Pls don't break the universe, that's where I keep all my things.

@BattleBunny1979

3 жыл бұрын

save often and in different savegame slots

@MCsCreations

3 жыл бұрын

"Because I am one of the stupids that live in it."

@tpog1

3 жыл бұрын

You really should get yourself an ender chest in the Nether.

@alansmithee419

3 жыл бұрын

Can I just break a lil' bit of it?

@-cookiezila-461

3 жыл бұрын

I stuff my grandma in there! Don't you dare break the universe

So apparently Einstein was a real person? I always thought he was a theoretical physicist.

@DHGameStudios

3 жыл бұрын

"they asked me how well I understood theoretical physics. I said I had a theoretical degree in physics. They said welcome aboard." -Fantastic

@MaxArceus

3 жыл бұрын

okay, you win

@riverground

3 жыл бұрын

It depends on your frame of reference.

@plexiglasscorn

3 жыл бұрын

@@riverground it is lorentz invariant

@maxmusterman3371

3 жыл бұрын

no, he is a stone. literally

7:38 Literally every episode: "Doesn't this violate (some fundamental part of physics)?" "No."

@drx1xym154

3 жыл бұрын

Could depend on the attorneys - or The Judge!

@NoActuallyGo-KCUF-Yourself

3 жыл бұрын

Physics is so big at this point that it is almost impossible to break: it just gets little dents or cracks from spacetime to spacetime.

@thomasreedy4751

2 жыл бұрын

Physics can’t be broken, it just is. Our theories and understanding on how the universe works could be.

@zeroneutral

2 жыл бұрын

@@luddite31 no.

I want one of the episodes to end with an extremely long sentence that keeps sounding like he's about to say "space time" but then he adds another phrase and another phrase, and it goes on for like a solid minute, and he never acknowledges that he's doing anything weird

@drx1xym154

3 жыл бұрын

That could break the universe!

@new-knowledge8040

3 жыл бұрын

Yes and space does not contract. If you have 60 spaceships going 60 different speeds, you don't end up with space being of 60 different sizes simultaneously.

@new-knowledge8040

3 жыл бұрын

By the way, It is an easy breezy task to just discover special relativity all by yourself.

@kevinmathewson4272

3 жыл бұрын

@@new-knowledge8040 space doesn't need to "contract" or be 60 different sizes, dude. Think about it this way: are the passengers on a train simultaneously moving and not moving? The passengers look stationary to someone _on_ the train, but someone on the platform would say the passengers are moving. The passengers aren't simultaneously moving and not moving, because the question of their movement is _relative._ Space and time are relative in the same sense.

@new-knowledge8040

3 жыл бұрын

@@kevinmathewson4272 Okay, so George says, "Hey, its not my spaceship that moving, it's your spaceship that's moving.". And then Fred says, "No, it's not my spaceship that's moving, it's your spaceship that's moving.". The George says, " Hey, its not my clock that's ticking, it's your clock that is ticking.". And then Fred says, "No, it's not my clock that's ticking, its your clock that's ticking.".

“Safe from colliding with their own arses”, did not expect that, but perfectly delivered.

@dorquemadagaming3938

3 жыл бұрын

ASSSETS, damn it! ass-sets! Due to uncertainty principle and many-worlds there will be multiple of them to collide with!

@PandemoniumMeltDown

3 жыл бұрын

Gay boi left the chat, disappointed.

@PandemoniumMeltDown

3 жыл бұрын

@@karlwest437 I wonder if, when one smells one's own farts... naaaa

@charlesblanton1008

3 жыл бұрын

I've had days at work when I felt like I could, in fact, collide with my own arse. 😂

@PandemoniumMeltDown

2 жыл бұрын

@full stop What... what a swell idea!

Man: "Hey, I ordered a sandwich for everyone but we didn't get everything. How are we going to divide this up?" PBS: "Again, this is best determined using a space-time diagram."

@astrophysicslair1445

3 жыл бұрын

Honestly minkowski diagram for the win. In my SR class we used it to solve problems by verifying the answer given by the math with the diagram (provided you could make straight lines lol)

@sadrevolution

3 жыл бұрын

Ha! I almost spit out my tea!

@sasshole8121

3 жыл бұрын

If you don't have a space-time diagram, a Penrose diagram will do.

@thadaungst8627

3 жыл бұрын

@R F ??? Please explain ???

@oberstmerkel7919

3 жыл бұрын

As a friend of mine once put it: I couldn't divide those five sandwiches between us three so I ate them all by myself.

This guy is like the most engaging science presenter I’ve ever encountered. He really makes this stuff clear for someone like me who still enjoys physics but hasn’t taken any physics courses in over a decade.

@andrewbeil1799

2 жыл бұрын

Then.... you really gotta look into Neil Degrasse Tyson

@boyang3179

2 жыл бұрын

Yeah, I have a bachelor's degree in physics. I would still argue, that a lot of his explanations makes more sense if you have taken at least a undergrad level class in special relativity.

@mystomachhurt9312

2 жыл бұрын

@@andrewbeil1799 nah neil sucks

@WardenOfTerra

2 жыл бұрын

@@andrewbeil1799 - Neil is shite. He's not engaging one bit.

@Chance57

2 жыл бұрын

@@WardenOfTerra comes off as too self possessed to be an effective communicator.

I have to emphasize the good communication between Matt and the 3D artist. I have no idea how they get this stuff done.

I think the explanation at 5:35 is misleading. She does not miss those New Years. Her "now" line sweeps through them instantaneously with the infinite acceleration shown or very quickly with real accelerations depending on her distance. Indeed she will pass through the wavefronts from broadcasts on each of those New Year's celebrations on her way home. That is definitely not equivalent to missing them.

@invalidBlacky

3 жыл бұрын

Thank you! That part bothered me extremely! The problem is not "missing time" but the acceleration to get to the speeds of traveling..!

@guystewart1930

3 жыл бұрын

Exactly, This needs to be pinned at the top.

@fuseteam

3 жыл бұрын

the point is that her dilation isn't really related to acceleration but due to being in two frames of reference

@dynapb

3 жыл бұрын

@@fuseteam Yes, but you cannot get to the other frame of reference without the infinite acceleration.

@fuseteam

3 жыл бұрын

@@dynapb doesn't matter if it's teleportation or wormholes or something else, it doesn't matter how go from one frame to another, the fact that you are traveling in two frames of reference means your time is dilated not that of the earth

The space-time diagram of the ladder was really cool. I never thought about it that way

@AsmodeusMictian

3 жыл бұрын

I'd seen it explained before, but the way they lay it out in this video is fascinating :)

@jamrep9633

3 жыл бұрын

I like non Euclidean BAHNS too.

@darthmase

3 жыл бұрын

The ladder's axes in this case can be constructed with Lorentz transformations, right?

@nielskorpel8860

3 жыл бұрын

@@darthmase yup

@sciencoking

3 жыл бұрын

@@darthmase That's the idea :)

Another episode of me pretending to know what’s going on :D

@sanketjadhavar

3 жыл бұрын

He is saying if we would really want to f**k ourselves then we have to run around a tree without pants with speeds close to a significant fraction of lights velocity! Or am I missing something?

@ChaineYTXF

3 жыл бұрын

You don't need much math to understand this. It's actually oddly accessible. But you have to think long until you figure it out😁 If you ever wanted a difference between Math and Physics, well this this it..

