"it's just how far back our knowledge of the Universe goes" - thank you for saying that, you are the first person I have heard to say that instead of the universe is x amount of years old.
stevemonkey6666 😳 Indeed, but saying ‘how far’ implies some form of distance or extent of existence. Using mathematical extrapolation we now consider the existence of the known universe to be 13+ billion years old and still ‘growing up’ . . . !
I mean, the age of our universe is AT LEAST 13.8 billion years old. Back when I was a kid, it was 7-20 billion years old, but now there is a study implying its possibly 26.7 billion year old. Personally, I am quite skeptical on that. We know for a fact that certain processes take less time and I am fairly certain our limit is at 16 billion years old. As that study for the 27 billion year old universe is mainly looking at stars that theoretically could have formed within less time thanks to some quantum shenannigans or theoretically could have survived a big crunch.
I was letting the video play while typing a clever bit about how time dilation in a massive early universe makes the 13.8 billion number nonsensical when just before I finished in the last 30 seconds of the video he said basically that sort of thing. Drats. I was looking forward to typing something clever today.
I love how the "nerdy" version of yourself also works to prevent people from being pedantic in the comments hahaha There's always the smarty ones that just overcomplicate stuff by being way too picky about details I'm pretty sure you do it on purpose too, but I won't tell anyone! Love your stuff!
War Oliv 😖 Hm! ‘smarty ones too picky about details’ . . . ? Remember what happened to Apollo 13, and how ‘smarty ones’ who were ‘very picky’ about details brought the three astronauts back safely to Earth? Those forensic scientists who examine the minutest details in an investigation? Are they ‘nerdy’ in your esteemed (?) opinion? Really!
Do you even understand in what context I said that? This is a science channel that tries explaining science in a way that most people can understand. Trying to simplify a bit while still being accurate IS the point of the channel. That's why he doesn't use too much math, so almost everyone can understand what he's talking about. Context mate, the example you gave is completely different from the point of these amazing videos. Overly detailing stuff isn't bad, in fact it's good. Not in this case though, since he's trying to teach in a way people will understand and stick around, instead of closing video because it is filled with advanced math.
as an engineering student halfway through my curriculum, that simple diagram of the stress energy tensor colored like that just made tensors click for me, so thanks!
I will avoid the math you 'kind of glazed over' but do wish to thank, thank, thank you for all of your excellent work. Specifically that whole "data vs. results" subplot was HILARIOUS in this episode. 10 out of 10!
I was sceptical when I first came across this channel, but now I really appreciate the content for what it is - science and simple explanations. I guess I'm a little crazy now...
"Gravity isn't about mass, it's about energy." Thanks for this. Why can't textbooks just come out and say this? It'd clear up a lot of confusion about photons being massless.
This video, by itself ,deserved an award. You're the best, those who dont know about this channel are missing out on so much. Thanks for answering the biggest query I had eversince I started pondering about astronomy. Thanks a lot sir.
This is my favorite answer to this question. We don’t know for sure, this is just how far back the knowledge of the universe goes. Perfect. Another great video! Please don’t ever get rid of that pet monster!!
The Science Asylum My brother and I got them when he was 4 and I was 8. We used to practice pile drivers on him. We gave my brother’s a short hair cut to tell them apart.
Love your videos. I have a few suggestions for when a clone pops into frame: A. Don't have your actors facing each other directly. Have them point slightly towards us, as it seems to invite the viewer in to the conversation. If they are directly opposing it makes us feel awkward. B. Another idea is to not have a cut at all. Keep your "you" self in frame and have your clone step into frame and ask a question or contest, and step away. Less jarring and slightly more believable without a sudden perspective change.
I appreciate the information you provide, hard to believe, but this kind of information and the way it is explained are not found on other channels. I shake your hand, with respect ! I will share links to your videos everywhere I can, hopefully this will increase the subscribers (1M+) and help you deliver great content like this for as long as possible.
As Einstein said "If you can't explain it simply, you don't understand it well enough" and u make everything simple. please do video on spacetime, if space is expanding so we have to consider time is also expanding but we dont experience time expansion.
Hi Nick. Absolutely love your videos. You are incredible at making very complex subjects understandable to the layman. Been watching through them now from your first to whatever the latest is. Thanks 😊
when using telescopes to "see the past" how do we know that the conditions and constants of the universe used to be as they are today and that we can even do those extrapolations into the past? how can we rule out other possibilities or the influence of things/processes we can't see today?
the stuff we can see with telescopes is relatively mundane ie. matches the predictions. We rule out other weird possibilities via occam's razor - it's simply more likely that our knowledge about the universe today (and near past) extrapolates into the further past, than the possibility that it just happens to look that way.
Just to add to what KohuGaly said, we do sometimes find that something we thought was constant isn't constant. The "Hubble constant" is a good example, which is why we renamed it the "Hubble parameter."
