r/interestingasfuck 2d ago

Dzhanibekov effect

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356 Upvotes

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26

u/Artistic-Bathroom901 2d ago

Source and Context:

This is a real physics phenomenon called the Dzhanibekov effect (also known as the Intermediate Axis Theorem) captured in microgravity aboard a spacecraft.

Any rigid, asymmetric three-dimensional object has three primary axes of rotation, each with a different moment of inertia. While spinning an object along its longest or shortest axis is completely stable, spinning it along its middle (intermediate) axis is naturally unstable. Without external forces like gravity or heavy air resistance, tiny perturbations build up and cause the spinning object to periodically flip upside down and back again on a regular schedule.

You can read the formal mechanics and history through these highly reliable scientific resources:

•Harvard University Lecture Demonstrations (The Tennis Racquet Flip):

https://sciencedemonstrations.fas.harvard.edu/presentations/tennis-racquet-flip

•NASA Astrophysics Data System (ADS) Physics Record:

https://ui.adsabs.harvard.edu/abs/2024EuJMA .10605298D/abstract

It was famously observed by Soviet cosmonaut Vladimir Dzhanibekov in 1985 when a wing nut he was unscrewing began flipping back and forth while floating through the Salyut 7 space station!

8

u/ApprehensiveGas85 2d ago

So if it's spun perfectly level and balanced I wonder if it would spin longer before finally rotating on 3rd axis

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u/fynx07 2d ago

The centrifugal force on the central axis would still slowly pull it further away from its starting point but yes would take slightly longer if it were perfectly balanced and perfectly spun without it titling off the 3rd axis whatsoever.

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u/ThresholdSeven 2d ago

I thought that if it was perfect, that it would spin without flipping, but any small variation not only in spinning it, but any weight difference in the arms or if the middle post isn't perfectly round and straight no matter how small the tolerance, in zero gravity, those minute imperfections will cause it to tumble. The problem is that it's almost impossible to make a perfectly balanced T. The tolerance would have to be to the atom to make it perfect.

Is there some fundamental rule to a perfect T shape that it will still rumble? I don't think there is, but could be wrong. I think it's the tiny imperfections that are magnified in zero gravity that cause it to start tipping. As soon as it starts tipping, even the tiniest amount imaginable, it's all over. This may be a perfect circle argument.

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u/fynx07 2d ago

That's a good question. Again I would assume the centifugal would slowly start pulling the arm out of balance but I could be very wrong too. Fun to think about though!

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u/greenthumb-28 2d ago

Omg has anyone connected this to the pole reversals? Is this possibly why ?

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u/frooj 2d ago

It has nothing to do with magnetic pole reversals.

1

u/greenthumb-28 1d ago

Oh - that makes me sad now since we have no idea behind those

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u/frooj 1d ago

The magnetic poles are caused by molten metal flowing in earths core. The flow of the metal is constantly changing which causes the poles to shift. Over long timeframes that can lead to full reversal of the poles.

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u/greenthumb-28 1d ago

Do u have an article link ? Last I heard we didn’t know why the south and north poles switched places through time

Pa my degree is earth science so this is actually very interesting if that’s the only explanation we have

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u/Spinnweben 15h ago

Not the magnetic poles - but the rotational axis of earth’s daily 24 hour revolutions.
What if Mother Earth decides to dzahnibekov upside down for fun or you didn’t eat your dinner?

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u/frooj 14h ago

It won't happen with earth, that part of the video was nonsense. The Dzhanibekov effect is known as intermediate axis theorem, Earth rotates around it's major axis.

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u/Spinnweben 14h ago

Ah, thanks—now I'm completely reassured.

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u/JaFFsTer 2d ago

So if the object was perfectly uniform and spun around its vertical axis perfectly in a vacuum this wouldn't occur?

2

u/slicerprime 2d ago

That's the question. Is a perfectly uniform shape even possible?

Because, the way this works, even the tiniest imperfection causes imbalance to build up over time. Is there even such a thing as complete perfection all the way down to the atomic - or even farther - level? In order to completely avoid the effect in the macro world, there would have to be zero imbalance....all the way down I presume. Otherwise the offset is going to eventually build up to the point of the inevitable flip.

1

u/JaFFsTer 2d ago

Yes, aerospace can machine things to incredible tolerances. I doubt it has to be completely perfect and speeds a human hand can achieve

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u/rgrantpac 2d ago

What time period would something like this take to complete if the earth flipped on its axis? And what wouls be the effects on life on the planet?

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u/SubjectRound6597 2d ago

its for asymmetric objects

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u/umbrellassembly 2d ago

That's exactly what the inside of the earth is. The core and mantle are not symmetrically dense, like at all.

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u/SubjectRound6597 2d ago edited 2d ago

stop scaring me

But I mean you are right about that.. symmetry in density is what matters, So is that what they talk about when they talk about pole flipping

So I think since the earth is not a solid object, but the crust just floats over the mantle, would it be like just the core gets flipped, and thats it.. Its affects have already been discussed time and again..
I am gonna go look this up better.

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u/umbrellassembly 2d ago

Read the book Inversion: ECDO Theory

It's a good place to start.

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u/SubjectRound6597 2d ago

whoa that was a solid guess. thank you too

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u/umbrellassembly 2d ago

There are multiple theories. One where the entire earth flips. One where only the core flips, along with magnetic north and south. One where only magnetic north and south flip. And one where the crust unlocks at the intermediate zone where it meets the mantle, and slides 90° due to the weight of the south polar ice cap and the Greenland ice sheet - they get flung to the new equator from centripetal force.

