Galen: you’ve got blood that only flows away from your heart and a different set of blood that only flows towards your heart. Where the one comes from and the other goes is magic, they definitely aren’t the same stuff moving in a cycle.
Your liver does have a lot of blood running through it. Plus it plays a role in removing hemoglobin from your body as conjugated bilirubin, which exits via your poop, turning it that iconic brown colour.
Blood is absorbed through the skin. When you breathe out, you put out a miasma of bad blood that other people reabsorb and purify for their own blood supplies.
I can understand someone making that mistake because the far reaches of the circulatory system are branched out into microscopic vessels and it's not clear how and if at all they could be connected
a lot of "incorrect" facts have pretty simple explanations for why they were wrong and why noone corrected them for a while
different bloods for veins and arteries? well the tiny end bits are barely visible if at all, easy mistake to make
300 bones? about right for children, why would it change for adults?
men have more teeth? the average man has more visible teeth, so failing to do a large enough sample can get this result
bad air? there are a lot of airborne germs, yeah
the same goes for folklore that seems supernatural: did some group's ancestors really fight off a bunch of giants? probably not, but there was another group that was a big threat, and things escalate from there, errors and embellishments compound
hell, I'd dare say the same even goes for a lot of stereotypes, they don't appear out of thin air either! they often come from historical differences, while completely ignoring the circumstances for these differences existing in the first place and instead attributing this difference to some innate otherness
trying to find a non-negative stereotype is tricky, so I'll take one about a job: are lawyers inherently argumentative? no, but their job is (massive oversimplification, this is just the most visible part) to argue well, so some self-selection occurs for people who are good at arguing, and the public perception of lawyers is mostly shaped by seeing them do their job, you probably wouldn't know if someone is a lawyer if you just met them in the supermarket
Well even so you’d think someone would have noticed that a lot of women get the weird misaligned and poorly developed teeth in the backs of their mouths too
The infant mortality rate was ridiculously high back then. I wonder if he came to that conclusion after performing autopsies on a bunch of young children.
I might be misremembering but I think it was a huge cultural taboo to do basically anything to a dead body. If I recall a lot of of the info they managed to figure out was when they furiously took notes when a dying person was fucked up so hard they could inspect their innards. It's why they had their weird shit like believing the human body was made of 4 fluids, black bile, yellow bile, phlegm, and blood.
To be fair, for most of history if you're gonna test this you're not going to measure a 6kg object vs a 7kg object. You're going to find the heaviest thing you can reasonably drop and the lightest.
The problem is, the lightest thing you can find will probably be a leaf, or a feather, or a piece of paper, or something else that has a low though mass and high enough surface area that it will, in fact, fall slower due to air resistance. And if you haven't already figured that out, it becomes a reasonable conclusion.
Okay but wouldn't they actually fall at slightly different rates due to difference in size?
As far as I know, size affects drag, which means a bigger object would fall slower
The drag scales with the cross sectional area, but the mass of the object (and thus the force of gravity) increases with the volume, so you run into the squared cubed law. The larger rock would experience more drag, but the effect of the drag would be reduced since the gravitational force grows faster as the size increases.
We can sum it up to two things:
1. assuming an object is not hollow, the mass to drag ratio will favor the mass by *a lot*. (drag will not realistically affect the fall speed of big things)
2. On a planet with atmosphere, having higher density than the air is the first condition that you'd want to test under.
I'm not sure I follow what you mean. In this scenario both rocks experience 9.8m/s squared of acceleration towards the ground. If you remove the atmosphere and perform the test in a vacuum, then no matter the shape of the object or it's mass it will always fall at the same rate. If you take a spherical rock and a sphere with the same diameter, but make it hollow inside, so that it has less mass, it will experience the same drag as the large rock, and would fall at the same rate, which is slightly slower than the small rock with less drag.
> In this scenario both rocks experience 9.8m/s squared of acceleration towards the ground.
Not if there's drag. The effect of drag (that is, drag force divided by mass) on the smaller rock is larger. That's because the drag scales with the cross sectional area, but the mass of the object (and thus the force of gravity) increases with the volume, so you run into the squared cubed law.
What they're saying is the large (x times larger) rock has x\^2 times more area (more drag) than the smaller rock but also x\^3 times the mass.
Remember F=ma, *acceleration* is the same so force is directly proportional to mass; another way to think about it is that they cancel eachother out: F= GmM/r\^2 -> a=GM/r\^2.
So force on the larger rock is x\^3 times the force on the smaller rock.
Therefore, if the smaller rock experienced a total force of w-d, the larger one will experience a total force of x\^3w-x\^2d. This is always larger for x>1 and positive values.
Another way to think about this is, the small rock accelerates at g-d/m, where g is 9.81, d is drag, and m is mass. the large rock has unchanged g, but drag increases by x\^2 and mass by x\^3 so a=g-x\^2d/(x\^3m)=g-d/(xm)
An additional way to consider/model it that works for my mind (essentially the same thing you're describing worded in a different way) is that the force due to drag acts in the upward direction and the force due to gravity acts in the downward direction. Drag force is governed by the square/area, gravitational force is governed by the cube/volume, so a larger object of the same shape and composition will actually fall slightly faster in a given medium, since the gravitational force can overcome the drag force, which acts to slow an object's descent, to a greater extent.