You are so brilliant Sir.If you ever decided to come to my country please make it public .I will at least come to get a glimpse of you .Wishes from Srilanka (South ,,Asia)
I was unaware just how much our understanding of time broke down in the first phase of the universe (I knew that questions about what happened before the big bang suffered from this). I took the "age of the "universe" figures quite literally. Thank you for helping to clarify that.
@@zerocool4835 Space time is great and I am a regular viewer, great to meet a fellow fan. Also really loved Infinite Series (a pity that the show couldn't live up to its name). I understood that at the very beginning our understanding of time breaks down at t == 0 (in the same way that the meaning of north and south breaks down at the poles). However, what this video managed to get me to see is that our understanding is still very limited the early stages of the universe for t > 0. This is qualitatively different from our understanding breaking down at the singularity (north is still perfectly meaningful until you reach the north pole).
Well this makes me feel old, back when I was in college the astronomy lecturer said that the universe was only 13.6 billion years old, how the time flies.
No one ever saw earth core yet we can still know stuff about it. (I suppose you could say that is also speculation but if you go with that logic to extreme everything is only a speculation.)
Yes we speculate stuff about earth's core too, and it is only few thousand kilometers beneath us and there are some observations to be able to speculate about it. What observations do we have to support all the speculations about black holes?
I've got a question You said that all frames are equal in every way and no frame gets a priority over another And also according to Maxwell;all accelerated charged bodies emit radiation. But in the frame of the charged body;it appears to be at rest with respect to itself.Then in this situation; how would it emit radiation???
I've got another question on Einstein's photoelectric equation It states that E(of photon)= work function+kinetic energy of electron. Now work function is in a way binding energy of the free electron which is equal to KE + PE and it implies that it is frame dependent And also the KE of the ejected electrons is also frame dependent The photoelectric equation turns out to be Frame independent(E of photon)=Frame dependent+frame dependent How is this possible??And where is the mistake???
1) I mean that accelerating charges _don't always_ emit light. 2) The flaw in your logic is the energy of a photon is _most definitely_ frame dependent.
only last part i got it.... other things i don't, but i like watching/listening/both things i don't know, especially if someone can make it interesting...
Thanks! According to some TH-cam cosmologists the age of the universe is 13.8 billion years. They claim that they know what happened before from conception to the first data. But whatever, good video. I need to watch it a few times on slow speed, though. It goes too fast for me (again).
1:07... A very interesting idea. How to you make your clones behave differentially? It is psychological or it is genetic? And how are you making them in the first place? We deserve some answers after so many time!
Quantum mechanics prevents _exact_ copies, so they always come out a little different. ( I gave a teaser of my cloning machine here: th-cam.com/video/a9T26ItpcDA/w-d-xo.htmlm21s )
The Science Asylum Just do your best. I think only uploading once or twice a month might actually work to your benefit. Less frequent uploads make each one more exciting. I've noticed lately that I'm more likely to watch a video soon after its uploaded if it's from a channel that uploads less frequently. Keep doing what you're doing. 🙂
Could anything considered to be void of energy also timeless? Can timeless objects be also considered matter? If this question isn't worth anyone's time, does it mean it doesn't matter?
PLEASE CAN YOU DO VIDEOS ON-1.WHY INTERNAL CONSTITUENTS OF A SYSTEM CANT AFFECT IT EXTERNALLY?( ie a person inside a box cant cause the box to move by hitting against the wall of the box from inside...I think this is also reason why emdrive cant work)2.WHY WE NEED FORCE CARRIER PARTICLES TO DESCRIBE FORCE?3.CAN WE EVER CHANGE THE LAWS OF PHYSICS INTO WHAT WE LIKE?
I love this video. I never say the universe is 13.8 billion years old. I always clarify that based on our knowledge, the universe is roughly that age. I always make sure to state that our knowledge is limited at best, and even based on that, we only use rough estimates to get the 13.8 b
Is there any estimate of how big/small the universe was during the Electroweak Epoch? Could all that energy condensed in a small region affect the perception/measurement of time?
There is one thing that I can't get may head around. It is the fact that time "ticks" more slowly when you measure it close to some heavy body. But in the early universe when there was primordial soup of quarks and gluons the energy density was enormous so shouldn't it slow time flow. I mean that during first Universe epochs the time was running extremely slowly... how do we take it under calculation during while calculating 13,8???
In case of two clocks, one close to a heavy body, one far away, you can keep them there for a while, then bring together and compare what they clocked. So when you see one ticked less, you can say it ticked slower. But in case of early universe we have nothing to compare with, so any amount of seconds that ticked there is all there is, there is no clock that ran faster and we could compare to. It's like watching TV series. We can say "this show has 400 episodes now, and that particular thing happened 321 episodes ago". Even if some episodes were released daily and some others once a month, if you don't have that external clock and can only talk about episodes numbers, if you only measure time in episodes this relative time rate is unobservable and doesn't change anything inside the TV series.
