Physicist Despairs over Vacuum Energy 

At 2:36, Peter should have been Paul. Sorry!

I feel like a lot of these books about "the physics of everything" make a tacit deal with the reader: the book will pretend to explain things, and the reader will pretend to understand

"I didn't understand this answer" Good to know that I'm not alone.

I am always totally happy when Sabine points to Einstein's picture, saying: "Yes, that guy again." What a magnificent running gag!

Honestly, I really struggled with early school because so much stuff was simplified and analogised to the point it just didn’t make sense to my tragically over logic little brain. As I got deeper into subjects like physics I felt really betrayed. Now when I teach compsci, I am overly sensitive about being blindingly clear when I am simplifying; and I always try to do a “deeper dive for the interested”. We should never teach analogies as facts just as poor illustrations that allow us to access a deeper concept. Thanks so much for your approach.

Thank you for starting where we must always start in order to sort ourselves out: "terminology", it is tempting to skip, but it is crucial!

The last point about oversimplified analogies is, I think, also particularly relevant in school. Chemistry in particular springs to mind in that they never tell us how it IS, they tell us how it is LIKE. And then, in areas where this model diverges from reality, they give another example of how it is LIKE something else, further perpetuating the problem and making it frustratingly opaque to dissect. Analogies are a double edged sword because they allow someone to gain a foothold in a new area, or to understand the bigger overarching patterns, but when it is used as a substitute for the actual description it becomes more hindrance than help.

Dr. Hossenfelder you have made me love science and physics more than ever so Thankyou for your concise and humorous studies. I’ve learnt more from you than anyone in the past and you answer most of the things I’ve wondered which makes the future more interesting and enjoyable. Education is key to freeing the mind to its full potential and I feel you are easy to understand on these complex topics. Great channel 👏 (Edit) probably best to comment after watching your video. You answered all my questions 🙏🏻 heading toward a star that is coming our way seems to be the quickest way to arrive when it catches us up.

I love how Sabine is transparent about the science; often science reporters push one theory or paradigm without addressing it's flaws, but she seems to truly be impartial.

Another video, I have 3 to watch, a great way to spend a Saturday afternoon, thanks for all the hard work.

Dr. Hossenfelder, I love your channel and your sense of humor. Thank you for making the hard stuff comprehensible.

Sabin's photo of herself "not understanding" is hilarious. I love this channel.

You have become the most interesting physicist around! I love your channel and jokes and learn so much. Thank you for all that work. I couldn't even learn a second language let alone master it and teach physics using it! You are so intelligent and talented. Thank you sincerely!

This helped clear up some misconceptions I didn't even know I had Thank you so much Sabine, your clarity is so helpful

"That guy" also taught us to make things as simple as possible but no simpler. Thnx Sabine.

This was an excellent explanation, It clarified some things for me and showed the dangers of arguing through analogies. Thank you.

I feel like the explanation the editor gave goes something like this: "If we view a ball rolling because of the wind as a ball rolling off a slope, we would conclude that such a wind speed corresponds to such an inclination of the slope. And that's why balls move in the wind."

Dr. Hossenfelder, thank you for taking the time to help break down these complex concepts. While I still don't completely understand it all, you do help me to get rid of misconceptions that I've had about some of these more difficult theories in astronomy and particle physics. Thank you for taking your expertise to the masses and making these very dense topics more approachable. Excellent work!

1) I love the Sabine 'listening/confused/puzzled' expressions, I was pulling the same at the reply. 2) I'm now off grid with a ZPM I found in the back of a dumped puddle jumper :)

You Sabine, are truly awesome. Thanks for making the difficult easier to understand.

Wow. For years I've heard about "the worst prediction in theoretical physics" and wondered how there could be such a ridiculous discrepancy (10¹²⁰) between theory and observation. And not once in all those years has anyone ever explicitly mentioned, "Oh by the way, in QFT we're disregarding gravity, so actually we can add any constant to our definition of energy density, so in fact, the vacuum energy density isn't really determined." I'm a "layperson", so I mostly have to TRUST in what scientists tell me. More & more I feel like I've been had! I mean, I've thought to myself before, "But hang on a sec, there's no gravity in QFT so how...?", but then stopped myself thinking "No, it's too bloody obvious, surely they've factored that in somewhere!" Unbelievable.

Queen Sabine debunking trash science by smart people because we cant tell the difference as layman, lol. Kudos.

thank you for this brilliant mind-bending short video, which helps you fall back in love with Physics if you need to

Dr. Hossenfelder, your explanations are direct and amazing. I’m hooked!

