動画数：214件
(James ) God doesn't get tempted
Timothy ) God doesn't die(Hebrews 5:7) Jesus needed salvation
(John ) Jesus was seen
- Intro
-second) refresher on the Doppler effect to remind viewers how observed red shift translates via Hubble’s Law to estimate distance; but far more “mind-boggling” than the “scale of the universe” mentioned at is how a single human individual can plan, storyboard, design, code, render, edit, produce, and post-edit based on feedback from Patreon supporters a 25+-minute video of this depth, breadth, and scale in 2 Earth weeks :O
- Distance to Venus
uncover for Britain
this is the best animation I’ve ever seen to describe the parallax on a global scale. Really clean and clear 👍
That's the most earthy earth I have ever seen
At , that visualization showing the moon’s orbit as it pans out to show Venus’s orbit - no space visualization or metaphor has illustrated the distance quite as effectively as this. Fantastic job. Now I want to see everything else in terms of moon-earth distances
the north and south examples seem to be reversed in this one
measuring the duration of the transit is such a beautiful solution
I knew the Guillaume Le Gentil story! from Vsauce's "How People Disappear" from 2013
To say he was done dirty would be such an understatement...
You can't just tell a tragic story of a man and cut it off right after telling it like that! 😂
On a side note, casually exposing a man's scandal without real purpose was such a stray. 😂
- Speed of light
I'm a bit puzzled by how the computation of the speed of light was derived from Romer's observation of Io's period @ . Why does the longer distance mean an increase in Io's revolution period? Isn't that distance applied to every cycle? I was thinking more of a doppler-like effect, but I feel like I'm missing something.
"It's whippin" 🌝💨
what a circle! 👏
If at like it says the moon took 20min longer total, not just a later start-finish(which was probably what he(mr Tao)meant ), then this would not mean a speed of light diff or indication situation, but that the 0.01(or whatever)percent of light that was bouncing off the tiny distant planet and coming back to earth, had a greater arc of the same < to cover on the far side... the observer on earth would see a greater amount of the light reflected because of the greater arc. I think anyway...edit(seems like it should be less than 20min based on this alone(arc diff thing-), such a small change front-to-back over the total distance(very large)).
At the implication that I got at first was that the Earth being farther away from Jupiter causes Io to appear 20m later because light has to traverse two extra AUs. But Io also disappears from view 20min later because of the same delay. So the total eclipse time shouldn't change. In case anyone else is confused by it: what it describes, I think, is that when we're closest to Jupiter we calculate the schedule of when Io's eclipses happen for half a year later. Then we wait half a year and look at Io and measure how far off our calculations were, which gives us the speed of light.
Clever indeed. My exact same reaction. Haha.I'm quite amazed at how accurate their instruments were at the time. I think I understand parallax, but if I would time travel I could not build those instruments back in the day. But I have learned through this vid they used women as computers!! That's hilarious. Who knew? (They also used women for calculations for the Apollo missions if I'm not mistaken. Correct me if I'm wrong.)
imo this is the most profound moment so far in the video. Would make a great short. Seeing light perform its journey in real time across the celestial distances is... Absurd. Because it is such an instant phenomenon to the casual observer. Outstanding video and interview.
Seeing the speed of light in action at between various celestial bodies is mind-blowing. That simple animation is worth thousands of words.
- Nearby stars
wait I don't understand. I mean I get how impressive that is, but it's so impressive that now I really want to know HOW they were able to measure the angle of a dime a mile away! 🤯
- The Milky Way
the cameraman gets turned to jelly by the Tao-Beam
Can a star can beso distant so we can not observe any photons from it, because it's apparent brightness is so spread out?And if yes, what's that distance? I imagine it to be extreeeeeme
more intuitive if you label the X axis as wavelength instead of frequency.
as an astronomy student, I got embarrassingly excited when I realized Grant was going to show a HR diagram here. great video! ❤
@ Why does the plot of color vs absolute brightness look like the 3rd dimension of the Mandelbrot set?
seeing all those Billions n Billions of stars that are crammed into every pixel of our screen within the galaxy, yet, they're so far apart in reality its so mind boggling. We see no spread in the imagery, yet in reality it would be nearly only spread.
What is the technique at called? Also two great videos you’ve made, and also also Kepler was a genius.
