Chemist John Dalton proposed the theory that all matter and objects are made up of particles called atoms, and this is still accepted by the scientific community, almost two centuries later. Each of these atoms is each made up of an incredibly small nucleus and even smaller electrons, which move around at quite a distance from the center.

 If you imagine a table that is a billion times larger, its atoms would be the size of melons. But even so, the nucleus at the center would still be far too small to see and so would the electrons as they dance around it. So why don’t our fingers just pass through atoms, and why doesn’t light get through the gaps?

To explain why we must look at the electrons. Unfortunately, much of what we are taught at school is simplified – electrons do not orbit the center of an atom like planets around the sun, like you may have been taught. Instead, think of electrons like a swarm of bees or birds, where the individual motions are too fast to track, but you still see the shape of the overall swarm.

In fact, electrons dance – there is no better word for it. But it’s not random dancing – it’s more like ballroom dancing, where they move in set patterns, following steps laid down by a mathematical equation named after Erwin Schrödinger.

These patterns can vary – some are slow and gentle, like a waltz whereas some are fast and energetic, like a Charleston. Each electron keeps to the same pattern, but once in a while it may change to another, as long as no other electron is doing that pattern already. No two electrons in an atom can do the same step: this rule is called the Exclusion Principle.

Electrons are like a swarm of birds. John Holmes/Wikimedia Commons, CC BY-SA

Although electrons never tire, moving up to a faster step does take energy. And when an electron moves down to a slower pattern it loses energy which it gives out. So when energy in the form of light falls on an electron, it can absorb some energy and move up to a higher, faster “dance” pattern. A light beam won’t get far through our table, since the electrons in all the atoms are eager to grab some energy from the light.

After a very short while they lose this gained energy, perhaps as light again. Changes in the patterns of absorbed and reflected light give reflections and colours - so we see the table as solid.

So why does a table also feel solid? Many websites will tell you that this is due to the repulsion – that two negatively charged things must repel each other. But this is wrong, and shows you should never trust some things on the internet. It feels solid because of the dancing electrons.

If you touch the table, then the electrons from atoms in your fingers become close to the electrons in the table’s atoms. As the electrons in one atom get close enough to the nucleus of the other, the patterns of their dances change. This is because, an electron in a low energy level around one nucleus can’t do the same around the other – that slot’s already taken by one of its own electrons. The newcomer must step into an unoccupied, more energetic role. That energy has to be supplied, not by light this time but by the force from your probing finger.

The table resistance is strong. Shutterstock

So pushing just two atoms close to each other takes energy, as all their electrons need to go into unoccupied high-energy states. Trying to push all the table-atoms and finger-atoms together demands an awful lot of energy – more than your muscles can supply. You feel that, as resistance to your finger, which is why and how the table feels solid to your touch.

Roger Barlow, Research Professor and Director of the International Institute for Accelerator Applications, University of Huddersfield.

Electrodes two millimeters apart trap a single atom. David Nadlinger - University of Oxford

An image of a single atom of the metal strontium suspended in electric fields has won the 2018 Engineering and Physical Sciences Research Council science photography competition.

David Nadlinger‘s photo, Single Atom In An Ion Trap, was captured through the window of a vacuum chamber in an Oxford University laboratory, using an ordinary digital camera on a long exposure shot.

Two metal electrodes, two millimetres apart, held the strontium almost motionless in a strong electric field as it was illuminated with a blue-violet-coloured laser.

The tiny, blue dot is an illuminated strontium atom. David Nadlinger - University of Oxford

Strontium atoms are relatively large, with radii around 215 billionths of a millimeter. The atom is visible in this photograph because it absorbs and re-emits the bright light of the laser.

Extremely still strontium atoms like this one are used in atomic clocks. Each tick of one of these hyper-precise clocks is determined by the frequency of radiation emitted when electrons around an atom change energy states.

Read more: Smile, hydrogen atom, you’re on quantum camera

Article was originally published on New Scientist.

