Category: SCIENCE

The Universe isn’t just expansion, but the expansion itself is accelerating. So why can’t we feel it in any measurable way?

One of the more puzzling and counterintuitive facts about the Universe is that what we experience as space — or the distance/separation between objects — isn’t something that’s fixed over time. Instead, distances evolve, and not in the same way, on cosmic scales, that they evolve here on Earth, in our Solar System, or within our galaxy. Within these more familiar systems, distances tend to change based on the forces acting on the objects in question: specifically, the force of gravity, which works to attract all objects with mass, as well as the electromagnetic and nuclear forces, which tend to dominate on smaller, lower-mass scales.

But on larger cosmic scales, the Universe truly is expanding, and moreover, that expansion is accelerating. Why is this expansion something that we don’t experience in any way here on Earth, and can’t even feel or detect in terrestrial experiments with even our most sensitive instruments? That’s what Jim wants to know, as he writes in to ask:

“Many cosmologists believe that the expansion of the universe is accelerating. If so, why don’t we feel it…

No matter how good our measurement devices get, certain quantum properties always possess an inherent uncertainty. Can we figure out why?

Perhaps the most bizarre property we’ve discovered about the Universe is that our physical reality doesn’t seem to be governed by purely deterministic laws. Instead, at a fundamental, quantum level, the laws of physics are only probabilistic: you can compute the likelihood of the possible experimental outcomes that will occur, but only by measuring the quantity in question can you truly determine what your particular system is doing at that instant in time. Furthermore, the very act of measuring/observing certain quantities leads to an increased uncertainty in certain related properties: what physicists call conjugate variables.

While many have put forth the idea that this uncertainty and indeterminism might only be apparent, and could be due to some unseen “hidden” variables that truly are deterministic, we have yet to find a mechanism that allows us to successfully predict any quantum outcomes. But could the quantum fields inherent to space be the ultimate culprit? Could it be the quantum vacuum itself that supplies whatever it is that’s necessary to cause the quantum uncertainty we experience whenever we try and make…

The Universe is 13.8 billion years old, going back to the hot Big Bang. But was that truly the beginning, and is that truly its age?

According to the theory of the hot Big Bang, the Universe had a beginning. Originally known as “a day without a yesterday,” this is one of the most controversial, philosophically mind-blowing pieces of information we’ve come to accept as part of the scientific history of our Universe. Many detractors will reject it as being too in-line with certain religious texts, while others — perhaps more justifiably — note that in the modern context of cosmic inflation, the hot Big Bang only occurred as the aftermath of a preceding epoch.

And yet, if you ask any cosmologist or astrophysicist who’s well-versed in the scientific story of our beginnings “How old is our Universe?” you always get the same answer: 13.8 billion years. Why is this, and when do we start counting the Universe’s age? We always say that the leftover glow from the Big Bang, or the cosmic microwave background (CMB), comes to us from an epoch that was 380,000 years have elapsed. But the CMB doesn’t mark the beginning of the Universe, and there’s a very compelling, but little-known and widely underappreciated, reason to begin counting the…

Many contrarians dispute that cosmic inflation occurred. The evidence says otherwise.

For as long as humans have been around, our innate curiosity has compelled us to ask questions about the universe. Why are things the way they are? How did they get to be this way? Were these outcomes inevitable or could things have turned out differently if we rewound the clock and began things all over again? From subatomic interactions to the grand scale of the cosmos, it’s only natural to wonder about it all. For innumerable generations, these were questions that philosophers, theologians, and mythmakers attempted to answer. While their ideas may have been interesting, they were anything but definitive.

Modern science offers a superior way of approaching these puzzles. No longer do we consider the Big Bang, once thought to be the ultimate origin of our Universe, to have occurred at a single moment or event in space and time. We can now ask questions such as “what existed before the Big Bang?” as well as “why did the Big Bang happen?” When it comes to even the biggest questions of all, science provides us with the best answers we can muster, given what we know and what remains unknown, at any point in time. Here and now, these are the best robust conclusions we can reach.

The original principle of relativity, proposed by Galileo way back in the early 1600s, remains true in its unchanged form even today.

When most people think of the term relativity, the first person who comes to mind is Albert Einstein. Indeed, Einstein’s two theories of relativity — the special theory of relativity, put forth in 1905, and the general theory of relativity, put forth a decade later in 1915 — represent a revolutionary way of viewing our Universe. Prior to Einstein, it was thought that both space and time were absolute quantities: the same for all observers, regardless of their location or of their motion through the Universe. It was thought that the amount of time that passed for anyone, anywhere, would be universally agreed upon, as would the distance between any two points or the physical size of solid objects. Only with the arrival of Einstein was it recognized that even quantities such as space and time weren’t absolute at all, but were instead experienced relative to the observer’s point of view.