I really, really look forward to Sabines new videos every Saturday. Love this channel and Sabines sense of humour

THANK YOU! Thanks for including the equations and explaining them as you go. Thank you for using more accurate / less confusing terms. And Thank you for your humor! That makes otherwise science more fun!

I'm new to this channel. But both the reply in Scientific American and (especially) your facial expression in response to it was hilarious! As the Brits would say "Jolly good show!" Your response to inappropriate analogies reminds me of Mr. Feynman's critique of 'invisible rubber bands' as an analogy for gravity.

One of my favorite things about your presentation of these fairly high level physics subjects is that you make it extremely clear where the gaps in our knowledge is and the clear delineation between what we know via observation and the theories we attempt to explain through inference. One of my favorite examples is dark matter. It's name is a misnomer. It's just a description of an aspect of astronomy we don't have a good explanation for when comparing our understanding of physics with our observations of galactic rotation. A lot of physicists thing it COULD be some type of particle because it's convenient and covers a lot of the observations they are making, but it's not even able to do that completely. Plenty of other science educators will tout it as THE answer but fail to break apart the complexities of what is wrong with the model or even mention alternative theories because the admission that our understanding of the subject is actually really limited doesn't SOUND like education, but I think for people seriously wanting to understand the sciences the admission of blank spots in our knowledge and limitations of observation are one of the most important things we can keep ourselves reminded of.

Such a better explanation than when PBS space time did an episode on it. I love the clarity of the way you explain things.

The editor's reply is exactly the sort of text my prototype AI response generator regurgitates when trained on previous Q&A datasets. So I'm not entirely sure it was a human that replied.

I didn’t know what to think of this channel at first. Now I’m addicted. Good work!

good morning to my favorite teacher, today's first is queued up, and tonight i'll see where that leads; i've never had so many questions i want to ask, yet i would never ever wish to introduce a frown to a great teacher's day, 2:49 , sometimes it is the things that dont as much as the things that do and the whys that are the utmost illuminating, and i am at the point i realize something.......7.01....... and no idea what i am realizing, vacuum physics indeed,

Thanks Sabine! I have been trying to understand Vacuum Energy for a long time. I STILL don't understand it, but now I am more confident in my ignorance!

This is just a beautiful mind and an incredible teacher. Dr. H, thank you for your work.

I am glad that there is somebody out there that explains this so clear. I always though that "vacuum energy" as result of "quantum fluctuations" was gobbledygook. On the other hand, if vacuum energy increases, because expansion of space, does that means that the mass of the Universe increases?

Vielen Dank, Frau Hossenfelder für die klaren Erklärungen! Das ist der beste Kanal, der sich mit aktuellen Fragen der Astrophysik in wirklich für den Nicht-Fachmann verständlicher Sprache nachvollziehbar auseinandersetzt und vor allem die Widersprüche nicht ausklammert, der also nicht nur ex-kathedra doziert, sondern den Zuhörer in die Gedankengänge mitnimmt. Nochmals: Vielen Dank!

I really enjoy your channel Sabine. I finally can understand some aspects of physics that perplexed me thanks to your presentations. Yours is a most excellent resource, and was most definitely worth my subscribing to!

This deeper dive past what seems more intuitive on surface is especially appreciated, since otherwise I likely would have thought otherwise ^^

MMM... another great presentation Sabine..... Much of the math is beyond my level, but the way you explain things means that I can get a handle on the ideas in an "analogue" kind of way. My knowledge of physics is pretty basic, but I find I can grasp your points quite well even on something as esoteric as this.... Thank you, you keep my 80 year old brain busy, and at my time of life that is a good thing... 🙂

Great videos, thank you so much Sabine!

I just started watching for less than half a minute and I am already having the best fun! This is physics explained in most entertaining way imaginable!

Thanks so much for this short clarification Sabine. Great! That was really necessary.

PLEASE!! :'D Sabine gib uns mehr Reviews mit face-reaction xD deine Mimik ist so expressiv, sein ein Laie der im ersten Moment gar keine Ahnung hat worum es geht _fühlt_ sofort mit und ist "auf der selben Wellenlänge" -- und die die inhaltlich auch noch mitkommen, leiden synchron mit dir -- es ist einfach herrlich ^_^

Thanks for helping to clear this up. A few top physicists (Barrow & Tipler; Weinberg, Carroll, Kaku) in their books failed to explain this clearly - to me!

Omg the look on your face when the editors reply is up. 😂

*Sabine reads editors response Sabine: I'm about to end this man's whole career.

Great video! I agree that it would be really important to clearly set out the limits of our current understanding. I loved the prediction test: "What theories did this measurement invalidate? None?".

