The Origin of Matter and Time
Vložit
- čas přidán 30. 05. 2024
- What are… things?
Tweet at us! @pbsspacetime
Facebook: pbsspacetime
Email us! pbsspacetime [at] gmail [dot] com
Comment on Reddit: / pbsspacetime
Support us on Patreon! / pbsspacetime
Help translate our videos! czcams.com/users/timedtext_cs_p...
Now that we’ve broken down our preconceived notions about mass and time, let’s redefine what they really are. Since we know that time is not a universal constant, what is? On this week’s Space Time, Matt defines causal order and explains how even though time may look different to multiple observers, it is the one concrete reality that we can all agree on.
The True Nature of Matter and Mass
www.youtube.com/watch?v=gSKzg...
When Time Breaks Down
• When Time Breaks Down
_____________________
FURTHER READING:
Lorentz Transformation
en.wikipedia.org/wiki/Lorentz...
_____________________
COMMENTS:
Endre Kovács
• When Time Breaks Down
ectoplasm2369
• When Time Breaks Down
BrunoJMR
• When Time Breaks Down
______________________
Written and hosted by Matt O’Dowd
Made by Kornhaber Brown (www.kornhaberbrown.com)
![[柴犬ASMR]曼玉Manyu&小白Bai 毛发护理Spa asmr](http://i.ytimg.com/vi/0TsXQ7z2Dh4/mqdefault.jpg)
"If you are seeing an apparent paradox, that means you are missing something" -- This is my quote of the year
>>> this sentence is a lie
i'm sure i wasn't the first to come up with it, when i apparently destroyed the quote of 2016 decades earlier as a teenager
hahaha
Paradoxes exist, like the concept of atheism (which is a system of belief in which systems of belief are seen as harmful and useless) but if you said instead something like “if you are seeing something that appears true yet defies then you are missing something and it is not true”.
This is part of why Moshe’s Teaching (Moses’s Torah), which is a lesson in Logic (The One True God), says not to follow your heart (feelings) or eyes (what appears to be) which have misled minds in the past, but rather to follow and devote our minds to The Source of Knowledge (Logic) who is The One True God (who actually makes x=x and makes the universe equal the universe).
@@goartist A sentence that is true must not be a sentence that is false, by definition.
The True God (Logic) is not a false god (that defies Logic), by definition.
Hey SpaceTimers, the "old guy" here. Here's a fun problem to work out that I mentioned to Matt after I saw this vid. It concerns the moving photon clock that appears on the spacetime diagram starting at 4:08. Read further if you enjoy working out fun physics problems (*cough*, +Gareth Dean , *cough*)...
In the spacetime diagram in this video, the moving clock and the stationary clock have their mirrored walls _perpendicular_ to the x-axis, i.e. the x-axis pierces each of the clock walls. In contrast, in the previous videos (and at 3:37 in this video), the photon clock walls are _parallel_ to the x-axis, i.e. the x-axis runs through the gap between the walls without touching either wall. Now the orientation of the clock doesn't affect the correctness of anything that's said in this video. But it does bring up a curious point.
See, if the clock walls are parallel to the x-axis, then when the clock moves in the x-direction, a stationary observer says it takes the same amount of time for the photon to move from the bottom wall to the top wall as it does to move from the top wall to the bottom wall. Both those "half-ticks" are seen to take more time than they would if the clock were stationary -- as Matt explained in the earlier video, that's because the photon in the moving clock travels a much longer diagonal path -- and so the "full-tick" of going bottom wall to top wall back to bottom wall is also longer compared to the full-tick of a stationary clock. This is time dilation.
But if the clock walls are _perpendicular_ to the x-axis, things are a bit different. A stationary observer will still say it takes longer (compared to a stationary clock) for the photon to go from the left wall to the right wall. BUT she will say that it takes LESS TIME (compared to a stationary clock) for a photon to go from the right wall to the left wall. This is why, at 4:11 in the video, the yellow dashed lines that go up-and-right trace out more time (vertical separation on the diagram between the endpoints of that line segment) than the yellow dashed lines that go up-and-left. In other words, "half-ticks" going from left to right take MORE TIME, but "half-ticks" going from right to left take LESS TIME, compared to the corresponding half-ticks of a stationary clock.
What about the full-ticks? Evidently, based on the diagram at 4:33, they are longer than full-ticks for a stationary clock -- in other words, the left-to-right half-tick of the moving clock must be time-dilated enough that, even with the shorter right-to-left half-ticks, the full-tick experiences a net time dilation. But... how does the _amount_ of time dilation for full-ticks of this moving clock compare to the time dilation for full-ticks of that other moving clock whose walls were parallel to the x-axis? More, less, or the same?
Fun exercise -- *prove* that the net time-dilation is *the same* for these two moving clocks (it had better be -- otherwise, the degree of time dilation will depend on how things are oriented in space and on the direction in which they move, which would be super weird). All you need is some basic formulae from special relativity (time dilation, really), some careful drawings, a bit of thought, and a pinch of algebra. Go ahead and discuss in the comments if you like. Or not. Up to you.
Enjoy. And I'm pumped to see that the Space Time community is still active and thriving. And growing! Keep it up!
--Gabe
I read all of this hoping that i could solve this,but this needs calculations and i have no clue
Damn, you type fast as you talk :D
Pierre LeDouche quite the opposite honestly. When you truly have an understanding of these things it changes everything about the universe for you. It’s fun to wonder but jumping into the proper understanding of these things takes you to places that are truly beyond your imagination. Take the blindfold off, trust me. You will not regret it.
The diagram only have one dimension x, that's why it looks like a problem when you try to put a 3d clock in a 1 dimension diagram. Or at least that's how I think of it.
@Pierre LeDouche I understand it abit more than you do-that is I understand all the concepts and I understand the basic equations underlying it, whereas I would not understand your field, and I find biology harder in general. But I assure you that the google-eyed wonder never stops. I actually find the large macroscopic scales of reality much more wonder-inducing. For me the quantum level is where reality has not yet fully formed, which is why the location of electrons can only be described in terms of the probability of them being in a certain position, as they occupy every possible position as a wave function until a measurement by an instrument or an observation by a person takes place. Reality is observer biased-participatory, see the eminent physicist john archibald wheeler, and one of his papers- philpapers.org/archive/WHEIPQ.pdf--- he was the man who wrote the standardised paper on einstein's general relativity, and coined the term 'black hole' among other things. Probably the greatest theoretical physicist following Albert Einstein. Being in the field of neurophysiology, the observer-participant nature of quantum mechanics should fascinate you. I think Stuff is more than the sum of it's parts. Certainly all sentient life is.