How can we calculate the age of the Universe by reversing expansion when we only know the size of the observable universe, couldn’t the actual size of the universe be 10 or 100 times bigger? In other words How can we calculate the age of the Universe by reversing expansion when for d=distance you are using the farthest “observable” star or galaxy, couldn’t there be galaxies 10 or 100 times farther away whose light has not reached us yet or never can reach us?
1: Was there more than 1 image of the CMB taken? 2: In an ever expanding observable universe and the CMB sitting on the observable universe horizon, wouldn't the CMB image change due to it's movement away from us?
1. The image I show in my videos is a composite image made from multiple smaller images. It was made in 2015 and is the most detailed version made so far. There were less detailed version made previously. 2. The CMB is emitted by matter and that matter does move away from us as the universe expands. However, the CMB light itself is _not_ expanding away from us. It stretched out during the trip though, which is why it's microwave light now. It used to be visible. (You're on the right train of thought though with motion affecting the way we perceive the light. The motion of Earth around the Sun, the Sun around the galactic center, and the galaxy through space all affect the measurements of the CMB. Those have to be removed from the data before we get that image I'm showing.)
Hey Nick! I would love to see you create a video about particle interactions inside the nucleus of an atom and, more specifically, the strong nuclear force. What governs it? Also, why are neutrons so unstable outside of the nucleus but not once inside? Love your videos and keep up your great work!
During reflection of image, how does photon show the object as an image in the mirror?? Is it like photon I carrying information about that object and projecting it into the mirror to form the image?? Also how does photon reflect off from the mirror?? If it reflects the same direction it was incident, does that mean it had to come at rest and reaccelerate in that reflected direction??
The photon doesn't carry information about the object. It just comes at our eyes from a specific location on the mirror, which depends on what part of the object it came from. If enough photons reflect off the mirror, the whole collection of them form an image. (A photon ceases to exist at the mirror and a new photon is created that travels along the new path.)
Yes..but for a photon to show ones image, shouldn't it first come from object and strike the mirror.... I was focusing on the fact that a photon comming from a table and entering our eyes will show us the table. A photon from sun will show us the sun..so different photon comming from different thing provide us with visual information of that thing. So visual information must be carried by photon. If an electron were to come from a surface and enter our eyes, it ain't gonna give us any visual information about that surface. So photon must carry visual information about the surface from where its ejected..
I'm saying that one single photon does _not_ form an image. The human brain doesn't even register one photon. You need a bunch of photons to form an image.
Yes..you explained that in your photon video..i remember that. But my concern is every photon carries a certain visual information about the particle it meets , that interact with our nerves to give vision. Photons comming from a table, a wall and a mirror all carry different visual information. How right am I to think this way??
My textbook which was written like fifteen years ago or more had 20 billion as the age of age universe. Is it because we didn't know about inflation back then and thought of expansion as linear?
If the Planck Telescope shows the CMB to be homogenous would a more sensitive instrument be able to detect differences in the CMB showing it to be 'lumpy'?
The CMB is _nearly_ homogeneous, but not perfectly. There are bumps and Planck can see them. I did a video all about the CMB recently: th-cam.com/video/Js4Oy2CjOtE/w-d-xo.html
I have another question... The universe is 13,8 bilion years old, but the radius of the observable universe is about 47 GLy (caused be the expantion of the universe) ... As I understand it, the expantion of universe is accelerating (or better yet the farther is something away the faster it moves away) and this acceleration is increasing... so there must come, in the future, some critical radius of the observable universe when its boundary will be moving away at the speed of light (so it will be ever impossible to see farther)... how can we calculate this critical radius and if possible, the time (like in bilions of years) when this will happen?
Hi Nick. I was wondering what "the age of the universe" really meant, and couldn't easily find any info about it. Since time is relative, what perspective are we measuring from here? Is "the age of the universe" different in different places? Sidenote/Constructive Criticism: I feel like you skimmed over the math a little too fast, leaving myself feeling like I didn't truly conceptualize or understand the subject. Either way, great video!
*"Since time is relative, what perspective are we measuring from here? Is "the age of the universe" different in different places?"* Yes, it's different in different places. When we quote a number like 13.8 billion years, we're measuring that in something we call the comoving frame. I talk more about that here: th-cam.com/video/9udKv1NXm7w/w-d-xo.html
Nick, a question that's been bothering me for quite some time now. See, when the universe was pretty young, it had a lot of mass in a small amount of space... so small in fact that I assume the entire mass of the universe would have fit within it's schwarzschild radius (I guess, my assumption may be incorrect here). In that case, why did it survive completely collapsing into a black hole? or was it always a black hole to begin with at the Big bang?