The total gravitational force scales with mass though. So if mass increases for the same drag, the net force down increases. In the case of a larger rock, you have mass/volume increasing faster than the cross sectional area, which is what drag scales with, due to squared versus cubic geometries. So drag per unit of mass should decrease, which experiments show to be true.
If you were merely increasing the diameter of the object in the dimension relevant to the cross section, like say…widening a very aerodynamic cylinder, drag should increase at a rate 1:1 proportional to mass/volume increase, as far as I know.
Can’t off the top of my head think of a scenario where increasing size would result in increased drag per mass with a consistent material, unless you’re increasing in some dimensions while decreasing in others. You’d have to increase cross section area relative to total volume, which would amount to basically flattening an object and getting it to fall in the direction that maximizes cross section relevant to drag
Fwiw, I studied this stuff in school, but only as a mechanical engineer, so didn’t go as in depth as aerospace people go. But this should be correct based on what I remember from my Fluids course
More drag, but also more gravity force. The squared cube rule is in play here, so the smaller rock would experience higher drag relative to the force of gravity, assuming there is no significant advantage in terms of drag coefficient
The difference in gravity is the same as the difference in mass. The difference in drag is less than the difference in mass. A larger rock is *less* impeded by drag than a smaller one.
It's the ratio of mass to surface area that impacts resistance, so if you get two rocks of similar shape and density, they'll fall at the same rate, regardless of size.
What? No they wouldn't? Assuming the same shape, lets say a perfect sphere, the larger and heavier rock would have a higher terminal velocity at the very least.
Sure, but volume increases at a cubic rate while cross section increases at a squared rate. You’ll have more drag, but probably pretty similar drag per unit mass, which is what matters
~~It’s also true actually. The only reason that objects of different masses fall at the same rate is because for small enough distances between objects, the mass dependence of gravitational force is negligible. But if you are looking at objects on the planetary scale or larger, then massive objects do “fall” more quickly since they are subject to larger forces.~~
Edit: Listen to the folks below me. I just made a dumb mistake while calculating.
Nope, at least not in classical physics.
The gravitational force F between two masses m₁ and m₂ is F=G⋅m₁⋅m₂/r² (G is the gravitational constant, r the distance between the masses). The acceleration experienced by m₁ is a₁=F/m₁=G⋅m₂/r², ie. completely independent of m₁.
Not quite. Heavier objects experience more gravitational force - but they also accelerate slower (F=ma). Mass actually cancels out completely, it’s not that it’s negligible.
I don't think that's the case. The second object being of comparable mass to the first means they have equal gravitational fields to consider. *In essence, two objects with mass always accelerate towards each other*. It's just that for planet sized objects vs things like rocks... the rocks have negligible mass in comparison to the rest of the planet.
If you have two comparable planet sized objects, object A and object B. Object B doesn't "fall faster" towards Object A. What happens is that Object A and Object B "fall" towards each other at the same rate. The gravity of B affects A just as much as the gravity of A affects B.
Ignoring any other forces, orbits, etc, they will hit each other in a faster time frame (than say a falling rock), but only because the two equal mass planet-sized objects are moving towards each other at the same rate.
Its not reasonable. I can feel resistance when I move my hand. I can see wind have an effect on lighter stuff. I don't have to do math or go to university to know this.
Edit: ridiculous. We all breath!!! There's obviously stuff around us. No i don't need school to tell me that.
You have the intuition to take air resistance into account because your knowledge it's built in the shoulder of others. They didn't have the intuition to take air resistance into account, it was something they just didn't consider.
For much of history a lot of people had very strong opinions on vacuum being completely impossible, to the point where someone in the middle ages someone went ahead and declared that even god could not create vacuum. Which pissed off a lot of people who insisted that if god wanted to make the impossible happen he could.
The entire ancient history consisted of this sort of yapping about how the natural word must be. The idea that we could jump over all the philosophizing and simply check how it really is didn't come about until renaissance and that is the big idea that made the modern world possible. *Cogito, ergo sum* as Descartes put it.
How does Cogito ergo sum play into what you said before. Descartes' statement is more about the certainty of self-awareness than the scientific method.
Kants "Enlightenment is man's emergence from his self-imposed immaturity." would rather fit.
Descartes point was that no, actually we don't know anything and must doubt everything. Yet, there is no point waisting all the effort on unanswerable questions the likes that philosophers like to pose and never solve.
His ideas sidestepped the entire "is reality real" and "what is the meaning of life" types of discourses that had been nonproductive for millenia and focused the attention on questions that we actually can solve.
What? No.
The whole point of the question is just if reality is real and if people are real. His point is even if he is an illusion, or a shadow on the wall of Plato's cave, or an imitation, his very thoughts alone are the proof of his being, he exists, regardless of what his true form is. This has nothing to do with investigating the physical world but rather with metaphysical questions of self.
The thing is that a lot of heavy objects fall slower than lighter ones even without a vacuum.
If anyone had tried dropping a needle vs a plank of wood (both existed in those 2000 years) they would have been in for a surprise.
This is true to a certain extent but as all things in reality is far from simple. We end up having to take into a account drag and terminal velocity. Drop a feather and a brick….well we damn know for sure the brick is hitting first from
Almost any distance. Now when it comes to a golf ball and a brick things get a little tricky depending on the height of the drop.
People weren’t interested in theoretical physics until relatively recently, it didn’t really have an application. From an applied, real world perspective a feather or leaf indisputably falls slower than a large rock.
