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	2022-11-09: What If Humanity Is Among The First Spacefaring Civilizations? 11:54: ... galaxy at 10% light speed, this delay will have basically no effect on cosmological ...
	2022-08-17: What If Dark Energy is a New Quantum Field? 01:25: ... model for dark energy is that it can be described with a so-called cosmological constant. This is just a static number that you can add to Einstein’s ... 03:22: Standard “cosmological constant” dark energy has omega -1. This is just what you get when you say that the vacuum has a constant energy density. 05:50: ... such a large number down to nearly zero but not quite zero. This is the cosmological constant problem, and we’ve discussed it ... 07:31: ... is yes, one could - and if that’s true then a lot of problems with cosmological constant dark energy could be solved. There are a few options for dark ... 09:51: ... solve some of the uncomfortable coincidences that seem necessary with a cosmological constant dark energy. Currently around 70% of the energy in the universe ... 10:55: ... able to form. This same “tracker” behavior could also help solve the cosmological constant problem. If quintessence shifts to match the matter fields, it ... 13:27: ... would be strong support for quintessence, because that would refute the cosmological constant model, and quintessence is its main competitor. The now fully ... 14:41: ... will teach us about its fabric, its origin, and its fate. Either the cosmological constant problem is coincidental with a quintessentially consistent dark ... 01:25: ... model for dark energy is that it can be described with a so-called cosmological constant. This is just a static number that you can add to Einstein’s equations of ... 03:22: Standard “cosmological constant” dark energy has omega -1. This is just what you get when you say that the vacuum has a constant energy density. 05:50: ... such a large number down to nearly zero but not quite zero. This is the cosmological constant problem, and we’ve discussed it ... 07:31: ... is yes, one could - and if that’s true then a lot of problems with cosmological constant dark energy could be solved. There are a few options for dark energy as ... 09:51: ... solve some of the uncomfortable coincidences that seem necessary with a cosmological constant dark energy. Currently around 70% of the energy in the universe is dark ... 10:55: ... able to form. This same “tracker” behavior could also help solve the cosmological constant problem. If quintessence shifts to match the matter fields, it could ... 13:27: ... would be strong support for quintessence, because that would refute the cosmological constant model, and quintessence is its main competitor. The now fully ... 14:41: ... will teach us about its fabric, its origin, and its fate. Either the cosmological constant problem is coincidental with a quintessentially consistent dark energy, ... 03:22: Standard “cosmological constant” dark energy has omega -1. This is just what you get when you say that the vacuum has a constant energy density. 07:31: ... is yes, one could - and if that’s true then a lot of problems with cosmological constant dark energy could be solved. There are a few options for dark energy as a new ... 09:51: ... solve some of the uncomfortable coincidences that seem necessary with a cosmological constant dark energy. Currently around 70% of the energy in the universe is dark ... 13:27: ... would be strong support for quintessence, because that would refute the cosmological constant model, and quintessence is its main competitor. The now fully operational James ... 05:50: ... such a large number down to nearly zero but not quite zero. This is the cosmological constant problem, and we’ve discussed it ... 10:55: ... able to form. This same “tracker” behavior could also help solve the cosmological constant problem. If quintessence shifts to match the matter fields, it could potentially ... 14:41: ... will teach us about its fabric, its origin, and its fate. Either the cosmological constant problem is coincidental with a quintessentially consistent dark energy, or ...
	2022-06-01: What If Physics IS NOT Describing Reality? 16:52: ... predicts that this should  happen. Also, we wouldn’t expect cosmological   redshift if matter is shrinking because there’s no  stretching of ...
	2022-05-25: The Evolution of the Modern Milky Way Galaxy 18:10: ... the Schwarzschild metric isn’t really valid in a universe with a cosmological constant.   There would indeed be an additional effect  ... 18:41: ... towards a black hole. In the same way, an  inertial frame at the cosmological event horizon   is flowing away from us at the speed of light. ... 18:10: ... the Schwarzschild metric isn’t really valid in a universe with a cosmological constant.   There would indeed be an additional effect  due to the tiny vacuum ... 18:41: ... towards a black hole. In the same way, an  inertial frame at the cosmological event horizon   is flowing away from us at the speed of light. ... 17:21: ... a kind of tug-of-war between the two?” Yes and no. First, assuming no cosmological  constant and dark energy, the expansion of   the universe does ...
