I never understood how cosmology worked...until now!

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Henrietta Swan Leavitt, an American astronomer hired as human computer made a startling discovery. Not only did it help humanity realise that the universe is teeming with billions of galaxies, but it led Edwin Hubble to eventually discover that the universe must be expanding, eventually leading to the big bang theory. The entire paradigm shift is centered around her discovery. But what exactly did she discover?

Chapters

00:00 The astronomer who made a startling discovery
01:07 Einstein's cosmological constant
02:54 Friedmann's counter argument against the constant
04:00 Vesto Slipher's puzzling discovery of the spiral 'nebulae'
07:40 The best measuring methods until the 1920s
09:04 A serious upgrade
10:50 Henrietta Levitt enters the story (Levitt's Law)
16:15 The paradigm shifts after Levitt's law
17:50 The Hubble Law
20:38 Einstein's blunder, or was it?

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[korporalkarrot]

Man you are one of the best science communicators.

[random-gcdc]

We need teachers like you so that kids can be curious to ask more questions and seek for more answers. Honestly it's hard to believe that kids/people nowadays have access of such content for free and readily accessible.

[Govstuff]

This presentation is needed to be shared to the people that don't understand how science works. Some don't believe because they can't fathom it took a team of scientists not all working together. But sharing what they know so we progress over time and now stand at the edge of new discoveries .
Great job.

[rishan_sir]

Long Before discovering your channel, I watched your khan academy lecture on magnetic hysteresis. That lecture was definitely the best lecture I have ever attended. It helped me a lot to become better teacher for my students. So one day I was binge watching your videos and suddenly I realised you are the same person who taught me about hysteresis! Very delightful experience. Keep making videos ❤

[ConnoisseurOfExistence]

1. How did Slipher know that the spiral nebulae are red shifted, instead of just red?
2. How did Leavitt know that all chepheid variables that she was observing (the ones in the Magelanic cloud) are at the same distance? Just because 2 objects in the sky look closer to each other, it does not mean that they're actually close together. In fact, 2 stars on the opposite sides of the sky can be actually closer to each other, than 2 that look in the the same direction from us...

[FailSpace]

Dudes you’re one of the best science educators to ever be on this platform. You make physics and astronomy so easy and intuitive to understand. Thank you for all of the work you do, Mahesh!

[mtthwsbg]

literally learned about 75% of the terms you introduced in this video i learned in my astrophysics 2 class that started this semester (about jan 12) so its crazy how im learning about all these new crazy concepts and you just so happen to make a video covering the same ideas and clearing up any confusion i ever had, reinforcing my pre-existing understandings, and teaching me so much more ❤ love the vids!!!

[CaciqueTaino]

Love your videos and this one was no exception. Not sure if you take requests, but would love for you to cover the Andromeda Paradox that is doing the rounds. You partly cover it in past videos but this one has a few more elements like being in the same place and same “time” yet different results.

[Grandy_UiD]

Vesto Slipher has gotta be one of the most badass names I've ever heard.

[sgiri]

Thats incredible to have you back with a cool content.

[arkadia_]

Thank you a lot for mentioning Slipher!! When i learned about him i simply realized that for the sake of giving a single person's name to a scientific law, you end up forgetting a lot of the people that came before and will never be remembered.
Scientific discoveries are a product of humanity not of a single person, we keep forgetting that, specially in these days.

[zeropointenergy]

Leavitt was described as "hardworking and serious" but that "she had the happy, joyful, faculty of appreciating all that was worthy and lovable in others, and was possessed of a nature so full of sunshine that, to her, all of life became beautiful and full of meaning."

[lalit-_-]

I am waiting for your video for a long time 😭

[perkuperku]

Could you also someday talk about how galaxies were discovered in the first place? It's so interesting and exciting to learn about the actual journey to the discovery rather than the fact itself. I love your way of storytelling and arriving so naturally at the final conclusion. It must take so much care and effort for preparing that. Thank you <3

[Its_x_Kai]

I was watching Rajan Chopra's Video on fake Educational influencer and in its comments many of them were really appreciating your videos on how you explain every thing using mathmatical expression and your awesome intuition on complex topics.

[ashmon]

The way you explain the things in your videos is amazing

[Durgasanthoshi-ur]

14:47 graph:curvy ups and downs
Physics: oh that's a straight line

[RGF]

Thanks for giving credit to Henrietta Leavitt for her contribution to astronomy. BTW, the correct pronunciation of “Cepheid” is “seh-fee-id”. These pulsating type stars were first observed in the 1780’s in the constellation “Cepheus” which is pronounced “seh-fee-us”. These variable stars were named for this constellation.

[gwenwalravens]

This channel is fantastic. Complex concepts are explained in a way everyone can comprehend. He needs more subscribers and more videos 🙂

[Yacello]

Don't be a jerk. 😂 (Jerk = d^3x/dt^3)