Einstein's Greatest Legacy: Thought Experiments

[@BennyEternET]

I guess it is in this context that we can agree with Einstein: "Imagination is more important than knowledge." it is the way of computing in Feynman's scientific method, and yes, it needs verification against experiments.

[@artstrology]

To breathe in from the air is "inspiration' and the opening of the mind to things unknown, it is at this moment, when the "demon" "demonstrates". Fueled by desire, and validated by capacity and integrity. The valve opens.

[@goyonman9655]

Imagination isn't more important than intelligene

[@artstrology]

@@goyonman9655 Only if the desire is to remain static. Imagination makes expansion possible. A simple observation of this, Mendeleev got the periodic table in a dream , not in a lab.

[@mustafakilavuzoglu]

Imagine, all in all it's just Einstein's false imagination that costed humanity priceless and precious "time" of more than a century. Imagine, there is no future, no time no spacetime! I have imagined already and GR married with QM "in no time"... just started to move and count timelesssly, that's all it took and now I believe to possess all the blueprints. If interested, Let's win a Nobel Prize together :)

[@vinayseth1114]

@@mustafakilavuzoglu Then how do you explain general relativity coming in handy when it comes to the working of satellites?

[@EugeneKhutoryansky]

Galileo used thought experiments long before Maxwell or Einstein. And less famous people probably used thought experiments long before Galileo.

[@arctic_haze]

Which ones? I am not denying he did but just can't remember any. However, Newton certainly did use though experiment. He used the Kepler law (consistent with his gravitation theory) to calculate that a satellite at sea level would have a roughly 90 minute period and this requires a force which accelerates its with 9,8 m/s^2 (in modern units) towards the center of the Earth, exactly the gravitational acceleration which Hooke had just measured with pendulums. This showed to him that the gravity we feel and the force which rules the movement of planets are really the same phenomenon.

[@jelmar35]

In a sense, a thought experiment is nothing other than normal reasoning. The distinguishing characteristic seems to be the use of mental imagery and spatial reasoning

[@EugeneKhutoryansky]

@@arctic_haze One example of Galileo's though experiments would be two objects of different masses connected to each other, and falling together. This was to address the question of if objects with more mass fall faster, or if all objects have the same acceleration due to gravity.

[@tTtt-ho3tq]

@@jelmar35 Not mass but weight. There was no Newton, yet. Two objects with the same weight will fall to the ground at the same speed according to Aristotle. So if attach those two objects together as one then that would be heavier than those two and should fall faster, again according to Aristotle. He thought that didn't make no sense. The only way it'd make sense is when every object falls to the ground at the same speed, light or heavier. And he experimented it to prove his thoughts.

[@noeckel]

I agree - and Galileo in particular deserves credit for using thought experiments as a very effective _pedagogical_ tool in his Dialogo. The Wikipedia page on "Thought experiment" has a nice quote from Galileo's "Discorsi e dimostrazioni matematiche" that shows how a thought experiment is used to deliberately construct a paradox.

[@unstablepacifist1672]

I've struggled for years to truly understand deeper physics instead of just sort of understanding. Listening to her explain and along with the graphics have made sparks of understanding bounce around my brain for the first time concerning these topics and it fills me with happiness.

[@frankdimeglio8216]