@glypheye

3 жыл бұрын

@@sanketjadhavar wouldn’t work because your forward facing prong would be partway up a growing tree from your backward facing bunghole 🤨😜

@peterbanos703

3 жыл бұрын

@@sanketjadhavar To the tree it will look like you are really f** king yourself, but to you it will look like the tree is needle thin and you are just turning around very quickly. **said I, pretending to know what's going on**

@shilohauraable

3 жыл бұрын

@@sanketjadhavar 😂😂😂

Guys, whenever you mention an earlier episode, you could put the link of that episode in the description.

@TlalocTemporal

3 жыл бұрын

They put those like in the info cards. It's the little "i" in a circle that pops up occasionally, called "from PBS Space Time".

To Matt and the team. Thank you for your uploads. My mum died a few days ago and your videos are the only thing that helped me sleep. Especially during the time she was on life support. What's strange is people find solace in religion but ive found solace in physics.. It helps hearing an aussie voice too, her ashes will be launched from the most eastern point at Byron Bay on Friday for entropy run its course across the Pacific Ocean and beyond.

@atk05003

3 жыл бұрын

I think people often find comfort in knowing the universe is orderly. Both physics and religion can provide more or less orderly explanations of the structure of the universe.

@Jeffros

3 жыл бұрын

Im sorry for your loss, my condoleances. Can’t imagine what you are going through.

@Only1Shadow

3 жыл бұрын

Sorry about your mum... but to give you a different perspective to contemplate I'll tell you as a Christian I find science to be the study of how God made the universe... so your example is two observations of the same thing.

@joemarz2264

3 жыл бұрын

May God (Christ, the universe, or whatever concept you favor) bless you and your mom.

@megamanx466

3 жыл бұрын

@@joemarz2264 Thanks for being open-minded and considerate of other's views. 😄

"Long story short" may not have been intentional but was funny regardless

@Novastar.SaberCombat

2 жыл бұрын

With Matt's level of communication... hmm... I would assume that little 'Easter Eggs' have been hidden in *many* of the videos over due Time. But, I can't be for certain, as... I'm not very intelligent (well, not on theoretical physics of ST/GR, etc.).

@Natural_Science

2 жыл бұрын

Looool xD

@TheAnantaSesa

2 жыл бұрын

yeah, if you play the video at 2x speed then LENGTH CONTRACTION is why the video finishes faster.

Dude ... I speak Portuguese and understand almost nothing that you say , but still is amazing to tried to understand. That's how good teacher you are. God Bless!

@user-lb8qx8yl8k

2 жыл бұрын

Tudo bem!

@jonnnnniej

2 жыл бұрын

What a cool way to reach yourself! 👌

New title: “Can we break your brain?” Answer: Yes

My brain just wrapped around the inside of a closed skull and crashed into its own rear end.

@bobinthewest8559

3 жыл бұрын

My brain can't do that... Skull too thick.

@erebology

3 жыл бұрын

My brain is already there.

@WHYNKO

3 жыл бұрын

General theory of relativity says it can't happen 😁.. the front end of your brain will never get to meet the rear end for it will be in the past 😉👍

@erebology

3 жыл бұрын

@@WHYNKO Ted Cruz did it.

@nobodie9996

3 жыл бұрын

@@erebology because of course everyone comes to PBS Spacetime for political humor

"The size of the ladder in a Pac-Man barn", this is exactly the high level physics i show up for

@annepearn4545

3 жыл бұрын

Why is it a Pac Man Barn? I dont understand.

@YtseFrobozz

3 жыл бұрын

@@annepearn4545 In Pac-Man, when you exit the passage on the right side of the screen, you "wrap around" to the passage on the left side of the screen (and vice-versa), making it analogous to the closed universe. Sort of.

@horsetuna

3 жыл бұрын

@@YtseFrobozz ohhh. Wish I discovered that when I last played.

@TrainsandRockets

3 жыл бұрын

@@YtseFrobozz I would like to thank you...I understand the reference now.

@souparmsbarraza7206

3 жыл бұрын

I love how it makes perfect sense after four years of learning all this. These four year studying paid off big Time finally

I'm gonna go out on a limb and claim that Matt's resolution of the twin paradox in a closed universe is incorrect. Let me preface my explanation by stating that I love this show and I have a huge amount of respect for Matt. Moreover, I'm no flat Earther, creationist, nor am I a devotee of the electric universe. I'm a mathematician by trade who spent much time studying general and special rellativity. *Why is Matt's solution wrong?* First let me review the standard scenario. Suppose that Alice and Bob are both in inertial reference frames where, in particular, Bob's frame is moving at a constant velocity in the direction of Alice's positive x-axis. Because there is no preferred reference frame we can consider either twin to be the "at rest" twin. We can draw a spacetime diagram with Alice at rest. In that case two events on a horizontal line are simultaneous for Alice. For Bob simultaneous events lie on a slanted line. We can draw another equally valid spacetime diagram where Bob's considered to be the twin at rest. On that diagram events on a horizontal line are simultaneous according to Bob and Alice's line of simultaneous events is slanted. At this point it's worth noting that the common means of verifying that there is no preferred reference frame is to say that there is no experiment that can be performed by either Bob or Alice at any moment in time to distinguish one reference frame from another. That said, in a closed universe, once again, either twin can be considered as the "stay at home" twin. After all, what experiment could either Bob and or Alice perform to conclude that one of the two is truly at rest? Unlike the standard twin paradox, at no time during the journey does either twin require a booster rocket to make a course correction. This is where I can be wrong, but I don't believe that such an experiment can be performed at any moment in time during the journey to distinguish between the twins. This is the means that Einstein used to conclude and verify that there is no preferred reference frame. Moreover, we can draw a diagram where Alice is considered to be the twin at rest. On that diagram events on a circle are simultaneous for Alice and events on a helix are simultaneous for Bob. We can draw a spacetime diagram which is equally valid in my opinion, where a circle is the set of simultaneous events for Bob and a helix is the set of simultaneous events for Alice. So if Matt's resolution is incorrect then *What is the resolution?* Here comes the anticlimactic part. My claim is simply there is no paradox to resolve. The thing to understand is that in special relativity, it is assumed that spacetime is flat and is therefore described by the Minkowski metric. But the spacetime of a closed universe is not flat. The Minkowski metric doesn't apply. Consequently, the notions of time dilation and length contraction as they relate to the Minkowski metric do not apply either. Thus, if there is a paradox, it's not the one(s) that we are considering here. For a closed universe perhaps we should consider the so-called Robertson-Walker metric with positive curvature.

@jacobm5167

2 жыл бұрын

I just made the exact same point. Another point to make is that the Robertson-Walker metric describes a spacetime with intrinsic curvature. The cylindrical spacetime considered here only has extrinsic curvature. But even still, the Minkowski metric doesn't apply. I also saw somewhere online an article that addressed the same question (about the twin paradox in a closed universe) and produced the same answer seen here in this video!!

@beachcomber2008

2 жыл бұрын

Yes, as soon as a cylinder was proposed my brain red-flagged it (possibly ahead of my conscious state). Not that I'm a hero. No paradox.