I'm applying to the Arecibo Observatory Space Academy Spring 2016 in Puerto Rico and they sent us an email recommending us to watch this video since they may ask us questions about it on Orientation Day. When Mark said he recommends us to watch those two videos first I quickly did. Now I love this channel and I've already watched over 15 videos here today. Keep up the good work! It's fantastic!
+The Doctor Really? That's very flattering. Thanks Arecibo!
Can you please explain what was going on? I don't know that much about physics.
Rip arecibo :(
So how's that working for you?
@@jonnyj. I think they are going to build another
Outstanding series! You're doing a great job with the CZcams format: short, challenging, fast-paced explanations that build on earlier content. Truly brilliant.
PBS, please edit all these videos together into a single cohesive episode so that I can throw money at you to acquire it. These episodes (especially recently concerning all the "nature of stuff" videos) are REALLY well done. Everything is presented in such a very concise and clear, easy to understand way. And this gentleman does a great job presenting. My daughter is still very young, but as she gets older I'd love to have all this together to show her. I'd love to have this sort of video on constant repeat than Dynotrucks or whatever the hell kids watch now-a-days.
Punky Rooster No Barney? Good luck getting any pre-physics graduate degree child to understand PBS Spacetime.
agreed these videos are amazingly well-done
I don't understand much of it but get little bits and I love watching them, I find them relaxing.
Alan Lee- While I am able to understand most of the content but I agree these videos are extremely relaxing. Its just comforting to know there are smarter people than me who have the time to study and fully understand this stuff. 😌
The amount of background needed to understand these videos is much less than people estimate - just a basic understanding of classical physics and its evolution (and some chemistry), which is taught in science courses at any respectable high school. This show has a giant potential viewer base that just needs a spark of interest.
Those animations tho(ugh) & that science tho(ough)! Awesome video guys!
***** Wow, thanks :D
Mikko Finell I don't care if people think I'm stupid or not. You're thinking about it too hard, don't hurt yourself.
Is it really that hard to type "though"? If you're going to write it incorrectly, you might as well use the even stupider "doe" version. "Ah yeah, that timeline doe!"
+Alexander Krivács Schrøder
Y r u tryin a b a grammr nazi on teh interwebs? R u nu 2 this? My 1st time on the internet was hard, 2. LOL ROFL WTF SMH
Mark Romano Nah, I just haven't had a sharp object penetrate my brain's language center like you.
"In this picture, time and mass and matter become emergent properties of the causal propagation of patterns of interaction between timeless, massless parts."
Anonymous time and matter are relative and have no owned properties but are dependent upon their subjective perception.
"This clock is a thing." followed by the smoothest most nonchalant catch I think I've ever seen. Well done, sir!
Came here and was the 2000th viewer and 200th like, this must be a sign.
That I need to stop noticing these patterns.
I'm 2081 view, 218th like. yay. Patterns.
+brianpso
4460:444
4500,450 dude, and when we will get the result of the Challenge?
+brianpso views: 6,271 and Likes: 627. Close enough?
i observed these patterns all over you tube... it is at the majority of time like this example: 10000 subs, 1000 views, 100 likes, 10 comments... always one is 10% of the other... is kind of interesting...
The visualisation of time dilation in this video was super awesome. This is a really weird effect to try and picture in your mind's eye because it seems so counter intuitive. So having a really clear representation is incredibly insightful. Thanks!
The "twin paradox" has been driving me crazy since I first started learning special relativity. Thank you for the resolution
this still drives me crazy. in PBS space time they tell us its the acceleration. but in Fermilab (also a greate place for physics) he telles its that you are moving from a frame of reference to another. whats right? czcams.com/video/GgvajuvSpF4/video.html
@@danielhermansen2300 Yeah, the acceleration has nothing to do with it. If you assume that near instantaneous acceleration to near light speed was possible (and wouldn't kill you) then the general relativity component would be negligible. As Dr. Lincoln showed in the Fermilab video, you can do it with NO acceleration. The key is that two different inertial reference frames have to be considered (either two for a single twin that is traveling) or one each for two observers (B and C in the Fermilab video) and that breaks the symmetry of the "stationary" observer and the "traveling" observer(s). I think the Minute Physics guy also did a video on it that explained it using space-time diagrams. I found it to be a very satisfying explanation.
@@rancidbeef582 thanks for giving me more inside in this. its realy easy to missunderstand stuff in relativity and fysics in general
@@rancidbeef582 it can be thought as a result of an acceleration as well
@@rancidbeef582 I would say that Minute Physics isn't really trustworthy. There's a lot of unsupported claims and speculations made in those videos. Regarding the special relativity solution, I was under the impression that you had to assume an instant inversion of direction for the traveling twin, which is not realistic. There may be a way around that, but if so it's difficult. Regardless, the symmetry breaking is the key component, as the two travelers do not have congruent frames of reference.
I've been watching a lot of these space-time-centric videos lately, I think every one you'd produced. But I hadn't seen this one. I could feel myself gradually "getting it", but some concepts, like different-perceptions-of-time-but-same-order-of-events, still confused me.
Enter the Rainbow World Line: seeing those beautiful colored individual light-like paths ricocheting through space and time, and the subsequent event lines they mapped to on the time axis was TOTALLY FREAKING AWESOME!!! Such a solid and simple representation of some concepts I thought I might never understand.
Fantastic educational tool.
I'm sitting here eating chocolate cookies while watching this video. I like chocolate cookies, they're simple, they no make my brain feel not good :P. Great video!
+Odgob Chocolate cookies are also ensembles of timeless, massless particles, you know?
+PBS Space Time dont ruin chocolate for him
+Eden Lumbroso Actually, they just made the cookies even better!
+PBS Space Time
If chocolate is massless, can I eat as much as I want without gaining weight?
+Michael Sommers An ensemble of timeless, massless particles is not necessarily massless.
This episode and the couple of others before this are some of the best on this channel
He went from difficulty level 0 to 100 in 7 minutes.
Yeah physics be like that lol
He usually does that! 😂
After reading this comment I skipped the video!
Watch his previous sessions carefully .. you'll get everything very easily
hahaha
11:27: You can also explain the twin paradox just by using the SRT. So, instead of taking a look at the acceleration, you need to use different inertial systems. Then you need to keep in mind the fact that different observers experience events at different times. Therefore you need to have a closer look at the Lorentz Transformation for time.
