plant growth is not doubled yet, but this is still really neat.
“We’re not at the point where we’re outperforming wild-type tobacco, but we’re on the right trajectory,” Gunn said. “We only need fairly modest improvements to Rubisco performance, because even a very small increase over a whole growing season can lead to massive changes in plant growth and yield, and the potential applications span many sectors: higher agricultural production; more efficient and affordable biofuel production; carbon sequestration approaches; and artificial energy possibilities.”
And I think that's what we are seeing in the video. The eddy current effect isn't permanent like in superconductivity. They have to keep moving the magnet around.
well that one looks great. Maybe in the original video a superconductive effect was there, but not strong enough to frame lock. But you can see it in the newer video.
In the video, it's when they stop moving the magnet, it maintains its position, neither repelling nor attracting.
Several physicists have spoken up and said this, and a few other tells distinguishes it from any conventional materials, which is why they made the video to begin with I'm sure.
That said I'm just parroting back the things I've picked up from this discussion.
Unmoving copper also neither repels or attracts a magnet.
Eddy currents impede movement of non ferrous metals in a static magnetic field. This looks like slow motion falling or resistance to spinning when the metal is in a fixed field.
This is how auto belays work.
If you move the magnet, the metal will also move since you're inducing a current and the fields from the eddy currents will react against the moving magnet.
That said, I'm enough of a layman not to be able to connect this explanation to what I saw in the video.
Are you saying because it wasn't moving in "slow motion," we can rule out non-ferrous metals? Or are you saying the alternating movement/stillness of the magnet shows this?
As I've said, I'm fuzzy on the details, so I'm relying on the expertise of the physicists here.
I can tell it doesn't react to a magnet in ways that I'm familiar with (copper, iron, other magnets), but that's all the detail I can tell from the video.
It's also suspicious that there's not a control sample of copper in the video. Any scientist trying to be thorough would have controlled for this - shown that you don't get the same effect with just a copper sample as you do with a copper sample that's been coated.
Well after seeing the second video I'm pretty convinced it's superconductive or a good scam. The effect was probably just not strong enough in the first video.
I'm suspicious of the magnet. Take a real close look in the second video: the paper cuts the image so the seam of the magnet blends with the table. But in the video it looks much more obviously like there's two magnets stacked on top of each other.
Which is a weird thing to do when for superconductors you shouldn't need it, but for pyrolytic graphite levitation you would (to get an N-S pole).
Well normal copper does this in presence of a strong magnet. I don't think we are seeing superconductivity, just regular copper Meissner effect. Super conductive would frame lock the copper. right?
There's also the problem of fine tuning -- why is the fine structure constant roughly 1/137? If it were different from its current value by a tiny amount, the universe as we know it wouldn't exist. Is the anthropocentric principal the only explanation we have -- it has the value it has because it produces a universe in which we're able to observe it?
And I guess less formally there's also the problem of complexity: condensed matter physics exists because trying to solve the standard model for a solid directly is both incredibly infeasible (think "cost of flipping bits in the calculation far extends that of all matter in the observable universe") and fails to capture the emergent phenomena in a natural way.
The other theory is there are infinite universes somehow being created all the time by every choice. Which to my mind isn't very Occam's Razor-ish. But it does exist as a theory.
You mean the Many-Worlds interpretation? That's not every choice, but every quantum measurement. And it's not necessarily an infinite number. And it's not a theory, but an interpretation. And it's actually very Occam's Razor-ish (at least that's what proponents claim), because it needs less postulates than the standard Copenhagen interpretation. The many worlds are a consequence, not a postulate.
IMHO, "Inflation" is false theory, because it doesn't obey law of conservation of energy.
If no inflation, then no Big Bang, so our Visible Universe is much older.
If our Universe is much older, then life evolved multiple times already. Red stars are shallow gravity wells, so they are primary target of an expansive civilization, because it easy to enter/exit them, so they are colonized first and their light is captured fully.
Conservation of energy is not the fundamental law it is often presented as. It is derived from Noether's theorem as applied to descriptions of the universe. Locally, it is true that energy is conserved, however, IIRC, General Relativity already can break it at large scales, even before we consider the fact that GR is incomplete and the real theory may break it even harder.
It is possible and I would judge even likely that some other value is conserved; that conservation of energy can be broken doesn't mean all chaos is unleashed and the Patent Office should revoke their ban on perpetual motion machines. When it is finally worked out, we may even pick up our "energy" label and move it to this new quantity. Depends on a lot of details we don't currently know. But what we today call energy is not necessarily conserved at large scales.
Saying that the universe can't do X because it violates conservation of energy is a circular argument; the precise definition of "conservation of energy" used by physics today is derived from our belief that the universe can't do X, but we also know our beliefs are incomplete. Very good approximations. Don't quit your day job to build a perpetual motion machine. But we are not in a position yet to even claim that our description of the universe is complete and we know the exact thing being conserved.
