I like to believe that the relative amount of people who don't [or refuse to] understand the configuration of the solar system has diminished since ancient times
not sure why "depressing". genetically, men today, and men 3000 years ago are not that different. you can take a kid from 3000 years ago, put them in school today, and they'll do as well as anyone else. and just like you have some very smart people today, you had very smart people 3000 years ago. being smart is not so much about "what school you went to", it's more about "what questions do you ask?"
Or is it that modern communications, compared to those in Ancient Greek times, make it easier for shark oil salesmen to make money out of gullible idiots?
As a kid just about all of my astronomy learning was through books. I knew no-one with any expertise in it, and The Sky At Night was 20 minutes a month. Therefore, in my head, there are dozens of names - of people and stars and constellations - that I literally had no idea how to pronounce "properly" for many, many years. Even now, even though I know the "correct" pronunciations, my internal dialogue is stuck using young John's best guess of what Ptolemy and Sirius and Horologium should be, and when I say them out loud to someone it's like I'm having to translate from my native language.
@@xxrxoxoxo158 The first book, and the only one I owned as a child, was Patrick Moore's "The New Observer's Book of Astronomy". It was the 1983 edition, which was already a little out of date when I got it second hand, but I absolutely cherished (and still do, it's amongst many friends now on my bookshelves). From there I devoured everything at my school and local library.
I learned of Hipparcus in a history of western philosophy by Bertrand Russell and how to some "he was the greatest astronomer of Antiquity" and you talking of Erathostene's calculations reminded me of Carl Sagan video on him and the idea of why he did that calculation which is just incredible ; your video was truly good for me, brought back a lot of memories 🙂🙂👌🏾👌🏾.
I have also read that book...a fine, detailed voluminous book. Certainly a great introduction to the ideas immanent in Western thought throughout antiquity and on into modern concepts.
As a producer of Cosmos: A SpaceTime Odyssey (and a huge fan of Dr B) can confirm this was Carl. This video reminds me so much him and the way he would explain scientific concepts. Thank you Dr. Becky!
@@arctic_haze You say "still", but that flat earth thingy is a relatively new cultural phenomenon. Judging by all the evidence we have, it seems, that pretty much the first people that really thought about what the shape of the earth is and had the means to do the relevant measurements, figured out, that it is ball-like. The stupidity started later.
@@mikebaginy8731 They claim it is a "luminary", basically a light in the sky. This idiocy comes from a 19th century flat earther who published under the name of Parallax.
@@scifino1 It has been revived twice in recent times. Once in the 19th century by Parallax (real name Samuel Rowbotham) and in recent decades by Eric Dubay, a yoga instructor, who found his book "Zetetic Astronomy" and plagiarized it. But we have always have stupid people.
Eratosthenes' estimate of the size of the Earth is one of my favorite science history anecdotes. I've brought it up several times when explaining some science stuff while streaming. That and some of the bizarre science ideas Archimedes did (like inventing the fresnel mirror for his "sun weapon" haha)
Also, love what you do Dr. Becky, it is both inspiring - not just to me, to future generations - and informative. Looking forward to the next iteration. 🙏
Good video. Science that can be done at home with simple tools is great. It just so happens that a cheap 15cm/6in globe and a standard 40mm dia. table tennis ball make a very good scale model of the earth/moon (to within about 2%). Ask your kids or friends how far apart the globe and the ball should be, to represent true to scale the real distance from the earth to the moon. I reckon most people will hold them much closer that they should be, which is 4.53 m or nearly 15 feet apart!
Dr Becky....long time fan and follower! I would love to see a video on how you manage to do so much great RUclips content along with having such an amazing professional career as well as a personal life. I find your ability to do it impressive and aspirational.
Thanx Dr. Becky for making trigonometry seem like child's play !! My progress in math came to a full stop in high-schools trig class.I could never seem to find an easy way to remember which angle and which side of a right triangle the trigonometric functions referred too...like sine,cosine,tangent,cosine,cotangent etc. or how to combine these trig ratios with logorithms! Now I am an ageing senior,long past my high school years!!But I really must confess that your channel has really rekindled my interest in maths,physics,and astrophysics...all thanks to you!!!Keep up your very exciting RUclips broadcasts and of course...,Go Webb Go!!! Take care Dr. Becky!
Well, one thing is for sure Dr. Becky! Because of your favorite (besides Saturn) moon phase whenever I look up it will always be Dr. Becky's toenail moon :-D
Dr. Becky, Thank you for giving me a wonderful lesson idea for my high school geometry class next year. We've been developing our curriculum so I've had Lesson&Activities for geometry on the brain. Huge thanks to you for this brilliant inspiration! 👏 🙌
If you get a 25 foot tall pole and walk until the shadow of the pole is not in the well then the angle doesn’t seem that small anymore. You have a right triangle with the earth and the pole and one corner is the well.
I'm always fascinated learning how someone initially figured out how to make a specific measurements. How were they able to create a mental model of what they wanted to measure and then use what was known to solve the problem? Knowing the answer now makes the solution seem obvious but the first time is was a tremendous leap of genius.
yet you did not validate anything you believe. we tried, and proved they were wrong. your practicing a religion by just believing what someone tells you. no different than going to church.
@@hillside6401 .. Who are "you", "we" and "they" in your comment above? And as far as "just believing what someone tells you", you re wrong. I have made my own observations which are 100% incompatible with a Flat Earth (and even more one centered in the North Pole) and 100% compatible with a spherical Earth and the heliocentric model. Here you have a cue: I lived 2 years in the city of Rio Grande, province of Tierra del Fuego, Argentina. Look it up. And I am a private pilot too (small planes only).
@@adb012 "you" probably refers to Dr. Becky. That's pretty damn obvious. As for the other pronouns, the original poster can elaborate if they wish. The problem with Becky's approach is an assumed curvature of the earth which has never been accurately measured or even proven to exist.
@@schex86 ... I wonder how we are able to navigate around the world in ships and airplanes, put satellites in orbit, or make surveys of large fields, if we don't know what the radius the Earth is. Except, of course, that we know it because it has been accurately measured, and hence proven to exist.
Isn't it scary that people over 2,000 years ago knew things fundamentally that people today flatly deny... how is it that we've progressed as a civilization again?
There have always been dimwits but it's only now through the wonders of modern technology that they are able to spread their dimwittedness round (see what I did there?) the world.
This is an excellent example of the kind of teaching I want to see used in maths classes for young kids. I am fairly certain that you could teach kids calculus by 6th grade if you used the history of astronomical mathematics as a basis. It would make the subjects far more interesting than just reading paper, and what kid wouldn't love to be told that they have to stay up until midnight because their homework requires them to make observations on something at that time. It would also lean into the thinking that you don't need to be absolutely correct every single time you do maths. There are going to be margins of error in all types of things, and learning that is also important.
The way you said "trigonometry" in the bloopers section reminded me of "The More You Know" public service announcements that NBC airs in the US. Great video as always!
In the bit where Dr Becky explains the size of the moon, who else thinks of the Father Ted comedy sketch, where Ted explains "Cows: Small Or Far Away? to Dougal? 🤣
Dr. Becky, when you did the "TRIGONOMETRY" with the wide rainbow arms....it reminded me of the time Spongebob kept doing the rainbow arms and saying "IMAGINATION"....of course to be a great scientist you have to have a great imagination anyway to imagine there are always answers out in the universe, we just have to find them
Unfortunately 99.9% of the population will never know or experience the joy of finding things out because they don't care. But we love Becky for videos like this. Thanks.
