
20220210: The Nature of Space and Time AMA
 00:03: ... of both space and time okay we start in this description with newtonian physics in which they're the dimensions that form the stage on which ...


20220119: How To Build The Universe in a Computer
 02:23: He’d then adjust the velocities of all according to Newton’s laws.
 02:56: ... the time of Isaac Newton it had been possible to write down equations describing the trajectories ...
 03:53: In an NBody simulation Newton’s laws of motion and gravity are applied over a series of time steps.


20220112: How To Simulate The Universe With DFT
 06:03: In other words, Newtonian mechanics.
 06:06: When we use Newton to solve, say, the threebody problem, we can solve the equations for each of the 3 particles separately.
 07:15: In the Newtonian case, particles only interact locally, and that means the Newtonian equations of motion are what we call separable.
 07:46: ... fact in Newtonian mechanics we can not only write down the equations of motion for each ...
 08:02: But if we want to keep the quantum behaviour of quantum mechanics we can’t throw away most of configuration space like we do in Newtonian mechanics.
 10:54: Because they aren’t interacting, the equations of motion for these electrons are separable, just like in Newtonian mechanics.


20211220: What Happens If A Black Hole Hits Earth?
 14:10: ... ways to break general relativity. There was the one on modified newtonian dynamics as an explanation for dark matter, and the one on fuzzballs  ...


20211210: 2021 End of Year AMA!
 00:02: ... the bucket spinning or not spinning referencing um the classic isaac newton thought experiments um but tricky actually gives us an answer and this ...


20211110: What If Our Understanding of Gravity Is Wrong?
 02:02: ... to Isaac Newton’s Law of Universal Gravitation, the gravitational field drops off ...
 02:46: But what if gravity doesn’t obey Newton’s law of gravity?
 02:52: ... Einstein found that Newtonian gravity breaks down when the gravitational field gets too strong  ...
 03:08: But Einsteinian gravity looks exactly like Newtonian gravity when gravitational fields get weak.
 03:18: What if Newtonian gravity breaks down both for very strong AND very weak fields?
 03:25: This is the idea behind Modified Newtonian Dynamics, or MOND, proposed by Israeli physicist Mordehai Milgrom in 1982.
 03:53: ... can be done with a modification to either Newton’s law of universal gravitation  in which case gravity has a minimum ...
 06:10: ... Instead it does what it was designed to do  it reproduces good ol’ Newtonian ...
 09:53: ... acted like Newtonian mechanics on solar system scales, like MOND on galactic scales, and like ...


20211102: Is ACTION The Most Fundamental Property in Physics?
 01:22: ... momentum and kinetic energy  but to no avail. In the meantime Isaac Newton came up with his laws of motion which gave us the instant and miraculous ...
 05:00: ... you study Newton’s mechanics and then move on to Lagrangian mechanics, it seems almost like ...
 05:52: ... motivations in developing general relativity was the fact that Newtonian mechanics failed to correctly predict the orbit of Mercury. If you ...
 11:12: ... wavefunction. This is analogous to how Lagrangian mechanics reproduced Newton’s mechanics. And it’s no coincidence, because the path integral is the ...
 18:34: ... theory feels like alchemy. Relatedly, Cluebcke says “Rough shade on Newton with that whole "you can't transmute apples into gold" line”  and for ...
 18:52: ... could Newton have know which lines of inquiry would be “fruitful” without exploring ...


20211020: Will Constructor Theory REWRITE Physics?
 00:00: ... people behind the greatest leaps in physics  Einstein, Newton, Heisenberg, all had the uncanny ability to see the fundamentals  see ...
 00:46: the laws of thermodynamics or Newton’s laws of motion Step 3.
 01:43: ... can derive all of thermodynamics and Newtonian mechanics and electromagnetism and so on from two master theories: ...
 04:55: ... mechanistic philosophy that dominates physics really started with Isaac Newton, so it’s appropriate to start with the falling apple that apocryphally ...
 05:06: In Newton’s picture, the apple has a current state, stationary and up in the tree.