	2022-04-20: Does the Universe Create Itself? 17:39: ... other black holes, etc - then it’s event horizon is the same size as our cosmological even horizon. Sounds too much of a coincidence, right? Well actually, this is ...
	2022-03-30: Could The Universe Be Inside A Black Hole? 02:09: This is the cosmological event horizon. 02:22: ... the accelerating expansion of the universe means the cosmological event horizon is closer to us than the spot where recession equals the ... 10:21: That’s the Cosmological Natural Selection idea by Lee Smolin, and yeah, we did an episode. 11:45: Cosmological natural selection might be a path to that, but we also need some evidence for that in order to proceed. 02:09: This is the cosmological event horizon. 02:22: ... the accelerating expansion of the universe means the cosmological event horizon is closer to us than the spot where recession equals the speed ... 02:09: This is the cosmological event horizon. 02:22: ... the accelerating expansion of the universe means the cosmological event horizon is closer to us than the spot where recession equals the speed of ... 10:21: That’s the Cosmological Natural Selection idea by Lee Smolin, and yeah, we did an episode. 11:45: Cosmological natural selection might be a path to that, but we also need some evidence for that in order to proceed. 10:21: That’s the Cosmological Natural Selection idea by Lee Smolin, and yeah, we did an episode. 11:45: Cosmological natural selection might be a path to that, but we also need some evidence for that in order to proceed.
	2022-03-23: Where Is The Center of The Universe? 01:04: This is called the Cosmological principle. 01:06: ... neither the Copernican principle nor the Cosmological principle are actual laws of physics - they’re philosophical positions - ... 11:28: He assumed a homogeneous universe and assumed the cosmological principle. 12:47: ... should point out that this doesn’t necessarily break the Cosmological principle because it could still be that our bubble is small on the most ... 01:04: This is called the Cosmological principle. 01:06: ... neither the Copernican principle nor the Cosmological principle are actual laws of physics - they’re philosophical positions - guiding ... 11:28: He assumed a homogeneous universe and assumed the cosmological principle. 12:47: ... should point out that this doesn’t necessarily break the Cosmological principle because it could still be that our bubble is small on the most ...
	2022-02-10: The Nature of Space and Time AMA 00:03: ... the same change in distance over time and uh as an example uh we have cosmological redshift okay so a photon of light traveling from one galaxy to the ...
	2022-01-19: How To Build The Universe in a Computer 05:26: ... example, in a cosmological simulation we’re trying to watch the detailed formation of individual ... 10:14: And then we have cosmological simulations  which create entire virtual universes, from the moment the first  atoms formed to the modern day. 10:39: ... the current largest cosmological simulations  is AbacusSummit, which just last year simulated 70 ... 05:26: ... example, in a cosmological simulation we’re trying to watch the detailed formation of individual galaxies, as ... 10:14: And then we have cosmological simulations  which create entire virtual universes, from the moment the first  atoms formed to the modern day. 10:39: ... the current largest cosmological simulations  is AbacusSummit, which just last year simulated 70 trillion particles on ...
	2021-11-10: What If Our Understanding of Gravity Is Wrong? 10:17: But the main problem with TeVeS  is cosmological in nature.
	2021-03-23: Zeno's Paradox & The Quantum Zeno Effect 14:04: We then use our cosmological models to predict what the expansion rate should be today.
	2021-03-16: The NEW Crisis in Cosmology 06:22: ... errors that are affecting one or both.   For example, the cosmological distance  ladder could have a broken rung. The   ...
	2020-07-28: What is a Theory of Everything: Livestream 00:00: ... does that number come from why are there three generations what's the cosmological constant telling us should those not be used as the as the occam's ...
	2020-06-15: What Happens After the Universe Ends? 10:41: ... by this sort of conformal rescaling, the universe needs a positive cosmological ...