THE CLEAR UNDERSTANDING OF THE MOTION OF WHAT IS THE MOON AND OF FALLING OBJECTS (AND THE FALLING MAN), AS E=MC2 IS CLEARLY PROVEN TO BE F=MA: Think about the BALANCE of BODILY/VISUAL EXPERIENCE. Consider what is the FULL DISTANCE in/of SPACE AND what is the MIDDLE DISTANCE in/of SPACE IN BALANCE. So, consider the man who IS standing on what is the Earth/ground. Touch AND feeling BLEND, AS E=mc2 IS F=ma; AS ELECTROMAGNETISM/ENERGY IS GRAVITY; AS gravity/acceleration involves BALANCED inertia/INERTIAL RESISTANCE. The EARTH/ground CLEARLY proves ON BALANCE that E=mc2 IS F=ma. Time DILATION ULTIMATELY proves ON BALANCE that ELECTROMAGNETISM/energy is gravity, as E=mc2 IS F=ma. OVERLAY what is THE EYE in BALANCED RELATION to/WITH what is THE EARTH. Notice the black space of THE EYE. The stars AND PLANETS are POINTS in the night sky. THE DOME of a person's EYE is ALSO VISIBLE. Now, carefully consider what is the semi-spherical, translucent, QUANTUM GRAVITATIONAL, AND BLUE SKY. Gravity IS ELECTROMAGNETISM/energy, as E=mc2 IS F=ma. SO, gravity AND ELECTROMAGNETISM/energy are linked AND BALANCED opposites. This NECESSARILY represents, INVOLVES, AND, DESCRIBES what is possible/potential AND actual IN BALANCE. Accordingly, TIME is NECESSARILY possible/potential AND actual IN BALANCE; as E=mc2 IS F=ma; AS ELECTROMAGNETISM/ENERGY IS GRAVITY. The Sun is E=mc2 AND F=ma. Very importantly, outer "space" involves full inertia; AND it is fully invisible AND black. So, E=mc2 AS F=ma clearly requires and involves invisible AND VISIBLE SPACE in fundamental equilibrium AND BALANCE; as ELECTROMAGNETISM/ENERGY IS GRAVITY. (The EARTH is ALSO BLUE, as it CLEARLY proves ON BALANCE that E=mc2 is F=ma.) ACCORDINGLY, the MIDDLE DISTANCE in/of SPACE AND the FULL DISTANCE in/of SPACE are NECESSARILY LINKED and BALANCED; as E=mc2 IS F=ma; as ELECTROMAGNETISM/energy is gravity. Great. Therefore, INSTANTANEITY is thus FUNDAMENTAL to what is the FULL and proper UNDERSTANDING of physics/physical experience; as E=mc2 IS F=ma; as ELECTROMAGNETISM/ENERGY IS GRAVITY. THE EYE is the body ON BALANCE, as E=mc2 IS F=ma. INDEED, the balance of being AND EXPERIENCE is essential. (BALANCE and completeness go hand in hand.) SO, objects (including what is the falling man) fall at the SAME RATE (neglecting air resistance, of course); as ELECTROMAGNETISM/energy is gravity; as E=mc2 IS F=ma. Indeed, gravity/acceleration involves BALANCED inertia/INERTIAL RESISTANCE; as ELECTROMAGNETISM/energy is gravity. Great. Therefore, the rotation of WHAT IS THE MOON necessarily matches it's revolution; as E=mc2 IS F=ma. "Mass"/ENERGY IS GRAVITY. ELECTROMAGNETISM/energy is gravity. The Earth AND the Sun are linked AND BALANCED opposites, AS E=mc2 IS F=ma; AS ELECTROMAGNETISM/energy is gravity. Great. Therefore, the rotation of WHAT IS THE MOON NECESSARILY matches it's revolution. Great. E=mc2 IS CLEARLY proven to be F=ma !!!! The stars AND PLANETS are POINTS in the night sky. A PHOTON may be placed at the center of what is THE SUN (as A POINT, of course), AS the reduction of SPACE is offset by (or BALANCED with) the speed of light; AS ELECTROMAGNETISM/ENERGY IS GRAVITY; AS E=mc2 IS F=ma. GREAT !!!!! The EARTH and the Sun constitute and comprise the MIDDLE AND THE FULL DISTANCE in/of SPACE (IN BALANCE) in full and BALANCED compliance and conformity with the CLEAR and universal fact that E=mc2 IS F=ma, AS ELECTROMAGNETISM/ENERGY IS GRAVITY. Great !!!!!! Hence, it is CLEARLY proven, in fact, that the rotation of WHAT IS THE MOON NECESSARILY matches it's revolution. Great. Obviously, what is THE MOON is subject to and constitutive of both E=mc2 AND F=ma. E=mc2 IS CLEARLY proven to be F=ma. "Mass"/energy involves BALANCED inertia/INERTIAL RESISTANCE consistent with/as what is BALANCED electromagnetic/gravitational force/ENERGY, AS ELECTROMAGNETISM/ENERGY IS GRAVITY; AS E=mc2 IS F=ma. The following constitutes even further proof of the fact that ELECTROMAGNETISM/energy is gravity. Very importantly, in dream experience, BODILY/VISUAL EXPERIENCE is invisible AND VISIBLE IN BALANCE. Dream experience is/involves true/real QUANTUM GRAVITY, as ELECTROMAGNETISM/energy is gravity; as E=mc2 IS F=ma. By Frank DiMeglio

[@kickbuttowski8201]

you know what , what ever you are saying is also a thought experiment MARY'S thought experiment

[@pohujwamtoniepodajski8936]

yea something about the formula was so spot on ... had the same

[@13krava]

3:06 excellent hand-arrow coordination 😁

[@pumbaa667]

AHAH, I didn't catch it, you made me rewatch it and laugh hard.

[@pumbaa667]

Kudos to the video editor it's not his first demonstration of greatness.

[@RalphDratman]

This video is really excellent, Sabine. You pulled all of those facts together in a way that made clear sense to me. You are a wonderful teacher. Thank you!

[@KeithCooper-Albuquerque]

Sabine, this was a great video and once again points to Einstein's great mind as being mind-blowingly fascinating. Great dress as well.

[@SabineHossenfelder]

Happy you like it!

[@RalphDratman]

I am not going to reply to this comment and I strongly suggest no one else reply to this either, otherwise this commenter will deflect the whole section. It was my mistake to post the first reply (which I have deleted) and I apologize to the group for doing so.

[@AndrewBlucher]

@@SabineHossenfelder Either the camera was slightly tilted, or you were. Are you well? Great video as always. I notice many commenters have missed a key point about Einstein's thought experiments: that they explored the boundaries. Others did grasp the concept. There is a fine line between modern physics and classical philosophy.

[@krisspkriss]

Love the dress.

[@oceanlawnlove8109]

@lol haha she really is fashionable tbh I look up to older, well dressed women who have something to say

[@Salvoran]

Irgendwie "organisch"... wie der Einsteinturm in Potsdam. (Zitat: Einstein)

[@tarmaque]

@@oceanlawnlove8109 She's younger than me, and I still look up to her. 🤣

[@MrDorbel]

I wonder if she makes them herself, they are always interesting and quirky.

[@XMickyMouseX]

And the sepia coloured tone matches the background so nicely!

[@grokeffer6226]

Necessity might be the Mother of Invention, but I'm thinking Imagination must be the Daddy.

[@MichaelPohoreski]

_Necessity is the Mother of Invention but Curiosity is the Father_

[@theultimatereductionist7592]

+Grok Effer That is why I HATE all the assholes who NEVER did the hard discipline of REAL ABSTRACT MATHEMATICS bashing imagination, creativity, mathematical modeling, computer simulation & computation. They FALSELY delude themselves into thinking they are being so "practical" by YAMMERING on about "physical experiments only", TOO STUPID to comprehend that RAW DATA ITSELF DOES NOT PROVE ANYTHING: that PROOF & PROVING THINGS & COMING TO CONCLUSIONS is an ABSTRACT MENTAL PROCESS, NOT A PHYSICAL ONE, EVEN IF THE ABSTRACT PROCESS MUST REFERENCE PHYSICAL DATA.

