3. The Doppler Effect and Special Relativity

MIT 8.286 The Early Universe, Fall 2013
Instructor: Alan Guth

In this lecture, the professor discussed the doppler effect, time dilation, Lorentz-Fitzgerald contraction and relativity of simultaneity.

License: Creative Commons BY-NC-SA

[mariusz]

So amusing watching this genius perform elementary algebraic operations on the blackboard. I'm grateful to MIT for making Alan's lectures available online.

[macieyid]

This lecture is a treasure. The example presented during the first 20 minutes is how every introduction to relativity should look like. If, like me, you're still not clear on how the non-intuitive stuff about photons fits together, watch this.

[gnasty]

These videos are a gift and I thank for them

[ShubhamBhushanCC]

The dude who asked the Galilean Relativity question is a genius. I never thought of it but now when I worked it out, it blew my mind. Damn!!! Physics is beautiful

[mubarakhussain]

Its a profound lecture by one of the greatest contemporary minds.

[mg-ilkm]

Great lecture. Very clear and to the point. Thank you!

[FelipeBl]

I like the very simple example in around 30:00 about time dilation and light arriving to an observer in a different frame of reference than of the source. Very clarifying

[brainstormingsharing]

Absolutely well done and definitely keep it up!!! 👍👍👍👍👍

[abdou_belounis]

Everyone must know this channel exists.

[aliasanon]

It is a complicated by interesting subject. A great and suitable for the job professor by the way with a deep theoretical understanding

[CrownOfGoldCompleatSacrifice_]

It appears we may not be getting it but as our thoughts change and it takes time to get to full understanding, they are past your life cycles so the change is instant

[laszlogmeszaros]

Hywel 4 is correct. Someone is finally out there, who is willing to think. It's great.

[philoso]

Page 24:00 regarding Aether.
Albert Michelson and Albert Einstein didn’t (know or scrutinize) enough of the principle of operation in the apparatus employ in light speed measurement which is “incapable” of determining presence of Aether or not, consequently declare that Aether do not exist ... by ignorance.

[CrownOfGoldCompleatSacrifice_]

System progressing two failed attempts at going back to the things before. On different note. At the end of last month I felt great and was ready to progress

[adurgh]

The only sticking point for me was the discussion about accelerating clocks. The effect of time dilation has to do with the time dimension as measured by any means, and a particular clock design is irrelevant, so the physical effects of acceleration on an actual clock being the motivation to introduce the concept of "ideal clock" seems unnecessary; even confusing to me.

[sscheinfe]

he has the most elegant chalk handwriting I have ever seen. just sayin.

[richardsmith]

Did he state the clock difference equation incorrectly at time 1:07:27, when he talks about simultaneity. He seems to state the clock difference is βLC, and it should be βL/C. The term is shown correctly in the slide.

[saritchauhan]

Why delta time prime( ∆t’ as he pronounced) can't be equal to delta time sub source (∆ts) when both are in same inertial frame for moving observer case. He himself says that stationary source and the screen(or we) are both in same inertial reference frame when asked by a girl at 46:08

[manish__kumar]

What effect on the length of rod when it moving with velocity(v) in incline way (note : not is horizontal or vertical) rod moving in downward or upward direction... is its length change or no any effect shown.

[Powerify]

Things being said between 46:56 - 47:09 is wrong. The equation implies exactly the opposite of what's being said...