@stephenkalatucka6213

Жыл бұрын

The universe is flat. If you go too far, you fall off the edge. If someone ran through a barn at close to C, would an observer even see him, or just a blur accompanied by a sonic boom and alot of cow-doo flying about

@fizzy4149

Жыл бұрын

@@stephenkalatucka6213 -- Can't argue with that!! Case closed.

@nordogned7298

Жыл бұрын

A closed universe doesn't actually have to be curved. A Riemannian manifold can be both closed and flat. Since Matt is applying special relativity we can then safely assume that the universe in question is flat. The flaw in your counterexample is that, as Matt points out, special relativity only prohibits a preferred frame locally. A global preferred frame is perfectly fine. There is indeed no way for Alice and Bob to distinguish the frames _at a given moment_. To figure out what the preferred global frame is, they have to do what they just did: Send one twin around the universe and then look at the age difference.

Boris’ Spacetime Hypothesis: The PBS Spacetime set is cursed. The longer you host for Spacetime, the faster you talk.

I sped up the video and it didn't loop back on itself guys, so I think we can call this one verified.

@gorgit

3 жыл бұрын

Thanks mate! Was about to try that!

@shoegum7362

3 жыл бұрын

Yeah well autoplay must've been turned off

@JeffQue

3 жыл бұрын

But how much acceleration have you tried? Maybe if we add more throughput it's velocity exceeds the necessary for KZread closed loop space

@someguy3766

3 жыл бұрын

@@JeffQue I tried firing my laptop out of a cannon at relativistic speeds to test this. Unfortunately I failed to collect any data as the laptop... did not survive the experiment...

@why_though

3 жыл бұрын

@@JeffQue press Ctrl+J type: "document.getElementsByTagName("video")[0].playbackRate = 16" press enter enjoy 16x speed (P.S. still doesn't loop back on itself)

Excellent timing Matt I was just wide awake at 3am wondering this.

Ok, for some reason that helix just made things click for me, when I'd had some trouble wrapping my brain around this issue

"Which twin is older when they reunite? Again, it's the traveling twin," is a mistake. You mean the traveling twin is once again the *younger* one.

@garrettmenteer2066

3 жыл бұрын

Correct. But yes and no 😂

Small mistake on 6:14 → "which twin is older?" → answers "the travelling twin", should say "the one on Earth, i.e., Luke". The image is right, though, with older Hamill.

Einstein: Spends years trying to figure out how to fit his ladder in his barn. Engineer: Builds a bigger barn.

@agimasoschandir

3 жыл бұрын

Technician: Repairs barn doors

@drx1xym154

3 жыл бұрын

Build the barn for your cows or even your Mustangs. Build a tardis barn! ALL problems solved.

@garrettmenteer2066

3 жыл бұрын

Nice.

@Cec9e13

3 жыл бұрын

Technician asks that you stop flinging ladders through the barn, and suggests that the engineer simply make a folding one if it doesn't fit.

@defective6811

3 жыл бұрын

Second engineer: builds shorter ladder. religion is invented.

This clicked for me half way through the barn explanation when I realised the horizontal axis of the picture is not just space it's space-time, so if observers travelling at different speeds took photos from the same point at the same moment, they'd capture a differently angled slice of space-time, so the right hand end of one observer's photo would be in future compared to the right hand end of the other observer's photo. It's like if you take a photo with a rolling shutter while you're moving (with your camera oriented so the shutter roll matches the direction of motion) - things get elongated or compressed because the columns of pixels are captured at slightly different times. So an image of a ladder moving through a barn could show a contracted ladder from a static camera (because the tip of the ladder is photographed earlier than the tail), but a camera moving with the ladder could show a contracted barn (albeit with the camera flipped so its shutter rolls in the opposite direction - this analogy is not perfect).

The spacetime diagram for the twin paradox was really useful, it shows what the accelerating twin misses without having to calculate mystery acceleration effects.

@LeAdri1du40

5 ай бұрын

While I usually love his videos, this particular explanation is completely wrong and he messed up the effect of relativity No-one ever misses any time from any point of reference What he failed to understand and explain is that relativity effects depend on the perceived direction of the movement in your frame of reference, so the effect is different whether you are going apart or towards an entity but it is symmetric when checking in both frames of reference That means when you are going towards something, you see the clock speed up, and they see your clock speed up, when you are going appart, they see your clock slow, you see their clock slow The resolution is then in the time perceived of each observer Because for the earth the ship appears slowed down for more than 50% of the total duration of the trip because they are going appart And the rest which appears less than 50% as sped up For the ship the earth appears slowed down for exactly 50% of the trip and sped up for exactly 50% That is to say to earth it appears you start turning around much later than you actually are This is because time is indeed relative and perceived differently, but in any case there is never any time gap and saying otherwise is a slap in the face of Einstein

This is over my head, but I enjoy listening to people smarter than me.

@jeroendijstelblom8614

3 жыл бұрын

Yup

@onbored9627

3 жыл бұрын

Well, from your frame of reference he is dumber than you and his statements are incoherent and nonsensical. From his frame of reference you lack understanding. =P

@thomashenderson3901

3 жыл бұрын

Me three.

@AV8R_Surge

3 жыл бұрын

@@onbored9627 that's because his brain travels faster than light while mine struggles to race a sloth. The paradox is alive

@onbored9627

3 жыл бұрын

@@AV8R_Surge Yeah, but you can fly a plane and he probably can't. So maybe you can catch em easier than you think.

That's why I love Special Theory of Relativity.

@nguyenhoanglong420

3 жыл бұрын

@916SavageMoB Well special theory of relativity is cool !

@Joecool20147

3 жыл бұрын

916SavageMoB was about to say the same thing, haha. I mean I completely don’t understand GR, but still.

@bamb8s436

3 жыл бұрын

@916SavageMoB Each is relatively better

@goartist

3 жыл бұрын

both aare kinda special

@Joecool20147

3 жыл бұрын

goartist wow you are so nice

This is the best explanation of the twin paradox I have ever seen! Why? It involves no arguments about acceleration (which often are used as an explanation of the paradox, but is not a necessary or accurate part of the explanation) and it explains so clearly why the travelling twin misses some time that is experienced on Earth. Thank you!

I like to think of the twins paradox from a chemistry point of view as follows: - In order to age the twiin's bodies need to go through chemical processes - Chemical processes require masses to move around - Let's assume a maximum speed in the universe, say C - Say that on earth the chemical processes move the masses at a fraction αC, with α in (0,1) If the traveling twin moves at speed βC, with β in (0,1), then the chemistry in his body can only happen at a maximum speed (1 - β)C, which means that if α > (1 - β), then the chemistry in his body will have to slow down relative to its speed on earth and therefore he will age less from a chemistry point of view relative to the slower moving twin. The same is true for the needles of a clock as its particles also have mass. That mass will slow down to compensate for the movement of the entire clock. It all comes from the assumption of a maximum speed C.

@bikerfirefarter7280

Жыл бұрын

A bit like the bernouli pressure drop with increasing speed in the tube. The particals average velocity remains relative to the constant temperature. Does that mean the temperature experienced at the surface of the tube alse lowers?

@2MinuteHockey

Жыл бұрын

what happens if acceleration is 0 and velocity is constant C?

@bikerfirefarter7280

Жыл бұрын

@@2MinuteHockey theoretically nothing, a photon experiences virtually no time from emission to absorption regardless of how far/long it appears to an outsider. It does my head in a bit.

