Shadows That Move during the Day

The question: what changes in one shadow?

Choose a fixed object and observe its shadow on the same surface at two safe times during a day. A child can mark or describe where the shadow ends and compare the marks later. The object should stay in the same position; otherwise the change in shadow cannot be attributed simply to a changed lighting situation.

The activity practices making a dated, repeatable observation. The child may point, describe, draw, choose a symbol, or direct a helper. A shadow may change direction or length, be faint, or disappear when the light is blocked. The record should describe the actual result, including uncertainty.

Never look directly at the sun. An adult chooses a safe location, supervises materials, and follows local weather guidance. An indoor sunlit surface or a pair of labeled photographs can be used when an outdoor observation is unsuitable.

Set up a fixed object

Select a stable, suitable object that can remain in place, such as a large upright block secured on a sheet of paper indoors. The adult checks that it will not fall and that the surface can safely be marked. Do not place an object where it creates a trip hazard.

Mark the object’s position on the paper or use its existing fixed location as a reference. Choose a surface where the shadow is visible and the child can observe without approaching a window or outdoor area that is unsafe under the current conditions.

If sunlight does not reach an appropriate surface, use two photographs with known times and a fixed reference, or postpone. A flashlight is useful for a different demonstration, but moving the flashlight does not by itself document the sun’s changing position over a day.

Materials for a record

Prepare paper, a pencil or marker, and a way to note the date and time. A ruler is optional. The child can make a mark, tell a helper where to mark, or select a symbol in an accessible record.

Use separate labels for the first and second observation, such as “10 a.m.” and “2 p.m.” Record the actual times rather than planned times if the checks happen later. Include the object’s location and the surface used.

A photograph can supplement the marks if taking one is appropriate. Keep the camera angle and reference visible where possible. A photo is optional, and the family or setting should decide whether any images are kept or shared.

One observation sequence

The example below uses an object that an adult has placed safely on a surface receiving sunlight. The child does not need to look at the light source.

1. Choose a safe surface and have an adult place a stable object where a shadow is visible.
2. Mark the object’s base and show the child the shadow without looking at the sun.
3. Mark the selected shadow tip and label the actual time.
4. Leave the object and reference surface in place if safe.
5. At a later safe time, mark the same feature and label the new time.
6. Compare direction or distance and record any unclear edges or setup changes.

An example conversation

Adult: “Where can you see the shadow of this block?” Child: points to a dark shape on the paper. Adult: “Would you like me to mark its far end where you are pointing?” The child confirms, and the adult labels the mark with the time.

Later, the child notices that the shadow end is in another place. Adult: “The block stayed in its outline. Our second mark is here. What is different?” Child: “The shadow points another way.” The adult records that comparison.

If the child says the block moved, check the object’s position against its outline. If it did move, record that the setup changed and treat the two marks with caution. Do not claim a clean comparison without checking the reference.

What a shadow shows

A shadow is a darker region where an object blocks some light from reaching a surface. Its outline and position depend on the object, the light, and the surface. A child can inspect the visible boundary without touching the object.

Ask, “Which object is making this shadow in our setup?” Move a hand briefly between a safe indoor light and a surface, if appropriate, and notice the changed dark area. Return the hand out of the way before recording the fixed object’s shadow.

A shadow is not a separate solid object. The child can still describe it as a shape and compare its position. The observation does not require an explanation of every property of light.

Mark the same point each time

Choose a consistent feature, such as the farthest visible tip of the object’s shadow from a marked base. Point to that location and ask the child to confirm it before a helper marks the paper. Label the mark with the actual time.

A shadow may have a blurred edge. If the tip is hard to locate, note that uncertainty or draw a small region rather than a falsely precise dot. Use the same method at the second check.

If the paper shifts or the object moves, record the change. A mark only supports a comparison when its relationship to the same object and surface is understood.

Compare direction

Draw a line from the marked base of the object to each shadow-tip mark. Ask the child where the first line points and where the second points, using a fixed reference such as “toward the book” or “toward the wall.”

If the lines point in different directions, the marks show a change relative to the paper and object. The child can trace the two lines or indicate them with a communication device. A helper should not rotate the page between comparisons without noting it.

Avoid assuming that a particular direction will occur in every place and season. Record the actual directions in the local setup and describe how the reference was chosen.

Compare length

If the base and tip marks are clear, measure the distance from the same base point to each tip using the same ruler and units. An adult can hold the ruler while the child reads, points, or selects the longer line.

Record approximate values if the edge is fuzzy or alignment is imperfect. “About 12 centimeters” and “about 8 centimeters” are more informative than unlabeled numbers. Do not use invented precision to make the comparison appear exact.