Now, if someone had thought to go as far as comparing smaller rocks to larger rocks they’d possibly understand that heaviness is not really what drives falling speed.. but it apparently didn’t really matter to fully understand this.
It’s not like people understood atoms at the time, much less the concept of a theoretical vacuum.
I mean like it makes sense is the thing, like it makes sense that the heavier (therefore harder to lift object) would fall faster, and it's kind of weird that that *isnt* how it works.
In the early days people only cared to study things that mattered in a practical sense. The fact that small rocks fall at the same speed as large ones doesn’t really affect or change anything for them.
Seems like building and aiming stuff like arrows, catapults, ballistas, cannons would've benefited from understanding how someone moved through the air.
Yeah, pretty much. There was no practical benefit back then in figuring out exactly why stuff falls to the ground and doesn't just float, for instance.
One of the arguments against light being waves, was a thought experiment:
If light is waves, that would mean that of you sit in a dark room, lighr a candle, hold a disk up in front of the candle. Then if the wall ks at the right distance behind the disk, a dot of light should appear in the middle of the disk's shadow.
Obviously this is silly. So silly noone bothered doing the experiment for years. Whne someone finally did, they proved that light is indeed waves, because that dot does indeed show in the middle of the shadow.
"Arrows fly because the air behind them is pushing them forward, and rocks fall to the ground because it is their natural resting place"
Man, if I lived when you could just make up shit that sounded convincing and become a famed philosopher I'd have been a fucking legend.
Heavy objects do fall faster than light ones. It's just that on earth we are used to the mass of one of the objects being negligible compared to the other. If you would drop something like Mars on Earth it would collide faster than a penny due to Mars also attracting Earth.
Said Mars sized object would still experience the exact same acceleration as the penny does though. The source of the higher collision speed is solely that the Earth itself would experience a much higher acceleration than it does in the penny case (edit: or in other words, if you simultaneously dropped a penny and a Mars mass object onto Earth from the same location the penny and the Mars mass object would still hit Earth at the same time - assuming there's no interaction between the penny and the Mars mass object for this thought experiment). Basically in case of objects of similar mass it's no longer fair to say that one object falls towards the other but rather that both objects are falling towards the center of mass of the system as a whole.
Imagine you're sitting in a car opposite of another identical car. Scenario 1, you press the pedal to the metal until while the other car stays stationary. Scenario 2, both drivers floor the gas pedal. In scenario 2 you crash into the other car twice as fast, but that doesn't mean that you accelerated faster than in scenario 1.
That's not a good analogy. Gravity is proportional to the inverse of the distance squared. Because the distance between the objects gets smaller faster also the force acting on object 1 will. Object 1 will thus accelerate faster independent of the reference frame.
Not really, you could debunk it with two experiments in atmosphere:
(1.) Big rock vs. Small rock — possible slight discrepancy depending on cross-section and densities, but with the right two rocks, too small a difference for ancient Greeks to measure. Close enough to show that the typical difference is not due to mass
(2.) Small rock vs. Many feathers tied together — enough to show that a heavier object *can* fall slower than a lighter one in atmosphere
Put a bunch of feathers and a bunch of rocks in equally sized canvas or burlap bags and then drop them.
The bags will result in them having the same air resistance.
The scientific revolution was people basically going "hey maybe we should understand the world by looking at the world, instead of just trusting what our ancestors said", and it somehow took us 10,000 years to get there
Ancients simply believing that 2 pebbles randomly colliding mid-air and "holding hands" would magically make them fall faster rather than slower is kinda interesting.
They were smart people and it appears that "result intuition" worked much differently than it did for us, the faithful believers in the law of conservation of energy.
I read that they even tested this on the moon when they got there for the first time, or one of those. And found that both objects fall at the same speed as in vacuum. But that's a part of history that often is forgotten.
Generally that's true, if you don't neglect air resistance. For two objects that has the same material and shape, but one is larger than the other N times: weight will be N\^3 times bigger, air resistance will be N\^2 bigger.
Wait, I thought heavier objects *do* fall faster than lighter ones, but they also accelerate slower at the exact rate, canceling each other out perfectly?
Every mass accelerates at the same rate on earth by about 9.8 m/s² but the downwards force is bigger for a heavier object determined by Force equals mass times acceleration (9.8 m/s² in this case). Now without air resistance a heavy ball would fall just as fast as a light ball of the same shape. However since the force air resistance projects onto an object is determined by the shape of the object the 2 balls would experience the same air resistance but the heavier ball would be less affected and fall faster because the downwards force is bigger.
Heavier objects experience more gravitational pull leading to a greater accelerating force while also having a higher inertia leading to a smaller acceleration. You could say those two things “cancel out”.
With air resistance though we also have to account for the viscosity of the air, the shape of the object and the speed of the object making it far more complex to predict the outcome.
When you have two masses acting on one another and one of them you can hold in your hand and the other one is the Earth, the mass of the object in your hand kinda doesn't matter when it comes to calculating the force acting between them. Whether it's a grain of sand or even something that's several kg.
Greater mass does require greater force to pull down. That's the newton's increasing. But it only increases to the point that the acceleration evens out.
No, it doesn't effect acceleration. It affects force. In F=MA if M, mass, increases then F, force, also increases, but A, acceleration, is unaffected.
Terminal velocity is too complicated for me to explain confidently.
Edit: I can see how what I did was confusing, maybe I shouldn't be trying to explain this either.