[@grokeffer6226]

@@theultimatereductionist7592 Oddly, I understood this, and I think I agree. Math was always my least proficient subject in school, but I've always found this sort of thing interesting.

[@grokeffer6226]

@Ana Blaque HaHa !! I say silly things sometimes to cover the fact that I can't really contribute anything else to the conversation.

[@simran3366]

Can't wait to hear u on PBS spacetime theory of everything webinar, Sabine!!!!!

[@LeoStaley]

Wait what??

[@justg2310]

Thanks for the info! I’ve been looking for this!

[@Tripskull]

Wait what? You were on SpaceTime? My 2 favorite physicists!!

[@ytpadyt]

3:31 just wait certain time and you know for sure wheter you are pulled by gravity or pulled up with constant acceleration..

[@manucitomx]

Thank you, again, for a fantastic explanation. This is of the best science channels on KZbin.

[@mydogbrian4814]

- Who is your tailer? - Thanks once again for your enlightening spin on a physics subject. - However, loss of information is not a problem. I can demonstrate it in my daily thought experiments dealing with my day to day reality. - I would expand on the subject but the cerebral energy necessary to recall that information appears to have been lossed somewhere along the way. I think it evaporated!

[@Garybutonline]

I have problems and so the outfits help me pay attention, and the accent helps me retain the information. Wish you were my lecturer.

[@stevenkelby2169]

She is, in a way!

[@DannyFarnsworth]

Your animations are wonderful. They clearly illustrate what you're saying without distracting.

[@dashxdr]

The downward arrows moving in sync with your hands was a nice touch.

[@TheEulerID]

I was puzzled with the title of this video and immediately thought of Maxwell's daemon, even though the principle of though experiments goes back much longer than that, to at least the ancient Greeks (indeed, it was the only sort of experiment they did like). Einstein might have been the greatest practitioner, but I don't think thought experiments are his legacy in particular.

[@baruchben-david4196]

Good point. I think that the important factor is that the gedanken must be confirmed by experiment; or perhaps more accurately, experiment must not falsify the gedanken.

[@Bestape]

I think they key is measurement. Sometimes new measurement is a more accurate (higher resolution) measurement of a known phenomenon. Sometimes new measurement describes a new phenomenon. I think Einstien explored both types of measurement.

[@RWin-fp5jn]

Good Point ! We should not overrate the importance of thought experiments ; Yes, they can be very useful to extend human theories and detect logical inconsistencies. However, nobody (not even Einstein) can derive Universal laws or truths from them, because that’s equivalent to implicitly saying that our human mind is so all-knowing that it can replace Nature itself as a laboratory for conducting experiments. Point and case: Einstein correctly noticed a contradiction with his EPR paradox leading to the concept of time instant quantum entanglement. However, in his human hubris, he crossed the line when he concluded on this basis that QP must be wrong. He never considered that his spacetime physics could be incomplete in stead. In the early 1970's Bell’s inequality theorem tests PROVED quantum entanglement is actually very real and that Einstein's critique on QP was WRONG. This should have provided a stern warning to all modern physicists that you cannot deduct 'universal truths' from mere 'human thought experiments'. But rather than admitting INSTANT influence is indeed possible, posing a problem for C (or any other spacetime speed for that matter), our top physicists persist that 'all is well' by adopting the most flimsy excuse stating: ‘…Yess,..well,..OK, …, so entangled particles DO influence each other instantly, but we consider this influence as being non-information, therefore it is nothing, therefor it is still true that ‘nothing exceeds C….’ . Tsss, that’s playing with words and semantics like we were lawyers. What a bad losers we are….If anything, the Gedanken Experiment proves how fallible we humans are, how reluctant we ar to let go of our assumptions and pre-conditions and how incomplete spacetime physics itself is....Are we really going to waste another 100 years sticking to our failures?

[@frankdimeglio8216]

@@baruchben-david4196 ON THE ABSOLUTE PHYSICAL EQUIVALENCY AND BALANCING OF E=MC2 AND F=MA: It is a very great truth in physics that the ability of thought to DESCRIBE OR reconfigure sensory experience is ULTIMATELY dependent upon the extent to which THOUGHT IS SIMILAR TO sensory experience, AS E=mc2 IS F=ma; AS ELECTROMAGNETISM/ENERGY IS GRAVITY. (THOUGHTS ARE INVISIBLE.) INDEED, E=mc2 IS DIRECTLY and fundamentally derived from F=ma; AS time dilation proves that electromagnetism/ENERGY IS GRAVITY. Therefore, ultimately and truly, time is possible/potential AND actual IN BALANCE; AS ELECTROMAGNETISM/ENERGY IS GRAVITY. In fact, INSTANTANEITY is FUNDAMENTAL to the FULL and proper understanding of physics/physical experience; AS ELECTROMAGNETISM/ENERGY IS GRAVITY. THE stars AND PLANETS are POINTS in the night sky. A PHOTON may be placed at the center of what is THE SUN (as A POINT, of course), AS the reduction of SPACE is offset by (or BALANCED with) the speed of light; AS ELECTROMAGNETISM/ENERGY IS GRAVITY. E=mc2 IS F=ma. GREAT !!! BALANCE AND completeness go hand in hand. It all CLEARLY makes perfect sense. (Very importantly, outer "space" involves full inertia; AND it is fully invisible AND black.) The INTEGRATED EXTENSIVENESS of THOUGHT (AND description) is improved in the truly superior mind. Gravity IS ELECTROMAGNETISM/ENERGY. By Frank DiMeglio

[@bobaldo2339]

Maxwell's little demon also needed to consume energy in order to man the gate - whether this be in the form of Big Macs or Information Burgers.

