from the world's big
How to make a black hole
Here's the science of black holes, from supermassive monsters to ones the size of ping-pong balls.
Dr. Michelle Thaller is an astronomer who studies binary stars and the life cycles of stars. She is Assistant Director of Science Communication at NASA. She went to college at Harvard University, completed a post-doctoral research fellowship at the California Institute of Technology (Caltech) in Pasadena, Calif. then started working for the Jet Propulsion Laboratory's (JPL) Spitzer Space Telescope. After a hugely successful mission, she moved on to NASA's Goddard Space Flight Center (GSFC), in the Washington D.C. area. In her off-hours often puts on about 30lbs of Elizabethan garb and performs intricate Renaissance dances. For more information, visit NASA.
MICHELLE THALLER: So Mark, you have a great question about black holes: Is there a minimum mass needed for a black hole to form and does a black hole form whenever a stellar object gets that dense?
To begin with, let's talk about the definition of a black hole. Now, most commonly people talk about black holes as being a consequence of a giant star dying. And the idea is that a star has this huge mass and that's a lot of gravity crushing the star together. Now, when the star is alive and there are fusion reactions going on inside the core, that crush of gravity is actually held up. But once the star dies and the fusion reactions go away the gravity crushes inward and there's nothing to support it anymore. So basically gravity becomes so strong in that object that not even light can escape and therefore we call it a black hole. That's probably the most classic way to make a black hole, is you actually make it from the core of a dead star that's collapsing.
But you might be surprised to learn that we actually think there are other ways to make a black hole. And the real answer to your question is that there is no minimum mass needed for a black hole, you just need to have the right density for an object's gravity to be so intense that light can't escape. The universe is very good at making black holes that are about the size of stars; it's an easy way to get them. But the universe makes black holes in other ways too. We actually think there are black holes being generated all around us on very, very small scales. There are things called high-energy cosmic rays — very, very energetic particles that slam into our atmosphere from space. These slam in with enough energy that we think they actually create tiny black holes, black holes that have the mass only a couple of atoms. There's enough energy to cram that matter together so much they form little black holes.
One of the things that we're doing at CERN, which is actually the largest particle accelerator on the earth right now, is trying to get up to those densities. CERN actually does want to make artificial black holes. Actually have two particles collide so intensely that they pop off a little black hole. And before you ask the question — no this is not dangerous. CERN does not get up to energies anywhere near what's happening in the natural world. These high-energy particles from space are much more energetic than CERN could ever do. So if anything dangerous was going to happen, it would already have happened. These tiny little black holes we think don't live very long, maybe even a millionth of a second. The whole point will be to detect them at all. All you need is a certain amount of mass and a certain amount of volume. It doesn't matter how much mass and you'll get a black hole. For example, if you could actually crush the entire Earth into the size of a ping-pong ball that would be a black hole.
But now let me tell you that things go the other way too. We know black holes that are much, much more massive than stars. There are things called supermassive black holes that are millions or billions of times the mass of the Sun. We see these in the center of galaxies all around us. And quite honestly, one of the biggest questions in astronomy right now is how do these giant black holes form? Because we see them so far away in space, we see them in galaxies that are 10 billion light years away and that means that 10 billion years ago when the universe wasn't very old you already had black holes that were billions of times the mass of the Sun.
Now, those supermassive black holes are really interesting because remember I told you the whole point is getting the right density for a black hole. It doesn't really matter how much matter there is. Intriguingly these giant black holes are actually not very dense, on average. If you had a black hole that was about 4 million times the mass of the Sun, the diameter of that black hole would be about the orbit of where Jupiter is in our solar system and the average density of it, across that whole volume, would be about the same as water.
So how is it that you could have a black hole that only has the average density of water? Aren't black holes extremely dense things? Well, this all depends on the amount of mass that you have. So if the Earth were a black hole, you would have to take all of the Earth and crush it to the size of a ping-pong ball — think about how dense that would be. That would actually be on the order of a sextillion tones within a cubic centimeter — really, really dense.
For these really massive black holes you have a lot more mass and that means you don't actually need the density to bend space quite as much. One of the ways I can explain this is to use an analogy. Say that you have a rubber sheet and in order to get a black hole you have to make the bending of the rubber really, really extreme, you have to drop something onto the rubber sheet that would bend it down. So maybe you have something that's just the size of a marble and in order to get a really good strong bend in that sheet it has to be the density of lead, really dense. Now say you have something big like an elephant. You put the elephant on the rubber sheet you get a lot of bending even though the elephant is, on average, a lot less dense than lead. So if you have more matter it will create a bending of space even if it's not very dense. And amazingly that does mean that the biggest black holes in the universe have the average density of air.
- There's more than one way to make a black hole, says NASA's Michelle Thaller. They're not always formed from dead stars. For example, there are teeny tiny black holes all around us, the result of high-energy cosmic rays slamming into our atmosphere with enough force to cram matter together so densely that no light can escape.
- CERN is trying to create artificial black holes right now, but don't worry, it's not dangerous. Scientists there are attempting to smash two particles together with such intensity that it creates a black hole that would live for just a millionth of a second.