Everything and everything in the universe is made up of atoms — except, of course, atoms themselves. They are made up of subatomic particles, namely, protons, neutrons, and electrons. While electrons are classified as leptons, protons and neutrons are in a class of particles famously known as quarks. Though, “known” may be a bit misleading: there is a lot more theoretical physicists don’t know about the particles than they do with any degree of certainty.

As far as we know, quarks are the fundamental particle of the universe. You can’t break a quark down into any smaller particles. Imagining them as being uniformly minuscule is not quite accurate, however: while they are tiny, they are not all the same size. Some quarks are larger than others, and they can also join together and create mesons (1 quark + 1 antiquark) or baryons (3 quarks of various flavors).

In terms of possible quark flavors, which are respective to their position, we’ve identified six: up, down, top, bottom, charm, and strange. As mentioned, they usually pair up either in quark-antiquark pairs or a quark threesome — so long as the charges ( ⅔, ⅔, and ⅓ ) all add up to positive 1.

The so-called tetraquark pairing has long-eluded scientists; a hadron which would require 2 quark-antiquark pairs, held together by the strong force. Now, it’s not enough for them to simply pair off and only interact with their partner. To be a true tetraquark, all four quarks would need to interact with one another; behaving as quantum swingers, if you will.

 

It might seem like a pretty straightforward concept: throw four quarks together and they’re bound to interact, right? Well, not necessarily. And that would be assuming they’d pair off stably in the first place, which isn’t a given. As Marek Karliner of Tel Aviv University explained to LiveScience, two quarks aren’t any more likely to pair off in a stable union than two random people you throw into an apartment together. When it comes to both people and quarks, close proximity doesn’t ensure chemistry.

“The big open question had been whether such combinations would be stable, or would they instantly disintegrate into two quark-antiquark mesons,” Karliner told Futurism. “Many years of experimental searches came up empty-handed, and no one knew for sure whether stable tetraquarks exist.”

Most discussions of tetraquarks up until recently involved those “ad-hoc” tetraquarks; the ones where four quarks were paired off, but not interacting. Finding the bona-fide quark clique has been the “holy grail” of theoretical physics for years – and we are agonizingly close.

Recalling that quarks are not something we can actually see, it probably goes without saying that predicting the existence of such an arrangement or particle would be incredibly hard to do. 

The very laws of physics dictate that it would be impossible for four quarks to come together and form a stable hadron. But two physicists found a way to simplify (as much as you can “simplify” quantum mechanics) the approach to the search for tetraquarks.

Several years ago, Karliner and his research partner, Jonathan Rosner of the University of Chicago, set out to establish the theory that if you want to know the mass and binding energy of rare hadrons, you can start by comparing them to the common hadrons you already know the measurements for. In their research they looked at charm quarks; the measurements for which are known and understood (to quantum physicists, at least).

Based on these comparisons, they proposed that a doubly-charged baryon should have a mass of 3,627 MeV, +/- 12 MeV. The next step was to convince CERN to go tetraquark-hunting, using their math as a map.

For all the complex work it undertakes, the vast majority of which is nothing detectable by the human eye, The Large Hadron Collider is exactly what the name implies: it’s a massive particle accelerator that smashes atoms together, revealing their inner quarks. If you’re out to prove the existence of a very tiny theoretical particle, the LHC is where you want to start — though there’s no way to know how long it will be before, if ever, the particles you seek appear.

It took several years, but in the summer of 2017, the LHC detected a new baryon: one with a single up quark and two heavy charm quarks — the kind of doubly-charged baryon Karliner and Rosner were hoping for. The mass of the baryon was 3,621 MeV, give or take 1 MeV, which was extremely close to the measurement Karliner and Rosner had predicted. Prior to this observation physicists had speculated about — but never detected — more than one heavy quark in a baryon. In terms of the hunt for the tetraquark, this was an important piece of evidence: that more robust bottom quark could be just what a baryon needs to form a stable tetraquark.

The perpetual frustration of studying particles is that they don’t stay around long. These baryons, in particular, disappear faster than “blink-and-you’ll-miss-it” speed; one 10/trillionth of a second, to be exact. Of course, in the world of quantum physics, that’s actually plenty of time to establish existence, thanks to the LHC.

