Terence Tao: The Cosmic Distance Ladder, UCLA

[@SalesforceUSA]

Tao is a very good communicator. Modest, fluent, responsive, considered, honest, and humorous. Very good person, a great scholar and a gentleman to the core.

[@greg55666]

This was really cool because it has utterly nothing to do with what he does for a living; it was just a history lecture anyone could have given, but it was totally fascinating from beginning to end.

[@powerfulwords]

Best lecture I've seen in some time - so clear and helpful in understanding the history & development in understanding distances in space. Thank you!

[@tthtlc]

This talk is a classic how to give a speech lesson: Know your audience well, and choose your topic carefully. This content is all new to me, because I am not into astrophysics or astronomy. For an audience of mathematician, choosing a mathemtically related story and content will have bored the audience to DEATH as it may have been heard so many times.

[@tysswe1]

He seems like such a nice person. One of those you would like to hang out with. Not like does wannabees like langan who thinks that they are so smart and look down on others. This guy reminds me of dr daniel jacksson of stargate!

[@hubomba]

Guy is super productive as a mathematician. Go check out his blog and all of the paper's he spits out. He has won a fields medal back in 2006 and in 2012 he proved that every odd number greater than 1 is the sum of at most five primes,without invoking the Riemann Hypothesis. This helps improve the status on proving Weak Goldbach's. The purpose of this lecture was obviously for the general public and more as a science history talk.

[@jamesbirchall3725]

terrytao.wordpress.com/

[@Phoniv]

"your two eyes can work out distance to objects" Most brilliant comment by Dr. Tao, evidence that the mind works like a computer. The rest of the lecture was also very enlightening!

[@billyjojo6690]

Only in arms distance. This is learned.

[@andychong5984]

From a mathematician! Absolutely brilliant

[@flippinrawks]

"astronomers would kill for 8% accuracy"-Terence Tao

[@dharmendrasinghazadhindust7186]

Meaning???

[@williamliamsmith4923]

DHARMENDRA SINGH AZAD HINDUSTANI आजकल astronomer’s accuracy is much lesser - even with all the technology (because even though the technology is good because we are dealing with much farther objects)

[@kellymoses8566]

@@dharmendrasinghazadhindust7186 Things astronomers study are so far away it is hard to get really accurate numbers.

[@BlancaParraMosqueda]

Was great!! He really can communicate this to every one!

[@DrakeLarson-js9px]

A classical, historical lecture.- well done.

[@greg55666]

The story about Kepler figuring out the orbit of Mars gave me goosebumps.

[@aoeu256]

You have to something similar to figure out string theory though...

[@taufiqutomo]

Something that is simple, something i learn and relearn multiple times, yet repeatedly fail to do it myself when the situation arises. One of the basic problem solving principles. *If there is repetition, look for what does not change!*

[@Emdee5632]

Carl Sagan, in his book and TV series ''Cosmos'' (not the 2014 series presented by Neil DeGrasse Tyson but the 1980 one) also tells the story how Johannes Kepler, using Tycho Brahe's calculations, discovers the orbit of Mars is an elipse. It's episode 3, Harmony of the Worlds.

[@greg55666]

@@Emdee5632 Yes, I know, but I think Terence told the story better here.

[@maxwang2537]

This is an amazing talk! Man, treasure and so interesting!

[@drted]

Starts @5:45

[@MagicmathmandarinOrg]

Amazing! The presentation is as incredible as anything there can be. “Mathematics is the most beautiful and most powerful creation of the human spirit.” Banach Stefan “God used beautiful mathematics in creating the world.” - Paul Dirac

[@life42theuniverse]

By Wikipedia human reaction time is about 200 ms ... so 45:00 Newtons experiment likely recorded < .5 sec regardless of distance.

