Lesson:What Is a Leap Year?/ExerciseL1

Listening Exercise

1 Watch the video and complete the text according to what you can understand.

You probably that this year 2012 is a leap year. And that means that this year we get an day on February, 29th. So instead of having 365 days this year, there will be 366. Great! An extra day, who really cares? Well people born on February, 29th on some leap year, also known as leaplings, they care, because they get to celebrate their real birthday. But, for the rest of us it's just a day like any other day. Whoopdy doo. So, why do we go to all the to have a leap year? Well, I'll , now we all understand that day. One full day is how long it takes for the Earth to spin around exactly once. And a year is how long it takes for the Earth to orbit the Sun exactly once. So while the Earth orbits around the Sun in a full year, it spins around three and sixty five point two five times. In other words, one full year 365.25 days. This is called the year. But here is the problem, our calendar year is only 365 days and that's because there's no way to have a .25 day. And so those extra .25 days they just keep and what they do is make it so that the stars drift out of sync with our calendar. So this is where leap year comes in to save the day. Every year we set aside those .25 days until the year when they equal one full day. And then on the fourth year we put that extra day on February 29th , then we call it leap day. Bamm, we're back in sync. That's why February, 29th exists. Cool! But the real thing, is how we humans figured this all out. It really was the , who first figured out leap year.

2

They noticed by the stars, specifically the Sirius star. That the astronomical year was actually 365.25 days and they this by seeing the Sirius star slowly drifting out of sync. But the western world wasn't so fast to figure this all out. It wasn't until many centuries later when Julio Cesar with the help of an astronomer, discovered just like the Egyptians first did that a year is really 365.25 days and they the Julian calendar with the leap year that we know and love to fix that problem. Well done Julius! Well, not so fast. You see, if you want to get really exact about it, the astronomical year is actually 365.2422 days which is 11min. 14 sec. than the Julian calendar. And that means in a hundred and twenty eight years from now, if we use the Julian calendar, we'll be again by one full day. So today, we use a version of the Julian calendar.

It's called the Gregorian calendar because pope Gregory it. The Gregorian calendar is just like the Julian calendar, but it has got a few more rules, so while every fourth year is a leap year. Every year that's by 100 are now no longer leap years. That means that years 1700, 1800, 1900, those were not leap years even knowing they would be. And here is another rule, if the year is also divisible by 400, then it is still a leap year. Which means that the year 2000, that was a leap year. And with all those complicated , our calendars can stay in sync with the star for millennia to come. But, one more thing. Did you know that the Earth's is slowing at a rate of .005 seconds per year? And that means in about two years we're gonna have to add one more leap year to in sync. But don't worry we've got of time to revise the calendar and fix that.