8.03 - Lect 15 - Doppler Effect, Big Bang Cosmology, Neutron Stars & Black Holes
ฝัง
- เผยแพร่เมื่อ 10 ก.พ. 2015
- Doppler Effect - Sound - EM Radiation - Binary Stars - Neutron Stars - Black Holes - Big Bang Cosmology
Assignments Lecture 15 and 16: freepdfhosting.com/b44fe0e3c0.pdf
Solutions Lecture 15 and 16: freepdfhosting.com/39414e0841.pdf - วิทยาศาสตร์และเทคโนโลยี
Wonderful!! I'm reading Alan Guth's literature and newer one (John Baez). Cosmology is amazing and the way how you explain it in 8.01, 8.02 and 8.03 (Doppler Effect Lectures) is fantastic. Congratulations, Professor.
awsome awsome awsome....each time feeling good while studying from profr. LEWIN....
+Vivek Raj :) :) :)
You are legend Mr. Lewin. I wish i had chance to take lecture from you.
:)
Well you have now on TH-cam ..
Great work as usual...... seeing this made me happy ....thank you
Amazing made physics interesting for me once again. Just the best
This is one of the most interesting lectures ever Sir! I bow down for such a visual explanation of the universe and for linking it with Doppler shift, Hats off Sir Thank you sir
Dear Professor Lewin. I studied physics long time ago during my civil engineering grade. It has been quite an emotional support during this long quarantine ( every day one lecture) to review those key subjects as angular momentum and application to astrophysics. Even I dusted off the classic Resnick Halliday Part I book !!!. Thank you very much for these wonderful lessons !Jorge from Buenos Aires-Argentina
That was my physics book and stiil have as reference.
Hello ! sir, you are my real hero....I pray to God keep stay healthy and Happy
That's because it deals of gaseous and not solid and compact matter! Tkank you!!
Hello Professor, so in theory, a person that lives in a planet 1 light year from Heart, with an incredible powerful telescope can theoretically see what is happening on Heart, 1 year ago? He can see our past.. this is mind blowing..
Thank you for those amazing lectures
I have question, if the light is traveling into blackhole with steady velocity as in the equation then it should act like magnetic field? If yes, then imagine if we have 2 same poles magnet then how it move in steady velocity? Is the frequecy change? The light intensity! then inside blackhole should bright?
sir in the part 1:03:11 is it related to 21 cm line of hydrogen that we often referred to 21 cm cosmology ?
I am listening on TH-cam, and my cat perked up during the tuning fork
Now that was good!
You are a superhero
:)
Thankyou so much sir❤, sir in 40:30, how can we study the spectrum of blackholes which donot escapes light.
Hello Prof Walter, something does not make me sleep at night ! Knocking stars! Is it real? If yes why do they knocking like that, it seems like someone knock the door !!!!thnx
btw, he couldn't hear the difference in sound at 9:20 because he was the center of rotation
Professor how do we know that the light I am looking at is the shifted version of a specific spectrum like Ca(K) lines as you mentioned? Is relative wavelength difference between different lines of the received spectrum or is there some other way for me to know which spectrum in the laboratory should I compare it to?
take a course in astronomy
18.10,sir, how do you know the dark absorption line observed from the spectrum of Delta Leporis is Ca if it has different wavelength compare to the Ca(K)? If we had included the Doppler Effect, there must be a difference between the laboratory spectrum and the spectrum observed from Delta Leporis, so how can we tell the dark absorption line from the spectrum of Delta Leporis is Ca?
It is not just a line but a compination of bonded lines.
Great lecture thank you very much however you lost me at around 33:00 I dont get how an astronomer can say that he knows what m1 is by just looking at its spectrum. Isn't m1 related to m2 as it was shown in 24:55 how can an astronomer possibly figure out m1 without having an idea about m2?
Can you tell me please, where the period T at 24:14 belongs to? I have already used google to answer this question, but I didn't find a convinient answer.
orbital period
Thanks, but is it the period of both masses or just the period of one of the two, or something completely different?
How can the orbital periods of the 2 stars in a binary system be different?
Well I was not aware of the fact that it was about a binary system I am sorry.
Why when I start watching any video for dr Lewin I have to complete it ? I am not a physicist but It’s amazing really
Sir, I have a doubt. How is it possible for a black hole to evaporate the destroyed information (Hawking Radiation)? Is it something related to the Holographic Principle?
use google
Hawking actually changed his mind on this fact. I recommend reading The Black Hole War by Leonard Susskind for an in depth explanation on this topic.
Sir, what was there before the big bang? What is the universe expanding into?
String Theory
Love u sir
sir i am pretty sure that you have heard about oscillating theory of universe . i think that it is correct if applied along with special theory of light
read up on cosmology - use the web
Fortunately this year scientists and astronomers have captured an image of the black hole (Event Horizon Telescope). I felt lucky being alive to see this event !
Really: You think so, could be all bs..
22:33 this is the center of my WHAT???...... uuuuuh professor Lewin 😂
Professor could you please upload the hand written notes for these classes in the description. It will be a huge help and a great time saver.
ha ha ha each lecture has about 50-70 pages handwritten notes. I have all these notes at my home of my 94 MIT course lectures. They will all go to the MIT Museum.