Because that's not how the geometry works. The "Schwarzschild radius" was derived mathematically assuming _very_ different conditions than we would see in the early universe. The geometry is completely different. You can't make that kind of comparison.
Maybe this from Eugene? th-cam.com/video/CliW7kSxxWU/w-d-xo.html (I'm working on one too that gives a little more physical context, but I'm not sure when it will be done.)
"I took everything pedantic about myself and I put it into you. What was I _thinking?!"_ 😆 That'd you could answer him once instead of multiple pedantic commenters?
Great video Nick, as per usual. I have a question I’d like to ask. It is as follows: We know from special relativity that the passage of time changes with the motion of the observer. So, the 13.8 billion years is the age of the universe as measured by an observer moving with what motion? Is he/she a stationary observer? If so, the observer is stationary with respect to what?
The early universe (pre CMB) is built with particle models. All that existed back then was particles, so time is measured in their reference frame (because it's the only reference frame available).
@@ScienceAsylum Really? I figured that when you factor in special relativity and a bunch of the things in the universe moving at vastly different speeds relative to each other, that some things in the universe would have experienced more time than other things and hence be older. Say for example a bunch of stuff in one region of the universe is moving at 0.5c while in another nearby region a bunch of stuff is moving at a speed of 0.6c or something like that. In general stuff travels at a variety of speeds which should have something to do with time dilation, unless I am missing something.
"it's just how far back our knowledge of the Universe goes" - thank you for saying that, you are the first person I have heard to say that instead of the universe is x amount of years old.
stevemonkey6666 😳 Indeed, but saying ‘how far’ implies some form of distance or extent of existence. Using mathematical extrapolation we now consider the existence of the known universe to be 13+ billion years old and still ‘growing up’ . . . !
I mean, the age of our universe is AT LEAST 13.8 billion years old. Back when I was a kid, it was 7-20 billion years old, but now there is a study implying its possibly 26.7 billion year old.
Personally, I am quite skeptical on that. We know for a fact that certain processes take less time and I am fairly certain our limit is at 16 billion years old. As that study for the 27 billion year old universe is mainly looking at stars that theoretically could have formed within less time thanks to some quantum shenannigans or theoretically could have survived a big crunch.
"13.8 bil years is the time back till which our current knowledge can go"
Nice and exact statement lucid.. awesome work
An alternative reply could've been - "Nick and lucid statement" :)
I was letting the video play while typing a clever bit about how time dilation in a massive early universe makes the 13.8 billion number nonsensical when just before I finished in the last 30 seconds of the video he said basically that sort of thing. Drats. I was looking forward to typing something clever today.
I love how the "nerdy" version of yourself also works to prevent people from being pedantic in the comments hahaha
There's always the smarty ones that just overcomplicate stuff by being way too picky about details
I'm pretty sure you do it on purpose too, but I won't tell anyone! Love your stuff!
War Oliv 😖 Hm! ‘smarty ones too picky about details’ . . . ? Remember what happened to Apollo 13, and how ‘smarty ones’ who were ‘very picky’ about details brought the three astronauts back safely to Earth? Those forensic scientists who examine the minutest details in an investigation? Are they ‘nerdy’ in your esteemed (?) opinion? Really!
Do you even understand in what context I said that? This is a science channel that tries explaining science in a way that most people can understand. Trying to simplify a bit while still being accurate IS the point of the channel. That's why he doesn't use too much math, so almost everyone can understand what he's talking about.
Context mate, the example you gave is completely different from the point of these amazing videos. Overly detailing stuff isn't bad, in fact it's good. Not in this case though, since he's trying to teach in a way people will understand and stick around, instead of closing video because it is filled with advanced math.
"I won't tell anyone"
Well that's been thrown out the window
Actually it was already outside the window to begin with
Lets just hope future astronauts arent using these videos for references. Lol. This guy is great!!!
@@sirmeowthelibrarycat Way to miss the point completely.
as an engineering student halfway through my curriculum, that simple diagram of the stress energy tensor colored like that just made tensors click for me, so thanks!
This channel has been beyond instrumental in helping me develop my first novel. Thank you and keep making more
You're welcome! Glad to help :-)
Appreciate the response! Don't be surprised if I make a character based on you one day :-)
Tactile Therapy Next Dan Brown
Name of the novel! I want to read it once it's out :D
Thanks! Its out now...it's called Tactile Therapy. You can search for it on amazon and itunes. The links are on my page
*Astronomical* video quality as usual.
Best explanation I've seen of the big bang model, you rarely see people being honest about the fuzzier parts for some reason
I will avoid the math you 'kind of glazed over' but do wish to thank, thank, thank you for all of your excellent work. Specifically that whole "data vs. results" subplot was HILARIOUS in this episode. 10 out of 10!