20210309: How Does Gravity Affect Light?
 01:17: ... assumed that Isaac Newton’s theory of gravity was the full picture, and that light behaves like any ...
 01:34: We now know that both gravity and light are much weirder than Newton thought.
 07:16: Einstein was in the business of overturning the ideas of Newton, so it’s not surprising that he turns to one of Newton’s great rivals.
 07:24: The Dutch physicist Christiaan Huygens disagreed with Newton on many things  including the idea that light is a particle.
 11:28: The number he got was exactly twice the deflection calculated by Cavendish based on Newton’s gravity.


20201118: The Arrow of Time and How to Reverse It
 02:31: ... Newton’s laws of motion combined with Coulomb’s law perfectly describe how the ...


20201027: How The Penrose Singularity Theorem Predicts The End of Space Time
 00:34: ... When John Mitchell and PierreSimon Laplace explored Newton’s law of universal gravitation, they realized the possibility ...


20201013: Do the Past and Future Exist?
 01:17: As with many ideas in physics, this one originates with Isaac Newton.
 01:21: Newton was the first to come up with a set of laws that allow us to predict the motion of all objects in the universe.
 01:27: ... Newton’s revelations led to the notion of the deterministic universe  the idea ...
 01:54: Newton’s picture of the universe included one other assumption that we know for sure is wrong.
 02:08: Newton assumed that all particles, all observers, all points in space were ruled by a single, constantly ticking clock.
 02:27: Here’s a nice way to represent Newton’s picture of space and time.
 05:33: The representation of the block universe that I showed you is very Newtonian.
 05:47: Newton says there’s only one way to slice the universe.


20200908: The Truth About Beauty in Physics
 02:19: There IS an extremely simple, elegant law underlying planetary motion  it's Newton’s Law of Universal Gravitation.
 02:27: Not only can Kepler’s complicated laws be derived from Newton, but Newtonian gravity makes predictions far beyond the motion of the planets.
 02:35: But even Newtonian gravity proved to be a special case of a much deeper law.
 02:41: Einstein’s equations of general relativity give even better precision than Newton’s law  perhaps perfect precision  in their description of gravity.
 02:50: And general relativity is also more explanatory than Newton  it tells us that gravity results from the warping of space and time.
 03:13: Ptolemy, Copernicus, Kepler, Newton, Einstein  each followed their own sense of mathematical beauty in this long quest to understand gravity.
 05:59: ... Newton’s law of gravitation is a great example, and we can be sure that Newton ...
 06:35: The step from Kepler to Newton suggests so, but then why does complexity seem to increase when you go one level deeper from Newton to Einstein?
 09:23: Same with Newton’s gravity, derived from observations of apples and the moon, but it predicts the motions of galaxies.


20200728: What is a Theory of Everything: Livestream
 00:00: ... have challenged this and started asking those questions anyway isaac newton came along and said hey wait a minute it's a perfectly legit question ...


20200608: Can Viruses Travel Between Planets?
 14:22: ... theory is modified newtonian dynamics  MONDS  in which gravity doesn’t drop off as quickly as the ...


20200527: Does Gravity Require Extra Dimensions?
 00:33: ... was the first force to get a decent mathematical description with Isaac Newton’s Law of Universal Gravitation back in the 17th ...
 01:37: But even Newton’s old theory works great in almost all situations.
 01:42: And deviations from Newton’s description may point the way to an understanding deeper than Einstein’s.
 01:53: ... Newton’s law of gravitation is an example of such a law  basically, the strength ...
 02:38: That’s where the r^2 comes from on the bottom of Newton’s law of gravitation.
 03:36: Newton’s inverse square law for gravity tells us there are 2+1 = 3 spatial dimensions.
 07:36: It’s actually the OG  the experiment first used to measure the strength of the force of gravity  or the G in Newton’s law of gravitation.


