Sixty Symbols - 2017-05-11
Mach's Principle and Centripetal vs Centrifugal Force. More links and info below ↓ ↓ ↓ Patreon: https://www.patreon.com/sixtysymbols Some extra clips from this interview: https://youtu.be/Y4_NBjZthyE This video features Professor Mike Merrifield from the University of Nottingham... https://twitter.com/ProfMike_M Additional editing and animation by Pete McPartlan Gamma Trilogy of videos: http://bit.ly/Gamma3 Prof Merrifield on Objectivity: https://youtu.be/PccGklgNlHs Discuss this video on Brady's subreddit: https://redd.it/6ajxjt Visit our website at http://www.sixtysymbols.com/ We're on Facebook at http://www.facebook.com/sixtysymbols And Twitter at http://twitter.com/sixtysymbols This project features scientists from The University of Nottingham http://bit.ly/NottsPhysics Sixty Symbols videos by Brady Haran http://www.bradyharanblog.com Email list: http://eepurl.com/YdjL9
Brady's really learning to be a scientist. His questions get better and better. And his answers and retorts too.
Sir Martyn's influence.
I pretty much don't get anything...I don't know why I aways lose my time here ...but I keep coming...I don't watch nothing about my graduation but I love his channels
Brady's questions have always stood out. I've been remarking on it since the very early days of periodic videos.
Really love how a rotating bucket with water in it is one of the most controversial experiments in the history of physics.
All I understood is that if the whole Universe rotates crickets start chirping.
I love how the silver play button is just propped up on a stack of binders in the back of the room
Did anyone notice Wilhelms scream? 1:13
I don't think they meant the animation as a 100% accurate representation of reality.. :) I think what they tried to visualize was how someone in the cylinder would continue in a straight line in the direction the cylinder is spinning.
neebs.....you're fired.
I'm just your everyday broom salesman. That killed Titanus. Twice. No, it was three times actually!
taascheee
You mean the Stormtrooper scream ?
"You could make the universe rotate if you wanted to" -- love his positive can-do attitude!
I love watching the whole catalogue and witnessing Brady's "well hang on a minute" questions get increasingly insightful. I can see why teachers are so passionate about their work.
It's a constant excelleration.
And I love that Xkcd comic.
4:20 where I draw the line of "I think you're complicating this a bit too much for me"
You´re great! I love your enthusiasm explaining everything and how clearly you express your ideas!!
Mach's principle gives me hope that we might be able to detect a larger multiverse.
why? It rather suggest the opposite
4:55
MADNESS
I love how you use the Wilhelm Scream in your videos... This is the second time I notice it :)
they said "somehow" a lot:)
I've always wondered about this, and now I can still wonder about it! Thanks
Amazingly well done. You can see a lot of effort went into animations etc.
Keep it up. :)
Just found this and boy am I learning. Thank you for making these!!! I love your video on reynolds numbers
best thumbnails on YouTube!
how good are the animations here - great work whoever did those!
Thanks for a new 60 symbols video. I get excited when new ones come out. I watch your other channels but this one impacts me the most. Keep em coming Brady!
Is there a relation between dark energy and quantum field theory?
This made my head spin right round
By the way thank you
I get it now, finally. thanks.
Can you Please make a video about the physics behind fidget spinner tricks?
thanks for the video :D
Got dizzy. Great vid!
Love those Pete animations.
Whats the thought experiment with the sphere around a pendulum called? I really want to flesh out the idea cos it blew my mind
I was thinking of the xkcd comic when i read the title, then it appeared immediately in video! Nice!
What if I were floating in a spinning room?
Whoah, wind back to 6:40 for a moment. Does that mean if you made two spheres, one of thick lead, one of thin aluminium, and hung identical pendulums swinging in each. Then if you spun both your lead sphere, and your aluminium sphere, that your pendulum in the lead sphere would rotate more than the pendulum in your aluminium sphere?
Is this a strong effect? Or are we talking something so tiny that it would take a century of rotations to effect it by 1 degree?
And is this effect outside of other known effects like movement generating a magnetic field and so on?
You need to look into the theory of general relativity to understand why, because this effect is not explained by classical mechanics. In the book ''Gravity: an introduction to Einstein's general relativity by James Hartle'' he covers rotational dragging of inertial frames, gyroscopes in curved spacetime and Geodetic precession only starting in chapter 14, meaning that it's pretty advanced stuff. And they only talk about what happens outside a rotating sphere, not inside. Basically, in GR, the curvature of spacetime is a function of the ''stress-energy tensor'' which contains a description of the energy/matter density, energy flux, momentum density and a pressure/stress tensor in each point in spacetime. So you can have weird gravity fields next to rapidly rotating objects, even some kind of twisting of space itself. This is too complicated for me anyway
It is a super tiny effect. For example, there is a satellite called Gravity Probe B which a few years ago measured the frame-dragging of the EARTH, and required extremely precise instruments and lots of time to do it. So your little spinning spheres of lead and aluminium are going to produce a completely unmeasureable effect :).
On the other hand, if you feel like flying near a rotating black hole, then there you will find the frame-dragging to be so strong that it drags spacetime around the black hole at the speed of light; such that within a certain radius it is physically impossible to not rotate with the black hole. This is only just outside the event horizon though, so be careful with this experiment :).
I'm very curious how this experiment was conducted to remove the influence of air within the outer rotating object, the torsion in the string and possible gravitational effects due to an imperfect other rotating object pulling unevenly on the pendulum.
This is called "rotational frame dragging" ( https://en.wikipedia.org/wiki/Frame-dragging ) and should be observable e.g. on rotating black holes. The maths goes over my head, though...
My name's Peter and I work in a lab. Once when I tried to rename the centrifuge "centripete" they accused me of being self-centred.
