If every human on Earth today had to be placed 6 light years apart from another person, how large would the diameter of this bubble of humans be? And yes, a bubble rather than a line, because a line would be much longer and it would be easier to calculate. Go!
One of my biggest joys while being quarantined here in a hot zone part of California is watching Professor Caroll's "The Biggest Ideas in the Universe". Thank you for sharing your knowledge with the rest of us.
im in Chula Vista, 74 and breezy, I cannot complain one bit, plus, COVID would kill my immune suppressed daughter, so watching these at home with her is fun
Oh my god that expression at 26:20 when Sean calls Emmy Noether “Emily” is just priceless :’) Thanks for not cutting (or more likely failing to cut) that out.
A positive effect of quarantine is that we now have a greater number of scientists doing their own podcasts and getting knowledge of complex topics into the general public.
OH MY GOD. I failed out of calculus three times in college. I only stopped because it was ruining my GPA. I wanted to be a physisist since I was 9 years old and tried and tried, but couldn't grok the maths! (I became a computer scientist instead LOL} The theory absorbs like a sponge but the nuts and bolts, I eventually accepted, were simply beyond me. Apparently my professors just were terrible! This video, and the barebones mathmatical theory involved, was an Eureka! moment for me, and youir explaination was just a tangent! Thank you, Sean Carroll! I feel foolish for not seeing the relationships I had at hand, and also a burning rsentment of what counts as an educational system in the United States for failing to actually educate me as me as a young, enthusiastic, student.
You are such a great Teacher! I wish you could also do more advanced, full-fledged physics courses in this exact format, with mathematics and all that🙄
Hi Paps. He does have many classes on The Great Courses. I took Dark Matter, Dark Energy. Here's the link: www.thegreatcourses.com/search/?q=Sean+Carroll Enjoy. I did. It's worth it just to see his tie collection :-)
carroll is arguably the best guide and explainer, when it comes to the mind-boggling , mind-stretching, contents of today's physics. He explains and even entertains, without oversimplifying and dumbing down the subject.
I don't believe I am watching this. Finishing my second glass of wine and laughing hysterically. Fifty years since I graduated from college. The best I got in calculus was Cs and I pretty much forgot everything. Pretty uninspirational teacher. Took Khan Academy High School Calculus BC last year for awhile, so the waters are not so muddy. All that said, I am sort of following and sort of comprehending. Thank you. I bought your book, Something Deeply Hidden, and read the first few pages and I pulled out Laurence Krauss"s book, Fear of Physics and reread a bit today. He also mentions the cow/sphere analogy. Thanks for this.
Wow what a series this is turning out to be! Its good to see you've already become very accustomed to presenting your doodles on the ipad, you seemed to be having a lot of fun with it. The whole presentation flowed super smoothly, well done and thank you so much!! I didn't know you were doing Q&A, hopefully I can offer you a few questions relevant to your upcoming topics. Thanks once again for such an amazing presentation, we're all truly humbled by your efforts as one of the worlds leading communicators of science.
Your sighing at the wave function really shows how much you are willing to respect your other colleagues in the field. Its almost like you are doing your best to acknowledge their POV although you've done so much to educate so many about a much more expansive POV that identifies the wave function as the fundamental underlying reality. Its kind of nice, it demonstrates the type of humanity you have.
First, I was being lazy to tap in the video after watching this time line, but after tapping on it, It was like.... Why this video ended! Sir! I learnt a lot today and I am Very Very much Happy that I watched the video which clears all the basic doubts! Thanks! ♥️🙏Love from India!
First question almost made me pass out I was laughing so hard. I would watch and hour of Sean reading usernames with a straight face. PRICELESSLY FUNNY!!
I've followed the podcast since the beginning. I'm not smart enough to understand 100% of the stuff that comes out of your mouth but I'm still enamoured by the physics. You make me second guess the thoughts in my head that tell me my lack of math and science means I shouldn't or can't learn more. You broaden my understanding, thank you.
Excellent as usual. As much as I enjoyed the initial talk on conservation of P. This Q&A video was even MORE enjoyable. You do have a great gift for teaching. Every time you digress or expand on an explanation of some kind, its like you read my mind and answered the questions I was thinking about!!!!! I have read Feynmans Six easy and not so easy pieces (also read his biographies, etc). You absolutely deserve to be sitting at the great mans desk. Thank you for this video diversion in these crazy times.
I just watched your first video, and loved listening to your understanding and explanations. you did make one comment in the q&a where you said that the photons energy will not be conserved as it is stretched through the expansion of the universe. You said that the energy goes down as the wavelength stretches, which is true, except that the actual energy in the photon does not change. if the energy in the photon changed the photon could not be moving at the speed of light. As it is moving at the speed of light the photon experiences no time. From the point that it left Galaxy X 13 billion years ago the photon has experienced no time, and no change, until it reaches our detectors here on Earth. But as we are moving away from it now at near the speed of light, because of the expansion of space, the energy seems to be lower as it is red shifted, but it is only our relative movement that makes that light seemed lower energy. If we were moving towards that same light source, it would seem much higher energy to our precepton. I don't know enough about this to know that I'm right, I am assuming that I have to be wrong at how I perceive this, otherwise everyone else is looking at this the wrong way. Thank you thank you thank you again for putting the time in to these lectures. I have watched many of them and decided I needed to start at the beginning if I really want to understand these big ideas.
