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Does Antimatter Fall Up?
New submitter Doug Otto sends word that researchers working on the ALPHA experiment at CERN are trying to figure out whether antimatter interacts with gravity in the same way that normal matter does. The ALPHA experiment wasn't designed to test for this, but they realized part of it — an antihydrogen trap — is suitable to collect some data. Their preliminary results: uncertain, but they can't rule it out. From the article:
"Antihydrogen provides a particularly useful means of testing gravitational effects on antimatter, as it's electrically neutral. Gravity is by far the weakest force in nature, so it's very easy for its effects to be swamped by other interactions. Even with neutral particles or atoms, the antimatter must be moving slowly enough to perform measurements. And slow rates of motion increase the likelihood of encountering matter particles, leading to mutual annihilation and an end to the experiment. However, it's a challenge to maintain any antihydrogen long enough to perform meaningful experiments on it, regardless of its speed. ... The authors of the current study realized that [antiatoms trapped in ALPHA] eventually escaped or were released from this magnetic trap. At that point, they were momentarily in free-fall, experiencing no force other than gravity. The detectors on the outside of ALPHA could then determine if the antihydrogen was rising or falling under gravity's influence, and whether the magnitude of the force was equivalent to the effect on matter."
Maybe our universe is a 'matter bubble' in a 'sea of anti-matter'. WE are the anti-matter.
To us, our normal matter is so common but that's only because we're sitting right smack in the middle of it. That would explain the repelling forces and show why dark matter could exist outside the bounds of the observable universe.
Whoops!
Have gnu, will travel.
If they have created hydrogen atoms already, why wouldn't they just check to see if those atoms fall to the bottom of the container, or float to the top? I would guess these atoms are stored in a vacuum, so buoyancy isn't a concern.
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Obviously there must be some credence to this idea for such an experiment to take place, but since my understanding is that gravity is an inherent effect of mass warping space, wouldn't anti-matter possess mass in the same way that matter does, so why would gravity act differently?
Just asking. Not trying to claim anything.
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And now we have proof of that. Most science isn't groundbreaking, but that doesn't make this experiment less important.
So now all we need to do is create a container of anti hydrogen and surround it with an electrical barrier to have our floating cars =)
It's easy to assume answers, but measurements separate science from philosophy.
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Does it live under water?
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And now we have proof of that. Most science isn't groundbreaking, but that doesn't make this experiment less important.
They don't quite have proof yet, but hat's okay, the goal of this experiment is to measure the ionization levels of anti-hydrogen. The anti-gravity test is a side show.
If antimatter interacts with gravity in such a way that it "falls" up or pushes against the force like magnetic fields pushing against each other, does this mean that antimatter would make anti-gravity platforms possible?
I'm a science plebe who watches/reads too much sci-fi, this was the first thing that came to my mind.
Then all we just need a ton of it to cancel out the weight of, lets say a car.
It will be like the Blade Runner movie with cars, floating around in the sky, whizzing past each other.
But not too close. Because that would set of one gigantic chain reaction of sympathetic mass annihilations, blowing earth out of its orbit around the sun.
1. Yes, hydrogen would fall towards the earth in a vacuum... sort of. Hydrogen atoms have a very high kinetic energy at room temperature, to the extent that the more energetic ones achieve escape velocity at a noticeable rate. So if you released a bunch of hydrogen around an Earth-sized planet with no atmosphere, it would be attracted to the planet, forming a tenuous atmosphere, but in time it would dissipate. If you try this experiment around Jupiter, the hydrogen will stick around basically indefinitely. In fact, nature has already tried the experiment -- Jupiter has a lot of hydrogen in its atmosphere.
So basically, hydrogen is affected by gravity in the same way as any other gas is.
2. According to standard physics, anti-hydrogen should behave exactly like regular hydrogen. That is, it should be attracted to the earth. If you have a gigantic container of anti-nitrogen at atmospheric pressure and put in an anti-balloon of anti-hydrogen at atmospheric pressure, the balloon would go up, just like a regular balloon in the regular atmosphere.
If the alternative hypothesis is right, and Earth's gravity repels antimatter, then the anti-hydrogen balloon would go down instead, but this is very unlikely to be the case.
In any case, the experiment will be performed in a vacuum, where hydrogen would behave just like any other material (and probably, so will anti-hydrogen).