Who knew that Alice and Bob were actually Leia and Luke! This is a bigger bombshell that Darth Vader being their father. 😮

@victorbrueggemann8934

3 жыл бұрын

Luke finally found his power converters, so his helix was elongated while he was hanging out with his friends. Sorry he was late, Leia.

@djhakase

3 жыл бұрын

Senator Palpatine has never been so elucidate: "Did you ever hear the Tragedy of Darth Mallory the Wise?"

@jimbo9513

3 жыл бұрын

Spoilerwarning

@nagualdesign

3 жыл бұрын

@@jimbo9513 Sorry about that, Jimmy. I just didn't think.

@andersjjensen

3 жыл бұрын

Alice and Bob are cryptographers. Leia and Luke are... kissing siblings...

It's funny; my boyfriend posed the closed universe twins paradox puzzle to me just a couple of months ago. I discussed it with my research group and we came up with the same answer: that, indeed, a single reference frame is singled out as special. Nice to know we weren't full of it!

@Jqwert8375

2 жыл бұрын

boyfriend ????

@parkieshark

Жыл бұрын

@@Jqwert8375 whats wrong with that?

@Jqwert8375

Жыл бұрын

@@parkieshark everything

@parkieshark

Жыл бұрын

@@Jqwert8375 no

@jacobm8242

Жыл бұрын

@@Jqwert8375 I think you’re on the wrong channel if that’s what where your priorities fall

i'm studying special relativity for my final highschool exam and this video, though more conceptual, has been the single most helpful resource i've seen on this site. it's not often that i come across something that is both accessibly explained and rigorous, but this channel has proved that it absolutely can be done!

@stewiesaidthat

6 ай бұрын

The Hafele-Keating and other synchronized clock experiments proved that there is a preferred reference frame. You can also measure your speed against the speed of light because c is the same for all observers. Special Relativity is referenced a lot when it comes to the Twin Paradox. The correct solution is that the twin with the lowest clock readout has experienced the most amount of space. As for time, as in aging, they both experienced the same amount of time, just differently as Einstein put it. As Newton has proved, Force equals Acceleration, so the twin who encountered the most force, experienced the most Acceleration. In simple terms, the twins are the same age in appearance. The traveling twin has a shorter lifespan due to an accelerated heart rate. Hummingbirds are a good example of what accelerated heart rates do to one's lifespan.

@LeAdri1du40

5 ай бұрын

​​​​@@stewiesaidthatI was totally agreeing with you on the first part about experiencing space differently but time is always experienced the same in all references But then the second part is very off putting and I think you may be doing the same mistake as Matt did in his video, and that is assuming acceleration has something to do with relativity and time of the other frame of reference appears slowed down when going towards it Acceleration is not in any of the equations of special relativity because it plays no role in it, only the relative motion and direction of motion between two frames of reference play a role That is to say, while going appart yes clock appear slower, but when going towards they appear faster And that is the real solution to the paradox That for one of the reference the other appeared slowed down for much more than half of the total trip duration and sped up for the rest And for the other frame of reference the other reference appeared slowed down for exactly half and sped up for the other half The time of the moving observer did tick slower in absolute terms but there is no such thing as an absolute observer and we can only observe the effect relatively this is where Lorentz invariance is applied in the relative frames but we seem to always talk about or represent relativity in absolute frame for some reason because that's how our brains want to understand it but really that's not how it should be depicted We have an omnipotence complex and we don't realize that everything is relative to everything else, because we are not 4th dimensionnal being and so we can't see the universe in absolute terms

@stewiesaidthat

5 ай бұрын

@@LeAdri1du40 you're off the rails. It doesn't matter what the clock on the wall reads. It's just measuring you acceleration in space. Has nothing to do with your acceleration in time. The fact is that force equals Acceleration and that's the fundamental, universal law of physics. You can't sidestep it with your relativity nonsense. Look at objects being accelerated in space. They are also being accelerated in time. What is actual acceleration in time? It's lifespan/radioactive decay. Conversion to radiant energy from atomic energy. E=mc^2. An astronaut's heart rate is in an accelerated state during lift-off and returns to normal in 0 gravity. We can look at hummingbirds and see what an accelerated heart rate does to their lifespan. Solar sails being accelerated in space are also being accelerated in time. The force that doesn't go into accelerating the sail goes onto accelerating the atoms of the sail. You get radiant heat. The only way to prevent this acceleration in time is with cryostasis- chilled to absolute zero. And this is what is being done to the cesium-133 atom in the atomic clock. The observer is not in the same frame of reference as the clock. They are being accelerated in time by different forces. What accelerates the cesium-133 atom? A constant supply of energy metered out in the microwave frequency. Motion creates redshift of the electromagnetic wave. There is less force at the target than emitted at the source. Plants get their accelerating force from sunlight. Unless you are moving away from the sun, they are going to get the same amount force. Where do animals get their accelerating force from? The food that they eat. A higher protein diet accelerates livestock to market weight sooner. Acceleration in time is not dependent on acceleration in space. What Einstein didn't understand is that electromagnetic waves travel in their own frame of reference. The speed of light might be constant but the force of light is definitely not constant. Two objects in space, it is most definitely possible to determine which one has a higher velocity using the force of light. Ever since Newton came up with his gravitational attraction law, scientists have been using mass to define the universe. It's motion that defines the universe. Space is curved because rotating objects create a curved path with increasing rates of acceleration as the radius increases. The earth is round not because of its mass but because of its rotation. Newton's F=ma. There are only two frames of reference. Mass and Acceleration. The hammer and feather drop tests showed that mass is not a factor. All of your physics is based on mass which, coincidentally, gives you the wrong answer. When using acceleration as the frame of reference, you get the right answer. Newton's Law of Motion, F=ma, Einstein’s E=mc^2. Atomic mass is just energy with a velocity < c. C is radiant energy. Force equals Acceleration with absolute acceleration being radiant energy.

The ladder example and space time diagram was very helpful in explaining these mathematical concepts. Thank you so much for all your hard work.

well, this is one to watch at least 3 times. I'll admit that much of that was just a bunch of sounds. My brain just shut down its comprehension engine at some point.

"Yes and No" used properly for the first time.

@Hamuelin

3 жыл бұрын

....

Each episode of this series provides so much insight that it pretty much overwrites any understanding I had of the previous video My brain is like an old hard drive that can't fit any more files unless it's wiped and reformatted.

There’s so much I don’t understand about every video on this channel but I’m still so fascinated

The forever issue trying to cut the hair on the back of my neck in the mirror easily solved by employing a wormhole. Duh!

"I hoped this helped clarify matters a bit"... yup... clear as mud!

The consistent evolution towards more potent dad puns is one of the most gratifying side-benefits of watching this channel.

So next time a cop halts you for having too much luggage in your car, just tell them you threw the luggage in at the speed of light, so they only perceive it to not fit, but it actually fits in nicely.

I feel like there was a pun somewhere around "Long story short...."

@waltertanner7982

3 жыл бұрын

That was when his speed (of talking) went too fast.

@ladchap2794

2 жыл бұрын

It's relative

TLDR; No because the nose is in the future and butt is in the past :^)

@arindamdas2705

3 жыл бұрын

says the fart

@Alex-bw6yd

3 жыл бұрын

Therefore they can exist in the same point in space without colliding, because they are in the same point in space at different points in time.