[@DeepBlueChannel]

The moon distance equation at 22:26 gives (D = 71.3 r) not (D = 60 r) 2r / 3hr = 2pi*D / 1 month 1 lunar month = 28 days, in hours 28*24 = 672 hr so: 2r / 3hr = 2pi*D / (672hr) => D = 2r * (672/3) * (1/2pi) => D = 71.3 r

[@summersun-t4y]

So why Tao put the value D=60r ???

[@meepk633]

Quick! Someone get this man a tailor!

[@20891]

Michael McDonald whats wrong with his

[@jaggar28]

That's a very stupid comment.

[@domtgtheonly1]

@@jaggar28 lol

[@aleratz]

He is an amazing communicator

[@cmoeinc]

I am really impressed with that. Thank you for showing us that.

[@rodovre]

Skip intro blabla: 05:40

[@iambiggus]

rodovre Ty.

[@adrianf.5847]

OK, since the mistake appears twice, let me write one or two lines. Physicists count every object that would now be up to 93/2 gly away and can be seen through a telescope as part of the observable universe. This is because it would now be at most this distance away and is now observable, even though its light was emitted when it was much closer to the matter of which we are comprised.

[@oker59]

@oker59 Newton didn't derive his inverse square law from keplers laws; he derived Kepler's laws from his inverse square law; it's the seminal problem to solve in classical mechanics before you get into say chemistry, electromagnetism and so on.

[@skyadriana5419]

no problem, I found it. He measured the shadow length a few times around 12:00 o'clock and took the average. Then he made a triangle with right angle between gnomon stick and shadow(measured avg. length). Then he used this to find the angle X between the hypotenuse and the gnomon stick. Then he found 7 degrees is the difference between 90(angle at Syene ) and X (angle he just measured at Alexandria). Then he used cosine theorem for triangle with 2sides R(&7deg.), distance(Alexandria->Syene=5000)

[@TimondeNood]

Amazing insights and amazing talk, thank you so much for sharing this!

[@skyadriana5419]

I mean - lastly, in order to find Radius of the Earth, he used cosine theorem for the Earth triangle: two equal sides R = Earth's radius; and 7degrees angle in between them. And third triangle side = 5000 stadii(which is distance between Alexandria and Syene)

[@skyadriana5419]

You are most welcome, oker59! I only listened to Tao and tried to figure out the 'simple math' he is referring to. I read how gnomon is used and based on that I made my assumption how exactly Eratosthenes used the gnomon to calculate Radius of the Earth. Circumference of the Earth as you mention can easily be calculated using 2 X Pi X R.

[@RaggedM88]

Great lecture.

[@adrianf.5847]

Even if the Moon was flat, there would still be differences in the brightness of the Moon. This is because when close to perpendicular to the Sun, it is hit by less light which it could reflect, even if we assume very strong diffraction.

[@alphabetacanton]

Like Paul Erdos, Prfessor Tao also noticed the "epsilon (child"" first.

[@RajivKumar-ee7xv]

He mentioned observable universe to be 78 billion LY now we know it is 93 billion LY. What more we fount out within last 10 years

[@cesteres]

Nah it's just inflation.

[@missh1774]

It always facinated me that Jupiter had a moon named Io. I think all its moons are fascinating.

[@pattystomper1]

I have a question: I learned that DISTANCE itself is now calibrated by the speed of light. For example, let's say we know that the speed of light is 186,000 miles per second. And we know that a laser takes 2 seconds to bounce back from the moon. Therefore, the moon is 186,000 miles away (one second to get to the moon, and one second to return = 2 seconds). * rounded off for simplicity. However, if we were to measure the distance using trigonometry, and calculated the distance as 185,000 miles, then we would have to redefine our definition of a mile in order to make that number match 186,000 miles. How would such a variance affect our estimated measurements to distant galaxies?

