Frame-dragging. Nov 11, 2021 at 23:09
• The rigid body issue is called Ehrenfest paradox Nov 12, 2021 at 1:11
• You ask for hard science and then give your measurements in imperial units? That’s cruel, making us do math like that! At least put the metric translations in parentheses! :-)
– SRM
Nov 12, 2021 at 1:58

You said "near luminal speed", then stated What would an observer see and be able to detect in the local area of space as the ring is spun up to %9.999$$c$$. I will assume you missed a 9 at the left, for 99.999% of $$c$$.

An observer nearby would see nothing, because they would have their subscription to life cancelled in less time than it takes for the retina to send a signal to the brain.

This is similar to shooting a near light speed projectile in an atmosphere, although at a larger scale. From the ring's perspective, air molecules are coming at it at light speed. When they collide with the ring the very atoms in the air will undergo atomic fission due to the sheer amount of kinetic energy they will receive.

Suppose this rings teleports into some place with an atmosphere while already spinning. If every part of the ring has near luminal linear speed, it is not much different from the ring coming right at us at luminal speed in a straight line.

So we have a shock of 100 tons coming at us at 99.999$$c$$... $$E = \frac{mv^2}{2}$$, which can be rounded to $$\frac{mc^2}{2}$$.

See where this is headed? It's almost as if you had just teletransported 25 tons of antimatter to a place (which would blow along 25 tons of regular matter, for a total of 50 tons of mass converted into energy).

I am not 100% accurate there because I should probably have used relativistic mass, but at this scale it doesn't matter much.

Consider that 1 kg of mass, if fully converted to energy, has an output of 21.5 megatons of TNT. 50 tons would be like one teraton, which is like 25% more boom than Yellowstone's last eruption, or about half the blast from La Garita. For reference:

The area devastated by the La Garita eruption is thought to have covered a significant portion of what is now Colorado. (...) By contrast, the most powerful human-made explosive device ever detonated, the Tsar Bomba, had a yield of 50 megatons, whereas the eruption at La Garita was about 5,000 times more energetic.

So we are not talking about end of all life here, but more like having to update a considerable part of Google Maps. At least for the initial impact. What comes next might not bode well to the biosphere.

Now we have a persistent problem. You said your ring is indestructible. This means that it won't stop, and after the initial blast it might dig into the crust. It would continuously nuke it, sending debris into the upper atmosphere and space. People very far away would see a huge plasma ball first, thenthe mushroom cloud of a nuke, only it doesn't go away but keeps getting broader and broader as hours and days pass. At some loint, for which I don't have the math, a lot of that debris is going to come back down, heating the atmosphere and cooking living beings in the process. The ground is probably shaking throughout half the planet the whole time too.

Please give the ring a stop condition, otherwise this goes on until there is nothing left.

Alternate scenario: the initial blast sends the ring up. I am quite confident that 2,500 Tsar Bombas under you are more than enough to evict you from Earth with a launch mass of 100 tonnes. The reason being that Apollo 11 had a launch mass of just 28 tonnes but had waaay less punch than 2,500 Tsar Bombas[citation needed], and it made it at least up to the Moon. If your ring escapes the Earth, then life may have a chance.

• I can only point out my mistake of not specifying the ring does not exist within an atmosphere. I thought I had but must have been lost in edit. I have to give points on the picture you paint and the "hold my beer" feeling any dino killing asteroid might have now! I'm actually surprised it doesn't quickly end with the planet in a fine mist in orbit of the host star. Nov 11, 2021 at 21:38
• 9.999%… as you approach light speed, decimal points tend to slide left. ;-)
– SRM
Nov 12, 2021 at 2:24
• @SRM thanks, fixed. Nov 12, 2021 at 3:07
• I really don't see how this wouldn't turn into an extinction level event in less time than it took you to type this answer. Dec 8, 2021 at 4:23

Can't help you on what if any relativistic effects you might get from your spinning ring, but I can tell you how to calculate how fast it can spin for any given material.

For a spinning ring, it's really fairly simple: multiply the mass of half the ring by the component of its spin gravity that's perpendicular to an arbitrary "cut plane" and you'll have the load on any cross section of the ring (don't divide by two -- there are two supports, but each ring half is supporting the other, so your mass is doubled too).

