The Maths of General Relativity (2/8) - Spacetime velocity

[@fyu1945]

This channel might probably my greatest Discovery since 3Blue1Brown. Just wanted to say I am absolutely astounded by your content!

[@brijeshsingh8460]

99 like and first reply 🔫 now reply "Noice"

[@brijeshsingh8460]

Noice

[@evilotis01]

saaaaaame

[@parassharma3567]

Same Here ! It's super lit

[@CrowKunCGS]

Yeah, I feel the same way too! But I would add one more channel to these: eigenchris. If you're interested in learning more deeply the mathematics of General Relativity, check out this channel, it's a REAL gold mine too: kzbin.info

[@Pidrittel]

“The maths of General Relativity” or “How Physics actually should be taught”. Simply brilliant.

[@Johncornwell103]

Well it depends on the type of physics being taught. None of this applies for newtonian physics

[@Pidrittel]

@@Johncornwell103 This comment was not related to the content but rather to the quality of the teaching. Of course, I am not saying you should teach GR as a general case, so that Newtonian physics just pop out as a special case. But I think, even as a physics student you can appreciate the nice way of explanation in this video. Of course, you can do your standard lecture of GR as kind of a soft differential geometry lecture (and if you do this for your professional background, it is nessecary that you understand all the details) but general relativity (as well as quantum field theory) belongs to the theories in physics where you cannot get clear enough in your notation to explain it as good as you can.

[@nanobruh]

U still dont have any idea of how things actually work : this is vulgarization not teaching

[@2xKTfc]

@@nanobruh Do you learn assembly programming by reading binary or by reading a textbook? You gotta start somewhere, and what you call vulgarization is a tool to achieve that. Not the only tool, but a helpful one if you know how to learn from it.

[@colfrancis9725]

@@nanobruh I can agree with the first half of what you said. However, it is "useful" if it gets people interested and it's also "useful" if they are pointed in the right direction. It is therefore reasonable teaching. This is "Edu-tainment" rather than a textbook. It's good for what it is. I don't know but I suspect the content creators are especially interested in testing out their new ideas for the diagrams, illustrations and animations. Some of these are good and may well get their way into other educational sources. (Just my opinion and I don't speak French well enough to fully understand what they were doing on the Science Clic French channel which is about 2 months ahead of the English channel).

[@Pidrittel]

How good can the visualization get? Alessandro Roussel: “Relatively good.” (pun intended)

[@elpak]

I project that, by the time you are finished, this will be the best explanation of general relativity available in the entire world for a low-level audience. Congratulations, it is looking fantastic. I am a Senior Lecturer at King's College London Physics Department, and look forward to the rest of this series.

[@colfrancis9725]

(Just my Opinion) I agree with what you've said. How do you think it will be for an undergraduate or post-graduate level audience? Would you consider adapting the way you draw spacetime diagrams to something like this in your teaching?

[@onicalcron3752]

I am excited so much I want to go orbit a black hole so I can come back with all videos uploaded

[@sidharthpattanayak9060]

you just going to mars and coming back will do the work and also save your money

[@sayKewal]

@@sidharthpattanayak9060 He was referring to time travel. But technically it will take more time to go to a Black Hole than to wait for the whole series.

[@colfrancis9725]

@@sidharthpattanayak9060 :) You know your stuff, just like the Twin paradox. Only, don't say Mars, make it a bit further and imply traveling a bit faster.

[@joeblow6413]

Or you could learn to speak French, because that version of the same video series came out about a year ago. Probably faster to just wait, though.

[@scienceium5233]

@@joeblow6413 could confirm

[@ClemensAlive]

Policeman: "You know you were speeding, right?" Me: "No. I just had a different vector through space time."

[@physicsquack7660]

Thats exactly the same thing? The derivative units are made up of vector components. Your position vector is your velocity through space time in the spatial dimensions. If he clocked your spatial dimension velocity as being over the limit in the spatial dimension, youre speeding in that particular axis. Your time axis would then change to compensate, slowing compared to "stationary".

