What Actually Expands In An Expanding Universe?
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- Опубликовано: 22 окт 2020
- As the universe expands, #expanding #space is said to "stretch" photons. But if it stretches photons, does it also stretch molecules, galaxies and you? A portion of this video was sponsored by Salesforce. Go to salesforce.com/veritasium to learn more.
Special thanks to Geraint Lewis - this video was based on his paper "On the relativity of redshifts"
arxiv.org/abs/1605.08634
Check out his RUclips channel: ve42.co/gfl and books: ve42.co/GFLbooks
References:
Expanding Space: the Root of all Evil?
Matthew J. Francis, Luke A. Barnes, J. Berian James, Geraint F. Lewis
arxiv.org/abs/0707.0380
Editing and VFX by Trenton Oliver
Thumbnail by Ignat Berbeci
Music from epidemicsound.com
#SMB #smallbiz #startups #SalesforceEssentials
![Minecraft but Players Can Upgrade [FULL MOVIE]](http://i.ytimg.com/vi/QRRgLJs4ZPk/mqdefault.jpg)
Don't know if it's universe, but I expanded a LOT in this quarantine
nobody cares
@@lemau8458 why are you like this
Y E P cos he’s lonely and has to resort to toxicity to gain attention since he can’t get it naturally
@@TheDrumstickEmpire true
I expanded too
I had to take some acid though
Bucket list after corona times:
1. Going in outer space
2. Turning off Electromagnetic force
man i wonder how something like this would feel...
@@GRAITOM it’s called death.
Same
After corona times, it will be miller time. Followed by Coors time.
@@GRAITOM Well, . . . if you concentrate, intently and without choice of self, upon being able to travel within your physical existence at the subatomic level, then maybe you just might be able to 'feel' an emotion. But, . . . you'd have to be able to concentrate first.
"You might think there's only one type of redshift. But in fact, there's three. But actually, there's one."
As an addition to explain the difference in observation, to greatly simplify. The redshift in light kind of works the same for sounds. When you hear the siren of an ambulance it sounds different when the ambulance is driving towards then when the ambulance is drives away from you. thats why you know it is moving towards you or away even if you don't see it. But the sound the ambulance makes is always the same, just perceived different
Thx
NO . Incorrect. Unlike Light which is itself a thing that's why passes through empty space as a particle it can where as sound is just a disturbance in a medium like air in siren case for ambulance.
Example: it's the difference like between the impact/effect/force office standing man pushing something to that of him hitting it with speed.
Sound is (mechanical) produced by physical forces in air to be simple but not light it is it's on particle with fixed speed.
@@jairussiriyalaofficial8922👍
If this was true then your practically saying the expansion of the universe started from some point and has and end point meaning the start point of the siren when you first hear it and the end as the ambulance gets further away the sound ends and can no longer hear it.....Scientifically they haven't yet proven when/where a start of something like the universe but only know it has to existed or we wouldn't be here...what's actually astounding me in saying that is there maybe be a end to our expanding universe for example a balloon when you blow it up it expands until eventually it pops not saying the universe is round just saying that's how expansion actually physically works .
@@jairussiriyalaofficial8922 I concur
I'm happy that Derek is now uploading frequently.
mind tho, these videos need hours or research, hours of editing, hours of planning, a lot of hours really. It’s impressive that he’s posting like every week
Its almost like a miracle
Im not less quality ... Quality over QUANTITY
Mee to
@Abhishek Thorat His name is Derek? Damn. Always thought his name was Veritasium.
Me when electromagnetic force disappear: Mr. Stark, I don't feel so good
That's what Thanos must have done to murder people. Disabling the electromagnetic force in certain places (intelligent creature's bodies) while simultaneously accelerating the expansion of space in those places.
My exact thoughts!!!!!
@@zyansheep Yeah, duh.
@@zyansheep space didn't expand there
Damn, I wanted to make the same joke, lol.
I appreciate you, dearly. I've recently been going through old videos of people like Feynman and Sagan. They existed at a time when video technology was still...amorphous. We only have so much video of them, and they died so long ago. I know they would be proud of creators and educators like you who are carrying on their work. Thank you.
U
Exactly👍👍
How far can a photon be stretched by space?
They are all spinning in their graves cause they were duped by a fallacious Myth. Had Saint Einstein known that objects accelerating in a common vector, the starts of their accelerations staggered by DELAY, exhibit observations of RED SHIFT made by observers amid the objects also accelerating at the same rate in the same common vector.... he would never have endorsed single-point expansion HALF theory ...
Had Saint Einstein known this, he would not have made the erroneous ASSUMPTION that red shift observations on galaxies implies expansion of space.
Sir Hubble REFUSED to endorse LeMaitre and Einstein's fallacy ... he KNEW their ASSUMPTION was flawed,
Space can not be bent stretched warped or folded because everywhere you'd like to bend stretch warp or fold it to, there space already exists, and the bending stretching warping or folding would result in space ^2 where space from one locale is imagined to meet space from another ... and THAT is total INSANITY.
your appreciation for the elaboration of falsehood is misplaced.
Don't worry guys, I love you guys too. I'm just not retarded... but believe whatever the hell you wanna believe in. This is kinda fun though not gonna lie. But I'd rather not just pretend my whole life to keep everyone else happy...
I'm sure we're all mad at God but come on. It's not his fault if no one listens to him...
Just live honestly and don't pretend like you're anything else. I've got geniune anxiety about people watching me overtime. It's weird and now that paranoia might be a reality... just please keep pretending like I'm not as embarrassing as everyone else...
God dammit.
ive seen 2 explanations before this one, and this one is by far the clearest, most well-suited for the average joe to understand. thank you.
Veritasium: "Do You Expand With the Universe?"
90% of the comments: _self depricating fat jokes_
Me: Our creativity sure isn't expanding.
