Chapter 4 of 7

All 7 chapters
  1. 1Sun, Earth and Moon, readunderstood
  2. 2Why we have day and night, readunderstood
  3. 3The Sun seems to move, readunderstood
  4. 4A year: going round the Sun, readunderstood
  5. 5The Moon goes round the Earth, readunderstood
  6. 6Phases of the Moon, readunderstood
  7. 7Eclipses, readunderstood

S2.9.4 Chapter 4

A year: going round the Sun

What is a year? Why does a year sometimes have an extra day?

Your guess

Pick one before you read on. It is fine to be wrong.

Your guess

  • You picked A. Read on. At the end, the chapter comes back to your guess.

  • You picked B. Read on. At the end, the chapter comes back to your guess.

  • You picked C. Read on. At the end, the chapter comes back to your guess.

By the end you can

  • Explain the Earth takes about 365 days to go round the Sun
  • Explain why every fourth year has an extra day
  • Explain that distance from the Sun does not make seasons

You know that one spin of the Earth makes a day. But the Earth also travels. It moves round the Sun in a big circle.

An orbit is the path of one thing round another. The Earth moves round the Sun in an orbit.

One trip round the Sun is one year.

On the left, a ball lit on its left half and shaded on its right half, with the words one spin = 1 day. On the right, a ring with a small Sun in the middle and a small ball on the ring, with the words one trip = 1 year. Under the ring are the words not to size. Labels: one spin, = 1 day, one trip, = 1 year, not to size.one spin= 1 dayone trip= 1 yearnot to size
One spin of the Earth is a day. One trip round the Sun is a year.

Draw it first

Draw the Earth going round the Sun

  1. The Sun in the middle, labelled Sun. A big ring round it is the path of the Earth. An arrow inside the ring points to the left along the path. A small ball on the ring on the right is the Earth, labelled Earth. Under the ring are the words one trip = one year.Sun

    1 Draw the Sun in the middle of the page. Write Sun.

  2. The Sun in the middle, labelled Sun. A big ring round it is the path of the Earth. An arrow inside the ring points to the left along the path. A small ball on the ring on the right is the Earth, labelled Earth. Under the ring are the words one trip = one year.Sun

    2 Draw a big ring round the Sun for the path. Add an arrow along it.

  3. The Sun in the middle, labelled Sun. A big ring round it is the path of the Earth. An arrow inside the ring points to the left along the path. A small ball on the ring on the right is the Earth, labelled Earth. Under the ring are the words one trip = one year.SunEarthone trip = one year

    3 Draw a small ball on the ring. Write Earth. Write one trip = one year.

This picture is not to size. The real path is much bigger.

The Earth moves very fast. But it moves smoothly, so you cannot feel it.

The trip takes about 365 and 1/4 days. That is a year.

A calendar uses whole days. A calendar year has 365 days. The extra quarter of a day does not fit.

A quarter of a day is about 6 hours. Each year, the calendar is 6 hours short.

The spare quarters add up. Four quarters make one whole day. After four years, we add one extra day.

See it three ways

As a picture

Four squares in a row. Each has a dotted strip on its left side. Under them are the words each year adds a quarter day. An arrow points down to one square filled with dots, labelled four quarters = 1 day.each year adds a quarter dayfour quarters = 1 day

In words

Each year is a quarter of a day longer than the calendar. Four quarters make one whole day. So we add a day almost every fourth year.

In symbols

1 year = 365 and 1/4 days. 4 × 1/4 = 1 day.

A leap year has 366 days. Almost every fourth year is a leap year. All the other years have 365 days.

Four boxes in a row, labelled year 1, year 2, year 3 and year 4. The first three boxes each hold the number 365. The fourth box holds 365 too, and a dotted strip is joined to its right side, labelled extra day. At the bottom are the words days in each year. Labels: 365, year 1, year 2, year 3, year 4, extra day, days in each year.365365365365year 1year 2year 3year 4extra daydays in each year
In a leap year, the extra day makes 366 days.

Try it

Add up the quarter days

You need: a sheet of paper, a pen.

Be safe: Tear the paper. Do not use scissors. Never look at the Sun.

  1. Fold the paper in half. Fold it in half again the same way. Open it out.
  2. Tear the sheet along the folds. You have four equal pieces.
  3. Write year 1 to year 4, one on each piece.
  4. Each piece is the quarter day that one year leaves over.
  5. Put the four pieces side by side to make the whole sheet.