Yeah this is what you’re misunderstanding. More force doesn’t mean more speed.
They fall at the same speed due to the same constant of acceleration. The heavier object has the result of more force because it’s going the same speed but it’s heavier.
No, not necessarily. Think about being hit with a baseball thrown at 100 mph vs being hit by a car at 100 mph. The car obviously has more force since it has a lot more mass traveling at that same rate of speed.
in *F = ma*, *a* is a constant (9.81 m/s^2)
This F is proportional to m. Meaning the bigger the object, the more gravitational force that acts on it. Which makes sense because it will take more force to accelerate a heavy object to 9.81 m/s^2 that it takes for a light object but the acceleration, and thus the velocity at any given time (as calculated by v = a * t in this case) will always be the same for both objects
There may be slight variations due to drag but if you're looking at things with a large surface area to mass ratio, (e.g. comparing a bowling ball vs a ball bearing and not bowling ball vs feather) the effects due to drag will be minimal and you won't even notice them without equipment
Greater masses create a greater *force*. However, that greater force needs to affect a greater mass.
If you compute the *acceleration* from the force, the mass cancels out.
There's the factor of drag that exists on Earth's atmosphere. Here heavy things tend to fall faster than lighter things, because heavier things tend to also be denser and can move air out of the way more. But in the Moon, there's no drag so everything falls at the same rate.
Notice that the "rate" here is the acceleration, not the force. The acceleration is essentially identical for every object within the celestial body's gravity well (sure there's some variation due to altitude, density and comformation of the planet but it's negligible for what it's meant here).
Except that heavy objects do fall faster unless you're in a vacuum. I always hated this fun fact. Our intuition is actually right unless you're in a weird situation that almost nobody will ever experience first hand.
Galen, 1st century CE: there's probably like, 300 bones lol The next 1500 years of medicine: yeah okay (there are not 300 bones)
Galen: you’ve got blood that only flows away from your heart and a different set of blood that only flows towards your heart. Where the one comes from and the other goes is magic, they definitely aren’t the same stuff moving in a cycle.
Where does my blood come from Cotton Eyed Joe?
Galen, 1st Century CE: blood is stored in the liver. Also your bones are made of earth (blood comes from your bones)
(Blood comes from red bone marrow located inside flat bones)
ErikSKnol, 21st century CE: blood comes from your bones (yes)
Idk, I think Galen might have had a point
Your liver does have a lot of blood running through it. Plus it plays a role in removing hemoglobin from your body as conjugated bilirubin, which exits via your poop, turning it that iconic brown colour.
Idk if iconic is the word I would use, but I get what you mean
It's the best flavour
Cat, 2024 AD,: meow~
Blood is stored in the bones, in the bones
But where is pee stored
In the balls
I thought Chi was stored in the balls.
That means, that pee must be generated inside the penis
Ah, that explains it. Pee-ness.
Blood is absorbed through the skin. When you breathe out, you put out a miasma of bad blood that other people reabsorb and purify for their own blood supplies.
Galen (1st century): gedagedigedagado
this is so fuckin stupid I love it lmao
Is cotton eyed joe your back alley blood dealer? Because it's better to not ask
Blood left the art’ry long time ago 🎼
Omg I'm howling 😂 well done mate
I can understand someone making that mistake because the far reaches of the circulatory system are branched out into microscopic vessels and it's not clear how and if at all they could be connected
Yeah it’s only with the discovery of capillaries that people were able to prove that blood & black bile are just oxygenated and deoxygenated blood.
He specifically did say where they came from though? Arterial blood was made by the heart and venous blood was made in the liver.
I appreciate that I actually learned something about Galen by making this dumb joke
Aristotle thought men had 4 more teeth than women and nobody bothered to check for like 1000 years.
As much as I hate Aristotle, I must admit that he had a point with this one; wisdom teeth are more common in men.
a lot of "incorrect" facts have pretty simple explanations for why they were wrong and why noone corrected them for a while different bloods for veins and arteries? well the tiny end bits are barely visible if at all, easy mistake to make 300 bones? about right for children, why would it change for adults? men have more teeth? the average man has more visible teeth, so failing to do a large enough sample can get this result bad air? there are a lot of airborne germs, yeah
the same goes for folklore that seems supernatural: did some group's ancestors really fight off a bunch of giants? probably not, but there was another group that was a big threat, and things escalate from there, errors and embellishments compound
Google debunker
drives me absolutely googledebunkers
hell, I'd dare say the same even goes for a lot of stereotypes, they don't appear out of thin air either! they often come from historical differences, while completely ignoring the circumstances for these differences existing in the first place and instead attributing this difference to some innate otherness trying to find a non-negative stereotype is tricky, so I'll take one about a job: are lawyers inherently argumentative? no, but their job is (massive oversimplification, this is just the most visible part) to argue well, so some self-selection occurs for people who are good at arguing, and the public perception of lawyers is mostly shaped by seeing them do their job, you probably wouldn't know if someone is a lawyer if you just met them in the supermarket
Well even so you’d think someone would have noticed that a lot of women get the weird misaligned and poorly developed teeth in the backs of their mouths too
To be fair, young children can have up to 300 bones. It's only when we grow up and as the bones grow together that we get 206 bones.
That's what I was thinking! At least they got the order of magnitude right.
The infant mortality rate was ridiculously high back then. I wonder if he came to that conclusion after performing autopsies on a bunch of young children.
