Physicist Despairs over Vacuum Energy

At 2 mins 26 seconds when I say "Peter" I meant "Paul". Sorry!

Dark energy has got something to do with quantum vacuum fluctuation, whoa, physics. You have probably heard something like that. Alas, that isn't quite right. In this video I clear up the confusion. Vacuum energy is much easier to understand than you might have been told. And it doesn't fluctuate.

0:00 Intro
0:27 Vacuum Energy according to Scientific American
2:07 Vacuum Energy according to Sabine
7:11 The Gas Analogy for Dark Energy
10:04 Sponsor Message

#physics #science

[SabineHossenfelder]

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

[slgnssp]

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

[duprie]

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.

[kumagoro]

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

[chousuke]

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

[ths]

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."

[ooffoo]

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.

[stephenpuryear]

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!

[unamericano]

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.

[joz]

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

[fredg.sanford]

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

[robotaholic]

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!

[improv]

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!

[nikkorocksalot]

This helped clear up some misconceptions I didn't even know I had

Thank you so much Sabine, your clarity is so helpful

[pamwalker]

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.

[thargy]

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.

[Alekosssvr]

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

[russellcollins]

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.

[sbwhddv]

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!

[avermaak]

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