10:00 the statement at bottom is correct , but above he says the momentum is accumulated as it travels at constant speed ie the longer it travels for the more kinetic energy. I’m pretty sure this is wrong. Or am I wrong ?
35:11 This is such a good explanation. Thanks for this. So this is also an explanation of not only e=mc2 but E = h · c / λ the difference always made me scratch my head because photons don't have mass from what little I understand and therefore could never really grasp how e=mc2 could be applied to them. So this energy then is turned into in some subtle way "vacuum energy" as you say - how is this explained in quantum field theory? Vacuum energy is just the neutral state of some discrete space/time field and somehow photons by losing all their energy or more accurately -> frequency & they become "flat" and disperse throughout the entire known universe all at once contributing to a greater sum of vacuum energy? lol. I think I'm stretching my brain too far but I greatly appreciate the videos, I'm really trying to educate myself recently - I have a long way to go!! (at least 23 episode :P )
Good morning Professor Carroll, Thank you so much for publishing such amazing content, in time like these it's great to see physics being divulged in such a simple cohesive and yet exciting way! Let me just begin by saying that I am a huge fan of yours. From your books to your podcasts and talks I have been following your work for quite some time now. I am currently trying to contact you because I just ended my BS Eng from case western reserve university in Engineering Physics and I have to say I am a bit lost on what path I should take next. I have a deep passion for physics, more in particular I like to question reality. A question I would like to answer is whether or not there is a unit of space time and if the Planck length truly is the ultimate unit of space time. Do you think that philosophy of physics might be a good path to answer such questions? Or do you think theoretical physics would be more appropriate? I know experimentally we don’t have a way to currently prove this, as we would need a particle accelerator immensely large to try and study the physics at such scales. I hope to hear from you soon Professor, Best wishes, and I look forward to more of your content in the Biggest Ideas in the Universe!
I have a few simple questions about different kinds of momentum. One, are planets in orbit around a star 'conserving momentum' by following the 'curvature of space' around the star, or is this is actually accelerated motion involving some expenditure of energy? I've heard references to orbits decaying but I don't know if this is due to some kind of friction (maybe deformations of the orbiting body) or just inherent in the nature of orbital motion. Two, is angular momentum, say a planet spinning on its axis, conserved, or is there also some inherent decay? Is there a clean relationship between angular momentum and linear momentum such that we don't need to distinguish them when talking about conservation of momentum?
Planetary orbits can decay via photons from the sun hitting the planet and transferring its momentum, slowing it down. Angular momentum is also conserved in a system if the net torque is zero. While there is a relationship between the two, it is often more useful to practice both conservation of linear and angular momentum
31:30 Sean mentions how the expansion of space means the frequency/wavelengths of photons changes because of Doppler shift, and so the energy of the photon changes (E = hf and all that). That led me to think about relative motion THROUGH space, and how Doppler shift still ovvurs. Doesn't THAT mean that the energy of a photon is not only a property of that photon, but also of the relative motion betwen photon and observer? I know this is something of a digression but if anyone has the answer it may help many on this journey with Sean.
You have to remember that the speed of light is the same to all observers (one of the fundamental assumptions in Einstein's formulation of special relativity). So the relative motion between photon and observer is always the same - the speed of light. But, just because different observers perceive the speed of photons to be the same doesn't mean that they perceive the frequency (and hence the wavelength) to be the same.
31:30 RE: the discussion of photons losing energy as space expands... Is it possible that the energy lost by the photon is somehow transferred to space itself (and this conserved)? If so, could this process be at least a contributor to the non-zero vacuum energy? Edit: “thus conserved” not “this conserved”
I hope you do an episode on mass, in particular the origin of mass as arising from the containment of massless particles (see PBS Spacetime “The True Nature of Matter and Mass”). I’d like to see this analogy extended into curved spacetimes so we can see how such a construction of massless particles experiences gravity and “feels heavy,” and if possible, how it could create curved spacetime/gravity.
Rest energy (mc2) does not seem to depend on material.... How do get all the rest energy out of a 1kg block of iron? Large molecules like uranium and small ones like hydrogen, sure but splitting or fusing iron doesn't give out energy.
I'm glad you talked about Baryogenesis and some less common conservation concepts, I honestly thought that you would skip it (like most physics explanation videos do). I'd rather you risk losing some of the more new people than just assuming that your whole audience can't understand. I like the concept of hanging some slightly difficult concepts out there in the hopes that it will inspire people to look deeper and understand those concept.
I've always struggled wiht the concept of expanding space. I know how to say the words but I don't understand the concept at all. How would we know space is expanding? Any physical ruler would exist within space and would expand along with the space. Does "speed" have meaning in expanding space? What about "distance"? It's so easy to say "expanding space" but I find it almost entirely unimaginable. Can anyone point me to somehwere helpful?
Around the 20 minute mark, he discusses whether or not Galileo might have known about Ibn Sina or at least that Ibn Sina said that without effects like those from air resistance, an object would continue moving. I learned that Galileo used ramps so that he could more accurately time rolling balls by slowing them down. I now wonder if he also knew that he was minimizing the effect of air resistance. If he did, that might indicate at least knowing what Ibn Sina thought. I also wonder if Galileo had any guesses about if and how air resistance varies with speed.