	2020-04-28: Space Time Livestream: Ask Matt Anything 00:00: ... of just put this one up here because it was lying around the anthropic cosmological principle now this isn't we talked a lot about the cosmological ...
	2020-02-11: Are Axions Dark Matter? 14:39: ... that the universe is spatially finite. The simplest interpetation of the cosmological equations derived from general relativity tell us that it it may be ...
	2020-02-03: Are there Infinite Versions of You? 00:14: ... cosmological equations that so beautifully describe our universe make an ... 00:26: ... on itself and be finite, or perhaps the simplest interpretation of the cosmological equations is too ... 10:31: ... even then we still have to hope that it’s reasonable to extrapolate our cosmological equations ... 00:14: ... cosmological equations that so beautifully describe our universe make an uncomfortable ... 00:26: ... on itself and be finite, or perhaps the simplest interpretation of the cosmological equations is too ... 10:31: ... even then we still have to hope that it’s reasonable to extrapolate our cosmological equations ...
	2020-01-27: Hacking the Nature of Reality 12:27: ... Nima Arkani-Hamed and collaborators have performed what they call a cosmological bootstrap to understand the nature of those early subatomic scale ...
	2020-01-13: How To Capture Black Holes 11:59: ... couple of episodes, but today we're doing comments from our episode on cosmological natural selection - Lee Smolin's idea that maybe new universes are born ... 12:49: ... of the fundamental constants, not the origin of everything. Ideas like cosmological natural selection and eternal inflation are helpful because they reduce ... 13:26: ... average out? The answer to this is ... no one has any idea. The cosmological natural selection hypothesis doesn't really define the ongoing ... 14:13: ... to Lee Smolin. I'm making a list, guys. If it turns out the whole cosmological natural selection thing is true, I'll send that list to the Swedish ... 11:59: ... couple of episodes, but today we're doing comments from our episode on cosmological natural selection - Lee Smolin's idea that maybe new universes are born inside ... 12:49: ... of the fundamental constants, not the origin of everything. Ideas like cosmological natural selection and eternal inflation are helpful because they reduce the ... 13:26: ... average out? The answer to this is ... no one has any idea. The cosmological natural selection hypothesis doesn't really define the ongoing connection ... 14:13: ... to Lee Smolin. I'm making a list, guys. If it turns out the whole cosmological natural selection thing is true, I'll send that list to the Swedish Academy of ... 11:59: ... couple of episodes, but today we're doing comments from our episode on cosmological natural selection - Lee Smolin's idea that maybe new universes are born inside black ... 12:49: ... of the fundamental constants, not the origin of everything. Ideas like cosmological natural selection and eternal inflation are helpful because they reduce the amount of work ... 13:26: ... average out? The answer to this is ... no one has any idea. The cosmological natural selection hypothesis doesn't really define the ongoing connection between the ... 14:13: ... to Lee Smolin. I'm making a list, guys. If it turns out the whole cosmological natural selection thing is true, I'll send that list to the Swedish Academy of Sciences. I ...
	2019-12-17: Do Black Holes Create New Universes? 00:10: Cosmological natural selection proposes exactly this - but even better, it claims to be able to test the hypothesis. 01:46: Inspired by biological evolution, theoretical physicist Lee Smolin came up with Cosmological Natural Selection. 08:51: ... cosmological natural selection is true, then the fundamental parameters favouring ... 10:44: ... like to add my own objection: cosmological natural selection is meant to explain the fine tuning in the fundamental ... 11:38: ... cosmological natural selection is an appealing idea because it seeks a natural ... 00:10: Cosmological natural selection proposes exactly this - but even better, it claims to be able to test the hypothesis. 01:46: Inspired by biological evolution, theoretical physicist Lee Smolin came up with Cosmological Natural Selection. 08:51: ... cosmological natural selection is true, then the fundamental parameters favouring black hole ... 10:44: ... like to add my own objection: cosmological natural selection is meant to explain the fine tuning in the fundamental ... 11:38: ... cosmological natural selection is an appealing idea because it seeks a natural explanation ... 00:10: Cosmological natural selection proposes exactly this - but even better, it claims to be able to test the hypothesis. 01:46: Inspired by biological evolution, theoretical physicist Lee Smolin came up with Cosmological Natural Selection. 08:51: ... cosmological natural selection is true, then the fundamental parameters favouring black hole production ... 10:44: ... like to add my own objection: cosmological natural selection is meant to explain the fine tuning in the fundamental constants, which ... 11:38: ... cosmological natural selection is an appealing idea because it seeks a natural explanation for fine ...
