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# 地球和太阳尺度

地球和太阳的尺度. 由 Sal Khan 创建

## 视频字幕

my goal in this video in the next you is to start giving a sense of the scale of really just the earth and the solar system and as we see is we start getting into like the galaxies in the universe it just becomes almost impossible to imagine but will at least give our best shot so I think most of us watching this video know that this right here is Earth this right here is Earth and just to get a sense of scale here I think probably probably the largest distance that we can somehow relate to is about a hundred miles you can get into a car for an hour hour-and-a-half and go about 100 miles and on the earth that would be about this far it would be a speck that would look something like that that is a hundred miles and also to get us a bit of scale let's think about a speed that at least we can kind of comprehend and that would be maybe the speed of a so let's think of the speed speed of a bullet speed of a bullet maybe we can't comprehend it but I'll say this is the fastest thing that we can maybe kind of comprehend it goes about and there are different types of bullets depending on the type of gun and all of that about 280 meters per second which is about 1000 1000 kilometers 1000 kilometers per hour and this is also roughly this is also roughly the speed the speed of a jet of a jet so just to give a sense of scale here the Earth's circumference the Earth's circumference so if you were to go around the planet the Earth's circumference just like that is about 40,000 kilometers it is 40,000 kilometers 40,000 kilometers so if you were to travel at the speed of a bullet speed of a bullet or the speed of a jetliner at a thousand kilometers an hour it would take you 40 hours to circumnavigate the earth 40 hours to go around the earth so it would take you 40 hours 40 hours to go around the earth and I think these none of this information is too surprising you might have taken 12 or 15 hour flights that get you not all the way around the earth but get you pretty far San Francisco to Australia or something like that so right now these aren't scales that are too crazy although you know even for me even the earth itself is a pretty mind-blowing ly large object now with that out of the way let's think about the Sun because the Sun starts to approach something far huger so this obviously here is the Sun and I think most people appreciate that the Sun is larger that it's much larger than the earth and that it's pretty far away from the earth but I don't think most people including myself fully appreciate how large the Sun is or how far into it is away from the earth so just to give you a sense the earth the Sun has the Sun has is a hundred nine times the circumference times the circumference of the earth times the circumference of the earth so if we do that same thought exercise there if we said okay if I'm traveling at the speed of a bullet or the speed of a jetliner it would take me 40 hours to go around the earth well how long would it take to go around the Sun so if you were to get on a if you were to get on a jet plane and try to go around the Sun or you know somehow ride a bullet and try to go around the Sun do a complete circumnavigation of the Sun it's gonna take you 109 times as long as it would taking you to do the earth so it would be 100 times I could do 109 but just for approximate it's roughly a hundred times the circumference of the earth so 109 times 40 is equal to four four thousand four thousand hours and just to get a sense of what four thousand is actually since I have the calculator out let's do the exact calculation it's a hundred nine times the circumference 109 times the circumference of the earth times 40 hours that's what it would take to do the circumference of the earth so it's four thousand three hundred and sixty hours to circumnavigate the Sun going at the speed of a bullet or a jetliner and so that is 24 hours in the day that is 181 days it would take you roughly half a year it would take half a year to go around the Sun at the speed of a jetliner let me write this down half a year half a year the Sun is huge the Sun is huge now that by itself may or may not be swear and actually let me give you a sense of scale here because I have this other diagram of a Sun this other diagram of a Sun and we'll talk more about the rest of the solar system in the next video but over here at this scale and the ass on this Sun at least on my screen if I were to complete it would probably about be about 20 inches in diameter the earth is just this little thing over here small smaller than a raindrop it's just a small little thing over here if I were to draw it on this scale where the Sun is even smaller the earth would be about that the earth would be right about that big now what isn't obvious because we've all done our science projects in third and fourth grade or we always see these diagrams of the solar system that look something like this is that these planets are way further away even though these are this is these are depicted to scale their way further away from the Sun and this makes it look so the Sun so I'm sorry the earth is a hundred and fifty million kilometers from the Sun so the earth earth is so this dish if this is if this is the Sun right here if this was the Sun right here you wouldn't even at this skill you wouldn't even be able to see the earth you wouldn't be able to see the earth it wouldn't even be a pixel but it would be a hundred and fifty it would be a hundred and fifty million 150 million 150 million kilometres from the earth and this distance right here is called an astronomical unit and we'll be using that term in the next few videos just because it's an easier way to think about distance sometimes abbreviated au astronomical unit astronomical astronomical unit and just to give you a sense of how far this is a light which is something that we think is almost infinitely fast and that you know something that looks instantaneous that takes 8 minutes to travel from the Sun to the earth if the Sun were to disappear it would take 8 minutes for that light for us to know that it disappeared on earth or another way just to put it in in the sense of this jet airplane let's get the calculator back out so we have a hundred we're talking about a hundred and fifty that's a thousand million that's a hundred and fifty million kilometres so if we're going at a thousand kilometres an hour so if we go two thousand kilometers our take us a hundred fifty thousand hours at the speed of a bullet or the speed of a jet plane to get to the Sun and just to get put that in perspective that if we wanted in days there's 24 24 hours per day so this would be six thousand 250 days or if we divide by 365 roughly 17 years if you were to shoot a bullet straight at the Sun it would take 17 years to get there if it could maintain its velocity somehow so this would take a bullet or a jet plane 17 years to get to the Sun 17 17 years or another way to visualize it this Sun right over here it looks on my screen it has about a 5 or 6 inch diameter if I were to actually do it as scale this little dot right here this little dot which is the earth this speck this speck if I actually wanted to draw this distance at scale I would have to put this speck about 50 feet away from the Sun 50 or 60 feet away from the Sun if you were to look at the solar system and we obviously there's other things in the solar system we'll talk more about them in the next video you wouldn't even know to suspect this is a little dust thing flying around this Sun and we as we go further and further out of this solar system you can see even this distance starts to become ridiculously small or another way to think about it if you if the Sun was about this size if the Sun was about this size then this speck then the earth at this scale would be about 200 feet away from it so you could imagine it's if you add a football field if you had a football field so let me draw a football field these are the endzone one end zone another end zone and your justic something maybe the size of a medicine sub ball a little bit bigger than a basketball at one end zone this little speck would be about 60 yards away or about roughly 60 meters away so this little speck you wouldn't even notice it on the scale of a football field something this size anyway I'm gonna leave you there hopefully that gives you just starts to blow your mind when you think about just just the scale of the Sun the earth and how far the earth is away from the Sun and then we're gonna see even those distances even those scales are super small when you start thinking about the rest of the solar system and especially when we start going beyond the solar system