And then at ... the painting animation... so awesome
Just making sure I'm thinking about this correctly. You can determine the type of star from the variations in the wavelengths it releases. Then with those wavelengths, you can estimate the absolute brightness of the star. Then you can use the apparent brightness and absolute brightness to calculate the distance?
Can we really measure the entire Milky Way with this method?
- Nearby Galaxies
is actually the year that Henrietta Leavitt published her results, and that is the only step I knew from the start because of the Lost Women of Science podcast 🙌
I’ve rewatched the part at so much. I still don’t get it. The observations just showed that brighter cepheids had longer periods. So if you know the period, you know it’s brighter than others but how do you know absolute brightness where you can use inverse square law?
- Distant Galaxies
Was Hubble the one to discover the redshift of galaxies?
- I was able to track everything up until: "...general relativity predicts that the universe is expanding at a uniform rate. The further away things are, the more they recede and the more red shift they have."
When Terrance was talking about the receding universe, he said that the further away bodies are, the faster they recede. How do we know that it is receding faster (either absolutely or relative to us observing it)? Is it some sort of coaxial parallax?
Does general relativity alone predict a uniformly expanding universe?
Great video as always, learnt a lot. Minor nitpick at . General relativity doesn't predict an expanding universe per se. Einstein's field equations simply permit an ad-hoc addition of a scalar field, the cosmological constant (lambda), that we use to explain dark energy and the expanding universe. There are other theories out there that are perfectly consistent with lambda-free GR
Loved the starwars reference at
And at , the star wars text animation 😆
galaxy far far away,where jedi council tried to save the day😂
he couldn't hold himself enough not to include this awesome reference there 😂
Star Wars! 😀
Is Hubble’s original law sufficiently accurate to allow for good measurements of distances at the scale of the observable universe?
"The observable universe is, we think, about 20 percent of the whole universe..." This is-- by far-- the most extraordinary claim of the entire video, and yet there is no reference or follow up. Any clue where this comes from?
"We think the observable universe is 20% of the entire universe, we don't know." I've never heard this before.
At , Tao says we think the observable universe is ~20% of the whole universe. What evidence do we have that supports that (even though we don't actually know)? I thought the prevailing theory was that the universe is infinite.
This is the first I'm hearing for an estimate of the proportion of the entire universe taken by the observable universe. Would very much like to know more about that "maybe 20%, we think" reasoning. Great video!
"Observable Universe is 20% of the whole Universe" caught me by surprise. Where does it come from?
At Terence Tao says that the observable universe is about 20% of the entire universe. I looked through his corrections for this video on his blog and he states "The 20% number was a guess based on my vague recollection of these works, but there is no consensus currently on what the ratio truly is".
Where did this guess of the observable universe being about 20% of the full universe come from?
it is so so humbling 🥶
it had never occurred to me too consider what percentage the observable universe is of the universe as a whole 🌌 hearing 20 per cent shocked me for some reason.
The disk of our own galaxy obscures what we can see, so that entire middle section that appears empty will remain unknown to us.
- Lingering mysteries
Camera felt a collision there 😂😂
Is there any keyword we can search for further explanations or research on the 10% anomaly? This is very interesting and I would like to learn more.
If you length contract with relativistic effects, do light wave lengths change?
How comforting to hear this guy laugh.I had a friend, so super intelligent he taught himself calculus from a book so he could write computer code, he never laughed.Every conversation I had with him I could see his discomfort with a pointless human interaction.
Tao’s laugh is delightful
"You Say Long Names Are Tricky But All I Hear Is Sempai Noticed Me" lol
The lighting seems correct to me. I think you are mistaking other consequences of the visualization for shadows. Half of the Earth is being rendered as transparent ().
For two frames there is a strange artefact on the left hand side.
- About Terence Tao and the Distance Ladder
I love how instead of a pi, Tao is a tau :)
I love you used Tau to represent Terrence Tao lol
the Tau creature lore drop was not one I was expecting today
Tao is Tau, nice
This 👌
I feel like explaining the “how” is what makes it memorable
- Earth
thought you were gonna say “which this margin is too narrow to contain” 😅
How ancient astronomers reasoned step by step to conclude that the Earth passed through the shadow of the Moon and not another planet in the solar system ?
Flat earthers at "Wait, that's illegal"
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anyone else seeing the cool illusion that when you shake your phone, the dark moons in the middle seem to jiggle around?
the animation!!