What you will see: One piece is a quarter of the sheet. Four pieces make the whole sheet. In the same way, four spare quarter days make one whole day.

If you cannot try it, this is what happens.
Four pieces of paper side by side, labelled year 1, year 2, year 3 and year 4. An arrow points down to one whole sheet, split by three dashed lines into four parts, labelled one whole day.year 1year 2year 3year 4one whole day

The year also brings seasons. A season is a part of the year with its own weather.

Many places have a warm season and a cold season. Near the equator there is little winter or summer.

The Earth leans a little to one side. It goes round the Sun. It always leans the same way.

So for part of the year the north leans toward the Sun. For the rest of the year the south leans toward it.

The half that leans toward the Sun has its warm season.

The Sun in the middle, labelled Sun. An Earth stands on each side of it, with an arrow of light going to each. A straight line through each Earth leans the same way, with its top end to the left. On the right, the top end leans toward the Sun, and the words north warm are above it. On the left, the top end leans away from the Sun and the bottom end leans toward it, and the words south warm are below it. At the bottom are the words not to size. Labels: Sun, north warm, south warm, not to size.Sunnorth warmsouth warmnot to size
The Earth always leans the same way. On one side of its path the north leans toward the Sun. Half a year later the south does. Not to size.

A wrong idea many people have

Every year has exactly 365 days.

Why it feels right: A calendar has 365 days, and most years do too.

The test that breaks it: Look at the calendars of four years in a row. Count their days. Almost always, three have 365 and one has 366. The paper pieces show why.

What is true: A year is about 365 and a quarter days. So almost every fourth year has an extra day, a leap year.

A wrong idea many people have

Summer comes when the Earth is nearer the Sun.

Why it feels right: A fire feels hotter when you stand nearer to it.

The test that breaks it: The north is warm while the south is cold. Both halves of the Earth are the same distance from the Sun.

What is true: The Earth leans. The half that leans toward the Sun is warmer. Near the equator there is little winter or summer.

Key words

orbit
the path of one thing round another.
year
one trip of the Earth round the Sun. It takes about 365 and a quarter days.
leap year
a year with 366 days. It comes almost every fourth year.
seasons
parts of the year with their own weather.

Back to your guess

The answer is B: A year is one trip of the Earth round the Sun.

A year is one trip of the Earth round the Sun. It takes about 365 and 1/4 days. The quarters add up to an extra day.

Check yourself

Try each one before you look. A wrong answer tells you where to go next.

  1. What is a year?

    Tap your answer.

    1. Yes, that is right. The Earth goes round the Sun once a year. The trip takes about 365 and a quarter days.

    2. Not this one. One spin of the Earth is a day. A year is a whole trip round the Sun. Go to S2.9.2. Try another.

    3. Not this one. The Moon goes round the Earth in about a month. A year is the Earth's trip round the Sun. Try another.

    See the answer

    One trip of the Earth round the Sun

    The Earth goes round the Sun once a year. The trip takes about 365 and a quarter days.

    • If you chose B: One spin of the Earth is a day. A year is a whole trip round the Sun. Go to S2.9.2.
    • If you chose C: The Moon goes round the Earth in about a month. A year is the Earth's trip round the Sun.

  2. How many days is one trip of the Earth round the Sun?

    Tap your answer.

    1. Not this one. Thirty days is about one month. The Earth's trip round the Sun takes much longer. Try another.

    2. Not this one. The Earth spins once in about 24 hours. That is a day, not a year. Go to S2.9.2. Try another.

    3. Yes, that is right. The trip takes about 365 and a quarter days.

    See the answer

    About 365 days

    The trip takes about 365 and a quarter days.

    • If you chose A: Thirty days is about one month. The Earth's trip round the Sun takes much longer.
    • If you chose B: The Earth spins once in about 24 hours. That is a day, not a year. Go to S2.9.2.

  3. Count the days in 4 years in a row. Three years have 365 days. One leap year has 366 days. How many days in all?

    See the answer

    1 461 days

    3 times 365 is 1 095. Add 366 to get 1 461.

  4. Each year, the calendar is about 6 hours short. How many hours short is it after 4 years?

    See the answer

    24 hours, which is one whole day

    4 times 6 hours is 24 hours. That is one whole day, so we add a leap day.