3. Which theory?
Negative matter DOES react to tractor beams in reverse, being repelled by the nominally attractive force.
Welcome to the Panopticon. Used to be a prison, now it's your home.
3 questions.
1. Hydrogen rises in gravity because it is less dense than air(mostly Nitrogen), So if there was no air/vacuum then hydrogen would fall towards the earth.?
I can't say anything to the other two questions, but this question is easily answered by something my high school physics teacher said to me. It has stayed with me since then as it is as eye-opening as it is obvious (in hindsight):
"The first mistake is to assume that helium rises. The truth is that it falls down towards the earth just like any other object. The reason for what you see is much simpler: It does not rise; it's just that everything else simply falls harder." (Freely translated from memory and German)
Helium only rises over the air, because regular air has the stronger draw to be below it. This explains why, in the absence of gravity; there is no lift. In the absence of a pull, the air has no impulse to displace the helium.
More generally, the same is true for liquid mixtures like oil/water. In gravity, the oil will rise above the water. In (close-to-)zero gravity, the oil and water will separate but stay where they are. That is because the water can't displace the oil without gravity pulling it more strongly down.
The same is true for solids. In meteorites with too little gravity, no submersion of the "heavier" elements like iron happen. This is why Earth has an iron core, but iron-rich asteroids have it distributed all over their volume.
I'd love it if we found out that antimatter falls upwards, but I'd be even more interested if anyone could conjecture on what that would mean.
Could that mean that antimatter warps space in the opposite direction as matter so that it has a repelling affect?
// file: mice.h
#include "frickin_lasers.h"
Assuming floating up meant it to have negative mass, antimatter would have negative energy and therefore matter and antimatter with congruent weight would annihilate without any visible energy-output.
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No, it almost certainly doesn't. There's no theoretical indication, even non Einsteinian gravity theories, that indicates it would. But heck, we've never tested it, and we can test it, so why not? Maybe it does and everyone was all wrong and we'll have to think of all new stuff. It almost certainly won't happen, but almost certainly isn't a good enough reason not to try.
As I wrote in a comment to the submission: Photons fall down. Is there such thing as an "anti-photon"?
I see no reason to even think they would. Gravitation is dependent upon mass of and distance between objects. Particles have the same mass as their anti-particle equivalents.
This research sounds like a massive waste of money.
Some background on antimatter antigravity from the Tikalon blog.
I disagree with that. For instance, game theory as applied to the study of effective ethics, is well within the realm of philosophy AND science. Never forget, as many mathematicians do, that all logic including the logical system known as mathematics are all parts of just one branch of philosophy.
The Usenet Physics FAQ has some background information on the theory behind this question. It's 14 years old but still worth reading. One interesting bit:
Based on what we currently know, we would expect that the only significant force acting on a piece of falling antimatter is gravity; by the equivalence principle, this should make antimatter fall with the same acceleration as ordinary matter. However, some theories predict new, as yet unseen forces: these forces would make antimatter fall differently than matter. But in these theories, antimatter always falls slightly faster than matter; antimatter never falls up. This is because the only force that would treat matter and antimatter differently would be a vector force (mediated by the hypothetical gravivector boson). Vector forces (like electromagnetism) repel likes and attract opposites, so a gravivector force would pull antimatter down toward the matter-dominated Earth, while giving matter a slight upward push.
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The question of whether anti-matter experiences anti-gravity goes back as far as I can personally remember (1970's) and probably some decades before that.
For most of the past 300 years in physics, experiment has led theory. We measure something, it leads to a theory, and then experiments are done to check the theory. Examples abound of theories that explain previous observations, and also predict something new - probably the most famous is relativity predicting the precession of Mars, but there are lots of others. (Newton predicting elliptical orbits based on the inverse square law of gravity comes to mind.)
Since about 1970 the situation is reversed - theory has led experiment. We have a satchel of theories which attempt to explain questions in physics which have no discriminatory evidence. Theories such as "Super Symmetry", "Loop Quantum Gravity", and "String Theory". I'm reading a book right now which claims 10^500 different string theories (yes, that's 10 with 500 zeroes after it), and lamenting the fact that few of these actually make testable predictions.
Relativity predicts that anti-matter should have positive gravity, but this has never been tested.