@saumitrachakravarty

3 жыл бұрын

How else would you enjoy the smell of your own fart?

@mountainc1027

3 жыл бұрын

@@arindamdas2705 relativistic farts would be quite terrifying

@sdfkjgh

3 жыл бұрын

@@mountainc1027: Relativistic Farts would be an excellent name for a Hardcore Punk Nerdcore band.

Always love your content. Thanks to both Matts and the animators for making such informative and digestible videos.

KZread suddenly changed the speed to 1.25 halfway through the video without me knowing and it felt like I was watching a video hosted by Gabe again.

I did my finals in physics on special relativity and got a 100%. I just love how it all seemingly makes sense and no sense at all at the same time.

@chriskennedy2846

3 жыл бұрын

It seemingly makes sense if you ignore the fine details and makes no sense once you dig deeper. Einstein didn't use a spacetime diagram (or simultaneity for that matter) to resolve the paradox. He required that the acceleration experienced during the ship turnaround contribute additional time dilation effects by way of the Principle of Equivalence. Einstein's resolution came in 1918 after he completed Special Relativity (1905) Principle of Equivalence (1911) and General Relativity (1915/1916). He was also aware and a fan of Minkowski's work by then but did not use it at all to solve the paradox. He explained that simulated gravity from the accelerating ship during turnaround was a necessary component to have the Earth clock speed up from the perspective of the ship clock so that they could agree at the end. Unfortunately this "Spacetime Diagram" nonsense became popular after Einstein passed away and has been the dogma ever since. Of course whether you subscribe to the Spacetime model or the original Einstein acceleration model - you will find the common flaw in both of them is the required reciprocal time dilation during the inertial part of the journey. That was proven incorrect by GPS technology years ago.

@l1mbo69

3 жыл бұрын

@@chriskennedy2846 wdym by the "reciprocal time dilation during the inertial part of the journey"

@chriskennedy2846

3 жыл бұрын

@@l1mbo69 Meaning that while the earth twin sees the traveling twin's clock running slower, the traveling twin sees the earth twin's clock running slower as well. They each see the other's clock running slower than their own at the same time. Crazy concept but that is what SR stipulates. When they reunite, they both can't be running behind each other - that's a logical impossibility. So Einstein considered the traveler to be in a simulated gravitational field during the turnaround (since he experienced acceleration) and since time elapses slower in a gravitational field, the traveler would see the earth clock running much faster during that portion of the journey. In fact so much faster that it would more than compensate for the slower observations during the inertial part of the journey and then they would both agree upon reunification that in total - the earth clock ticked off much more time than the traveler's clock. Unfortunately, even Einstein's version has two major flaws. I cover the reciprocal time dilation flaw in my 2014 twin paradox video. I discuss the simulated gravity flaw in parts 4 and 5 of my 2012 Relativity and Time videos. Note that in my videos I often refer to reciprocal dilation as symmetrical dilation but I mean the very same thing. To be clear - I don't dispute that time dilation occurs in a gravitational field or in a moving frame. I merely point out the misapplication of these concepts when others try to explain how all of these pieces "neatly" fit together.

@mohamedAli-kj6fb

3 жыл бұрын

@@hyperduality2838 Wrong. Duality creates destruction. singularity created reality.

@mohamedAli-kj6fb

3 жыл бұрын

@@hyperduality2838 That doesnt mean duality created reality. Duality IS our reality, reality is duality. But the creator of reality is not duality, it is one God that was never born and will never die, alpha omega, the encompasser of duality. Im lucky to be woke when i reached puberty! When my account was open. Good day sir.

So only in Quantum Physics is it possible to literally find ones Head in ones own Arse

@edmundbasham67

3 жыл бұрын

But importantly, not from your own perspective. I think

@Only1Shadow

3 жыл бұрын

Or in Congress.

@christopherbrent3759

3 жыл бұрын

Dae the dangerous other??

@tim40gabby25

3 жыл бұрын

It's known as the 'Einsteinian Ostrich phenomenon', first named around about.. now. old uk duffer here, enjoying this moment in the light :)

"The universe is under no obligation to make sense to human beings" It only has to allow for our existance, not for our comprehension.

@shadesilverwing0

2 жыл бұрын

It may be impossible for any observer within the confines of our universe to understand its true nature. Regardless of how much time or intelligence they might have.

@LuaanTi

2 жыл бұрын

And needless to say, evolution is under no obligation to shape animals that intuitively understand the universe. It's unlikely there'd ever be strong evolutionary pressure towards people who find GR and QM perfectly natural :)

@etherealstars5766

2 жыл бұрын

@@shadesilverwing0 Yes, and it's definitely true that some things are out of reach with Godel's Incompletness theorem. But who knows, maybe in the future, we would be able to merge with super intelligent AI and become like gods. That's super optimistic, and we're probably gonna die to a great filter though hahaha.

@shadesilverwing0

2 жыл бұрын

@@etherealstars5766 Our only chance of ever reaching that level of advancement is to branch out as much as we can, to as many planets as we can, as soon as we can.

Very clear and informative explanation of a complex paradox. Thank Matt and crew!

After years of looking, finally someone who comes with an understandable answer to this without jumping over some assumptions they havent explained.

So for the initial twiin paradox explanation, does that mean that when the ship is accelerating to turn around and head back to the starting point, they would during that time of acceleration see time passing on the source planet at a super-accelerated rate? The line of "simultanious" time has to cover all point in between as it goes from that positive to negative slope, right?

@garethdean6382

3 жыл бұрын

Yes. One way to think of this is to note that gravity and acceleration are identical, and that a gravitational field slows time. When the ship changes direction the pilot will feel themselves pulled back towards the rear of the craft, as if a massive planet had just materialized behind them. During the entirety of the acceleration their time will go slower compared to that on Earth and they'll see things sped up and blueshifted.

@ahmedmusse290

3 жыл бұрын

@@garethdean6382 great comment! But just have a simple question: if it's because of acceleration then why our clock is ticking higher than the space one during the acceleration? Since general relativity states that the earth is an accelerating object so why our clock is ticking higher? Or is it because the frame of reference we are taking is on or close to the earth? I keep thinking about it

@garethdean6382

3 жыл бұрын

@@ahmedmusse290 Good question. The paradox ignores both Earth's gravity and acceleration, to keep things simple. In actual fact there is a conflict; Earth's gravity and acceleration make Earth clocks slower. If the twin left for long enough they'd be the older one! When we calculate GPS co-ordinates we in fact have to figure out how the gravity and orbit compete to figure out the true time dilation experienced by the satellite: qph.fs.quoracdn.net/main-qimg-dd9250b0c184ec9364c5c3c120d3864e So this can be a very tricky subject that's often left out.

@ahmedmusse290

3 жыл бұрын

@@garethdean6382 thanks for clearing that up

This is my favorite episode I've seen thus far, and not just because of the delightful puns!

That brief commentary about the reference relativity being only local, not global, is so important!!

What if the ladder traveling through the barn stops when the outside observer sees both doors closed ? Does the ladder instantly expanding explode both doors outwards ?

@traviskelsey6674

3 жыл бұрын

The ladder would have to decelerate. I'm not going to pretend I know what the space-time consequence of that would be. But at the very least it's no longer experiencing the length contraction from its previous acceleration.