Upvote number 111. This comment is underrated.
The irony is appreciated.
First time?
@@blank2588 朋友是一个坚韧不拔的纪录片， 在香港这座城市的设置。 主演：钱德勒 索罗斯 傅博斯1 瑞秋 莫妮卡 和一些其他他妈的演员。
Me: Especially with this incredibly overused format.
Lesson learned: Never go out in outer space without electromagnetic forces.
If you don’t have electromagnetic forces applying to you while you’re on earth you’re screwed too
😁😁😁
I would love to see a video on how it feels to go out that way
@@VvDiverDownvV Being de-moleculed? It would probably hurt after some point, depending on the rate of decay.
@@LambGoatSoup Well see I feel like everything at the same time would just float away sooo you wouldn't feel anything maybe? You'd just go instantly?
Incredible video, thanks a lot for taking the time and making the effort to make this.
I swear the title changed from "are you expanding with the universe" to " what actually expands in an expansing universe" and i think the thumbnail changed too. It's refreshing watching old veritasium videos. This video is actually one of my favorite veritasium's video, i think i watched this video at least 6 times
Me personally holding a degree of Masters in Physics, still this guy, with every video, brings out the attention to something which seemed to me very trivial in the first go but never gave a second thought, and blows my mind every single time. I don't know how Derek does it. Best youtube channel I've ever subscribed to.
Mind me asking your future plans after the M.Sc.??
Same here. I have a master's in physics as well and have thought many times that Derek would have been great at physics. He asks good questions and has the patience and ability to think through them logically.
@@mrbonzzai Well, he has a PhD in physics education research
@Science Revolution no the stars we see (with our naked eyes) are within the Milky Way galaxy and thus at most 100 k L.Y. away. The rest of your incomprehensive rambling I let somebody else to comment.
@Science Revolution shut up you're a tree
I'm not fat, i'm red shifted...
And the comment of the year goes to
10/10
best top comment i have ever seen lol
I'm sorry I don't speak red shifted.
Shock I identify as skinny, I’m trans-slender.
This is the best channel ever for your content I can only imagine how much research is required. Thanks a lot ❤️
No other content creator has the ability this guy has to be able to explain concepts to 14 year old me and then 6 years later help me understand another concept the day before a final year Undergrad Physics exam...different level
Man, I feel the same way but the diffrence is my age is on the younger side. I wish I could learn this for the rest of my life!
@@justanerdguy3054 Then go study Physics!!
@@beetlesstrengthandpower1890He said "wish", not "going to", because that means working on it, rather than just passively consuming media and forgetting about it the next day.
"Why's it red?"
"Because spacetime is expanding between us at an accelerating rate"
because salesforce!
what if the universe (being infinite in size) is not expanding and actually everything in it is shrinking, would we be able to tell the difference?
@@usuario2967 uhhh yeah i guess cause then the light from sun would take longer time to reach us and the time would continue to expand
Red was not the imposter
Blue sus, bcs i saw red kill... The expanding photon from my phonescreen explain how blue is suspicious
Oh man I have been wondering about this question for as long as I know everything expands
Really, my friend. I have been thinking about that same question for a while now.
What is happening is more space is being created. Now could this new space creation get to a point where it could eventually overcome all the forces holding things together? Maybe. The Big Rip theory suggests that the expansion could continue that far. But its too soon to say if that will happen. Dark energy grows over time? I think so but is it infinite or finite? If finite will the acceleration lessen and stop? Before the universe smears out into homegeniaty? I doubt I'll be around that long to find out. 😎😆
I did too and then I thought I found the answer in a Philip K. Dick story where a man time travels (sort of) and the people from like15,000 years ago are tiny since he would be more expanded. They think he is god and it turns out he gives them the 10 commandment or something. But now I'm mad because I told other people we expand since I thought it was true because of that story
I feel so lied to or something
There's nothing expanding besides the "metric".
Surely the laws of nature must apply to everything. That must mean that we are proof of the truth. Yes, aliens do exist and no, the universe is not expanding.
I've always wondered this! Thanks for explaining in such a clear way, this video made me so excited to finally understand
very interesting and thought provoking, makes me want to go learn physics to fully understand what I fully imagined just now.
Go for it 👍🤟
Little girl: "Why is it red?"
Derek's first thought: "It's red shifted!"
Hahaha
I don't get it
@@MarioAP At 11:21, you hear a little girl ask "why's it red?" when he turns the camera on.
Because blood rushed to it.
You may not be expanding, but your mind is
1:13 "Are you expanding with the universe"
Geez, I know I've gained _a little_ weight during quarantine, but still.
BAHAHAHAHAHA
HZBXBAHHSJEIRNTNJFIHTBTBEKFNBFBDJDHTBG I DONT KNOW WHY I FOUND THIS SO FUNNY
Woohoo I was hundredth like
Funny
Most people of my family lost weight this 7 months
What to say when someone tells you you're fat: No, I'm expanding with the Universe... lol
I want tô thank all of you that work on this channel for explaining that question. The first time I heard about the expansion of the universe I wondered about us being expanded as well. I could't find the explanation for this anywhere until I seen this video. That question literally gave me insomnia in the day I thought about It, now I can sleep 😅
This is wonderfully explained but awesome to take in - I will have to watch this many more times.
Consistent uploads with quality wow how's that even possible
A good team behind him
And prerecorded probably, definitely not complaining though :)
Scientists keep thinking and there are still things to discover
@@ajtan06 prerecorded?😂 To what? Xd
Sweet, sweet sponsorship income = more financial resources = more better content.
Me: *about to go to sleep*
RUclips (Veritasium): 'Do You Expand With The Universe?'
Me: _I don't need sleep, I need answers_
That's how it is sometimes. I'll be sound asleep by the time this video ends. Then I'll watch it when I wake up lul.