A child can compare the lines visually without measuring. If the difference is too small to judge from the marks, say that it is unclear rather than selecting a longer line at random.

Why the shadow may change

During the day, the sun’s apparent position in the sky changes as Earth rotates. With a fixed object and surface, this can change the direction and length of its sunlit shadow. NASA’s [lesson on the sun’s position](https://nasaeclips.arc.nasa.gov/shared_assets/spotlite/suns-position/nasa-eclips-4d-sun-position-3-5-spotlite-interactive-lesson-508.pdf) describes daily patterns in shadow length and direction.

The local result depends on time, location, season, and the geometry of the setup. Do not promise a particular direction or exact length without measuring it. Indoors, window frames or other objects can also affect the available light.

The child need not look at the sun to observe its effect. Describe the shadow and reference marks on the surface, and use a model or diagram for the explanation if helpful.

If a cloud blocks the light

At the second visit, the shadow may be faint or absent because the lighting has changed. Record “no distinct shadow visible at this check” and the time. A missing mark is an observation, not a reason to guess where the tip would have been.

If the light returns and the group wants to check again, make a new dated or timed entry. Do not label a later mark with the earlier time. The interval between observations may contain changes that were not recorded.

The adult decides whether the location remains safe and comfortable. The activity can stop or move to a photograph if conditions are unsuitable.

If the object moves

The child may notice that the block is outside its original outline. That is valuable evidence about the setup. Record “object moved before the second mark” and check whether it can be returned accurately to the original position.

If its position or orientation cannot be restored reliably, begin a new series rather than comparing the marks as if nothing changed. Keep the original marks and explain the interruption if the child wants a record.

An adult should secure the object appropriately at the start and avoid placing it where people need to walk. Do not use heavy or unstable objects as observation tools.

If the paper moves

A fixed object on a loose sheet can stay in place relative to the room while the paper rotates. The drawn marks then no longer provide the same reference. Mark or secure the paper in an appropriate way before the first observation.

At the second check, compare the paper’s position with a fixed edge or other reference. If it has shifted, note the change and restart if necessary. A line on the page is meaningful only when its position relative to the object is known.

The child can help check an agreed mark without lifting or moving the object. A helper may manage the setup while the child decides what to record.

A simple first observation

Use one visible shadow and ask the child to show its end. The child can point, choose between two marked locations, or direct a helper. Record the time and one mark; a second visit is optional.

If the shadow has no clear edge, invite the child to describe it as “fuzzy” or point to the approximate darker region. The activity need not require an exact measurement.

A clear photograph of a shadow can be used instead of a live setup. Label it as a photograph and discuss the visible relationship between object and shadow.

A more detailed comparison

After two successful marks, add a third observation at a later safe time. Use the same object, base, surface, and method. Record each actual time and compare the three directions or lengths.

The child might arrange the records chronologically and say, “The second mark was closer to the base than the first.” Check the actual marks rather than supplying a predetermined pattern. Depending on conditions and timing, the observed sequence may differ from an expected example.

A third entry adds information but still does not describe every moment of the day. Missing or faint shadows should remain visible as gaps or uncertain observations in the record.

A picture of the setup

Draw the object, its marked base, and the shadow on a sheet. Add an arrow only if it has a clear meaning, such as the direction from the base to the shadow tip. The child can choose the marks and dictate labels to a helper.

A diagram made from above may omit the height of the object. Label it as a top view if that helps avoid confusion. Do not infer actual object height from a drawing that was not made to scale.

The picture can show two shadow-tip marks with their times. Keep the original page orientation or add a reference edge so the comparison remains understandable.

A model with a flashlight

A safe flashlight and a large object can model how changing a light’s position changes a shadow. An adult controls the light and ensures it is not shone into anyone’s eyes. Keep the object and screen fixed while moving the light between two positions.

Ask the child to compare the two shadow positions. Then explain the model’s limit: moving a flashlight in a room is a demonstration of a changing light direction, not a measurement of the sun’s path or Earth’s rotation.

The flashlight activity can be done separately when sunlight is unavailable. Its observations should not be mixed with timed outdoor or window observations in the same record without labels.

Two children share the work

One child can indicate the shadow tip while another marks the confirmed location. A third person may write the time. Participants can share or change roles; an adult manages the stable setup and safety.

If two people point to different edges, the shadow may be blurred. Let each show the area they see and mark a range or describe the uncertainty. The group can agree on a consistent method before the next check.