Bedankt
Thanks!
Thank you for the support!
I was sceptical when I first came across this channel, but now I really appreciate the content for what it is - science and simple explanations. I guess I'm a little crazy now...
Glad you came around :-)
"Gravity isn't about mass, it's about energy."
Thanks for this. Why can't textbooks just come out and say this? It'd clear up a lot of confusion about photons being massless.
Really love the way how you bring up all the problems in a calculations and put up the answers for it too..... that's what makes u the best
Man your vids are amazing!!
Nicely explained
I love it when assumptions and ideas that I’ve held for decades are blown away - and, once again you have succeeded to do so! Awesome!
Great overview. It's always nice to have the details and methods behind the "results" we learn. :)
So you borrowed a t-shirt from PBS spacetime guy.Its good to see my two favorite channels wearing each others shirts.
Yeah, we exchanged shirts :-) I actually got a chance to talk to him in person a few weeks ago (VidCon), so that was cool.
you're fabulous in explaining even the most difficult thing in cosmology.
This is the first time I am on your channel and I absolutely love your content right away! :)
For what we know it could be infinitely old, it's nice that you clarified that it's only about our current knowledge and not the actual age
This video, by itself ,deserved an award. You're the best, those who dont know about this channel are missing out on so much. Thanks for answering the biggest query I had eversince I started pondering about astronomy. Thanks a lot sir.
You're welcome :-)
Your videos are by far the best
This channel is criminally underrated.
Good to see your video again .. Its hard to wait for your videos ..please make more more more..Thanks BTW
Thank you. The best and most reasonable and honest answer to the question.
Just found your channel. Why doesn’t this have more views? More subs? Incredible stuff!!
Thanks! 🤓 (I'm a little weird, which probably doesn't help the channel's growth.)
This is my favorite answer to this question. We don’t know for sure, this is just how far back the knowledge of the universe goes. Perfect. Another great video!
Please don’t ever get rid of that pet monster!!
I've had him since I was about 4 years old. He's not going anywhere.
The Science Asylum My brother and I got them when he was 4 and I was 8. We used to practice pile drivers on him. We gave my brother’s a short hair cut to tell them apart.
Love your videos. I have a few suggestions for when a clone pops into frame:
A. Don't have your actors facing each other directly. Have them point slightly towards us, as it seems to invite the viewer in to the conversation. If they are directly opposing it makes us feel awkward.
B. Another idea is to not have a cut at all. Keep your "you" self in frame and have your clone step into frame and ask a question or contest, and step away. Less jarring and slightly more believable without a sudden perspective change.
Fascinating! I like the shot if the data you included
I appreciate the information you provide, hard to believe, but this kind of information and the way it is explained are not found on other channels. I shake your hand, with respect ! I will share links to your videos everywhere I can, hopefully this will increase the subscribers (1M+) and help you deliver great content like this for as long as possible.
Wow. You blew my mind as always :)
Instant like.
Incredible video! Well done!
As Einstein said "If you can't explain it simply, you don't understand it well enough" and u make everything simple. please do video on spacetime, if space is expanding so we have to consider time is also expanding but we dont experience time expansion.
loving your productivity nick :-)
Another great video, and thanks for recognizing Data's personhood.
How old is the universe? It doesn’t have an age. It has always existed. And It will never end.
Hi Nick. Absolutely love your videos. You are incredible at making very complex subjects understandable to the layman. Been watching through them now from your first to whatever the latest is. Thanks 😊
Glad you like them 🤓
Wow, that was complex!!!
I couldn't grasp.
New Science Asylum video! YES!
Awesome explanation
Really liked the video and how you made the math accessible. Will you ever make a video on tensors? I'm buying your e-book and can't wait to read it.
Thanks for another great video!
Thank you for the another amazing video.
when using telescopes to "see the past" how do we know that the conditions and constants of the universe used to be as they are today and that we can even do those extrapolations into the past? how can we rule out other possibilities or the influence of things/processes we can't see today?
the stuff we can see with telescopes is relatively mundane ie. matches the predictions. We rule out other weird possibilities via occam's razor - it's simply more likely that our knowledge about the universe today (and near past) extrapolates into the further past, than the possibility that it just happens to look that way.
Just to add to what KohuGaly said, we do sometimes find that something we thought was constant isn't constant. The "Hubble constant" is a good example, which is why we renamed it the "Hubble parameter."
0:55 Is it only one instrument which made this measurement?
The Planck space probe had two different instruments installed: a low frequency instrument (LFI) and a high frequency instrument (HFI).
Loved this explanation! Many thanks! Great work as always (you must do some collabs with other science channels to get the name out)!