[@WIDSTIGETHEVLOGGER]

Policeman: "Yes indeed, but your vector through spacetime had an angle too large in relation to the grounds worldline which is prohibited. Therefore I will need to give you this ticket." *gives ticket*

[@particularminer260]

1:11 “More generally, all objects in the universe move with exactly the same speed ... the speed of light” Perhaps this statement is intended to grab the attention of the listener. But while that’s true in the context of spacetime, our everyday use of the term “speed” is quite different. “Spacetime speed” is probably a better moniker.

[@banudi2]

thank you for clearing it up. I was confused

[@dblockbass]

This is the equivalence principle

[@gentlesingularity]

I didn’t understood this concept quite clearly esp why the speed is “speed of light” v = c. Can you elaborate this?

[@SD-sf8yj]

@@gentlesingularity imho, v=c is just a definition here, relating to the concept of 'spacetime'. it illustrates (as i understand) that time can be also be interpreted as a distance of 300'000km that light covers in space or, after this distance has been traveled by a lightbeam, 1s has passed. it does definitely not mean that a real apple will move at that velocity ;)

[@Sasukej2004]

This channel slowly gaining popularity is the best thing ever!

[@jiriverkijk9246]

Ngl I’m pretty excited, 10/10 best channel for relativity out there!

[@PoseidonWasTaken]

I like that these videos are so short. The math is kinda hard to fully wrap your head around and these small segments gives me time to absorb the info between videos

[@nero1612]

I really hope this channel gets the recognition it deserves

[@omaralhafez5014]

Same opinion.

[@archishmannag]

These 6 minutes feel like 6 days before premiere! From Einstein's theory of relativity!

[@imagine.o.universo]

Hello I am a bachelor and this was the first time I formally study general relativity. I can say that your work helped me a lot! It was brilliant! I believe this is the best material on the internet to explore the concepts behind this subject.

[@LagAttacktoSlay]

I really can't wait for someone to comment about their moment when it all clicked. It's really a joy seeing someone enjoy such topics, and you make it easier for us!

[@anywallsocket]

These explanations are not only logically and visually very palatable, they are like music for the coherence of my soul

[@mikemironov7551]

I just want to appreciate the production quality of animation! Whoever done this - great job!

[@ScienceClicEN]

Thank you :)

[@ozAqVvhhNue]

@@ScienceClicEN I would love to know the name of the background music

[@ScienceClicEN]

It's a personal creation you can listen to it on my SoundCloud : soundcloud.com/aroussel

[@ozAqVvhhNue]

@@ScienceClicEN Thank you so much ^^

[@Alex-bw6yd]

This series is sooooo god damn good. Literally the best way to understand Relativity. I had a pretty good grasp before but it was difficult, but the first video (and I'm sure the subsequent videos) was so good at breaking it down and really explaining how truly bizzare and amazing Relativity actually is.

[@enotdetcelfer]

Between this channel for relativity, and Atoms and Sporks for quantum mechanics, I'm loving all the "let's get a better intuition" stuff recently. I wish I had learned this in school first... it's sad we're still taught the old stuff first and then have to unlearn it in a sense. Can't wait for more vids to get translated!

[@ayushmaanyadav5280]

Thank you so much for doing this series in english. You guys have the best animation! Please do other topics too. Like coriolis force.

[@luudest]

I like the dramatic music in the background, and I like the series!

[@fernandofreitas2615]

I'm a "normie" who hasn't taken any university/college physic (I have some high school physics) and I'm amazed at how I'm getting a pretty strong understanding of the concepts around general relativity, especially after first watching your great "A new way to visualize General Relativity" video. Amazing simplification of complex concepts.

