Advances Vs. Consequences: What Does The 21st Century Have In Store For Humanity?
“We now live in a time where the actions of a small group of people — whether through malicious or benign intentions — are capable of leading to global catastrophe. It’s not just climate change or the threat of nuclear war that hangs over us; it’s a slew of facts.
It matters that a mass extinction is occurring right now: we’re destroying this planet’s proverbial “book of life” before we’ve even read it.
It matters that computers are permeating ever-increasing facets of our life, as humanity’s recently rising electricity use (after a plateau earlier this decade) is almost entirely due to new computational uses, like cryptocurrencies and blockchain.
It matters that the population is greater than ever before, as managing and distributing the edible food and drinkable water we produce is a greater challenge than ever before.”
Do you like big, sweeping conversations that tackle the biggest existential questions facing our species today? Looking to the larger picture, of humanity’s future on Earth, scientist Martin Rees has written a book detailing the challenges facing our civilization in the 21st century, and is about to deliver a public lecture on the topic of navigating the course that could lead us into a true golden age… or to ruin.
I’ll be live-blogging the lecture with many thoughts to add, and I hope you’ll join me in enjoying it!
Astronomers Debate: How Many Habitable Planets Does Each Sun-Like Star Have?
“We know that there are between 200 billion and 400 billion stars in the Milky Way galaxy. About 20% of those stars are Sun-like, for about 40-to-80 billion Sun-like stars in our galaxy. There are very likely billions of Earth-sized worlds orbiting those stars with the potential for the right conditions to have liquid water on their surfaces and being otherwise Earth-like, but whether that’s 1 or 2 billion or 50 or 100 billion is still unknown. Future planet-finding and exploring missions will need better answers than we presently have today, and that’s all the more reason to keep looking with every tool in our arsenal.”
Most of the time, in science, the quality of our data drives the size of our uncertainties. When we have very little data and it’s only of poor quality, our uncertainties tend to be large; when we have lots of very good data, our uncertainties shrink. NASA’s Kepler mission has provided astronomers with an unprecedented suite of data on exoplanets, revealing thousands of new worlds beyond our Solar System. And yet, despite all it’s found, if you ask the simple question of “how many Earth-like planets orbit a typical Sun-like star,” answers disagree by a factor of 100: from about 1% of stars have them to there’s between 1 and 2 for each and every such star.
What’s the real story? Where do these uncertainties arise, and are they larger than they need to be? Come get the full story (and watch David Kipping’s video at the end) and find out!
One Cosmic Mystery Illuminates Another, As Fast Radio Burst Intercepts A Galactic Halo
“Although scientists have studied [Fast Radio Bursts] intensely since their discovery, their origins remain mysterious. Meanwhile, an estimated 2 trillion galaxies populate our observable Universe. With incredibly large distances for FRBs to traverse, each one risks passing through an intervening galaxy. Giving off multiple pulses of under 40 microseconds apiece, FRB 181112 became the first burst to intercept a galactic halo.”
Where do fast radio bursts come from? Recent studies have demonstrated that they’re associated with host galaxies, but we don’t understand how they work, why some of them repeat, or why the pulse durations are so variable.
What about galactic halos: how much gas is in them? What is the gas temperature, density, magnetization, etc.? These are big questions about galaxies in general that we don’t have a general picture of. If only there were some way to learn more.
How about luck? We got lucky, in November of 2018, when for the first time a fast radio burst passed through a foreground galaxy’s halo. What did we learn? Come get (and see) the full story!
Has Google Actually Achieved ‘Quantum Supremacy’ With Its New Quantum Computer?
“Instead of recording a 0 or 1 permanently as a bit, a qubit is a two-state quantum mechanical system, where the ground state represents 0 and the excited state represents 1. (For example, an electron can be spin up or spin down; a photon can be left-handed or right-handed in its polarization, etc.) When you prepare your system initally, as well as when you read out the final results, you’ll see only 0s and 1s for the values of qubits, just like with a classical computer and classical bits.
But unlike a classical computer, when you’re actually performing these computational operations, the qubit isn’t in a determinate state, but rather lives in a superposition of 0s and 1s: similar to the simultaneously part-dead and part-alive Schrodinger’s cat. It’s only when the computations are over, and you read out your final results, that you measure what the true end-state is.”