I was taught different at school, same conclusion, but in my Lessons it was a different shadow length of a tower at 12 noon 500 miles apart . But would imagine you were in a higher class than me .The one that struck me ,was the fall of an Aqueduct over a set distance, to keep a steady flow .Roman engineering is really impressive
Howdy hi hi Dr. Becky! The thing that keeps bringing me back to your videos Dr. Becky is the genuine excitement and joy that is so evident upon your face when talking about this stuff. When I was in junior high, I encountered a particular problem in math. I think it was an extra credit problem or some such. In any case it was to find the number of units in a four sided pyramid where each level going up was one less than the level below. I worked on this problem for about an hour and a half that night, but alas I just couldn't work out how to calculate it. The next day when the solution was revealed as simply taking each of the squares and adding them all up. I was so very disappointed. Not that I'd failed to find this answer. But rather that the instructor would give so unworkable a solution for bases that exceeded even relatively small numbers. I never quite forgot that as it made me really mad. And so on summer break of my freshman year in high school. I decided I would work out how to do this properly. I filled two full notebooks with ideas and calculations carrying each one out to a base of 100 which was as high as I felt I could reasonably go with just a pen and paper. When I finally had my answer, I have to imagine that my face was filled with the same look as you so often times share with your viewers. The equation has since that time escaped my memory. It has been around three and a half decades since that time. But this is why I absolutely love watching you.
The history lesson you brought up certainly dispels the notion that ancient people believed in a flat earth and very much knew better. Another thing I wonder is that wouldn't the easily measurable umbra get smaller with increasing distance leading to underestimation of the Earth's radius? I find the degree of accuracy remarkable.
Not quite, because although majority of educated people did believe in the spherical Earth, majority of the ancient people still believed or were forced to believe in the Bible, Torah and other sacred scriptures literally, and many renowned Christian fathers (especially in the east) from the first five centuries professed the literal interpretation of the Bible with the firm firmament and the Earth situated on the (lower) waters, at the same time destroying majority of the pagan schools and libraries in just a couple of centuries. In that case the real shape of the Earth under the firmament is pretty irrelevant since the better part of Earth is situated under the water anyway, whereas the part above the water could e.g. be semi-spherical, since it was pretty clear to every sailor that the surface of the sea is curved. So, we are not really talking about those ancients who literally believed in the flat Earth here, but about those who believed in the Firmament that divides the upper waters from the lower waters and the Earth above it, as those in ancient Sumer, Egypt, India etc. thousands of years before the Hipparchus and Eratosthenes..
There is a common idea that believing past people think the world was flat is sort of a bias towards our modern day intelligence, suggesting people in the past were in the dark and stupid. Columbus wasn't trying to prove the earth was round, he was just trying (as I know it) to find an alternate way to get to the other side of the known continent. Widespread belief of a flat earth is, as you should not be surprised, a more modern thing, heavily started by Wilbur Glenn Voliva who ran the town of Zion. Bring on he internet and you get a self-perpetuating theory energized by people seeking an alternate form of identification.
@@kilroy987 Believing that the Earth is literally flat was moronic even 2000 years ago because it was pretty clear that the surface of the sea was curved and that no model of the flat earth could ever explain the trajectories of the Sun, Moon etc., but I'm not talking about those people or the modern ones, for me the flat earth model is rather a model of the universe with the Earth situated in its center on the waters beneath the firm rotating Firmament, because the spherical Earth can't float on the waters, and the majority of the people (regardless 60 or 75 %) even in the Middle ages just a thousand years ago, either believed in such model because of their sacred scriptures and the priests, or still did not believe in the scientific flying spherical Earth because of the lack of education and secular teachers.
The Earth's umbra does get smaller as you get farther from Earth. However, if the Sun is very far away, then light rays from the Sun are nearly parallel by the time they reach Earth, which means the umbra at the moon is very close to the size of the Earth. How do we know that the Sun is very far away? Imagine you are looking at a half-moon while the Sun is still up. Think of the triangle formed by Earth, the Moon, and the Sun. This is a right triangle with the Moon located at the right angle because the moon is being lit directly from the side. Now measure the angle where Earth is by pointing one straight rod at the Moon and another at the Sun and measuring the angle between them. The angle between the rods will be very close to 90 degrees. Since the angle at the Moon is 90 degrees and the angle at the Earth is close to 90 degrees, that means the Sun must be much much farther away than the distance between the Earth and Moon. Aristarchus tried to do this measurement, but the angle measurements weren't accurate enough, so his measurement of the distance to the Sun was much less accurate than his measurement of the Moon's distance. See this page for more explanations and a diagram: www.astro.umontreal.ca/~paulchar/grps/histoire/newsite/sp/great_moments_e.html#gm_250bc The more accurate way to measure the Sun's distance is to use Venus: curious.astro.cornell.edu/about-us/41-our-solar-system/the-earth/orbit/87-how-do-you-measure-the-distance-between-earth-and-the-sun-intermediate
I do that with kids. The real cool thing is finding different ways of calculating things using older mathematical tools like megalithic distance using gravity and pendulum swing to measure the size of the earth and Rational Trigonometry to work out ratios between triangle lengths. Degrees are out but spread is in.
Always love your videos and your passion to pass on your knowledge. It's amazing how far we've come with technology and it's easy to forget how long we've had the knowledge about our planet and the solar system (at least in part). Oh, and extra blooper at 4.29 Cirumference? 😉
Just watched a video, 2 days ago, highlighting the importance of having a ball of Twine. No twine, no video, they were so right! Super Cool video Dr Becky! Now if I can just find those old trig tables.
Amazing! I had noticed the round curve of Earth's shadow border around the Moon, but did not gave much tought about it, unconsciously I decided it was the same as the round border of Moon's own shadow as its phases go. Truly amazing how this information is hidden in plain sight
It is simpler with radio waves than with retro reflectors - because you use the reflex from the big moon instead of the small retro reflector. But the reflex from the retro reflector is much more precise.
True... even a radio amateur at home can point a radio signal at the moon and receive its reflection 2.5 seconds later. It used to require quite big antennas and a lot of power, but with the advent of digital signal processing that enables receiving signals that are "in the noise", it is now possible for every radio amateur who wants to try it.
@@Rob2 Back before modern electronics, it was still possible it just took a lot of specially built hardware to do it. In modern stuff, you stack the signals. In the old method you had to use a very narrow bandwidth to get the same sort of effect.
@@kensmith5694 No, that isn't the same! When you make a very narrow filter at some time you basically hear only a tone, but it is impossible to hear of that is what you sent up or if it is noise filtered to a narrow bandwidth. Stacking signals is not the same as filtering. I remember being at a 2M EME station in the 1980's. 1kW output in 4 yagis and receiver with narrow filter, you mostly just hear singing noise. Today with 100W in a single yagi you can make a QSO.
