The Fossil Record Is Missing Most of the Story What gets preserved — and what disappears?

 

The Fossil Record Is Missing Most of the Story

What gets preserved — and what disappears?

Stand in front of a museum display and it is easy to imagine that you are looking at a representative selection of ancient life.

There are shells, teeth, bones and perhaps a beautifully preserved leaf. Put them together and a lost world begins to emerge.

But imagine trying to reconstruct your garden from the things that would still be recognisable after years of decay, burial and disturbance. Would your collection represent everything that once lived there?

Or would it mostly represent the things that were hardest to destroy?

The fossil record is an extraordinary source of evidence. It is also a highly selective one.

That makes fossils a wonderful starting point for a question that reaches far beyond palaeontology:

What might be missing from the evidence we have?

Nature does not preserve everything equally

A dead organism does not automatically become a fossil.

It may be eaten, decomposed, broken apart, transported or dissolved. Even remains that become buried can undergo changes that destroy their structure or remove details.

The study of these processes is called taphonomy: the investigation of what happens to organisms and their remains after death, including the changes involved in preservation.

A useful classroom description is:

Taphonomy asks how a living thing became the evidence we can examine today.

A shell and a piece of soft fruit provide a simple comparison. Both come from living organisms, but their structures and chemical compositions give them very different chances of surviving.

Hard parts such as shells, teeth and bones generally have a better chance of preservation than soft tissues. Rapid burial can also help by reducing exposure to scavenging and physical disturbance. Neither guarantees a fossil. [1, 2]

There are several filters between life and a museum

Think of the fossil record as the result of a sequence of opportunities for information to be lost.

Filter	Question to ask
Original community	What organisms actually lived here?
Death and decay	Which parts survived decomposition and scavenging?
Burial	Which remains entered sediment rather than being destroyed?
Geological change	Which evidence survived subsequent physical and chemical changes?
Discovery	Which fossil-bearing rocks became accessible and were searched?
Display	Which finds were selected for the public to see?

The final collection is not a random sample of the original community.

That is what bias means here: some kinds of evidence have a greater chance of entering the record than others.

A museum display adds another selection. A spectacular skeleton can attract attention in a way that a tray of tiny fragments may not. Yet small, less dramatic fossils can be scientifically valuable too.

The question to take into a museum is therefore:

“Why am I seeing these organisms, and what else might have lived alongside them?”

Where an organism lived matters too

Body structure is only part of the story.

An organism living where sediment accumulates has a different preservation opportunity from one living on an exposed upland slope. Marine environments, rivers and floodplains are generally better represented than mountainous terrain. [2]

Try this thought experiment.

One animal dies on a muddy river floodplain and is soon covered by sediment. Another dies on an exposed hillside.

Before considering their species or size, ask:

• Which is more exposed to weathering and scavenging?
• Which is more likely to be buried?
• Could water move either animal’s remains?
• Might their eventual resting place differ from where they lived?

A fossil’s location is evidence to interpret. It is not automatically an exact map of the organism’s original home.

Practical investigation 1: Which materials survive burial?

Suitable for: families, GCSE students and A-level discussion
Time: about 30–45 minutes to set up, followed by observations over 4–6 weeks

This investigation compares the early survival of biological materials under different conditions.

It is a decay and preservation investigation. It will not turn the samples into geological fossils.

Choose the materials

A manageable selection is:

• clean, empty shells;
• leaves from one plant;
• small twigs;
• pieces of apple peel or another soft plant material.

For the separate impression activity, you could also use a clean craft feather and a bone replica.

Real bone is unnecessary. A plastic replica can model shape but cannot model the decay, chemistry or mineralisation of bone.

Use small quantities of plant material and avoid raw meat, animal carcasses or unknown animal remains. Wear gloves when handling soil and old samples, cover cuts and wash hands afterwards. Keep containers away from food preparation areas. Do not sniff samples or bring visibly mouldy material into the classroom; an adult should dispose of affected containers without further disturbance.