20200511: How Luminiferous Aether Led to Relativity
 04:06: ... only 5 years before his death. Across the channel, a much younger Isaac Newton was sitting in Cambridge making life difficult for Huygens. First his ...
 05:08: ... versus Newton. Light as a wave versus a particle. Most accepted Newton  as most always ...
 06:22: ... so we get to the end of the 19th Century. With Newton’s mechanics and gravity, Huygen’s optics, Maxwell’s electromagnetism, ...
 07:19: ... using the Galilean transformation, which is part of the foundation of Newton’s mechanics. I were a smug 19th century physicist, I’d wanna hope Galilean ...
 11:20: ... contradicts Galilean relativity, and so revealed a crack in the sacred Newtonian mechanics. This directly inspired Hendrik Lorentz to derive his Lorentz ...
 11:42: ... and then his general theory of relativity that ultimately overthrew Newton’s theory of gravity, and, according to Einstein, it revealed the cracks in ...


20200218: Does Consciousness Influence Quantum Mechanics?
 15:59: ... for not nerding hard enough because you corrected my pronunciations of Newton's book while missing my questionable taxonomic identify of apes versus ...
 16:17: ... roman or princhipia like a modern Italian or latin mass, and whether Newton himself would have said the latter  it seems probably he ...


20200211: Are Axions Dark Matter?
 16:00: ... last week's comment responses I corrected my pronundiation for Newton's book  and then lots of people corrected my correction. Principia ...


20200203: Are there Infinite Versions of You?
 12:40: The solutions only exist in special cases for Newtonian gravity.
 15:56: Also I mispronounced the name Newton's great work  it's PrinKipia  hard K, not soft principia.


20200120: Solving the Three Body Problem
 00:20: ...  and arguably all of science changed forever in 1687 when Isaac Newton published his Principia. Within it were equations of motion and gravity ...
 01:24: ... does it mean to find a solution to the threebody problem? Newton’s laws of motion and his law of universal gravitation give us a set of ...
 02:06: ... the case of two gravitating bodies, the solutions to Newton’s laws are just the equations for the path traveled by the bodies  be it ...
 03:18: ... motion of many bodies. For most of the three centuries since Newton, predicting the motion of the planets and the moon was critical for ...


20191015: Loop Quantum Gravity Explained
 15:35: ... counters the gravitatinally attraction  if you'll forgive my crude Newtonian ...


20190923: Is Pluto a Planet?
 02:20: This picture was cleaned up by the observations of Galileo and Brahe and the mathematical models of Kepler and Newton.
 02:27: Newton’s Laws of Gravity led to consistent predictability of the motion of the heavenly spheres.
 03:06: New wandering stars were discovered in the centuries following Newton.
 03:19: That same motion almost perfectly reflected the clockwork predictions of Newtonian mechanics.


20190424: No Dark Matter = Proof of Dark Matter?
 00:03: ... of gravitational theory itself the first such proposal was Mons modified Newtonian dynamics proposed by Mordecai Milgram in the early 80s the idea is the ...


20190328: Could the Universe End by Tearing Apart Every Atom?
 03:05: ... thing is the second Friedman equation it's basically the equivalent of Newton's law of gravity for the whole universe describing the acceleration or ...


20190306: The Impossibility of Perpetual Motion Machines
 06:14: After all, Newton tells us, an object in motion tends to remain in motion unless acted on by an outside force.


20190130: Perpetual Motion From Negative Mass?
 01:24: Let’s start with mass in Newton’s physics.
 01:34: This is encapsulated in Newton’s second law, which defines the connection between the amount of force applied and the acceleration that results.
 01:52: It appears in Newton’s Law of Universal Gravitation.
 02:35: ... Newton’s second law with the law of gravitation and you see that although massive ...
 02:57: ... with very different masses fall at the same rate, and that was before Newton came even ...
 03:19: OK, so how do negative masses work in Newtonian mechanics?
 03:28: In fact, in Newtonian gravity, any like masses – both positive or both negative  should produce a mutually attractive force.
 04:37: Newton’s second law seems to say that negative inertial masses respond oppositely to the applied force.
 05:47: ... fact Newton’s law of gravitation is really only approximation of a much more complete ...
 08:18: So far this seems to echo the Newtonian prediction.
 08:42: But this should crudely translate to the case of two equalsized objects, although not in the simple, linear style of Newtonian mechanics.
 10:39: We then happily plugged our negative inertial mass into Newton’s 2nd law to get acceleration.
 10:58: ... carved into the geometry of Einstein’s spacetime – are the GR analogs of Newton’s second law and give the equations of motion of ...
 11:10: ... principle, or from Lagrangian mechanics – a more modern version of Newton’s laws of ...