--------------------------------------
Explaination with SRT
--------------------------------------
1.: Person A remains at planet earth, while person B (the astronaut) travels at 80% of speed of light to a 6,25 Lj remote star.
2.: Person A as well as Person B have each one syncronised clock.
3.: At the beginning of the travel both observers are on planet earth. According to A and B:
(t_A= 0 ; t_B = 0) | (t'_A = 0 ; t'_B =0)
4.: Let us say that the travel lasts "5" years according to observer A. Because of length contraction, the travel lasts only "4" years according to observer B. In observer B's perspective A's clock shows that only "3,2" years have passed, bacause of time dilatation. So:
(t_A = 5 ; t_B = 4) | (t'_A = 3,2 ; t'_B = 4)
5.: When observer B arrives, he changes his inertial system while stopping his spaceship. So, according to Lorentz Transformation of time, the clocks (for observer B) show this time:
(t'_A = 5 ; t'_B= 4).
6.: So Observer B travels back home but because of Lorentz Transformation the clocks show this time (he changes his inertial system again):
(t'_A = 6,8 ; t'_B = 4). But the clocks's time according to observer A are still:
(t_A = 5 ; t_B =4).
7.: While traveling back home according to A "5" years and according to B "4" years pass by. After having arrived observers A and B compare the times of both clocks:
(t_A = 10 ; t_B = 8) | (t'_A = 10 ; t'_B = 8): The traveller (person B) is "2" years younger than person A.
These episodes resurrects my brain..
“In the beginning the Universe was created.
This has made a lot of people very angry and been widely regarded as a bad move.”
???
It still stands it was created.
What have you heard here which shows matter not created? This is how creation happened.. big bang should ring a bell here
kop pite where did that matter from the Big Bang come from
@@ebonezbart matter is energy.. BB was a high pount of energy which exploded and later cooled as matter. Read on how it possibly happened.
That is how creation happened.
Don't panic and remember to take a towel with you...
@@ebonezbart Since BB contained all physical reality, it had to come from a non material (massless, infinite [timeless]) source.
The last few videos have been hard for me to wrap my head around, but this one did an excellent job of wrapping them all together into one mind-blowing package. Great stuff!
Thank you for not being afraid to explain complicated things. There are lots of channels that just focus on the same popular physics material so it's nice to see something new to learn from.
"What is a thing? No mystery there"
Saying that will get ya slapped by a metaphysicist.
But this is about natural science.
the video was titled the origin of matter but it wasnt = clickbait
I had a math teacher who while doing proofs would make a statement like "We know that such-and-such is true, by 'obviousness'" instead of "By contradiction" or whatever proof method. "By obviousness." XD
I love this show. You're such an amazing teacher
I have been searching this video for a long time to understand time. I finally found it. Thank you guys. You are doing a great job. The best science channel I have seen, where you talk things in detail. The whole series of E=mc2, speed of light, matter and mass, time and this video, the best. Thumbs up!! Keep going.
First i saw a different episode of this channel then I saw another suggestion that made me more curios then i saw another suggestion then I go on watching videos continually. Man this channel is amazing. Nice work, keep going....
Best illustration of a Lorentz transformation I've seen, very understandable. Great video!
This was so well explained; top stuff.
What a fantastic channel, thank you guys! I have to rewatch all these several times to really understand them, but that's just because of the material. You guys do a great job explaining it!
Woah, really had to strain to grasp this one! That said, I love how you don't dumb down these videos. Keep up the great work!
This is such an awesome channel...
"We'll get back to why this is a good measure of time, in a minute".
The channel is taking an awesome direction. Keep it up guys! Much love.
Fascinating interpretation, one of the most interesting videos I've seen on CZcams. Thanks.
love you guys. love the uploads. all love round. mkayyy.
Those visual aids are perfect.
it feels like PBS beneficiate from luxury to have a graphics team! big big big help here Not everyone on this wide web have that fortune
"In this episode we're going to rebuild our understanding...of matter and time." That's exactly what you did for me with this video. I took college physics in the 1980s and since then have tried to keep-up with a layman's understanding of new developments in physics. That means my understanding of physics has seen only incremental changes to a mental model that's 30 years old for me now. In these videos you completely demolished my old mental model and provided me with a much better, much more interesting model. I'm really, really grateful. This entire CZcams channel is excellent obviously, but this short series on the nature of matter and time have just been outstanding.
The very best explanation yet for matter, energy, mass, and spacetime. But a little too fast paced. We need a revisit if these at a pace slow enough to gynormousness of all this.
Could you guys do an episode on Quarks and the gluon field sometime?
I've never been able to find a really good explanation for how that works so far.
+Hatdude man Anything in particular that concerns you?
Veritasium
Does your beards growth feel a difference in time dilation as it accelerates out of your face so we can admire it a little longer?
Hi PBS Space Time!
First of all, congratulations for your CZcams video series,
you're doing a great job of explaining science and getting more people involved in it.
In the series of videos about time ("When time breaks down", "The origin of matter and time"), you spoke about a very interesting idea about passing of time depending on the internal structure and evolution of particles and atoms, and ultimately on motion.
I got particularly curious about the idea, and I was looking for some more precise reference about it (I am a physics PhD, so it would be wonderful if you could point me to some paper or book).
Thank you very much in advance, for the references and for your awesome job!
Awesome video! This serials were a mind-breaking! Congrats! Keep with the good job!
It is the most mindblowing experience to realise that all our common "concepts" (ex: time, space, mass, energy, motion, acceleration) are not isolated but one.
Essentially, Physics is an attempt at breaking down the world by describing its properties, one by one, while keeping in mind that none of these properties exist separate from each other.
The bigger picture + the details x synchronicity = totally addictive mental stimulation.
I just love this channel: its host has rocket sense of humour... :)
The implications of this raises some serious existential questions. I wonder if this is something that commonly bothers people who study fundamental physics, or do they just go to the Rick and Morty school of indifference, like:
"Everything is an illusion, free will doesn't exist, and nothing has an purpose. Now let's go watch TV."
+AFastidiousCuber
kinda why im watching. And, i think, why you are too.
+AFastidiousCuber I have found the physicists I know have some deep beliefs on such things, often as part of why they study physics in the first place. But it's seldom deep enough to challenge fundamentally human concepts like justice. (Which science has proven does no in itself exist.)