	2019-12-09: The Doomsday Argument 01:38: In 1987, physicist Steven Weinberg used this form of anthropic reasoning to estimate the value of the cosmological constant. 01:48: ... a quick refresher: the cosmological constant defines the amount of dark energy, which is the stuff causing ... 01:57: ... in physics from string theory to eternal inflation predict that the cosmological constant could take on different values in different universes, and its ... 02:18: Getting a low cosmological constant is extremely unlikely according to these pictures. 02:33: ... principle - perhaps we’re just in one of the lucky universes with a low cosmological constant because where else could we ... 02:49: ... the assumption that lower cosmological constants were less likely than higher ones, Steven Weinberg reasoned ... 03:31: ... refined his estimate of the cosmological constant to be the value that most astronomers across the multiverse ... 04:49: This sort of reasoning seems useful - it enabled a decent guess at the cosmological constant. 08:39: ... Steven Weinberg’s case the question was “what sort of cosmological constant is the typical astronomer likely to observe - so reference ... 11:20: ... reasoning can lead to powerful predictions, like the value of the cosmological constant, it can lead to dubious but worrying predictions like the ... 01:38: In 1987, physicist Steven Weinberg used this form of anthropic reasoning to estimate the value of the cosmological constant. 01:48: ... a quick refresher: the cosmological constant defines the amount of dark energy, which is the stuff causing the ... 01:57: ... in physics from string theory to eternal inflation predict that the cosmological constant could take on different values in different universes, and its value ... 02:18: Getting a low cosmological constant is extremely unlikely according to these pictures. 02:33: ... principle - perhaps we’re just in one of the lucky universes with a low cosmological constant because where else could we ... 02:49: ... ones, Steven Weinberg reasoned that our universe should have the maximum cosmological constant that would allow galaxies to form - and hence allow our ... 03:31: ... refined his estimate of the cosmological constant to be the value that most astronomers across the multiverse would ... 04:49: This sort of reasoning seems useful - it enabled a decent guess at the cosmological constant. 08:39: ... Steven Weinberg’s case the question was “what sort of cosmological constant is the typical astronomer likely to observe - so reference class was an ... 11:20: ... reasoning can lead to powerful predictions, like the value of the cosmological constant, it can lead to dubious but worrying predictions like the doomsday ... 01:48: ... a quick refresher: the cosmological constant defines the amount of dark energy, which is the stuff causing the expansion of ... 02:49: ... the assumption that lower cosmological constants were less likely than higher ones, Steven Weinberg reasoned that our ...
	2019-12-02: Is The Universe Finite? 11:51: The tension between the Planck results and other cosmological measurements seems to be growing. 13:58: ... to tell you about a very clear one: Stephen Weinberg's prediction of the cosmological constant years before dark energy was ever ... 15:52: ... probably some massively exponentially accelerating universe because the cosmological constant in most universes seems likely to be a lot higher than ... 13:58: ... to tell you about a very clear one: Stephen Weinberg's prediction of the cosmological constant years before dark energy was ever ... 15:52: ... probably some massively exponentially accelerating universe because the cosmological constant in most universes seems likely to be a lot higher than ... 13:58: ... to tell you about a very clear one: Stephen Weinberg's prediction of the cosmological constant years before dark energy was ever ... 11:51: The tension between the Planck results and other cosmological measurements seems to be growing.
	2019-11-18: Can You Observe a Typical Universe? 04:37: ... the 1986 book the Anthropic Cosmological Principle, John Barrow and Frank Tipler misinterpret the strong ...
	2019-11-11: Does Life Need a Multiverse to Exist? 08:37: But an even more finely-tuned parameter appears to be the cosmological constant.