20190109: Are Dark Matter And Dark Energy The Same?
 04:18: The answer is complicated  it’s not always obvious how weird stuff like negative masses translates from general relativity to Newton’s laws.
 04:26: But for now let’s follow the paper’s argument, which is based on Newtonian physics.
 04:31: In Newtonian gravity, you multiply the two masses together along with some other stuff to get the strength of their mutual gravitational attraction.
 04:58: Dr. Farnes takes the Newtonian argument a step further.
 05:09: It also determines the way objects respond to forces via Newton’s 2nd Law.
 05:43: According to this Newtonian interpretation.
 06:22: ... positive and negative mass particles, along with his interpretations of Newton’s ...
 08:18: ... we look at the second Friedmann equation, which is really the analog of Newton’s law of gravity for the whole cosmos, this negative mass fluid – as a ...


20181212: Quantum Physics in a Mirror Universe
 00:02: ... get flipped the laws of physics should be unaltered in that mirror world Newton's laws will still give the balls trajectory those laws work the same no ...


20181107: Why String Theory is Right
 02:33: Everyone knows that Isaac Newton discovered gravity when he fell out of an apple tree, or something like that.


20181003: How to Detect Extra Dimensions
 04:07: In our universe, gravity appears to diminish according to the inverse square law, as reflected in Newton's law of universal gravitation.


20180920: Quantum Gravity and the Hardest Problem in Physics
 02:06: ... the earlier ideas of Isaac Newton, in which space and time are treated as separate and universal, special ...
 02:49: But the Schrodinger equation treats space and time as fundamentally separate in the oldfashioned Newtonian way.


20180718: The Misunderstood Nature of Entropy
 03:57: This theory explained thermodynamic behavior as the summed result of the individual motion of tiny particles under Newton's laws of motion.
 10:22: ... the laws of motion, whether Newtonian or quantum mechanical, don't care about the direction of time, and yet, ...


20180711: Quantum Invariance & The Origin of The Standard Model
 02:03: Newton's laws of motion and gravity, Maxwell's equations for electromagnetism, Einstein's general relativity, and of course, the standard model.


20180620: The Black Hole Information Paradox
 11:54: They were glimpsed as dark stars in the mathematics of Isaac Newton's law of universal gravitation.
 12:01: So, to continue your own mathematical journey into black holes, Newton's gravity is the place to start.
 12:07: ... comprehensive series on gravitational physics that will take you from Newton's law all the way through gravitational field and celestial ...


20180613: What Survives Inside A Black Hole?
 06:26: ... Newton's law of universal gravitation and Coulomb's law for electrostatics say ...


20180523: Why Quantum Information is Never Destroyed
 00:36: Newton's equations for classical mechanics, Maxwell's equations for electromagnetism, and the Schrodinger equation for quantum mechanics.


20180516: Noether's Theorem and The Symmetries of Reality
 05:00: The law of conservation of energy is fundamental in Newtonian mechanics, in which space and time are unvarying and eternal.


20180418: Using Stars to See Gravitational Waves
 08:40: ... the existence of gravitational waves, he had to master it precursor, Newtonian ...
 08:51: He needed to understand Newton's theory of gravity well enough to see where it failed.
 08:56: ... already done some serious universitylevel physics, then mastering Newtonian gravity is also your next step toward understanding Einstein's view of ...
 09:10: ... from the basics of classical mechanics through the intricacies of Newtonian ...


20180228: The Trebuchet Challenge
 01:43: ... Newton's laws tell us that when two objects with different masses are accelerated ...
 04:46: ... to figure out the equations of motion of a trebuchet in terms of Newton's laws, with a complicated series of force vectors, some gnarly geometry, ...