Until recently, the only antimatter we had access to has been charged particles: anti-protons and anti-electrons. Measuring the gravitational force on a charged particle is nigh impossible because the EM force is so large (relative to the gravitational force) that any EM effects swamp the readings. You can't just see if the particle falls in the container, because it's essentially impossible to shield a container well enough. It's like trying to measure the mass of a cork floating in a tornado.
Anti-hydrogen would work, but until recently we had none to test. Antiparticles tend to have high velocities when produced - they have to escape their anti-nemesis which is also produced - so they have to be slowed down enough to "pair" to make the neutral antimatter particle.
The vacuum used for the experiments has a big effect also. Depending on the level of vacuum used, any particle has a "mean free path" before it will impinge on another particle. You have to get your anti-particles to slow down, form antimatter, and conduct the experiment before another particle comes in and annihilates it. This requires insanely good vacuum which is both hard to achieve and highly expensive.
The ALPHA experiment at CERN now produces antimatter, so the referenced paper asks the question: what is the ratio "F" between the inertial mass and the gravitational mass of antihydrogen? For normal matter it's 1 and for "antigravity matter" it would be -1.
The paper reports that they have measurements within specific confidence levels that F < 110 almost certainly, and F < 75 at the 95% confidence level.
If the experiments outlined in the paper are continued (and perhaps refined), over time they can statistically narrow the results and ultimately settle the question by experiment.
I think that this would be a good thing, it would confirm (or contradict) by experiment something that is predicted by theory.
1) Not exactly.. In the absense of other forces all known objects/particles will accelerate towards each other due to gravity. Hydrogen rises for the same reason a boat floats in water - buoyancy. Denser things (like water or air) fall "harder" and push less-dense things (like boats or hydrogen) out of the way. When you release a piece of wood underwater it doesn't fall up, it gets lifted up by the denser surrounding water which experiences a larger gravitational force per unit volume. It's basically an energy game - gravitational potential energy in a constant field equals mass*gravitational acceleration*height. Imagine a chunk of wood and an equal-volume "chunk" of water next to it. At the same height the water will have more energy than the wood because it has more mass. If the wood is pushed downward the water will be pushed upwards since there's a finite volume to be occupied at that depth. As a result the wood will have lost some gravitational potential energy, and the water will have gained some; however, since the water is more massive it will have actually have gained more energy than the wood has lost. The effect is similar to pushing a ball up a hill - you've created a gravitational energy "battery" which will discharge itself as soon as you remove the forces holding things in position.
2. No. The effect of gravity will be the same regardless of surrounding particles. If anti-H has positive gravitational mass it will fall down unless displaced by something more massive. It's best to do such experiments in vacuum simply because it eliminates the "noise" of interparticle interactions.
--- Most topics have many sides worth arguing, allow me to take one opposite you.
If antimatter is gravitationally repulsed by matter, then it could help explain dark matter. Instead of requiring a huge expansion of the Standard Model, it may simply be that the vacuum is gravitationally polarized.
http://arxiv.org/pdf/1106.0847.pdf
(I'm a big fan of Hajdukovic. Whether he's right or wrong, he asks fascination questions).
For instance, game theory as applied to the study of effective ethics, is well within the realm of philosophy AND science.
No, it's in the realm of philosophy (with a few nods towards mathematical rigor to provide a facade of credibility beyond standard armchair philosophical wanking).
3 questions.
1. Hydrogen rises in gravity because it is less dense than air(mostly Nitrogen), So if there was no air/vacuum then hydrogen would fall towards the earth.?
I can't say anything to the other two questions, but this question is easily answered by something my high school physics teacher said to me. It has stayed with me since then as it is as eye-opening as it is obvious (in hindsight):
"The first mistake is to assume that helium rises. The truth is that it falls down towards the earth just like any other object. The reason for what you see is much simpler: It does not rise; it's just that everything else simply falls harder." (Freely translated from memory and German)
Helium only rises over the air, because regular air has the stronger draw to be below it. This explains why, in the absence of gravity; there is no lift. In the absence of a pull, the air has no impulse to displace the helium.
More generally, the same is true for liquid mixtures like oil/water. In gravity, the oil will rise above the water. In (close-to-)zero gravity, the oil and water will separate but stay where they are. That is because the water can't displace the oil without gravity pulling it more strongly down.
