Category: physics

This Is How Much Dark Matter Passes Through Yo…

This Is How Much Dark Matter Passes Through Your Body Every Second

“Dark matter, to the best of our knowledge, is out there in all directions. It may be invisible to our eyes, but we can feel its gravitational force. It passes through all the matter in the Universe, including human beings, as though it weren’t there at all. There are, to the best of our knowledge, no collisions or interactions other than its effects on curving spacetime. It doesn’t clump, cluster, or form structure like dark atoms or molecules.

And yet, if it has even the tiniest hint of an ability to collide with either normal matter or radiation, we’ll be able to detect it. Over the course of your life, about a milligram of dark matter will have passed through your body. If even one dark matter particle interacts with one proton or electron in your body, we’ll have a chance. When it comes to dark matter — one of the Universe’s deepest mysteries — it’s hard to ask for anything more.”

There’s a tremendous amount of astrophysical evidence that indicates the existence of dark matter. Grouped together in large, diffuse halos that surround every galaxy in the Universe, dark matter’s gravitational effects can be seen all across the Universe. This implies that there’s dark matter everywhere, including in the galaxy, in the Solar System, in the Earth, and even in your body. It’s not static, but simply passes right through you. If we can calculate and/or estimate how much dark matter there is and what it’s properties are, we can even come up with a figure for how much dark matter passes through you every second, and learn what that means for trying to directly detect it.

A human body might not be a great dark matter detector, but over your lifetime, a milligram of dark matter will have passed through your body. Come get the full story to learn more!

The Surprising Reason Why Neutron Stars Don&rs…

The Surprising Reason Why Neutron Stars Don’t All Collapse To Form Black Holes

“The measurements of the enormous pressure inside the proton, as well as the distribution of that pressure, show us what’s responsible for preventing the collapse of neutron stars. It’s the internal pressure inside each proton and neutron, arising from the strong force, that holds up neutron stars when white dwarfs have long given out. Determining exactly where that mass threshold is just got a great boost. Rather than solely relying on astrophysical observations, the experimental side of nuclear physics may provide the guidepost we need to theoretically understand where the limits of neutron stars actually lie.”

If you take a large, massive collection of matter and compress it down into a small space, it’s going to attempt to form a black hole. The only thing that can stop it is some sort of internal pressure that pushes back. For stars, that’s thermal, radiation pressure. For white dwarfs, that’s the quantum degeneracy pressure from the electrons. And for neutron stars, there’s quantum degeneracy pressure between the neutrons (or quarks) themselves. Only, if that last case were the only factor at play, neutron stars wouldn’t be able to get more massive than white dwarfs, and there’s strong evidence that they can reach almost twice the Chandrasekhar mass limit of 1.4 solar masses. Instead, there must be a big contribution from the internal pressure each the individual nucleon to resist collapse.

For the first time, we’ve measured that pressure distribution inside the proton, paving the way to understanding why massive neutron stars don’t all form black holes.

New Stars Turn Galaxies Pink, Even Though Ther…

New Stars Turn Galaxies Pink, Even Though There Are No ‘Pink Stars’

“New star-forming regions produce lots of ultraviolet light, which ionizes atoms by kicking electrons off of their nuclei.

These electrons then find other nuclei, creating neutral atoms again, eventually cascading down through its energy levels.

Hydrogen is the most common element in the Universe, and the strongest visible light-emitting transition is at 656.3 nanometers.

The combination of this red emission line — known as the Balmer alpha (or Hα) line — with white starlight adds up to pink.”

When you look through a telescope’s eyepiece at a distant galaxy, it will always appear white to you. That’s because, on average, starlight is white, and your eyes are more sensitive to white light than any color in particular. But with the advent of a CCD camera, collecting individual photons one-at-a-time, you can more accurately gauge an astronomical object’s natural color. Even though new stars are predominantly blue in color, star-forming regions and galaxies appear pink. The problem compounds itself when you realize there isn’t any such thing as a pink star! And yet, there’s a straightforward physical explanation for what we see.

It’s a combination of ultraviolet radiation, white starlight, and the physics of hydrogen atoms that turn galaxies pink. Find out how, with some incredible  visuals, today!

Could We Create A Bottomless Pit On Earth?

Could We Create A Bottomless Pit On Earth?

“A round-trip journey, from the North Pole to just shy of the South Pole and back to the North Pole again, all through the Earth’s center, should take just a whisker under 90 minutes. Under ideal conditions:

* creating a vacuum,
* straight through the Earth’s rotational axis,
* starting with no tangential velocity,
* devoid of any type of air resistance and subject only to gravitational forces,

you’d wind up right back where you started just 90 minutes later: roughly the same time it takes the international space station to orbit the Earth. So long as you brought an oxygen supply with you, you’d be no worse for the wear.”

From tourist traps to Alice in Wonderland to modern entertainment like Gravity Falls, bottomless pits are tropes that hardly seem physically possible. Sure, you can always envision a thought experiment, but that doesn’t mean you could actually build one. Despite the engineering challenges and the enormous expense that would be associated with such a project, this one turns out to be physically plausible with not-too-distant-future technology. There are a number of obstacles we’d have to overcome, including the Earth’s rotation, drilling a shaft clear through the planet, and stabilizing a passenger against the heat and radioactivity of the natural interior of our world. But if we could do it, and not get stuck at the center, we’d come back to where we started just 90 minutes later.