- Thaller uses a brilliant analogy involving a rubber sheet, a marble, and an elephant to explain why different black holes have varying densities. Watch and learn!
- Bonus fact: If the Earth became a black hole, it would be crushed to the size of a ping-pong ball.
Are we genetically inclined for superstition or just fearful of the truth?
- From secret societies to faked moon landings, one thing that humanity seems to have an endless supply of is conspiracy theories. In this compilation, physicist Michio Kaku, science communicator Bill Nye, psychologist Sarah Rose Cavanagh, skeptic Michael Shermer, and actor and playwright John Cameron Mitchell consider the nature of truth and why some groups believe the things they do.
- "I think there's a gene for superstition, a gene for hearsay, a gene for magic, a gene for magical thinking," argues Kaku. The theoretical physicist says that science goes against "natural thinking," and that the superstition gene persists because, one out of ten times, it actually worked and saved us.
- Other theories shared include the idea of cognitive dissonance, the dangerous power of fear to inhibit critical thinking, and Hollywood's romanticization of conspiracies. Because conspiracy theories are so diverse and multifaceted, combating them has not been an easy task for science.
A growing body of research suggests COVID-19 can cause serious neurological problems.
- The new study seeks to track the health of 50,000 people who have tested positive for COVID-19.
- The study aims to explore whether the disease causes cognitive impairment and other conditions.
- Recent research suggests that COVID-19 can, directly or indirectly, cause brain dysfunction, strokes, nerve damage and other neurological problems.
Brain images of a patient with acute demyelinating encephalomyelitis.
COVID-19 and the brain<p>A growing body of research reveals alarming neurological complications among COVID-19 patients. On Wednesday, for example, researchers from University College London published a <a href="https://academic.oup.com/brain/article/doi/10.1093/brain/awaa240/5868408" target="_blank">study</a> in the journal Brain that describes how some patients have suffered temporary brain dysfunction, strokes, nerve damage, and other neurological problems concurrent with COVID-19.</p><p>Some patients suffered brain inflammation as a result of a rare disease called acute disseminated encephalomyelitis, which can cause numbness, seizures, and confusion. One patient in the study even hallucinated monkeys and lions in her home.</p>
Photo by Mario Tama/Getty Images<p>A separate study published in the <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7198407/" target="_blank">Journal of Clinical Neuroscience</a> notes that some COVID-19 patients have also suffered neurological complications like impaired consciousness and acute cerebrovascular disease. The study notes that past viruses like MERS and SARS also seemed to cause neurological problems.</p><p>A troubling finding among this growing body of research is that some patients seem to suffer neurological damage even when respiratory symptoms aren't obvious. Additionally, scientists aren't sure whether damage from the disease will be permanent.</p><p style="margin-left: 20px;">"Given that the disease has only been around for a matter of months, we might not yet know what long-term damage COVID-19 can cause," Dr. Ross Paterson, joint first author of the University College London study, said in a <a href="https://www.eurekalert.org/pub_releases/2020-07/ucl-iid070620.php" target="_blank">press release</a>. "Doctors needs to be aware of possible neurological effects, as early diagnosis can improve patient outcomes."</p><p>If you've been diagnosed with COVID-19 and want to enroll in the study, visit <a href="https://www.cambridgebrainsciences.com/studies/covid-brain-study" target="_blank">cambridgebrainsciences.com/studies/covid-brain-study</a>.</p>
Construction of the $500 billion dollar tech city-state of the future is moving ahead.
- The futuristic megacity Neom is being built in Saudi Arabia.
- The city will be fully automated, leading in health, education and quality of life.
- It will feature an artificial moon, cloud seeding, robotic gladiators and flying taxis.
The Red Sea area where Neom will be built:
Saudi Arabia Plans Futuristic City, "Neom" (Full Promotional Video)<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="c646d528d230c1bf66c75422bc4ccf6f"><iframe type="lazy-iframe" data-runner-src="https://www.youtube.com/embed/N53DzL3_BHA?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span>
Coronavirus layoffs are a glimpse into our automated future. We need to build better education opportunities now so Americans can find work in the economy of tomorrow.
- Outplacement is an underperforming $5 billion dollar industry. A new non-profit coalition by SkillUp intends to disrupt it.
- More and more Americans will be laid off in years to come due to automation. Those people need to reorient their career paths and reskill in a way that protects their long-term livelihood.
- SkillUp brings together technology and service providers, education and training providers, hiring employers, worker outreach, and philanthropies to help people land in-demand jobs in high-growth industries.
Source: McKinsey Global Institute analysis [PDF]<p>Work in understanding the skills at the heart of the new digital economy is leading to novel assessments that allow individuals to prove mastery to faithfully represent their abilities—but also to give weight and stackability to the emerging ecosystem of micro-credentials that make education more seamless across time and education providers. And we are seeing the beginnings of a renewal in the liberal arts, focused on building human skills in affordable ways that are accessible to many more individuals and far more effective.</p><p>Amidst these dark times, there is much opportunity to refresh the nation's education and training solutions to support the success of individuals and society writ large.</p>