Working on a couple collabs right now actually.
Yeah right! I will have a look to the maths! Like I would understand it!😂😂😂 I MISSED YOU Nick Lucid from the Science Asylum!🤗 Welcome back!!! ;-)
Another great episode!
Another great video😁, i was thinking about that a lot😆..that was a great explanation, thanks for your hard work))
There was a difficult amount of information in this video for me to follow. Kudos to those who can grasp the concepts here.
Doobly doo, made me smile :) Matt Colville also calls the doobly doo that... great video Nick!
Wheezywaiter came up with the word years ago and it spread like crazy.
Perfect video. Like always.
THE SCIENCE ASYLUM --> Question: Can you do a video about the nature of the Island of Stability?
Well explained, as usual. Thanks.
Btw I love your videos bro...!
You are so brilliant Sir.If you ever decided to come to my country please make it public .I will at least come to get a glimpse of you .Wishes from Srilanka (South ,,Asia)
I was unaware just how much our understanding of time broke down in the first phase of the universe (I knew that questions about what happened before the big bang suffered from this). I took the "age of the "universe" figures quite literally. Thank you for helping to clarify that.
Look up space time start from the first video
@@zerocool4835 Space time is great and I am a regular viewer, great to meet a fellow fan. Also really loved Infinite Series (a pity that the show couldn't live up to its name).
I understood that at the very beginning our understanding of time breaks down at t == 0 (in the same way that the meaning of north and south breaks down at the poles).
However, what this video managed to get me to see is that our understanding is still very limited the early stages of the universe for t > 0. This is qualitatively different from our understanding breaking down at the singularity (north is still perfectly meaningful until you reach the north pole).
Well this makes me feel old, back when I was in college the astronomy lecturer said that the universe was only 13.6 billion years old, how the time flies.
Wow. So you've been around 0.2 billion years! You must've seen some crazy things in your time.
I liked and licked this episode!
Tell us more about black holes
Here some facts about black holes: No one ever saw a black hole, no one that lives today will see one, anything else about black holes is speculative.
Chike boi you can't see them
No one ever saw earth core yet we can still know stuff about it. (I suppose you could say that is also speculation but if you go with that logic to extreme everything is only a speculation.)
Yes we speculate stuff about earth's core too, and it is only few thousand kilometers beneath us and there are some observations to be able to speculate about it.
What observations do we have to support all the speculations about black holes?
Chike no one has ever seen the earth's core either. we use indirect detection methods of almost everything we have observed
I've got a question
You said that all frames are equal in every way and no frame gets a priority over another
And also according to Maxwell;all accelerated charged bodies emit radiation.
But in the frame of the charged body;it appears to be at rest with respect to itself.Then in this situation; how would it emit radiation???
Short Answer: The statement "accelerated charges emit light" isn't universally accurate.
I have a video on my to-do list that might help with this.
So you mean that accelerated charges may emit light or something like that???
I've got another question on
Einstein's photoelectric equation
It states that E(of photon)= work function+kinetic energy of electron.
Now work function is in a way binding energy of the free electron which is equal to KE + PE and it implies that it is frame dependent
And also the KE of the ejected electrons is also frame dependent
The photoelectric equation turns out to be
Frame independent(E of photon)=Frame dependent+frame dependent
How is this possible??And where is the mistake???
1) I mean that accelerating charges _don't always_ emit light.
2) The flaw in your logic is the energy of a photon is _most definitely_ frame dependent.
So is it h times f(observed)
Well done.
Plz make a video on the math of general relativity
Thanks
only last part i got it.... other things i don't, but i like watching/listening/both things i don't know, especially if someone can make it interesting...
Thanks! According to some TH-cam cosmologists the age of the universe is 13.8 billion years. They claim that they know what happened before from conception to the first data. But whatever, good video. I need to watch it a few times on slow speed, though. It goes too fast for me (again).
You are just amazing
Can you please explain all the hipe about graghene and what it might mean for the future?
1:07... A very interesting idea. How to you make your clones behave differentially? It is psychological or it is genetic? And how are you making them in the first place? We deserve some answers after so many time!
Quantum mechanics prevents _exact_ copies, so they always come out a little different. ( I gave a teaser of my cloning machine here: th-cam.com/video/a9T26ItpcDA/w-d-xo.htmlm21s )
2 videos in 1 month? Great!
That's what I try to make happen every month. I don't always manage it though.
The Science Asylum Just do your best. I think only uploading once or twice a month might actually work to your benefit. Less frequent uploads make each one more exciting. I've noticed lately that I'm more likely to watch a video soon after its uploaded if it's from a channel that uploads less frequently. Keep doing what you're doing. 🙂
How old those videos are?
What happens before the upload?
Where they come from?
Have they always be there?
Could anything considered to be void of energy also timeless? Can timeless objects be also considered matter?