“Cinema is the ultimate pervert art-form: It doesn’t give you what you desire, it teaches you how to desire.”
brown The question of in my pov is a hint at how much more knowledgeable people in the antique were. The vast distance was in some circles most likely a common place, the picture the surviving written traditions give us is necessarily very incomplete.
* How did Eratosthenes know that the Sun was so far away that its light rays were close to parallel?
I read that in cosmos by Carl sagan
at as the earth rotate we will also have a circular arc of places where the sun will be completely overhead on that day so that effect will be happening everyday what so great in tropic of cancer also at
* is it completely accurate to say that on the summer solstice, the Earth's axis of rotation is tilted "directly towards the Sun"?
Thankyou very much Grant but I still have one more doubt I am confused at what you said that when the earth's axis is in direction toward sun , then the line passing through earth center and sun will be passing through somewhere at north pole as seen in video at so if this is the case then if the earth rotates on its axis on solistic day then the line joining earth's center and sun will cross this one point I.e north pole so How is this tropic of cancer is formed ??? Shouldn't there be a single point instead of whole circle of tropic of cancer....❤btw loved the video...just beautiful
i am very confused becz how grant created that circular arc if the sun is in the same line of axis then at a single point in northen hemisphere there should be sun overhead from where does the tropic of cancer comes ??? i am very confused...
*northern hemisphere* summer solstice --> Tropic of Cancer. (for the southern hemisphere summer solstice in December it would be the Tropic of Capricorn)
* Wait, aren't there two tropics? The tropic of Cancer and the tropic of Capricorn?
* I thought the Earth wasn't a perfect sphere. Does this affect this calculation?
At you say the measurement of the circumference of the Earth is "pretty good with no technology", but Eratosthenes wouldn't have been able to measure the 7 degree angle without the gnomon, a piece of technology.
* Are the riverboat merchants and the "grad student" the leading theories for how Eratosthenes measured the distance from Alexandria to Syene?
The grad student joke really cracked me up XD
it's so wholesome to hear his "belly laugh"
Prof Tao's ominous laughter while joking about graduate students doing manual labor hits a little different, as a graduate student myself 💀😂
His laugh 😆🙏🏼
The Pure Laughter of Education-Ladder Humor ❤
That's exactly how I would expect a great mathematician to laugh
the nerd laughter is a mathematical proof that Terence Tao is a genius.
The most common theory today about measuring this distance is the use of Bematists, counting camels steps to measure distances. Camels are known to have a very constant step distance.
- Moon
At : the method used to measure the Moon's radius assumes that the Sun is at a much larger distance than the Moon itself, so that the Earth's shadow (umbra) doesn't converge. So the Moon radius has been estimated after the Sun distance......Very nice video!
Question at , how do we know that the size of the shadow of earth is twice the radius of the earth?Are we approximating that the sun is infinitely far away so all sunrays are parallel?
* How long is a "lunar month" in this context? Is it really 28 days?
Correct me if I am wrong but I believe the scanning animation at is actually going the wrong direction. Since the Earth rotates counter-clockwise (from "above") then we would see the "top" side of the moon first
If that is the case, is the animation from to
minutes, because the Moon rotates in the same direction as the spinning of Earth around its axis. The animation therefore is also moving in the wrong direction as well (related to this, the line of sight is covering up the Moon in the wrong direction to the Moon rising at around ).
I don't think it's right. looking down from the north pole, both earth rotation and moon revolution are counter clockwise.And it's widely know moon rises 50 minutes later each passing day, means it takes longer than 24 hours.
And shouldn't the line of sight animation at also rotate counter-clockwise?
It’s slightly more, not less. The moon rotates around Earth from west to east, same direction as our own rotation around the Axis
Correct me if I am wrong, but at , it's actually slightly *more* (not less as said by Dr. Tao)... It takes the moon 24 hours and 50 minutes between moon rise to the next moon rise.
* Is the time taken for the Moon to complete an observed rotation around the Earth slightly less than 24 hours as claimed?
Animation at seems to show the moon going in a retrograde orbit which is not how it actually orbits the earth.
correct? Because line of sight is scanning over the moon clockwise and moon is moving anti clockwise. Nevertheless, fantastic video, among the best on YT in general. .Just before posting this I noticed that Mr Tao posted a link (first comment) with Q&A with corrections and explanations where this is also clarified.