The same is true for solids. In meteorites with too little gravity, no submersion of the "heavier" elements like iron happen. This is why Earth has an iron core, but iron-rich asteroids have it distributed all over their volume.
That is true for a container (e.g. a balloon*) filled with helium. AFAIK it would also be true for individual helium atoms if the temperature was 0 Kelvin. They would basically fall like little rocks.
In reality the Earth is actually warm enough and light enough that unconfined helium atoms frequently reach escape velocity and fly away into space. They do this often enough that a cloud of helium will never settle on top of the atmosphere like oil on top of water. It will just diffuse into space. There is no particular reason why a helium atom would want to travel upwards, except in the big scheme of every direction is basically upwards so once an atom has moved a good distance it will have moved up and away from Earth.
All of this hold for hydrogen molecules too, except my understanding is that hydrogen will usually react with oxygen in the atmosphere and form water on the way up, and water molecules are too heavy to escape the Earth at a noticeable rate.
*Assuming it's an indestructible balloon that doesn't pop at altitude, of course.
Imagine you have a sealed super insulated magic box filled with energy that can be partially converted upon command to (anti)matter via pair production and later back to energy again.
The box is suspended over a cliff on a white dwarf by spring and left to free fall. The spring harvests some energy from the falling box and some is lost to friction and other resistance.
At the bottom of the cliff box produces matter anti-matter pairs reducing its effective gravitational mass. This allows spring to overcome gravitational force holding the box down and reposition itself at the top of the cliff where pairs are converted back into energy and the process begins all over again. You then run to the patent office and secure your patent for the worlds first working propetual motion generator. Not bloodly likely if you ask me.
Mental typo: typed "Mars" when I meant to say "Mercury". Relativity predicted the precession of Mercury.
Ultracold so it doesnt hit the container quickly. Made at CERN too.
If anti-matter falls up (repels matter) and even repels other anti-matter, it would explain the Fermi Paradox. You could not travel between starts because there would be fairly-evenly-distributed particles of anti-matter everywhere between stars, avoiding the stars due to their gravity, and spacing themselves (the anti-matter particles) out because they repel each other.
This is scary.
The Onion is going out of business because their wacky stories keep coming true:
http://www.theonion.com/articles/evangelical-scientists-refute-gravity-with-new-int,1778/
Table-ized A.I.
Game theory is mathematics, not science.
eom
Mathematics is science, not whatever you think it is.
I have been thinking this for twenty years.
Think of E=MC2.
Faster than light travel is only impossible when you have a net positive mass. If your mass is net zero, (meaning in your magnetic grip you hold matter and antimatter in the same functional unit but not touching each other (two magnetic bottles), then you could travel faster than the speed of light.
“Physics is to math what sex is to masturbation.”
-- Richard Feynman
... not that I don't think masturbation (and math, possibly at the same time) is nifty. Science is distinguished from mathematics in that it not only considers mathematical models, but compares (and judges) said models by correspondence to "real world" observations. Game theory, while "physically motivated," is mathematics. Game theory can be applied by scientists to explain real-world measurements, but on its own is not science.
If it utilises the scientific method, it's science.
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By which standard mathematics manifestly is not science. While there is no "one true formulation" of what the "scientific method" exactly is, pretty much every formulation roughly follows the schema described here on Wikipedia, including the critical element of:
Testing: This is an investigation of whether the real world behaves as predicted by the hypothesis.
A mathematician --- let's consider a game theorist for example --- will set up a problem ("given this rigorously-defined hypothetical scenario, what strategy would result in maximization of mathematical object 'X'?"), and apply mathematical logic to produce a provably correct answer to the hypothetical question. Whether this scenario *actually exists* anywhere in reality, and whether participants *actually act* according to optimal strategies to maximize 'X', is wholly irrelevant to whether the mathematician's theory is "correct". A scientist using game theory would ask such questions (and perform real-world tests to conclude the answers) --- and might even conclude that the theory (applied to a real-world context) is scientifically false (fails to model the real world), even though the mathematical theory is provably true.
No, mathematics is a kind of philosophy. It happens to have some real-world applications, but then so do some other branches of philosophy.
-- Alastair
If it utilises the scientific method, it's science.
Exactly. Like evolutionary biology. Now that we've successfully created life from basic proteins and selectively applied evolutionary pressure until we get modern man hundreds of time, we have a solid scientific theory. And cosmology. Now that we have successfully created the universe hundreds of times and consistently observed its behavior, we have a high-confidence model for what it will do in the future.