I think a lot of the misconceptions in theoretical physics and cosmic philosophy are a result of us trying to use digital math to quantify an analog cosmos. Every quantum interaction is just fields interacting, and they don't have numbers associated with them. What is required is a fundamental change in how we view math. Numbers and equations are not the path to precision. We need interferometric waveform math, and I think the path to that is quantum computing. We have to design a system we can't possibly understand (even the engineers and physicists) It's like trying to conceptualize a fourth special dimension. We can't possibly fathom a fourth axis at 90° simultaneously to all of the 3 dimensions we experience.
Hi Sir, I have a simple question. Inside a factory at the end of the shift a supervisor and his co-worker are counting the produced objects, the objects are approximately the size of a tennis ball. It is their daily routine,the worker counts the objects as he takes it from the production lot and puts it inside a bag. The role of the supervisor is to keep watch so that there is no mistake while counting. One fine day, before starting the counting process, the supervisor looks at the lot and writes done some random three digit number as quantity of the produced items, in short he assumes that the actual quality would probably match with that number. Now the question is what are the chances of that actual quantity matching exactly with that random number?
Hi Prof Carroll, I just wondered if you have also been watching Brian Greene's "Your Daily Equation" ? I merely ask as a fan of both you and Prof. Greene. Thanks for this great new series BTW.
Where could we find an antiparticle for every particle in our universe? Just considering that time were going both directions simultaneously, every neutron in our universe's time direction would be its corresponding antineutron in the reverse time direction. Every proton, its antiproton. And so on. Total baryonic number in both time directions: 0. Total leptonic number in both time directions: 0. A nice symmetry, two universes in one (the antiuniverse would however decrease entropy in its own time direction.... but "past" the big bang instant, and I mean "past in the reverse time direction," it would increase entropy as it goes longer and longer past that instant, whereas it would be our universe's particles that would decrease entropy before the big bang in our time direction. Not sure if this all makes sense. . . . Could time really be both directions at once? Semantics are not really helping in such a situation, "at once" meaning "at every one instant" in this case.
Time slows down the faster you go. Mass increases the faster you go. Time slows down in the vicinity of black holes. Is there a law of conservation of time or is this a reflection of something else to do with the behavior of spacetime?
Take two rocks separated by some distance at time t=0. The universe expands until time t'=1, and now the distance between them is greater. The gravitational potential energy between those rocks should be greater now due to the increased separation. Shouldn't the same apply to galaxies? What am I missing?
Question about black holes If from our perspective anything aproaching the event horizon of a BH slows down in time how can we see a BH grow. And how can we see two BHs merge. The only thing we "should" see is seeing those object freeze in time as they aproach the event horizon.
Thank you Prof. Carroll! This series are much appreciated for people like me that don't have the means to go to a university and learn from the best. I have a question. What about Hawking radiation, wouldn't that violate conservation of energy in some way?
The particle pairs from Hawking radiation borrow some of the energy from the black hope, so energy is still conserved. The black hole loses energy in the process due to the escaping particle
I don't know what it is, but I get way less out of these videos than I do from Sean explaining things, or discussing them, with another person present.
T.O.E thesis: The collapsed wave of probability functioning similarly at unsame scales has a different appearance. Our sensory set reaches limitation of expected capacity at a different perceptual domains. In the same~ way, a planar observer of offset signwaves will see intersection at alternate opposite inflection points; where to a third-dimentional viewer, intersection within the same offset spiral-form waves never appears...
If you spaced heavy objects throughout the known universe would it bend the universe enough to win? I guess I'm asking is the constant dependent on the amount of stuff?
Trying to wrap my head around what happens when multiple worlds branch after an "observation" is made and how energy is conserved: - Energy = x in the pre-observed world in which a particle is actually a wave - An observation is made and the wave collapses into a particle; this now-entangled and branched world has energy = y1 < x - For simplicity, say there are 3 total "entanglements" possible -> are 3 branching worlds thus simultaneously created? If N possibilities -> are there always instantaneously N branched worlds? - For N branched worlds each with energy y (sub z) [where z is integers from 1 to N, and y1 may or may not equal y2 (etc...)], is it true that the summation of y1 + y2 + y3 ... +yN = x ???
Does anybody know if Sean Carroll ever does public speeches with meet and greets? That would be the thrill of a lifetime! I will always refer to the wide eye slight lift of the forehead stripped of facial twitches blank canvas with the glistening twinkle of humor in the eye as the Sean Carol effect, I’ve tried so hard to do it. One day I’ll get it down
We know as a fact that the universe is expanding , which affects the space . And if space time is one thing in itself it should be affecting time too, right ? If that is true how does that happen ? And can we perceive this effect here on Earth ?
always wondered if it wouldn't save a lot of confusion among beginning physics students to write Einstein's infamy as dE/dm = c^2. Makes it rather obvious that the gain in mass in fission equates to excess energy which must manifest elsewhere in the system
A question on the conservation of momentum: Do two particles exist in the same reference frame at the same time - whatever "same time" can mean? ie, does a particle continue at a constant velocity because inertial frames are distinct and an interaction is required to destroy a particle in one frame and create some in other frames?