If this question isn't worth anyone's time, does it mean it doesn't matter?
PLEASE CAN YOU DO VIDEOS ON-1.WHY INTERNAL CONSTITUENTS OF A SYSTEM CANT AFFECT IT EXTERNALLY?( ie a person inside a box cant cause the box to move by hitting against the wall of the box from inside...I think this is also reason why emdrive cant work)2.WHY WE NEED FORCE CARRIER PARTICLES TO DESCRIBE FORCE?3.CAN WE EVER CHANGE THE LAWS OF PHYSICS INTO WHAT WE LIKE?
I love this video. I never say the universe is 13.8 billion years old. I always clarify that based on our knowledge, the universe is roughly that age. I always make sure to state that our knowledge is limited at best, and even based on that, we only use rough estimates to get the 13.8 b
You deserve 13.8 billion views
I love this video
Is there any estimate of how big/small the universe was during the Electroweak Epoch? Could all that energy condensed in a small region affect the perception/measurement of time?
There is one thing that I can't get may head around. It is the fact that time "ticks" more slowly when you measure it close to some heavy body. But in the early universe when there was primordial soup of quarks and gluons the energy density was enormous so shouldn't it slow time flow. I mean that during first Universe epochs the time was running extremely slowly... how do we take it under calculation during while calculating 13,8???
In case of two clocks, one close to a heavy body, one far away, you can keep them there for a while, then bring together and compare what they clocked. So when you see one ticked less, you can say it ticked slower. But in case of early universe we have nothing to compare with, so any amount of seconds that ticked there is all there is, there is no clock that ran faster and we could compare to.
It's like watching TV series. We can say "this show has 400 episodes now, and that particular thing happened 321 episodes ago". Even if some episodes were released daily and some others once a month, if you don't have that external clock and can only talk about episodes numbers, if you only measure time in episodes this relative time rate is unobservable and doesn't change anything inside the TV series.
thedeemon, that's a great analogy!
How can we calculate the age of the Universe by reversing expansion when we only know the size of the observable universe, couldn’t the actual size of the universe be 10 or 100 times bigger?
In other words
How can we calculate the age of the Universe by reversing expansion when for d=distance you are using the farthest “observable” star or galaxy, couldn’t there be galaxies 10 or 100 times farther away whose light has not reached us yet or never can reach us?
The size of the _entire_ universe could easily be infinite, but it doesn't matter. All that matters is the size of the _observable_ universe.
Is the Big Bang an explanation of the origin of matter or of the origin of space time?
1: Was there more than 1 image of the CMB taken?
2: In an ever expanding observable universe and the CMB sitting on the observable universe horizon, wouldn't the CMB image change due to it's movement away from us?
1. The image I show in my videos is a composite image made from multiple smaller images. It was made in 2015 and is the most detailed version made so far. There were less detailed version made previously.
2. The CMB is emitted by matter and that matter does move away from us as the universe expands. However, the CMB light itself is _not_ expanding away from us. It stretched out during the trip though, which is why it's microwave light now. It used to be visible.
(You're on the right train of thought though with motion affecting the way we perceive the light. The motion of Earth around the Sun, the Sun around the galactic center, and the galaxy through space all affect the measurements of the CMB. Those have to be removed from the data before we get that image I'm showing.)
@5:14 Tardis
Hey Nick! I would love to see you create a video about particle interactions inside the nucleus of an atom and, more specifically, the strong nuclear force. What governs it? Also, why are neutrons so unstable outside of the nucleus but not once inside? Love your videos and keep up your great work!
Quantum chromodynamics is cool, but complicated. It might be a while before I get to it.
During reflection of image, how does photon show the object as an image in the mirror?? Is it like photon I carrying information about that object and projecting it into the mirror to form the image??
Also how does photon reflect off from the mirror??
If it reflects the same direction it was incident, does that mean it had to come at rest and reaccelerate in that reflected direction??
The photon doesn't carry information about the object. It just comes at our eyes from a specific location on the mirror, which depends on what part of the object it came from. If enough photons reflect off the mirror, the whole collection of them form an image.
(A photon ceases to exist at the mirror and a new photon is created that travels along the new path.)
Yes..but for a photon to show ones image, shouldn't it first come from object and strike the mirror....
I was focusing on the fact that a photon comming from a table and entering our eyes will show us the table. A photon from sun will show us the sun..so different photon comming from different thing provide us with visual information of that thing. So visual information must be carried by photon. If an electron were to come from a surface and enter our eyes, it ain't gonna give us any visual information about that surface. So photon must carry visual information about the surface from where its ejected..
I'm saying that one single photon does _not_ form an image. The human brain doesn't even register one photon. You need a bunch of photons to form an image.