20180214: What is Energy?
 01:38: Fun side note, Leibniz was famously arrival of Isaac Newton.
 01:43: Besides the whole coinventing calculus thing, Leibniz's vis viva seen as a competition to Newton's idea of conservation of momentum.
 01:53: Newtonian mechanics had only recently revolutionized physics.
 03:04: But that's just Newtonian mechanics.
 06:55: Just adding conservation of energy to Newton's mechanics gives an extra constraint that allows us to solve problems we couldn't otherwise.
 07:08: Newtonian mechanics is great at describing the motion of simple systems of a few rigid objects.
 07:56: ... its conservation has led to new types of mechanics that have supplanted Newtonian mechanics, for example Lagrange mechanics, which, in its simplest form, ...
 08:12: It produces the same equations of motion as Newtonian mechanics but without having to keep track of those innumerable fiddly force vectors.


20171129: Citizen Science + ZeroPoint Challenge Answer
 06:38: Multiply those together and you get that a gecko can support something like 40 newtons, or four kilograms, in Earth gravity.


20170928: Are the Fundamental Constants Changing?
 03:11: The dimensions behind, say, Newton's gravitational constant or the mass of the electron all have arbitrary human definitions.


20170119: The Phantom Singularity
 00:16: [MUSIC PLAYING] Isaac Newton's universal law of gravitation was an incredible insight when he figured it out in the late 1600s.
 00:39: Newton's equation gives you the gravitational force exerted between two masses, m1 and m2 that are a distance R apart.
 01:21: According to Newton's law, in order to fuel that infinite gravitational acceleration you need to get zero distance from an object's center of mass.
 04:04: So, does the fact that it includes a singularity mean there's something fundamentally wrong with Newton's law of gravitation?
 04:16: ... gravitational field is too strong say, near a star or a black hole Newton's law gives the wrong answers, and we need Einstein's general theory of ...
 04:30: So does general relativity rid us of Newton's pesky singularity?
 06:47: r, the distance to the center of mass, remains in the denominator just as it was in Newton's law.
 07:00: This gives us the same infinite gravitational pull as the Newtonian singularity.
 07:05: And just as with the Newtonian case, this gravitational singularity can only exist if infinite densities are possible.
 07:13: But unlike Newton's laws of gravity, the Schwarzschild metric actually tells us whether or not that infinite density is expected.
 07:22: To see how, we need to look at the second singularity in this equation, a singularity that Newton's law does not contain.


20170104: How to See Black Holes + Kugelblitz Challenge Answer
 10:26: Well, here, we're saved by Newton's shell theorem, which states that the gravitational force inside a perfectly symmetric shell is zero.


20161221: Have They Seen Us?
 16:17: ... the escape velocity at the surface of the Earth because we're used to Newtonian approximations ...
 16:49: ... happen to get exactly the right size for the event horizon if you use Newtonian gravity to calculate the distance at which the escape velocity reaches ...


20161214: Escape The Kugelblitz Challenge
 05:22: ... Newton's shell theorem tells us that the entire inside of a spherically symmetric ...


20160914: SelfReplicating Robots and Galactic Domination
 00:41: Space stuff gravitates around in slow, stately arcs that would make Newton proud.


20160622: Planck's Constant and The Origin of Quantum Mechanics
 04:13: It was Sir Isaac Newton who first analyzed this heat glow in the 1660s when he used a prism to split sunlight into its component colors.


20160525: Is an Ice Age Coming?
 13:58: ... that the law of conservation of energy, as we learned when we studied Newtonian mechanics, is a feature of flat ...
 14:12: ... gravity from a Newtonian perspective requires the invention of a new quantity gravitational ...


20160518: Antigravity and the True Nature of Dark Energy
 04:04: This thing is in a real way just Newton's law of gravitation for the whole cosmos.
 11:35: This law is a property of a Newtonian universe, in which space and time are fixed static dimensions.


20160413: Will the Universe Expand Forever?
 02:16: ... let's develop intuition a bit by thinking about gravity from a Newtonian perspective as a force, rather than as an Einsteinian spacetime ...
 02:58: Now this escape velocity comes right out of Newton's universal law of gravitation, which itself can be derived from the Einstein equations.
 03:07: The mathematical step from Newton's gravity to escape velocity comes from thinking about energy.
 03:40: ... this Newtonian analogy and, remember, ignoring dark energy the universe also has an ...
 09:29: And to understand how does so will take us far beyond the capacity for Newtonian analogy.