[@nicklaskowalski]

That’s a hell of a t-shirt!! Looking rather “pre-historic” especially with the cave-like background. Love it actually!

[@arctic_haze]

Well done. I would not believe this all could be explained in 7 minutes.

[@ataru4]

Great video. Before I studied physics I misunderstood what made Einstein a genius, like most people I think. After reading his original work I realised it wasn't so much what he thought but how he thought.

[@Petticca]

@Asa And this was something Einstein himself seemed to realise. I recently read a talk he had given where he stressed the importance of understanding *how* the great thinkers of the past thought. He seemed to consider it more important than merely learning about what they discovered. I think it's evident he was not completely wrong if we look at theoretical physics today. I can't help but draw comparisons to historical views where it took a change in perspective to progress; these came after many years of physicists, incorrectly, invoking all kinds of phenomena that *must* exist, because the data /model shows it. In conversation Einstein had said that (my words, not his) essentially he felt the direction quantum physicists were heading was going to leave them stuck spinning their wheels as they needed to change how they were looking at what they were discovering. While he felt that ultimately his view of how the universe worked would be required in order to truly understand quantum physics, he acknowledged he didn't think he was approaching it in the right way as he worked to reconcile things. The more I learn about Einstein's way of looking at things, the more I am convinced he was not wrong in his view on the importance of understanding how to look at things matters more than what we think we know about things.

[@ryanwarren219]

Thank you for this and all your videos! They are helping me understand topics that I’ve been curious about and puzzled by for a long time.

[@dennistucker1153]

Excellent video! Thank you Sabine.

[@dkenmiller9829]

Beauty and smart co-existing. I am impressed past my 75 years. Thank you Sabine!

[@wholenutsanddonuts5741]

Also, opening the door requires work (at least in any realistic scenario). Adding work to reduce local entropy increases universal entropy so no law is broken.

[@msw0011]

Hello there Sabine. Excellent presentation, thank u.

[@alexandreramos8484]

Your visuals are so great!

[@StanTheObserver-lo8rx]

On PBS space time,you were one of the main topics today. To condense it,they say they dont waste time on "beautiful theories since no telling if they are right or wrong". A couple wanted a piece of you!..lol. They said they are looking forward to the next episode when you will be the star. I hope they meant Space Time and not some podcast we will never see.

[@jc7636]

Cheers Sabine, love your videos.

[@peternolan814]

Hello Sabine, I first read the word gedanken in Feynman's three volume Lectures On Physics when I was still in school aged 16 to 18 1969 to 1971 when I had that three volume set that I still have to this day. Feynman's own gedanken experiment was for electrons passing between two slits. Peter Nolan. Ph.D.(physics). Dublin. Ireland.

[@bobbygautam3950]

Underrated channel should have more subs

[@marcus72ch2]

Again a very interesting Video. Great, I‘m always waiting impatiently for the next one to show up

[@rosman2635]

Einstein provided us with so much information of what cannot be observed.

[@blahblahsaurus2458]

I've heard plenty of people talk about general relativity being incompatible with quantum mechanics, but this is the first time I've heard an actual example of how, thanks!

[@paolomilanicomparetti3702]

It's not just Einstein's equivalence principle that stems from a thought experiment, but also Galileo's. He had a thought experiment about two objects, one light and one heavy, falling together, tied to one another, to demonstrate that all objects fall just as fast.

[@rclrd1]

Also Galileo: you can't tell whether is ship is moving or docked by doing experiments in an enclosed cabin. That is the essence of "Relativity"!

[@otiebrown9999]

An outstanding presentation of the concept of the, Thought Experiment.

[@hyperduality2838]

"By imagination and reason we turn experience into foresight" -- Spinoza.

[@treyquattro]

so good! You make everything seem so straightforward. Superb pedagogy

[@vinko8237]

What about Galilei (friction, inertia) and Newton (imagine a projectile faster and faster)? Didn't they also get to their achievement using thought experiments? Anyway it's cool they are still used even in the modern physics, maybe even more now when theories are harder and harder to be tested. Thank you for your concise depth in every your video! You really put some... thought in it!!!

[@hipphipphurra77]

When Einstein once was asked for his laboratory he showed his pen.

[@Alexagrigorieff]

@Bertrand de Born [citation needed]

[@Alexagrigorieff]

@Bertrand de Born And that constitutes "so much is wrong waht he said"?

[@Alexagrigorieff]

@Bertrand de Born So he was sometimes wrong about something. Which part of Special or General relativity, or his other scientific accomplishments it invalidates?

[@Alexagrigorieff]

@Bertrand de Born Last time I checked, currently accepted formulas for SR time dilation do indeed have c+v and c-v terms. So what's your point? Many SR formulas include 1/sqrt(1-v^2/c^2) term, which you can rewrite as c/sqrt((c+v)(c-v))

[@Alexagrigorieff]

@Bertrand de Born It seemed you're having a problem with Einstein using c+v term. Why is that?

[@kunai9809]

My favorite thought experiment i have from a friend of mine: Suppose the sun just disappeared. Like, completely. At once. What would we notice here at earth, and when? Light from the sun needs about 8 minutes to reach the earth, so it would still be totally normal here regarding daylight for another 8 minutes. What about gravity though? Would earth just instantaneously leave it's orbit around the former sun? Well, wouldn't that violate the law that information cannot travel further than the speed of light?` From here it's just my own thinking. I think it would violate it. So consequently, earth would orbit around _nothing_ for another 8 minutes and Pluto would continue it's curve around the void for more than 5 hours. So the gravitational information must somehow travel from the sun to the planets...as waves? My question is: have I just derived gravitational waves??