+AFastidiousCuber
Your typical working physicist doesn't worry much (or at all) about philosophy while he is working. It just isn't relevant. He or she might have thought about it while an undergrad, or he might think about it in his off hours, but when he goes to work in the morning he puts it aside. It's not that he's too stupid to are, it's that he is smart enough not to waste time and effort pondering questions that can't be answered.
+AFastidiousCuber I think the thought of your imaginary scientist is not very thought through. :) If we get to the conclusion that free will doesn't exist - who cares? 1.) You _think_ you have free will. Even tough this might not be true, the illusion of it will certainly bring you further in life. 2.) If you're worrying about the predictability - I recommend watching the video "Free Will" by Wireless Philosophy. It demonstrates that a state of a closed system can only be predicted as long as it, well, stays closed! As soon as you somehow interfere with the system (maybe based on your prediction) your prediction might not be true anymore. Even tough you might not have free will, if you can build a computer that predicts that you die tomorrow, you can just act in a different way that the computer predicted! (You know what I mean?)
And about the "no purpose" thing... Imo "purpose" is quite a stupid concept, it was invented by religious people to whitewash the term "order from my god". Isn't it amazing that you may do whatever you want to do, without having to worry if you follow a purpose? You're still able to stimuly your happyness-receptors, even without purpose! :)
Not sure what you meant with illusion. ;)
AFastidiousCuber whether or not you believe reality exists the way we perceive it or not, our brains aren't changing anytime soon. So we're still going to experience reality the same way whether we like it or not, that includes getting pleasure from watching tv
Wow, Spacetime videos are getting better and better! Keep up the good work!
Can't stop watching your videos guys! So fascinating and well explained👍
Laughing hysterically at the "Pink Floyd" answer.
point it out plz
At the very end of the video
Well, the twins paradox is really well-known and resolves with noticing, that the travelling object must be accelerated to return to start point. But if we assume that our universe has a finite size and proper curvature to be closed on itself then there is a possibility to trip around the whole universe at _constant_ speed and to return to the same point, having both "traveling" and "stationary" observers "moving" relative to each other. How is the paradox resolved for such setup?
Lets say both twins are skyping each other, how fast would the skype session appear? If one travels at the speed of light away, then the skype session would be frozen at the non-traveling because the other twin is traveling away just as much as the light is moving back. However, the traveling twin would also have a frozen skype session because to him it appears as if the stationary twin is actually moving away (there is no prefered reference frame). The other twin will seem to be eternally young, but thats because the skype session is frozen. If they stop moving after being 1 light-years away, then the skype session will resume but show the data of 1-year in lag. If they move twards each other then the skype session will speed up and the lag will reduce until it reaches 0 lag when they are both in the same place.
This has to be one of THE BEST science / physics vids I have seen in the topic of what time ACTUALLY is!! Really appreciate this type of explanation, detail, and clarity ---/ indebted to you guys ...... Ps go physics!! :))
Superb. Your art of teaching is so commendable.
If I'm understanding this correctly, it means that causality is, ontologically, the only fundamental structure underlying the phenomena of time, mass and matter, correct? If so, then my question is this - what implications might this have, if any, for our speculations about the origin of the universe? Does the fact that reality at the most fundamental level revolves around causal relations change our confidence in the "something can come from nothing because time doesn't exist" hypothesis which often comes hand in hand with inflationary theory because time was never the reason for the any of this in the first place?
Incredible episode, truly. Tremendous thanks to everyone involved.
This told me I’m stupid in every language out there
Watching PBS Spacetime Videos reminds me of a very good and true positive review on a learning video looking at electromagnetism and electricity/electronics which said "I like this video because it makes things simple to understand, nowadays we seem to make the mistake of wording things in a complex manner because that makes the information appear more accurate or true" this is not the case however. And PBS makes a very good attempt of not packaging truth or information in a way to make it appear complex.
Absolutely THE BEST Science channel anywhere. Nothing is dumbed down, and still explained to non scientists. Brilliant. Thanks so much.
Wait, did you guys say that interactions between quarks and other subatomic particles happen at *less than* Planck Time? I thought there was nothing less than Planck Time?
+bbbl67 Not true. The Planck time is just the amount of time it takes for light to cross a Planck length. It's not a "minimum time period" in the sense that you might be thinking.
+PBS Space Time Aren't there theories that suggest that the Planck Length and Time are the minimum possible measurement units? Discrete spacetime theories?
+PBS Space Time So is time infinitely "small"?
+bbbl67 How I understand the Planck time, is that it is the shortest period at which we can actually observe an interaction, since no photons can propagate that quickly. Please, somebody correct me if I'm wrong.
+saharahgaiht directly measureably, minimum time units aren't infinitesimal. The fastest any event that can be mesured is a Planck time unit, the fastest thing possible moving the shortest mesureable distance. However, two events could happen within the same Planck time to the same Planck length, with one still happening before the other causally, and effectivly.
This is all assuming I understood this video, and I'm not sure I do yet.
do all world lines converge at the big bang?
Yes, because time and space originated from the Big Bang. Just remember that the Big Bang wasn't a single point or single event.
+When Will You Learn? Damn then what was it? I don't understand how can the microwave background radiation be so uniform if 3 dimensional space appeared everywhere at once, that's the hole point of inflation isn't it? Saying everything was closely together including space
+Vlad Tchompalov Probably, with a few small unknowns and definition quibbles. If they don't things become rather weird for our universe.
+Daniel Skiba The whole point of inflation is that space _didn't_ appear everywhere at once; space is expanding into itself. On scales like within a solar system or a galaxy, it's not quite as immediately obvious. On the scales involving the distances between galaxies, we see some crazy stuff happening, like galaxies speeding away from each other faster than the speed of light, even though that shouldn't be possible. The theoretical explanation that resolves this is that the space itself is expanding, which isn't constricted by something so petty as the speed of light.
+Chris V ...how is that related, you see if the universe is infinite it would never be in a finite size, if it can't be in a finite size how can the microwave background radiation be so uniform
I didn't grasp really any of this, but I appreciate how interesting this is, and appreciate your bringing it to us.
Those graphs just clicked something my brain and gave a much better understanding of time dilation and of the lorentz transformation, thanks for that!
very informational
+Alan Aji You finished it fast.
+David K lol
Very informal
Can every particle at least be sure of the order of its own interactions? If so, isn't a universal time frame available by compiling and comparing the different orders of interactions?
NO! (NO condescension here...)