Haha that's good
Relatable haha also wanted to sleep but watched this vid instead x3
You need sleep too. (A friendly reminder to go to sleep if you haven't yet)
With videos this good I opt in to watch the ads for you. Thanks for the content
thank you for the amazing and high quality content of yours ... ♥♥♥
"The problem is if you give it a second thought"
Me: Yes, that is the source of all my anxieties
_Relatable_
@@noidea9952 Highly
Lmao same
hahaaa
Me: Let's spend 4 hour preparing for something that obviously won't happen cause it "might" happen
This whole "you're currently accelerating because of gravity" thing is still kind of making my head explode.
Also, you're killing it.
Well, kinda like when you jump, you're not being pulled back down by the earth directly, per se, your mass is just interacting with the earth's mass and you're sliding down the curved spacetime back to rest xD the earth is just much more massive so you think you're being pulled back down, but really, both masses are pulling on each other! Just the earth has a lot more mass to pull with xD
@@FractalNinja Yeah I get it conceptually, but intuitively "You are always currently accelerating up" seems like it cannot be true. It's one of those weird facts that is just a mind bender. I love it!
GDI Bass
I'm not sure how "up" could be the correct term considering there is no "direction" in space. The earth isn't pushing you "up", you are just along for the ride essentially.
Up is a relative term, so the absolute definition of it (especially when talking about an intuitive interpretation of a concept) isn't particularly relevant.
@@FractalNinja I think you should watch veritasium's video on gravity! He explains how gravity isn't actually a force there and when you're free-falling, the earth is basically crashing into you. Just like in this video, the free-falling oberserver was the same as the astronauts stationary in the universe looking at the rocket-ship - because they are essentially the same
"Are you expanding with the universe?". *Looks at belly*. "Why yes, yes I am"
I wish you discussed why we sometimes see blue-shift within the framework of an expanding Universe between all points.
Also, if we would expand if we could turn off the electromagnetic and nuclear forces that hold everything together then it makes sense that if we could turn off the expansion/dark matter then everything should move closer together at least a little bit. We would get denser. Everything's density ideally is more than what we currently measure. The difference is therefore the strength of the effect of dark matter.
Joke time: A man appears in the court for breaking traffic signal. The man argues that the red traffic light appeared green to him due to Doppler effect. The judge accepts his argument, cancels the charge of jumping traffic signal and instead fines him for crossing speed limit.
that never happened...
@@EXTENDEDWARRANT your sarcasm is bad
@@EXTENDEDWARRANT IT LITERALLY SAYS
"Joke time"
@@thefountainpendesk I know I’m just joshin
no one asked but...
assuming green λ = 540 and red λ 700...
v/c = Δλ / λ
= 540 - 700 / 700
= -0.2286...
v = -0.2286... x c
= -68523990.4 m/s
or 246686365.44 kph
That's 22.9% the speed of light... and he could travel around the equator in just over 2 seconds
11:23 "Why's it red?"
You're in a non-inertial frame of reference kid, where the earth's gravitational field is dominating your local space-time curvature.
The camera is also recording.
The Earth's gravitational field is negligible to the red-shifting. It is red, because the source moves away from the observer, and as a result of the Doppler effect, it decreases in frequency.
@@carultch I also watched the video. I was inferring that she hadn't, and she wanted the answer to cosmological redshift (-There I clarified the comment). Please understand that this is a joke.
Sir you are awesome .
I knewed about expansion and red shift but this video gave me a clear picture and visualisation .
Iam a class 11th student and love Physics.
I had that question for years. Thanka for the explanation
Proud of myself for understanding approximately 27% of what this video is talking about.
😂😂😂😂😂😂 i can relate to you
🤣 same here
i gave like for 1%
Well if that 27% is the Doppler effect then you understand 100% of the video
He's getting a lot of use out of that rocket.
Lol true😂
@@adeshpoz1167 it's all cool. His production team does a good job.
@@GregoryTorchia Derek must have also purchased that tower at Harvard, along with some distant galaxies.
SpaceX: Our 50th reflight of a booster!
Veritasium: Shows his rocket in many more videos
you are blind to TIME.
some good questions;
how long is it now or how long is it now?
Is time continuous?
What is the shortest time that can be measured?
To help with the answers consider the Planck constant
You are such a compelling and charismatic speaker
Derek, this video was very important. Thank you!
10:53 “Mr. Stark, I don’t feel so good”
:,D
Gud one
Underrated
Thats exactly what i thought!!! :D
so thats what thanos did
"What would the freefalling observer see"
the pavement, presumably.
Lol
Or his life flashing before his eyes.
Einstein cheering
@@dakinnie We tend to view the past with rose colored glasses, this is known as temporal red-shift.
He'd be known as Lil splat
Another great video. Thank you for making such great content. Namaste x
Very well explained!!! Thanks a lot :)
Did not understand a thing bit yes its all sound good to me
Then how can you have a valid opinion?
@@Sonex1542 when did i said he is right
I said it's sound good to me not by theory
Big difference bro
sometimes understanding... is about letting go and letting the force guide you 💁♀️
Don't worry, you are not alone
Don't try to understand it, feel it
In the difficult time of Corona, I am glad Derek provides us with videos more frequently. Life has become stagnant for me, and I feel like i'm getting dumber since there's so less to do and learn from during this time. These videos are a breath of relief for me and I really appreciate it. Thanks, Derek.
@Science Revolution This is a joke, is it not?
@Science Revolution I really, really hope this comment is satire
preachhh
@Science Revolution You know, there are answers to all those questions. But because you started your comment demeaning and insulting all other people and scientists, it tells me you are not really even interested about the answers and you are not willing to learn from them. Therefore I can't bother to explain those things to you. For everyone's sake, just leave the internet for a moment and read a book, or something.