[@enotdetcelfer]

Showing the movement through time as the 3rd dimension like this needs to be the new standard for so many things. I feel like it gives a much better intuition of the different time perspectives involved. I feel like we're close to a unified theory when watching these xD good stuff

[@lIlIlIlIlIlIlIlIlI]

This channel is amazing. I feel blessed being able to grasp relativity so easily. Unlike other explanations based purely on math, these visualizations and crystal clear verbal explanations are incredibly helpful. I can't wait for part 2!

[@shanetroy111]

this is part 2

[@lIlIlIlIlIlIlIlIlI]

@@shanetroy111 At the time of the comment the video was on countdown for its premier. Premiered time is referenced under the title of the video and comment time is reference next to the commentator's name. Thank you.

[@DialecticRed]

It is amazing, isn't it? Alessandro does a really great job of making concepts easier to understand while not sacrificing the complexity and intricacies of the math within, and I've personally gotten a lot out of the channel so far. It's also suprising how quickly he's released the video, although I'm assuming he probably already made each of the videos in the series or at least most of them and releasing the videos periodically. Nonetheless, the amount of thought, work, and professionalism in his videos is astounding and the amount of views he has is mind bogglingly small for the quality of his content.

[@colfrancis9725]

@@DialecticRed Parlez-vous Francais? Because the French version of this channel is a couple of months ahead. So, yes, I guess it's all made and ready to go.

[@DialecticRed]

@@colfrancis9725 Oui, je parle un peu Français, mais je ne sais pas beaucoup. I'm not fluent though despite three years of language learning so I probably wouldn't be able to understand much, although perhaps that could be a way for me to practice my French. . .

[@NeedsEvidence]

1:45 Small technicality: If you measure time in *seconds* , and distances in *light seconds* , then the speed of light is not 1 but 1 *light second per second* (a *light second* is NOT a *second* ). You could, however, define the unit of distance as *1 second* (the _time_ representing the _distance_ light travels in 1 second). In this case, the speed of light is 1.

[@stanydevito]

This is legitimately the best animations and explanations I've seen before. I really think that your method is extraordinarily awesome!

[@HarhaMedia]

The production quality of your videos is top-notch!

[@ScienceClicEN]

Thanks :)

[@constantinandro684]

I couldn't wait for this episode so i watched the entire series beforehand on the french channel, so i guess will learn French.

[@haidaralhassan4621]

I just knew this. imma learn french too 🏃🏻🏃🏻🏃🏻🏃🏻🏃🏻🏃🏻🏃🏻

[@SHM910]

What is the name of the french channel?

[@tetraedri_1834]

@@SHM910 ScienceClic

[@akhilanr1233]

really true, i have been trying to learn g r from different places, tried almost everything, books, videos, internet, the actual g r paper by einstein but no one is giving me an explanation for the many questions and doubts i have. this series looks promising, so i really cannot wait every week. exited for the rest

[@kazharding]

I've wanted to learn the maths behind general relativity for a while now, and finally i found a series that makes it easy to understand! the only downside is I'll probably end up watching all the videos on your channel instead of doing my actual homework hsjsgsj. anyways, just wanted to say what a good job youve done on these videos, amazing!

[@joseville]

1:15 What's the fastest object in the universe? General Relativity: yes (Thanks for these awesome, amazing visualizations and teachings!)

[@UKtownsendj]

Exactly how it should be, this is so simple and extraordinary! Well done!

[@pedroarthur4623]

The project of this channel is simply brilliant

[@cubeik-jakubvlcek698]

Well I do not often write comments anywhere but I have to do it now. I just want to thank you for all this stuff, you make it possible for normal people to understand such difficult concepts like relativity. I've always been in love with physics and only few understood me. But with creators like you, I don't feel so alone anymore. Btw it is almost 12 pm and I am sitting in my bedroom just taking some notes and trying to comprehend. Just thanks!