	2019-09-30: How Many Universes Are There? 05:53: For example the cosmological constant – the strength of dark energy – could be different. 06:51: ... are so many bubble universes that at least some will have a low enough cosmological constant for life to ... 07:54: Each different configuration results in a different family of particles and also a different cosmological constant. 08:32: As well as a decent cosmological constant. 05:53: For example the cosmological constant – the strength of dark energy – could be different. 06:51: ... are so many bubble universes that at least some will have a low enough cosmological constant for life to ... 07:54: Each different configuration results in a different family of particles and also a different cosmological constant. 08:32: As well as a decent cosmological constant.
	2019-08-06: What Caused the Big Bang? 03:23: ... density, then Einstein's equations end up having a term that we call the cosmological constant - A positive value for the cosmological constant means a ...
	2019-04-03: The Edge of an Infinite Universe 16:01: ... on physics stackexchange, in which he suggests that the shrinking cosmological horizon could merge with the event horizon to produce a global state ...
	2019-03-28: Could the Universe End by Tearing Apart Every Atom? 00:25: ... expansion mathematically we describe a constant energy density with the cosmological constant in the equations of Einstein's general theory of relativity but ... 04:25: ... let's add dark energy in the form of a cosmological constant it usually hangs out outside the brackets because it's emo, but ... 04:32: ... volume increases density does not go down, the basic definition of the cosmological constant. So now the pressure term is A, negative and B because of this ... 00:25: ... expansion mathematically we describe a constant energy density with the cosmological constant in the equations of Einstein's general theory of relativity but what if ... 04:25: ... let's add dark energy in the form of a cosmological constant it usually hangs out outside the brackets because it's emo, but we can ... 04:32: ... volume increases density does not go down, the basic definition of the cosmological constant. So now the pressure term is A, negative and B because of this factor of ...
	2019-03-20: Is Dark Energy Getting Stronger? 00:04: ... currently accepted cosmological description of our universe is called the Lambda CDM Model and is built ... 00:45: ... looking at a new paper in Nature Astronomy, “Cosmological constraints from the Hubble diagram of quasars at high redshifts” by ... 00:55: It hints that the cosmological constant may not be so constant after all. 02:13: Mathematically we represent a constant vacuum energy with Einstein’s cosmological constant – or Lambda. 02:51: ... the textbooks, this type of cold dark matter sits alongside the cosmological constant as our best description of how the universe behaves on the ... 05:32: Perhaps the cosmological constant is not so constant, or dark matter is not so cold after all. 11:47: Are concordance and the cosmological constant dead? 00:55: It hints that the cosmological constant may not be so constant after all. 02:13: Mathematically we represent a constant vacuum energy with Einstein’s cosmological constant – or Lambda. 02:51: ... the textbooks, this type of cold dark matter sits alongside the cosmological constant as our best description of how the universe behaves on the largest ... 05:32: Perhaps the cosmological constant is not so constant, or dark matter is not so cold after all. 11:47: Are concordance and the cosmological constant dead? 00:45: ... looking at a new paper in Nature Astronomy, “Cosmological constraints from the Hubble diagram of quasars at high redshifts” by Risaliti and ... 00:04: ... currently accepted cosmological description of our universe is called the Lambda CDM Model and is built on the idea ...
	2019-02-07: Sound Waves from the Beginning of Time 12:20: They also confirm the dark energy behaves just as is predicted by Einsteins cosmological constant.
	2019-01-24: The Crisis in Cosmology 09:15: Well, first you figure out what starting cosmological parameters... 12:08: The current calculations assume that dark energy is described by the cosmological constant,... 09:15: Well, first you figure out what starting cosmological parameters...