[@trogdorstrngbd]

The definitions for units are nowadays never changed that drastically because we have ways to measure these quantities very accurately. Your hypothetical situation also wouldn't have any effect on the definition of a mile because we don't define it based on the distance to the moon, but by the distance traveled by light in a fixed amount of time, which is itself defined by the emission frequency of cesium-133. Regardless, any definition-based effects on lengths as large and imprecise as those in astrophysics would be negligible.

[@DrakeLarson-js9px]

But at Minute 1:05:34 Terence describes 'The Big Bang' as a 'given' while I would advocate it as possibly a semi-misguided conjecture! (An internal UCLA debate initiation?)

[@skyadriana5419]

Everything sounds great but I am not getting Tao's results with this input data - for Moon radius and distance to the Moon. They are way too different. With his data, also distance to the Sun is 11 times Sun Radius - completely wrong result compared to Tao's presentation slides(20 times). Did anybody try to reproduce Tao's results and are you duplicating his results successfully?

[@oker59]

Hello Sky Adriana, the volume isn't working on my computer right now, so I don't feel like rewatching this right now; but, right off the top of my head, the Gnomon was used for sundials.

[@TheBobbyboy64]

54:09 Distance to Proxima Centauri should be ~ 25 trillion miles, not 25 billion....

[@thangnguyen02]

it's only a couple letters off. Eh, it's fine.

[@DiapaYY]

It depends on the system you're using en.wikipedia.org/wiki/Long_and_short_scales

[@oker59]

. . . or who generalised the sundial. I reread the section on Erastothenes, and it makes no mention of sundials(as I thought; for some reason, my memory kept saying Appollonius). I looked up the index sundials and gnomons and I can't find anything. I'm sorry, but right now, i've dived back into comparative mythology; this time "The Golden Bough"; i tried for years to avoid reading this book; i hope to be done with it quickly enough and back to reading/thinking about mathematics.

[@jonnie303]

On Kepler - "If Einstein calls you a genius you're really doing well"

[@Robinsonero]

If aristarchus concluded the the earth orbited the sun after computing its size and distance, how did he know to look for a difference between the half moon phase and the midpoint the quarter turn in it's orbit from the new moon? The diagram Tao shows for that calculation (where he shows the distinction between half way between the full and new moon and the actual observed half moon) already has the earth on a curved orbit around the sun. Put another way, wouldn't aristarchus have had to presuppose a heliocentric model to look for the difference between half the moons orbit and the point at which the earth and moons orbit meet at a right angle?

[@randomhandle422]

No, all you need to know is that the sun is what lights up the moon and earth.

[@oker59]

Fascinating Adriana, I had only guessed from memory of reading Thomas Heath's "A History of Greek Mathematics." What else comes to my memory but I didn't bother remarking because the memory feels to faint is that it was Appollonius who did the gnomon generalisation of the sundial. Is this who? It's fascinating the gnomon calibrations of the sundial that you find; Erastothenes figured out the circumference fo the Earth from the shadows indicated at the same time in both Alexandria and Syene!

[@adrianf.5847]

Actually, Prof. Tao saying that GPS uses triangulation is a major howler too.

[@DeepBlueChannel]

A question though: how did the ancient Greek measure time at night when them measured the Lunar eclipse period of 3 hours?!

[@Emdee5632]

I believe they already had hourglasses.

[@aaroncanterbury8371]

I actually think I'd enjoy conversing with Tao, I love learning new things, also he seems like a cool guy to me, He's more understandable then most speakers.

[@aaroncanterbury8371]

Eratosthenes actually paid scholars btw to accurately measure there paces, he paid several to collect the average counted paces, they had to been the same height and where accounted in to the earths radius, merchants weren't reliable at that time as they won't count there paces when trading. So inaccurate, but I'm glad he said something similar to the idea of how he measured the distance.

[@hubomba]

"How long did it take you to get the field's badge." Hehehe.

[@skyadriana5419]

OK sure oker59! Then if you have inspiration and find out what is the correct way that Eratosthenes did the math(especially without PI) I would be very glad to read that!

