Category: physics

Perhaps I did


“Mathematics is the taming of the infinite.”

— Linear Algebra professor

This Is How Astronomers Will Finally Measure The Universe’s Expansion Directly

“This is why, by measuring the redshifts and distances to a slew of objects ⁠— objects at a variety of different distances and redshifts ⁠— we can reconstruct the expansion of the Universe over its history. The fact that a whole slew of disparate data sets are all consistent with not only one another but with an expanding, evenly filled Universe in the context of relativity, that gives us the confidence we have in our model of the Universe.

But, just as we didn’t necessarily accept gravitational waves before they were directly measured by LIGO, there’s still the possibility that we’ve made a mistake somewhere in inferring the properties of the Universe. If we could take a distant object, measure its redshift and distance, and then come back at a later time to see how its redshift and distance had changed, we’d be able to directly (instead of indirectly) measure the expanding Universe for the first time.”

We’ve measured the distance to literally billions of objects all over the Universe, from within our galaxy to more than 30 billion light-years away. By observing how the light from these distant objects is shifted, we’re able to infer that the Universe is expanding. We’re able to infer how that expansion rate has changed over time. And we’re able to infer what the Universe is made of: a monumental accomplishment.

But what we’ve never been able to do, as of 2019, is to watch an individual, distant galaxy physically expand away from us in real-time. With the new generation of 30-meter class telescopes we have coming online, though, all of that is poised to change. When the ELT arrives, the largest of the next generation telescopes at 39 meters, it will have the capability to make this measurement directly by observing the same sets of quasars 10 years apart.

You’re going to get to learn a new term today: redshift drift. When we measure it, we’ll have our first direct observation of the Universe as it physically expands on human timescales.

Even In A Quantum Universe, Space And Time Might Be Continuous, Not Discrete

“In General Relativity, matter and energy tell space how to curve, while curved space tells matter and energy how to move. But in General Relativity, space and time are continuous and non-quantized. All the other forces are known to be quantum in nature, and require a quantum description to match reality. We assume and suspect that gravitation is fundamentally quantum, too, but we aren’t sure. Furthermore, if gravity is ultimately quantum, we don’t know whether space and time remain continuous, or whether they become fundamentally discrete.

Quantum doesn’t necessarily mean that every property breaks down into an indivisible chunk. In conventional quantum field theory, spacetime is the stage upon which the various quanta act out the play of the Universe. At the core of it all should be a quantum theory of gravity. Until we can determine whether space and time are discrete, continuous, or unavoidably blurred, we cannot know our Universe’s nature at a fundamental level.”

If you could look at the Universe down to the smallest possible scales, fundamentally, what would you find? Would you discover that space and time really could be broken up into tiny, indivisible entities where the was a length scale and a timescale that could be divided no further? Would you discover that space and time were quantum in nature, but were instead a continuous fabric? Or would you discover something else, like that space and time weren’t quantum or that there was a fundamental “blurring” that prevented you from seeing below a specific scale?

Quantum, surprisingly to many, doesn’t necessarily mean it can be broken up into indivisible chunks. Space and time might not be discrete even if they’re quantum. Time to learn the difference.

The Science Of Why 5G Is (Almost) Certainly Safe For Humans

“Finally, the benefits that 5G will bring to society in the coming decade are truly revolutionary. In addition to the accelerated speeds that regular consumers will see, laying the infrastructure for 5G will enable civilization-changing smart technologies and a virtually unlimited number of device connections. 5G will enable blossoming technologies that rely on connectivity to the internet to go widespread, from connected self-driving cars to smart plugs, lights, cameras, toothbrushes, thermostats, healthcare monitoring devices and more. The Internet of Things is coming, and 5G is the technology that will take it mainstream.

There are lots of real hazards out there in the world, but 5G — much like vaccines, fluoridated drinking water, and the vapor trails left by airplanes — aren’t among them. In the search for truth, society should rely on the full suite of scientific evidence, rather than fear or ideology, to guide us. When we do, all of us can reap the benefits of a safe, connected world.”

Remember how big of a leap it was when we transitioned from 3G to 4G technologies? The jump from text and SMS messaging to streaming online video represented a factor of ~500 improvement in bandwidth, and the jump to 5G should not only give us an additional factor of 100, but should enable billions of additional connected devices. The Internet of Things is coming, and 5G is the technology that will bring it to fruition.