Cool story. Now explain why almost everything we see is moving away from us, where fresh hydrogen for stars comes from in an ancient universe, where the cosmic background radiation comes from, why the distant universe appears 'younger'...
Note that the 'laws' of physics are no better than normal scientific theories, scientists just had more hubris back then.
> Now explain why almost everything we see is moving away from us
(Not a native speaker).
Most galaxies in our galaxy cluster are moving away from us because of coincidence: Shappley attractor makes accretion disk by attracting mater from Dipole Repeller void[0], so our local group of galaxies is stretched along the way. At scale of our local galaxy cluster, Doppler Shift is responsible for majority of Red Shift.
At cosmic scale, Red Shift cannot be explained by Doppler Shift alone. If we take into account gravitational waves, then at least part of Red Shift can be explained by gravitational noise: gravitational waves are slowing down light a bit, so photon loses tiny bit of energy with every such interaction, which causes major part of Red Shift at cosmic scale.
> where fresh hydrogen for stars comes from in an ancient universe,
This is though question which is hard to answer. If elementary particles are bubbles, then they are popping up because something is stretching our Universe, i.e. our Universe is inflating ... oh, fck.
> where the cosmic background radiation comes from
[If inflation theory is false, no Big Bang, and visible Universe is much older, then]
Cosmic microwave background is just light from distant galaxies with large Red Shift z=1000 (light was stretched about 1000 times from galaxies in range of about 4 trillion light years).
> why the distant universe appears 'younger'...
James Webb infra-red telescope is proving that this assumption is false right now. Read the news.
We have a good idea where it comes from: It was created in the big bang, and as stars form (and explode, or form neutron stars and collide) they turn it into heavier elements. Over time there is less hydrogen, which is why the universe can’t be infinitely old. Since it’s only ~13.7B years old, the amount of hydrogen we see makes sense with our models.
It’s a much much bigger problem if the universe significantly older than we think it is… if we were to believe the Wikipedia article on this[0], we’d only expect stars to exist at all for about 100 trillion years, but given that the distribution of hydrogen availability is likely to follow an inverse exponential decay curve of some sort, we’d probably see much lower amounts of hydrogen much earlier than that.
> because it doesn't obey law of conservation of energy.
Energy is in general only conserved locally. More precisely, the covariant derivative of the stress-energy tensor `\nabla_{\mu}T^{\mu \nu}` is zero, but this can only be put into integral form in a few special cases.
I have a 2 year old desktop apple computer and GIMP gets about 2 fps for simple tasks like using the pencil to draw. (maybe it's better on linux or PC)
> Turns out the momentum from higher mass and the increased friction from higher mass balance exactly.
yes, in the spherical cow sense, but this isn't at all true for real life vehicles and tires. the weight of the vehicle does have a significant impact on traction, here's a quick video explaining tire load sensitivity: https://www.youtube.com/watch?v=kNa2gZNqmT8
related to the above issue (and as GP mentioned), the high CoG of an SUV also poses challenges for braking performance. you want all four wheels of the vehicle to have roughly similar braking force. obviously the front wheels are going to contribute more to braking than the rear, but you don't want a huge disparity. this doesn't matter so much for the abstract question of "how quickly can a vehicle stop?", but it matters a lot for the practical question of "which direction is the vehicle facing?" if the rear wheels are contributing much less of the total braking force, the car is likely to end up sideways. this is bad if you want to do something like "remain in control of the vehicle" while braking.
GP didn't claim that braking distance was larger because of higher mass. Rather, because of the higher centre of gravity the ABS has to be calibrated differently, leading to weaker braking, thus larger braking distance.
I have no expertise in this, but seems prima facie plausible.
I think simongr3dal’s remark isn’t about them taking longer to stop, but about the use of the term calibration.
ABS is a feedback loop: brake faster until just before the wheels start slipping. That doesn’t need calibration.
There may be additional logic in ABS systems for corner cases that requires calibration, though (for example, if your front left wheel has lots more grip than the other ones, can you brake full on it and keep the car going in a straight(ish) line?), but I don’t see how higher CoG would be a factor there.
Ah, fair enough, that makes sense. You're right, if we posit that ABS is purely to prevent slipping, that would imply that it always goes for maximum braking.
> I don’t see how higher CoG would be a factor there.
Could be that the "additional logic" (whether we call it ABS or something else) aims to keep certain values (such as longitudinal or lateral acceleration) within bounds (thus releasing brake pressure when approaching those bounds), and those bounds are tighter with higher CoG.
I remember the Mercedes A-Class (with pretty high CoG) rolled over in the Swedish Moose test initially, until that was fixed with Electronic Stability Control (how?).
