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PBS Space Time
What Caused the Big Bang?
PBS Member Stations rely on viewers like you. To support your local station, go to: http://to.pbs.org/DonateSPACE ↓ More info below ↓ Uploaded 06-08-19 Check out the new Space Time Merch Store! https://pbsspacetime.com/ Support Space Time on Patreon https://www.patreon.com/pbsspacetime Every astronomy textbook tells us that soon after the Big Bang, there was a period of exponentially accelerating expansion called cosmic inflation. In a tiny fraction of a second, inflationary expansion multiplied the size of the universe by a larger factor than in the following 13 and a half billion years of regular expansion. This story seems like a bit of a … stretch. Is there really any mechanism that could cause something like this to happen? What what we’re covering today – the real physics of cosmic inflation. Hosted by Matt O'Dowd Written by Matt O'Dowd Graphics by Leonardo Scholzer Directed by Andrew Kornhaber Produced By: Kornhaber Brown Dark Energy Playlist: https://www.youtube.com/playlist?list=PLsPUh22kYmNA6WUmOsEEi32zi_RdSUF4i The Quantum Vacuum and Hawking Radiation Playlist https://www.youtube.com/watch?v=OvgZqGxF3eo&list=PLsPUh22kYmNAHB1W2_Ka2F83sObdczwKr Most cosmologists buy some variation of the inflation hypothesis. It seems to very neatly solve some of the biggest questions in cosmology. Those being: why is matter and energy so smoothly spread out across the entire observable universe? And why is the geometry of the universe so flat? Neither should be expected unless the universe expanded much more rapidly early on. We explored these problems in an earlier video – worth a look if you really want to get inflation. Another problem fixed by inflation is the absence of magnetic monopoles – strange particles predicted to have been produced in the early universe. We’ll come back to those another time. Big Bang Supporters: Anton Lifshits David Nicklas Fabrice Eap Juan Benet Justin Lloyd Morgan Hough Quasar Supporters: Mark Heising Mark Rosenthal Tambe Barsbay Vinnie Falco Hypernova Supporters: Chuck Zegar Danton Spivey Donal Botkin Edmund Fokschaner Hank S John Hofmann John R. Slavik Jordan Young Joseph Salomone kkm Mark Heising Matthew Matthew O'Connor Syed Ansar Gamma Ray Burst Supporters: Adrien Hatch Alexey Eromenko Andreas Nautsch Bradley Jenkins Brandon Labonte Carlo Mogavero Daniel Lyons David Behtala DFaulk Dustan Jones Geoffrey Short James Flowers James Quintero John Funai John Pollock Jonah Jonathan Nesfeder Joseph Dillman Joseph Emison Josh Thomas Kevin Warne Kyle Hofer Malte Ubl Mark Vasile Nathan Hitchings Nick Virtue Paul Rose Ryan Jones Scott Gossett Sigurd Ruud Frivik Tim Jones Tim Stephani Tommy Mogensen Yurii Konovaliuk سلطان الخليفي Learn more about your ad choices. Visit megaphone.fm/adchoices Learn more about your ad choices. Visit megaphone.fm/adchoices
Today · 17 min
Espresso
La contaminación lumínica no borra las galaxias
Este es el episodio 219 del podcast Espresso de @nestor, publicado el 15 de noviembre de 2026. Puedes dejar comentarios de texto y audio en este enlace. Cuando observamos desde ciudad, desde área metropolitana, pues a veces parece que las galaxias y las nebulosas simplemente se han ido, ¿no? Han desaparecido. No es exactamente eso. La luz sigue llegando. La cosa está en que el fondo del cielo se ha vuelto demasiado brillante. La luz artificial se dispersa en la atmósfera y crea un resplandor que, bueno, eleva el brillo de fondo. Cuanto más brillante es ese fondo, menos contraste queda entre él y los objetos débiles que intentamos observar Y eso explica algo que puede resultar desconcertante en un principio Una galaxia puede tener una magnitud suficientemente brillante sobre el papel Y sin embargo, pues ser casi invisible desde un cielo urbano Y no es que falte luz procedente de la galaxia Sino que esa luz está repartida sobre una superficie extensa y tiene que competir con un fondo ya iluminado Sin embargo una estrella de magnitud similar concentra casi toda su luz en un punto y puede seguir destacando con bastante facilidad Por eso la contaminaci lum afecta especialmente a galaxias a nebulosas y a cualquier objeto de bajo brillo superficial Y tambi explica por qu un cielo oscuro puede mejorar tanto la observaci sin cambiar de telescopio El objeto no se vuelve m brillante de repente lo que se vuelve m oscuro es el fondo y al bajar ese fondo pues recuperamos contraste trasladar un mismo telescopio desde un entorno urbano a un cielo rural pues produce una mejora más grande de la que obtendríamos simplemente aumentando unos centímetros de abertura si movemos si permanecemos en el mismo lugar por eso en cielo profundo el lugar de observación Pero tampoco toda contaminaci lum es igual La luz directa cerca del observador puede arruinar la adaptaci visual Un resplandor de n urbanos en el horizonte puede afectar mucho a los objetos bajos y bastante menos a los que est cerca del zenith Y una noche h o con part en suspensi puede empeorar todav m el problema porque esa luz artificial se dispersa con mayor facilidad tiene muchas partículas en suspensión, lo que decíamos, en las que rebotar. También conviene recordar que los filtros no hacen milagros. Los célebres filtros UHC o Oxígeno 3 pueden mejorar mucho el contraste de determinadas nebulosas de emisión porque deja pasar unas longitudes de onda y bloquea otras, pero no sirve, por ejemplo, para una galaxia. La galaxia emite luz en un espectro bastante amplio Así que si filtramos buena parte de esa luz artificial también estamos eliminando parte de la luz que queremos observar Y nos quedamos igual que est o peor todav Por eso no existe un filtro capaz de convertir un cielo urbano en un cielo oscuro La mejor manera de luchar bueno la mejor herramienta ser mejor decir para luchar contra la contaminaci lum sigue siendo cuando es posible alejarse de ella Pero hay más, cuando llegamos por primera vez a un cielo realmente oscuro solemos decir que se ven más estrellas, es verdad, pero para quien observa cielo profundo lo más importante no siempre es eso, lo importante es que el cielo entre esas estrellas se haya oscurecido y entonces empiezan a aparecer cosas que ya estaban allí. Galaxias nebulosas, extensiones débiles, estructuras internas que desde un cielo brillante se confundían con el fondo. La contaminación lumínica no apaga esos objetos, lo que hace es esconderlos dentro de un cielo que hemos hecho demasiado brillante. Y por eso mejorar la observación no siempre consiste en recoger más luz, consiste en recuperar la oscuridad alrededor de ella.