Just when you thought you knew it all.
I spy with my little eye An Introduction to Modern Astrophysics by Carrol and Ostlie
What if the "spinning room" turn fast enough for you to stand on the wall, but you'r still wearing rollers?! :P
I feel like this wasn't explained very well (that's not to say I particularly know what I'm talking about though). As far as I'm aware, the cause of centrifugal forces is the fact that mass will continue to move in its direction of travel, so when you rotate something the mass tries to fly out of the rotation and as such creates the centrifugal force. The only thing stopping it from flying apart is the material itself (or in the case of a room, the walls), which is why if you spin something fast enough it pulls itself apart as the material fails due to how great the forces are.
But the centrifugal force is really just the momentum of the particles.
I think saying that the universe is sending itself messages is very misleading as to what's actually going on.
Let’s do some math:
For a rotating body with mass m, radius r and tangential speed W, it’s kinetic energy E is:
E=(m/2)(W*r)^2
And so, if we shoot a big cannon ball at the room, the kinetic energy will be transferred to the room completely, and thus it’ll spin at:
W=((2E/m)^(1/2))/r
And relativists’ll say that either the Universe spins (at the same W) relative to you/the room (no movie reference intended ; P), or vice-versa; but since the Universe is bigger than the room, it would need to be less massive in order to spin as fast; but that’s not possible (i.e. stars, Earth, galaxies, black holes, etc...), therefore I guess rotating/Non-Euclidean spaces aren’t relativistic and can be distinguished with kinetic energy mathematics
I think it is pretty well communicated. The problem is that when you spin a gyro (or throw a ball in space for that matter) it seems to fly or stay "straight" compared to... the universe. If the universe has no global effect on the inertia of the ball or gyro why does it always stay aligned to the universe? Newton thought there is an "Absolute Frame" in which the movements he described take place. Mach says no, it must be the material in the universe acting upon the ball.
The thing is that how do you know the inertia is a fundamental property of an object? because those inertial forces that make effect in an acelerated object might be the result of all the gravitational and electrical interactión between the rest of objects in the universe that moves relative to this object and the object :P
@Hoo Dini the rotating frame of reference is not inertial frame and newton laws don't works in this frame and that is why we have to include false force namely centrifugal force to use of Newtons Law
@Zukaro Travon
>> If the entire universe was rotating around the room, then the particles would just stay in the same position as in that case they'd have no momentum.
Well I think at least Ernst Mach, Einstein and others would have disagreed with you. You should read about frame dragging and the Lense –Thirring effect.
>> Everything is moving it's just that we don't have an absolute way of measuring it yet, so we need relativity. But if we ever figure out an absolute measuring system then you could say all motion is absolute. I don't know if we'll ever find a way to do that but I wouldn't assume we never will.
No, relativity isn't just some aid we developed to serve a purpose. If physical reality doesn't match with reality the theory will be dismissed, but so far there is nothing that would suggest that what the theory describes isn't what is actually happening in physical reality. The reason we can't measure uniform motion isn't just because we have not been able to figure out some measuring device that we could be able to figure out in the future, the reason (at least according to relativity) is that uniform motion/speed is relative and there can never be anything that could be used to absolutely measure something that isn't absolute to begin with.
Whew that rotation animation made me dizzy
I thought I had these things figured out before I watched this video...
6:40 please someone explain this to me...
So if you have a sphere outside a pendulum, in an ideal vacuum, it would still rotate with the sphere?
Dear Professor, i like your sexy beard! Looks fresh ;)
I'm completely mystified here.
@palmomski, I have never been able to really understand the status of rotating frames in general relativity. I have read that a gravity field is associated to these, but I don't understand how it avoids the "faster than speed of light problem". The Mach principle was also a problem for Einstein. So, he did not solved it. General relativity states that the equations remain the same in all reference frames even accelerated ones, but then i would assume that some non physical terms would appear (like the coriolis force). Don't know exactly. By the way, galilean reference frames are not allowed to rotate relative to stars... So maybe Einstein imposed the same constraint ? I thought he had done better !
@jmiquelmb I slept on it and what you said makes sense to me, thank you. Even though it has always sounded really strange to me that accelerating is "not as relative" as simple motion. Then again, I have no idea what to think of what @lcdvasrm just said.
glad i am not the only one that got nothing from this video
If you remove the floor, you will just sit there floating. If you add friction in, or connect yourself to the system, then you will get pushed to the walls. So the reason machs principle exists is because of the non-conservative force of friction. And non-conservative forces are "non-conservative" because there is an extra degree of freedom to dump energy beyond use-able work. This increases the entropy of the system, and so information only appears to be getting introduced.
This always bothered me and I couldn't untangle it. Thanks. I never knew Mach figured it out. It's mysterious.
Great animation in this video!
0:11 xkcd 123 detected
Is this the first time XKCD has been used in these vidoes?
so basically... with pendulums we could find the center of EVERYTHING?
Beat me to it, I was going to tell him about the Foucault Pendulum :P
huh so there are actually intelligent ppl on this planet...
Apparently, we are at the center. And everything else is too.
You don't need pendulums for that. Every point in the universe is its rotational and positional center.
If anyone tells you that you're not the center of the world, tell them they're wrong because uncle Al said so.
I am Peto (informal of Peter)... :D
Peter Bočan I have another name!
Malik Hatch - 2017-05-11
when you've been watching sixty symbols long enough to watch the professors go grey
Pass The Butter Robot - 2017-07-25
Maybe he's been gray for ages but he's just stopped dying his hair & beard...
Dave Crupel - 2018-04-30
He has achieved the rank of Elder Alchemist
KLAbe - 2019-03-29
The "Just For Men" wore off that is all.