@Science Revolution if u had asked the doubts without insulting the scientists then I would have happily cleared them
Someone needs to build a really good special relativity simulator to show the visceral look and feel of these spacetime transformations. I want to see how a ship's appearance would change as it passes by at semi-luminal speeds. I want to see how the colors would shift, lengths would contract, and time would slow down from each observer's perspective. Could you get on that?
How far can a photon be stretched by space?
@@reasonerenlightened2456 maybe microwave as we receive the electromagnetic radiation from CMB
@@reasonerenlightened2456There is no limit. Maybe energy reaches 0
There is this Vsause video that shows what will happen when you move at light speed so that's like 1 out of 4
I know this isn't new, but first time watching it and someone who knows this topic well - excellent presentation, graphics and storytelling!!!
All these videos make me realize is that Einstein is the GOAT. this dude found ONE EQUATION that all this is based around??? WILD.
He is one of the GOATS if not the GOAT. However, there is one more equation which describes as much of the universe, if not more and that is Schrodinger's equation.
Funny you say this in this video, cause Einstein was really against the idea of the unverse expanding for a long time before he was proven wrong.
zu wild
Runner-up. Newton is the true GOAT.
it wasn't just einstein, many scientists contributed and even corrected einstein
Derek really deserves Recognition for not being afraid to experiment in the Format of his Videos, he rather tries new things and tweaks his presentation with every project, not to mention the immense effort put into each video, it really shows!
He's really done a good job of making sure he doesn't get pigeonholed into a specific type of video.
long time viewer, thanks for the vast amounts of knowledge you brought to us during the years.
This video confused me tho, i was under the assumption that dark energy (given enough time due to the fact that the expansion is accelerating) will eventually rip stars planets and even molecules apart.
(ps. a video on dark energy will be very much appreciated :DD )
UNTIL SCIENTIST DEFINE QUANTUM GRAVITY THE WILL CREATE DARK WHATEVER? GRAVITY IS THE PROBLEM THEY CAN'T SOLVE.
i have a concern with this understanding of red shift. we have all learnt in early childhood, that each point in ray of light act as point source and send light everywhere. so the energy fo light keeps on decreasing as the light move forward as some of it is lost to create other light. isn't this the reason for red shift of light as red light contains less energy then other visible light.
Veritasium's animation team on another level. Along with the content, you guy are on a roll!! Thank you!
Also they got time for multiple thumbnails...
Dude you're pumping out videos in these times like crazy.
MAD respect.
I learn so much from this channel!!
This is a fantastic and accurate explanation. The only thing that is missing is explaining "g_00" the time time component of the metric tensor. Just looking at this component gives 99% of the predictions of General Relativity, as it reproduces Newtonian gravity. It's also the source of gravitational redshift, and it was worked out by Einstein in 1907-1909, long before the full theory.
"It's all doppler?"
"Always has been."
NetDoppler
Actually I also only knew that it was doppler everywhere.... Then at the beginning I'm like is the knowledge i process wrong? Then later I'm like no i was not 😂
*BANG!!!*
It all depends if you view life through a redshift or blueshift lens!
Same
D: Thanks for posting something I haven't seen repeated 1000 times on other pop-sci channels. This one was new to me.
Kings Disease album of the year btw
Same ish, just explained very well with animations. Good stuff
I hope you're not cynical. This is completely new to me and not explained in any other video I've seen (please share video here if i'm wrong. Anyway, this is explained heme amazingly and anything I can from a physics video. Very professional stuff Derek!
Wym the video was well made and this my first time seeing red shift explained like this. Don’t be thinking you are the only subscriber this guy makes vids for. 🤣
I'm sure he made it just for you.
Maybe I'm missing something but I always wondered about that light Doppler effect. Sound Doppler is easy since speed of sound relative to the source changes, that's why sound waves infront of an object are compressed and behind it expanded, hence incoming source has higher frequency than outgoing one. E.g. sound doesn't move at the same speed relative to any inertial frame as light does. So what's the underlying mechanism of the Doppler effect when it comes to light when the light moves at the same speed relative to any inertial frame including its source of course? E.g. the observers should have no means to tell how fast the source of light moves relative to them right?
Thank you for taking the time to explain very complex and interesting concepts!
Veritasium: are you expanding with the universe?
me after eating two entire bags of crisps: *i sure am*
ew
bri'ish "person" detected
@@devans.5324 "person" lmao
Alert, the Queen is on the loose
its been six months you need to keep up and have more crisps
“When the universe was very young, it was so hot...”
I'm going to stop you right there.
The girl named universe: *reports bruh moment*
“Help! I need an adult”
@@cyto3338 never speak again
Why don't you take a seat right over here...
Excuse me! I don't get this
Can anyone xplain?
Another superior explanation of a misconception that you do so well.
Love this channel…absolute crazy how I think crazy things and then hope somebody would have explained more or dig deeper and provide more insights
And Bammmm…Verisatiun have video on it! Love❤️
5:30 - As I'm falling to my death, I'm going to be concerned with the color of a photon in a gravity tube.
Lol
This comment is underrated
But the fall doesn't hurt just the landing.
Welcome to theoretical physics
😂
I'm happy that Derek is uploading frequently.
I'm unhappy that I can't grasp any of these .
I end up watching them multiple times to try to understand it 😂
It's all shadeballs?
Always has been
El stupido
This got nothing to do with the video but I just got an ad in this video for no man's sky with the song retreat retreat by 65 Days of static.
Really made me happy to hear that song again.
I have some questions about the "big bang".
(genuinely interested in answers, not to argue).
1. When we look at distant galaxies that we say are "further back in time" due to how far away they are, and then we are told that these distant universes are "older" meaning the light we receive from them took so long to get to us from there that we can literally see back in time to the big bang. How is it that we can apparently see back to the origins of the big bang? If everything is expanding outward, and space itself is expanding (carrying us with it) faster than the speed of light, how is light then able to reach us from back in time when the big bang happened?