In the expanding universe do the energies gained by the cosmological constant and lost through redshift cancel each other out? If not is it possible that energy is conserved in the wave function of the universe (Hilbert space)?
thank you for this, einstein was before media, hawking couldnt talk, the world really needs to hear whats going on inside your brain, this mite be the most important thing on the internet
you will be surprised to know Einstein was a bigger media celebrity than all the Kardashians and clooneys and Pitts and jlos put together in his time. it is a tragedy that our celebrities are of such low quality.
Could you talk a bit more about: If energy in an expanding universe is NOT conserved how (does it work) / why is the cosmological constant still fixed per cm of space and remains so, even as the universe expands? - Is the conserved / not conserved energy in the expanding universe related to the many worlds interpretation? Something like: the total amount of energy remains constant just not in our particular universe? Kind Regards and thank you so much for doing this. Henry B. - Stockholm, Sweden.
A conservation of the one (energy) but not the other (mass) would violate the energy-mass equivalence. In fact a hot cup of coffee has more mass than a cold cup of coffee, even though the total mass of any particle is equal in both cases. "Mass" is not bound to the particles alone, but to the closed system "cup of coffee". And for closed systems the conservation of mass is still valid.
It seems like a fudge if you are saying energy is not conserved in an expanding universe? If a photon is being red shifted In such a universe, where is its energy going? Can't this be transferred to the vacuum energy surrounding it and thereby conservation of energy is being maintained? This is besides the energy contributing to the expansion of the universe (undefined dark energy).
Sean, in Hawking radiation, at the event horizon two virtual particles are produced as matter and antimatter. Is it true before they annihilate each other, they get pulled apart and one particle escapes into space and the other into the black hole. For black hole evaporation , does it matter which particle gets absorbed into the black hole ? Matter or antimatter ? Is it true it’s 50/50 which particle escapes ?
Im no Sean Carroll, but I know enough to help with your question.Yes, particle-antiparticle pairs are "ripped" apart at the EH. The outgoing particle always has positive energy since it requires energy to create said particle. This means that the other particle has negative energy - in the sense that it has to balance out the energy given away to the particle that escaped into space. Another way to look at it is that the particle that is created and escapes "steals" some of the gravitational potential energy of the BH to form said particle. And to the crux of your question: if the hawking radiation creates a charged particle, then it would randomly produce either +/- charge equally - Else it would become charged and quickly neutralize itself. Note: this doesn't apply to photons as they are their own anti particle.
I wish I had found this series in time to ask about the relationship of kinetic energy (1/2mv^2) and E=mc^2. Except for the “1/2” term the two fórmulas are identical. Since light is a velocity and since it’s the maximum velocity, is E=mc^2 not related to the kinetic energy of a mass moving at c? Years after my two basic college physics electives, I thought I had some breakthrough understanding the intuitiveness of E=mc^2 when I first realized the similarity of the two formulas. But, I had forgotten the 1/2 term. Sadly, I realized after college so I couldn’t just ask my teachers in class the next day.
![Felix "Unfair" | [Stray Kids : SKZ-PLAYER]](http://i.ytimg.com/vi/Oswujxm2Ag0/mqdefault.jpg)
The background behind you suggests you're taking the social distancing very seriously.
lol - yeah I'll say :-)
I'd say so. Apparently the Voyager space probe is now roughly 13.2 billion miles from Earth. It's about as isolated as you can get!
It's recommended you maintain a distance of at least 6 light years from other life forms
If every human on Earth today had to be placed 6 light years apart from another person, how large would the diameter of this bubble of humans be? And yes, a bubble rather than a line, because a line would be much longer and it would be easier to calculate. Go!
@@rikuzenith Where is Scott Aaronson when you need him?
One of my biggest joys while being quarantined here in a hot zone part of California is watching Professor Caroll's "The Biggest Ideas in the Universe". Thank you for sharing your knowledge with the rest of us.
"Rest energy"...is that like cabin fever?
@@davidschneide5422 what?
im in Chula Vista, 74 and breezy, I cannot complain one bit, plus, COVID would kill my immune suppressed daughter, so watching these at home with her is fun
@@JoeHynes284 wishing you and your daughter a wonderful day, my friend. Stay safe
Oh my god that expression at 26:20 when Sean calls Emmy Noether “Emily” is just priceless :’) Thanks for not cutting (or more likely failing to cut) that out.
He still mispronounces Noether though.
A positive effect of quarantine is that we now have a greater number of scientists doing their own podcasts and getting knowledge of complex topics into the general public.
OH MY GOD. I failed out of calculus three times in college. I only stopped because it was ruining my GPA. I wanted to be a physisist since I was 9 years old and tried and tried, but couldn't grok the maths! (I became a computer scientist instead LOL} The theory absorbs like a sponge but the nuts and bolts, I eventually accepted, were simply beyond me. Apparently my professors just were terrible! This video, and the barebones mathmatical theory involved, was an Eureka! moment for me, and youir explaination was just a tangent! Thank you, Sean Carroll! I feel foolish for not seeing the relationships I had at hand, and also a burning rsentment of what counts as an educational system in the United States for failing to actually educate me as me as a young, enthusiastic, student.
The USA spends ten times more subsidising fossil fuels than on the entire education budget..
