This Is Why Scientists Will Never Exactly Solve General Relativity
“One of the most valuable lessons I ever got in my life came during the first day of my first college math class on differential equations. The professor told us, “Most of the differential equations that exist cannot be solved. And most of the differential equations that can be solved cannot be solved by you.” This is exactly what General Relativity is — a series of coupled differential equations — and the difficulty that it presents to all those who study it.
We cannot even write down the Einstein field equations that describe most spacetimes or most Universes we can imagine. Most of the ones we can write down cannot be solved. And most of the ones that can be solved cannot be solved by me, you, or anyone. But still, we can make approximations that allow us to extract some meaningful predictions and descriptions. In the grand scheme of the cosmos, that’s as close as anyone’s ever gotten to figuring it all out, but there’s still much farther to go. May we never give up until we get there.”
In our best theory of gravity, General Relativity, we can compute to arbitrary accuracy the effects on matter of any spacetime that we can write down. Unfortunately, most of the spacetimes that we can dream up in our head aren’t ones that we can write down, and most of the ones that we can write down can only be solved approximately, not exactly.
This is not a flaw nor a benefit: it is simply a property of the theory that we have. Is it the final answer? Perhaps not. But it’s the best one we’ve got so far. Here’s what it means.
Sorry Science Fans, Discovering A 70-Solar-Mass Black Hole Is Routine, Not Impossible
“Astronomers aren’t perplexed by this object (or similar ones to it) at all, but rather are fascinated with uncovering the details of how they formed and how common they truly are. The mystery isn’t why these objects exist at all, but rather how the Universe makes them in the abundances we observe. We don’t falsely generate excitement by spreading misinformation that diminishes our knowledge and ideas prior to this discovery.
In science, the ultimate rush comes from discovering something that furthers our understanding of the Universe within the context of everything else we know. May we never be tempted to pretend anything else is the case.”
Did you hear about this “impossible” black hole that “perplexes” astronomers and “defies” theory? If you followed the news cycle last week, that’s probably what you’ve heard. But the truth is far more interesting, and includes facts like:
-this is the fourth black hole we’ve found like it, not the first,
-there are two other ways to make black holes that would explain this object in addition to the one way that can’t,
-and that we’ve seen each and every one of the steps necessary to make a black hole like this,
-but that finding this black hole with this particular method really is revolutionary?
As always, the real science is far more interesting than the mangled hype you’ve seen before. This black hole doesn’t defy theory, but sure does teach us a lot. Come get the real story today.
These Are The Top 10 Hubble Images Of 2019
“1.) Galaxy pair AM 2026-424. With two massive galaxies colliding head-on, an intermediate ring of blue stars appears before the inevitable final merger.”
In 1990, the Hubble Space Telescope was launched, providing humanity with unprecedented views of the Universe. Each and every year, with 2019 marking the 30th consecutive year, a series of images get produced that shed light on some aspect of our Universe in unprecedented fashion. Despite Hubble’s big gyroscope failure (and scare) at the end of last year, 2019 has turned out to be no exception, with 10 spectacular new images and 7 almost-as-spectacular honorable mentions.
There’s a great chance you missed most of these during the year, but now’s your opportunity to get the year’s Hubble highlights all in one place!
Ask Ethan: Was The Critical Evidence For The Big Bang Discovered By Accident?
“The cosmic microwave background is a landmark evidence of the Big Bang origin of the universe. How come this discovery is labelled as an accidental one?”
Imagine that you lived in a world where nobody knew where the Universe came from. Sure, different theories led to a myriad of possibilities, but it takes observations to decide what’s correct in this Universe. In the 1920s, Georges Lemaitre worked out the first early details of the Universe originating from a hot, dense state. In the 1940s, George Gamow and his collaborators started to pull out robust predictions, like the nuclear predictions for fusion in the early Universe, the growth of stars, galaxies and clusters in the Universe, and the existence and rudimentary properties of a leftover glow: today’s Cosmic Microwave Background. Yet the actual discovery of this leftover radiation from the Big Bang, despite the meticulous planning of a group working to detect it explicitly, truly was a serendipitous accident.
You’ll never look at the expression “one astronomer’s noise is another astronomer’s data” the same way again!
Your 2019 Holiday Gift Guide For Space, Astronomy, And Science Lovers
“At The Edge Of Time, by Dan Hooper. This new book, out just a few weeks ago, is my favorite new science book of 2019. As a theoretical cosmologist, Dan is all the things I appreciate in a scientist who writes about his own research: he’s knowledgeable, comprehensive, and careful to get the details right. He has clear opinions and preferences, but is willing and able to push them aside in service of teaching the reader about the strengths and weaknesses of a variety of perspectives on a myriad of issues at the frontiers of physics.
If you’re mystified and curious about the mysteries of the Universe, including dark matter, dark energy, and cosmic inflation, and want a unique take on all of these puzzles with a peek behind how science-in-action works, you won’t want to miss this book. (I liked it so much that Dan is going to be my next upcoming guest on the Starts With A Bang podcast!)”
Do you love space, science, astronomy, physics, the Moon, and learning about the frontiers of what we know? Well, the holidays are coming up (today is Black Friday), and if that describes you or someone close to you in your life, here is a complete gift guide for the science enthusiast in your life.
With a total of 11 recommended books, a wall calendar, hats, accessories, and even a unique puzzle, you won’t want to miss this holiday gift guide!
Why Humans Should Be Thankful That Our Universe Has Dark Matter
“In a Universe without dark matter, we might still have stars and galaxies, but the only planets would be gas giant worlds, with no rocky ones to speak of. Without carbon, there are no organic molecules; without oxygen, there is no liquid water; without a whole slew of elements from the periodic table, biochemical life would be completely impossible.
