Time transcripts of tsunamiSpeed

[00:00:00:010]	We are going to calculate the velocity of the tsunami now. All we need

[00:00:04:020]	is to know the formula

[00:00:08:020]	distance = rate x time

[00:00:12:030]	And we just rearrange that so that rate is over here by itself.

[00:00:16:040]	Which means we are going to divide distance by time. That's fun because

[00:00:20:040]	we already know those, right? We know that the distance is

[00:00:24:050]	551.9 km and we know that the time is

[00:00:28:060]	0.468 hours

[00:00:32:070]	So this gives us a velocity of 1,179

[00:00:36:080]	km/hr. Wow.

[00:00:40:080]	I don't know if you have any intuition about

[00:00:44:090]	how fast a tsunami goes in the open ocean. It's really fast, but it's not quite

[00:00:48:090]	as fast as this. Well, so where did we go wrong? 

[00:00:52:100]	Nothing about our method is wrong, but this is a good time to talk about uncertainty.

[00:00:56:100]	This station is really close to the earthquake. Let's just imagine 

[00:01:00:110]	a thought experiment here where you've got a station that takes a data

[00:01:04:120]	sample every 15 minutes, but let's say that

[00:01:08:130]	the tsunami only takes 45 minutes to get to that station. Being uncertain

[00:01:12:140]	plus or minus 15 minutes out of 45 minutes is huge!

[00:01:16:140]	It's a big uncertainty compared to the measurement you are making.

[00:01:20:150]	Let's say that you've got a station that takes data every 15 minutes and the tsunami

[00:01:24:160]	takes 8 hours to get there. Well, 15 minutes out of 8 hours is not nearly

[00:01:28:160]	as big of a deal. The absolute value

[00:01:32:170]	of your uncertainty can matter a lot more depending on its

[00:01:36:190]	relationship to the real size of the measurement you're making.

[00:01:40:190]	That is a really really important concept in any branch of science, so just think about that.

[00:01:44:200]	

[00:01:48:200]	But, anyway, look, this is real data, this is real life, it has uncertainties,

[00:01:52:210]	and that's okay. It doesn't fit neatly into multiple choice tests

[00:01:56:220]	designed by bureaucrats, but that's okay, that's the way it is.

[00:02:00:230]