[@markusperscheid4278]

Good video. The entanglement breaks down the time, in which it runs, when it is measured, to the time in which the measurement is made. Different time scales and what it is inside, can live together, with no interactions? And the daemon does he have a mathematical function.

[@Scrogan]

Neat! There are plenty of interesting thought experiments out there, especially around the counter-intuitive nature of quantum physics.

[@hughbarton5743]

A gorgeous explanation on Maxwell's Demon.....thanks as always.

[@datapro007]

Great video, Sabine. I very much enjoy your series. Thanks.

[@DocBree13]

Physics was never my strength, so I will appreciate any feedback about a couple of questions. 1) Maxwell’s demon: wouldn’t the demon be doing work? If so, would that not be sufficient to explain the decreased entropy? Wouldn’t that also preclude the experiment to being tantamount to a perpetual motion machine? 2) Einstein’s elevator: when we stand on the Earth, we experience a constant attraction to the Earth. That attraction is not increasing at a constant acceleration as in a free fall to the Earth from an elevation. So wouldn’t the appropriate elevator just rise at a constant velocity instead of constant acceleration? 3) Hawking radiation: what is meant by loss of information in this sense? If the mass and energy that were absorbed by the black hole could never escape it, wouldn’t that also constitute loss of the information? How is loss via degradation/radiation different than loss due to permanent sequestration? thank you in advance to any physics fans who help me understand these :)

[@LaPhysiqueaveclesMains]

Somebody may have mentioned that already, but actually, the very first known thought experiment in the history of Physics was made by Galileo. This is how he inferred the fact that all objects should fall at the same speed in a vacuum regardless of mass. His reasoning was to consider a large, massive object, mentally cut it in two parts, and dropping it: how should the parts fall compared to the whole solid ? What if the parts were linked with a rope ? It is precisely these thought experiments that drove him to experimenting on the free-fall of objects for real. Some would argue that thought experiments were conducted by Aristotle as well, which in a way is true, but Aristotle's "discovery" process cannot be associated with what we nowadays define as the Scientific Method. Therefore, his reflexions cannot really, in my views, be viewed as thought experiments, at least not in a modern sense. Thank you for the video !

[@kachetofes]

I absolutely loved your book, and there are no words to describe how excited I am for your appearance on PBS spacetime! Eric Weinstein seems to share your criticism regarding the state of theoretical physics, and I'm super excited to hear Lee Smolins and your take on his ideas of spin networks that are similar to Smolins.

[@apokaya11]

Information loss paradox is not the problem of The General Theory of Relativity. It squarely falls onto Quantum Fields Theory which argues for the conservation of the information, not the former theory? And also as a personal note, sitting on a tram in circa 1905 and looking back to the watchtower and postulating: what if I move away from that watchtower at the speed of light and then dropping the bombshell Special Theory in which you can travel in time (proven more than 50 years later) such a giant paradigm leap. That is the craziest thought experiment I have ever heard and deserves a special recognition.

[@martinackermann2821]

Sein bekanntestes Gedankenexperiment war das "Zugexperiment", bei dem er die "Relativität der Zeit" quasi am Dopplereffekt der Lichtgeschwindigkeit erklärte, der sich ferner sogar an der Rotverschiebung des Lichtes - fernster Galaxien - bewies. Im Zuge der dabei aber spätestens erkannten Widersprüche, zur Absolutheit der LG, verzichtet man indessen auf seinen Gedankenzug-Klassiker.

[@xk1390]

It's nice to see such a pragmatist like Sabine exaggerating. General Relativity is arguably a more important legacy of Einstein's.

[@alamagordoingordo3047]

Always so intresting and clear.

[@CodeShudder]

I'm wondering about the period between EPR and Bell's experiment. Hidden variables seemed like simple, elegant explanation making Bohr's theory look crazy. I've learned that even Bell was leaning towards EPR. What was so significant in Copehagen interpretation (uncertainty principle) that outweighted this Occam's razor of hidden variables so that there was a need to test which is true? It must've explained something that other theories couldn't, but I don't know what it was.

[@Chuttanooga]

Highly competent explanation in best Raider outfit.

[@frankdimeglio8216]

Frank DiMeglio is RECOGNIZED as having mathematically unified physics.

[@frankdimeglio8216]