@@lecturesbywalterlewin.they9259 Can people on the internet get a soft copy?
@@admiralhyperspace0015 not possible
Walter, how can I help with the subtitles?
You can only help by writing for each lecture a file that I can then use to get cc. It will take you approx 5-7 hours to do that for EACH of my 23 lectures. Send me the file as soon as you have one ready.
@@lecturesbywalterlewin.they9259 What kind of file do you mean? I send it to you by here(the comments)?
@@pat6595 do your homework on what it takes to get cc. I cannot explain this in detail but I am sure you can find out online. It's a HUGE amount of work.
@@lecturesbywalterlewin.they9259 Yes, it is. You are right.
he has the ability to draw straight lines and circles free hand, without mechanical assistance.
I read your book Sir
hello sir....your lectures are always source of motivation for me to study physics....can I consult these for jee advanced
:)
Is it true that since energy conservation is because of time translation invariance and the universe is expanding that energy is not 100% conserved on the largest scales? Is this the same as thinking of the energy within the universe being transferred to energy of the expansion of space-time?
energy may not be conserved in the multiple universes. I suggest you google this.
Lectures by Walter Lewin. They will make you ♥ Physics. Thank you! I just finished your final 8.03 lecture and have watched all of them from 8.01-8.03 over the past 4 years and I have loved them so much!
dear professor , i want to research in cosmology and actually in that mathematical point(singularity) which come under quantum gravity concept.
so after your wonderful lecture , one thought came over my mind .
our universe has expanded from singularity and black holes also end at singularity.
so, is it possible that the matter which goes inside black hole travel to past to singularity then again to present but in different universe.?
actually there would not be violation of physics laws about conservation of matter that matter can neither be created nor be destroyed ?
take some courses in Cosmology. The following statement from my former colleague Prof Alan Guth may interest you: *"It is possible that the total energy of the entire universe is exactly zero, with the positive energy of matter completely canceled by the negative energy of gravity. I often say that the universe is the ultimate free lunch, since it actually requires no energy to produce a universe."*
@@lecturesbywalterlewin.they9259 That is quite interesting , professor. Isn't professor Alan guth creater of eternal inflation theory?
@@MaheshSharma-dy6sq th-cam.com/play/PLUl4u3cNGP61Bf9I0WDDriuDqEnywoxra.html
I like the study of universe so I will see professor Alan guth's lecturers..😀👌❤
great! his couse "The Early Univesre" is on my channel.
@@lecturesbywalterlewin.they9259
yes sir I found it and thank you!!😀
In relativistic doppler effect (at 12:31 ), the relative velocity is at angle θ, so how can you take the β on the denominator as v/c? Isn't it be v(cosθ)/c? And so Above you won't need the extra cosθ term as it will be included in β?
Yes what I wrote down is correct. It's gamma times [1- beta*cos(theta)]. gamma is due to time dilation. Even if theta is 90 degrees, there is time dilation by a factor gamma (that is REALLY not Doppler shift even though it is often given that name but that is a misnomer). beta*cos(theta) is the radial component of the velocity. Most books write sqrt[(1-beta)/(1+beta) ] and they mention then that beta is the radial component. That is wrong! If the radial component is zero, there still is time dilation by a factor gamma which is not zero, Thus my equation is correct ! and many books have it wrong.
I read up again on the derivation of the infamous result for relativistic Doppler shiftL sqrt[(1-beta)/(1+beta) ]. This is ONLY correct when the object moves in your direction or in the opposite one. It's wrong in all other cases, and it's DEAD wrong if theta is 90 degrees.
Does that mean if the motion is perpendicular, towards or away from the observer, the amount of time dilation would be same? It's hard to believe that on the perpendicular case the amount of time dilation would be same because, in perpendicular motion, the effective velocity (observed from the distant receiver) would not be same but less in amount and so time dilation should be less. It there any mathematical proof that time dilation does not depend on the direction of motion OR gamma only depends on the magnitude of the relative velocity and not on the direction of the motion?
And what about Relativistic aberration? Would Observed angle be same as theta or it would change according to Relativistic aberration equation?
What I discussed with you is called transverse Doppler effect. In my view its a misnomer but that a separate issue. Transverse Doppler effect is simply time dilation. If an object moves in a direction of 90 degrees to my line of sight to the object, there is a time dilation gamma.
In the frame of the receiver, θ0 represents the angle between the direction of the emitter at emission, and the observed direction of the light at reception. In the case when θ0 = π/2, the light was emitted at the moment of closest approach, and one obtains the transverse redshift. Sometimes the question arises as to how the transverse Doppler effect can lead to a redshift as seen by the "observer" whilst another observer moving with the emitter would also see a redshift of light sent (perhaps accidentally) from the receiver.