The great quantum qualm within the LHC, however, is one that presents a significant challenge in the search for tetraquarks: heavier particles are less likely to show up, and while this is all happening on an infinitesimal level, as far as the quantum scale is concerned, bottom quarks are behemoths.

The next question for Rosner and Karliner, then, was did it make more sense to try to build a tetraquark, rather than wait around for one to show up? You’d need to generate two bottom quarks close enough together that they’d hook up, then throw in a pair of lighter antiquarks — then do it again and again, successfully, enough times to satisfy the scientific method.

“Our paper uses the data from recently discovered double-charmed baryon to point, for the first time, that a stable tetraquark *must* exist,” Karliner told Futurism, adding that there’s “a very good chance” the LHCb at CERN would succeed in observing the phenomenon experimentally.

That, of course, is still a theoretical proposition, but should anyone undertake it, the LHC would keep on smashing in the meantime — and perhaps the combination would arise on its own. As Karliner reminded LiveScience, for years the assumption has been that tetraquarks are impossible. At the very least, they’re profoundly at odds with the Standard Model of Physics. But that assumption is certainly being challenged. “The tetraquark is a truly new form of strongly-interacting matter,” Karliner told Futurism,”in addition to ordinary baryons and mesons.”

If tetraquarks are not impossible, or even particularly improbable, thanks to the Karliner and Rosner’s calculations, at least now we have a better sense of what we’re looking for — and where it might pop up.

Where there’s smoke there’s fire, as they say, and while the mind-boggling realm of quantum mechanics may feel more like smoke and mirrors to us, theoretical physicists aren't giving up just yet. Where there’s a 2-bottom quark, there could be tetraquarks.

References: Nature, LiveScience, APS Physics

Article was originally published on Futurism.

If you’re reading this right now, it’s a sure bet that you are touching something, be it your cellphone, laptop, chair, desk, or a nice plush bed with Egyptian-cotton sheets (we can dream, right?). Speaking of that nice plush, comfy bed, I hate to shatter the illusion, but you aren’t actually touching it.

Everything you can see, touch, and “feel” is made up of atoms — the infinitesimally small constituent parts of matter. The field of study related to these, called “quantum physics,” gives us plenty of insane things to consider about the world around us — specifically, the indistinguishable activities going on at an atomic scale.

Ultimately, it may seem the atomic world isn’t particularly relevant to our day-to-day lives. However, this information is a key point when it comes to our understanding of how the four forces shape the physical world, and thus, it is key to understanding the universe. After all, you can’t understand how large things work without knowing the ins-and-outs of the small stuff, too.

Among the phenomena it encompasses, we have: quantum entanglement, particles that pop in-and-out of existence; the particle-wave duality, particles that shape-shift at random; strange states of matter; and even strange matter itself. Quantum mechanics also tells us that we are made up of particles, which means that, microscopically, all sorts of strange things are going on within us that aren’t perceivable to the human eye — things that sometimes seem to make little sense.

To understand why you can never touch anything, you need to understand how electrons function, and before you can understand that, you need to know basic information about the structure of atoms.

For starters, almost all of the mass an atom has is concentrated into an incredibly small region called the nucleus. Surrounding the nucleus is a whole lot of seemingly empty space, except for the region within an atom where electrons (and protons) can be found orbiting the central nucleus. The number of electrons within an atom depends on the element each atom is suppose to comprise.

Like photons, this funky subatomic particle also exhibits the particle-wave duality, which means that the electron has characteristics of both a particle and a wave. On the other hand, they have a negative charge. Particles are, by their very nature, attracted to particles with an opposite charge, and they repel other similarly charged particles.

This prevents electrons from ever coming in direct contact (in an atomic sense and literal sense). Their wave packets, on the other hand, can overlap, but never touch.

The same is true for all of humankind. When you plop down in a chair or slink into your bed, the electrons within your body are repelling the electrons that make up the chair. You are hovering above it by a unfathomably small distance.

I’m sure some of you will wonder, “If electron repulsion prevents us from ever truly touching anything, why do we perceive touch as a real thing?” The answer boils down to how our brains interpret the physical world.