Yes..you explained that in your photon video..i remember that. But my concern is every photon carries a certain visual information about the particle it meets , that interact with our nerves to give vision.
Photons comming from a table, a wall and a mirror all carry different visual information.
How right am I to think this way??
My textbook which was written like fifteen years ago or more had 20 billion as the age of age universe. Is it because we didn't know about inflation back then and thought of expansion as linear?
We just didn't have the "data" required to make more accurate estimates.
If the Planck Telescope shows the CMB to be homogenous would a more sensitive instrument be able to detect differences in the CMB showing it to be 'lumpy'?
The CMB is _nearly_ homogeneous, but not perfectly. There are bumps and Planck can see them. I did a video all about the CMB recently: th-cam.com/video/Js4Oy2CjOtE/w-d-xo.html
I have another question... The universe is 13,8 bilion years old, but the radius of the observable universe is about 47 GLy (caused be the expantion of the universe) ... As I understand it, the expantion of universe is accelerating (or better yet the farther is something away the faster it moves away) and this acceleration is increasing... so there must come, in the future, some critical radius of the observable universe when its boundary will be moving away at the speed of light (so it will be ever impossible to see farther)... how can we calculate this critical radius and if possible, the time (like in bilions of years) when this will happen?
There has _always_ been that boundary. It's called the "cosmic horizon." It's the edge of the observable universe.
Was there a singularity at the beginning or we used to say?
At the moment, our models say there was a singularity, but we might find in a better future model that isn't actually true.
Yay! Another new videos for us crazies!
Yes, you are a sick puppy!! Thanks for the video!
Is the age of the universe based on time, as measured on earth. Would the result be different if we were on a planet ten times the size of ours?
Hi Nick. I was wondering what "the age of the universe" really meant, and couldn't easily find any info about it. Since time is relative, what perspective are we measuring from here? Is "the age of the universe" different in different places?
Sidenote/Constructive Criticism: I feel like you skimmed over the math a little too fast, leaving myself feeling like I didn't truly conceptualize or understand the subject.
Either way, great video!
*"Since time is relative, what perspective are we measuring from here? Is "the age of the universe" different in different places?"*
Yes, it's different in different places. When we quote a number like 13.8 billion years, we're measuring that in something we call the comoving frame. I talk more about that here: th-cam.com/video/9udKv1NXm7w/w-d-xo.html
Nick, a question that's been bothering me for quite some time now.
See, when the universe was pretty young, it had a lot of mass in a small amount of space... so small in fact that I assume the entire mass of the universe would have fit within it's schwarzschild radius (I guess, my assumption may be incorrect here). In that case, why did it survive completely collapsing into a black hole? or was it always a black hole to begin with at the Big bang?
Because that's not how the geometry works. The "Schwarzschild radius" was derived mathematically assuming _very_ different conditions than we would see in the early universe. The geometry is completely different. You can't make that kind of comparison.
@@ScienceAsylum... so if the arrow of time were to be reversed, then there would come a time when it would be impossible for black holes to exist?
Yes, at least in the way that black holes currently exist.
@@ScienceAsylum That's amazing! Thanks Nick!
06:43 what's that music in background?
th-cam.com/video/CxylBTofdtM/w-d-xo.html
Can you make a vedio on how waves like em waves penetraye through some materials and not others.
th-cam.com/video/wDu0KMdDD1I/w-d-xo.html
Ah but doesn't causality and thus time require infinite regression, like trying to find the beginning of a circle?
Anyone have any accessible explanation of tensors?
Maybe this from Eugene? th-cam.com/video/CliW7kSxxWU/w-d-xo.html (I'm working on one too that gives a little more physical context, but I'm not sure when it will be done.)
"I took everything pedantic about myself and I put it into you. What was I _thinking?!"_
😆
That'd you could answer him once instead of multiple pedantic commenters?
You said “glazed over” when you meant “glossed over”. Glazed over is what our eyes do if you get too detailed on the math (which you don’t really do).
Great video Nick, as per usual. I have a question I’d like to ask. It is as follows: We know from special relativity that the passage of time changes with the motion of the observer. So, the 13.8 billion years is the age of the universe as measured by an observer moving with what motion? Is he/she a stationary observer? If so, the observer is stationary with respect to what?
The early universe (pre CMB) is built with particle models. All that existed back then was particles, so time is measured in their reference frame (because it's the only reference frame available).
@@ScienceAsylum Really? I figured that when you factor in special relativity and a bunch of the things in the universe moving at vastly different speeds relative to each other, that some things in the universe would have experienced more time than other things and hence be older. Say for example a bunch of stuff in one region of the universe is moving at 0.5c while in another nearby region a bunch of stuff is moving at a speed of 0.6c or something like that. In general stuff travels at a variety of speeds which should have something to do with time dilation, unless I am missing something.