@@Rob2 Perhaps I need to explain more fully. Consider what stacking is in the frequency domain. Each frequency that is a multiple of the repeat rate is selected for and other frequencies are rejected. A narrow pass filter does this but for only one frequency. Thus you can obtain one component of the stacked result. If you set the experiment up correctly, from the phase you can get an ambiguous measure of the distance. You will know that the distance is and unknown integer times the ambiguity plus a distance based on the phase. Once you know that, you can do the same experiment with a different filter to rule out some of the ambiguity.
The flerfs would reject this because of the optical measurements, demanding a physical measurement to the moon, etc. So where do you buy a 240,000 mile tape measure!
@@romithromith the flerfs would reject this because "nuh-uh!". There's no point trying to be logical or rational with them because they have no interest in either: their claims and arguments are based on irrationality and are completely illogical.
@@KeithMilner Flerfs are at the bottom of the conspiracy theory pecking order. _American Moon,_ an Apollo Hoax video, begins with this warning: "Do not upload this film on other accounts, neither in whole or part. In particular, the so called "flat earthers" are warned against using any of this material in their own videos."
Oh, I do, absolutely. But unfortunately, it works only for relatively small numbers. We have to use alternative algorithms to find larger primes of the size we typically use in cryptography. (I'm a computer programmer.) Here's a million-dollar question: Can you find the prime factors of a number in polynomial time?
Great video, Dr. Becky! Think for a moment, about what a crescent or first or third quarter moon looks like from where you live. Keep in mind the angle of the terminator (the light/dark line on the surface of the moon) relative to the position of the sun... I have lived most of my life at or above 37' north latitude, so the terminator angles I referenced above have always been at a slant relative to the horizon. Some years ago while in Hawaii, I saw the moon rise at mid-day in the first quarter phase (the moon appeared as a half circle.) What blew me away was that the terminator on the moon (the flat side of the half circle) was nearly parallel to the horizon which was the Pacific Ocean. I thought "I have never noticed that before!" I reasoned that the only way that was possible was that I had changed my position (latitude) on a curved surface. Another example of "observational astronomy!"
I don't think they are actually prisms. I thought they were like the radar reflectors fitted to boats, consisting of triangles of metal fixed at 90 degrees to form a double pyramid.
I take it this is a parrel creation thing. Scott manly released a vid yesterday about this. But goes onto measuring the universe. Ether way gceat video Dr Becky
The tricky thing about Hipparchus "using a bit of trigonometry" to solve the problem is that, prior to his calculation, there wasn't really such a thing as trigonometry. Like, there were no trigonometric tables he could refer to at this time. Until the first one. That was compiled by Hipparchus. 😅
How to calculate distance to the Moon: 1. Get a really big ball of string. 2. Tie one end to the Earth. 3. Go to the Moon. 4. Mark off, on the string, where the Moon is, with a pencil. There you go. Easy.
2000 years ago, they knew the earth was round. Huge idea for that time era. My point being some (relatively) intelligent people still today claim the earth is flat.
My old, now deceased, mother never could believe we had men land on the moon back in 1969. Why? Because her total lack of knowledge of science, space and rocketry just didn't allow her mind to grasp it. Today "intelligent" people are too often uneducated, they don't understand modern technology, especially when it comes to even the most elementary concepts of astronomy and space exploration. As a result they latch onto something they can understand, purposeful misinformation and often conspiracy theories. Willful ignorance, essentially. Choosing to believe fanciful lies rather than believe in good science.
Lovely. I was always wondering how different history of humanity would be without Moon's precise shadow. It reminds me Fermi. You show me how relatively easy it is. Thanks
This is fun! I remember doing it back in school (all those many, many moons ago!), and never forgot that it's exactly how science is done. _~huge grin~_ And you're wearing my favorite color of polish I love to wear, too. 😊
"(radar measurement) was a lot more difficult because the signal was a lot weaker." Not true, actually. Ham radio operators can measure the distance to the moon with home equipment, much easier than the high power lasers and observatories you need to use for the retroreflectors. Of course you sacrifice precision over lasers, but you don't need millimeter precision to get good data.
According to my geometry, the Earth's shadow is 26% smaller when it reaches the Moon's orbit but I guess Hipparchus was smart enough to take that into account.
It's funny that you repeated Eratosthenes many times in the bloopers so that you say it correctly but then said it wrong in the video anyway! :) Love your videos, Dr. Becky! You are awesome!
The certain time of day is noon at the summer solstice . The ancient Syene (not the modern Aswan) is on the tropic of Cancer line and at that day and time even the deepest wells are lit to the very bottom. They also had good enough sundials to determine the noon accurately because the earth rotates by 1 degree every 4 minutes. Also, he used the length of the arc and not the distance of the chord (as shown in the video) by using professional "bematists" . Although the first known working and accurate odometer had been invented by a contemporary and acquaintance of Eratosthenes (Archimedes) he used people to measure it from what is known from historical sources. Carl Sagan . for his TV show Cosmos , made a very nice video , shot in Egypt ,about the size of the Earth
I continue to be in awe of the towering intellects that ancient Greece produced. If only that tradition had continued to the present we would be way ahead of where we are now.
I observed it first-hand back in the 1970s and 1980s when handheld electronic calculators became popular. Students and some scientists no longer relied on things like estimates and manual checking, instead they put numbers in and got answers out with no clue as to whether they were correct or meaningful. Before that time we used slide rules and mathematical tables and had to have a good grasp of numbers. Yes, calculators and computers are better than slide rules but they don't require much knowledge and it is much easier to get fooled by a wrong result. So to the ancient Greeks, they of course had none of the modern inventions so they had to rely more on their intellect. It required more discipline and as a result they seem to us today as towering intellects. Our students today are lazy, they want answers without doing the necessary work. Our best today are likely as smart as the ancient Greeks, but their achievements tend to get obscured by the noise of the vast multitudes of underachievers among us.
I love science but could never be a scientist because of math like this. I was a C student in math all through school. I still use my fingers when adding lol.
For anyone interested to understand how retroreflectors (0:15) work, you can learn more about them in @SmarterEveryDay's video ruclips.net/video/dsRsap2_RAc/видео.html and in @SteveMould's video ruclips.net/video/z5cR6EA2jGY/видео.html 🙂
I understand how the laser reflects but there's one thing I don't get. The Earth is moving and rotating, so in the ~2½ seconds it takes to go to the Moon and back, the Earth & the place that shot the laser has moved, so when the laser returns to the same spot it moved and is not there anymore. For example at the United State latitudes the Earth is rotating about 600mph which is about 880 feet a second. So even if the laser stayed in line between the Moon and Earth's orbits, because the earth is rotating, when the laser returns it should hit about 2200 feet (770 meters) to the east.
@qam2024 oh that's a good point, never thought of that detail 🤔 My guess is that still works because you have to remember all motion is relative. Yes the earth spins… but the moon is tidal-locked with it and the Earth-Moon system is thus kinda fixed together when considered on their own system in isolation. Another way of thinking about it is that it's similar to when you throw a ball vertically while in a train and the ball still lands back in your hand. Or consider that when the laser is shot from Earth, it has the same angular velocity than the Earth has from spinning.