[@skyadriana5419]

I wonder how in this case exactly, step by step, the gnomon was used.

[@oker59]

@oker59 He(Terrence) calls them peasants!(those who helped Brahe on his astronomical observatory island). Carl Sagan called them "hangers ons"! There's pictures that show that one of them was indeed a midget. Tycho Brahe's 'helpers' were indeed 'characters.'

[@oker59]

Of course, you've watched the video; i'm sure you've hit on the connection between this sundial work and maybe Erastothenes calculation of the circumference of the Earth. Alright, I'll go try to look it up; thanks again Adriana!

[@oker59]

I remember doing the simple math of Erastothenes calculation of the circumference of the Earth; you don't even need Pi! Still, you're showing pretty good mathematical ability. I must say your saying to measure the shadow length and find the average doesn't sound like something Erastothenes or anybody back then would do! Not to mention the use of trigonometry; well, maybe later after Erastothenes. Anyways, I looked up Heath's "A History of Greek Mathematics" and couldn't find who did . . .

[@jr800w]

I learnt his trick.....never stay still

[@edogawa0saki]

he s so great!

[@Kanishka-b6p]

All flat earth believers should watch 11:20

[@Emdee5632]

Flattards done care about facts.

[@abdonecbishop]

excellent

[@albertuskundratis1]

Beautiful Presentation! "Climacteric": A Period in human life in which a Change takes place in The Constitution"-a definition from Webster's Standard Dictionary, a yellow-clad hard copy edition from 1970 which I always remember! CLIMACTERIC is derived from KLIMAKTERIKOS-"Rung of a Ladder" in Greek! Hence THE CLIMACTERIC PAPERS, a Future Compilation like THE FEDERALIST PAPERS(On the U.S. Constitution)? See "TWENTY THREE PROPOSALS"-by Larry Sabato JR. Today as I'm commenting this, it's September

[@Dultmaster]

You can fit two or three terry taos in his suit

[@neoloaded]

Terence starts @5:56

[@HoaTran-om9eq]

The best mathematician in the world wins Clay millenium award in 2019

[@Aanthanur]

very very nice

[@what_on_arth]

Watch at 75% speed.

[@jimjimakos1101]

Give us knowledge big mathematical legend terence tao

[@skyw9857]

Brilliant!

[@clonebin0]

anyone watching this in 2021?

[@Emdee5632]

Yes.

[@davidwilkie9551]

"Distance Ladder" is what you see of prime-cofactor frequency density-intensity, axial-tangential harmonic alignment, holographic integration.., or "Standing Wave-packaging", etc, etc.

[@JashanTaggar]

My man needs a fresh high fade

[@JMUDoc]

OK - who brought a BABY? Selfish.

[@iambiggus]

JMUDoc it’s like a baby in a bar. No reason it can’t be there, but you know at some point it’s gonna kill the mood.

[@photovi]

If math is so important and measurements so precise it’s odd this man would not purchase the correct size suit

[@OakQueso]

You just absolutely demolished the best mathematician in the world. His career is over with.

[@albertuskundratis1]

#1) N.B. Kepler's Three Planetary Laws!: "DUC ORBI HARMONIA!" (Lead to a Planet by Harmony of Movement); HH-GG-NN: ANARCTIC "R"! Anagrammed letter for letter from "Shaler Running Back BRANDON LEHMEIER runs through a Play at Practice." (See the Pittsburgh Post Gazette, 2000)

[@NameforYouT]

@sanjeevbvideos I hope you are not worshiping a triangle. And your point: There are certain principles found in Indian texts. The complete picture is always absent and the non-simple language you are probably talking about is Sanskrit and all these were not found. Moreover, if it indeed they are present and if they are the same thing, we don't need somebody to spell them out to like this in simple language.

[@harshavardhanasrinivasan3125]

Wow i wish I could be your math student

[@birkandundar4503]

Thanks ..