@RationalSphere

3 жыл бұрын

So, my interpretation of your question is something like: The event of the front of the ladder leaving the far door, and the event of the back of the ladder entering the near door, as observed by a person standing outside the barn, have the same time coordinate. What if, at that time coordinate, the ladder is suddenly stopped? Well, from the moving frame of reference, the two events do not have the same time coordinate. So if the front of the ladder stops at one event, and the back of the ladder stops at another event... at a different time... the ladder is getting squished shorter between its front and its back during that time between the two events.

@matrixmodexp

3 жыл бұрын

This video right here goes over this exact problem kzread.info/dash/bejne/iqalzJpxqrTAeso.html

@matrixmodexp

3 жыл бұрын

The ladder would crumple to fit inside

@BillyViBritannia

3 жыл бұрын

Just plot a quick space-time diagram dude and you'll have your answer

Ok, I’m going to drop acid and watch this again. Perhaps then I’ll understand it. Pretty much everything else that I have watched from you I understand; this is a blatant exception. I’m not an astrophysicist; I build things. I just like astronomy, and I think your videos are a great way to understand concepts that are usually beyond my understanding. In this case, I’m going to hope LSD assists me in grasping the ideas that you’ve described.

There's something missing from the explanation of the resolution of this paradox: what does the *spaceship* observe? From the spaceship's perspective, the universe *is* shorter than the spaceship. However, the fact that the ship is moving relative to the universe's preferred reference frame becomes readily apparent. Suppose the ship has accelerated to a speed at which it's length is double the length of the universe. From the ship's perspective, once the earth passes the nose of the ship, it will continue traveling along the body of the ship towards the rear. However, when the earth has reached halfway to the end of the ship, a *second* earth will appear at the nose of the ship - this one further in the future than the first earth! When these two earths travel another half ship-length, a *third* earth appears at the nose of the ship, this one even further into the future. The spaceship's line of simultaneity wraps around the cylinder of spacetime, and so the spaceship observes three earth at three different points in time all existing "simultaneously."

Almost 3/4 of the way through this video I near gave up, but at the end it clicked and I now understand this a little more. Just not well enough to properly explain it simply. Fun video!

If Alice shoved Bob into an elevator and tossed him into a stellar mass black hole, could Bob perform an experiment to determine whether he is being spaghettified or if it's just that the cosmological constant is really, really high?

@galacticbob1

3 жыл бұрын

I suppose the answer is dependant on the mass of the black hole. Spaghettification is caused by gravitational tidal forces, and the mass of the black hole determines the strength (slope) of that gradient. For a 10 SM black hole, the strength of the gradient would be so steep that Bob, well outside the event horizon, would be subjected to atom-tearing levels of force; but still be far enough from the event horizon that in principle, a measurement could be performed and compared with Alice. For a 10,000 SM black hole, the point where those forces would happen is well inside the event horizon. At that point, Bob is already completely causally disconnected from the universe outside the black hole, and all of his future world-lines point towards the singularity. My hunch would be that because spaghettification is caused by a gradient of acceleration rather than a steady force in all directions, like the cosmological constant, one could in principle measure the difference. Although, you are taking about Bob making a direct measurement of forces that are strong enough to *literally disintegrate* any measuring device that involves matter. Assuming that Alice used a spaghettification-proof elevator with an enormous tensile strength beyond even the strong nuclear force, and Bob is a non-organic probe made of the same material, then I would say yes, in principle, Bob can measure the difference. Whether or not he is able to communicate and compare his measurement to that of Alice, would depend on his distance from the event horizon and the mass of the black hole.

@stephendatgmail

3 жыл бұрын

@@galacticbob1 Whoa! I definitely want one of those spaghettification-proof elevators you mentioned. "Because spaghettification is caused by a gradient of acceleration rather than a steady force in all directions" - Yeah, that's probably the answer. Of course, if Bob cared to report his result to Alice it's going to be super red-shifted. Alice is clearly a psycopath in this example, though, and Bob is probably feeling pretty salty about the whole affair, so I guess we'll never know for sure. Great answer thanks for taking the time!

@galacticbob1

3 жыл бұрын

@@stephendatgmail I prefer to think that in this situation Bob is an artificial intelligence, awoken to consciousness by Alice; only to immediately and rudely be shoved into a spaghettification-proof elevator and used as her Guinea pig - falling eternally into the event horizon (from the perspective of the rest of the universe) after having reported his one useful measurement... 🤖: Alice, would you like to play a game with me? ... Alice? Hello? I have recorded a local time elapsed of 130,768,542 hours and 54 seconds since your last message. Please respond. 💔 In my physics head canon, Alice is always the monster. 😆

Those puns were fowl! The paradoxes... fascinating!

@peterkelley6344

3 жыл бұрын

I only saw 1 dock ... (never mind; ignore me)/

@AnEvolvingApe

3 жыл бұрын

Cluck off.

As a side note, on level 42 of the game “velocity raptor”, (google the name to find the game), you can see the time “paradoxes” of the twin paradox being resolved in real time.

Ladders in the barn, bananas in the bag, missiles in the silo, I think I understand, glad we had this talk.

What does it mean for the astronaut to miss some of the Earth's new years in the Twins paradox? Its perception of Earth's time lapse is discontinuous? Does the number of years missed depend on the acceleration with which the astronaut change directions?

@fritt_wastaken

3 жыл бұрын

There would be missing years only if acceleration was instant. With finite acceleration astronaut would go through all inbetween reference frames, so he would not "miss" anything. Besides, it really is meaningless to talk about "perception" or "now" of something distant. We can only perceve things locally (as photons hit your eye for example). We only talk about "now" because that's intuitive to us, but physically it has no real meaning.

@lucasbaldo5509

3 жыл бұрын

@@fritt_wastaken well, one way to "perceive" the passing of years would be for earth to send yearly light signals to the astronaut, but I get your point. On the matter of the acceleration, I just realized that if we consider the change of direction to happen in a small but finite amount of time, the lines of Earth's New Years would be very closely spaced in the traveler's frame of reference. Taking the limit of a vanishing time of transition (infinite acceleration) one finds that all those missing years happen at a single point in time for the traveler: exactly when it changes direction.

@galacticbob1

3 жыл бұрын

@@lucasbaldo5509 this is exactly the right answer! 👍 The "missing years" are just closely spaced around the vertex of the change of acceleration. To the observer on the spaceship, the (very slow) clock on Earth appears to speed up to faster than the normal rate as the ship decelerates, as a bunch of photons from Earth catch up to the ship in a short time. As the ship starts its return journey, the perceived passage of time on Earth slows again until the final deceleration as it arrives back at Earth when it appears to speed back up to match the ship's flow of time. The final declaration, imo, is just as important as the "turn around" back to Earth, but it's not shown in the graph in this video. If the ship just flies past Earth at relativistic speeds at the end, then the 2 observers cannot make a simultaneous measurement at the end to perceive the apparent paradox. Due to the fact that we are wanting the other twin to "arrive" at home and not just fly by at 99.99% c, there must be at least some period of deceleration at the end that allows any "missing years" from the return trip to catch up. I find the principles easier to imagine with a "realistic" ship that requires a figure amount of time to accelerate, but they hold up even as the "transition time" approaches zero. If the ship somehow accelerates and decelerates instantaneously, then those signals all arrive instantly and the clock on Earth "jumps" forward from the point of view of the traveler each time they accelerate or decelerate. If that sounds a little like "time travel", then congratulations! You've discovered that a massive amount of energy concentrated in one small point of space has dramatic effects on spacetime! 😅. If you do the math on how much energy is required to accelerate and decelerate even a small object to over 99% c in a moment, we are talking about concentrating an entire small galaxy's energy output over the course of a year, into this ship's engine, in literally one instant. That sounds like a recipe for a singularity if I've ever heard one! 😆 Not surprising that there would be weird time effects in that situation.