20160323: How Cosmic Inflation Flattened the Universe
 11:47: It doesn't exist in the inertial reference frames for which Newton's laws are valid.


20160316: Why is the Earth Round and the Milky Way Flat?
 02:15: Here it's fine to think about gravity Newtonianly as a force rather than as an Einsteinian warping of space time.
 02:23: ... Newton's Universal Law of Gravitation tells us that the strength of gravity drops ...


20160106: The True Nature of Matter and Mass
 02:20: The photons exert a force on the box, the box also exerts a force on the photons Newton's Third Law, which gives us the conservation of momentum.


20151125: 100 Years of Relativity + Challenge Winners!
 01:32: But for now we have some math to do and it's all going to be Newtonian.
 01:37: Newton was OK, too, I guess.
 02:13: ... some Newtonian mechanics to see how much mass is needed to accelerate Apophis to get ...
 04:12: Newton's law of universal gravitation tells us the force between two massive objects.


20151111: Challenge: Can you save Earth from a Killer Asteroid?
 01:43: To do this, you'll need lots of Newton.
 01:49: You'll need Newton's law of universal gravitation as well as basic mechanics and kinematics.


20151007: The Speed of Light is NOT About Light
 01:46: This Galilean Relativity is an incredible insight that Isaac Newton would later codify into his Laws of Motion.
 02:11: By the late 1800s, we have Maxwell's equations, Newton's mechanics, various other awesome theories.
 02:38: In fact, we now know that even Newton's mechanics were using assumptions that implied an infinite speed of light, which is really bad.
 03:16: Galileo and Newton tell us that total monkey speed equals pony blade speed plus monkey skate speed.
 04:37: Newton's mechanics use it.
 05:06: The transformation underpinning Newton's mechanics is wrong.


20150923: Does Dark Matter BREAK Physics?
 03:32: According to Newton, gravity weakens proportional to distance from its source squared.
 03:50: Well, it turns out that if you make a simple change to Newton's gravity, things work out.
 04:05: The original modified Newtonian dynamics hypothesis, and it's a general relativity extensions, tries to give us this basic relationship for gravity.


20150827: Watch THIS! (New Host + Challenge Winners)
 00:09: There was a Newtonian and an Einsteinian version of the challenge.
 00:13: Let's start with the answer to the Newtonian version.
 00:15: ... key to the Newtonian challenge was getting an expression for the gravitational force on the ...
 01:26: This is kind of a coincidence of the specific situation of a uniformly dense planet and Newtonian mechanics.
 05:05: But remember, the Newtonian solution is also there.


20150819: Do Events Inside Black Holes Happen?
 00:37: ... treat gravity Einsteinially rather than Newtonianially from the outset, it will help a lot if I can rely on technical terms ...
 07:03: ... Newtonian gravity, a projectile on the surface of a planet or a star needs a ...


20150812: Challenge: Which Particle Wins This Race?
 00:17: For the purposes of this challenge, I want you to treat gravity and all physics Newtonianly.
 00:59: ... Newtonian gravity, you can work out an expression for the orbital speed of this ...
 03:35: Use the subject line "Twoparticle Newtonian gravity challenge".
 05:09: You can only enter one challenge, though, Newton or Einstein.
 05:16: ... can enter the Einsteinian challenge at all, that means you can solve the Newtonian challenge in about 60 seconds, which isn't much of a ...
 05:29: But you also have more time, and both the Newtonian and Einsteinian versions of the question are pretty fun exercises.


20150805: What Physics Teachers Get Wrong About Tides!
 02:01: Assumption one we're going to use Newtonian gravity.
 03:09: And in Newtonian physics, it's fake.
 03:13: Remember, Earth itself is accelerating towards the Moon, so according to Newton, Earth's frame is noninertial.
 12:39: ... what the geodesics should be that resemble that basically give you Newton's laws of motion as if there were a gravitational force are just the ...
 13:18: In the Newtonian sense, acceleration would mean put a frame of reference at Earth's center.