In this case, a number of factors are at work. The nerve cells that make up our body send signals to our brain that tell us that we are physically touching something, when the  sensation of touch is merely given to us by our electron’s interaction with — i.e., its repulsion from — the electromagnetic field permeating spacetime (the medium electron waves propagate through).

Also note, various things play a role here in making collections of particles into tangible things. We have things such as chemical bonding and, of course, the four primary forces mentioned above. Chemical bonds allow electrons to “latch on” to imperfections within an object’s surface, creating friction.

For those that have persevered thus far:

You will see that the purely electro-static repulsion between electrons is not the only reason why you hover above your chair. In the normal case, it’s about as strong as the Pauli Exclusion Principle when it comes to pushing things apart. It’s actually a combination of these two effects dominating the actual behavior. By that, I am speaking of the unbelievable idea that electrons know where every other electron is, and they try to avoid each other as much as possible, resulting in an exponential decrease in the force between electrons, even without the electromagnetic repulsion in play.

All in all, isn’t it amazing how these things relate? It’s a fundamental scientific truth that things are often not as they seem, or at least, they are not as we perceive them to be. It throws everything we think about the universe into a new light.

Additional commentary provided by Kaijian Xiao

References: Gizmodo, Argonne National Laboratory

Article was originally published in Futurism.

Chemist John Dalton proposed the theory that all matter and objects are made up ofparticles called atoms, and this is still accepted by the scientific community, almost two centuries later. Each of these atoms is each made up of an incredibly small nucleus and even smaller electrons, which move around at quite a distance from the centre. If you imagine a table that is a billion times larger, its atoms would be the size of melons. But even so, the nucleus at the centre would still be far too small to see and so would the electrons as they dance around it. So why don’t our fingers just pass through atoms, and why doesn’t light get through the gaps?

To explain why we must look at the electrons. Unfortunately, much of what we are taught at school is simplified – electrons do not orbit the centre of an atom like planets around the sun, like you may have been taught. Instead, think of electrons like a swarm of bees or birds, where the individual motions are too fast to track, but you still see the shape of the overall swarm.

In fact, electrons dance – there is no better word for it. But it’s not random dancing – it’s more like ballroom dancing, where they move in set patterns, following steps laid down by a mathematical equation named after Erwin Schrödinger.

 

These patterns can vary – some are slow and gentle, like a waltz whereas some are fast and energetic, like a Charleston. Each electron keeps to the same pattern, but once in a while it may change to another, as long as no other electron is doing that pattern already. No two electrons in an atom can do the same step: this rule is called the Exclusion Principle.

Although electrons never tire, moving up to a faster step does take energy. And when an electron moves down to a slower pattern it loses energy which it gives out. So when energy in the form of light falls on an electron, it can absorb some energy and move up to a higher, faster “dance” pattern. A light beam won’t get far through our table, since the electrons in all the atoms are eager to grab some energy from the light.

After a very short while they lose this gained energy, perhaps as light again. Changes in the patterns of absorbed and reflected light give reflections and colours - so we see the table as solid.

So why does a table also feel solid? Many websites will tell you that this is due to the repulsion – that two negatively charged things must repel each other. But this is wrong, and shows you should never trust some things on the internet. It feels solid because of the dancing electrons.

If you touch the table, then the electrons from atoms in your fingers become close to the electrons in the table’s atoms. As the electrons in one atom get close enough to the nucleus of the other, the patterns of their dances change. This is because, an electron in a low energy level around one nucleus can’t do the same around the other – that slot’s already taken by one of its own electrons. The newcomer must step into an unoccupied, more energetic role. That energy has to be supplied, not by light this time but by the force from your probing finger.

So pushing just two atoms close to each other takes energy, as all their electrons need to go into unoccupied high-energy states. Trying to push all the table-atoms and finger-atoms together demands an awful lot of energy – more than your muscles can supply. You feel that, as resistance to your finger, which is why and how the table feels solid to your touch.

RogerBarlow, Research Professor and Director of the International Institute for Accelerator Applications, University of Huddersfield.

This article was originally published on The Conversation. Read the originalarticle.