There is a way of drawing the circle from the shadow using a ruler pencil and compasses that may help with accuracy. This technique creates a circle from any three points and it is easier to understand with pictures but I will try to explain it. Bisecting any chord of a circle at 90 degrees to the chord ("chord" = any straight line touching the perimeter of the circle twice) creates a line that passes through the centre of the circle. So if we put three points on an image of the earth's shadow on the moon and draw lines from one to the next and to the next (basically A to B to C) we create two chords and bisecting them creates two lines which meet at the middle of the circle. Bisecting the lines is where the pencil and compasses come in. Set the compasses to a length something over half the length of the line to be bisected and from each end of the line make an arc that passes through the line and extends each side long enough to meet a similar arc from the opposite end. Make sure the arcs meet on both sides of the line and then connect the points of intersection of those arcs. That creates a line at exactly ninety degrees to the chord exactly in the middle. Do that for both chords and you have the two lines which will meet at the centre of the circle. The three points can be anywhere along the edge of the shadow but the longer the line the more accurate the process so it helps to print out a big picture of the moon and shadow, put a point at each end of the shadow and then the third somewhere in the middle. It doesn't have to be in the centre of the shadow as the technique works with chords of any length. Once you have the centre of the circle you can measure the radius. In case that doesn't make sense there is a video here ruclips.net/video/4PlmucbAoek/видео.html
Very good, and definitely better than guess and check. One tiny point: in Euclid's day, they didn't allow your compasses to remember their radius, so you have to bisect two points by drawing a circle centred at one and passing through the other for both points, which obviously forces identical radii. I tend to do it the way you described, though, because I have smarter compasses than Euclid's :-D
@@davidgould9431 The teacher who taught me this method was a big fan of Euclid and his enthusiasm infected me. From just a handful of basic axioms and postulates Euclid created the fundamental structure of flat geometry. I am sure he was one of the giants on whose shoulders Newton was standing.
You had an image of the eclipse to work with on your tablet. How did they do it so long ago? A quick scetch on papyrus by memory possibly, or maybe holding up various circle templates until they found a good fit? I wonder how they did it.
Maybe they used a camera obscura(pinhole camera) to project the moon eclipse onto a paper of some sort and trace that with a pencil. Or they just used a stretched arm and measure both moon and eclipsed part on a little stick or ruler in there hand or something, they just needed the size differences. Though since the prediction was that accurate, I might be leaning more to the camera obscura idea.
Hi, Dr. Becky!! I've just ordered your book "Space At The Speed Of Light." I've been reading about astronomy and watching astronomy documentaries ever since childhood and have not looked back. I watch your videos because it is a great source of updated information about astronomy. I'm especially interested in what the James Webb Space Telescope can do to discover the secrets of the universe. Kepp up the great work.
Doesn't this only work if you assume that the Sun is sufficiently far away so that the size of the Earth's shadow on the Moon is basically the same as the size of the Earth?
You can confirm that condition by measuring long shadows to check how parallel they are. If they are parallel enough, you can assume a good enough approximation.
God, I still remember when we did the calculation of the radius of the Earth in the same way in the geography class in 7th grade and the calculation of the parallel where we are and the direction of the north towards the shadow angle of a 1 m high stick. The outdoor school was a full day trip, a day of geography in the field, best time ever in primary school, usually near a small observatory or in the mountains or a night outdoors miles away from a light source. My kids didn’t learn any of it, they were literally lost in space while standing on the planet
Scott Manley and Becky both channeling the spirit of Hipparchus this week.
But Scott totally failed the "Eratosthenes" pronunciation challenge! Point to Becky.
What I find depressing is that Hipparchus had a better understanding of what the Solar System than some people on the Internet today.
I like to believe that the relative amount of people who don't [or refuse to] understand the configuration of the solar system has diminished since ancient times
@@limiv5272 The wast masses of those that doesn't know doesn't care. The problem are those that are confident that they do know and are wrong.
@@michaelpettersson4919 Dunning-Kruger-Effect
@@christianege4989 Exactly.
not sure why "depressing". genetically, men today, and men 3000 years ago are not that different. you can take a kid from 3000 years ago, put them in school today, and they'll do as well as anyone else.
and just like you have some very smart people today, you had very smart people 3000 years ago.
being smart is not so much about "what school you went to", it's more about "what questions do you ask?"
It's crazy how ancient Greeks managed to do all this, meanwhile some people in 2022 still think the Earth is flat
Or is it that modern communications, compared to those in Ancient Greek times, make it easier for shark oil salesmen to make money out of gullible idiots?
It's crazy how people blindly believe they're spinning @ 1000 mph without ANY evidence whatsoever
@@MrCheswickMusic Thanks for proving my point.
@@MrCheswickMusic you have at least one piece of evidence, it's called coriolis effect, you should go outside more and look at some river banks...
@@MrCheswickMusic "a 15 degree per hour drift..." Thanks Bob!!!
As a kid just about all of my astronomy learning was through books. I knew no-one with any expertise in it, and The Sky At Night was 20 minutes a month. Therefore, in my head, there are dozens of names - of people and stars and constellations - that I literally had no idea how to pronounce "properly" for many, many years. Even now, even though I know the "correct" pronunciations, my internal dialogue is stuck using young John's best guess of what Ptolemy and Sirius and Horologium should be, and when I say them out loud to someone it's like I'm having to translate from my native language.
Hey what books do you have about astronomy 🤩
@@xxrxoxoxo158 The first book, and the only one I owned as a child, was Patrick Moore's "The New Observer's Book of Astronomy". It was the 1983 edition, which was already a little out of date when I got it second hand, but I absolutely cherished (and still do, it's amongst many friends now on my bookshelves). From there I devoured everything at my school and local library.
That was so beautifully written.
@@jamilaali7288 What a tremendously kind thing to say! Thank you. :)
For me, Hermione was "Hermy-one" until Stephen Fry and audio books
I learned of Hipparcus in a history of western philosophy by Bertrand Russell and how to some "he was the greatest astronomer of Antiquity" and you talking of Erathostene's calculations reminded me of Carl Sagan video on him and the idea of why he did that calculation which is just incredible ; your video was truly good for me, brought back a lot of memories 🙂🙂👌🏾👌🏾.
That video is on RUclips. I think it's a clip from Cosmos.
I have also read that book...a fine, detailed voluminous book. Certainly a great introduction to the ideas immanent in Western thought throughout antiquity and on into modern concepts.
@@waynedarronwalls6468 completely agree with you
@@caw25sha yup, it's that one.
As a producer of Cosmos: A SpaceTime Odyssey (and a huge fan of Dr B) can confirm this was Carl. This video reminds me so much him and the way he would explain scientific concepts. Thank you Dr. Becky!
It’s amazing what the ancients could achieve with observation, logic and some simple mathematics.
Also, it is astounding that with the technology we have now, there are still people claiming that the Earth is flat and space does not exist.
@@arctic_haze I wonder if flat-earthers believe the moon is also flat. Or made of cheese?
@@arctic_haze You say "still", but that flat earth thingy is a relatively new cultural phenomenon. Judging by all the evidence we have, it seems, that pretty much the first people that really thought about what the shape of the earth is and had the means to do the relevant measurements, figured out, that it is ball-like. The stupidity started later.
@@mikebaginy8731 They claim it is a "luminary", basically a light in the sky. This idiocy comes from a 19th century flat earther who published under the name of Parallax.
@@scifino1 It has been revived twice in recent times. Once in the 19th century by Parallax (real name Samuel Rowbotham) and in recent decades by Eric Dubay, a yoga instructor, who found his book "Zetetic Astronomy" and plagiarized it. But we have always have stupid people.