[@CaribbeanMischief]

He could use a tailor.

[@sandranosocialism1780]

There's always a little bit social awkwardness. One could almost use that for interviews

[@uhnp]

Earth is round was known to Hindus long before Aristotle. It's mentioned in Vegas.

[@12121sk]

1:05:30 WOW!

[@justamanofculture12]

Cosmic distance ladder? I can't even draw ladder in my house 😂

[@TheElephantOpera]

@openuniverse2003 Dude, he's just telling a story, not making an advanced technical talk. And fyi, Dr. Tao is considered one of the greatest living mathematicians. You don't need to lock yourself in an ivory tower to be a great mind. Some people also enjoy educating others.

[@Reds_Garage]

Can someone give me aspirin please

[@shaneroberg309]

IN THE MIDDLE OF THE WORD BELIEVE IS THE WORD "LIE".

[@thangnguyen02]

I'm surprised that a math guy could answer the astronomy questions so well. But then, his IQ is awesome.

[@matthewroazen4476]

But then again, isn't astrophysics 95% math?

[@restybal]

He reminds me of Carl Sagan.

[@oker59]

the history of the Gnomon is deeper than Tao shows here(I'd like to think he knows this).

[@all462]

There is only so much to fit in 1 hour talk.

[@gaaraofddarkness]

9:00 who brings a toddler to such a talk ?!? It's so annoying.

[@brainstormingsharing1309]

👍👍👍👍👍👍👍👍👍

[@Drgoulu]

Tao is certainly a very talented mathematician, but definitely not a good communicator. Wish this very interesting topic was presented by someone like Brian Cox...

[@shoopinc]

Dr. Goulu problem is Brian Cox isn't much of a mathematician

[@B1ankeys]

Nope.

[@albertuskundratis1]

It's September 17, 2012 6:49 17 seconds pm CONSTITUTION DAY within Constitution Week! #23) N.B."TWENTY THREE PROPOSALS" A Hand RUNG'R- an "I.N.R.I. Era" B(oo)k. "H.M. Hal I C Race'ng!

[@DaitoRyuDeshi]

or Astronomy of the Hindus. (Ancient Indian mathematics was based on Astronomy) !

[@judclark7376]

Extra credit 7b woooohoooooo.

[@officialEricBG]

fields badge LMFAO

[@scotttimms5117]

God Dam,im so Dumb

[@gongz3661]

António Salgueiro > Terence Tao

[@jeromekwasniowski8293]

✌️♎️

[@albertaoridge]

Why would anyone bring a toddler to this? What is wrong with people?

[@shaneroberg309]

LEMMING

[@jollyjokress3852]

What I predict: I understand the first two slides then I will just give up understanding ;)

[@Onoma314]

The lunisolar year ( 365.24)multiplied by the stellar year (360) multiplied by 1,000 gives you Earth's exact equatorial circumference in feet Both year lengths are from Sumerian calendars This method yields Earth's equatorial circumference = 0.00512766% difference from the actual circumference FAR more accurate than Eratosthenes, and using a system FAR older Try again, professor

[@MegaTp4]

The foot as defined today is not old at all. Try again Jesus

[@Onoma314]

Then I invite you to my forum to see how little you actually know about this topic That goes for any of you " mathematicians " secretsoftheages.freeforums.net/board/1/general-discussion

[@mikefullermikefuller4711]

I am Very, Very Intelligent too.

[@XBlack-oc6xt]

yeah, me too, I have iphone

[@alphabetacanton]

Stop touching your chin Professor!!

[@AbdulHadi-hs1uf]

This dude need to relax ?

[@Onoma314]

One whole month and no progress with a simple passage from Plato ? Lol

[@ivanjelenic5627]

bitch please, stop looking for attention to validate yourself. it's not our problem that you're insecure.

[@Onoma314]

Ivan Jelenic Calm down, you don't want to soil your panties