“When ESC detects loss of steering control, it automatically applies the brakes to help steer the vehicle where the driver intends to go. Braking is automatically applied to wheels individually, such as the outer front wheel to counter oversteer, or the inner rear wheel to counter understeer”
So, ESC activates the brakes harder than the driver indicates through the controls, while ABS activates the brakes less hard than the driver indicates through the controls.
“Just as ESC is founded on the anti-lock braking system (ABS), ESC is the foundation for new advances such as Roll Stability Control or active rollover protection that works in the vertical plane much like ESC works in the horizontal plane. When RSC detects impending rollover (usually on transport trucks or SUVs), RSC applies brakes, reduces throttle, induces understeer, and/or slows down the vehicle.”
In the end, there can be only one set of commands that get sent to the brakes, throttle, etc, so these systems must be interconnected, making the terms more marketing than indicators of specific systems in the car.
“The concept for ABS predates the modern systems that were introduced in the 1950s. In 1908, for example, J.E. Francis introduced his 'Slip Prevention Regulator for Rail Vehicles'.
In 1920 the French automobile and aircraft pioneer Gabriel Voisin experimented with systems that modulated the hydraulic braking pressure on his aircraft brakes to reduce the risk of tire slippage”
> thus it's always the brake pads stopping the car, not the tires?
The tires are the only thing in contact with the ground. All deceleration force can only come from the grip between tires and the ground[1]. The brake pads in most installations can easily lock up the tires (which means now you only have sliding coefficient of friction instead of rolling friction). In other words, what matters is tire grip.
Buy the grippiest tires you can afford to run.
[1] Well, cars with aero downforce also get a lot of deceleration from that. A Formula 1 car will decelerate at more than 1G merely by lifting off the throttle, without touching the brakes. But none of this is relevant to street cars.
Even race cars running on slicks and weighing 700 kg get better braking by avoiding lockups and using the pads instead. So unless your pads are trash, you better get a proper ABS instead of imagining some magical tire with grip comparable to brake pads.
The above comment seems to be making a distinction that braking force comes from the tires or the brakes. That is not how it works.
The brakes provide friction to resist the spinning of the wheel, but of course only to the point that the tire can provide grip (friction) against the road surface.
Picture trying to brake with slick tires on wet ice. Nearly zero tire grip equals nearly zero braking force. Doesn't matter what kind of brake components are on the car. No grip = no grip.
If you want to be able to stop quickly to avoid accidents you need to maximize grip a the tire-road contact patch and you need to have a braking system powerful enough to fully take advantage of that grip.
Every car sold for decades now already has the latter (unless something is broken, obviously), so the variable you need to control is tire grip.
Thus: Buy the grippiest tires you can afford to run (if you want optimal braking to avoid accidents, that is).
> The brake pads in most installations can easily lock up the tires
> In the United States, the NHTSA has mandated ABS in conjunction with Electronic Stability Control under the provisions of FMVSS 126 as of September 1, 2012.
Just about any car can brake hard enough to lock up all 4 tires and enter a skid (or activate ABS to avoid this)- the limiting factor to braking distance is friction between the tires and the ground.
Scaling for static friction between rubber and asphalt does not follow the friction equation you are taught in high school physics class. Generally, for a given weight of vehicle, a larger tire surface area is able to produce more maximum braking friction. In other terms, minimizing the surface pressure and maximizing the surface area at the contact patch increases maximum braking friction.
Modern brakes can get a lot hotter before brake fade. Until the brakes get too hot it is just a matter of brake pressure. Modern cars universally have disk brakes which shed heat better. Larger vehicles also have bigger tires which leaves more room for brakes.
In short while you are not wrong, in practice even the worst numbers are still more than good enough that brake performance isn't an issue.
That would be true if your wheels instantly stopped turning when you applied the brakes.
The limiting factor for braking isn't the friction between your wheels and the ground, which is weight-dependent, but the friction between your brake pads and rotors, which is not weight-dependent.
Yeah, that's why it's as easy to come to a stop on well maintained tarmac as it is on ice, snow or gravel. As long as those brake pads work well that is.
I suggest taking your bike out and practice breaking on various surfaces. You will quickly get what the limiting factor is. It's the same with a car just the tires are much wider and brakes more powerful.
this isn't quite right either. most modern cars have brakes that far exceed the limits of grip for the tires. the brakes themselves should only be the limiting factor if you are riding them down a very long hill or performing multiple hard stops in quick succession (eg, racing).
“We’re not at the point where we’re outperforming wild-type tobacco, but we’re on the right trajectory,” Gunn said. “We only need fairly modest improvements to Rubisco performance, because even a very small increase over a whole growing season can lead to massive changes in plant growth and yield, and the potential applications span many sectors: higher agricultural production; more efficient and affordable biofuel production; carbon sequestration approaches; and artificial energy possibilities.”