You're reactions starting @1:22 are everything!!!

Thank you for your fascinating observations on mainstream science! It is very pleasant to hear real scientists make sense of what we don’t know. I would love to meet you and have coffee and talk about physics… I am a particle physicist too

Thanks Sabine for your great insights. They are Invaluable and useful. You seem to be in a trajectory lately, to erradicate all the nonsense in this field and you are certainly not afraid to break some eggs. You have my support! There is no need to be kind to people in positions that they shouldn't be in, like that awful editor. Keep on doing the great work!

your content is so amazing I'm hooked!

Thanks for explaining this better than some books I've read and tried to understand this (vacuum energy/dark energy/cosmological constant). This includes books by Weinberg (First 3 Minutes, 1993); Barrow &Tipler (Anthropic Cosmological Principle, 1988, equations over my head!); Ross (Why the Universe is the Way it is? 2008, fine tuning argument); and Krauss (Universe from Nothing, 2012). Each seems to summarise the vacuum energy of the universe in different ways, that is confusing for a lay reader like myself. Some clearer explanations I've read were by Sean Carroll, the 10^120 difference between quantum field theory calculation (10^116 eV/cm3) and observed reality (10^-4 eV/cm3), The Particle At the End of the Universe (2013), pages 254-56. Others by Hawking & Mlodinow (Grand Design, 2010); Barrow (Book of Universes, 2012); and Kaku (God Equation, 2021, mentions assumptions of general relativity & quantum mechanics). They all explain it from different angles. I would still like a physicist to show me the maths step by step for how they get the huge 10^120 difference between the quantum field theory calculation and the observed reality? I hope Dr Hossenfelder could do a video, showing the maths step by step how physicists arrive at this huge 10^120 disparity? Even if I don't understand all the maths, I still like to know what each symbol represents and what assumptions are behind it? Anyway, big thanks Dr Hossenfelder for seeking to explain physics to the general audience and for pulling up physicists when they "leave scientific disciplines" and head off into hypothesis, aesthetics, philosophy, and belief statements. Nuff respect to Dr Hossenfelder, I appreciate your explanations greatly.

I would like to see Sabine debate Sean Carroll on this point. I watched a lecture from the Great Courses on candidates for dark energy and Carroll explains the vacuum energy in terms of QFT, which is where you get the outrageous prediction of 10^112 as opposed to 10^-8 for the vacuum energy. He explains these concepts very thoroughly so I’m surprised to see them dismissed here.

Sabine is just brilliant! Love the snarky explanations!

Amazing video. Your scientific approch is quite necessary in the media.

oh why haven’t you turned up in my view list before? a pleasure to watch - thanks

Lol I’ve fallen in love with your channel. Your sense of humor is fantastic. Thanks for doing what you do.

The thumbnail is hilarious 😂😂😂😂

This explanation raised a new question for me: If we agree that vacuum energy is a constant, non-fluctuating enery level from absolute zero, which is everywhere in space, and does not dilute as space-time expands or contracts. Then doesn't it mean that on its own, vaccum energy does not have any "preference" to either expand or contract the universe? All it does is just accelerate whichever state we are currently at. If spacetime is contracting in an area, it will assist in this contraction, and if its expanding in an area, it will assist in accelerating it. So, it does explain why space explansion accelerates, but it does not explain what is the initial thing that drove acceleration above the threshold where vaccum energy alone could keep up the acceleration going (and im not informed enough to confidently say it's the big bang, and that this event alone was enough to get us here), and also doesn't tell me what's stopping space time from locally contract and be accelerated in the other direction by the same vaccum energy principle, or why can't that spread/overtake the current acceleration outwards.

6:58 why add here that it doesn't fluctuate? arent virtual particles bubbling off vacuum as dEdt < k ?

I always thought it is weird that it is just generally _assumed_ that vacuum energy equals dark energy but no one has come up with feasible mechanism explaining _how_ the quantum boiling of vacuum would make spacetime expand on the largest scale. Thanks for clearing this up!

Thank you Sabine for another great video! I appreciate your critical thinking skills that seem to be lacking by those who profess to be experts.

Thanks again, Dr. Hossenfelder! Great video, just what the doctor ordered to clear my mind after reading that article. :-)

4:32 lambda is the energy density of the vacuum, which is energy per volume of empty space 4:41 vacuum energy doesn't dilute if the universe expands because it's a property of space-time 6:45 vacuum energy summary

The editor is now working for the NYT.

Would you mind talking about the Cauchy horizon and that result that says the GR equations don't work after a certain point? I remember reading about it in Quanta Magazine, and when I went to check in the paper it was based on I only got more confused.