2. It is said that the big bang didn't happen in a "location" in space, but then I hear the same people also say that everything was once contained at a single infinite "point" prior to the big bang and then "BANG" everything that was contained in that single point is now shooting through space at incredible speeds and even space itself is expanding outward... Why do physicists say everything was once contained in a "single point"? How is it possible for a "point" to exist if spacetime itself was contained within that point?
3. Why do physicists say that the distant galaxies we see are "old" in the sense that they represent a time closer to the origin of the big bang? I understand the concept that the light we see from distant galaxies takes a very very long time to reach us, which means the light we are seeing is what that galaxy was like when the light first started traveling toward us, but how does this mean that the "old" galaxy we see has anything to do with the origins of the big bang, and how could we possibly measure how close that is to the origins of the big bang?
4. If we are moving with space at a greater speed than light (because of space itself expanding) this means that there are galaxies moving away from us that we will never see because the light will never reach us unless we one day learn to fold space ourselves, so we can't measure how vast space is exactly. Heck, some say space is infinite. How could we ever possibly know the origins of the big bang if we can't measure space?
5. How could we possibly tell that "the universe" is expanding "outward" if we can't actually measure the size of the universe in its entirety? Is it not just as likely that space (if its finite) outside of our observable universe is trillions of times bigger than our current observable universe and as a whole isn't actually expanding outward, and what we see isn't the whole story? For example, I could observe the atmosphere here in Australia and I could theoretically (with enough data) predict how the weather is going to behave long into the future, but if my observations were confined to the atmosphere within/above(?) Australia only, and I could not observe the outside world, It is not possible to predict the weather long into the future because it is only a small part of what is happening on a larger scale. Is it possible that the expansion of our current observable universe is just a small part of what is actually happening on a much larger scale outside of what we can currently observe? Isn't it just as likely that galaxies outside of where we can currently observe could actually be expanding through space toward us, as the "Big Freeze" theory that we will just continue expanding outward and eventually just fade into darkness?
Your first mistake is asking questions. Your second mistake is expecting a reply.
There are millions of holes in the current cosmological dogma, and everytime a new hole is found, they plug in some mysterious new entity to plug the gap, and keep the funding coming.
It’s all b.s.
@OP I'm a complete noob and I'm gonna be very handwave-y for much of this but I'll try to give my understanding of things. Also note that this is all scientific theory - the thing that makes the scientists believe they are "true" is that they describe, explain, and predict reality as witnessed by us. As seen many times in the past, as soon as there is something we can't explain with our model, we look for a better one - none of this is known "for certain" (whatever that would mean).
(1) Space would've been expanding faster than the speed of light only for pairs of points that are sufficiently distant from one another. The Earth and the Sun, for example, are also objects in the expanding space, but they aren't moving away from each other faster than the speed of light (clearly, we can see the light from the Sun). As for "going back in time", we can see a distant object that - some time after the Big Bang - would've been moving away from us quickly, but not at the speed of light, that's why the light still reached us.
(2) The theoretical origin of the universe, or the "Big Bang" - just says that the space is, and has been, expanding. The natural extension of that when you go backwards in time is that it started from a single point (or "singularity"). And, essentially, the entire Universe was then contained in that point - it was just "smaller" relative to the speed of light. That's why it's said that it was both "all of space" and "a single point". And, in particular, we can see evidence that "a lot time ago" the universe was very hot and very dense.
(3) There are two possible radius you can draw from yourself towards the "edge of space". One edge contains the furthest (and the oldest) stuff that we can see right now (Visible Universe). The other one, outer to the first one, contains the furthest and the oldest) stuff that we will EVER be able to see (Observable Universe, ). We will still be able to see it (maybe in a few billion years) because the light from it has been travelling towards us since the Big Bang, and it's been moving towards us faster than the Universe is expanding. Once these two "edges of space" meet (again, in a few billion years), we will be able to see that "stuff" as it was at the time of the Big Bang. And after that, assuming the Universe keeps expanding, it will disappear (behind the edge of the Visible Universe), and we won't be able to ever see it again.
As to answer your actual question - the way we calculated "when" the Big Bang happened, as far as I'm aware, is observe/assume some pattern in how the Universe has been expanding, and calculate how long it would've taken some distant objects to "expand away" from the point where we currently are.
(4) Yeah, this is correct, some points are moving away from each other above the speed of light due to the Universe expanding. But they weren't always. At the very beginning (for some time after the Big Bang), the entire Universe would've been observable.
(5) The reason why we model the Observable Universe as "expanding outward" is because some of the stuff we can see is moving away from each other (again, as measured by the speed of light, which is fixed to be constant). So, at least "for the time being" it looks like stuff is moving away from each other. But it's entirely possible that this changes, or isn't the whole picture. And the different examples that you mentioned are I believe examples of "possible models of the expanding universe" which theorize that e.g. the Universe starts contracting at some point, eventually going back to a single point again (Big Crunch). This would also, as far as I understand, make the entire Universe (eventually) Observable. The reason why these theories are mostly discarded nowadays is that we can't see anything that we think would reverse the current (visible) expansion of the Universe.
PS: I really liked Veritasium's recent video on "Einstein's Math" and the theory that our Universe is a White Hole (the "Big Bang" being the singularity).
Probably, dunno honestly
maybe
Papa flammy
Fancy seein' you here oh great and wise giga brain MENSA member!
Papa flammy!!!
I have a question: Why would light wavelengths look redder (lower frequency) if time slows down the faster you go? In the rocket thought experiment, those in the rocket with their time slowed down, should perceive the light as a shorter wavelength.
This example helped me : You can tell the difference of sound made by a car moving towards you or getting away ; while the driver of the car hears the same pitch . If everyone tries to measure the wavelength ; It would be different .