- Sun
I love how it does not just say “not to scale” but rather “not remotely to scale” even when it is more accurate than most science text books.
τ has such a concise way of speaking
This is why I Love learning new things.. was watching the background and have always wondered how people figured this out. At I yelled out "I see" when you moved the right angle.. I got it.
"as your lovely illustration will show" how nice that he has so much confidence in you!
"As your lovely illustrations will show..." One of the most awesome things you see here is just the mutual respect they have for each other, Terence and Grant. It really does show how important cooperation is in the sciences and mathematics
At wouldn't Tangent of the angle be the one to use here? Since sine of the angle equals the side opposite divided by the hypotenuse, meaning the distance between earth and moon divided by the distance between moon and sun. I thought tangent was opposite divided by adjacent, meaning distance between earth and moon divided by distance between earth and sun. If you use: tan(angle)=Dm/Ds and solve for Ds you get: Dm/tan(angle)
random trig question but, why are we able to know the theta angles are the same here?
hours - due to the motion of the Earth around the Sun (or the Sun around the Earth, in the geocentric model). [A similar correction needs to be made around , using the synodic month of 29 days and 12 hours rather than the "English lunar month" of 28 days (4 weeks).]
That value when calculated is coming about 18 minutes not 30 minutes as stated in the video
* I plugged in the modern values for the distances to the Sun and Moon and got 18 minutes for the discrepancy, instead of half an hour.
they had water clocks also
@ I'd like to here more about how the "30 minutes between (we see half) and (moon is halfway around its orbit)" was measured. In theory you can do it with a clock and a VERY precise examination of the Moon's surface, such that you know precisely what landmarks lay on its exact half, and then with a clock you know exactly where it is relative Earth. But even then, I'd imagine the terminator is not a clear line, and of course there are limits to telescopes' resolving capability. Ofc 1 arcsecond resolution isn't that hard to achieve at visible wavelengths, so maybe it's easier than I think. The error is OOM 1 part in 100 with a good telescope so nevermind I answered my own question.
- Heliocentrism in Antiquity
if complete lunar and solar eclipses didn’t exist, would it be much harder to figure out all these distances? how else would we get to the part at about the distance to the sun? (just halfway through watching gotta jot this note down)
For his time, why would he be inclined to say that a smaller object MUST orbit a larger object ?? It wouldn't be for much later when Galileo finds the moons of Jupiter, but even then: you couldn't conclude definitively that it is always the case based on such a low sample of observations. It wouldn't be until Newton that we link gravitational forces to orbits... (no?)
Ive wondered the same issue for yearsBut the graphics don't explain it tooIf we're rotating away , how our view doesn't shift?!Where are constellations located then?Thx
was honestly an incredible moment to ponder about, because it’s that counterargument against the heliocentric model that sets up just how big the universe is. Imagine being one of the first people connecting the dots that the heliocentric model is actually true, but the constellations not moving as the Earth orbits the Sun is also approximately true.
which song is playing at this point?
dude, WHERE IS THAT?!!!
* Could the parallax problem be solved by assuming that the stars are not distributed in a three-dimensional space, but instead on a celestial sphere?
@ could it not also have been true that the constellations were in a single, uniform layer? Almost like a very slow moving cloud that is just moving too slowly for us notice, or a feature of a boundary that we only see parts of
This actually shows how the often quoted "extraordinary claims require extraordinary proof" doesn't necessarily invalidate a claim. And also serves to show nescience doesn't stem from ignorance but can very well come from a place of logic
"it shows you that even when you get the maths right, you don't necessarily get to the truth...." — Terry Tao
- Kepler’s genius
This was not made so clear in our discussions or in the video (other than a brief glimpse of the timeline at ), but Eratosthenes's work actually came after Aristarchus, so it is very likely that Eratosthenes was aware of Aristarchus's conclusions about how distant the Sun was from the Earth. Even if Aristarchus's heliocentric model was disputed by the other Greeks, at least some of his other conclusions appear to have attracted some support. Also, after Eratosthenes's time, there was further work by Greek, Indian, and Islamic astronomers (such as Hipparchus, Ptolemy, Aryabhata, and Al-Battani) to measure the same distances that Aristarchus did, although these subsequent measurements also were somewhat far from modern accepted values.
it amazes me how whatever documentary, paper or history books, they love to "jump ahead" from about 0 BCE to 1600.. Isn't it wonderful how every genius and wonderful guy suddenly pops after the 15th century ? weird that from 500bce to 1500 it was the golden age of the most valuable civilzation that world has seen, the Islamic golden age. but no, newton suddenly found everything, and kepler as well
* Did nothing of note happen in astronomy between Eratosthenes and Kepler?