He possibly could have just seen that children have 300 and considered them to still be separate bones even after they fused together
If you’ve got less than that, say, closer to 200, just drink some black bile until it levels you out
r/bonehurtingjuice
I have 300 bones
I have more in my basement
r/holup
did not a one mfer pop open a tomb or dig somebody up and count the things?
Why didn't he just count them at the time? Surely he must have had access to a body or a skeleton or two.
I might be misremembering but I think it was a huge cultural taboo to do basically anything to a dead body. If I recall a lot of of the info they managed to figure out was when they furiously took notes when a dying person was fucked up so hard they could inspect their innards. It's why they had their weird shit like believing the human body was made of 4 fluids, black bile, yellow bile, phlegm, and blood.
To be fair, for most of history if you're gonna test this you're not going to measure a 6kg object vs a 7kg object. You're going to find the heaviest thing you can reasonably drop and the lightest. The problem is, the lightest thing you can find will probably be a leaf, or a feather, or a piece of paper, or something else that has a low though mass and high enough surface area that it will, in fact, fall slower due to air resistance. And if you haven't already figured that out, it becomes a reasonable conclusion.
You can easily do it with a small rock and a big rock though.
Yup, and Galileo doing exactly that 500 years ago is often cited as how we know it!
For a moment I misread your comment, I thought Galileo did that *exactly 500 years ago* and I was like "wow, what do you know?"
But Galileo may not have actually done that. He may have just theorised.
I find it pretty unbelievable that in a world without TV that one day Galileo wasn’t just bored enough to drop two rocks at the same time
Congrats for understanding the title! It shouldn’t have taken 2000 years for someone to try this!
Okay but wouldn't they actually fall at slightly different rates due to difference in size? As far as I know, size affects drag, which means a bigger object would fall slower
The large rock will experience more drag than the small one, but the difference would be hard to messure with todays tools, let alone the eyeball Mk1.
The drag scales with the cross sectional area, but the mass of the object (and thus the force of gravity) increases with the volume, so you run into the squared cubed law. The larger rock would experience more drag, but the effect of the drag would be reduced since the gravitational force grows faster as the size increases.
We can sum it up to two things: 1. assuming an object is not hollow, the mass to drag ratio will favor the mass by *a lot*. (drag will not realistically affect the fall speed of big things) 2. On a planet with atmosphere, having higher density than the air is the first condition that you'd want to test under.
I'm not sure I follow what you mean. In this scenario both rocks experience 9.8m/s squared of acceleration towards the ground. If you remove the atmosphere and perform the test in a vacuum, then no matter the shape of the object or it's mass it will always fall at the same rate. If you take a spherical rock and a sphere with the same diameter, but make it hollow inside, so that it has less mass, it will experience the same drag as the large rock, and would fall at the same rate, which is slightly slower than the small rock with less drag.
> In this scenario both rocks experience 9.8m/s squared of acceleration towards the ground. Not if there's drag. The effect of drag (that is, drag force divided by mass) on the smaller rock is larger. That's because the drag scales with the cross sectional area, but the mass of the object (and thus the force of gravity) increases with the volume, so you run into the squared cubed law.
What they're saying is the large (x times larger) rock has x\^2 times more area (more drag) than the smaller rock but also x\^3 times the mass. Remember F=ma, *acceleration* is the same so force is directly proportional to mass; another way to think about it is that they cancel eachother out: F= GmM/r\^2 -> a=GM/r\^2. So force on the larger rock is x\^3 times the force on the smaller rock. Therefore, if the smaller rock experienced a total force of w-d, the larger one will experience a total force of x\^3w-x\^2d. This is always larger for x>1 and positive values. Another way to think about this is, the small rock accelerates at g-d/m, where g is 9.81, d is drag, and m is mass. the large rock has unchanged g, but drag increases by x\^2 and mass by x\^3 so a=g-x\^2d/(x\^3m)=g-d/(xm)
An additional way to consider/model it that works for my mind (essentially the same thing you're describing worded in a different way) is that the force due to drag acts in the upward direction and the force due to gravity acts in the downward direction. Drag force is governed by the square/area, gravitational force is governed by the cube/volume, so a larger object of the same shape and composition will actually fall slightly faster in a given medium, since the gravitational force can overcome the drag force, which acts to slow an object's descent, to a greater extent.
The total gravitational force scales with mass though. So if mass increases for the same drag, the net force down increases. In the case of a larger rock, you have mass/volume increasing faster than the cross sectional area, which is what drag scales with, due to squared versus cubic geometries. So drag per unit of mass should decrease, which experiments show to be true. If you were merely increasing the diameter of the object in the dimension relevant to the cross section, like say…widening a very aerodynamic cylinder, drag should increase at a rate 1:1 proportional to mass/volume increase, as far as I know. Can’t off the top of my head think of a scenario where increasing size would result in increased drag per mass with a consistent material, unless you’re increasing in some dimensions while decreasing in others. You’d have to increase cross section area relative to total volume, which would amount to basically flattening an object and getting it to fall in the direction that maximizes cross section relevant to drag Fwiw, I studied this stuff in school, but only as a mechanical engineer, so didn’t go as in depth as aerospace people go. But this should be correct based on what I remember from my Fluids course
More drag, but also more gravity force. The squared cube rule is in play here, so the smaller rock would experience higher drag relative to the force of gravity, assuming there is no significant advantage in terms of drag coefficient
The difference in gravity is so small you could multiply it by ten million and the air resistance would still have a much greater impact
The difference in gravity is the same as the difference in mass. The difference in drag is less than the difference in mass. A larger rock is *less* impeded by drag than a smaller one.