It is essential to understand that the concept "transverse" is not reciprocal. Each participant understands that when the light reaches them transversely as measured in terms of that person's rest frame, the other had emitted the light afterward as measured in the other person's rest frame. In addition, each participant measures the other's frequency as reduced ("time dilation"). These effects combined make the observations fully reciprocal, thus obeying the principle of relativity. The transverse Doppler shift is central to the interpretation of the peculiar astrophysical object SS 433.The first longitudinal experiments were carried out by Herbert E. Ives and Stilwell in (1938), and many other longitudinal tests have been performed since with much higher precision.[2] Also a direct transverse experiment has verified the redshift effect for a detector actually aimed at 90 degrees to the object.en.wikipedia.org/wiki/Relativistic_Doppler_effect#Transverse_Doppler_effect
Does not it mean elliptical motion?
Mr walter can i ask you a physics question?
Lewin is fantastic, unmatched lecturer, but here @2:40 he should be using the wavelength to derive the effect of Doppler. The student can not appreciate the received freq. equation otherwise.
Good mornig, Professor.
If in the Lagrange Point "gravitational pull forces" towards doner and accretor ARE THE SAME and if this point lies into de surface of the doner, why the matter of the doner that is on the side near the accretor wants to float towards the accretor? Why the force in this direction is larger and it is energetically more favorable when the forces are supposed TO BE THE SAME in the Lagrange Point? I can sense it but I don't find the right physical explanation...
Thank you, Sir.
+Jordi GS
The Lagrange points mark positions where the combined gravitational pull of the two large masses provides precisely the centripetal force required to orbit with them. There are five such points, labeled L1 to L5, all in the orbital plane of the two large bodies.
you do not mean the Lagrange point. If the point A where donor's and accretor's gravitational pull are equal lies inside the donor, then the material in the donor closer to the accretor than point A will experience a larger gravitational pull towards the accretor than towards the donor thus it will move to the accretor.
Dear professor, thank you for the amazing quality in the lecture as always. What confuses me is how does the asymmetry discussed in 0:40 does not contradict the principle of relativity? Thank you once again
why should it contradict that?
It seems to allow us to tell the difference between a "moving" and "stationary" observer, doesn't it?
i.e it assumes "absolute space".
Or, in other words, I thought that the postulate in relativity is that the scenarios of t being a moving observer, and r, the receiver being a stationary observer has to be necessarily identical to t being the stationary observer, and r being the moving observer, assuming both are inertial frames of reference.
GR deals with cosmology. Countless Galaxies move away from us with a speed much larger than the speed of light. That is no violation of SR.
>>>>It seems to allow us to tell the difference between a "moving" and "stationary" observer, doesn't it?>>>>
NO
Sir i have a problem just disturbing my mind ... what about a freefall under gravitational accelaration that never ends.... can it reach the speed of light ..... as my calculations if an object is droped from a height of 4.5 × 10^15 m (roughly) it will reach the speed of light. ...i dont know if i am talking of utter bulshit.... but sir give me a answer to this....let thee eyes have a peacefull sleep.....
free fall of an object to Earth from "infinity" will reach Earth at 11 km/s.
+Lectures by Walter Lewin. They will make you ♥ Physics. sir how can a object from infinity. to earth. earths gravitational pull is not so strong
Sir what is the driving force of expansion of universe
The energy from the Big Bang drove the universe's early expansion. Since then, gravity and dark energy have engaged in a cosmic tug of war. Gravity pulls galaxies closer together; dark energy pushes them apart. Whether the universe is expanding or contracting depends on which force dominates, gravity or dark energy.
@@lecturesbywalterlewin.they9259 Thankyou for the reply sir. Sir what is the dark energy force.
I feel good that he snuffles because I do that too
❤️👍🙏
4 minutes: but if that is so, then motion cannot 'just' have relative meaning.
:)
Lectures by Walter Lewin. They will make you ♥ Physics. But therefore i found a mistake in my paper :(. It doesnt affect my theory, but its sooo embarassing. I want to crawl into a hole. I emailed the journal.
In 1915 Einstein corrected his paper of 1911 about light bending grazing the sun.
1:00:06
and here comes mid-2022 where we have James Webb Space Telescope's ERO (Early Release Observation) which has filtered out on the basis of spectroscopy a set of candidate galaxies with a redshift of Z~11 all the way upto even 20 !! (Z is what in the lecture prof said as Ⲗ'/Ⲗ)
all thanks to MIRI and other devices on board
Hans Alvin ?
Please make subtitles
to make cc would take me at least 7 hours per 80 min 8.03 lecture. If you want to do it, that would be great, send me the file and I will use it.
30:17 200,000km/s is not 70% the speed of light
asshole!
It’s true... 2,00,000 kms/sec is exactly 70% of the speed of light in a sec..
To 1 significant figure, it is 70% of the speed of light.
Subtitles please :'(
sorry relativity
Lol, sapiens so funny.
Dark energy is an illusion caused by the gravitational distortion caused by the gravitational fields of distant galaxies.
Gravity from distant galaxies has a redshift effect on the frequency of light they emit in the same way that gravity can bend the path of light.
Hence no cosmic acceleration, no dark energy, no un accounted for dark matter, no big bang, this universe is eternal, no beginning or ending. Cosmic background microwaves are just distant galaxies who's light has been gravitationally distorted beyond your visible spectrum.
Galaxies exchange and recycle energy and birth new stars out of old dead ones.