Today · 4 min
PBS Space Time
Are You a Boltzmann Brain?
Viewers like you help make PBS (Thank you 😃) . Support your local PBS Member Station here: https://to.pbs.org/DonateSPACE Uploaded 26-04-17 Was an incredible drop in entropy responsible for the Big Bang? If that’s the case, this would lead us to conclude that a great many other things are possible, including the likelihood that you are a Boltzmann Brain. Try The Great Courses Plus at http://ow.ly/4anY30acloO You can further support us on Patreon at https://www.patreon.com/pbsspacetime Get your own Space Time tshirt at http://bit.ly/1QlzoBi Tweet at us! @pbsspacetime Facebook: facebook.com/pbsspacetime Email us! pbsspacetime [at] gmail [dot] com Comment on Reddit: http://www.reddit.com/r/pbsspacetime Help translate our videos! https://www.youtube.com/timedtext_cs_panel?tab=2&c=UC7_gcs09iThXybpVgjHZ_7g Previous Episode: The Oh My God Particle https://www.youtube.com/watch?v=osvOr5wbkUw The second Law of Thermodynamics tells us that everything moves towards a state of greater entropy, but it is low entropy that enables galaxies, stars, planets and human beings. The lowest entropy state that we’re aware of in our universe was right before the Big Bang. The entirety of our own universe was condensed to a microscopic size. What caused this extreme low entropy? If it was caused by a random fluctuation in particles that implies that a great many other things are possible due to the random fluctuations of particles. One of the strangest of those possibilities is that of the Boltzmann Brain. If the Big Bang was caused by random entropic fluctuations then it is much more likely you are a Boltzmann Brain than that you are a human being. Written and Hosted by Matt O’Dowd Produced by Rusty Ward Graphics by Kurt Ross Made by Kornhaber Brown (www.kornhaberbrown.com) The Great Courses Plus is currently available to watch through a web browser to almost anyone in the world and optimized for the US market. The Great Courses Plus is currently working to both optimize the product globally and accept credit card payments globally. Special thanks to our Patreon Big Bang, Quasar and Hypernova Supporters: Big Bang Shane Robinson David Nicklas Samuel Dean Jacintho Quasar Tambe Barsbay Luna IT Solutions Coolascats Avan and Kyan Griggs Max Levine Hypernova Science Via Markets Chuck Zegar Craig Peterson Jordan Young Ratfeast John Hofmann Thanks to our Patreon Gamma Ray Burst Supporters: Justin Lloyd Conor Dillon Jared Moore Michal-Peanut Karmi Bernardo Higuera Erik Stein Daniel Lyons Jade Bilkey Kevin Warne JJ Bagnell J Rejc Dylan Merida Amy Jie Anthony Caridi Avi Goldfinger John Pettit Shannan Catalano Florian Stinglmayr Yubo Du Benoit Pagé-Guitard Ronny Polonia Nathan Leniz Jessica Fraley Kirk Mathews Loro Lukic Carl P. Corliss Brandon labonte David Crane Greg Weiss Eric Jackson Learn more about your ad choices. Visit megaphone.fm/adchoices Learn more about your ad choices. Visit megaphone.fm/adchoices
Today · 15 min
Sleepy Facts About the Universe
How Does a Collapsing Star Core Produce an Explosion? - The Hidden Collapse Before a Supernova | Sleepy Facts About the Universe
Got something to say to this podcast? Send a voicemail, and you might hear yourself on the next episode! When we picture a supernova, we usually imagine a star suddenly brightening and exploding outward. But the visible blast is actually a delayed announcement. The real catastrophe happens deep inside the star in less time than it takes to draw a breath, hidden entirely from view. This episode examines the final seconds of a massive star, exploring how an iron core collapses at a significant fraction of the speed of light, reaches the density of an atomic nucleus, and rebounds to launch a shock wave. The journey from this hidden collapse to a visible explosion is remarkably complex. The shock wave immediately loses energy to nuclear demolition and escaping neutrinos, often stalling completely before turbulent convection and neutrino heating can revive it. Because photons remain trapped in the dense stellar envelope, the only signal to escape immediately is a burst of neutrinos. This exact sequence was confirmed in 1987 when detectors recorded neutrinos from a supernova in the Large Magellanic Cloud hours before the first visible light arrived. I wanted to understand why the bright spectacle we see is just a minor fraction of the total energy released, and how an event can be completely finished in the core before we even know it has begun. Some questions sound simple until you try to answer them, and the mismatch between the internal collapse and the delayed visible arrival completely changes how I think about dying stars.
Today · 26 min