But is it safe for humans? Although there’s a lot of fearmongering and conspiracy theorizing surrounding it, there’s an awful lot of science, too. Here’s why it indicates that 5G is almost certainly safe for humans.

Everything we call real is made of things that cannot be regarded as real.

Niels Bohr

6 Steps Everyone Can Take To Become An Ally In White, Male-Dominated Workplaces

Step 1: Listen to (women/people of color/URMs) when they discuss the problems they face. This is the first real step towards being an ally, and all it requires you do to is pay attention to the many voices out there — especially the voices of people whose experiences are vastly different from your own — and pay attention to them.

You’ll find lots of challenges that they talk about, and a myriad of ways that people are given the message that they are inadequate. This is a problem that practically everyone faces, but the degree of severity of this problem varies drastically among people of different races, genders, sexual orientations, religions, and ages. Many things that we think of as minor offenses if they only happen once or twice become unbearable, like death-by-a-thousand-papercuts, when they happen continually.”

So, you’ve chosen the field you want to go into, and it’s a field where your talents and interest both lie. You know you’re good enough to do it, but you know there are going to be formidable obstacles and challenges to overcome. If that field happens to be dominated by white men (the dominant culture in many STEM fields), and you yourself aren’t a white man, you’re no doubt going to encounter obstacles and challenges that go above and beyond what you’d face if you were a white man.

You have a choice as far as how you behave in this environment, particularly if you yourself are a white man. If you’re interested in being an ally, you might find this essential reading.

This Is Why The Speed Of Gravity Must Equal The Speed Of Light

“In order to get different observers to agree on how gravitation works, there can be no such thing as absolute space, absolute time, or a signal that propagates at infinite speed. Instead, space and time must both be relative for different observers, and signals can only propagate at speeds that exactly equal the speed of light (if the propagating particle is massless) or at speeds that are blow the speed of light (if the particle has mass).

In order for this to work out, though, there has to be an additional effect to cancel out the problem of a non-zero tangential acceleration, which is induced by a finite speed of gravity. This phenomenon, known as gravitational aberration, is almost exactly cancelled by the fact that General Relativity also has velocity-dependent interactions. As the Earth moves through space, for example, it feels the force from the Sun change as it changes its position, the same way a boat traveling through the ocean will come down in a different position as it gets lifted up and lowered again by a passing wave.”

According to Newtonian gravity, space and time are absolute, and the gravitational force between any two objects is defined by the distance between them. In relativity, though, different observers don’t agree on distances, which means they won’t agree on forces, accelerations, or other properties of motion from a relativistic perspective. And yet, if you use Newton’s law of gravitation to compute the orbits of Solar System objects, it gets the right answer. If you instead tried to use Newton’s laws but allowed planets to be attracted to where the Sun was in the past, you’d get the wrong answer! Does this mean that the speed of gravity is infinite?

Hardly, but you have to dive deep into relativity to understand what else is up. Thankfully, we’ve done this, and you can enjoy the answer for yourself! Here’s why the speed of gravity must equal the speed of light.

For The Last Time, No, A NASA Engineer Has Not Broken Physics With An Impossible Engine

“The problem isn’t that these laws couldn’t be overturned by experiment; of course they could. The problem is that physicists have performed so many experiments in so many different ways, so carefully and with such precision verifying them. These conservation laws have been confirmed for every gravitational, mechanical, electromagnetic and quantum interaction ever observed, and they always hold. In every scenario ever examined, momentum, Lorentz invariance, and Newton’s 3rd law are always conserved.

And now, it’s claimed that an engine, one that relies on nothing more than a simple electromagnetic or mechanical power source, overthrows all of physics. Like cold fusion. Like the EM drive. Like any perpetual motion machine. Or, like the latest absurdity, David Burns’ helical engine.”

Every time a new story comes out about some idea or discovery that clearly violates a well-established law of physics, I’m quick to point out the flaws with it and to assert that this doesn’t and cannot work. I’m then quickly met with an army of non-physicists who claim that I’m too close-minded; that I’m not even open to the possibility of new technology; and that I’m not even giving it a fair shake.

On the contrary, explaining what we know about physics and how we know it, in the context of what’s been robustly established, is the fairest shake something can get. Physics is not broken, and the latest bad idea really is bad. Here’s why.


“What we observe as material bodies and forces are nothing but shapes and variations in the structure of space.”

— Erwin Schrödinger (via mysteriousquantumphysics)