This is something the Ancient Aliens crowd forget. Humans are very clever at finding things out.
Would also be good content for flat earthers
There’s no getting through to flat earthers. Conclusion first, then twist or cherry pick observations to fit conclusion.
@@ArvelJoffi I don't think "conclusion" is the right word to use. Belief would be more accurate
@@ArvelJoffi There's no point in trying to be rational with flat earthers, as the conclusion they came to is based in irrationality
A person is smart. People are dumb, panicky, dangerous animals and you know it.
Eratosthenes' estimate of the size of the Earth is one of my favorite science history anecdotes. I've brought it up several times when explaining some science stuff while streaming. That and some of the bizarre science ideas Archimedes did (like inventing the fresnel mirror for his "sun weapon" haha)
will have to find a how eratosthesnes did it so i can do it too! sounds fun!
Big kid here with little kids of my own, will definitely share this with them, thank you!
Perfect 😃
Appropriate moon earrings, too! Nice! 🌗👍🏻💙😀
Also, love what you do Dr. Becky, it is both inspiring - not just to me, to future generations - and informative.
Looking forward to the next iteration. 🙏
Good video. Science that can be done at home with simple tools is great. It just so happens that a cheap 15cm/6in globe and a standard 40mm dia. table tennis ball make a very good scale model of the earth/moon (to within about 2%). Ask your kids or friends how far apart the globe and the ball should be, to represent true to scale the real distance from the earth to the moon. I reckon most people will hold them much closer that they should be, which is 4.53 m or nearly 15 feet apart!
Same. I use a basketball and a tennis ball as the representative sizes, and the distance apart is 7 metres.
It is really impressive that these people were able to find out such things long before satellites, or even circumnavigation!
Dr Becky....long time fan and follower! I would love to see a video on how you manage to do so much great RUclips content along with having such an amazing professional career as well as a personal life. I find your ability to do it impressive and aspirational.
Thanx Dr. Becky for making trigonometry seem like child's play !! My progress in math came to a full stop in high-schools trig class.I could never seem to find an easy way to remember which angle and which side of a right triangle the trigonometric functions referred too...like sine,cosine,tangent,cosine,cotangent etc. or how to combine these trig ratios with logorithms! Now I am an ageing senior,long past my high school years!!But I really must confess that your channel has really rekindled my interest in maths,physics,and astrophysics...all thanks to you!!!Keep up your very exciting RUclips broadcasts and of course...,Go Webb Go!!! Take care Dr. Becky!
Well, one thing is for sure Dr. Becky! Because of your favorite (besides Saturn) moon phase whenever I look up it will always be Dr. Becky's toenail moon :-D
Dr. Becky,
Thank you for giving me a wonderful lesson idea for my high school geometry class next year. We've been developing our curriculum so I've had Lesson&Activities for geometry on the brain.
Huge thanks to you for this brilliant inspiration! 👏 🙌
As someone with only a bachelor's degree in astrophysics, it brings me some joy that a professor of the subject can still misspell circumference.
Amazing that the ancient Greeks were able measure such small angles !!!
You too can measure such small angles.
If you get a 25 foot tall pole and walk until the shadow of the pole is not in the well then the angle doesn’t seem that small anymore. You have a right triangle with the earth and the pole and one corner is the well.
It is not small at all. We can measure much-much smaller angles today.
I guess we have better toys today, but not any better imagination.
@@ecospider5 I strongly suspect that you may be right but I need at least a 2 minute animated cartoon to demonstrate what you are saying
Wow, didn't know this follow-up on Eratosthenes. Simply genius.
Amazing! Wish I took a moment to pause and see if I could come up with that by myself
I'm always fascinated learning how someone initially figured out how to make a specific measurements. How were they able to create a mental model of what they wanted to measure and then use what was known to solve the problem? Knowing the answer now makes the solution seem obvious but the first time is was a tremendous leap of genius.
Dr Becky: "Anyone, even a kid with a pencil and a piece of string, can figure out the distance to the Moon"
Flat Earther: "We are not just anyone!"
yet you did not validate anything you believe. we tried, and proved they were wrong. your practicing a religion by just believing what someone tells you. no different than going to church.
@@hillside6401 .. Who are "you", "we" and "they" in your comment above? And as far as "just believing what someone tells you", you re wrong. I have made my own observations which are 100% incompatible with a Flat Earth (and even more one centered in the North Pole) and 100% compatible with a spherical Earth and the heliocentric model.
Here you have a cue: I lived 2 years in the city of Rio Grande, province of Tierra del Fuego, Argentina. Look it up. And I am a private pilot too (small planes only).
@@adb012 "you" probably refers to Dr. Becky. That's pretty damn obvious. As for the other pronouns, the original poster can elaborate if they wish. The problem with Becky's approach is an assumed curvature of the earth which has never been accurately measured or even proven to exist.
@@schex86 ... I wonder how we are able to navigate around the world in ships and airplanes, put satellites in orbit, or make surveys of large fields, if we don't know what the radius the Earth is. Except, of course, that we know it because it has been accurately measured, and hence proven to exist.
The earth is a pyramid. Why do you think the aliens built pyramids rather than spheres?
I have been fascinated with astronomy since middle elementary school in the mid 60's. Dr. Becky's enthusiasm is so refreshing.
Dr. Becky has it going on. Sounds like she has a nice singing voice. Would be nice to hear a bit more in the next video.
Isn't it scary that people over 2,000 years ago knew things fundamentally that people today flatly deny... how is it that we've progressed as a civilization again?
There have always been dimwits but it's only now through the wonders of modern technology that they are able to spread their dimwittedness round (see what I did there?) the world.
We have progressed _in spite_ of the deniers, who have done everything in their power to hold us back.
People have become so distrustful of the powers-that-be, after cereal lying, that they question everything.
@@phukfone8428well... is there really two scoops of raisins in a box of raisin bran?🤪 cereal...
@@phukfone8428 There is a _grain_ of truth in what you say.
Fascinating, as always, Dr. Becky. Thank you.
Yeah pseudo science stories are very comforting for the ignorant masses, keep it up Becky...
This is an excellent example of the kind of teaching I want to see used in maths classes for young kids. I am fairly certain that you could teach kids calculus by 6th grade if you used the history of astronomical mathematics as a basis. It would make the subjects far more interesting than just reading paper, and what kid wouldn't love to be told that they have to stay up until midnight because their homework requires them to make observations on something at that time.
It would also lean into the thinking that you don't need to be absolutely correct every single time you do maths. There are going to be margins of error in all types of things, and learning that is also important.
Well, my favourite Moon artist is Louis Armstrong. His Moon River is so brilliant that everything seems pretty close.
Captivatingly educational and eye candy beautiful 💙
The way you said "trigonometry" in the bloopers section reminded me of "The More You Know" public service announcements that NBC airs in the US. Great video as always!
In the bit where Dr Becky explains the size of the moon, who else thinks of the Father Ted comedy sketch, where Ted explains "Cows: Small Or Far Away? to Dougal? 🤣
wonderful again i did it over one side and the other side of the moon and was amazed how it worked keep them coming i enjoy every one
Dr. Becky, when you did the "TRIGONOMETRY" with the wide rainbow arms....it reminded me of the time Spongebob kept doing the rainbow arms and saying "IMAGINATION"....of course to be a great scientist you have to have a great imagination anyway to imagine there are always answers out in the universe, we just have to find them
I heard "IMAGINAAAATION" as well!
