Time's Arrow

If a cup of water spills on the floor, the water can’t unspill—that is, it’s inconceivable that each water molecule would exactly reverse its course to slip back into the cup. To do so would be to turn back time—something that, as far as we know, can’t be done. The water either spills or it doesn’t, but if it does, it’ll stay that way.

In that way, time as we experience it is asymmetric. We have memories of the past rather than the future, and spilled water doesn’t flow back to its cup, just as an arrow that has been let fly doesn’t return to its bow. In our everyday lives, the “arrow of time” goes only in one direction: forward.

“We know [this] is something that’s part of our common experience,” says Andrea Rocco, a theoretical physicist at the University of Surrey in England. But how exactly time’s arrow arises is less clear to physicists, in part because the math they use to describe most of the world makes no distinction between time that moves forward and time that moves backward; either direction is perfectly viable, as far as their equations are concerned.

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The Quantum World Isn't so Weird?

Down at the level of atoms and electrons, quantum physics describes the behavior of the very smallest objects. Solar panels, LED lights, your mobile phone and MRI scanners in hospitals: all of these rely on quantum behavior. It is one of the best-tested theories of physics, and we use it all the time.


On the face of it, however, the quantum realm is extraordinary: Within it, quantum objects can be “in two places at once”; they can move through barriers; and share a connection no matter how far apart they are. Compared to what you would expect of, say, a tennis ball, their properties are certainly weird and counterintuitive.


But don’t let this scare you off! Much of quantum physics’ odd behavior becomes a lot less surprising if you stop thinking of atoms and electrons as minuscule tennis balls, and instead imagine any “quantum object” as something like a wave you create by pushing your hand through water. You could say that, at small scales, everything is made of waves.


In the spirit of demystifying quantum behavior, here are three key types of “weird” quantum phenomena that normal water waves can do just as well, and the one thing that sets the quantum world apart.     READ MORE...

Hidden Quantum World Inside the Proton

During a deeply inelastic collision with a proton, a relativistic electron (highlighted in blue) can emit a high-energy photon (purple here) that penetrates interior of the proton, where it ‘sees’ only a fraction of the entangled quarks, gluons, and virtual particles. The excited proton later decays in cascades of secondary particles. Credit: IFJ PAN, jch

Protons are far from simple particles — they are swirling cauldrons of quarks, gluons, and quantum entanglement.  Scientists have used this entanglement to develop a universal model explaining how particles emerge from high-energy collisions. 

Their predictions align with past experimental data, and future colliders will put their theory to the ultimate test, possibly reshaping our understanding of nuclear physics.

Peering Inside the Proton
The inside of a proton is one of the most dynamic yet elusive realms in physics. Within this tiny particle, quarks and gluons interact in a constantly shifting sea of virtual particles. 

Now, using quantum information theory and the concept of quantum entanglement, scientists have developed a new framework to describe these interactions with unprecedented clarity.

For the first time, this approach successfully explains data from all available experiments involving the scattering of secondary particles in deep inelastic collisions between electrons and protons.      READ MORE...

Gravitational Waves

As in history, revolutions are the lifeblood of science. Bubbling undercurrents of disquiet boil over until a new regime emerges to seize power. Then everyone's attention turns to toppling their new ruler. The king is dead, long live the king.

This has happened many times in the history of physics and astronomy. First, we thought Earth was at the center of the solar system — an idea that stood for over 1,000 years. Then Copernicus stuck his neck out to say that the whole system would be a lot simpler if we are just another planet orbiting the sun. Despite much initial opposition, the old geocentric picture eventually buckled under the weight of evidence from the newly invented telescope.

Then Newton came along to explain that gravity is why the planets orbit the sun. He said all objects with mass have a gravitational attraction towards each other. According to his ideas we orbit the sun because it is pulling on us, the moon orbits Earth because we are pulling on it. Newton ruled for two-and-a-half centuries before Albert Einstein turned up in 1915 to usurp him with his General Theory of Relativity. This new picture neatly explained inconsistencies in Mercury's orbit, and was famously confirmed by observations of a solar eclipse off the coast of Africa in 1919.

Instead of a pull, Einstein saw gravity as the result of curved space. He said that all objects in the universe sit in a smooth, four-dimensional fabric called space-time. Massive objects such as the sun warp the space-time around them, and so Earth's orbit is simply the result of our planet following this curvature. To us that looks like a Newtonian gravitational pull. This space-time picture has now been on the throne for over 100 years, and has so far vanquished all pretenders to its crown. The discovery of gravitational waves in 2015 was a decisive victory, but, like its predecessors, it too might be about to fall. That's because it is fundamentally incompatible with the other big beast in the physics zoo: Quantum theory.

The quantum world is notoriously weird. Single particles can be in two places at once, for example. Only by making an observation do we force it to 'choose'. Before an observation we can only assign probabilities to the likely outcomes. In the 1930s, Erwin Schrödinger devised a famous way to expose how perverse this idea is. He imagined a cat in a sealed box accompanied by a vial of poison attached to a hammer. The hammer is hooked up to a device that measures the quantum state of a particle. Whether or not the hammer smashes the vial and kills the cat hinges on that measurement, but quantum physics says that until such a measurement is made, the particle is simultaneously in both states, which means the vial is both broken and unbroken and the cat is alive and dead.  TO READ MORE, CLICK HERE...