	2019-01-09: Are Dark Matter And Dark Energy The Same? 03:34: In Einstein’s equations and the Friedmann equations, that constant energy density is represented by the cosmological constant, or Lambda. 07:49: So, you remember I said that a constant POSITIVE energy density can be expressed as a cosmological constant? 08:02: Well a constant NEGATIVE energy density – like the one proposed by Farnes, gives a negative cosmological constant. 08:18: ... gravity for the whole cosmos, this negative mass fluid – as a negative cosmological constant – has the same competing effects as regular dark energy, but in ... 08:50: ... Farnes acknowledges that his proposal gives a negative cosmological constant that ultimately decelerates, but there’s some contradiction ... 09:06: And yet a negative cosmological constant gives you an extremely different universe. 09:15: ... this thing - to correctly conclude that a universe with a negative cosmological constant should have a sinusoidal scale ... 09:43: The negative cosmological constant is the source of that slow-down and for the subsequent accelerating collapse. 10:48: ... a negative cosmological constant and this sinusoidal expansion, any slowdown happens near the ... 03:34: In Einstein’s equations and the Friedmann equations, that constant energy density is represented by the cosmological constant, or Lambda. 07:49: So, you remember I said that a constant POSITIVE energy density can be expressed as a cosmological constant? 08:02: Well a constant NEGATIVE energy density – like the one proposed by Farnes, gives a negative cosmological constant. 08:18: ... gravity for the whole cosmos, this negative mass fluid – as a negative cosmological constant – has the same competing effects as regular dark energy, but in the ... 08:50: ... Farnes acknowledges that his proposal gives a negative cosmological constant that ultimately decelerates, but there’s some contradiction because he ... 09:06: And yet a negative cosmological constant gives you an extremely different universe. 09:15: ... this thing - to correctly conclude that a universe with a negative cosmological constant should have a sinusoidal scale ... 09:43: The negative cosmological constant is the source of that slow-down and for the subsequent accelerating collapse. 10:48: ... a negative cosmological constant and this sinusoidal expansion, any slowdown happens near the turnaround ...
	2018-05-23: Why Quantum Information is Never Destroyed 11:11: Merissan has plans to use the loss of energy in cosmological redshift as a refutation of conservation of energy arguments. 11:59: Could the energy lost to cosmological redshift actually become dark energy? 12:23: But it's dropped off since then due to cosmological redshift. 11:11: Merissan has plans to use the loss of energy in cosmological redshift as a refutation of conservation of energy arguments. 11:59: Could the energy lost to cosmological redshift actually become dark energy? 12:23: But it's dropped off since then due to cosmological redshift.
	2018-05-16: Noether's Theorem and The Symmetries of Reality 01:14: The simplest example of this is the case of cosmological redshift. 04:52: Energy can be lost in the case of cosmological redshift, and it can be created from nowhere in the case of dark energy. 06:32: ... any object moving on any path or indeed any system quantum-mechanical to cosmological evolving between two ... 01:14: The simplest example of this is the case of cosmological redshift. 04:52: Energy can be lost in the case of cosmological redshift, and it can be created from nowhere in the case of dark energy.
	2018-03-21: Scientists Have Detected the First Stars 04:20: The absorption dip was predicted by our cosmological models, and it was right where we thought it would be. 04:50: Our cosmological models can't explain how this early hydrogen gas could possibly be this cold. 04:20: The absorption dip was predicted by our cosmological models, and it was right where we thought it would be. 04:50: Our cosmological models can't explain how this early hydrogen gas could possibly be this cold.
	2018-02-28: The Trebuchet Challenge 00:00: [JINGLE PLAYING] Energy is a powerful tool for predicting the behavior of our universe, from quantum to cosmological scales.
	2018-01-17: Horizon Radiation 01:01: ... horizon of a black hole, out of which no information can travel or the cosmological horizon that limits the observable ...
	2017-09-28: Are the Fundamental Constants Changing? 10:50: ... surveys with future generations of telescopes, more refined cosmological models, and better atomic clocks will also help scientists shave down ...
	2017-06-07: Supervoids vs Colliding Universes! 03:58: It's a cosmological tug-of-war.