THE CLEAR UNDERSTANDING OF THE MOTION OF WHAT IS THE MOON AND OF FALLING OBJECTS (AND THE FALLING MAN), AS E=MC2 IS CLEARLY PROVEN TO BE F=MA: Think about the BALANCE of BODILY/VISUAL EXPERIENCE. Consider what is the FULL DISTANCE in/of SPACE AND what is the MIDDLE DISTANCE in/of SPACE IN BALANCE. So, consider the man who IS standing on what is the Earth/ground. Touch AND feeling BLEND, AS E=mc2 IS F=ma; AS ELECTROMAGNETISM/ENERGY IS GRAVITY; AS gravity/acceleration involves BALANCED inertia/INERTIAL RESISTANCE. The EARTH/ground CLEARLY proves ON BALANCE that E=mc2 IS F=ma. Time DILATION ULTIMATELY proves ON BALANCE that ELECTROMAGNETISM/energy is gravity, as E=mc2 IS F=ma. OVERLAY what is THE EYE in BALANCED RELATION to/WITH what is THE EARTH. Notice the black space of THE EYE. The stars AND PLANETS are POINTS in the night sky. THE DOME of a person's EYE is ALSO VISIBLE. Now, carefully consider what is the semi-spherical, translucent, QUANTUM GRAVITATIONAL, AND BLUE SKY. Gravity IS ELECTROMAGNETISM/energy, as E=mc2 IS F=ma. SO, gravity AND ELECTROMAGNETISM/energy are linked AND BALANCED opposites. This NECESSARILY represents, INVOLVES, AND, DESCRIBES what is possible/potential AND actual IN BALANCE. Accordingly, TIME is NECESSARILY possible/potential AND actual IN BALANCE; as E=mc2 IS F=ma; AS ELECTROMAGNETISM/ENERGY IS GRAVITY. The Sun is E=mc2 AND F=ma. Very importantly, outer "space" involves full inertia; AND it is fully invisible AND black. So, E=mc2 AS F=ma clearly requires and involves invisible AND VISIBLE SPACE in fundamental equilibrium AND BALANCE; as ELECTROMAGNETISM/ENERGY IS GRAVITY. (The EARTH is ALSO BLUE, as it CLEARLY proves ON BALANCE that E=mc2 is F=ma.) ACCORDINGLY, the MIDDLE DISTANCE in/of SPACE AND the FULL DISTANCE in/of SPACE are NECESSARILY LINKED and BALANCED; as E=mc2 IS F=ma; as ELECTROMAGNETISM/energy is gravity. Great. Therefore, INSTANTANEITY is thus FUNDAMENTAL to what is the FULL and proper UNDERSTANDING of physics/physical experience; as E=mc2 IS F=ma; as ELECTROMAGNETISM/ENERGY IS GRAVITY. THE EYE is the body ON BALANCE, as E=mc2 IS F=ma. INDEED, the balance of being AND EXPERIENCE is essential. (BALANCE and completeness go hand in hand.) SO, objects (including what is the falling man) fall at the SAME RATE (neglecting air resistance, of course); as ELECTROMAGNETISM/energy is gravity; as E=mc2 IS F=ma. Indeed, gravity/acceleration involves BALANCED inertia/INERTIAL RESISTANCE; as ELECTROMAGNETISM/energy is gravity. Great. Therefore, the rotation of WHAT IS THE MOON necessarily matches it's revolution; as E=mc2 IS F=ma. "Mass"/ENERGY IS GRAVITY. ELECTROMAGNETISM/energy is gravity. The Earth AND the Sun are linked AND BALANCED opposites, AS E=mc2 IS F=ma; AS ELECTROMAGNETISM/energy is gravity. Great. Therefore, the rotation of WHAT IS THE MOON NECESSARILY matches it's revolution. Great. E=mc2 IS CLEARLY proven to be F=ma !!!! The stars AND PLANETS are POINTS in the night sky. A PHOTON may be placed at the center of what is THE SUN (as A POINT, of course), AS the reduction of SPACE is offset by (or BALANCED with) the speed of light; AS ELECTROMAGNETISM/ENERGY IS GRAVITY; AS E=mc2 IS F=ma. GREAT !!!!! The EARTH and the Sun constitute and comprise the MIDDLE AND THE FULL DISTANCE in/of SPACE (IN BALANCE) in full and BALANCED compliance and conformity with the CLEAR and universal fact that E=mc2 IS F=ma, AS ELECTROMAGNETISM/ENERGY IS GRAVITY. Great !!!!!! Hence, it is CLEARLY proven, in fact, that the rotation of WHAT IS THE MOON NECESSARILY matches it's revolution. Great. Obviously, what is THE MOON is subject to and constitutive of both E=mc2 AND F=ma. E=mc2 IS CLEARLY proven to be F=ma. "Mass"/energy involves BALANCED inertia/INERTIAL RESISTANCE consistent with/as what is BALANCED electromagnetic/gravitational force/ENERGY, AS ELECTROMAGNETISM/ENERGY IS GRAVITY; AS E=mc2 IS F=ma. The following constitutes even further proof of the fact that ELECTROMAGNETISM/energy is gravity. Very importantly, in dream experience, BODILY/VISUAL EXPERIENCE is invisible AND VISIBLE IN BALANCE. Dream experience is/involves true/real QUANTUM GRAVITY, as ELECTROMAGNETISM/energy is gravity; as E=mc2 IS F=ma. By Frank DiMeglio

[@cyruskalali8222]

I just discovered Sabine. It is the discovery of the century.

[@RosssRoyce]

The difference between how Gravity and Accelleration in a rising elevator affect a mass is that the Elevator affects the mass in a chain reaction pushing from the ground, through knees, hips, spine..up, compressing the mass. While Gravity affects the whole mass’ building blocks at once, not through compression or chain reaction leverage.

[@SB-pq9dd]

Great and Nice Channel... Extremely Useful... Thank You!

[@ovdtogt1]

The embedded 'information' is the ability to remain each other's opposite even after these properties have been undefined for any period of time.

[@williambunting803]

This is a truly exciting period in science, closing in on the ultimate secrets of energy and matter. So many great minds exploring the many aspects of nature at this level. Every idea and opinion represents a life dedicated to learning, research, pondering, experimenting, calculation, and debate. In a world awash with money, it is truly sad that science has to go begging for the funds drive the research forward.

[@TheNameOfJesus]

The Maxwell's Demon story is a fascinating gedankenexperiment. I think I see your explanation, but it's still profoundly interesting. Perhaps the relationship between information (I) and entropy (E) can someday be put into a formula, like I = E c^2.

[@MCsCreations]

Really interesting! Thanks a lot! 😊

[@stridedeck]

I'm in total agreement with thought experiments! Here are two that will lead to insights: What will be the economic result if all labor is free (not caring if people are motivated to work)? The other thought experiment is: What if all movement is not created within, but comes from an outside source?

[@paskal007r]

hi, there's actually a thought experiment from Galileo Galilei, with two rocks tied with a rope, that he used to prove wrong the previous theories of freefall speed being proportional to an object's weight.