You are such a great Teacher! I wish you could also do more advanced, full-fledged physics courses in this exact format, with mathematics and all that🙄
Hi Paps. He does have many classes on The Great Courses. I took Dark Matter, Dark Energy. Here's the link: www.thegreatcourses.com/search/?q=Sean+Carroll Enjoy. I did. It's worth it just to see his tie collection :-)
I’d like to think the Many Worlds theory includes a universe in which I understand all this.
I actually understood parts of this, especially many of the shorter words.
"I will not be naming everyone, just the ones with really funny usernames."
At least one person will now be thinking "I should have changed my username from when I was 11"
I wonder if he would have said my name :)
I’ve been a Patreon supporter of Mindscape since the beginning and a big fan of your work in general. You bet I’m going watch this series!
ENERGY IS REAL. YOU'RE RIGHT,
SEAN. THERE IS NO CALORIC.❤
Suggestion: maybe a quiz at the end to see and apply what we've learned to help store it??? Like a challenge for us just learning. Thanks.
carroll is arguably the best guide and explainer, when it comes to the mind-boggling , mind-stretching, contents of today's physics. He explains and even entertains, without oversimplifying and dumbing down the subject.
I don't believe I am watching this. Finishing my second glass of wine and laughing hysterically. Fifty years since I graduated from college. The best I got in calculus was Cs and I pretty much forgot everything. Pretty uninspirational teacher. Took Khan Academy High School Calculus BC last year for awhile, so the waters are not so muddy. All that said, I am sort of following and sort of comprehending. Thank you. I bought your book, Something Deeply Hidden, and read the first few pages and I pulled out Laurence Krauss"s book, Fear of Physics and reread a bit today. He also mentions the cow/sphere analogy. Thanks for this.
Wow what a series this is turning out to be! Its good to see you've already become very accustomed to presenting your doodles on the ipad, you seemed to be having a lot of fun with it. The whole presentation flowed super smoothly, well done and thank you so much!! I didn't know you were doing Q&A, hopefully I can offer you a few questions relevant to your upcoming topics. Thanks once again for such an amazing presentation, we're all truly humbled by your efforts as one of the worlds leading communicators of science.
I've just finished Feynman's six 1964 Messenger Lectures at Cornell, so this series is a great way to reinforce these ideas.
Nice, I just started it.
Your sighing at the wave function really shows how much you are willing to respect your other colleagues in the field. Its almost like you are doing your best to acknowledge their POV although you've done so much to educate so many about a much more expansive POV that identifies the wave function as the fundamental underlying reality. Its kind of nice, it demonstrates the type of humanity you have.
To a motivated learner , these videoes are of great help 👏
I'm so glad that I've discovered this series, thank you! :)
Me too thanks much appreciated
First, I was being lazy to tap in the video after watching this time line, but after tapping on it, It was like.... Why this video ended!
Sir! I learnt a lot today and I am Very Very much Happy that I watched the video which clears all the basic doubts!
Thanks! ♥️🙏Love from India!
First question almost made me pass out I was laughing so hard. I would watch and hour of Sean reading usernames with a straight face. PRICELESSLY FUNNY!!
You're an awesome company in days like these. Thank you so much for sharing your knowledge to a wider audience! Regards from Louise, Sweden.
I like how you answered the Galileo, Newton, Ibn Sina question. Specifically the history Galileo experienced in Italy 🇮🇹! Great work!
Thank you so much, from Italy on lockdown I appreciate the chance to learn such interesting things. I got to understand and love physics from you.
I've followed the podcast since the beginning. I'm not smart enough to understand 100% of the stuff that comes out of your mouth but I'm still enamoured by the physics. You make me second guess the thoughts in my head that tell me my lack of math and science means I shouldn't or can't learn more. You broaden my understanding, thank you.
Hello from Italy, professor, love what you’re doing with this series of videos!
Excellent as usual. As much as I enjoyed the initial talk on conservation of P. This Q&A video was even MORE enjoyable. You do have a great gift for teaching. Every time you digress or expand on an explanation of some kind, its like you read my mind and answered the questions I was thinking about!!!!! I have read Feynmans Six easy and not so easy pieces (also read his biographies, etc). You absolutely deserve to be sitting at the great mans desk. Thank you for this video diversion in these crazy times.
I’m loving these. Please keep it up. Thank you.
So happy your subscriber base is growing. Not a measure of how brilliant you are!
This is wonderful, I'm watching it again.
I just watched your first video, and loved listening to your understanding and explanations.
you did make one comment in the q&a where you said that the photons energy will not be conserved as it is stretched through the expansion of the universe. You said that the energy goes down as the wavelength stretches, which is true, except that the actual energy in the photon does not change. if the energy in the photon changed the photon could not be moving at the speed of light. As it is moving at the speed of light the photon experiences no time. From the point that it left Galaxy X 13 billion years ago the photon has experienced no time, and no change, until it reaches our detectors here on Earth. But as we are moving away from it now at near the speed of light, because of the expansion of space, the energy seems to be lower as it is red shifted, but it is only our relative movement that makes that light seemed lower energy. If we were moving towards that same light source, it would seem much higher energy to our precepton.
I don't know enough about this to know that I'm right, I am assuming that I have to be wrong at how I perceive this, otherwise everyone else is looking at this the wrong way.
Thank you thank you thank you again for putting the time in to these lectures. I have watched many of them and decided I needed to start at the beginning if I really want to understand these big ideas.
I absolutely love these. Thanks, prof. Keep 'em coming!