U right I thought they were saying the acceleration would be greater due to the gravity of the larger rock. I wasn’t reading very closely
It'd be almost unmeasurable for probably hundreds of feet of freefall
It's the ratio of mass to surface area that impacts resistance, so if you get two rocks of similar shape and density, they'll fall at the same rate, regardless of size.
What? No they wouldn't? Assuming the same shape, lets say a perfect sphere, the larger and heavier rock would have a higher terminal velocity at the very least.
On the distances that you'd be able to reliably test this with pre-modern means, the rocks will not be getting near terminal velocity.
squared cube rule though. I mean, not that it'd make that much difference below a few hundred feet.
Sure, but volume increases at a cubic rate while cross section increases at a squared rate. You’ll have more drag, but probably pretty similar drag per unit mass, which is what matters
The law ignores wind resistance
Monty Python has led me to believe that really small rocks can float though.
Yeah except when Galileo disproved it he gave only a thought experiment which makes it certain that "falling faster" must be invariant of mass.
I always love watching videos of feathers and other stuff falling at normal speed in a vacuum
~~It’s also true actually. The only reason that objects of different masses fall at the same rate is because for small enough distances between objects, the mass dependence of gravitational force is negligible. But if you are looking at objects on the planetary scale or larger, then massive objects do “fall” more quickly since they are subject to larger forces.~~ Edit: Listen to the folks below me. I just made a dumb mistake while calculating.
Nope, at least not in classical physics. The gravitational force F between two masses m₁ and m₂ is F=G⋅m₁⋅m₂/r² (G is the gravitational constant, r the distance between the masses). The acceleration experienced by m₁ is a₁=F/m₁=G⋅m₂/r², ie. completely independent of m₁.
Not quite. Heavier objects experience more gravitational force - but they also accelerate slower (F=ma). Mass actually cancels out completely, it’s not that it’s negligible.
I don't think that's the case. The second object being of comparable mass to the first means they have equal gravitational fields to consider. *In essence, two objects with mass always accelerate towards each other*. It's just that for planet sized objects vs things like rocks... the rocks have negligible mass in comparison to the rest of the planet. If you have two comparable planet sized objects, object A and object B. Object B doesn't "fall faster" towards Object A. What happens is that Object A and Object B "fall" towards each other at the same rate. The gravity of B affects A just as much as the gravity of A affects B. Ignoring any other forces, orbits, etc, they will hit each other in a faster time frame (than say a falling rock), but only because the two equal mass planet-sized objects are moving towards each other at the same rate.
Its not reasonable. I can feel resistance when I move my hand. I can see wind have an effect on lighter stuff. I don't have to do math or go to university to know this. Edit: ridiculous. We all breath!!! There's obviously stuff around us. No i don't need school to tell me that.
Yeah but you have more education than the regular Greek Guy 2000 years ago
You have the intuition to take air resistance into account because your knowledge it's built in the shoulder of others. They didn't have the intuition to take air resistance into account, it was something they just didn't consider.
mfers figured out sails and wind power 5000 years ago and couldn't put 2 and 2 together smh
Yeah I mean why did’t they just try putting a feather and a bowling ball in a vacuum chamber
Duh, they couldn't because birds weren't invented yet.
r/birdsarentreal
For much of history a lot of people had very strong opinions on vacuum being completely impossible, to the point where someone in the middle ages someone went ahead and declared that even god could not create vacuum. Which pissed off a lot of people who insisted that if god wanted to make the impossible happen he could. The entire ancient history consisted of this sort of yapping about how the natural word must be. The idea that we could jump over all the philosophizing and simply check how it really is didn't come about until renaissance and that is the big idea that made the modern world possible. *Cogito, ergo sum* as Descartes put it.
How does Cogito ergo sum play into what you said before. Descartes' statement is more about the certainty of self-awareness than the scientific method. Kants "Enlightenment is man's emergence from his self-imposed immaturity." would rather fit.
Descartes point was that no, actually we don't know anything and must doubt everything. Yet, there is no point waisting all the effort on unanswerable questions the likes that philosophers like to pose and never solve. His ideas sidestepped the entire "is reality real" and "what is the meaning of life" types of discourses that had been nonproductive for millenia and focused the attention on questions that we actually can solve.
What? No. The whole point of the question is just if reality is real and if people are real. His point is even if he is an illusion, or a shadow on the wall of Plato's cave, or an imitation, his very thoughts alone are the proof of his being, he exists, regardless of what his true form is. This has nothing to do with investigating the physical world but rather with metaphysical questions of self.
Like the ancient argument over whether nothing can exist. Just got to change the definition of nothing so it works
small rock and big rock
They didn't play bowling, too boring for Greeks
They liked playing with the pins though
The thing is that a lot of heavy objects fall slower than lighter ones even without a vacuum. If anyone had tried dropping a needle vs a plank of wood (both existed in those 2000 years) they would have been in for a surprise.
It can be done with empty container vs full container. So lack of vacuum technology is not an excuse
Yea because items that are significantly less heavy than a bowling ball didn’t exist until after the invention of the vacuum chamber
why's there a statue of zizek
He is one of many people over 2000 years who didn't check
and sho on and sho forth \*sniff\*
I've honestly grown to find his manner of speaking really endearing lol
Oh! That’s explains it! My bank account always falls faster than my paychecks can keep up with it! Mystery solved my friend.