[@michaeljorgensen790]

I have a question about a thought experiment about possible trajectories of matter into and out of the photon sphere of a black hole. Years ago a Professor explained to the class that there is a region near the event horizon where ordinary matter (atoms) could not pass through and make it back out of the photon sphere intact. This had to do with an increase in relativistic mass. Trajectories had to be calculated using the Schwarzschild Metric (Combination of General Relativity and Special Relativity) for calculating gravity at any particular point and not just General Relativity alone. So you get to a point where anything with mass passes a point of no return and this point is above the event horizon. Most people think that "classical" general relativity alone works all the way up to the event horizon and if you have engines to change your trajectory you can get back out as long as you don't cross into the event horizon. Susskind touched on this region below the photon sphere in a lecture but he did it with massless photons. I'm trying to find a video of a professor explaining relativistic mass increase in this region and why exactly you reach a point where you can go down and not up. That professor explained that even trying to move in any upward direction would increase your relativistic mass as fast as you can apply any force and the best you could hope for was to just arrest your inward (downward) movement. And near the event horizon if you arrest your inward movement you are still moving relative to that visualization of space or space-time flowing inward toward the event horizon. SR introduces a non linear quality that shows that it is not just velocity that can effect relativistic mass but also gravity itself can effect relativistic mass. Does anyone know of a lecture about this?

[@parthabanerjee1234]

Dear Sabine, I am glad that you pointed out how crucial Gedankenexperiment is to theoretical physics. Aber dafür muss man einen Kopfkino und eine Zwangsjacke haben.

[@DallasPhool]

An evaporating black hole doesn't destroy information, it simply emits it in very low frequency gravitational waves, General relativity means that time, distance, mass, and energy are all equivalent and are only separated in "local" regions.

[@rayfleming2053]

Einstein imagined that non-physical space has physical dimensions and clocks. Then he imagined imaginary dimensions and clocks could be changed by the motion of an observer or the presence of stable matter through imaginary mechanisms. From this he developed imaginary special and general relativity theories. We need to start over with the true physical origin of dimensions and clocks, the wavelengths and frequencies of the quantum field in order to develop true physical theories of relativity and general relativity.

[@eismscience]

Thank you for pushing this idea, Sabine! So many people do not appreciate it.

[@thomasjackson9993]

You are a beautiful person, and I really appreciate your lectures. Thank you for your work.

[@skeltek7487]

Particles are entangled along the whole path until measurement. Measuring one particle let’s the second stay entangled until measured. The relativity of simultaneousness does not permit a judgement on which particle has been measured first.

[@py8554]

Schrödinger's cat, a thought experiment that Einstein helped create, was not mentioned. Perhaps it’s because it is more famous than EPR experiment or Black hole information loss paradox?

[@einsteindrieu]

Experiments & Devices -That's what I say to Sabine !-Good video.

[@1Clavdivs]

There is a name for people who do "thought experiments" : mathematicians.

[@thebeelight]

wonderful topic and great content!

[@notdone1975]

All of your explanations are so clear and easy to grasp, thank you?

[@SabineHossenfelder]

Thanks for the feedback! Happy you find my videos useful!

[@jacksourlis4151]

Regarding the elevator scenario, what if you put flashing lights in the elevator equal distance from Alice who is in the elevator also just as she was on the train in the big think video.

[@jamesdolan4042]

I always thought that space-time as a fabric was a thought experiment used to describe General Relativity. However, since Gravitational Waves in space were detected/discovered a Space-time fabric is indeed an actual possibility.

[@gdsandkes]

What is also remarkable, and I believe indicative of a deeper truth, is that we even have this ability.

[@owenmartin3307]

One can very easily verify whether the elevator is moving or not by checking if there is a force on it, and if so you will feel the vibrations inside.

[@AllenMorrisColonel]

Thank you for your efforts.

[@jelly-johnbobster2283]

Thank you, Sabine!

[@zagaberoo]

Looking forward to hearing you speak at the PBS symposium.

[@ianalanneilgrant4626]

2:45 I am not sure about the characterization of information and entropy. It needs to be handled carefully because there is an important distinction we have make between actual data, and the information that is supposed to _represent_ that data. The difference is that the information has to be interpreted in some context to yield actual knowledge of the data, in this example the data is the position and velocity of the molecules in the gas. The information from which we _infer_ the underlying data is highly abstract. It may be measurements of voltages from some optical sensor in an interferometer looking at light, or electrons or something which we assume is reflected from the molecules of the gas in a certain region around the aperture. The interpretive context from which we infer the data then includes all the theories we use which underlie the correct operation of the various pieces of measurement apparatus we develop in order to be able to carry out the experiment. So the underlying ontology emerges from the interaction of all this constantly changing technological development, and that inferred reality is what we call the actual data. Then the Shannon information is a quantity we calculate from the assumption that our measurement apparatus will only ever produce information of that particular form. In that sense the Shannon information assumes some particular generating process, called an _information source._

[@ianalanneilgrant4626]

The thing is that the distribution of the positions and velocities in the gedanken experiment is assumed to be due to an opaque source, in the sense that there is nothing we could know about the source that would enable us to guess with better than a random chance of being correct. Now if you assume that as the basic condition of the Universe at the time of the Big Bang, then ... well, you don't leave much room for other ideas about how mind or life could have been realized. For some this is not a problem, but for others, like Richard Dawkins, it becomes a religious dogma that you have to defend like a zealot.

[@armyofshea7941]

I love thought experiments. Use them daily, though not in the physics world. Not quite that smart. However, anytime you are about to share knowledge, wisdom, or guidance with others (ie: conference call or briefing) I suggest you first conduct your own thought experiment about how the conversation will go. Consider your audience, your experience and bias, their experience and bias, then tailor what you will say. It makes a huge difference.