🙈🙉 thank you for this free education, The intellects are the true rock stars!
Thanks for this. Videos and Q&A a great combo
Great stuff. just what I need while at home..
Thank you so much Sean for the time you put for explanation these fundamental concepts. Awesome timing as well while we are mostly at home.
LOL at the cat chaos causing timeline jumps. Only Sean's cats could do this :)
Cats always make a mess of our physics laws
Your stuff is amazing dude i love listening and getting my mind melted 😂🙏 keep it up!
10:00 the statement at bottom is correct , but above he says the momentum is accumulated as it travels at constant speed ie the longer it travels for the more kinetic energy. I’m pretty sure this is wrong. Or am I wrong ?
"Is the Universe a closed system? All the evidence we have says yes."
Roger Penrose: "Hold my crumpet."
First? maybe. keep up the good work, i really enjoy this
35:11 This is such a good explanation. Thanks for this. So this is also an explanation of not only e=mc2 but E = h · c / λ the difference always made me scratch my head because photons don't have mass from what little I understand and therefore could never really grasp how e=mc2 could be applied to them.
So this energy then is turned into in some subtle way "vacuum energy" as you say - how is this explained in quantum field theory? Vacuum energy is just the neutral state of some discrete space/time field and somehow photons by losing all their energy or more accurately -> frequency & they become "flat" and disperse throughout the entire known universe all at once contributing to a greater sum of vacuum energy? lol. I think I'm stretching my brain too far but I greatly appreciate the videos, I'm really trying to educate myself recently - I have a long way to go!! (at least 23 episode :P )
Excellent. Thank you.
Good morning Professor Carroll,
Thank you so much for publishing such amazing content, in time like these it's great to see physics being divulged in such a simple cohesive and yet exciting way!
Let me just begin by saying that I am a huge fan of yours. From your books to your podcasts and talks I have been following your work for quite some time now. I am currently trying to contact you because I just ended my BS Eng from case western reserve university in Engineering Physics and I have to say I am a bit lost on what path I should take next. I have a deep passion for physics, more in particular I like to question reality. A question I would like to answer is whether or not there is a unit of space time and if the Planck length truly is the ultimate unit of space time. Do you think that philosophy of physics might be a good path to answer such questions? Or do you think theoretical physics would be more appropriate? I know experimentally we don’t have a way to currently prove this, as we would need a particle accelerator immensely large to try and study the physics at such scales.
I hope to hear from you soon Professor,
Best wishes, and I look forward to more of your content in the Biggest Ideas in the Universe!
35:20 Would it be possible to have the decrease in photon energy and increase in vacuum energy to cancel each other out and keep the energy conserved?
I have a few simple questions about different kinds of momentum. One, are planets in orbit around a star 'conserving momentum' by following the 'curvature of space' around the star, or is this is actually accelerated motion involving some expenditure of energy? I've heard references to orbits decaying but I don't know if this is due to some kind of friction (maybe deformations of the orbiting body) or just inherent in the nature of orbital motion. Two, is angular momentum, say a planet spinning on its axis, conserved, or is there also some inherent decay? Is there a clean relationship between angular momentum and linear momentum such that we don't need to distinguish them when talking about conservation of momentum?
Planetary orbits can decay via photons from the sun hitting the planet and transferring its momentum, slowing it down.
Angular momentum is also conserved in a system if the net torque is zero.
While there is a relationship between the two, it is often more useful to practice both conservation of linear and angular momentum
31:30 Sean mentions how the expansion of space means the frequency/wavelengths of photons changes because of Doppler shift, and so the energy of the photon changes (E = hf and all that).
That led me to think about relative motion THROUGH space, and how Doppler shift still ovvurs. Doesn't THAT mean that the energy of a photon is not only a property of that photon, but also of the relative motion betwen photon and observer? I know this is something of a digression but if anyone has the answer it may help many on this journey with Sean.
You have to remember that the speed of light is the same to all observers (one of the fundamental assumptions in Einstein's formulation of special relativity). So the relative motion between photon and observer is always the same - the speed of light. But, just because different observers perceive the speed of photons to be the same doesn't mean that they perceive the frequency (and hence the wavelength) to be the same.
Great idea ti share with us your knowledge and excelent teaching abilities during this selfquaranteen time. I enjoy it very much
31:30 RE: the discussion of photons losing energy as space expands...
Is it possible that the energy lost by the photon is somehow transferred to space itself (and this conserved)? If so, could this process be at least a contributor to the non-zero vacuum energy?
Edit: “thus conserved” not “this conserved”
I hope you do an episode on mass, in particular the origin of mass as arising from the containment of massless particles (see PBS Spacetime “The True Nature of Matter and Mass”). I’d like to see this analogy extended into curved spacetimes so we can see how such a construction of massless particles experiences gravity and “feels heavy,” and if possible, how it could create curved spacetime/gravity.
please continue this style vid
Math and the formulas, literally speaking to you, telling u deep truths via tricks and shortcuts is amazing
at 8:18 - 8:49 - perfect place to mention that Work = mad = force * distance?
Rest energy (mc2) does not seem to depend on material.... How do get all the rest energy out of a 1kg block of iron? Large molecules like uranium and small ones like hydrogen, sure but splitting or fusing iron doesn't give out energy.
Thanks for this series. I am enjoying it a lot !