[@malakaibarber]

Brilliant source for the general public to learn more ‘in depth’ understandings of pop science

[@ayusshanubhav2097]

This channel is growing so fast. love it ❤️

[@georgeclinton3229]

This is the best series I saw in a while (the previous one that made me this exited was Naruto, but that is an other subject). I don't know about others, but this is like a good movie for me, like Matrix but in reallity. The history of physics is really cool, like how they developed each others ideas into finding out the truth about reality. I learned electric engineering at university that involved only a segment of how phenomenons work. Physics class was pretty much a survival for me, I was very young at that age, and the way they taught us wasn't the best I think. This video explains things much clearer and gives way better visual presentation than that my professors did at a white board with a piece of chulk. Good job! I can't wait till Part 3 comes out.

[@ScienceClicEN]

Thank you I am very glad you like the series ! The 3rd part is coming tuesday I hope you'll like it (I loved Naruto too when I was younger ahah)

[@wolfpackproductions.notfurries]

Love this channel! Most simplest explanation of genral relativity

[@kuboteusz]

I'm utterly impressed by your fresh approach to the subject. Bravo.

[@imaginer04]

Brilliant visualisation of math. Enjoying these videos. It makes sense to me.

[@ScienceClicEN]

Thanks !

[@Scriptum_1]

This vids are so great ! I can imagine some day when teachers teach this on high schools and general relativity would be a reachable subject

[@quaxenleaf]

What a wonderful gift at such a critical time; thank you for your incredible contribution to the understanding of a complex scientific principle.

[@piotao]

AWESOME. Our world need more explanations like this!

[@lilyh4467]

This should be mandatory content for physics courses.

[@dofalol]

I have never grasped or explicitly seen the statement that "all objects in universe move with exactly the same speed" through space-time, but hearing that in this video made a lot of things click for me. There were basic things about time dilation I was usually unsure of and had to always check, but they can easily be resolve with that fact in mind.

[@robo7th]

I need to rewatch this 2-3 more times. to fully understand this simple concept.

[@juijani4445]

Discovered your most popular video today. You get A+++ for fantastic narration, accurate & high quality visuals and just cause it's physics! Subscribed + all notifications ON!!

[@ScienceClicEN]

Ahah thank you very much !

[@dan9948]

I can't wait for the rest of the 8 videos!

[@koushalkrishna]

You earned a sub my guy! Really impressed with content. I was searching for this for a long time. Thanks!

[@maurocruz1824]

For a mathematician, what you're saying is that you are parametrizing a curve by its arclenght. And that's why the module of your velocity is constant.

[@Mysoi123]

from a mathematical point of view, the spacetime velocity vector is a unit tangent vector.

[@darkshao51]

Great video as always! The animations are always incredibly well done. I can't wait for the next one!

[@NovaWarrior77]

Einstein notation, explained in a comprehensible way? Inconceivable!!!

[@Laff700]

I fin tensor notation to be more logical than Einstein notation.

[@ScienceClicEN]

The problem with tensor notation (with all indices down) is that this does not differentiate between covariant and contravariant indices. In terms of differential geometry this is essential because indices up / down represent different geometrical objects (one-forms / vectors). Tensor notation is usually used as a special case of Einstein notation, for a euclidean metric, when you can just lower/raise the indices without worries

[@NovaWarrior77]

@@ScienceClicEN I...respect the answer *blink blink*

[@Frotdog]

The expression ||v>|| = c typically refers to the magnitude of the velocity vector being equal to the speed of light, c. This applies to massless particles like photons, which always travel at the speed of light in a vacuum. So, for massless particles, the magnitude of their velocity is indeed equal to the speed of light, but not for “all objects in the universe….denitwd the letter c”. Can someone clarify this for me?

[@kartikkhurana4266]

They do, the value of their proper time changes.

[@nahommerk9493]

This is such a great video for learning advanced physics! I sure do hope the next parts are coming soon!

[@ScienceClicEN]

Thanks ! One video each week, next one on tuesday ;)

[@Cettywise]

Yo, you're breaking this shit down! Thank you so much and please keep up the good work

[@leapdaniel8058]

Metric tensor coming in part 3!

[@-_Nuke_-]

Astonishing work! These videos are a work of art!