I still have a little problem relating this to universe level . ..but ...
Thanks. Great example, don’t know why I didn’t think of it like that. Really helps me imagine what’s happening. Omg.... just realised this also helps me understand spacetime better as well! & how different observers can experience time differently. Many thanks! 🤯
And if the car is all red, it's driving away real fast
@@alex0589 And if it's blue, it's coming to you
@Science Revolution 1. Yes it's a star we can see. No, it doesn't have strong enough gravity; it's not dense enough yet.
2. Scientists don't, duh. The most recent picture of a black hole has a massive black spot in the middle. There's a reason for that.
The light that we see is from the accretion disk, where space is moving with the black hole and objects are crashing into each other. Some light escapes from there.
Also, the mechanism is explained with general relativity. Evidently you don't know what a black hole is.
Gravity doesn't "decelerate the light speed;" it curves spacetime. _Time_ is included. The event horizon actually makes it so the light's possible futures all end up within the black hole. We don't know exactly what happens after that, though.
3. The curvature of spacetime is brought about by a big enough mass. We talk about "gravity," but we actually mean curved spacetime.
In some models of physics, such as Newtonian mechanics, gravity is a force pushing things down, and that works as a good enough approximation for most uses.
If you really want to complain about science, complain about string theory or something.
@@alex0589 Now imagine you're in the car. No traffic light would show red to you from a certain speed.
7:28
I never quite understand this part. If the motion of earth is well-defined relatively to the cosmic background radiation, then does it mean that the universe has a preferred reference frame in terms of velocity?
I understand that the law of physics is invariant under boost (of reference frame), but does the (initial) state of the universe have a special frame where net momentum is zero?... and that determines the doppler shift of CMB?
This is an excellent question. We often say there is no preferred reference frame of the universe, even though the CMB seems to provide an excellent counter-point to that. The CMB is the furthest "object" that we can see back in time, and we can measure its Doppler shift via a special relativistic effect called beaming. Since we are moving at 600 km/s through space relative to the CMB, we see portion moving towards us as being blueshifted and beamed to a higher brightness, while the portion moving away from us is redshifted and similarly is dimmer. Based on the amount of beaming we see, we are able to determine our relative motion (to within some uncertainty of a few 10s of km/s).
Because of this, it is somewhat fair to say that the observable universe does have a preferred reference frame in terms of velocity, however the universe itself still does not, as we still cannot define the CMB's relative motion to objects outside of the observable universe. Additionally, this preferred reference frame would be different depending on where in the universe you are, as our preferred reference frame (the observed CMB) would be much different than what someone at the other end of the universe 15 Gpc away would see as their microwave background radiation.
The initial state of the universe did not have a special frame where the net momentum was zero. The universe was expanding back then just as it is now (even more so during the period of inflation), and as a result no such reference frame could exist as far as I know.
Good point.
This one was deep. Congratulations!
When the world needed him the most
He became more frequent
what the hell! this man is making quality videos on almost weekly basis now. these videos are much better than documentaries on these topics! Keep up the great work!!
Best youtube channel... hands down.
As usual, fantastic.
I may not expand with universe but has expanded like never before in this lockdown.
faster than the universe's expansion? MIND BLOWN
*have 😉
Loving seeing more videos from Derek recently. The quality and quantity had increased, and I have no idea why but I love it.
I just hope he doesn't burn himself out.
I read his comment that he has a team, cmiiw
That sponsor money getting put to use
This is the phrase I heard today
He made a community post where he said he has a team now.
Yes we are changing and that's why time
Is non incremental and time and location is stored in each partical as it exspands. Compression sends particles back in time expansion sends them forwards in time it also changes their position from where they used to be to where they're going to be
Awesome video, very explanatory.
My brain just expanded from watching this.
I really enjoy your content 🙂❤️
I personally think the gravitation shift makes the most sense. Imagine a fog of non-luminescent celestial objects spanning the void of space each deforming the gravitation field around them like a little divot on an otherwise smooth piece of paper. As light travels through this torrential textured space time, it red shifts. This would also explain why objects more distant have a greater redshift than objects closer to us, which would otherwise make no sense.
I laughed at 5:35
I'm imagining a hospitalised student visited by his friend after sustaining various injuries from his free fall and the friend asks him "What colour was the photon?" to which he responds "Piss off, mate!".
Well of course, it's not the fall that hurts you -- it's that sudden stop at the end!
you british , bro ?
@@Milesco
Nerf gravity.
@@Milesco ehh doesn't that mean that you'll get hurt by stuff like bungee jumping lol
@@psc698 : No, it means you *_won't_* get hurt by bungee jumping! (Unless the cord breaks! 😁)
Derek can you help me understand a thought experiment I've had.
If you look through a telescope at a planet very far away and can see the surface. Let's assume there is life on the planet and this telescope is powerful enough to see down to the street level so you can see people living their lives. Now this planet is 1000 light years away so you see the people as they were a 1000 years ago.
Ok so far so good
Now, suppose you take the telescope on a rocket and keep looking at the planet as you travel towards the planet at some very fast speed. Let's assume 0.5c.
What I can't understand is this...
Do the people as viewed through the telescope appear to move more quickly?
I've had this thought experiment in my head for over 15 years and can't figure out what would happen. My instincts say the people should appear to move more quickly as you travel towards them but then this breaks the idea of relativity and light being the same speed no matter where you measure it.
But then, if they move at the same speed as you travel towards them at some point you would reach the planet but through the telescope would still appear older and that's not true either.
Maybe an idea for a video in the future?
They should appear to move more quickly, I don't think this violates relativity. I think this is the same as when you hypothetically orbit around the Earth at ludicrous speeds and come back a year later -- only to find that the year on Earth is far far in the future while you have aged only one year
Great now I have another huge question to think about for years!! Haha really though, cool thought!!