A child can participate without touching the paper or object by using a device, gaze, or instructions to a helper. Confirm each selected point before it is recorded.

A shadow that crosses another shadow

A window frame, chair, or another object may cast a second shadow across the paper. Ask which dark region belongs to the selected object. A small safe movement of a removable unrelated object by an adult may help identify its contribution, if appropriate.

If the shadows cannot be distinguished, record that the edge is unclear. Choose a clearer area or restart another time rather than guessing a tip. Do not move the fixed object and then use the original marks as though it had stayed still.

The overlap itself can be described as an observation, but it answers a different question from the movement of one object’s shadow.

When the shadow reaches the edge of the paper

If the shadow extends beyond the sheet, the visible end on the paper is not necessarily the true tip. Record “shadow continued beyond the page” and avoid measuring the page edge as the shadow’s length.

An adult can provide a larger suitable surface for a new series if it is safe to do so. Mark the object’s base and restart the observations. Do not splice marks from differently positioned sheets together without a reliable reference.

A child may still describe the direction of the visible portion. The unavailable tip limits a length measurement but does not prevent every observation.

Weather and safety interruptions

A weather change can end the activity. If a thunderstorm approaches, follow the relevant local guidance and move to appropriate shelter. The [National Weather Service lightning guidance](https://www.weather.gov/safety/lightning-tips) recommends shelter when thunder is heard and staying away from windows during a thunderstorm.

Do not remain at a window or outdoors to finish a mark during lightning. A record can say “observation stopped because conditions changed.” Another day or a labeled photograph can provide a new opportunity.

Sun exposure, heat, unstable surfaces, and local access rules also matter. An adult chooses the location and duration; a learning goal never requires an unsafe setup.

What a comparison can and cannot prove

Two marks show where the chosen shadow tip appeared under the recorded conditions. If the setup was stable, they support a statement about the change between those observations. They do not reveal every intermediate position.

If clouds, the object, the paper, or the selected tip changed, those factors limit the comparison. Record them rather than attributing every difference to one cause. A model can help explain a possible relationship but does not repair missing data.

A child’s prediction about the next mark is welcome if labeled as a prediction. The next observation may agree or differ, and either result can be discussed.

An accessible record

Offer large marks, clear labels, spoken descriptions, or a communication board. Explain the meaning of each symbol, including “edge unclear” and “no shadow visible.” The child may choose a format that does not require drawing.

A helper can position a ruler and read a measurement or mark a location selected by the child. Confirm the choice and note the assistance. A tactile representation of lines on a page can be offered if appropriate, but it represents the observation rather than the shadow itself.

If the child receives an adult’s report of a shadow, record the source accurately. Do not imply that the child directly saw a feature they could not access.

Review the marks together

At the end, show the base mark and the timed tip marks. Ask the child to choose one comparison: direction, approximate distance, or visibility. Read the labels and discuss what the marks support.

If a mark is missing or a setup changed, include that in the explanation. A child may say, “We cannot compare the length because the shadow went off the page.” That is a reasoned conclusion, not an incomplete answer.

Keep the page if it will be useful, or photograph it only with appropriate permission. The child can choose a favorite description or decide not to share the record.

A prediction before the second check

After making the first mark, ask whether the child wants to guess where the shadow tip will appear later. They may point to an area on the paper, say they do not know, or choose not to predict. Label any guess separately from the actual mark.

At the second safe check, show the original prediction and mark the visible tip using the agreed method. The prediction can be near, far from, or impossible to compare with the result if the edge is unclear. Keep both entries rather than altering the prediction afterward.

A correct guess is not the measure of success. The useful step is comparing a stated expectation with evidence while acknowledging any change in the setup or visibility.

Compare two marks with a paper strip

If a ruler is unavailable, an adult can place a strip from the base to the first tip and mark that distance. Without moving the base reference, compare the same strip with the line to the second tip. The child can indicate which line extends farther.

A strip comparison gives an ordering rather than a numerical length. If the tips are fuzzy or the two distances are nearly equal, record that the comparison is uncertain. Use the same starting point for both lines.

The helper can hold the strip while the child points. The strip should not move the fixed object or change the marked surface.

Continue with a related observation

Flashlight shadows with shape cutouts offers a separate indoor model of an object blocking light. Keep the light source, object, and screen roles clear, and never shine a flashlight into someone’s eyes.

Weather watching without predicting the forecast provides another way to record a view at a specific time. It distinguishes an observation from a forecast and emphasizes safe conditions.

Return the object and materials to their usual places after the adult decides the series is finished. A fixed setup is useful only while it remains safe and suitable for the setting.