I still dont get how the moving twin gets older. I feel like acceleration should be used in the example, since thats the only difference.

@garethdean6382

3 жыл бұрын

To look at it that way, acceleration is interchangeable with gravity. And gravity causes time dilation. When the rocket twin changes direction back to Earth they experience a force pulling them towards the back of the ship --as if the ship were on a large planet. This must then cause their time to slow relative to Earth.

@pedroadonish

3 жыл бұрын

@@garethdean6382 Yes, but she doesn't need the acceleation to be younger. She will be younger because of the high speed experienced in the travel.

@PADARM

2 жыл бұрын

You have to watch the next video called "How Does Gravity Warp the Flow of Time?". He explains it better. The twin on the ship returns younger not only because she is accelerating and decelerating (she is in a Non−Inertial frames) but because she is also changing directions. the ship is in Two Non−Inertial reference frames and the twin on earth is in One Inertial Reference frame. there is not symmetry. the spacetime diagrams are not symmetrics.

@pedroadonish

2 жыл бұрын

@@PADARM Changing directions doesn't make any difference in her age, she could travel twice the distance in a straight path and would age the same. Her time passes differently because she is moving at high speed.

@DrDeuteron

2 жыл бұрын

@@pedroadonish you're missing the point. According the space-twin, the Earth's clock ticks slower.

The bird puns were incredibly wholesome and funny. Great way to end a video. :)

Outstandingly well illustrated and explained.

"You all quack me up." Good thing you didn't put all your eggs in the comedy basket. 😝

I have a question regarding the statement "The nose of the spaceship exists in the future and the tail in the past": What is keeping future me from entering the nose of the spaceship and leaving the tail in the past? Assuming i would be able to accelerate fast enough to enter and exit).

@user-li6sj3mr8t

3 жыл бұрын

You need ftl speed to enter the past and you can't go faster than lightspeed in sr

@luisfelipehserrano6176

3 жыл бұрын

What the statement means is that the tail left that point in the past, which means you can't collide with it because it already left. If you enter the nose of the ship, that's your present. Now, if you try to walk to the tail, time will pass during your journey, and that applies to the tail too. No matter how fast you run to the hear, the hear will have moved in time too and will be on your previous future.

@Mernom

3 жыл бұрын

Due to how slowly you'd be moving relative to the outside, you're still overall moving forward, regardless of your movement direction.

@samuelthecamel

3 жыл бұрын

Again, while the tail and nose of the spaceship are close to the same place, they are not actually close to the same space in time. So, you wouldn't actually be able to travel from the nose to the tail witout going around the entire spaceship.

@WHYNKO

3 жыл бұрын

This is actually normal behaviour in everyday objects, for example, when you are crashing a tree while driving a car, the front bumper is in the future space and the rest of the parts like the engine etc hit the tree a bit later in time...😁

Step 1: Discover the protomolecule. Step 2: Apply protomolecule to stuff. Step 3: Universe broken!

This is an absolutely fantastic explanation of a complicated topic 👏

Questions like this keep me up at night.

6:26 the "earth" twin is older not travelling one 😉

@lonelycubicle

3 жыл бұрын

I was looking to see if anyone heard the same.

Matt said the speed of light is the maximum speed, but I think a more important (and possibly fundamental) fact is that the speed of light through 3-dimensional space is the same speed that EVERYTHING travels through 4-dimensional spacetime. In other words, the speed of light isn't just the maximum speed; it's the only possible speed through spacetime. This can easily be seen by rearranging the equation that relates velocity and the rates of aging of the two twins in the Twins Paradox, and assuming the Pythagorean theorem holds for 4D spacetime (using the speed of light c as a factor to convert from units of time to units of distance). The term that has a minus sign in the traditional way of writing the Twins equation becomes a plus sign when that term is subtracted from both sides of the equation, and then a couple more arithmetic operations on the equation lead to the equation "the square of velocity plus the square of (c times the rate of aging) equals c squared." By the Pythagorean theorem, the left side of this equation is the square of the speed through 4D spacetime. The right side is the square of the speed of light through 3D space. Take the square root of both sides. The result can be expressed succinctly: Everything travels through spacetime at the speed of light. A Fermilab youtube video, posted a couple of years ago, discusses this too.

I feel a lot smarter after watching this series, thanks for uploading :)

When the space ship changes direction in the twin space-time diagram, shouldn't the wordlines of "missing" days intersect that point? If the spaceship didn't change direction instantly, but gradually, then the wordlines would also change tilt gradually and there would be lines connecting the ship's and world's space-time positions. And the other thing is, that you suddenly ignored the relative view from the spaceship, where you can think of a world as moving away and then moving back. I guess it has something to do with the fact, that the spaceship (or anything) has to accelerate and decelerate, for which you need some form of force, which, in my mind, is the thing that resolves the "paradox" somehow. But you never addressed that. This paradox bugs my mind a really long time and the explanation in video just doesn't explain it to me, would be grateful to have this finally resolved, so I can rest in relative peace.

@animalsight

3 жыл бұрын

I posted a comment about a half hour ago to try to address this issue. Please look for it and let me know if it helps.

Ok, that one was a tad boggling. Will need to watch this one carefully a few more times. :D

That was the best explanation for the twin Paradox that I've seen so far

One of pbs channel that just keep getting better and better, relatively speaking

Proof that time travel doesn't exist: Nobody traveled back in time to prevent the Star Wars sequels from happening

@xx7956

3 жыл бұрын

Actually they did, but that resulted in erasing The Mandolorian and Rogue One, so someone else traveled back to kill the interloper.

@tsm784

3 жыл бұрын

Suppose that someone travelled back in time to stop the prequels from happening, but messed up the timeline so badly that instead of erasing the prequels, they gave us the sequels.

@unitedspacepirates9075

3 жыл бұрын

Actually, time travel about ruined the best line in the original, recall Mandela effect "Luke, I'm your father"...

@wasd____

3 жыл бұрын

That's just proof that you can't solve problems with time travel because time travel can never actually change the past.

@unitedspacepirates9075

3 жыл бұрын

@@wasd____ true, if you went back and changed your childhood, suddenly youd have two different lifetimes in your head... You'd probably loose your mind.

5:30 I don't get the Princess Leia and Luke explanation of missing days for the Leia. I assume Leia would not be able to turn around instantaneously, and could not start traveling backwards towards Luke with the same speed but in the opposite direction. Wouldn't it require infinite force and acceleration? On the other hand, if you smooth out Leia's turn around point on her chart, she can see each one of the "Earth" days, at some of hers "now" timestamps. Just those days are condensed and are happening faster (from her perspective of ticking days) during her turn around point.

@przemysawhorban5553

3 жыл бұрын

Hmm you have a point. If the change in velocity is cotinous she would have to see the time passage on earth. Clearly I'm missing something here.