Unfortunately 99.9% of the population will never know or experience the joy of finding things out because they don't care. But we love Becky for videos like this. Thanks.
Must admit, when I first heard how Eratosthenes measured the Earth I was blown away. Those Greek dudes were pretty clever!
Brilliant! Thanks a bunch, dr. Becky! 😃
Stay safe there with your family! 🖖😊
I was taught different at school, same conclusion, but in my Lessons it was a different shadow length of a tower at 12 noon 500 miles apart . But would imagine you were in a higher class than me .The one that struck me ,was the fall of an Aqueduct over a set distance, to keep a steady flow .Roman engineering is really impressive
Dr. Becky is my favorite astrophysicist.
Howdy hi hi Dr. Becky!
The thing that keeps bringing me back to your videos Dr. Becky is the genuine excitement and joy that is so evident upon your face when talking about this stuff. When I was in junior high, I encountered a particular problem in math. I think it was an extra credit problem or some such. In any case it was to find the number of units in a four sided pyramid where each level going up was one less than the level below. I worked on this problem for about an hour and a half that night, but alas I just couldn't work out how to calculate it.
The next day when the solution was revealed as simply taking each of the squares and adding them all up. I was so very disappointed. Not that I'd failed to find this answer. But rather that the instructor would give so unworkable a solution for bases that exceeded even relatively small numbers. I never quite forgot that as it made me really mad. And so on summer break of my freshman year in high school. I decided I would work out how to do this properly. I filled two full notebooks with ideas and calculations carrying each one out to a base of 100 which was as high as I felt I could reasonably go with just a pen and paper.
When I finally had my answer, I have to imagine that my face was filled with the same look as you so often times share with your viewers. The equation has since that time escaped my memory. It has been around three and a half decades since that time. But this is why I absolutely love watching you.
Such beautiful singing at the end.
The history lesson you brought up certainly dispels the notion that ancient people believed in a flat earth and very much knew better.
Another thing I wonder is that wouldn't the easily measurable umbra get smaller with increasing distance leading to underestimation of the Earth's radius? I find the degree of accuracy remarkable.
Not quite, because although majority of educated people did believe in the spherical Earth, majority of the ancient people still believed or were forced to believe in the Bible, Torah and other sacred scriptures literally, and many renowned Christian fathers (especially in the east) from the first five centuries professed the literal interpretation of the Bible with the firm firmament and the Earth situated on the (lower) waters, at the same time destroying majority of the pagan schools and libraries in just a couple of centuries.
In that case the real shape of the Earth under the firmament is pretty irrelevant since the better part of Earth is situated under the water anyway, whereas the part above the water could e.g. be semi-spherical, since it was pretty clear to every sailor that the surface of the sea is curved.
So, we are not really talking about those ancients who literally believed in the flat Earth here, but about those who believed in the Firmament that divides the upper waters from the lower waters and the Earth above it, as those in ancient Sumer, Egypt, India etc. thousands of years before the Hipparchus and Eratosthenes..
There is a common idea that believing past people think the world was flat is sort of a bias towards our modern day intelligence, suggesting people in the past were in the dark and stupid. Columbus wasn't trying to prove the earth was round, he was just trying (as I know it) to find an alternate way to get to the other side of the known continent. Widespread belief of a flat earth is, as you should not be surprised, a more modern thing, heavily started by Wilbur Glenn Voliva who ran the town of Zion. Bring on he internet and you get a self-perpetuating theory energized by people seeking an alternate form of identification.
@@kilroy987
Believing that the Earth is literally flat was moronic even 2000 years ago because it was pretty clear that the surface of the sea was curved and that no model of the flat earth could ever explain the trajectories of the Sun, Moon etc., but I'm not talking about those people or the modern ones, for me the flat earth model is rather a model of the universe with the Earth situated in its center on the waters beneath the firm rotating Firmament, because the spherical Earth can't float on the waters, and the majority of the people (regardless 60 or 75 %) even in the Middle ages just a thousand years ago, either believed in such model because of their sacred scriptures and the priests, or still did not believe in the scientific flying spherical Earth because of the lack of education and secular teachers.
Chin,ese thought the world was flat until quite recently, until that is some Jesu,it priests showed them otherwise...
The Earth's umbra does get smaller as you get farther from Earth. However, if the Sun is very far away, then light rays from the Sun are nearly parallel by the time they reach Earth, which means the umbra at the moon is very close to the size of the Earth.
How do we know that the Sun is very far away?
Imagine you are looking at a half-moon while the Sun is still up. Think of the triangle formed by Earth, the Moon, and the Sun. This is a right triangle with the Moon located at the right angle because the moon is being lit directly from the side. Now measure the angle where Earth is by pointing one straight rod at the Moon and another at the Sun and measuring the angle between them. The angle between the rods will be very close to 90 degrees. Since the angle at the Moon is 90 degrees and the angle at the Earth is close to 90 degrees, that means the Sun must be much much farther away than the distance between the Earth and Moon.
Aristarchus tried to do this measurement, but the angle measurements weren't accurate enough, so his measurement of the distance to the Sun was much less accurate than his measurement of the Moon's distance. See this page for more explanations and a diagram: www.astro.umontreal.ca/~paulchar/grps/histoire/newsite/sp/great_moments_e.html#gm_250bc
The more accurate way to measure the Sun's distance is to use Venus: curious.astro.cornell.edu/about-us/41-our-solar-system/the-earth/orbit/87-how-do-you-measure-the-distance-between-earth-and-the-sun-intermediate
Any time I see how good the ancients were at figuring out outer space makes me depressed about flat earthers.
I do that with kids. The real cool thing is finding different ways of calculating things using older mathematical tools like megalithic distance using gravity and pendulum swing to measure the size of the earth and Rational Trigonometry to work out ratios between triangle lengths. Degrees are out but spread is in.
Dr Becky showing us an actual good use for all that math we learnt at school but never used.
Always a delight and highlight to any kind of day I'm having to see a new Dr. Becky video pop up!
Always love your videos and your passion to pass on your knowledge.
It's amazing how far we've come with technology and it's easy to forget how long we've had the knowledge about our planet and the solar system (at least in part).
Oh, and extra blooper at 4.29 Cirumference? 😉
Just watched a video, 2 days ago,
highlighting the importance of having a ball of Twine.
No twine, no video, they were so right!
Super Cool video Dr Becky!
Now if I can just find those old trig tables.
Amazing! I had noticed the round curve of Earth's shadow border around the Moon, but did not gave much tought about it, unconsciously I decided it was the same as the round border of Moon's own shadow as its phases go. Truly amazing how this information is hidden in plain sight
It is simpler with radio waves than with retro reflectors - because you use the reflex from the big moon instead of the small retro reflector.
But the reflex from the retro reflector is much more precise.
s/reflex/reflection/g
True... even a radio amateur at home can point a radio signal at the moon and receive its reflection 2.5 seconds later.
It used to require quite big antennas and a lot of power, but with the advent of digital signal processing that enables receiving signals that are "in the noise", it is now possible for every radio amateur who wants to try it.