And a good thing, too. Can you imagine where we would be if those types of things were inherently not subject to repeatable, falsifiable experiments? What a wreck that would be! Much of our body of science would be inductive reasoning that we kind of back into from our best observations, instead of nice, tidy falsifiable experiments from which we can deductively predict outcomes, just like they taught you in sixth grade. I'd sure hate to live in that kind of world.
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I would expect antimatter to be gravity neutral to matter and to show anti gravity only to antimatter (which would probably not be practical to measure on earth.)
This would give a simple explanation to some big problems; like why our universe has no antimatter in it. In other words an anti matter world would disperse.
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If and only if F=-1 (anti-matter and matter repel each other gravitationally), the following questions have already satisfactory answers, at least for me:
* Why is our universe composed of matter only?
It isn't. There are both normal matter [NM] and anti-matter [AM]. But since they repel each other and attract their own kinds, they gang into NM-only and AM-only "clusters".
* What's a galaxy? Why are they formed?"
Each galaxy is one of those clusters. They're formed in "separated blobs" instead of a single huge one due to the repulsion.
* "Why is the universe's expansion accelerating?"
AM-NM repulsion.
* "Where is the anti-matter?"
We probably already saw, named and cataloged anti-matter galaxies, since they interact with the light (what we have coming from them) in the same way as normal matter. (...mmmm. What if we checked for possible intergalactic repulsion? This would corroborate with the "F=-1" hypothesis, although a negative wouldn't rule out the hypothesis, i.e. it's not falsifiable.)
* "Are there anti-matter intelligent beings in the space, ready to throw mankind into slavery for their ugly purposes?"
Only if they want us to do information-related jobs, since they would be annihilated by any goods we do.
I, for one, welcome our new anti-matter overlords.
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Note that this is why we cannot use blimps to get to the ISS: hydrogen is subject to gravity.
An article several years ago posited that "dark energy" was due to the gravitational repulsion between matter and anti-matter. This was discounted at the time, but I always thought whether it should have been dismissed without experimental evidence. I am really happy to read that the very difficult experiment is being attempted.
Mathematics is different from philosophy. Philosophers try to say something about the real world, albeit with different methods than natural sciences. Mathematicians on the other hand don't try to say anything about the real world. They analyse the structure of mathematical/logical constructs, no matter where those constructs come from (most early constructs came from natural sciences, but there are now also many constructs which cannot be found in nature; try to find the smallest uncountable ordinal number in our world!).
The Tao of math: The numbers you can count are not the real numbers.
If there was a point in that sarcasm, it was lost on me.
According to Lucy van Pelt, snow comes up from the ground.
Just a minor correction...
The instrument was eventually changed to a non-superconducting version. This was discussed here on Slashdot, but here's a section of the Wikipedia page on the experiment that states it briefly:
"With Obama administration plans to extend International Space Station operations beyond 2015, the decision has been made by AMS management to exchange the original AMS-02 superconducting magnet for the non-superconducting magnet previously flown on AMS-01. Although the non-superconducting magnet has a weaker field strength, its on-orbit operational time at ISS is expected to be 10 to 18 years versus only three years for the superconducting version. This additional data gathering time has been deemed more important than higher experiment sensitivity"
I've eaten that! It is called a baseball sirloin.
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My mother is a halfling and my dad is an ogre, so that makes me an Ogreling
I find the analogy between matter/anti-matter and electron/hole pairs in semiconductors to be pretty fascinating. It's only pseudo-science, but I did some checking of Maxwell's equations and equations from Special Relativity, using this analogy, to see if anti-matter falling up makes any sense. If you assume mass can be negative, like the mass of a hole in a silicon lattice, then there are only a couple of places where I had to use the absolute value of mass to make it all consistent (one was E=MC^2). However, there are alternative ways to represent anti-matter falling up which may more consistent, where antimatter has positive mass. "Does antimatter have negative mass?" is not the same question as "Does antimatter fall up?" Here's what I put on the talk page on Wikipedia about this topic:
General relativity predicts anti-matter falls down, and it probably does. However, I find the close analogy between electron/hole pairs and electron/positron pairs fascinating. Holes fall up, because the electrons above fall down. When electron/hole pairs meet, they annihilate each other, often giving off a photon, just like electron/positrons. Electron/holes are created in pairs, never just on their own, just like matter/anti-matter.