I'm glad you talked about Baryogenesis and some less common conservation concepts, I honestly thought that you would skip it (like most physics explanation videos do). I'd rather you risk losing some of the more new people than just assuming that your whole audience can't understand. I like the concept of hanging some slightly difficult concepts out there in the hopes that it will inspire people to look deeper and understand those concept.
I've always struggled wiht the concept of expanding space. I know how to say the words but I don't understand the concept at all. How would we know space is expanding? Any physical ruler would exist within space and would expand along with the space. Does "speed" have meaning in expanding space? What about "distance"? It's so easy to say "expanding space" but I find it almost entirely unimaginable. Can anyone point me to somehwere helpful?
I feel like if aliens were here, this is how they'd try and help us monkeys. Thank you Sean.
Around the 20 minute mark, he discusses whether or not Galileo might have known about Ibn Sina or at least that Ibn Sina said that without effects like those from air resistance, an object would continue moving. I learned that Galileo used ramps so that he could more accurately time rolling balls by slowing them down. I now wonder if he also knew that he was minimizing the effect of air resistance. If he did, that might indicate at least knowing what Ibn Sina thought. I also wonder if Galileo had any guesses about if and how air resistance varies with speed.
Good to see you in a pod cast Sean
I think a lot of the misconceptions in theoretical physics and cosmic philosophy are a result of us trying to use digital math to quantify an analog cosmos. Every quantum interaction is just fields interacting, and they don't have numbers associated with them. What is required is a fundamental change in how we view math. Numbers and equations are not the path to precision. We need interferometric waveform math, and I think the path to that is quantum computing. We have to design a system we can't possibly understand (even the engineers and physicists)
It's like trying to conceptualize a fourth special dimension. We can't possibly fathom a fourth axis at 90° simultaneously to all of the 3 dimensions we experience.
Keep em coming. Love your lectures
At 7:23 , what you meant to say was that it is an isosceles right triangle, as in 45/45/90. It is certainly not equilateral (as Pythagoras showed)!
Oops, you're right!
Hi Sir, I have a simple question. Inside a factory at the end of the shift a supervisor and his co-worker are counting the produced objects, the objects are approximately the size of a tennis ball. It is their daily routine,the worker counts the objects as he takes it from the production lot and puts it inside a bag. The role of the supervisor is to keep watch so that there is no mistake while counting. One fine day, before starting the counting process, the supervisor looks at the lot and writes done some random three digit number as quantity of the produced items, in short he assumes that the actual quality would probably match with that number. Now the question is what are the chances of that actual quantity matching exactly with that random number?
Hi Prof Carroll, I just wondered if you have also been watching Brian Greene's "Your Daily Equation" ? I merely ask as a fan of both you and Prof. Greene. Thanks for this great new series BTW.
Where could we find an antiparticle for every particle in our universe? Just considering that time were going both directions simultaneously, every neutron in our universe's time direction would be its corresponding antineutron in the reverse time direction. Every proton, its antiproton. And so on. Total baryonic number in both time directions: 0. Total leptonic number in both time directions: 0.
A nice symmetry, two universes in one (the antiuniverse would however decrease entropy in its own time direction.... but "past" the big bang instant, and I mean "past in the reverse time direction," it would increase entropy as it goes longer and longer past that instant, whereas it would be our universe's particles that would decrease entropy before the big bang in our time direction.
Not sure if this all makes sense. . . . Could time really be both directions at once? Semantics are not really helping in such a situation, "at once" meaning "at every one instant" in this case.
the barion thing reminds me of cellular automata, where you have to input 1 cell for the system to start
Time slows down the faster you go. Mass increases the faster you go. Time slows down in the vicinity of black holes. Is there a law of conservation of time or is this a reflection of something else to do with the behavior of spacetime?
Take two rocks separated by some distance at time t=0. The universe expands until time t'=1, and now the distance between them is greater. The gravitational potential energy between those rocks should be greater now due to the increased separation. Shouldn't the same apply to galaxies? What am I missing?
Question about black holes
If from our perspective anything aproaching the event horizon of a BH slows down in time how can we see a BH grow. And how can we see two BHs merge. The only thing we "should" see is seeing those object freeze in time as they aproach the event horizon.
Thank you Prof. Carroll! This series are much appreciated for people like me that don't have the means to go to a university and learn from the best. I have a question. What about Hawking radiation, wouldn't that violate conservation of energy in some way?
The particle pairs from Hawking radiation borrow some of the energy from the black hope, so energy is still conserved. The black hole loses energy in the process due to the escaping particle
I don't know what it is, but I get way less out of these videos than I do from Sean explaining things, or discussing them, with another person present.
T.O.E thesis: The collapsed wave of probability functioning similarly at unsame scales has a different appearance.
Our sensory set reaches limitation of expected capacity at a different perceptual domains. In the same~ way, a planar observer of offset signwaves will see intersection at alternate opposite inflection points; where to a third-dimentional viewer, intersection within the same offset spiral-form waves never appears...
If you spaced heavy objects throughout the known universe would it bend the universe enough to win? I guess I'm asking is the constant dependent on the amount of stuff?