@@Rob2 Back before modern electronics, it was still possible it just took a lot of specially built hardware to do it. In modern stuff, you stack the signals. In the old method you had to use a very narrow bandwidth to get the same sort of effect.
@@kensmith5694 No, that isn't the same! When you make a very narrow filter at some time you basically hear only a tone, but it is impossible to hear of that is what you sent up or if it is noise filtered to a narrow bandwidth. Stacking signals is not the same as filtering.
I remember being at a 2M EME station in the 1980's. 1kW output in 4 yagis and receiver with narrow filter, you mostly just hear singing noise.
Today with 100W in a single yagi you can make a QSO.
@@Rob2 Perhaps I need to explain more fully. Consider what stacking is in the frequency domain. Each frequency that is a multiple of the repeat rate is selected for and other frequencies are rejected. A narrow pass filter does this but for only one frequency. Thus you can obtain one component of the stacked result. If you set the experiment up correctly, from the phase you can get an ambiguous measure of the distance. You will know that the distance is and unknown integer times the ambiguity plus a distance based on the phase. Once you know that, you can do the same experiment with a different filter to rule out some of the ambiguity.
This is a great flat earth debunk! I will share this with them. Thanks Becky.
The flerfs would reject this because of the optical measurements, demanding a physical measurement to the moon, etc. So where do you buy a 240,000 mile tape measure!
Yeah, flatties don't do maths.
@@romithromith the flerfs would reject this because "nuh-uh!".
There's no point trying to be logical or rational with them because they have no interest in either: their claims and arguments are based on irrationality and are completely illogical.
@@KeithMilner Flerfs are at the bottom of the conspiracy theory pecking order. _American Moon,_ an Apollo Hoax video, begins with this warning: "Do not upload this film on other accounts, neither in whole or part. In particular, the so called "flat earthers" are warned against using any of this material in their own videos."
Wait.. Ara-toss-the-knees? Briliant! Now I will never forget.
If you like Eratosthenes, you're going to love his sieve.
Oh, I do, absolutely. But unfortunately, it works only for relatively small numbers. We have to use alternative algorithms to find larger primes of the size we typically use in cryptography. (I'm a computer programmer.)
Here's a million-dollar question: Can you find the prime factors of a number in polynomial time?
Great video, Dr. Becky!
Think for a moment, about what a crescent or first or third quarter moon looks like from where you live. Keep in mind the angle of the terminator (the light/dark line on the surface of the moon) relative to the position of the sun...
I have lived most of my life at or above 37' north latitude, so the terminator angles I referenced above have always been at a slant relative to the horizon. Some years ago while in Hawaii, I saw the moon rise at mid-day in the first quarter phase (the moon appeared as a half circle.) What blew me away was that the terminator on the moon (the flat side of the half circle) was nearly parallel to the horizon which was the Pacific Ocean. I thought "I have never noticed that before!" I reasoned that the only way that was possible was that I had changed my position (latitude) on a curved surface.
Another example of "observational astronomy!"
I absolutely love your enthusiasm! You cause me to look up more often. Thank You!
surveyor happy place . For the record the reflectors we call prisms, I think because it is quick and easy to say that way.
I don't think they are actually prisms. I thought they were like the radar reflectors fitted to boats, consisting of triangles of metal fixed at 90 degrees to form a double pyramid.
Thanks Dr.Becky.keep looking up ✨. Martin from the Emerald Isle 👍☘️
I mean I love you and the bloopers the best but I want you to sing more, please. You are too funny and yes a big kid at heart who is also smart.
Oh Becky I love hearing you explain everything to my designy brain!
Eratosthenes's knew that the sun would shine down that well in Cyrene on the summer solstice, because Cyrene is on the Tropic of Cancer.
I take it this is a parrel creation thing. Scott manly released a vid yesterday about this. But goes onto measuring the universe.
Ether way gceat video Dr Becky
The tricky thing about Hipparchus "using a bit of trigonometry" to solve the problem is that, prior to his calculation, there wasn't really such a thing as trigonometry. Like, there were no trigonometric tables he could refer to at this time. Until the first one. That was compiled by Hipparchus. 😅
Incorrect. The Egyptians were using trigonometry a thousand years prior to Hipparchus.
They just had a different name for it.
There is geometric trigonometry allowing to make analog calculations without any tables or number calculations.
How to calculate distance to the Moon:
1. Get a really big ball of string.
2. Tie one end to the Earth.
3. Go to the Moon.
4. Mark off, on the string, where the Moon is, with a pencil.
There you go. Easy.
2000 years ago, they knew the earth was round. Huge idea for that time era. My point being some (relatively) intelligent people still today claim the earth is flat.
My old, now deceased, mother never could believe we had men land on the moon back in 1969. Why? Because her total lack of knowledge of science, space and rocketry just didn't allow her mind to grasp it. Today "intelligent" people are too often uneducated, they don't understand modern technology, especially when it comes to even the most elementary concepts of astronomy and space exploration. As a result they latch onto something they can understand, purposeful misinformation and often conspiracy theories. Willful ignorance, essentially. Choosing to believe fanciful lies rather than believe in good science.
Even though much of your stuff goes over my head. You make it fun to learn and I do learn watching your videos. Keep up the great work!
Lovely.
I was always wondering how different history of humanity would be without Moon's precise shadow. It reminds me Fermi.
You show me how relatively easy it is. Thanks
Well you have to remember the Earth and Moon were created, they didn't just "happen" to be of the correct diameters and distances apart.
@@txmike1945 Well. I cant remember this event, it was cca 4 000 000 000 years ago, and iam only 33 :-D
@@josifekkunardi1086 :-) :-)
Brilliant stuff… And should be mandatory in schools. Very powerful and inspirational to see what 'basic' maths can do.
I thought basic math WAS mandatory in schools.
This is fun! I remember doing it back in school (all those many, many moons ago!), and never forgot that it's exactly how science is done. _~huge grin~_
And you're wearing my favorite color of polish I love to wear, too. 😊
It was another clear story. Seen on 26-5-22 at 21:47 in the NL.
What a fun video! Your joi de vie was uplifting.
Good point but you might as well learn the phrase correctly, "joie de vivre."
@@txmike1945 je pense qu’on parle pas français! In other words get a life be careful of what you say to whom.
"(radar measurement) was a lot more difficult because the signal was a lot weaker."
Not true, actually. Ham radio operators can measure the distance to the moon with home equipment, much easier than the high power lasers and observatories you need to use for the retroreflectors. Of course you sacrifice precision over lasers, but you don't need millimeter precision to get good data.
I enjoy the videos, I feel like I’m geeking out on science with a friend. Your energy is amazing.
Thanks! I really enjoyed this.
According to my geometry, the Earth's shadow is 26% smaller when it reaches the Moon's orbit but I guess Hipparchus was smart enough to take that into account.
Re: bloopers; was hoping you would mention the work of Eratoste-shoulders and Eratosthe-toes
Those are a few of my favorite things!!
Science is CRAZY
While I've tried and failed to get a degree in physics, these surprisingly silly experiments are what make everything so cool.
A degree in science is twice as big as the moon :P
Cirumference! 4:25. Great video though.
Brilliant!
Geotrig is what killed my pursuance of Electrical Engineering 🙄😏 Great video Dr. Becky. Thank you for sharing 🤗😘
What maths do flat earthers use to tell the distance to the Moon? Triggerednometry
triggernometry
Love this variety in the kind of content on the channel.