Both Special Relativity AND General Relativity demonstrate that observers in different reference frames WILL witness a different order of events in another time frame moving relative to them than an observer IN the observed frame will! (Sorry that's such a clumsy sentence, this stuff is HARD to talk about!) So: 'particle A" will witness a particular sequence of events in it's own reference frame, but 'particle B' in a reference frame in motion relative (there's that word!) to 'particle A's' reference frame will NOT see the same sequence of events!
IMHO, that's the crux of the strangeness of both Theories of Relativity. I know, it's WEIRD!!!!!!
I love how this stuff bends your mind into a pretzel!
Great series. It touches on some of the ramifications of general relativity that are often overlooked, but seem kinda important now that you mention them!
Why does velocity have no absolute reference while acceleration does? What makes non-accelerating reference frames special? What are they not accelerating relative to?
+CvBrony Basically it's what is required to 'flip' the frames. With two moving frames this is quite simple, the rest of the entire universe can be seen to be moving. Space itself remains unchanged and identical for both objects.
For acceleration however a 'pseudo force' is needed. A gravitational field that fills the entire universe. (In this case the 'still' object is just falling in gravity while everything else in the universe is accelerating against it.) This requires space to be curved across the universe, both objects disagree as to what space(time) looks like and so disagree as to how much time has passed.
+CvBrony If you have no other objects to observe, you can't tell what your velocity is, because there is nothing to relate to.
Yet acceleration is still an observable (or rather experienceable) phenomenon, which you can experience without relation to other objects, for example while sitting in a car with your eyes closed. Your interaction with the back of the seat will tell you the car is accelerating, even if you can't see anything outside of the car.
+CvBrony _"Why does velocity have no absolute reference while acceleration does?"_
Acceleration does not have an absolute reference frame. It transforms in a similar way to how velocity, distance, and time transform.
_"What makes non-accelerating reference frames special?"_
The laws of physics are the same in all inertial reference frames. In accelerating frames you need to add fictional forces to get things to work. For instance, in a rotating frame, such as on a merry-go-round, you need to add centrifugal forces.
_"What are they not accelerating relative to?"_
They are not accelerating with respect to anything.
+CvBrony Acceleration is, in its essence, the increase of kinetic energy within a closed system. It doesn't need a point of reference.
Think of it like this: you're in a car moving at a constant speed and you throw a ball. The momentum of the ball will be [throw velocity + car's velocity] and so the difference in velocity between you and the ball is just the velocity put into the throw.
Now if you throw the same ball inside an accelerating car, while the ball is in the air, your velocity will have increased, and so the gap in between your velocity and the ball's gets smaller every second.
+Алексей Салихов But your car analogy only works because the force is only applied to the car, which then applies it to you, and you can feel this as the backseat squishes part of your body.. If every single atom in your body was accelerated at the same time via a uniform force (for example gravity), would you still be able to tell that you're accelerating? If you were in free fall in a dark chamber, how would you experimentally determine that you're accelerating towards the earth vs. just being in zero gravity? From what I have read, the two scenarios feel absolutely identical to humans.
Wouldn't quantum uncertainty allow for space-like paths on Planck scales?
+Brian Bouchard Yes, absolutely, and so the reality is much less clean than portrayed here.
+Brian Bouchard Giggity.
+Brian Bouchard So...space itself can transport information? Or bend and tangle itself to allow the flow of information between distant parts of...space...I have no idea.
I prefer to see it as interaction creates reality
quantum uncertainty allows everything in time and space but not in energees
Great Videos!...Finally asked and answered some basic questions I had in a way I could grasp it. Wow! I think I can finally begin to actually say I understand some of the concepts instead of just knowing them.
Once again, he actually answers those questions that I always have at the end of such a presentation that no one else does.
Your resolution for the twin paradox might have a problem in a Universe with a parallels-must-meet Geometry (a finite Universe), since the astronaut can travel along a geodesic and still get to the same spacial location again (like starting in Greenwich, and following the meridian until you get back to Greenwich again). There should be no acceleration since space it self is curved equally from both perspectives (expect for the 'paradoxic' Lorentz Transformations of course)
Also a question that bothered me as a mathematician: you've shown a coordinate transformation from one to another reference frame... Intuitively it feels like this might be done with a projection matrix that maps the Standard Basis of the Euclidean space of one observer to his perception of the other observer's Standard Basis (sorry if I did not get the math-terminologies right, I did my algebra at a German university :P).
I wonder whether the Lorentz Transformations are really Endomorphisms (should be Isomorphisms as well in that case).
+Jonas Kr. There's actually a solution for that, it's a little bit of a sod on the maths front bu basically the geometry of the universe will cause one twin to age and indeed have an effect whenever two objects move apart at a fixed speed in any direction. I had to spend a week on Physics Stack Exchange before everything clicked. Never again.
+Gareth Dean it would be very kind of you, if you could send me a link to the page that made it click
Jonas Kr.
Darned if I can find the thread now of course... but they sent me this, which put everything into place. (My math skills are rusty enough to give tetanus and this was relatively math and jargon free.) www.math.uic.edu/undergraduate/mathclub/talks/Weeks_AMM2001.pdf
+Gareth Dean jargon free is good, but I for my part can access physics much better from the maths point of view (for what did I do maths at university if not for that :P). But I'll give it a try :D
+Gareth Dean What I got from this was simply that symmetry is broken in finite universes and that feels wrong, totally, utterly wrong.
For whom the bell tolls.... 1:58
\m/
I love watching these videos and stretching my brain to barely grasp their concepts. Just wish there was someone at work or even within 50 miles around me I could talk with about these subjects.
This is my favorite channel by far on CZcams. Hands down.
The exact speed of light is actually 299,792,458 m/s!
Thanks, random citizen!
Didn't he say kilometres
+RAMMSTONE Either 300,000 km/s or 300,000,000 m/s, both mean the same thing.
Harys Page km/s is not the same as m/s....
*facepalm*
If there is no clock that can measure absolute time, how do we know the age of the universe?
+Gabriel Oshiro Background microwave radiation is used for those calculations.
+Gabriel Oshiro I think we extrapolated the age of the universe from how much it has expanded. That is, how long it took for galaxies and stuff to travel that much distance. Please, somebody correct me if I'm wrong.
+Elijah Potter I don't get it... how do you measure time from the background radiation?
iseslc But that's the thing... If my clock is not the same as other galaxies, could it be that we think that it took 6 billion years to get here but another galaxy will feel like just 5 billions have passed?