[@tolgaerguner5246]

in 1:15 , you mentioned that ''all objects in the unvierse have exactly same speed which we call light of speed'' But all object in the universe have different speed, I cannot get it this point. Can anyone explain ?

[@Mysoi123]

The total speed is the same but their velocity along each coordinate can varies. If the car is moving 60 mph to North-east , then speed in the east direction can vary if the car change direction.

[@ishikani]

10/10 animation, definitely subbed.

[@ScienceClicEN]

Thank you glad you liked it :)

[@dinodinoulis923]

Great! Really clear explanations and easy to follow so far.

[@Fzlse]

You’re videos are literally the best

[@deeptigoyal4950]

Your videos help me understand the basics of GR thanks for that Also your animations are super great.👍🏻👍🏻👍🏻 They really make difference in your videos Happy to find this channel

[@israsayed]

I am so glad I have found this channel so early while it's becoming famous

[@nisaxaxa123]

First thing on my to-do list today. Very well done, cant wait to see more.

[@MinibossMakaque]

I think I'm misunderstanding something at 5:03. This seems to suggest that the greater the satellite's velocity is given to it's time component, the faster time passes for us in relation to the satellite. Isn't it the opposite?

[@ScienceClicEN]

Beware, that's an important point, it's what was emphasized at the end. The coordinates are *not* physical distances, so you cannot just "rotate" the vector on the grid, and expect it to keep the same norm. In particular, if you want to change the direction of the vector, you must account for the change of norm (it's done with the metric tensor, we'll see that later). This might be confusing because I used the image of a circle in my video "We all move at the speed of light" : in this video it was *not* the components of the spacetime velocity that were represented, but the observed velocities (the ones measured with respect to the observer's time instead of the proper time of the object)

[@konradschulz7567]

I just yesterday discovered you and holy fuck I learned more in that 15 minutes than in my entire 10 years at school. I love you. And the are forces an illusion video is a masterpiece, so is the visualizing of space time. I love you.

[@Hello-qg4yk]

YES DEFINITELY

[@alteskonto1145]

Oh damn you was 19 years in school? Must've been hard

[@konradschulz7567]

@@alteskonto1145 lol I typed it wrong

[@konradschulz7567]

@@alteskonto1145 I actually skipped 2nd grade

[@jolez_4869]

This series is so good!

[@burieddreamer]

This channel is underrated.

[@bkkhanj]

so nice and perceptive approach. Thank you.

[@petrowi]

Awesome content. One thing to consider is demonstrating the actual scale of relative motions of everyday objects, such as earth an apples - they travel in *almost* parallel paths and the highly curved paths traced in the animation don't show that. For example, Earth and a satellite would both have speed c in 4D space, and if Earth observes 300000km/s for c, it would observe 299,999.9999 km/s for the satellite with its time dilation. Essentially, the cylinder in your animation would be stretched out to the point where the spiral drawn around by the satellite's worldline is *almost* parallel to the axis of the cylinder - the Earth worldline. While such drawing wouldn't illustrate well the concept, it can be shown briefly for the viewer to get a better understanding

[@onit996]

Nice videos :D Really looking forward to the next ones! I always thought general relativity to be way over what I will ever process, so I'm excited to see if I can understand your videos. :)

[@animeshkarnewar3]

Some really cool visualizations! Good job!

[@AverageAlien]

Thoroughly enjoyed the video. Great work.

[@meowwwww6350]

These videos are in the level of brilliant. Org!!

[@9146rsn]

I am deeply grateful for this wonderful presentation. Hope I could collaborate with people such as you and live a more fulfilled life :)

[@JM-gj7de]

Hurry...I need all eights vids!!!:)

[@michaeljburt]

This simple but effective approach is really artful. I'm a student of general relativity, in the sense that I've spent a long time trying to understand the math. And everything here is rock solid, and not necessarily the viewpoint I have come it from before.

