Science

Common mistakes in earth and space

6 mistakes learners make with earth and space, each one named and explained.

All common mistakes

The Earth spins once a day and goes round the Sun once a year, and almost everything we see in the sky follows from those two motions.

Astronauts floating because there is no gravity

What it looks like

You say there is no gravity on the space station, when gravity there is nearly as strong as it is on the ground.

Why it happens

The word weightless says it plainly, and everything on screen floats.

A worked example

Question. Why do astronauts float on the space station?

A common answer. There is no gravity that far out

The answer. They are falling round the Earth, and everything around them is falling at the same rate

Why. Gravity is what keeps them in orbit. Without it they would fly off in a straight line.

Put the two side by side

No gravity would mean no orbit at all.
Falling together is why nothing presses on anything.

Ask what is holding them in their circle.

Day and night explained by the year long orbit

What it looks like

You say we have night when the Earth is on the far side of its orbit, which would make a night six months long.

Why it happens

Both motions are real and both are taught in the same lesson, so the one that causes day and night gets mixed up with the one that causes the year.

A worked example

Question. What causes day and night?

A common answer. The Earth going round the Sun

The answer. The Earth spinning on its own axis

Why. The orbit takes a year. Day and night change every few hours, so it must be the spin.

Put the two side by side

The orbit gives you the year and the seasons.
The spin gives you day and night.

Match the motion to how long the change takes.

Moon phases explained by the Earth's shadow

What it looks like

You say the Moon is a crescent because the Earth is blocking part of the sunlight.

Why it happens

The Earth's shadow does fall on the Moon sometimes, and a crescent looks exactly like something being covered up.

A worked example

Question. Why is the Moon sometimes a crescent?

A common answer. The Earth's shadow covers part of it

The answer. We see only part of the lit half, because of where the Moon is in its orbit

Why. The Earth's shadow on the Moon is a lunar eclipse, which happens rarely, not every month.

Put the two side by side

A shadow explanation would need an eclipse every month.
The orbit explanation gives a different shape every night.

Phases are about which part of the lit half faces us.

Seasons explained by how close the Earth is to the Sun

What it looks like

You say it is summer because the Earth has moved nearer to the Sun.

Why it happens

Nearer means hotter is true of a fire or a radiator, so it is a reasonable thing to reach for.

A worked example

Question. Why is it warmer in summer?

A common answer. The Earth is closer to the Sun in summer

The answer. That half of the Earth is tilted towards the Sun, so the light hits it more directly and for longer

Why. If distance caused the seasons, the whole planet would have summer at once.

Put the two side by side

Distance would give the north and the south summer together.
The tilt gives them opposite seasons, which is what actually happens.

Check your explanation against the other hemisphere before you believe it.

The Moon thought to make its own light

What it looks like

You list the Moon as a light source alongside the Sun and a lamp.

Why it happens

The Moon is plainly bright in a dark sky, and everything else that bright is making its own light.

A worked example

Question. Is the Moon a light source?

A common answer. Yes, the Moon gives out light

The answer. No, the Moon reflects light from the Sun

Why. A light source makes its own light. The Moon only sends back the Sun's.

Put the two side by side

The Moon is bright.
Bright is not the same as luminous.

Ask where the light was made, not where it came from last.

The Sun thought to travel round the Earth

What it looks like

You explain day and night by the Sun moving across the sky and round to the other side.

Why it happens

The Sun really does appear to move across the sky, and nothing you can feel tells you that the ground is turning.

A worked example

Question. Why do we have day and night?

A common answer. The Sun goes round the Earth once a day

The answer. The Earth spins on its axis once a day

Why. The Sun looks as though it moves because you are being carried round by the spin.

Put the two side by side

A Sun that circles the Earth would have to travel a vast distance every day.
A spinning Earth explains it with one turn.

Ask what is moving: the thing you are standing on, or everything else in the universe.

WAJD spots these patterns in your child's answers and names the one behind their wrong answers, instead of just marking them wrong.

More science topics