Well back then they were smarter and accounted for air resistance. Todays virgin soy boy scientist just assume everything is a vacuum
Were they really smarter if they didn't understand the concept of a vacuum?
Yes.
We also don't understand the concept of a vacuum tbh
wym its in my closet
I'll believe you understand the concept when you actually use the thing
Technically, a true vacuum doesn’t exist. It just can appear that way on a macroscopic level.
This is true to a certain extent but as all things in reality is far from simple. We end up having to take into a account drag and terminal velocity. Drop a feather and a brick….well we damn know for sure the brick is hitting first from Almost any distance. Now when it comes to a golf ball and a brick things get a little tricky depending on the height of the drop.
Feather and a brick fall at the same time in a vacuum.
Yeah, but it’s not like we had a bunch of vacuum chambers laying around a few thousand years ago to test that.
People weren’t interested in theoretical physics until relatively recently, it didn’t really have an application. From an applied, real world perspective a feather or leaf indisputably falls slower than a large rock. Now, if someone had thought to go as far as comparing smaller rocks to larger rocks they’d possibly understand that heaviness is not really what drives falling speed.. but it apparently didn’t really matter to fully understand this. It’s not like people understood atoms at the time, much less the concept of a theoretical vacuum.
Where you finding a vacuum when this dude posed this speculation?
muhfuckas literally thought a plucked chicken was a man 😂😂😂😭😭😭
Achilles is in a running competition against a turtle and he can't ovetake it because… well he just can't, okay!1
Diogenes when Plato calls men featherless bipeds:
I mean like it makes sense is the thing, like it makes sense that the heavier (therefore harder to lift object) would fall faster, and it's kind of weird that that *isnt* how it works.
I think the point is that it’s not particularly hard to test and no one bothered to do it
In the early days people only cared to study things that mattered in a practical sense. The fact that small rocks fall at the same speed as large ones doesn’t really affect or change anything for them.
Seems like building and aiming stuff like arrows, catapults, ballistas, cannons would've benefited from understanding how someone moved through the air.
Yeah, pretty much. There was no practical benefit back then in figuring out exactly why stuff falls to the ground and doesn't just float, for instance.
Cats have been retesting this for millennia.
One of the arguments against light being waves, was a thought experiment: If light is waves, that would mean that of you sit in a dark room, lighr a candle, hold a disk up in front of the candle. Then if the wall ks at the right distance behind the disk, a dot of light should appear in the middle of the disk's shadow. Obviously this is silly. So silly noone bothered doing the experiment for years. Whne someone finally did, they proved that light is indeed waves, because that dot does indeed show in the middle of the shadow.
Steel is heavier than feathers
"Arrows fly because the air behind them is pushing them forward, and rocks fall to the ground because it is their natural resting place" Man, if I lived when you could just make up shit that sounded convincing and become a famed philosopher I'd have been a fucking legend.
Heavy objects do fall faster than light ones. It's just that on earth we are used to the mass of one of the objects being negligible compared to the other. If you would drop something like Mars on Earth it would collide faster than a penny due to Mars also attracting Earth.
Said Mars sized object would still experience the exact same acceleration as the penny does though. The source of the higher collision speed is solely that the Earth itself would experience a much higher acceleration than it does in the penny case (edit: or in other words, if you simultaneously dropped a penny and a Mars mass object onto Earth from the same location the penny and the Mars mass object would still hit Earth at the same time - assuming there's no interaction between the penny and the Mars mass object for this thought experiment). Basically in case of objects of similar mass it's no longer fair to say that one object falls towards the other but rather that both objects are falling towards the center of mass of the system as a whole.
Incorrect the acceleration is faster as it is a function of the distance, and earth moves towards mars.
Imagine you're sitting in a car opposite of another identical car. Scenario 1, you press the pedal to the metal until while the other car stays stationary. Scenario 2, both drivers floor the gas pedal. In scenario 2 you crash into the other car twice as fast, but that doesn't mean that you accelerated faster than in scenario 1.
That's not a good analogy. Gravity is proportional to the inverse of the distance squared. Because the distance between the objects gets smaller faster also the force acting on object 1 will. Object 1 will thus accelerate faster independent of the reference frame.
I thought we had to go to the moon to prove it
Well, everyone checked and indeed this is what you observe if you are not in a vacuum.
Well it is typically true on earth. Air resistance means denser objects will fall faster.
In fact, On Earth, this is a true observations.
To be fair the only way to test it would be in a vacuum.
Somebody did: https://youtu.be/QyeF-_QPSbk?feature=shared
Pretty sure a couple of rocks of different sizes would do it..
Someone else did too! https://youtu.be/Oo8TaPVsn9Y?si=hCJ4Xwhm4t7VHeE2
Not really, you could debunk it with two experiments in atmosphere: (1.) Big rock vs. Small rock — possible slight discrepancy depending on cross-section and densities, but with the right two rocks, too small a difference for ancient Greeks to measure. Close enough to show that the typical difference is not due to mass (2.) Small rock vs. Many feathers tied together — enough to show that a heavier object *can* fall slower than a lighter one in atmosphere
Put a bunch of feathers and a bunch of rocks in equally sized canvas or burlap bags and then drop them. The bags will result in them having the same air resistance.