Therefore, if you know both the tensile strength and density of your material, you have half of what you need. The other half is the centripetal acceleration equation: V^2/r (in this case, you have V because you specified it).

Hint: make the ring bigger and it'll hold up better, because you're dividing by the radius. So, multiply mass of that half-ring (density * volume) by centripetal acceleration (distance over squared time) and you get the "weight" of the half-ring. Divide by the strength and you get cross sectional area -- if that's a finite number, this isn't completely impossible for your chosen material.

Worth noting that this is a worst-case for strength; the actual "weight" of each ring half will be less than this because most of the spin "gravity" isn't perpendicular to the "cut" plane -- so the actual load will always be less than this naive calculation suggests (and forty years ago, I might have been able to do the calculus to say how much less).

• Ahh, good point - you spotted that there's two questions here. Nov 11, 2021 at 20:11
• Thank you for the answer. It does help strengthen the framework I'm working with to get to my goal. Whish is actually more a question of.... how to put it? Weird effects of a what happens to spacetime or basic the environment when you are near a mass moving near light speed. I want to minimize as much as possible handwaving. Thus if I get something sufficiently astounding happening at just %50C it will bring it closer to believability. Nov 11, 2021 at 20:39

There have been mentions of Frame Dragging

I would expect those to be negligible, even if the mass of the object (which would need to be kept together by magic, otherwise it would collapse into a black hole) is substantial.

Further what the visual or detectable effects these phenomenon would exhibit.

It would be extremely bright in all bands, because any material particle coming in contact - and, given its mass, the object would be actively sucking in interplanetary matter and dust - would be annihilated.

Any momentary charge asymmetry on the ring's surface would also become a source of electromagnetic radiation.

If external source of light strikes the object, I assume it will reflect blue anti-spinward and red spinward?

Yes, exactly. Except that at those speeds, "blueshift" means that the sun's radiation is reflected back as anything from ultraviolet to hard X-rays. The ship's detector cannot fail to identify it, unless they approach near-axially, and from the spectral distribution it would be obvious that they're looking at a relativistic spinning object.

All of the above also means that the ring will require some sort of energy source to keep spinning and replace the energy lost.

• Collapse to a black hole? This is the first I this has came up? Yes, to flying apart or antigravity cones but not collapsing into a singularity? If you could get past the EM, photonic radiation. Would the ring visually appear to be spinning, or hardly moving (relatively (pun intended?) Nov 22, 2021 at 19:00
• Well... what would happen, I don't think it can be easily derived because such a ring cannot spin at that speed. The centripetal acceleration would be the squareof the peripheral velocity divided the radius, and a relativistic peripheral velocity is already huge before any squaring :-). If it could, the ring would undergo a Lorentz contraction and, indeed, its volume of space would be distorted (you can find some of this under "Ehrenfest Paradox" or "Kaluza's conjecture on relativistic spinning discs"), and it is conceivable that the ring would fall inside its own event horizon. Nov 22, 2021 at 19:27
• Is the singularity solely an effect of the Lorentz contraction or something else? Nov 22, 2021 at 20:29

The short answer to your question is: It would look like a white hole. The reason is simple: In Hilbert's In FOUNDATION OF PHYSICS FROM A THEORY OF EVERYTHING TO A CONSTITUENT OF GENERAL RELATIVITY by Hilbert states that particles moving at a little more than half the speed of light would produce an anti-gravity cone. Later Franklin Felber gave a precise solution, 57% of C and you will have a propellant capable of moving almost at the speed of light that will accelerate you slowly but in your case it is more than 99% of the speed of light. The effect would be the same but much more violet, anything trying to approach would be repelled almost instantly except for light which would be extremely deformed in a gravitational lensing effect. What would happen to things like dust or hydrogen atoms in space, I put would become relativistic projectiles.

sources:
Exact 'antigravity-field' solutions of Einstein's equation:
https://arxiv.org/ftp/arxiv/papers/0803/0803.2864.pdf
Test of relativistic gravity for propulsion at the Large Hadron Collider: https://arxiv.org/ftp/arxiv/papers/0910/0910.1084.pdf FOUNDATION OF PHYSICS: FROM A THEORY OF EVERYTHING TO A CONSTITUENT OF GENERAL RELATIVITY: http://www.bu.edu/cphs/files/2015/04/2007_Renn-Stachel.pdf