Only with the presence of massive dark matter halos, surrounding galaxies and driving the growth of the cosmic web, can a planet like Earth or carbon-based life like we find terrestrially be formed. As we’ve come to understand what makes up our Universe and how it grew to be this way, one inescapable conclusion emerges: dark matter is fundamentally necessary for life to arise. Without it, the chemistry that underlies all life could never have occurred. Today and every day, we should be thankful for every part of the cosmic story that allowed us to exist. Even dark matter.”
Today marks American Thanksgiving, a holiday where we give thanks for all the positive things that have impacted our lives and the bountiful harvest that nature provides in order for us to survive through the harsh winters. But one of the things that’s not only unappreciated, but often derided in the popular media is dark matter, a substance which interacts gravitationally but not through any other known force.
Yet, without dark matter, humans, chemical-based life, or even rocky planets wouldn’t be able to exist in our Universe. Here’s why you, and everyone, should be thankful for it.
This Is Why We Can’t Just Do All Of Our Astronomy From Space
“There’s no doubt that going to space provides humanity with a window on the Universe that we’d never get to exploit if we remained on Earth. The sharp, narrow-field images we can construct are incomparable, and as we move into the next generation of space-based observatories like Athena, James Webb, WFIRST and (maybe) even LUVOIR, we’ll answer many of today’s mysteries concerning the nature of the Universe.
Yet there are some scientific tasks that are far better suited to ground-based astronomy than space-based astronomy. In particular, deep spectroscopic imaging of distant targets, direct exoplanet studies, identification of potentially hazardous objects, hunting for objects in the outer Solar System (like Planet Nine), all-sky surveys for variable objects, interferometry studies and much more are all superior from the ground. Losing the benefits of ground-based astronomy would be both catastrophic and unnecessary, as even a small effort can prevent it. But if we continue to be reckless and careless with our skies — two all-too-human traits — they’ll disappear, along with ground-based astronomy, before we know it.”
So, you don’t care of we lose ground-based astronomy, because astronomy from space is better anyway? I bet you don’t even know what we’ll lose if we lose ground-based astronomy.
Because it’s substantial, it’s irreplaceable, and if you’re going to allow it to slip away, you’d better know what we’re losing.
This Is Why The ‘X17’ Particle And A New, Fifth Force Probably Don’t Exist
“You cannot be afraid to make a mistake in science, but you must be aware that mistakes are common, can come from unexpected sources, and — as a responsible scientist — our job is not to sensationalize our most wishful thinking about what might be true, but to subject it to the most careful, skeptical scrutiny we can muster. Only with that mindset can we responsibly take a look at the experimental evidence in question.
If we want to give these new results a proper analysis, we need to make sure we’re asking the right questions. How was the experiment set up? What was the raw data? How was the analysis of the data performed? Was it verified independently? Is this data consistent with all the other data we’ve taken? What are the plausible theoretical interpretations, and how confident are we they’re correct? And finally, if it all holds up, how can we verify whether this really is a new particle with a new force?”
If you’ve been around the particle physics block before, there’s a lesson you should have learned by now: your default assumption should be that the Standard Model is correct. If an experiment contradicts what the Standard Model predicts, you should immediately be spending your energy wondering what’s wrong with the experiment, not leaping to fantastic, speculative conclusions about all of physics being wrong.
What should you make about the Atomki Anomaly, the X17 particle, and the idea of a new, fundamental force? To say “be skeptical” is a gross understatement. Get the story today.
Spectacular Planetary And Lunar Alignment To Grace The Post-Sunset Thanksgiving Skies
“As 2019 has progressed, Saturn has followed Jupiter in its sky-crossing migration from east to west. Meanwhile, for about the past month, Venus has emerged as an evening star after sunset, drifting from west to east. On Sunday, November 24, Venus and Jupiter nearly met — achieving a conjunction — coming within 1.4° of each other.”
Normally, astronomical conjunctions are a big and spectacular deal, especially when they’re close, and particularly when they’re between the two brightest planets of all: Venus and Jupiter. But on American Thanksgiving, November 28, an extraordinary and unusual event will occur: the young crescent Moon will align with Venus and Jupiter as well, fresh off a conjunction. While skywatchers worldwide will get a spectacular show, the best views come for people in European and African longitudes, as they’ll see the Moon appear between closely spaced Venus and Jupiter.
This rare sight will only last for that one night, so make sure you know where to look and what to look for, because it’s your last chance to experience it for years!
Ask Ethan: Could The Shape Of Our Universe Be Closed Instead Of Flat?
“I thought that the curvature parameter had been essentially settled upon by WMAP, Planck, and other astronomical measurements. I am curious what you think about the validity of this recent paper. Is the Universe actually closed with a detectable positive curvature as the authors of the Nature Astronomy paper suggest? If the Universe is spherical, then how big would the sphere be according their measurements?”
About 2 weeks ago, a team of scientists took a detailed look at the latest Planck results, the most sophisticated, highest-precision map of the Cosmic Microwave Background ever obtained. But rather than look simply at the temperature fluctuations, they looked at a different signal: the effect of gravitational lensing. And instead of finding the flat Universe that other types of analysis yield, they favored a closed, positively-curved Universe at about the 4.4% level, creating a greater-than-3-sigma tension with the rest of the Planck data.
Does that mean the Universe could be closed instead of flat? Not if you look at the consequences of this dastardly interpretation. Get the real science on Ask Ethan today.