I have learned a lot about physics on this and other sites, but all of this incomprehensible to me. Sabine, you are the best. I like watching you for the humor.

Absolutely fascinating. Thank you for my morning brain tickle. Blessings!

Before I saw this video, that math equation looked like a bunch of letters and numbers thrown together by my 18 month old granddaughter. Now it actually makes sense! Thank you Sabine! :)

You rock. Love the way that you break this down. Thank you. I’m still astounded at the constancy of the vacuum energy for a given volume despite the accelerating expansion of the universe. I imagine that this is a big question that once solved will lead to deeper understanding. Is there any relation between the expansion of the universe and any variable at all? Do you think the answer lies tied up in higher dimensional non-de sitter space?

You really are a star Sabine. Thank you for these videos.

Awesome! The picture, the content and the humor :)

I don't know if Sabine ever considered merchandising, but if she does, she needs to make a shirt with a tasteful drawing of Einstein and the caption, "THAT GUY AGAIN".

Thank you, Professor. Years ago, I read literature and the physics text by Professor Richard Fynemann. Human understanding is very limited in our infinite universe.

This is comforting . So often Sabeens explanations seem closer to natural intuition than the ones you hear from other commentators as if many are trying to over sensationalise by making it more counter intuitive for which there really is no need

Congratulations from Brazil. Thanks for the channel. 🇧🇷

Would love for you to chat with Sean Carroll on his Mindscape podcast

The editor's comments sounded rather like the justification of astrology.

Great Sabine, Thank you!

I have heard this general, paraphrased, 'quick characterization' quite a few times, by a number of physicists who's names we'd all recognize. Weinberg, Carrol, Arkadi-Hamad(sp?)... "Virtual particle pairs pop into and out of existence constantly. You are allowed to borrow the energy for this from the vacuum as long as you pay it back [essentially] instantly." I thought, based on the sacrosanct 'conservation of energy' laws, that therefore, the net energy from the vacuum is zero. I've heard that the calculated energy density, necessary to account for the expansion of the universe, (the 'cosmological constant), was 10 to the negative 8th ergs per cubic centimeter. This is often referred to as "dark energy". I've also heard that vacuum energy and the cosmological constant were NOT the same thing, since one equates to zero net energy and one is a calculated value based on data. So, why are we saying here that vacuum energy has ANYTHING to do with the expansion of the universe?

You're so right about inappropriately oversimplified analogies, Sabine. I've spent my whole life trying to drag sense out of stupid pop-sci analogies. It's far harder work than it should be.

I only just discovered you also made music videos. Beautiful, Intelligent and talented 😍

Thank you for that explanation, which basically says vacuum energy is defined as zero, and must be zero, or else it would exert a gravitational field. I did a lot of research, in my early years, chasing down this elusive vacuum energy. Also people constantly interchange the terms energy, power or work, which they are not. We are really after power, or work provided by utilizing differences in energy states. I remember attending a lecture by Prof. Harold Puthoff in 1994. I spoke with him afterwards. He talked about these experiments which he carried out at UCSD, related to attempts to extract Vacuum Energy. He was able to create helical electron streams to extract work, from a force which must of had only the explanation of being created by the vacuum zero-point energy. Of course, this is one way to understand this acceleration. He used a calorimeter, in a closed system, to measure net energy gained and displayed microscopic images of the electrons' path to prove the existence of the force. He approached every sector of the energy industry, with the results. The nuclear industry leaders wanted to replace their expensive enriched uranium rods with these devices and said they would use these, as it would solve the problem of nuclear waste. The oil companies said they wanted to use this as well, since fossil fuels were becoming more expensive to extract and they were looking to diversify their investments to stabilize their profits. This shot down the idea than an evil conspiracy exists which colludes to stop the use of alternative power sources. (I won't say that there aren't some people who might not want more alternate power sources, but this list is far fewer and less powerful than those who do want it). ANYWAY, Puthoff realized, however that although he tried this experiment in many different configurations, it really never proved that net energy could be extracted from the vacuum in any usable form or at all. The energy extracted was very small, in the microwatts and of course, the energy required to put the electrons into a situation where they could spiral down, was orders of magnitudes higher than that. So, he devised the "One Watt Challenge," which meant a closed system must be able to demonstrate a net extraction of one watt of vacuum power for an indefinite period of time. No one has ever demonstrated this, because the laws of thermodynamics are fundamental to the stability of the universe. Its barking up the wrong tree to attempt to extract vacuum energy. Its better to chase elusive energy sources, like fusion, remote energy extraction or solar, wind, etc, than to attempt to extract energy from the vacuum. Because of what you said, we are not after Free Energy, but rather "Low Cost Power". Its power and not energy which does work. Its the "power company", not the "energy company." Even electrons display energy in their ground state. Brownian motion is a form of energy, but not power. Nothing is free; what we need are power sources which are worth the cost of creating the device used to extract it. At this point, we seem to be doing the best we can, which is sad in itself. Because then you realize what a great source of power fossil fuels really are, and they are becoming more difficult to extract, as time goes on. I am optimistic we will overcome all this and someday figure out how to transfer geothermal energy more efficiently, over a broader area of the Earth's surface, due to efficient graphene production methods. I also believe solar prices will continue to decline, due to cheaper electronics manufacturing methods. And ultimately, we will discover some method of focused fusion/fission which will prove useful in more compact systems. I don't put much stock in Tokamaks, because we've spent hundreds of billions on trying to create the conditions of the surface of the sun and are still 50 years from creating something usable. We've spent only millions on focused fusion/fission research. We've barely begun to try out the endless possibilities in that area, whereas the Tokamak route is only a question of optimizing its efficiency. A tokamak is only capable of extracting heat, which is inefficient. Focused fission/fusion has many possible routes, where electrical energy can be directly extracted without first being converted to heat.