  5. From an earlier chapter

    Which way does the Sun seem to move across the sky?

    Tap your answer.

    1. Not this one. The Earth turns toward the east. So the Sun seems to go west. Go to S2.9.3. Try another.

    2. Yes, that is right. The Earth turns toward the east. So the Sun seems to go west.

    3. Not this one. You can watch a shadow change through the day. The Sun seems to cross the sky. Go to S2.9.3. Try another.

    See the answer

    From east to west

    The Earth turns toward the east. So the Sun seems to go west.

    • If you chose A: The Earth turns toward the east. So the Sun seems to go west. Go to S2.9.3.
    • If you chose C: You can watch a shadow change through the day. The Sun seems to cross the sky. Go to S2.9.3.

  6. Draw the Sun and the Earth on its path. Write one year beside the path.

    See the answer

    A Sun in the middle with a ring round it. A small Earth sits on the ring. The words one year are by the ring.

    One trip of the Earth round the Sun is one year.

  7. Why does almost every fourth year have an extra day?

    Tap your answer.

    1. Not this one. The Earth takes the same time every year. The trip takes about 365 and a quarter days. Try another.

    2. Not this one. It is no mistake. A trip takes about 365 and a quarter days. The calendar adds a day to keep up. Try another.

    3. Not this one. A trip takes 365 days and a quarter, not 366. Only after four years do the quarters make a day. Try another.

    4. Yes, that is right. The calendar has 365 days. A trip takes a quarter of a day more. Four spare quarters make one day.

    See the answer

    Each year leaves a quarter of a day. Four of them make a whole day.

    The calendar has 365 days. A trip takes a quarter of a day more. Four spare quarters make one day.

    • If you chose A: The Earth takes the same time every year. The trip takes about 365 and a quarter days.
    • If you chose B: It is no mistake. A trip takes about 365 and a quarter days. The calendar adds a day to keep up.
    • If you chose C: A trip takes 365 days and a quarter, not 366. Only after four years do the quarters make a day.

  8. Why do some places have a warm season and a cold season?

    Tap your answer.

    1. Not this one. The north is warm while the south is cold. Both halves are the same distance from the Sun. Try another.

    2. Not this one. The Sun gives out about the same heat all year. The lean of the Earth changes how much each half gets. Try another.

    3. Not this one. The half facing the Sun has day. That changes every few hours. A season lasts months. It comes from the lean. Try another.

    4. Yes, that is right. The half that leans toward the Sun is warmer. Half a year later, the other half leans toward it.

    See the answer

    The Earth leans. Each half leans toward the Sun in turn.

    The half that leans toward the Sun is warmer. Half a year later, the other half leans toward it.

    • If you chose A: The north is warm while the south is cold. Both halves are the same distance from the Sun.
    • If you chose B: The Sun gives out about the same heat all year. The lean of the Earth changes how much each half gets.
    • If you chose C: The half facing the Sun has day. That changes every few hours. A season lasts months. It comes from the lean.

  9. The picture shows the Earth at the start of its trip. Where is it one year later?

    A ring with a small Sun in the middle, labelled Sun. A small ball on the right side of the ring, labelled Earth, with the word start beside it. At the bottom left are the words not to size. Labels: Sun, Earth, start, not to size.SunEarthstartnot to size
    Tap your answer.

    1. Not this one. Half way round takes about half a year. A whole year is a whole trip. Try another.

    2. Not this one. The Earth spins about 365 times in a year. It goes round the Sun only once. Go to S2.9.2. Try another.

    3. Yes, that is right. One year is one whole trip round the Sun. At the end of it the Earth is back where it began.

    See the answer

    Back at the start

    One year is one whole trip round the Sun. At the end of it the Earth is back where it began.

    • If you chose A: Half way round takes about half a year. A whole year is a whole trip.
    • If you chose B: The Earth spins about 365 times in a year. It goes round the Sun only once. Go to S2.9.2.

Keep it

Copy this into your exercise book.

One trip round the Sun takes about 365 and a quarter days. That is a year. The spare quarters add up to one day. So almost every fourth year has 366 days.

Draw: Draw the Sun and a ring round it. Put the Earth on the ring. Write one year.

Reading with a child? A short page for the adult: what this chapter teaches and three questions to ask.

No internet tomorrow? Save the whole book as one file (717 KB). It opens on any phone.