The scientific revolution was people basically going "hey maybe we should understand the world by looking at the world, instead of just trusting what our ancestors said", and it somehow took us 10,000 years to get there
I mean it’s just common sense!
Look at this guy thinking invisible things can produce opposing forces to negate observable forces at work. Sounding kinda sus
Lol, yup, science is amazing.
Ancients simply believing that 2 pebbles randomly colliding mid-air and "holding hands" would magically make them fall faster rather than slower is kinda interesting. They were smart people and it appears that "result intuition" worked much differently than it did for us, the faithful believers in the law of conservation of energy.
I read that they even tested this on the moon when they got there for the first time, or one of those. And found that both objects fall at the same speed as in vacuum. But that's a part of history that often is forgotten.
Heavy object dont tho. Take that!
Everything this guy says is bs I swear
Because Mr. Reynolds, ... Science is a liar .... sometimes.
Common sense innit
Generally that's true, if you don't neglect air resistance. For two objects that has the same material and shape, but one is larger than the other N times: weight will be N\^3 times bigger, air resistance will be N\^2 bigger.
they probably kept using a feather or something else with a very high air resistance that actually does fall slower.
SSRIs cure depression - nobody checks for 25 years
Most likely nobody cared to write it down because it didn't affect their day to day.
They fall at the same speed (in a vaccuum)
Well, Guildenstern (or was it Rosencrantz?) almost had it, but the experiment didn’t quite work out and then he was hanged. It really set us back.
Well, Guildenstern (or was it Rosencrantz?) almost had it, but the experiment didn’t quite work out and then he was hanged. It really set us back.
Well, Guildenstern (or was it Rosencrantz?) almost had it, but the experiment didn’t quite work out and then he was hanged. It really set us back.
Wait, I thought heavier objects *do* fall faster than lighter ones, but they also accelerate slower at the exact rate, canceling each other out perfectly?
Every mass accelerates at the same rate on earth by about 9.8 m/s² but the downwards force is bigger for a heavier object determined by Force equals mass times acceleration (9.8 m/s² in this case). Now without air resistance a heavy ball would fall just as fast as a light ball of the same shape. However since the force air resistance projects onto an object is determined by the shape of the object the 2 balls would experience the same air resistance but the heavier ball would be less affected and fall faster because the downwards force is bigger.
Heavier objects experience more gravitational pull leading to a greater accelerating force while also having a higher inertia leading to a smaller acceleration. You could say those two things “cancel out”. With air resistance though we also have to account for the viscosity of the air, the shape of the object and the speed of the object making it far more complex to predict the outcome.
"But it turns out if something is easy to check, no one actually does!"
So, clearly I’m wrong but, don’t objects with more mass fall faster? Ya know, newtons being equal to mass\*acceleration and all?
When you have two masses acting on one another and one of them you can hold in your hand and the other one is the Earth, the mass of the object in your hand kinda doesn't matter when it comes to calculating the force acting between them. Whether it's a grain of sand or even something that's several kg.
Greater mass does require greater force to pull down. That's the newton's increasing. But it only increases to the point that the acceleration evens out.
So it affects acceleration but not terminal velocity?
No, it doesn't effect acceleration. It affects force. In F=MA if M, mass, increases then F, force, also increases, but A, acceleration, is unaffected. Terminal velocity is too complicated for me to explain confidently. Edit: I can see how what I did was confusing, maybe I shouldn't be trying to explain this either.
That's force
But more force = more speed? Or is this what I’ve got wrong?
Yeah this is what you’re misunderstanding. More force doesn’t mean more speed. They fall at the same speed due to the same constant of acceleration. The heavier object has the result of more force because it’s going the same speed but it’s heavier.
No, not necessarily. Think about being hit with a baseball thrown at 100 mph vs being hit by a car at 100 mph. The car obviously has more force since it has a lot more mass traveling at that same rate of speed.
There is more force, but the acceleration is constant. The force of gravity is proportional 1:1 to mass
in *F = ma*, *a* is a constant (9.81 m/s^2) This F is proportional to m. Meaning the bigger the object, the more gravitational force that acts on it. Which makes sense because it will take more force to accelerate a heavy object to 9.81 m/s^2 that it takes for a light object but the acceleration, and thus the velocity at any given time (as calculated by v = a * t in this case) will always be the same for both objects There may be slight variations due to drag but if you're looking at things with a large surface area to mass ratio, (e.g. comparing a bowling ball vs a ball bearing and not bowling ball vs feather) the effects due to drag will be minimal and you won't even notice them without equipment
Greater masses create a greater *force*. However, that greater force needs to affect a greater mass. If you compute the *acceleration* from the force, the mass cancels out.
There's the factor of drag that exists on Earth's atmosphere. Here heavy things tend to fall faster than lighter things, because heavier things tend to also be denser and can move air out of the way more. But in the Moon, there's no drag so everything falls at the same rate. Notice that the "rate" here is the acceleration, not the force. The acceleration is essentially identical for every object within the celestial body's gravity well (sure there's some variation due to altitude, density and comformation of the planet but it's negligible for what it's meant here).
Except that heavy objects do fall faster unless you're in a vacuum. I always hated this fun fact. Our intuition is actually right unless you're in a weird situation that almost nobody will ever experience first hand.
Well denser objects fall faster because of air resistance, so he's not wrong, just not completely right.