Here’s the story behind how to create and successfully use a bottomless pit here on Earth!

Found on a whiteboard while cleaning

Found on a whiteboard while cleaning

This Is Why Physicists Think String Theory Mig…

This Is Why Physicists Think String Theory Might Be Our ‘Theory Of Everything’

“String theory offers a path to quantum gravity, which few alternatives can truly match. If we make the judicious choices of “the math works out this way,” we can get both General Relativity and the Standard Model out of it. It’s the only idea, to date, that gives us this, and that’s why it’s so hotly pursued. No matter whether you tout string theory’s successes or failure, or how you feel about its lack of verifiable predictions, it will no doubt remain one of the most active areas of theoretical physics research. At its core, string theory stands out as the leading idea of a great many physicists’ dreams of an ultimate theory.”

You don’t have to be a fan of string theory to understand why it’s such a promising area of scientific research. One of the holy grails of physics is for a quantum theory of gravitation: that describes gravity on the same footing as the other three forces, in very strong fields and at very tiny distances. Surprisingly, by looking at analogies between gravity and field theories, replacing particles with strings might be the answer.

It’s an incredibly difficult concept to understand why this would be the case without a slew of advanced mathematics, but in 2015, the world’s leading string theorist, Ed Witten, tried. That is to say, he wrote a piece for other physicists entitled, “What every physicist should know about string theory.” 

But what if you want to understand it and you’re not a physicist? Then you should read this.

The 5 Most Important Rules For Scientists Who …

The 5 Most Important Rules For Scientists Who Write About Science

“Remember that your number one goal, if you’re a scientist writing about your science, is to increase the excitement and knowledge of your audience about what it is that you do. What we’re learning about all aspects of the Universe is expanding and increasing every day, and that joy and wonder should carry over to all of us in our daily lives. We cannot be experts in each and every field, but that underscores exactly why we need experts, and to respect true expertise when we encounter it.

If we take care to communicate responsibly, we can all gain a greater awareness of what it is that we do understand, as well as an appreciation for what that knowledge means. We may never run out of questions to ponder about the Universe itself, but with a little care and effort, we can all come a little bit closer to comprehending the answers.”

For most of us, we recognize that our expertise is extremely limited in all but a few areas. In order to learn what’s going on at the cutting edge of human knowledge, we have to go to the experts. In fields like physics, astronomy, biology, and chemistry, that means going to the scientists who study those fields. Yet scientists who communicate their own science often are some of the worst communicators out there, either getting mired in the details and losing the big picture or oversimplifying things to the point where they misinform their audience. Yet, if they just followed these five rules, they could avoid the most common mistakes and do what they set out to: inform the world about what they do and why it matters.

Come get the five most important rules for scientists who write about science. I bet you find value here even if you’re not a scientist yourself!

Ask Ethan: Can We Build A Sun Screen To Combat…

Ask Ethan: Can We Build A Sun Screen To Combat Global Climate Change?

“[W]hy don’t we evaluate building a “sun screen” in space to alter the amount of light (energy) earth receives? Everybody who did feel a total eclipse knows temperature goes down and light dims. So the idea is to build something that would stay between us and sun all year long…”

The Earth’s temperature is rising: that’s a fact. The overwhelming cause of this warming is human-caused emissions of greenhouse gases, like CO2 and methane. The CO2 concentration has now passed 410 parts per million, an increase of over 50% over pre-industrial revolution levels. If we cannot or will not reverse what’s driving the temperature change, we could instead try to counteract it. One proposal is to put a large device in space, between the Sun and the Earth, to block some of the incoming sunlight. As it turns out, blocking 2% would be enough to completely counteract the effects of human-caused global warming. Modifying our atmosphere is risky, but placing a sun screen in space to do the job has only one real drawback: its expense.

But how expensive is it, truly, when you consider the positive effects it would have on the planet? Let’s consider what it would take to combat global climate change by putting a shade in space!

The EmDrive, NASA’s ‘Impossible&rs…

The EmDrive, NASA’s ‘Impossible’ Space Engine, Really Is Impossible

“Tajmar’s results are exactly what you’d expect for the systematic error explanation: with a properly shielded apparatus, with no additional electromagnetic fields induced by the wires, there is no observed thrust at any power. They conclude that these induced fields by the electrical wires, visibly present in the other setups, are the likely culprit for the observed, unexplained thrust:

‘Our results show that the magnetic interaction from not sufficiently shielded cables or thrusters are a major factor that needs to be taken into account for proper µN thrust measurements for these type of devices.’

To the best of our knowledge, then, rockets will still require propellant.

The EmDrive isn’t a reactionless drive at all, and all the laws of physics should still work. In short, we fooled ourselves.”

For years, many tinkerers and inventors have been claiming that some sort of electromagnetic cavity, e.g., the EmDrive, can create a reactionless drive. That is, they claim they can change the momentum of a rocket without any sort of change-in-momentum of anything else, violating Newton’s action-reaction law. Needless to say, much like perpetual motion, physicists are largely skeptical. But until now, we hadn’t yet found why they were achieving the results that they did. However, a new source of error was just uncovered: magnetic fields originating from the cables that power the device. Properly set up the device, away from cables and loops of wires, as Martin Tajmar’s team did, and guess what: your ‘anomalous thrust’ disappears.

The EmDrive, billed as NASA’s impossible space engine, really was too good to be true.

The best free response answer of the year goes…

The best free response answer of the year goes to this kid