What do you mean by saying that it will break relativity ? The light would still move at the same speed, its just that you would be moving into it, which means that your eyes will receive more of it.
I wouldn’t say it violates relativity. The light coming towards you doesn’t move any faster, but you see more of it. They’d appear brighter and faster.
This is like the opposite of that Einstein thought experiment where if you were to move away from a clock at an ever increasing speed, as you approached the speed of light the clock would appear to slow down and at the speed of light it would appear stop moving. www.emc2-explained.info/The-Light-Clock/
@Veritasium The only issue I have with this vid is that cosmologists in fact do NOT agree that the universe is homogeneous or isotropic. Since about 2013, with Planck Satellite data, scientists see that the universe strangely seems to "prefer" a direction. To add insult to injury, that direction aligns with our tiny earth and sun. Dr. Lior Shamir, just this month published about this in the paper "Large-Scale Asymmetry in the Distribution of Galaxy Spin Directions-Analysis and Reproduction."
We know that light sources moving to/away from us can cause doppler shift in the wavelength of the light they produce, but does a moving observer also perceive a doppler shift because of his own movement?
I mean if a star's light is shifted to a wavelength λ because of the star speed, if it doesn't get shifted further during travel (ie ignoring cosmic expansion red-shift for now) then we would assume it would arrive at the observer with wavelength λ.
But if the observer is also moving with considerable speed relative to that light source, then would he detect additional red/blue shift on the moving detector?
I was thinking about the setup of the experiment at 7:56, for a single photon the only way to observe it and pass it further is to absorb it, measuring its properties and generate new photon with the same properties. Is such case every observer on the chain would be new light-source, which we know can shift additionally the wavelength because of its relative speed.
But if you consider a beam of light, and after all stars are radiating light in all directions, ie given beam of light would spread wider as it travels further, which means that a detector can be setup to intercept only a small fraction of it, while the rest of the beam is left untouched by measurement, and doesn't need to be re-emitted.
So at every observer in the chain we can take a small sample of light to measure the light properties (assuming they're mostly homogeneous with the rest of the light in that beam), and let the rest of the beam travel with its wavelength untouched since its original light-source.
I assume when the last observer takes a sample and compares with the light that was re-emitted by every other observer on the chain, its wavelength should be the same.
And I assume the only factors for a doppler shift of a wavelength are both speeds of the light-source and of the observer. Expansion of the spacetime just affects these speeds.
So the actual red-blue shift only happen on emission and on detection of photons, right?
I mean that if I'm observer on a planet moving away from the star I'm observing because of the Cosmic expansion I'll detect a red-shift.
But if I'm moving at a speed that allows me to keep the same distance with the observed star (ie relative speed to the star is 0) I wouldn't detect a red-shift at all (no matter if you consider the light red-shifted at the star, and then blue-shifted the exact same amount on detection because of my speed)
Is that right?
"Are you expanding with the universe?"
Yes I am, sideways. Or maybe I eat too much...no definitely the Universe
It's a consequence of your expansion being coupled to the earth, and the Earth therefore being the mechanism of expansion. Expansion radially from the centre is ruled linearly by 'r', but expansion perpendicular to that is ruled by the surface area of the Earth, which is in a square relationship to 'r'. Hence we expand proportionately quicker in the pseduo-plane parallel to the surface of the Earth.
(Disclaimer: this is a joke. Feel free to pretend to take it seriously and continue the joke, but the logic is deliberately utterly wrong.)
Spongebob giving Patrick heasld, wtf XD
@@nialltracey2599 Wow I've never thought of it like that 🧐🧐
10:53 - I don't feel so good Mr. Stark
I was looking for this comment
I think the problem is that when we hear/talk about expanding space, we tend to think of space-time as sort of stretchy trampoline that can change shape, while (at least in my understanding) it's just that when you go at large enough scale where forces like gravity and dark energy are no longer dominant, things are getting further and further apart. The universe is expanding, spacetime isn't, but we misleadingly talk about "expanding space" like it's something flexible
well , according to what I've read or heard,
1. gravity is not a "force" exactly, (Veritasium has a video on gravity you should check it out)
2. the word "gravity" usually ONLY refers to the gravitational field of the Earth
3. There's nowhere in the universe dark energy isn't dominant
but I agree with the last line u said, spacetime isn't expanding, universe might be.
Actually that's what I thought first, that the stars and galaxies were just moving away from each other. But then, a question arises: Moving into what? The reality is that space itself is expanding and by doing so places things farther and farther apart from each other. And not only that, because it is expanding everywhere it accelerates things in opposite directions. Veritasium explanation is that while this happens things themselves don't expand, they are just placed farther and farther apart from each other. If everything expanded we wouldn't notice any change, would we?
@@ricardojsgw My understanding was that they are moving into the newly created space that is formed every instant uniformly in all directions, for some unknown reasons
@@architanaik1420 In response to your comment:
1) You're correct. It's a "virtual" force of sorts
2) Yeah, you're correct about that too (I should've said "gravitational attraction")
3) If that were true, "small"-scale systems like our own solar neighborhood wouldn't exist right? The whole point is that dark energy is dominant at scales where gravitational attraction (caused by the curvature of space-time) is not (for example, it seems to be holding galaxies together). I'd love to stand corrected though
Felt like an episode of PBS Spacetime. Love both channels
"And what about you? Are you expanding with the universe?"
*me eating my 3rd box of pizza*
I probably am
OMG ALL THESE UPLOADS! and of such quality! You’re on fire! Thanks for the awesome content, keep up the great work.