Trying to wrap my head around what happens when multiple worlds branch after an "observation" is made and how energy is conserved:
- Energy = x in the pre-observed world in which a particle is actually a wave
- An observation is made and the wave collapses into a particle; this now-entangled and branched world has energy = y1 < x
- For simplicity, say there are 3 total "entanglements" possible -> are 3 branching worlds thus simultaneously created? If N possibilities -> are there always instantaneously N branched worlds?
- For N branched worlds each with energy y (sub z) [where z is integers from 1 to N, and y1 may or may not equal y2 (etc...)], is it true that the summation of y1 + y2 + y3 ... +yN = x ???
How then is the energy in our continually branching world not tending toward 0???
Does anybody know if Sean Carroll ever does public speeches with meet and greets? That would be the thrill of a lifetime!
I will always refer to the wide eye slight lift of the forehead stripped of facial twitches blank canvas with the glistening twinkle of humor in the eye as the Sean Carol effect, I’ve tried so hard to do it. One day I’ll get it down
We know as a fact that the universe is expanding , which affects the space . And if space time is one thing in itself it should be affecting time too, right ? If that is true how does that happen ? And can we perceive this effect here on Earth ?
always wondered if it wouldn't save a lot of confusion among beginning physics students to write Einstein's infamy as dE/dm = c^2. Makes it rather obvious that the gain in mass in fission equates to excess energy which must manifest elsewhere in the system
A question on the conservation of momentum: Do two particles exist in the same reference frame at the same time - whatever "same time" can mean? ie, does a particle continue at a constant velocity because inertial frames are distinct and an interaction is required to destroy a particle in one frame and create some in other frames?
Enjoyed it
In the expanding universe do the energies gained by the cosmological constant and lost through redshift cancel each other out? If not is it possible that energy is conserved in the wave function of the universe (Hilbert space)?
Yes, that's what I was wondering (though I wouldn't have put it so well).
This is gold. Needs more subs!
thank you for this, einstein was before media, hawking couldnt talk, the world really needs to hear whats going on inside your brain, this mite be the most important thing on the internet
you will be surprised to know Einstein was a bigger media celebrity than all the Kardashians and clooneys and Pitts and jlos put together in his time. it is a tragedy that our celebrities are of such low quality.
I have heard your interviews in closer truth, as an athiest i would love to hear your videos and agree with the concepts
Fantastic , Thanks Sean
OMG! liked before watching.
Could you talk a bit more about:
If energy in an expanding universe is NOT conserved how (does it work) / why is the cosmological constant still fixed per cm of space and remains so, even as the universe expands?
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Is the conserved / not conserved energy in the expanding universe related to the many worlds interpretation? Something like: the total amount of energy remains constant just not in our particular universe?
Kind Regards and thank you so much for doing this.
Henry B. - Stockholm, Sweden.
A conservation of the one (energy) but not the other (mass) would violate the energy-mass equivalence.
In fact a hot cup of coffee has more mass than a cold cup of coffee, even though the total mass of any particle is equal in both cases.
"Mass" is not bound to the particles alone, but to the closed system "cup of coffee". And for closed systems the conservation of mass is still valid.
Freelanceteach vibes. Love it
It seems like a fudge if you are saying energy is not conserved in an expanding universe? If a photon is being red shifted In such a universe, where is its energy going? Can't this be transferred to the vacuum energy surrounding it and thereby conservation of energy is being maintained? This is besides the energy contributing to the expansion of the universe (undefined dark energy).
Thanks for answering my question!
thank you. thank you. thank you. a heroic deed.
Sean, in Hawking radiation, at the event horizon two virtual particles are produced as matter and antimatter. Is it true before they annihilate each other, they get pulled apart and one particle escapes into space and the other into the black hole. For black hole evaporation , does it matter which particle gets absorbed into the black hole ? Matter or antimatter ? Is it true it’s 50/50 which particle escapes ?
Im no Sean Carroll, but I know enough to help with your question.Yes, particle-antiparticle pairs are "ripped" apart at the EH. The outgoing particle always has positive energy since it requires energy to create said particle. This means that the other particle has negative energy - in the sense that it has to balance out the energy given away to the particle that escaped into space. Another way to look at it is that the particle that is created and escapes "steals" some of the gravitational potential energy of the BH to form said particle. And to the crux of your question: if the hawking radiation creates a charged particle, then it would randomly produce either +/- charge equally - Else it would become charged and quickly neutralize itself. Note: this doesn't apply to photons as they are their own anti particle.
Trebor Senaj thanks !! That’s the best explanation I’ve heard !!
Sean, did I hear you say "cow particles" at 16:15? Are those the spherical cows you were talking about? :^)
Good morning! If energy decays due to expansion, is there a relationship b/w dark energy & the vacuum energy?
I wish I had found this series in time to ask about the relationship of kinetic energy (1/2mv^2) and E=mc^2. Except for the “1/2” term the two fórmulas are identical. Since light is a velocity and since it’s the maximum velocity, is E=mc^2 not related to the kinetic energy of a mass moving at c?
Years after my two basic college physics electives, I thought I had some breakthrough understanding the intuitiveness of E=mc^2 when I first realized the similarity of the two formulas. But, I had forgotten the 1/2 term. Sadly, I realized after college so I couldn’t just ask my teachers in class the next day.
Thank you so much Sean!
Is time invariance violated in general relativity? (since energy is not conserved there)
What the heck. Thanks Sir. Great, absolutely great
Thanks Sean !
Keep it up! This is great.