[@drakodrako100]

How could you have done something like that, its actually perfect, thanks for doing this videos they really teach me a lot, I am in a point I want to learn teorical physics and you made my dream possible, thanks :), just doing this video I really really wanted to understand how the General Relativity works with maths. Thanks.

[@hungryformusik]

5:14 How is it possible geometrically that the time component is bigger than the proper time ?

[@ScienceClicEN]

This is a very good question. It would not be possible if spacetime was euclidean (using the Pythagorean theorem). However spacetime is not euclidean but Lorentzian : in a Lorentzian space if you go from A to B in a straight line it can actually be longer than going from A to C and then from C to B ! This is because distances in a Lorentzian space are measured with what we call a "pseudo-metric". This will be explained in episode 4 ;)

[@Prof-Joe-H]

Absolutely stunningly wonderful. And even more importantly: perfectly correct! (Sorry for the many -ly words.) 🙂

[@ScienceClicEN]

Ahah thanks ! Glad you liked it :)

[@colfrancis9725]

I'm confused and forced to reserve my judgement until the next video. POSITIVE: A lot of this is very good. Well done and thank you very much. The amount of writing in this section (POSITIVE stuff) isn't proportional to how good this is. There's more writing about the negative stuff because I am just so desperate to sort out these problems. NEGATIVE: Your resolute determination that worldlines are cut into equally spaced chunks of proper time through part 1 and now also part 2 of the series You draw spacetime diagrams and often make statements that force people into thinking the arc length along the worldline between units of proper time is constant. Only at the end of this video do you suggest that Pythagoras' theorem or the conventional Euclidean approach to determining that arc length isn't going to work. Well, this is ok, or it could be ok depending on what you do in the next video. However, you simply wouldn't have that problem if you hadn't insisted that the chunks of proper time were equally spaced along the worldline in the first place. QUICK QUESTION: How would you draw the worldine and mark out the chunks of proper time for a particle that moved at a constant velocity with speed

[@ScienceClicEN]

Actually the geometric distance between the intervals of proper time *is* constant, this is because proper time is an affine parameter of the worldlines. Now if you try representing it in a spacetime diagram, because the distance used is not euclidean but Lorentzian it seems as if the intervals are not equally spaced... but they are really. So I decided to start this series with an euclidean approach, introducing the concepts of differential geometry first on Riemaniann surfaces because euclidean metrics are much more intuitive for us.

[@colfrancis9725]

@@ScienceClicEN Thank you very much for this reply. You took some time to address a question that is antagonistic to the teaching method you have chosen, rather than just ignoring it. You deserve recognition for that. For whatever it is worth, I am much more likely to recommend this series and the methods you use to others. I'm interested to see the over-all effect on students caused by the teaching method you have chosen. You have moved a learning demand* away from many concepts such as worldlines and spactime diagrams but increased the learning demand elsewhere. Specifically, students may be more reluctant to accept that a Lorentzian metric instead of the Euclidean metric must be used. The learning demand required to actually construct and draw worldines of the type you are using, instead of just looking at some you have already drawn, may also be large. In order to maintain the appearance of constant Euclidean distance between proper time units, the co-ordinates along the axis of those worldlines would need to be compressed or stretched (determined by the motion of the particle). There is also a problem if you tried to show TWO worldines on the same diagram. Suppose you wanted to consider the usual Twin Paradox of special relativity: If the students expect the units of proper time to be equally spaced, they will measure the arc length along each worldline to obtain precisely the opposite (wrong) idea of which twin experienced the least proper time. Best of luck to you. You are doing well and getting many people interested and motivated. Your concept is a good one and I'm sure it will help to explain the science in some situations. You seem to be interested in developing animations, images, diagrams and other visual tools that will aid in Science communication. I am merely pointing out that this idea may be helpful in some situations but it may be putting a higher learning demand in other situations. [ * "Learning demand", as discussed in this article: Leach, J. and Scott, P. (1995). "The demands of learning science concepts: issues of theory and practice". School Science Review, 76 (277), 47 - 52. ]

[@typha]

at 6:29, that's not how orbital mechanics work. The satellite that is further away ought to be moving slower, and the same could be said of its angular velocity. That may or may not have anything to do with your point, but maybe you could have used something other than satellites to illustrate it.