But Einstein didn’t originate the concept of relativity at all. In fact, relativity can trace its origins back to nearly 400 years ago: when it was put forth by a scientist who obsessively studied the behavior of…

The largest particle accelerator and collider ever built is the Large Hadron Collider at CERN. Why not go much, much bigger?

The Large Hadron Collider (LHC) is the largest, most powerful particle accelerator ever built on Earth. Accelerating protons up to energies of ~7 TeV apiece — to energies about 7000 times greater than their rest-mass energy as given by E=mc² — it smashes protons circulating clockwise with protons circulating counterclockwise into one another at specific collision points, where giant detectors then measure the debris emerging from those collisions and attempt to reconstruct them in an effort to probe fundamental physics. After announcing the discovery of the Higgs boson in 2012, it continues to probe the subatomic universe to the highest precisions of all-time.

But in order to push the frontiers of physics even further, a new, more powerful machine will be required: a future particle collider. Although there are four main concepts currently being considered, there are many who ultimately hope for a particle accelerator the size of Earth, or even greater. That’s what Gary Camp has been thinking about, as he writes in to ask:

“Since bigger is better (so far) I am toying with the idea of a collider…

The Michelson-Morley experiment of 1887, despite expectations, revealed a null result: no effect. The implications were revolutionary.

Imagine being alive in the late 1800s, and thinking about one of the most important physical phenomena in the Universe: light. A number of things that we take for granted today were already known about it. We knew that light:

• moved at the speed of light, around 300,000 km/s,
• exhibited wave-like behaviors such as interference and diffraction,
• and was electromagnetic in nature, with oscillating in-phase electric and magnetic fields.

We did make an underlying assumption about light, however, that wasn’t necessarily true: that, like all known waves, it required a medium to travel through. Just like water waves required the water, seismic waves required the Earth, and sound waves required the air to travel through, light was assumed to have a medium as well, known as the luminiferous aether.

Since light was known to propagate through a vacuum — such as the vacuum of space that separated the Earth from the Sun — it never occurred to most that light didn’t need a medium to propagate through; it was…

Today, the Large Hadron Collider is the most powerful particle physics experiment in history. What would a new, successor collider teach us?

Right now, the Large Hadron Collider (LHC) is the most powerful particle accelerator/collider ever built. Accelerating protons up to 299,792,455 m/s, just 3 m/s shy of the speed of light, they smash together at energies of 14 TeV, creating all sorts of new particles (and antiparticles) from raw energy, leveraging Einstein’s famous E = mc² in an innovative way. By building detectors around the collision points, we can uncover all sorts of properties about any known particles and potentially discover new particles as well, as the LHC did for the Higgs boson back in the early 2010s.

Peaking on the night of August 11/12, up to 100 bright meteors per hour will be visible. Here’s how to make the most of it.

Every year in August, the night sky comes alight with meteors, as planet Earth plows through the debris stream of Comet Swift-Tuttle, giving rise to the Perseid meteor shower. Because of Swift-Tuttle’s large, massive size and the fact that it’s been in its present orbit for thousands of years, it’s produced an impressively large debris stream. The The fact that Swift-Tuttle travels very far from Earth, as it has an orbital period around the Sun of 133 years (nearly twice as long as Halley’s comet), means that the debris moves very rapidly with respect to Earth. And the fact that Swift-Tuttle is also a potentially hazardous object to Earth — one that crosses Earth’s orbits nearly perfectly — means that each year, as Earth passes through its debris stream, the meteor shower that it puts on is spectacular.

The Perseid meteor shower is reliably Earth’s greatest annual show, with around 100 meteors-per-hour at its peak and where most of the meteors fast-moving, with a lot of kinetic energy, results in a bright, luminous show from practically anywhere on Earth with clear skies. Although the Moon can often get in the way, this year, on the night of…

How do normal matter and dark matter separate by so much when galaxy clusters collide? Astronomers find the surprising, unexpected answer.

When galaxy clusters collide, something fascinating happens.

The individual galaxies and collisionless dark matter simply pass through one another, unscathed.

But the gas within each cluster collides, heats up, and slows down.

This creates an observed separation between the light-emitting gas and the gravitational effects of overall mass.