"Each time you take that next step, it's always heroic"Incredible quote.
Why are you using a portrait of Kepler that's been known to be a fake for years? 😒
days" for the earth to go . Isn't it like 365.25 since we have to add a a day every 4 years unless the year is divisible by 100? I think there's even another rule that comes after that but point being it's not exactly 365, it's *about* 365 :P
* Isn't it tautological to say that the Earth takes one year to perform a full orbit around the Sun?
* How did Copernicus figure out the crucial fact that Mars takes 687 days to go around the Sun? Was it directly drawn from Babylonian data?
- One small correction, the majority of Copernicus’s data was from Islamic (Arab/Persian) astronomy, not Babylonian.
you know how many times I have studied this Keppler thing but couldn't get it into my thick head, and now with this animation I finally got it??? My eyes welled up with tears. Thank you thank you thank you THANK YOU!!!
every time i hear about this theory i wonder and ask if anyone knows why 'that' order of platonic solids for the ratios? why not most faces to fewest, or vice-versa?
* What is that funny loop in the orbit of Mars?
* Can you elaborate on how we know that the planets all move on a plane?
Technically, these are two times when the technique of triangulation fails to be accurate; and also in the former case it is extremely difficult to observe Mars due to the proximity to the Sun. But again, following the Universal Problem Solving Tip from , one should initially ignore these difficulties to locate a viable method, and correct for these issues later.
* Can one work out the position of Earth from fixed locations of the Sun and Mars when the Sun and Mars are in conjunction (the same location in the sky) or opposition (opposite locations in the sky)?
h () to complete the full circle. However Moon is also moving in the same direction around Earth and during that 24 h it moves 1/27,3 of full circle. So the Earth has additional 24 h/27,3 to move to catch up or cca 50 minutes.
As a modern astrophysics PhD student I really shouted 'omg' and had goosebumps when I see at how the ellipse orbit of the earth was derived....
Damn! That was so genius! What a madlad!
From childhood, I have always curious in how astronomer use star's position to calc things out, as they are circled around earth, they do not stay in a flat coordinate system in my poor imagined space, when we are in earth, they stay at our front and back, left and right, it also hard to image how to solid record those things down. I never really dig into it, even though, every time I read some articles about solar system, black hole in central of galaxy, it make me feel ill to imagine how to record those things down, and how to calc some position out by those records. I really want to support this video in some worshipful ways, just for this 's "This is a genius thing". To know that this is a genius thing to figure out how to use those wired records, make me feel so comfortable and release, that make my stupid be acceptable!
How did they know about the 687 days of Mars' orbital period?
* So Kepler used Copernicus's calculation of 687 days for the period of Mars. But didn't Kepler discard Copernicus's theory of circular orbits?
* Did Brahe have exactly 10 years of data on Mars's positions?
years, but with many gaps, due both to inclement weather, as well as Brahe turning his attention to other astronomical objects than Mars in some years; also, in times of conjunction, Mars might only be visible in the daytime sky instead of the night sky, again complicating measurements. So the "jigsaw puzzle pieces" in are in fact more complicated than always just five locations equally spaced in time; there are gaps and also observational errors to grapple with. But to understand the method one should ignore these complications; again, see "Universal Problem Solving Tip #1". Even with his "idea of true genius" (which, incidentally one can find in Einstein's introduction to Carola Baumgardt's "Life of Kepler"), it took many years of further painstaking calculation for Kepler to tease out his laws of planetary motion from Brahe's messy and incomplete observational data.
The animation from to
: the points on earth's orbit seem to cluster closer together near the perihelion and spread out at the aphelion, isn't it meant to be the other way round to conserve Copernicus' rule on equal area for equal time intervals?
We can hardly imagine the immense effort and brilliance it must have taken for them to collect, store, share, and analyze such vast amounts of data. The mathematics we take for granted today looked entirely different back then, and they lacked the standardized units, precise tools, and advanced technology that we now rely on. Despite these challenges, their determination, intellectual drive, and hunger for knowledge must have been extraordinary.
- Where this leaves us
The sad part is here