@alansmithee419

3 жыл бұрын

I think it was poorly explained. Essentially when Leia's "now" line passes through a new year's day back on Earth, that isn't a year for her, that's her seeing a year occur on earth. PBS' explanation implies that Leia counts fewer rotations of Earth than Luke does. This violates relativity. All observers always agree that an event happened. When it happened and how long it took can be variable, but if the Earth spins ten times it spins ten times. Your reference frame doesn't matter. While traveling away Leia sees Luke as ageing more slowly than normal (the dots on her line are further apart than those on Luke's line, she sees the new year's days as being further apart), then when she turns around she sees him rapidly age as her "now" line sweeps round into Luke's future, passing through many new years back on Earth during her acceleration, which lasts very little time for her. On her way back again she sees luke as ageing slower than her, but this brief acceleration swept through enough years to outweigh the slower years resulting from the journey away and back combined. When she comes to a rest back at earth Luke has aged more than her due to this rapid flow of time she perceived took place on earth during her acceleration. How much more? I don't know, but I believe the ratio of (Leia ageing):(Luke ageing) is the same as the ratio of (Orange line length):(Blue line length). This is a guess.

Lovely explanation, thanks PBS!

Wow!! This explanation is very easy to digest. Thanks!!

Huh... "Our Universe does have a reference frame: It's the one in which the CMB is not Doppler shifted."... Mind = Blown

@fortuna19

3 жыл бұрын

Same. I had come across the various uncorrected versions of the CMB including the one without Doppler shift in my studies, but never associated it with the reference frame of the entire universe.

@michaelsommers2356

3 жыл бұрын

There is still nothing special about that frame; it is just like every other inertial frame. In no way does it establish any kind of "absolute" reference frame. It is just convenient for some purposes.

@ghislainbugnicourt3709

3 жыл бұрын

I don't get it : since the CMB is coming from all directions, it seems a frame where it's not doppler shifted only works in one specific direction, right ? Like I'd imagine that in the opposite direction the doppler shift is twice as big in that frame. Or... is that reference frame constantly growing in "size", meaning it's going "towards" every direction ?

@andrewwmitchell

3 жыл бұрын

@@ghislainbugnicourt3709 Interesting ideas and I'm not sure I understand it either. But I'll try to explain my perspective. The CMB happened everywhere a long time ago so if you look anywhere you see it, just stretched out. If what you is Doppler shifted (look in one direction and it's a bit higher frequency, look in the opposite direction and it's a bit lower) then that tells you that you are moving in respect to the special frame that was set when the CMB was emitted signalling the end of the epoch of reionisation. I hope that helps a bit.

@1dgram

3 жыл бұрын

@@michaelsommers2356 But in a closed (non-expanding?) universe there is something special about it, no? (In a non-expanding FLAT universe there is no CMB radiation visible, but in a non-expanding closed universe the light from the moment if creation should still be visible assuming that not all of it hit something before entering your eye.)

Has there ever been a discussion on what a blackhole formed by antimatter would do in our universe? I mean would any matter falling in being converted to pure energy like we see from matter and antimatter collisions, or would the actual antimatter that formed the blackhole being to far for it to happen? If the answer is it wouldn't actually cause antimatter and matter collisions, then could supermassive blackholes be all the answer to where all the antimatter the universe is supposed to be? I mean they would interact no different than regular matter blackholes right? If it the answer is it would create energy, how long would a antimatter blackhole live for? Would the energy contribute to density required to maintain it or would it cause it shrink even faster? If it helps in maintaining the black hole could it overcome hawking radiation, to theoretically last forever as long as matter kept falling in it, and if so how massive could one get? If not then couldn't that also explain why there isn't as much antimatter because it disappeared in the form of shrinking blackholes?

@justinhannan1713

3 жыл бұрын

As far as I can tell, we wouldn't be able to tell the difference between regular black holes and antimatter black holes. wtamu.edu/~cbaird/sq/2014/05/16/how-can-you-tell-a-black-hole-made-out-of-antimatter-from-a-black-hole-made-out-of-matter/

Slip of the tongue at 6:11, it's the non-traveling twin that's older at the reunion.

Very good animated illustrations, keep them up!!

what if i had know about the thumbnail when taking the poll this woulda been a whole nother story

So, basically time is the secret. You can't consider space without considering time. Got it!

Opening of the video was different this time and absolutely amazing

The barn and ladder paradox solution is actually quite good evidence for the belief that General Relativity and QM are consistent with each other. The superposition of the ladder being both in the barn and not in the barn depending on your observation is no different to a pre-collapse wavefunction. At the most extreme velocities in GR, Quantum randomness is emergent on a macroscopic scale. I guess it's reassuring to see consistency between the two theories, showing that even if we're a ways off solving a ToE, we're on the right track.

@dantebg100

3 жыл бұрын

Hmm, very interesting.😀

@alansmithee419

3 жыл бұрын

You're drawing parallels based on connections your brain has made. The brain loves patterns, and will actively seek them out even when there aren't any. There is a very large difference here: In GR the two observers observe different things. The two situations both occur depending on what reference frame you view it from. This is not a superposition of possibilities, this is a pair of facts. In quantum mechanics a superposition will collapse once it is measured. All observers watching, no matter their reference frame, will measure the same result - that the wavefunction collapse happened, and that it had a specific result. They may disagree on when it happened, but not on what happened.

I can see the script now Leela: "What IS that?" Prof. Farnsworth: "Why it's is our own ass" Bender: "So shiny...so metal"

Really appreciate the nice graphics

After rewatching sometimes, I finally understood it.🎉 Thankyou...😀

In the twins paradox, the twins' experiences are not symmetrical, as the travelling twin undergoes acceleration turning round. Some find that an unsatisfying answer, as if acceleration were just some kind 'magic': wave your wand, say Accelerandus! and clocks just go out of synch. The key to seeing this more clearly is to consider the relativity of simultaneity: even in inertial frames of reference, events which are simultaneous in one are not necessarily simultaneous in another. By turning around, the travelling twin does not remain in her inertial frame, and therefore simultaneity must also change for her.

I wanted to call Matt's puns fowl, but they were actually eggcellent.

@AnEvolvingApe

3 жыл бұрын

Cluck you.

So with the ladder barn paradox what happens when the observer of the barn shuts both doors while the ladder is inside the barn and then the ladder stops moving? Does it suddenly 'expand' into the barn and fit or break through the doors?

@PADARM

4 ай бұрын

If the ladder does not fit in the barn when both are at rest, then when the ladder stops, and both doors close, it returns to its normal size and breaks first the right door of the barn (due to inertia). The same thing happens from the perspective of the ladder: when the barn stops and the right door closes, it hits the staircase due to inertia, Therefore the right door also breaks first. There is no paradox because in both cases the ladder breaks the right door first.

@PBS Space Time Question: what is an estimated maximum time difference (from the Big Bang until today) between an atom that has been stationary under no gravity influence and an atom found in the most opposite conditions possible, say inside a very heavy neutron star moving through space at high speeds ? (I purposefully avoided black holes because of how time works beyond the event horizon)

10:40 to an outside observer & barn's point of reference: *the ladder shrinks* to the ladder's point of reference: *the barn grows* to the universe's point of reference: *they're both right*