+Gabriel Oshiro I believe PBS Spacetime has a video on it if you are interested.
this animations were amazing and its very easy to learn ! Great video :D
This video is brilliant. This whole channel is brilliant.
I wonder where the notion of time being dimension came from? all observations showing quite clearly time is entropy and it is always now - nothing less and nothing more. I have a simple question - if time is a dimension with past and future as a directions - where is the bit that connects the present with the past and future? ;-)
+tzahry It comes from the light clock idea.
t' = t (1-(v/c)^2)^.5 multiply everything by c^2
c t' = t (c^2 - v^2)^.5 square both sides
c^2 (t')^2 = c^2 t^2 - (v t)^2 v t = d = x^2 + y^2 + z^2
(c t)^2 = (c t')^2 + x^2 + y^2 + z^2
On the left is the distance every observer (sitting in one inertial frame) goes through which is c t
On the right is the distance an object moving through x, y, and z goes through. They go through more space so they are perceived to go through less time (t' is their time).
The equation looks like a 4D Pythagorean's Theorem like c^2= a^2 + b^2 is for two dimensions.
Does this mean time is no different than space dimensions? No, absolutely not. I personally don't think of time as an actual fourth dimension (I've studied it for many years and have my own interpretation). Nevertheless, there is a mathematically 4D relationship.
Often you'll see the equation as:
s^2 = c^2 t^2 - x^2 - y^2 - z^2 because s is called the "space-time" interval and it's the useful thing in GR and SR but the other form is more intuitive.
Thanks for the answer :-). the question "where are the bits that connects the present with the past and future" is quite interesting thought experiment ;-) i know about the light clock and it's excellent brain crotch but the light clock is just a metaphor so extrapolating anything further from that is road runner physics :D (it's not too far from reality but it makes complete sense only in cartoon). The problem with 4D space is that it makes sense if you look at it only from very specific angle and then it quickly falls apart in you start poking into details. Further more there is no evidence of any 4th dimension I'm aware off - quite the contrary so far (using 4D to explain things is bit like solving mysteries by aliens - anything can be explained with super advanced aliens ;-) >>> The equations are well known however they make prediction that entropy of whole universe is reversible from certain frame of reference (= time travel) so there is quite big flaw in it (no particles traveling back in time were ever detected and if time would be 4th dimension the universe would be full of these). Another fun extension of the thought experiment if you'll go really deep into it is trying to prove direct physical evidence of past or future ( = that isn't exclusively 100% extrapolated from "now"). ;-)
tzahry I already said that I don’t think time is the “fourth dimension” and it is distinctly different than the spatial dimensions and no one can deny this. Nevertheless, there are 4D relationships. That relationship is in equations that form a Pythagorean’s Theorem in 4D.
The photon light clock typically shown is just the simplest example available. ALL fundamental forces move at c (strong force, EM, gravity all do and the weak force is a composite) and every particle not bound by some field moves at c. The light clock also works at all angles so it is really a fundamental principle.
I interpret relativity differently than others however. I view relativity by thinking about the Doppler Shift:
Classically it is: fmo = f (1-v/c) and fms = f / (1 + v/c) where v positive is receding
Almost all the evidence for relativity amounts to proving that fmo = fms and wlmo = wlms
Also QM states that E = h f and p = h k where h is just a constant (so for example if f is symmetric then so is E) so reality has a symmetry of observables between reference frames and these observables only depend on the relative velocity.
The time Lorentz Transform is
t’ = (t - v x/c^2)/gamma where gamma = (1-(v/c)^2)^.5
Clocks synchronize with light in the transform (the fastest thing available and so it’s the only thing that can synchronize the clocks; fast and slow clock transport have the same results) so c t = x or t = x/c thus:
t’/t = (1-v/c)/gamma
The relativistic Doppler Shift is:
f’/f = (1-v/c)/gamma
Thus
t’/t = f’/f
These equations can be expanded for all angles and situations and the time dilation of gravity also has an exactly proportional red and blue shift.
We do NOT see time dilation alone in any system but rather we see the entire Lorentz Transform. Most people get this horribly wrong. Time will appear to move faster when an object approaches because the Doppler Shift blue shifts. EVERY manifestation of time is set to the fundamental forces so if they shift so does time. A cycle of light at a certain frequency equals a certain amount of time. The more cycles observed the more time observed. The ticking of the fundamental forces IS time. The symmetry of observables (f, k, wl, E, p) between frames is necessary experimentally and one of the most well proven concepts in physics.
Back to the classical Doppler Shift. Let’s see what happens if we apply time dilation to ONE and only one reference frame. The moving source would then emit at a lower frequency by gamma and the moving observer would intercept a frequency higher by 1/gamma. Time is ONLY running slower in the moving frame. Thus we have:
fmo = f (1-v/c) / gamma and fms = f gamma / (1 + v/c)
fmo = fms = (1-v/c)^.5/(1+v/c)^.5 = (1-v/c)/gamma (do the math and this is an astonishing result)
The reference frames are asymmetric but there is a symmetry of observables between frames and this result matches SR. _All things we can experiment on are symmetric._ Also
kmo = f (1-v/c)/gamma and kms = f gamma / (1 + v/c)
kmo = kms = (1-v/c)^.5/(1+v/c)^.5
By using the Lorentz x Transform (x’ = (x-v t)/gamma) synchronizing with light c t = x and the relativistic k Doppler Equation we have:
x’/x = k’/k to me this is why time and space are treated the same in relativity. Just like frequency of the fundamental forces maps out the progress of time (creates our clocks) the wavelength (or wavenumber) maps out distance and creates all our rulers.
Again we can have length contraction in only one frame but the observables between frames are again symmetric. ALL observers have rulers and clocks set to their own reference frames thus they will always see the speed of light as c because for light:
f’/k’ = f/k = x’/t’ = xmo/tmo = xms/tms = x/t = c
I personally don’t think all reference frames are absolutely symmetric but there is a symmetry between reference frames allowing anyone to prefer their own frame. One’s clocks and rulers are always set to their own frame so they can’t measure differences. The Twins Paradox for example is true because no one can ever think that two frames are special. The metrics in General Relativity reflect the symmetry _between_ reference frames and Minkowski mathematics can be derived using this interpretation.
If relativity is viewed in this way then the insanity of backwards time travel if faster than light travel was possible wouldn’t occur. This idea was well explained by physicist John Bell. If anything this and other ideas show that we don’t know what’s “actually” happening in another reference frame we just know what we can observe from our own frame and we always see the laws of physics as the same in our local frame.