Can’t get over how interesting all the topics you cover on this channel
ok, this is not easy to understand for people but I will try to show you... := means assigned a value
for t:= 0 to 100 do (our time interval) Universal clock age of the universe.
for k:= 0 to 100 do (our increasing or decreasing size) (gravity well)
for j:= 0 to 100 do (where is it in its height)
for i:= 0 to 100 do (which pixel is it in its width)
for L:= 0 to 100 do (which pixel is it in depth) so now do what?
So lets move the object sideways while it expands we have our coordinates x,y,z, we will say they all are starting at 0,0,0 front left top corner of our screen so x+i + some amount to move to the right m.
Lets add blue shift and put the camera on the other side of the box.
pixel(x+i+m,y+j,z+l) is equal to a color from a photo that will skin this box and we will add some blue on the right side and so for each L increment we are adding a bit of blue to r,g,b the pixel color.
and we are removing a bit of red. Adding because the camera is on the other side of the box facing us.
Does k matter? Will the box get larger when you look through the camera? No the camera is also getting larger. So why does it matter? Depending on how close to the sun or Jupiter it matters in the real world.
So for each tick of t, we clear the screen, then we draw the box, we have to resize our skin photo(s) to fit the planes on the sides top bottom, while we transfer pixels from the photo to the right side we add the blue light gradient towards the camera. Can you see a situation where k matters? Of course.
Light bends the closer to a massive object, the camera might be near jupiter the box near the sun.
3D no glasses a present for you since you are doing such a good job. No need to wear glasses adjust the pixel color. CGI can easily be 3D no glasses. See 3D no glasses chalk drawing on road blue cliff in road google images.
So to answer your question, one universe big bang, one big bang, did all of it explode? Yes all on the same clock? Its your clock you are using doing your experiment. You just cleared the screen every t and took your measurements ipso facto all expanding at the same time. A ruler painted onto a balloon.
t is a dimension because it will tick you cannot stop it. k is a dimension because it will expand you cannot stop it. j,i,L are 3 spacial dimensions.
PBS Space Time did an episode on this (couldn't find the link) and Matt says that space between the galaxies is expanding but space within galaxies is not. Its not only due to gravitational pull but also because gravity affects time itself. So although the expansion flings galaxies away from us, from what i could gather, it will never blow apart solar systems for example, especially not those inside a galaxy.
Always, Derek always finds a relatable way of explaining things, and always takes an interesting topic, people like u r the real ppl quenching our curiosity
I feel like he's actually a Physics teacher that likes his job. :D
It's because he spells Derek with an "erek". They are the best types of Derek.
Tere se pucha kisi ne भो sadi के जो gyan चोद raha hain yahan
@@yoyomodiji Sorry, Google can't translate you. Maybe someone else can understand.
Veritasium keeps making videos on questions I've wanted answers to but haven't had time to look deeply enough, great job!
My suggestions for future topics: What are the cosmic requirements for life; What's the window for life in universes life span? Something about amino acids in space vs on earth vs theoretically possible ones...
How would life appear to us/our equipment if we were to approach such planet at near lightspeed, could we theoretically see a timelapse of their history as we approach? How feasible would it be to build a forward "time capsule" on earth's orbit, a vessel that goes around earth at high % of speed of light and hosts a person?
...What's the opposite of lightspeed, i.e can something be truly static? Is difference between universe and not universe whether something "can be static"?
Ok, I might've gotten carried away, but there's some good topics in there!
If something went around earth incredibly fast it would be flung out of orbit
Also what is your profile pic
@@enderman5423 Yeah, I guess that's true. Maybe something like a long orbiting structure with passenger on one end and a counterweight at the other, putting the rotation pivot at the centre. Then just spin that really fast.
My pic is a wooden owl statue.
@@z3dar According to Einstein, there’s no such thing as static. Everything is moving relative to something else
Beware. Easy answers to hard questions are almost invariably wrong. There is misinformation in this video, and others of his. But most of the viewers can't tell the difference, they seem to uncritically assume that he's correct.
As an object gets closer and closer to the speed of light it appears to the observer to contract. Is it possible that photons simply appear to become stretched the further they go because they are slowing down?
In other words is it possible that red light is just going slower than blue light?
11:05 After watching this, I think the more accurate thing to say is molecules are expanding very slightly, instead of not at all.
Seems like a long roundabout way of saying “No, because the forces on your body are more affected by electromagnetism than dark energy.”
Are you expanding?
No, because scale.
Why does scale matter?
Ten minute video.
That's what I don't get though. If red shifting happens along any given distance then it should also happen at subatomic distances which would prove that universe is expanding at any scale, but by such a small amount it isn't noticeable on small distances.
@@gabrielrej834 We really should just call dark energy “anti-gravity”. It’s a repulsive force or pseudo-force that dominates anywhere the other forces do not. In the presence of dense matter, gravity is sufficient to nullify expansion, and gravity is far weaker than electromagnetism. On large enough scales, matter is diffuse, so dark energy rules. The anti-gravity effect is present at small scales, but gravity and electromagnetism counter it locally.
@@ryantwombly720 Anti-gravity insinuates a force that straightens spacetime, whereas dark energy pushes things through it. It also insinuates that we, without gravity, would expand like a balloon (the opposite of gravity which pulls things together), but in reality we expand like a dot drawn on the surface of a balloon. We don't expand away from our centers, but rather the center of the universe. Lastly, dark energy is, at the moment, a hidden variable. The universe is expanding faster than we calculated is possible, the amount by which we call dark energy. Calling it anti-gravity insinuates that we have a working model with a named force, but at the moment, it's just energy we add to our equations to make them are accurate, hence dark (unknown) energy.
@@ryantwombly720 -- It's not like anti-gravity in a couple of important ways:
1) Its strength has nothing to do with the amount of matter present in a given region. A cubic meter of space will expand to 8 cubic meters in the same amount of time, regardless of how much matter is present in it.
2) Its strength is directly proportional to the distance between two point-like objects, rather than _inversely_ proportional to the _squared_ distance between them.