It's a weak analogy, but if gravity is caused by warping of space, can we compare that to how electrons and holes warp a crystal lattice? Electrons cause a crystal lattice to expand to make room for them, and this expansion causes other electrons to be weakly attracted to them. At very low temperatures this results in Cooper pairs, which likely explains super-conductivity. Holes in a silicon lattice similarly attract each other, because they cause the local lattice to contract. There are papers on the web that mention the possibility of Cooper pairs made of holes. Electrons are repelled by the lattice contraction caused by holes, just as holes are repelled by the lattice expansion caused by electrons. Could matter/anti-matter be similar?
Celebrate failure, and then learn from it - Nolan Bushnell
Philosophers try to say something about the real world, albeit with different methods than natural sciences.
Sometimes, maybe, but most philosophy is just like math: you're reasoning in the abstract about logical constructs. The constructs might model things in the real world, but it's the abstraction that gets debated. Take epistemology, for example (the meaning of "know") - you contrive all sorts of oddball examples to get intuitions about it, but there's never the sort of argument that could be settled by instantiating those examples in the real world and measuring them. Without first defining "knowledge", there's no measurement that can tell you whether someone has knowledge. Only if the philosophy came to some sort of conclusion would you even know how to conduct a measurement.
As long as we're not talking about mathematics in the grade school sense of computation, I consider it firmly to be philosophy, and certainly not science (at my university there was an entirely different department concerned with efficient computation, called of course "Math Science", to distinguish it from normal, non-science math).
Socialism: a lie told by totalitarians and believed by fools.
When I was in physics in the late 80s I had a professor that said he had done experiments on whether or not anti-matter would have anti-gravity effects. He stated that it behaved the same as matter with respect to gravity. Perhaps one of those cases of repeated work....
“Physics is to math what sex is to masturbation.”
-- Richard Feynman
So... maths is something you do when you're in the mood for physics but don't have anyone else to do it with? Or is it more a case of "I want to insult mathematics, and if I use a vulgar enough analogy maybe no-one will notice that I don't actually have an argument"?
I'm not Feynman (sorry!), but I can offer my interpretation of what this means beyond cheap-shot vulgarity.
So... maths is something you do when you're in the mood for physics but don't have anyone else to do it with?
That actually pretty much sums it up. Physics requires you to interact with your "partner" --- the real world --- to carry out the act. Mathematics occurs in the solitary world of your head --- you manipulate symbolic systems without the need to touch the real world and move in responsive dialog to its motions. In short, mathematics fucks with your mind, physics fucks with the world.
Physics requires you to interact with your "partner" --- the real world --- to carry out the act. Mathematics occurs in the solitary world of your head --- you manipulate symbolic systems without the need to touch the real world and move in responsive dialog to its motions.
So what's the difference in that analogy between theoretical physics and mathematics within any established branch? Admittedly with mathematics you can go completely wild and come up with a system that works however you want it to, but you could just as well invent a universe with different physical laws and try to figure out what the consequences would be. Conversely, with mathematics you'd almost always be working in an area with defined rules, and you have to comply with those rules just as much as you have to comply with how the physical world works when you're doing physics.
So what's the difference in that analogy between theoretical physics and mathematics within any established branch?
You pretty much answer your own question:
Admittedly with mathematics you can go completely wild and come up with a system that works however you want it to
and, even when you do the same under the guise of "science" (creating mathematical formalisms for "invented universes" entirely detached from experimental results), you've stopped doing science and started doing math. There's nothing wrong with math! I love math! I have a degree in math! But, if one is looking for the key technical distinction between "science" and other branches of philosophy, then connection to empirical observation is it --- whether or not you personally feel this is a big deal.
"The first mistake is to assume that helium rises. The truth is that it falls down towards the earth just like any other object. The reason for what you see is much simpler: It does not rise; it's just that everything else simply falls harder." (Freely translated from memory and German)
That is actually very misleading, to the point of being incorrect.
At the atomic level, a molecule of Oxygen falls at the same rate as an atom of Helium (about 9.8 m/(s^2), depending on altitude), so nothing really "falls harder".
What actually happens is the process of buoyancy. A He atom weighs about 16x less than an O molecule. A volume of air at specific temperature and pressure will contain the same number of particles (atoms or molecules).