Approximately a week ago, a NASA website began hosting a paper by Google AI Quantum and collaborators entitled, “Quantum supremacy using a programmably superconducting processor,” that claimed to achieve the long-sought-after goal of Quantum Supremacy at last. But what does that mean? What did the Google team actually demonstrate, how did they do it, and what still remains to be done in order to achieve our dream of surpassing the practical limits of classical computers for solving actual, useful problems?
Luckily, I got my hands on a copy of the paper and got to interview some experts in quantum computing to find out the answer. If you want to know the real, scientific truth, dive on in!
The One Science Lesson Every American Adult Can Learn From Greta Thunberg
“It’s a free world and a free country, and no one can stop you from believing whatever you want. You can believe that vaccines cause autism, that the Earth is flat, that humans never walked on the Moon, and that global warming is a hoax. But if you believe any of those things, you are choosing an unsubstantiated and anti-science conspiracy that, when confronted with the actual evidence humanity possesses, doesn’t have a legitimate leg to stand on.
For decades, politicians have commanded scientists to stick to their science and not enter conversations about science and society. Yet we live in a world where some of the most powerful nations are governed by inherently anti-science attitudes. Science has already carried the day when it comes to global warming and climate change; now is the time to be an adult and address the real changes humanity has brought upon planet Earth.”
The climate really is changing, and humans really are the cause. Out of 28 nations surveyed, the denial of these two facts is greater in no other country than the United States: we are 28th out of 28 in this regard. The science has been non-controversial for more than 30 years, and the oldest climate model, at 52, is still completely valid and correct.
So why can’t we even admit that much to ourselves? Because there’s a lesson we haven’t learned. Greta Thunberg has, and it’s time for us all to get on board.
This One Thought Experiment Shows Why Special Relativity Isn’t The Full Story
“In Einstein’s initial formulation of General Relativity way back in 1916, he mentioned the gravitational redshift (and blueshift) of light as a necessary consequence of his new theory, and the third classical test, after the precession of Mercury’s perihelion (already known at the time) and the deflection of starlight by a gravitational source (discovered during a total solar eclipse in 1919).
Although a thought experiment is an extremely powerful tool, practical experiments didn’t catch up until 1959, where the Pound-Rebka experiment finally measured a gravitational redshift/blueshift directly. Yet just by invoking the idea that energy must be conserved, and a basic understanding of particle physics and gravitational fields, we can learn that light must change its frequency in a gravitational field.”
If a photon flies through space towards Earth, it must gain energy and become bluer in nature as it approaches Earth’s surface. This idea, of a gravitational redshift or blueshift, dictates how a photon must change in energy in the presence of a gravitational field. Yet this effect, which only exists in General Relativity, could have been predicted as soon as special relativity was discovered by one simple thought experiment: to consider a particle-antiparticle pair dropped from high above the surface of the Earth, but to let the annihilation occur at varying locations.
If you considered that, you’d immediately realize how special relativity was insufficient for describing our Universe! Come learn how to reason it out for yourself today!
Is The Universe Filled With Black Holes That Shouldn’t Exist?
“What about at the high end of the stellar mass range of black holes? It’s true that pair instability supernovae are real and are indeed a limiting factor, as they don’t produce black holes. However, there’s an entirely separate way to produce black holes that is not particularly well understood at this time: direct collapse.
Whenever you have a large enough collection of mass, whether it’s in the form of a cloud of gas or a star or anywhere in between, there’s a chance that it can form a black hole directly: collapse due to insufficient pressure to hold it up against gravitation. For many years, simulations predicted that black holes should spontaneously arise through this process, but observations failed to see a confirmation. Then, a few years ago, one came in an unlikely place, as the Hubble Space Telescope saw a 25 solar mass star simply “disappear” without a supernova or other cataclysm. The only explanation? Direct collapse.”
As far as our best theories are concerned, the Universe isn’t filled with black holes of all different masses. Instead, the black holes that the Universe forms are inextricably linked to the processes by which the Universe makes the objects that then become black holes. From stars, there’s a theoretical lower limit of about 5 solar masses, and yet we saw a black hole of about 3 solar masses get created. There should be an enormous drop in black hole frequency above about 50 solar masses, but LIGO may be about to challenge that. And even at the highest end, there should be an upper limit to the masses of supermassive black holes, but a few of the ones we’ve found challenge that limit, too.