It's funny that you repeated Eratosthenes many times in the bloopers so that you say it correctly but then said it wrong in the video anyway! :) Love your videos, Dr. Becky! You are awesome!
The certain time of day is noon at the summer solstice . The ancient Syene (not the modern Aswan) is on the tropic of Cancer line and at that day and time even the deepest wells are lit to the very bottom. They also had good enough sundials to determine the noon accurately because the earth rotates by 1 degree every 4 minutes. Also, he used the length of the arc and not the distance of the chord (as shown in the video) by using professional "bematists" . Although the first known working and accurate odometer had been invented by a contemporary and acquaintance of Eratosthenes (Archimedes) he used people to measure it from what is known from historical sources. Carl Sagan . for his TV show Cosmos , made a very nice video , shot in Egypt ,about the size of the Earth
I continue to be in awe of the towering intellects that ancient Greece produced. If only that tradition had continued to the present we would be way ahead of where we are now.
I observed it first-hand back in the 1970s and 1980s when handheld electronic calculators became popular. Students and some scientists no longer relied on things like estimates and manual checking, instead they put numbers in and got answers out with no clue as to whether they were correct or meaningful. Before that time we used slide rules and mathematical tables and had to have a good grasp of numbers. Yes, calculators and computers are better than slide rules but they don't require much knowledge and it is much easier to get fooled by a wrong result.
So to the ancient Greeks, they of course had none of the modern inventions so they had to rely more on their intellect. It required more discipline and as a result they seem to us today as towering intellects. Our students today are lazy, they want answers without doing the necessary work. Our best today are likely as smart as the ancient Greeks, but their achievements tend to get obscured by the noise of the vast multitudes of underachievers among us.
I just get a big grin watching your vids :) Thanks!
I love science but could never be a scientist because of math like this. I was a C student in math all through school. I still use my fingers when adding lol.
Indeed DrB, remembered that of eclipse later then, wrapped sense figured: much appreciated many thanks!
For anyone interested to understand how retroreflectors (0:15) work, you can learn more about them in @SmarterEveryDay's video ruclips.net/video/dsRsap2_RAc/видео.html and in @SteveMould's video ruclips.net/video/z5cR6EA2jGY/видео.html 🙂
Thanks ....mirrors are weird .....
I understand how the laser reflects but there's one thing I don't get. The Earth is moving and rotating, so in the ~2½ seconds it takes to go to the Moon and back, the Earth & the place that shot the laser has moved, so when the laser returns to the same spot it moved and is not there anymore.
For example at the United State latitudes the Earth is rotating about 600mph which is about 880 feet a second. So even if the laser stayed in line between the Moon and Earth's orbits, because the earth is rotating, when the laser returns it should hit about 2200 feet (770 meters) to the east.
@qam2024 oh that's a good point, never thought of that detail 🤔
My guess is that still works because you have to remember all motion is relative. Yes the earth spins… but the moon is tidal-locked with it and the Earth-Moon system is thus kinda fixed together when considered on their own system in isolation. Another way of thinking about it is that it's similar to when you throw a ball vertically while in a train and the ball still lands back in your hand. Or consider that when the laser is shot from Earth, it has the same angular velocity than the Earth has from spinning.
There is a way of drawing the circle from the shadow using a ruler pencil and compasses that may help with accuracy. This technique creates a circle from any three points and it is easier to understand with pictures but I will try to explain it.
Bisecting any chord of a circle at 90 degrees to the chord ("chord" = any straight line touching the perimeter of the circle twice) creates a line that passes through the centre of the circle. So if we put three points on an image of the earth's shadow on the moon and draw lines from one to the next and to the next (basically A to B to C) we create two chords and bisecting them creates two lines which meet at the middle of the circle. Bisecting the lines is where the pencil and compasses come in. Set the compasses to a length something over half the length of the line to be bisected and from each end of the line make an arc that passes through the line and extends each side long enough to meet a similar arc from the opposite end. Make sure the arcs meet on both sides of the line and then connect the points of intersection of those arcs. That creates a line at exactly ninety degrees to the chord exactly in the middle. Do that for both chords and you have the two lines which will meet at the centre of the circle. The three points can be anywhere along the edge of the shadow but the longer the line the more accurate the process so it helps to print out a big picture of the moon and shadow, put a point at each end of the shadow and then the third somewhere in the middle. It doesn't have to be in the centre of the shadow as the technique works with chords of any length. Once you have the centre of the circle you can measure the radius.
In case that doesn't make sense there is a video here ruclips.net/video/4PlmucbAoek/видео.html
Very good, and definitely better than guess and check. One tiny point: in Euclid's day, they didn't allow your compasses to remember their radius, so you have to bisect two points by drawing a circle centred at one and passing through the other for both points, which obviously forces identical radii. I tend to do it the way you described, though, because I have smarter compasses than Euclid's :-D
@@davidgould9431 The teacher who taught me this method was a big fan of Euclid and his enthusiasm infected me. From just a handful of basic axioms and postulates Euclid created the fundamental structure of flat geometry. I am sure he was one of the giants on whose shoulders Newton was standing.
You had an image of the eclipse to work with on your tablet. How did they do it so long ago? A quick scetch on papyrus by memory possibly, or maybe holding up various circle templates until they found a good fit? I wonder how they did it.
Maybe they used a camera obscura(pinhole camera) to project the moon eclipse onto a paper of some sort and trace that with a pencil.
Or they just used a stretched arm and measure both moon and eclipsed part on a little stick or ruler in there hand or something, they just needed the size differences.
Though since the prediction was that accurate, I might be leaning more to the camera obscura idea.
Very interesting, and I love the way you say “Moon” it’s like mooon, I love it and love your channel🥰🥰🥰❤️
@James Sharier so what you really mean is, you love pseudo science made up stories!
Hi, Dr. Becky!! I've just ordered your book "Space At The Speed Of Light." I've been reading about astronomy and watching astronomy documentaries ever since childhood and have not looked back. I watch your videos because it is a great source of updated information about astronomy. I'm especially interested in what the James Webb Space Telescope can do to discover the secrets of the universe. Kepp up the great work.
Hope you enjoy!
The book just arrived today.
Doesn't this only work if you assume that the Sun is sufficiently far away so that the size of the Earth's shadow on the Moon is basically the same as the size of the Earth?
You can confirm that condition by measuring long shadows to check how parallel they are. If they are parallel enough, you can assume a good enough approximation.
I once saw her calculate the distance to the Moon with a pencil. A fookin pencil!
Outstanding video!
God, I still remember when we did the calculation of the radius of the Earth in the same way in the geography class in 7th grade and the calculation of the parallel where we are and the direction of the north towards the shadow angle of a 1 m high stick.
The outdoor school was a full day trip, a day of geography in the field, best time ever in primary school, usually near a small observatory or in the mountains or a night outdoors miles away from a light source.
My kids didn’t learn any of it, they were literally lost in space while standing on the planet
Are you and your friends going to do a full length astrophysical musical? Because that would be awesome.
The _Dance of the Galaxies_ could be the opening number. I guarantee the _Singularity Solo_ would be a show stopper.
I gave this a go today. The circle I drew had a diameter 3.34 times that of the Moon. Not bad.
Doc, you rock.