[@ScienceClicEN]

Yes indeed it's important to clarify : if they were to follow orbits in free fall then the satellite which is further should be slower than the other one. Here I was just talking about two trajectories (not necessarily in free fall), to show how two vectors that have the same components can have different lengths depending on where they are located. The idea in this series is to start from scratch and forget everything we know about physics, so at first we are not supposed to know that this situation would not be physical.

[@gbeziuk]

I hereby sacrifice this comment to the omnipotent algorithmic g-d of KZbin, so that this really worthy video will get more popularity.

[@idirkhial9422]

Really looking forward to it!

[@apm77]

One thing that this presentation leaves out is the method behind the madness of notation conventions. People will be confused at how an index can sometimes be up and sometimes down, and how you know it's an index and not exponentiation. These questions have answers but that's a different video series. To what extent is this an obstacle for people?

[@yingmingyang1460]

Am I the only one that understands almost nothing but still gets excited😂

[@smzakirhussain7604]

The BEST simplification!!!

[@kennethhicks2113]

Great stuff! I think you should review the last minute as the satellite ex. can me misleading in that during the same amount of time they subtend the same angle....they don't. Can't wait wait the next one, great start on youtube btw, more education styles/info the better : )

[@maurocruz1824]

5:22. That doesn't violate triangle inequality?

[@ScienceClicEN]

Good catch, in relativity the metric is not euclidean (it's not the Pythagorean theorem) but Lorentzian, this means that the triangle inequality is opposite : the path between A and B is always *longer* than the path between A and C + the path between C and B. This is explained at the end of episode 4

[@IsaacNewton1687]

4:50 flat earthers with no knowledge in coordinate systems are like "he proved it" 😂😂

[@nexyboye5111]

very nice and clear video, keep up the good work

[@piosol4521]

Very well explained!

[@kingsizemaster]

Nice video, thank you for the explanation, but I didn't get a part very well, the part which says all objects in the universe move with exactly the same speed (the speed of light), whay does it mean?

[@ScienceClicEN]

Beware I am talking about motion through spacetime, not just motion through space. I have a video about this called "We all move at the speed of light"

[@balabuyew]

@@ScienceClicEN This is a good question. However, in mentioned video (We all move at the speed of light) you do not describe WHY is that.

[@Smitology]

@@balabuyew In a way it's a postulate of relativity, if it were not true, then predictions would not match with experiements.

[@ticoq179]

at the minute 1:13 is a fact or an assumption when you say that we already move at the speed of light?

[@wejdentrabelsi6919]

m so excited to finish this it feels serious n real idkidk m excited thank u sooo much

[@bejond9118]

What is this background music you are using? Does anyone have a name or a link for me?

[@ScienceClicEN]

It's a personal creation you can find it on my SoundCloud : soundcloud.com/aroussel

[@bejond9118]

@@ScienceClicEN thanks! PS: I love your videos and this background music is awesome! Keep it up :)

[@ScienceClicEN]

Glad you like my work !

[@bjornfritz9219]

That last example with the 2 satellites is brilliant

[@devrim-oguz]

Great, intuitive animations!

[@kcm624]

At 5:20 there is a triangle where one of the sides is 2s long and the longer side is 1s long. Is this a mistake?

[@shmuelmunitz9934]

I didn't understand that but about writing the vector as it's the sum of it's components times the basis vector. Can someone explain it? 3:20

[@Mysoi123]

eo and e1 usually have the length of one. which means 2eo = 2 basis vectors, each has the length of one. if the eo has the value of 2, then 2eo = 2 basis vectors each has the value of 2.

[@houssemharrak9060]

A perfection in explaining

[@emanuelvendramini2045]

I have seen some eigenchris videos but, damn! this is better!