	2016-11-09: Did Dark Energy Just Disappear? 04:06: The new study claims a 3-sigma confidence that there is a positive cosmological constant. 04:14: ... quick aside: the cosmological constant, written as lambda, is the thing you add to Einstein's ... 04:26: If the cosmological constant exists, and is larger than zero, then dark energy is a real thing. 04:32: ... so 3-sigma confidence in a positive cosmological constant basically means this: if you repeated this experiment many, ... 05:44: ... Laureates also claimed a significance of 3-sigma or lower for a positive cosmological constant based on that early supernova data ... 04:06: The new study claims a 3-sigma confidence that there is a positive cosmological constant. 04:14: ... quick aside: the cosmological constant, written as lambda, is the thing you add to Einstein's equations of ... 04:26: If the cosmological constant exists, and is larger than zero, then dark energy is a real thing. 04:32: ... so 3-sigma confidence in a positive cosmological constant basically means this: if you repeated this experiment many, many times, ... 05:44: ... Laureates also claimed a significance of 3-sigma or lower for a positive cosmological constant based on that early supernova data ... 04:32: ... so 3-sigma confidence in a positive cosmological constant basically means this: if you repeated this experiment many, many times, about ... 04:26: If the cosmological constant exists, and is larger than zero, then dark energy is a real thing. 04:14: ... quick aside: the cosmological constant, written as lambda, is the thing you add to Einstein's equations of general ...
	2016-06-22: Planck's Constant and The Origin of Quantum Mechanics 14:21: This can change the power spectrum, so the distribution of the sizes of its blobs, which is really important for measuring cosmological parameters.
	2016-05-25: Is an Ice Age Coming? 12:46: ... Lidster and a few others have wondered whether the energy lost in the cosmological redshift of photons could account for the energy gained by dark ...
	2016-05-18: Anti-gravity and the True Nature of Dark Energy 01:24: This dark energy is described by the cosmological constant in the equations of general relativity. 01:48: Today, we're going to talk about the simplest interpretation of dark energy, one where the cosmological constant really is constant. 02:03: A constant cosmological constant represents a nonzero energy of empty space, a vacuum energy. 06:26: This was actually Einstein's motivation for adding the cosmological constant in the first place. 06:47: The cosmological constant was designed to work in the opposite direction to regular matter and energy. 07:08: The effect of the cosmological constant is the combined effect of dark energy's own density and pressure. 01:24: This dark energy is described by the cosmological constant in the equations of general relativity. 01:48: Today, we're going to talk about the simplest interpretation of dark energy, one where the cosmological constant really is constant. 02:03: A constant cosmological constant represents a nonzero energy of empty space, a vacuum energy. 06:26: This was actually Einstein's motivation for adding the cosmological constant in the first place. 06:47: The cosmological constant was designed to work in the opposite direction to regular matter and energy. 07:08: The effect of the cosmological constant is the combined effect of dark energy's own density and pressure. 02:03: A constant cosmological constant represents a nonzero energy of empty space, a vacuum energy.
	2016-05-11: The Cosmic Conspiracy of Dark Energy Challenge Question 02:16: ... that are derived from those, dark energy is described by a positive cosmological ... 06:20: Feel free to propose any solutions you come up with for this apparent cosmological coincidence. 02:16: ... that are derived from those, dark energy is described by a positive cosmological constant. ...
	2016-05-04: Will Starshot's Insterstellar Journey Succeed? 09:54: ... it's really fully described by a constant cosmological constant and so has an unchanging density with time, then no, space time ...