20150729: General Relativity & Curved Spacetime Explained!
 00:14: [THEME MUSIC] Newton's and Einstein's dispute over gravity comes down to competing notions of what constitutes an inertial frame of reference.
 00:27: ... Newton says that a frame on earth's surface is inertial, and relative to that ...
 01:11: Today we're finally going to show how curved spacetime makes Einstein's model of the world just as self consistent as Newton's.
 01:18: ... one is to express both Newton's and Einstein's viewpoints in geometric spacetime terms, since that's the ...
 01:51: Let's start with Newton.
 02:03: This captures Newton's idea that inertial observers shouldn't accelerate relative to other inertial observers.
 02:08: ... Newtonian gravity would just be an additional force we introduced, like any other ...
 03:18: OK, Einstein's position is that Newton is making the same mistake as the ant.
 04:27: Now according to Newton, that happens because the apples fall radially instead of down.
 05:09: But then again, so does Newton's flat spacetime picture that has gravity injected as a kicker.
 06:34: And that means game over for Newton.
 06:36: ... and time separately at all, most of the everyday effects on earth that Newton would attribute to gravity are due to curvature in ...
 08:22: So we often think in Newtonian gravitational terms, because it's easier, and because the resulting errors are usually small.


20150722: SPECIAL ANNOUNCEMENT + Flat Spacetime Geometry Comments
 02:58: Remember, in Newtonian physics, there's no unambiguous answer to that question, because you can only talk about motion relative to other things.
 03:22: Those are the guys that, it turns out, corresponds to inertial observers in Newtonian physics.


20150715: Can You Trust Your Eyes in Spacetime?
 01:30: Pretend the world has no gravity, Newtonian or otherwise.
 06:38: In Newtonian mechanics, we distinguish inertial and noninertial observers dynamically by using the floating ball test.


20150708: The Leap Second Explained
 00:30: Thus, in 1960, the second was redefined to be whatever would make the motions of multiple objects in the solar system fit Newton's laws of motion.


20150708: Curvature Demonstrated + Comments
 06:34: ... the curves and vectors in that space mean, and how it helps explain away Newtonian ...


20150702: Can a Circle Be a Straight Line?
 01:21: ... how it lets you account for the motion we observe even if there's no Newtonian force of ...


20150617: How to Signal Aliens
 06:35: ... by the terms "acceleration" an "inertial frame." That means reexamining Newton's first and second laws and so ...
 07:26: ... pointed out that you can distinguish ordinary celebration from real Newtonian gravity, because real gravity will vary in strengths slightly at both ...
 09:42: All directions are equivalent in the absence of some kind of real gravity in the Newtonian sense picking out some direction.


20150603: Is Gravity An Illusion?
 00:00: ... PLAYING] Isaac Newton said that an apple falls because a gravitational force accelerates it ...
 00:18: ... to Isaac Newton, the ground can be considered at rest, Earth applies a gravitational ...
 00:54: OK, bear with me for a minute because we need to begin with some Physics 101 and Newton's laws of motion.
 01:25: ... Newton's laws can't tell you whether a frame of reference is really at rest or ...
 01:34: However, interestingly, Newton's laws can tell you whether your frame of reference is really accelerating or not.
 01:49: Now in Newtonian physics, inertial frames are special because Newton's second law, F equals ma, is only valid in inertial frames.
 02:41: Inertial frame and nonaccelerating frame are synonyms in Newtonian physics.
 03:26: There's something else familiar that makes people, books, and elephants accelerate in lockstep the Newtonian force of gravity.
 05:31: Now in Newtonian physics, this is just an accounting trick that has no broader significance.
 05:49: Now, you know what Newton would say.
 06:29: Well because, Newton says, that frame can't be inertial.
 06:51: Really, Newton?
 07:11: More to the point, Newton, if you're inside the box, there's no way for you to know that you're not in intergalactic space.
 07:59: Now Newton says, nice try, Einstein, but you forgot something Earth is round.
 09:19: It makes several predictions that Newton's theory of gravity does not, and so far, it has passed all its experimental tests.


20150429: What's the Most Realistic Artificial Gravity in SciFi?
 00:53: Whether you want to think of gravity in the Newtonian or the Einsteinian sense, the problem persists.