Particles are excitations of fields and if there is a finite maximum speed (which is well proven) then it’s not amazing that those excitations distort (especially since all changes in fields propagate at c and everything is wavelike). There is no such thing as a rigid object. In fact the way they distort works out perfectly and matches SR and GR.
"Time" only applies so long as we're talking about an assemblage of massless lightspeed interactions at the Planck scale, a "thing." Sequences of events are important to us but they are only important in the present moment insofar as they set particles (processes, quantum interactions) in certain directions with certain energy, which defines if and how they interact. That goes on to produce more interactions, and still more, but now I've reduced it down to a billiard ball metaphor and that breaks down, too! Turns out pretty much every logical principle we hold sacred breaks down at a certain point.
Say you travel into the future - theoretically possible. Okay, but are you the same "you" who did the traveling? Did the traveling change you, and can you in any way inform "past you" of what it's like at the other "time"? Again, paradoxes of logic emerging from our limited (classical) understanding of the universe. I'm probably inserting a dozen more I'm not even aware of! Someone will come along and point them out, I'm sure.
I love CZcams comments. :) Best waste of time ever.
Possibly the emergence theory?
Damn...I love Space Time, but for crying out loud, the background music in this episode makes it hard for me to concentrate on what he is saying!
Maybe my favorite video of the series so far. It provides insight into both relativity and the quantum realm.
The graph at the beginning really helped me understand the space-time duality and it's relation to light. It hlped me piece together the expansion of space and it's relation to objects with mass.
Is the speed of light constant in a gravity-well? If we're in orbit around a black hole, wouldn't we be in a region of very curved space, and if the speed of light was not invariant, how could we properly test the invariance of the speed of light on Earth?
+electrocat1 I believe the Michelson Morley experiment may clear up your last question. also the Michelson interferonmeter
Abzun777 It doesn't. My question is whether or not a Michelson interferometer would even give a reliable result in a gravitational field.
+electrocat1 Yes it is. The fact that space is curved is what causes time in a gravity well to pass slower than outside of it.
+Gareth Dean but what about to an inertial observer in the gravity-well? Would the deviation in the time component and the space component of the geodesic be substantial enough to cause a difference, or is it accounted for somehow? Surely it must be, because then the equivalence between an orbiting reference frame and one in intergalactic space would be lost, right?
electrocat1
You are correct, it is accounted for and one of the reasons is, as you mention, the equivalence of an orbiting and intergalactic frame. It can actually get quite odd when the curvature is severe, at an event horizon even massive particles will be traveling at c.
If light has a speed, they have a distance per time. But if photons experience no time and still experience a change of distance, does that mean they experience infinite speed?
*it has
+Holobrine Observers perceive light traveling through their own time, but when Matt says photons experience no time he means from their frame of reference; photons experience no time because to them, time is simply frozen. Checkout the Spacetime video with the photon clock, particularly when the clock starts moving at the speed of light, it's great for visualizing this.
+Holobrine Not quite, the speed of light is the same even for them. However they experience infinitely short journeys. As you go faster space 'pancakes' in the direction of your motion so photons see the universe as infinitely thin, with all points they visit being the same place. In a very real sense they don't experience anything, their birth is their death.
+Holobrine Youre forgetting that since they travel at the speed of light, the distance shrinks for them. So while they travel at the speed of light (and not any faster), they don't have to travel very far at all. They essentially experience no ticks of the clock until they interact with something
+Holobrine No, it is never possible to observe an object moving at an infinite speed. Instead, light speed objects experience zero space because from their perspective all the differences in surface features, like the curvature of the Earth, are completely non-existent. As any object approaches the speed of light lengths contract, so for any object moving at the speed of light all other objects appear completely flat.
If I remember correctly all of this relates to the concept of hologram theory as all of the three dimensional information about the universe existing as a timeless two-dimensional representation specifically because everything is massless particles in which information is stored in arrangements that conform to clear cause-and-effect relationships.
It's actually rather interesting when you think about it.
Matt O'Dowd! U always present these topics very lucidly, so even guys like me with basic physics knowledge can grasp these topics. Now I get a hang on how Gen RT & Spl RT are to be applied; how causal perspective of matter and so time & so to resolve the Twin Paradox! Thanks.
I wish PBS did more video series like these, makes learning way more fun and interesting.
The explanation of the twin paradox is incorrect. You don't need GR, nor is special relativity confined to dealing with situations where no acceleration takes place. All you need is that accelerations are small enough, or gravitational fields weak enough. For example, a twin can use a ship that accelerates at 1g, and wait a few years for his ship to turn around. The time dilation effect due to the acceleration of 1g is completely negligible then in comparison with the dilation due to motion close to the speed of light.
The correct explanation is that in spacetime a straight line is always the *longest* path between two timelike separated events. While the twin who remained on Earth spent the entire time in a single inertial reference frame, the twin who went on a trip spent half the time in one, half in another moving in the opposite direction. This crooked path is actually shorter because of the peculiar geometry of special relativity.
To make the description a bit more concrete: the twin who remained on Earth thinks that due to time dilation, *each leg* of the trip only took 5 years in space, even though on Earth 25 years passed. The twin on the spaceship thinks that *each leg* took 1 year for his brother on Earth, even though the spaceship's clock measured 5 years. It may surprise you to learn that, when speaking of each leg individually, they're both correct! However, only the twin who remained on Earth stayed in a single reference frame, so only he gets to add his numbers together and get 50 years on Earth, 10 in space.
The twin who went to space was not in a single reference frame, so it makes no sense to add his numbers together. Each was measured in a completely disparate reference frame! It's apples and oranges, a bit like comparing temperatures in Celsius and Fahrenheit directly. So even though the acceleration of the spacefaring twin is important for resolving the paradox, the general relativistic dilation of time due to acceleration is a red herring.
+Vacuum Diagrams I heard the words 'straight line' and 'speed of light' I have to laugh at that, because one doesn't exist, and the other is a variable speed, and not a constant speed like you have assumed. 'The speed of light' nope, just wrong. Try again.
+Vacuum Diagrams If I was to say such a thing as 'The speed of a car' you'd laugh.
+Tripcore You might want to watch a few more videos on this channel. I suggest the one entitled "The speed of light is not about light" or something to that effect.
Vacuum Diagrams Why would I watch something that's named 'The speed of light is not about light'? That's like asking me to watch something called 'the speed of a car is not about a car'.