[@hansolafsen77]

Has the actual EPR experiment with position and momentum been conducted or just those with other non-commuting quantities like spin and Stern Gerlach magnets cobstituing the "common past"?

[@mikegale9757]

Here's a new twist on a famous thought experiment called the Andromeda paradox. What's the difference between throwing a clock at a wall and throwing a wall at a clock? The last reading on the clock before it breaks is going to be different in each case and the Twin Paradox teaches us that "feeling the force" breaks the symmetry. But it begs the question as to why the clock's perception of "now" over there is valid in one case and not the other. I contend that a "now" moment is a spacetime event like any other so it's objective reality begins when light is emitted, absorbed or reflected. It has nothing to do with one's lines of perceived simultaneity. No amount of cycling or rocketeering is going make the light go back where it came from so Brian Greene's spacetime loaf and Einstein's persistently stubborn illusion are both bunk. The past is a done deal and the future is uncertain. I think we should make that an axiom of physics to avoid getting bogged down with misapprehensions in our future endeavours. If your theory permits time travel into the past (i.e. light going backwards in time), then it is most certainly wrong.

[@TheEDNC]

Brilliant presentation Thank you.

[@sanjj_1]

loved this video !!!!

[@MilosMalinic]

Please explain why "we don't know until we measure it" is such a problem in quantum mechanics. Why the statement "the system is already set, but we don't know how until we measure it" is wrong (is it?) in the entanglement experiment?

[@ovdtogt1]

The demon requires energy: it would raise the entropy as much as it would lower it. So no change in entropy occurs. All systems that lower entropy also raise entropy and that includes information.

[@Tmidiman]

Hi Sabine, Im really enjoying your presentations. Have you ever covered time travel? I’ll search your previous videos.

[@br3nto]

What is meant by “information” when referring to no useful information transferred between entangled particles and information being destroyed when black holes evaporate via Hawking radiation?

[@lopantolulu]

4:21 jada also experiment with entanglement,mostly with august

[@paulkarch3318]

Stories may be true or false. Story is that one time a reporter asked Einstein: "How can time flow at different rates at different places?" Einstein replied: "If you spend 5 hours with a pretty girl it's like 5 seconds; if you spend 5 seconds sitting on a hot stove it's like 5 hours." Although I am almost totally ignorant regarding physics, I recommend watching Roger Penrose's videos. I'm not trying to put words in his mouth but he makes some pretty good points: 1. If you look at the microwave background, which comes from the big bang, you see the traditional black body radiation however this indicates a state of maximum entropy; the cosmologists are asserting that the entropy increases from a maximum. 2. Information is lost in black holes and black holes account for most of the entropy in the universe. 3. When all the black holes evaporate, the universe will be made up of photons and that means there is no distance and no time. 4. This state will blossom forth into a new big bang.

[@duelmonitor]

@Sabine Hossenfelder Any chance you could cover the subject of bohmian mechanics (aka pilot wave theory)? Could the wave be a result of no/low mass particles being influenced by the bending of the space around the particle much like a boat in water could be influenced its own wake created by the ripples in water? Could this bending of space around particles be the quantum version of gravity?

[@michaelblacktree]

IIRC, Plato was also a big proponent of thought experiments.

[@sadface7457]

That was is an philosophical context not a physical context

[@LuisAldamiz]

@@sadface7457 - There's only some blurry division between philosophy and science. In fact "philosophy" was how the ancients called what we now call "science" (originally science, scientia means "wisdom" in Latin, while philosophy means "love of wisdom" in Greek). They just had worse means in general than we do. Plato is sadly a reason why "philosophy" acquired a more speculative meaning, mostly via Christian Neoplatonics, who were actually not very interested in science at all but in pseudoscientific wishful thinking.

[@rclrd1]

@@sadface7457 No clear distinction. What we now call "science" used to be called "natural philosophy".

[@michaelblacktree]

One could also argue that modern science still has some philosophical aspects, as well.

[@JustaReadingguy]

Love your stuff. Thanks.

[@odizzido]

In regards to the demon, assuming you extract some of that energy to do work the kinetic energy of those atoms would decrease would they not? Sure you could keep separating out the relatively high energy particles but only until the box reaches 0 kelvin?

[@christophmahler]

In my understanding, *Ernst Mach* proceeds Albert Einstein when it comes to questioning _assumptions and concepts_ of modern physics and either coining or proliferating the German 'Gedankenexperiment' (e.g. in 'Erkenntnis und Irrtum' from 1905). According to Mach there would be no point to mistake e.g. the 'quantum' or any other 'particle' or concepts like 'gravity' as _real_ as the apple that falls on Newton's head - as the only function of physics would be the unbiased and precise _decription of their _*_relation_* within the human _experience_ - which requires experimentation (that is the control of circumstances of observation and their incremental variation) - on one side - and reflecting _'introspectively'_ on 'premises' that guide the design of such experiments on the other side, ensuring whether one asks 'proper' - that is _well defined_ - questions.

[@alaricgoldkuhl155]

Hi Sabine. Not a physicist, but love your videos. I have a question about spatial expansion. We know that it happens/has happened, but is there an understanding about the mechanics of it? I can conceptualize how time is also created as light will take longer to travel through expanding space, but if space is in fact digital and quatized, must it then expand in discrete planck-length geometries?

[@MrRyanroberson1]

Did you read about a recent proposal to solve the paradox? In principle, if you capture all emitted radiation up to 50% of the original mass (from when you start), you should be able to reconstruct where and what the other 50% is (this requires exponentially less computing power as you collect even more)