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Current time:0:00Total duration:4:39

Video transcript

if you were to ask some people why we have seasons they might say that maybe it's due to how far we are from the Sun at different points in the year different points in Earth's orbit and what I want to do in this video is show you why that isn't the case so the line of reasoning would go something like this this is the Sun at the center of our solar system and roughly at the center of Earth's orbit and let me draw or its orbit over here and so the line of reasoning is that there's certain points in Earth's orbit where we're closer to the Sun and certain let me draw a better job than that so this lets say this is a point where we're closer to the Sun we a little further then we get a lot further and then we get a little bit closer and then we a little bit closer and then this is the closest point so maybe Earth's orbit looks something looks something like this looks something like this so the argument would go look their points in Earth's orbit where we're close to the Sun and points where we are further from the Sun and actually that part of the argument is true Earth's orbit is not a perfect circle and there are points in Earth's orbit where we are closer or further away from the Sun and actually when we are closest to the Sun so if the earth is right over here there's a word for that it's called perihelion just means the closest point in orbit perihelion peri perihelion close closest point in orbit to the Sun and there is a furthest point from the Sun and this is called a fee lien or at fili and I've somehow sometimes seen it called aphelion pronounced up Hylian aphelion aphelion so it is true that Earth's orbit is not a perfect circle around the Sun although it's pretty close but it's not a perfect circle it has a slight elliptical a slightly elliptical shape and because of that there are times in the year where we are closest to the Sun and there are times the year where we are furthest to the Sun and the difference is about 3% so it's not a huge difference in distance I've really exaggerated the difference in this diagram right over here but based on this reasoning people would say this is the flawed part that when when we're close to the Sun this must be the summer this must be the summer and when we are farthest away from the Sun this must be the winter this must be the winter and the most obvious point of evidence why this is not the case is that it is not summer when it is summer at one point in the plan it is not summer throughout the planet at that time in particular when it is so let me draw our planet in particular in particular when it is summer in the northern hemisphere when it is summer in the northern hemisphere actually let me do somewhere in a in a more warm color when it is summer in the northern hemisphere so here it is summer summer it is winter in the southern hemisphere it is winter in the southern hemisphere it is winter in the southern hemisphere and when it is summer in the southern hemisphere it is winter in the northern hemisphere so the entire planet does not experience the seasons at the same time so that's probably I guess you could say the biggest just point of data that we observe on our planet why this by itself cannot explain the change in seasons and in particular and in particular it does it really goes against what we experience in the northern hemisphere because our perihelion right now is occurring in January it is occurring during the winter the Northern Hemisphere winter perihelion right now is during the northern hemisphere hemisphere Northern Hemisphere winter and when we are farthest away from the Sun this is actually the Northern Hemisphere summer Northern Hemisphere Northern Hemisphere summer so although it might seem like a fairly intuitive idea hey if we're close to the Sun the whole plant is getting warmer may be that summer when we're further away the whole fit plants getting a little less energy that's winter the evidence we see on earth goes directly against that in particular we don't have the same seasons into both the northern and southern hemisphere at the same time and in particular in the northern hemisphere when we're closest to the Sun it's actually in January it's actually in the middle of winter so I'll leave you there in this video I've left you just saying okay so the closeness to the Sun does not right now does not dictate what season we are you're saying what is the reason and what we'll see in the next reason in the next in the next video the reason is the tilt of the axis of the earth the rotational axis of the earth