Does this mean the Universe is filled with black holes that shouldn’t exist? Or does it simply mean that we need superior models? Get the full story today.
This Is What The Milky Way’s Magnetic Field Looks Like
“The Milky Way’s gas, dust, stars and more create fascinating, measurable structures. Subtracting out all the foregrounds yields the cosmic background signal, which possesses tiny temperature imperfections. But the galactic foreground isn’t useless; it’s a map unto itself. All background light gets polarized by these foregrounds, enabling the reconstruction of our galaxy’s magnetic field.”
Have you ever wondered what our galaxy’s magnetic field looks like? As long as we restrict ourselves to looking in the type of light that human eyes can see, the optical portion of the spectrum, we’re extremely limited as far as what we can infer. However, if we move on to data from the microwave portion of the spectrum, and in particular we look at the data that comes from the polarization of background light (and the foreground light directly), we should be able to reconstruct our galaxy’s magnetic fields to the best precision ever. The Planck satellite, in addition to mapping the CMB to better precision than ever before, has enabled us to do exactly that.
Even though there are still some small questions and uncertainties, you won’t want to miss these incredible pictures that showcase just how far we’ve come!
Ask Ethan: Why Are There Only Three Generations Of Particles?
“It is eminently possible that there are more particles out there than the Standard Model, as we know it, presently predicts. In fact, given all the components of the Universe that aren’t accounted for in the Standard Model, from dark matter to dark energy to inflation to the origin of the matter-antimatter asymmetry, it’s practically unreasonable to conclude that there aren’t additional particles.
But if the additional particles fit into the structure of the Standard Model as an additional generation, there are tremendous constraints. They could not have been created in great abundance during the early Universe. None of them can be less massive than 45.6 GeV/c^2. And they could not imprint an observable signature on the cosmic microwave background or in the abundance of the light elements.
Experimental results are the way we learn about the Universe, but the way those results fit into our most successful theoretical frameworks is how we conclude what else does and doesn’t exist in our Universe. Unless a future accelerator result surprises us tremendously, three generations is all we get: no more, no less, and nobody knows why.”
There are three generations of (fermionic) particles in the Universe. In addition to the lightest quarks (up and down), the electron and positron, and the electron neutrino and anti-neutrino, there are two extra, heavy “copies” of this structure. The charm-and-strange quarks plus the top-and-bottom quarks fill the remaining generations of quarks, while the muon and muon neutrino and anti-neutrino plus the tau and tau neutrino and anti-neutrino comprise the next generation of leptons.
Theoretically, there’s nothing demanding three and only three generations, but experiments have shown that there are no more to within absurd constraints. Here’s the full story of how we know there are only three generations.
This Is Why We Don’t Shoot Earth’s Garbage Into The Sun
“Considering that the United States alone is storing about 60,000 tons of high-level nuclear waste, it would take approximately 8,600 Soyuz rockets to remove this waste from the Earth. Even if we could reduce the launch failure rate to an unprecedented 0.1%, it would cost approximately a trillion dollars and, with an estimated 9 launch failures to look forward to, would lead to over 60,000 pounds of hazardous waste being randomly redistributed across the Earth.
Unless we’re willing to pay an unprecedented cost and accept the near-certainty of catastrophic environmental pollution, we have to leave the idea of shooting our garbage into the Sun to the realm of science fiction and future hopeful technologies like space elevators. It’s undeniable that we’ve made quite the mess on planet Earth. Now, it’s up to us to figure out our own way out of it.”
As human beings continue to lead the technologically advanced lives we’re presently leading, we’re also producing waste of many different types. Biohazards, dangerous chemicals, nuclear waste and other pollutants must be kept out of drinking water, agricultural regions, the oceans, atmosphere, and away from populated areas. You might wonder why, now that we’re well into the space age, we haven’t considered shooting Earth’s most difficult-to-deal-with garbage into the Sun?
Well, we have considered it, and there are good reasons not to do it. If you’ve ever wondered why, you’ll really enjoy this read.