If the volume contains relatively more He, the total mass of the volume will be less (lower density). If you surround this volume with volumes of higher density and place them in a gravitational field, then the sum of the pressure forces on the volume will not be in equilibrium. There will be a net force pushing the volume upwards.
At the atomic level, all the particles are falling constantly, bouncing off particles of lower layers (electrostatic repulsion), bouncing up again. At the macroscopic level, volumes of particles with lower density rise because the net forces on them are unbalanced. Back at the atomic level, particles that bounce off the bottom of the volume get an extra "push", and bounce back a bit higher.
Back at the atomic level, particles that bounce off the bottom of the volume get an extra "push", and bounce back a bit higher.
Actually, more accurate would be to say that the particles that bounce off the bottom of the volume will not hit it hard enough and frequently enough to repel all the particles from the denser volume below. So the top boundary of that denser volume will rise, moving the bottom of the less-denser volume upwards, causing the particles in that volume to bounce slightly higher.
"The first mistake is to assume that helium rises. The truth is that it falls down towards the earth just like any other object. The reason for what you see is much simpler: It does not rise; it's just that everything else simply falls harder." (Freely translated from memory and German)
That is actually very misleading, to the point of being incorrect.
At the atomic level, a molecule of Oxygen falls at the same rate as an atom of Helium (about 9.8 m/(s^2), depending on altitude), so nothing really "falls harder".
Yes.
This is why I specifically pointed out that there might be inaccuracies due to translation (and why I explained it in more detail further below). The term "falling harder" is on its own indeed slightly misleading compared to the German I translated it from. The forces acting on individual atoms are of course identical in both cases. After all, if only subject to gravity, a 1 gram feather will fall just as fast as a 1 kilogram brick.
But if you have an oil/water mixture in the same environment, no buoyancy -- as you explained it in more technical terms -- occurs. This is why I said that without an external impulse (as in: a force acting upon it), regular air will not displace helium just like water will not displace oil.
In the end, you can always dig deeper and deeper for more and more technical explanations. Each one iota more factually correct than the next, but also far harder to understand. This is why you invent abstractions and add a caveat to the tune of "this explanation is abridged". After all, there is no buoyancy, no gravity, no abstract "forces" acting upon anything. These are all mere abstractions for more fundamental processes that have only one thing in common: They are easier to understand.
After all, try to show someone the formulas that combine the standard model with relativity theory to explain the apparent curvature of space and its effects on matter down to the subatomic level. And then try to get from there to why helium rises. All the while explaining to them why some other concepts do not apply and why (for example how an oil/water emulsion overcomes the buoyancy of oil).
Good luck. :)
But if you have an oil/water mixture in the same environment, no buoyancy -- as you explained it in more technical terms -- occurs.
Replace "the same" with "a zero-gravity". Note to self: Don't try to think about the next sentence when typing the current one. :P
I'm surprised nobody mentioned Betteridge's law of headlines yet.
It *must* be more reliable than rigorous science experiments rignt ?
The point is that you were saying that the Scientific Method is what makes stuff Science. I'm saying, a lot of modern science can't rely on the scientific method you learned in sixth grade. As we try to understand our universe and the world around us, we are stuck making the best observations we can and trying to infer a model that we can't falsifiably test.
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The problem here is your understanding of the subjects you're referring to. Evolutionary Biology and Cosmology both make falsifiable predictions about our universe, which we can and have tested in the past.
They make some falsifiable predictions. We can apply selective evolutionary pressure to viruses and observe useful results, and do it repeatedly. We can interbreed and predictably speciate horses. But we cannot falsifiably predict that a single-cell organism will evolve into a horse under certain conditions, with a known set of evolutionary steps along the way. That doesn't stop us from looking at fossil records and trying to inductively trace back where horses came from and what conditions led to them and what the intermediate steps along the way were. And we still call it science.
With cosmology, we have billions of snap shots of different structures at different points in their lives, and we can look at them and say, "We think these are different stages of the same cycle." So we create a model. And we say, "If this model is correct, we would expect to find X somewhere." And then if X turns up, that increases the probability that the model is correct. But we can't create a universe and observe its evolution for 14 billion years. That doesn't stop us from creating models of how stars and planets and galaxies form, and we still call it science.
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