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graphs are used every day you see

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relationships everything from ticket

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sales to insurance claims if you want to

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see how one thing relates to another you

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can probably use a graph and believe it

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or not nASA has graphs for just about

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everything so what's the big secret

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let's start from the beginning no no no

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let's start from the right beginning the

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x axis the x axis needs to be a

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horizontal line at the bottom of your

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graph yes that's right now we will draw

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our y axis this one's vertical no no

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your Y axis needs to be on the left edge

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of your x axis now we're onto something

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hmm we need an example well let's say we

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want to travel to other planets we

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obviously need food to get there and

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back so we want to see the relationship

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between the planet we're going to and

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how much food each person will need to

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take with them so first label your axis

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as a rule we always put our independent

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variable on the x-axis in this case

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we'll put the number of days it takes to

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get to any given planet on the y axis

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will put the dependent variable why is

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it called the dependent variable well in

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our example the amount of food we need

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in kilograms depends upon how long it

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takes to get there and back so let's

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think of some examples

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National Space Station that's about a

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seven-day mission since we need about

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1.83 kilograms of food per day and

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that's so let's see 12 point 81

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kilograms now let's go to the moon we'll

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put in a few of the Apollo missions for

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reference now we have a bunch of dots it

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sort of makes sense but let's connect

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them all with a line now that looks

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better we can now see the relationship

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between how long a mission is and how

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much food we need to take this lets us

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ask some good questions like how much

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food would it take to get to say Mars

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wow that's a lot of food for one person

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fortunately NASA engineers think about

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these questions every day well there you

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go folks

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next time you want to see how two things

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relate to one another