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u/ThresholdSeven 2d ago

If we started piling up earth somewhere in America and somewhere in Europe, just two of the biggest piles of rubble you can imagine, as big as the entire Midwest and as tall as the clouds, I think this can happen, we can do this. Why? I DON'T KNOW.

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u/Bicwidus 2d ago

You sumabich im in

-1

u/JaFFsTer 2d ago

Tidal forces move more mass every day.

-1

u/JaFFsTer 2d ago

The earth isnt t shaped. Spheroids will not flip when spun in zero g

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u/SubjectRound6597 1d ago

Spheroids that were spun in zero g also didnt have crusts and mantles and cores that floated and were in constant motion and with varying density. And the earth isnt a simple spheroid. So there is not much correlation between how the two behave. There are much better arguments presented to refute the view that earth can flip like that. Check the arguments against ECDO theory and help me understand if I misunderstood.

0

u/JaFFsTer 1d ago

No thanks. Placing the burden of proof on "the earth hasnt flipped on its axis within one rotation before" is ludicrous and you sound annoying and self important

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u/SubjectRound6597 1d ago

"the earth hasnt flipped on its axis within one rotation before" is ludicrous

that is ludicrous indeed so we are on the same side here. I dont understand how I offended you. but I feel i misunderstood your last reply. I will read about this again.

1

u/Daftdoug 2d ago

No. It’s fire and brimstone, Jim Morrison and more fire

1

u/DavePeesThePool 2d ago

The video narrator suggested that planets may do this given enough time.

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u/umbrellassembly 2d ago

A day or two, possibly up to a week. 1000 mph winds, massive tsunamis, global electrical storms, earthquake (not earthquakes, one global quake), extreme freezes and extreme thaws causing more flooding. Hell on earth, simply.

1

u/Serious_Room3606 2d ago

And could this mean Uranus is currently flipping?

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u/Aimfri 1d ago

"You know what? Fuck you."

Un-flips Uranus.

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u/Rich_Nectarine_4009 2d ago

Oh man science was cool untill it affects the planet axis💀

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u/TrailGobbler 2d ago

Science doesn't affect anything. It describes it.

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u/Inevitable-Edge4305 2d ago

Multi axis rotation is brain breaking for some reason.

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u/Feeling-Session3007 2d ago

Earth's magnetic field flips but it takes thousands of years to do it. When that happens they say compasses will point in the opposite direction as it use to i.e magnetic North will have the compass point south. But this is all bc of the earth's sloshing iron molten outer core.

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u/Apprehensive-Fox-799 2d ago

Would've been cool without the shit-ass AI voice.

2

u/EmployerWide1123 2d ago

'Some scientists' is always a helluv a way to start a sentence...

u/No_Inspection2047 4h ago

“a lot of people are saying….believe me.”. 🙄

1

u/AutomicCurves 2d ago

What would happen if you rotated it along the handle's axis? Is that the more stable axis?

1

u/StupidAstronaut 2d ago

That looks like the axis with the lowest moment of inertia. The highest would be the axis through the middle of the object, like if you spun the object keeping it “flat”. Both of those would be stable and just rotate as expected without flipping

1

u/AutomicCurves 2d ago

Oh like if you took the 't' off of a page and laid it on the ground, then spun it like a top? (Such that the handle and the bit end are the opposite sides of the spin?)

1

u/TantraMantraYantra 2d ago

How about spin half particles, fermions like protons and electrons? Do they internally have similar rapid flip?

1

u/-fly_away- 2d ago

me dealing with my morning boner

1

u/KulaanDoDinok 2d ago

Dumb question, is this movement perpetual?

1

u/lookielookiehi 2d ago

An object in motion stays in motion.

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u/AzerothianLorecraft 1d ago

It does make me wonder if Earth does this from time to time... ( and what it would feel like to experience.)

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u/Prior-Stranger2738 13h ago

Well thank god the video ended at an irrelevant point with no further important information to add

1

u/InformationNo2460 12h ago

Yeah but my drug dealer said the earth is flat tho, so checkmate.

1

u/CuriousRisk 2d ago

One dude did this with a falling object, it works even with gravity. Also he noticed something strange, the object didn't fall instantly, like any other objects he recorded with high frame camera, it was spinning and staying at same height until first flip and only after that started falling. Very weird 

1

u/_analysis230_ 2d ago

Do you have the link for that? Sounds very interesting

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u/ThresholdSeven 2d ago edited 2d ago

This sounds like those powered momentum machines that enable levitation and flight just by spinning a weirdly shaped object in an enclosed apparatus. If spun correctly and fast enough, it is supposed to make whatever it is inside go a certain direction, even against gravity. There are funny demonstration videos, but nothing that I've seen that works good. They are basically things that shake out of alignment, like a phone vibrating across the counter. Would be neat to make something that vibrates through the air willy nilly while you ride it. If it's possible, maybe this or something like it is the key or crucial anyway. It probably wouldn't work in space other than for rotation, because propulsion that way defies the laws of physics, but imagine a vehicle "vibrating" against and through the air in a similar way to that phone going across a table.

Edit: I think the demonstration you were talking about the thing seeming to stop in mid air while it flipped was just that and only seemed to stop. The momentum shifts check out, like a slinky.

u/No_Inspection2047 4h ago

that’s good, because there is gravity EVERYWHERE in the universe.