... as usual, another satisfying visit to this site ... one my favorites.

Consider for a moment that the Higgs field doesn’t have a constant energy. Gravity in this notion is proportional to the energy that matter imparts to the Higgs field around it. The more and denser matter the higher the energy level of the Higgs field, right up to the point where the Higgs Field energy equals that of the particles and the field merges with the matter and the matter collapses to become a black hole. For this to be true matter must have a portion of its energy dispersed into the field. So where gravity is effectively the energy of the Higgs field, considers the moment of the creation of a Black Hole where in an instant the energy of the field is separated from the matter that gave the field that energy. That body of energized Higgs Field would remain in space giving that area of space the effect of there being matter present, when in fact it is not. Anything passing through that energized field would behave as if there was matter present ie the matter would appear Dark. We know that you can apply energy to the Higgs Field and it will transition to matter. The question is, is this a progressively gradiënted transition?

I mean...the best analogy for this is the beating heart, blood pressure and the function of valves...and analogies are key to understanding physics.

Two minutes in and I was already in stiches! Sabine should do this more often pre-recording her voice so she can do such an elegant display of facial expressions! That said, major cloud bank of fog started to lift when I read a Beretsevsky paper that explained: in QED, QFT etc., 'vacuum' has taken on a new meaning: it does not mean absolutely nothing, it instead means "the ground state of the field".

Never got closer to clear understanding than with your videos and your book

After reading the daily news, I need a dose of Sabine to retain my sanity. Thanks!

Wait, isn't gas pressure caused by particles hitting the walls of the CONTAINER? How do you define gas pressure, where there is only the gas and no solid bodies? Also if the vacuum/gas energy (how indeed does the vacuum work as a gas) exerts energy on the galaxies, wouldn't this just move the galaxies IN space, and not just create more space?

Love this video it's the fist time I see one explaining the maths of equations. And there's not much of that around RU-vid. Well there's much about it like the man who say you're going to understand lagrangian after his videos and are 45 video of half hour each and you don't understand a word since the part 1 of 45. And always says well you don't need to understand this. Only the effect

Thank you for your helpful explanation of what science believes is occurring in space. Have these mathematical equations for vacuum power been tested in the real world or are they just mathematical concepts used to explain what we think we observe

Great job as usual. Enlightening. Services like NordVPN require the same hard look at what they say and what their reality actually means.

That face reading the editor's replay. I almost fell out of my chair.

As always common sense analysis Is your winning hand,why do some specialists seem so lost in the details,the forest is the trees and show this clearly.Thanks for that.

This is a superbly-explained video. Thanks.

My wife has about ten vacuums and spends a lot of energy on them.

Last time I was this early my vacuum had energy. I followed everything except the definition of the scale factor. Anyone care to explain the scale factor more thoroughly?

Great explanation, and not just because it totally agrees with my understanding of the subject lol. I’m so glad to have found the ‘Sabine’ of physics, (I'm referencing the racing driver and Top Gear Sabine Schmitz).

Thanks very much, I found this analogy between the pressure of gas and the pressure of false vacuum in the Guth's book with aims to explain inflation and I couldn't understand it. He say that the negative pressure of a false vacuum does think arise suction effect, although the opposite effect takes place. Now I think that this analogy create confusions.