The matters of time always confused me.
Let's say there is a universe in which there are no particles that have mass. Maybe at the heat-death of the universe. All what's left might be some photons travelling through space. Then you can't even build a clock, and according to this video, if I understand it correctly, there is no passage of time anymore. But aren't there still changes in the distribution of the photons in space? Can't two photons meet and interfere with each other? If there is any *change* within space (or even expansion of the space itself), doesn't that imply the existence of time?
Does the fact that we can measure time only in one way, for material objects, imply that time really stops when we can't measure it any longer? Or does it simply mean we are left with no tools to measure it? Could it be, that the time we measure is simply an emergent emanation of some deeper time dimension, or that there could even be a different time dimension in which our time-space is immersed and changes its states?
krzyszwojciech time is just a way of our brains perceiving the change of reality
If you define time as a perception, you make it kinda solipsistic, subjective-dependent. Without brain then, there would be no time by your definition. Isn't it better to just definite it by change itself?
And we do perceive expansion of space anyway, yet no physical time seems to be associated with it from the description of the video, IIRC. Unless the space itself have a mass associated with it, as I've heard before.
Still, it seems to me that this model of time is lacking something.
Maybe the correct way to look at time would be to look at some bits of space and what their changing content is, rather than associating it with a particle. This way, in one moment of time a bit of space would contain a photon (or information associated with a photon), and in another moment it wouldn't any more. It would seem more sensible, but maybe less practical, since we can't measure anything at that scale to even confirm that the space is made out of quantised objects.
In my understanding, yes, change implies time; the two are necessary to describe each other and therefore synonymous. We still don't know exactly what will happen at the heat-death of the universe, but it seems to me that in a system with maximum entropy and zero density, no interactions between particles would be possible, and thus no time could pass. This could only occur if every fundamental particle were moving at the speed of light in a solitary reference frame. If there exists so much as a single proton or electron, time is occurring.
The Big Rip describes one such scenario, in which space expands so rapidly that even subatomic particles are torn apart into their components. But if that does not happen, then the universe will be filled with a uniform soup of neutrons at the lowest possible energy state, emitting no photons. Those neutrons would experience time, but there would be nothing to observe whatsoever.
But, as I pointed out earlier, looking at time merely through the view of particles with mass disregards other types of changes. Like expansion of space. Or change in distribution of photons (two photons could meet and maybe get entangled and it would be impossible to talk about such an event without some kind time concept established). Or the fact that the photons red shifts in that growing space.
If we assume that time is only occurring where mass exists, wouldn't it also be true that most of the universe is timeless already?
Unless space has a mass associated with it after all - and in principle there will always be some time preserved this way.
It may be that the expansion of space has no time component, but is only relevant as it affects particles of matter traveling through it. After all, we've seen that time is defined as the causal interactions of particles, and such interactions must occur within some sort of "container" or field, as within a proton, or as ripples in the HIggs field.
Where there is no mass, there cannot be any time, by definition. At least, this is what I'm taking away from the lecture. Space-time, after all, is a medium, not a tangible "thing" that one can interact with.
I like this channel so much I feel like taking notes, even though I don't need to.
Best Episode it all came together for me here with concepts from other episodes
How can I translate this into English?
+imnotbatman
Go get a degree in physics.
+imnotbatman If you cant understand his accent, dont bother trying to understand the content, its obviously over your head. Its also over your head to turn on captions.
+tubester4567 The captions on these videos are the CZcams auto-generated ones, and they pretty much suck. I'd love it if PBS Space Time would actually do the work and make the captions accurate. But that's a lot of tedious work, and assuming you have to pay somebody to do it, a fair amount of money.
No wait, I lied. Somebody did write accurate closed-captions for most of these videos. But not this one, or the previous photon clock challenge video. I dunno why...
Weak-minded idiot.
"What is a thing? No mystery there"
As a Buddhist I find this personally offensive.
Buddhists get offended?
@@Cabutronize yeah, I thought they are supposed to be too detached to care
One of the most well explained video! keep it up. :)
I sit on my computer for hours just watching these types of videos. really great job at explaining all this
The photon clock with a photon bouncing back and forth between two mirrors counting as one tick of a clock, just another arbitrary unit of measurement to measure "time". How come just the movement of one photon one cycle isn't "time"? How come just the movement of a photon at all isn't "time"?
+Charles Brightman I think because there is no set distance the photon would be defined as traveling. the Mirrors could be any arbitrary distance apart.
+Charles Brightman well thats not time as we know it. what we call "time" and measure is really just the change of the these "photon clocks".
if for example the universe was empty there wouldnt be time (as we know it), there might be a continuation of *something* but it wouldn't be what we call time.
+Charles Brightman He's not saying no time passes between ticks. I think you're misunderstanding the video. The photon clock is a measuring tool, like a ruler that measures space. However the clock gives a good demonstration of how time fluctuates as your speed changes, since you can visualize the change in photon path length.
+Jerman Ramirez I don't know. Can something even "exist" without time?
+TenebraePatruus Agreed, so the unit of measurement for that time is arbitrary also.
im getting way to dumb to understand this videos
*too dumb... haha
Loved this episode series, so wel put
Simply the best matter and time explanation I’ve ever heard. 🎉
Taking about time, if there is no absolute time then how is age of universe 13.8 billion years...
Because we can construct a human time scale, a cut or boundary by which we understand materiality/existence/materializations through a measurement we call time, but it doesn't mean that time itself is as we claim it is or even that it exists. Time is a form of human measurement but the cosmos doesn't center or care for our narratives. WE are trying to fit them into our stories and not the other way around.
Its the amount of evolvement(if thats a word) of the universe relative to the big bang
@@Critterpig evolution
my brain just melted... i love it! Keep up the mind melting work guys!
Wow, this series is getting better and better!
Great Video as always!
My understanding is that the Twin Paradox is fully explained by SR alone. When the traveling twin changes direction, she changes her frame of reference, and that alone is what resolves the paradox. For example, consider the traveling twin instantly teleporting from Earth to a passing ship, later teleporting to a returning ship, and finally teleporting back to Earth. Or just exchanging timestamp messages among passing ships, the time dilation still resolves, and the "traveler" ages slower. Acceleration isn't required.
True
good job making the clock you held part of the graph... lovely video effect.. the science you are doing is better though but that says alot..
The greatest representation of a photon clock on a space time graph that I have ever seen in my life. Explains it perfectly. Hats off
This is the best physics channel on the internet right now.