	2016-04-27: What Does Dark Energy Really Do? 00:40: And this is only allowed if we introduce a new type of energy represented by the cosmological constant. 01:33: During that expansion, it increases the wavelength of these electromagnetic waves, resulting in what we see as redshift, cosmological redshift. 07:10: However, this accelerating expansion can be explained with the same bit of math, the cosmological constant, pointing to the same physics, dark energy. 07:22: Add the cosmological constant to the first Friedmann equation, and we reconcile the left and the right side. 07:36: This lets us interpret the cosmological constant as representing a sort of vacuum energy, a property of space itself. 08:16: Expansion will only depend on the cosmological constant. 08:50: But with a positive cosmological constant, the universe will eventually have a constant Hubble Parameter. 09:23: If the cosmological constant stays constant, we can expect an exponential growth to continue. 11:45: ... is so thoroughly verified in so many other ways, and the addition of the cosmological constant works so well to describe the discrepancy, it's strongly ... 12:03: As we saw today, the cosmological constant solves two measure discrepancies. 00:40: And this is only allowed if we introduce a new type of energy represented by the cosmological constant. 07:10: However, this accelerating expansion can be explained with the same bit of math, the cosmological constant, pointing to the same physics, dark energy. 07:22: Add the cosmological constant to the first Friedmann equation, and we reconcile the left and the right side. 07:36: This lets us interpret the cosmological constant as representing a sort of vacuum energy, a property of space itself. 08:16: Expansion will only depend on the cosmological constant. 08:50: But with a positive cosmological constant, the universe will eventually have a constant Hubble Parameter. 09:23: If the cosmological constant stays constant, we can expect an exponential growth to continue. 11:45: ... is so thoroughly verified in so many other ways, and the addition of the cosmological constant works so well to describe the discrepancy, it's strongly suggested this ... 12:03: As we saw today, the cosmological constant solves two measure discrepancies. 07:10: However, this accelerating expansion can be explained with the same bit of math, the cosmological constant, pointing to the same physics, dark energy. 12:03: As we saw today, the cosmological constant solves two measure discrepancies. 09:23: If the cosmological constant stays constant, we can expect an exponential growth to continue. 11:45: ... is so thoroughly verified in so many other ways, and the addition of the cosmological constant works so well to describe the discrepancy, it's strongly suggested this ... 01:33: During that expansion, it increases the wavelength of these electromagnetic waves, resulting in what we see as redshift, cosmological redshift.
	2016-04-20: Why the Universe Needs Dark Energy 06:34: We missed the cosmological constants. 06:50: ... we derive the first Friedmann equation with the cosmological constant included-- that's the lambda symbol, here-- we end up with this ... 07:00: ... the cosmological constant is positive, this works on the side of the density term to help ... 07:31: The expression "cosmological constant" is a clue. 07:43: The weird stuff described by the cosmological constant doesn't do that. 08:39: Soon, we'll get to the second and most compelling piece of evidence for dark energy and for the cosmological constant. 06:50: ... we derive the first Friedmann equation with the cosmological constant included-- that's the lambda symbol, here-- we end up with this little ... 07:00: ... the cosmological constant is positive, this works on the side of the density term to help bring ... 07:31: The expression "cosmological constant" is a clue. 07:43: The weird stuff described by the cosmological constant doesn't do that. 08:39: Soon, we'll get to the second and most compelling piece of evidence for dark energy and for the cosmological constant. 07:43: The weird stuff described by the cosmological constant doesn't do that. 06:50: ... we derive the first Friedmann equation with the cosmological constant included-- that's the lambda symbol, here-- we end up with this little extra ... 06:34: We missed the cosmological constants. 07:27: But what does this cosmological-constant thing actually do? 08:04: ... some point, drop below that of this vacuum energy, as described by the cosmological-constant ... 07:27: But what does this cosmological-constant thing actually do? 08:04: ... some point, drop below that of this vacuum energy, as described by the cosmological-constant ... 07:27: But what does this cosmological-constant thing actually do?
	2016-03-23: How Cosmic Inflation Flattened the Universe 06:48: Actually, Einstein came up with the exact mathematical description that we need-- an antigravity term called the cosmological constant. 07:30: The cosmological constant represents something that can happen to our spacetime. 07:38: The cosmological constant adds some energetic stuff to empty space. 06:48: Actually, Einstein came up with the exact mathematical description that we need-- an antigravity term called the cosmological constant. 07:30: The cosmological constant represents something that can happen to our spacetime. 07:38: The cosmological constant adds some energetic stuff to empty space. 07:30: The cosmological constant represents something that can happen to our spacetime.
	2015-09-30: What Happens At The Edge Of The Universe? 03:37: Given our best measurements of cosmological parameters, we think that the cosmic event horizon is around 16 billion light years away.
	2015-03-25: Cosmic Microwave Background Explained 04:28: ... the wavelength of free streaming light through a process called cosmological ...
	2015-02-25: How Do You Measure the Size of the Universe? 02:53: Using something called cosmological redshift, which is like a fingerprint that the expansion of space leaves on beams of light.

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