Ask a precise question

Rather than changing several conditions at once, start with:

“Does initial sediment moisture affect how much recognisable material remains after four weeks?”

Use the same clean sand or other chosen sediment throughout. Compare a measured dry treatment with a measured damp treatment.

Do not call a damp container “oxygen-free”. Oxygen availability has not been measured, and moisture alone does not establish it.

Set up a fair comparison

1. Photograph each material beside a ruler.
2. Prepare similar-sized samples of each material.
3. Place samples in separate labelled containers so that materials do not overlap.
4. Use the same sediment mass and burial depth in every container.
5. Add the same measured amount of water to each damp-treatment container. Add none to the dry treatment.
6. Keep containers in the same shaded location with the same type of ventilated cover.
7. Prepare at least three independent containers for each material in each treatment.
8. Record the starting conditions and examine the samples after four weeks.

For four materials, two treatments and three repeats, that means 24 containers.

If you want to compare several retrieval dates, prepare a separate set for each date. Repeatedly digging up and reburying the same sample changes its exposure and may damage it.

Keep a simple record of container mass or moisture changes during the investigation. If you replenish evaporated water, use a consistent method and record the amount. A ventilated dry treatment may absorb moisture from the air, so describe the actual conditions rather than assuming they stayed perfectly dry.

Decide what “survived” means

A sample does not have to disappear completely to lose useful information.

Record several features separately:

Observation	What to record
Recognisable outline	Clear, partial or absent
Surface detail	Veins, ridges or texture still visible?
Fragmentation	Intact, cracked or broken into pieces
Colour	Change compared with the starting photograph
Recovery	Was the sample found, and how easily?

Photograph the recovered material under similar lighting, with a ruler.

For a simple graph, use a defined score:

• 0 = no recognisable material recovered;
• 1 = fragments recovered, original form unclear;
• 2 = original form partly recognisable;
• 3 = original form clearly recognisable.

This is an ordered description, not a precise measurement of the amount of tissue remaining. Show individual results as well as any summary.

A score of 0 means “not recovered”, which is not necessarily the same as “completely decomposed”. Small fragments may have been missed.

Predict first, then observe

Which will retain the most recognisable detail: shell, twig, leaf or apple peel?

Ask students to explain their predictions before retrieval.

Do not promise a particular result. Some materials may change very little within four weeks. That is a result to discuss, rather than a reason to invent a more dramatic conclusion.

The strongest conclusion will be limited:

“Under our conditions, these materials retained recognisable features better than those materials.”

It will not be:

“We have proved which organisms fossilise.”

Practical investigation 2: Which objects leave the clearest impressions?

Time: 30–45 minutes

This quicker activity investigates a different question:

“How much information can an impression preserve?”

You will need

• soft clay or reusable modelling clay;
• a clean shell;
• a leaf with visible veins;
• a small twig;
• an optional clean craft feather;
• a ruler and camera.

Flatten equal-sized clay pads to a similar thickness. Press each object gently into a pad, then lift it away.

Try to keep the pressing method consistent. Complete at least three impressions of each object.

Compare the original with the impression:

• Can you identify the outline?
• Which surface details survived?
• Did pressing distort the object?
• Can you infer its original thickness?
• What can you no longer tell about its colour or composition?

For an extension, compare a fine clay surface with damp fine sand. Keep the objects and pressing method as similar as possible.

Clay is a useful model of impression formation; it does not reproduce the full range of natural sediment properties or geological changes.

Challenge someone to identify the evidence

Hide the original objects and ask another student to identify the impressions.

A leaf outline might be obvious while its species remains uncertain. A shell may preserve ridges beautifully but reveal nothing about the animal’s behaviour.

This introduces the difference between having evidence and having enough evidence to answer a particular question.

An impression of a body part records that structure. A footprint records an activity. Both can provide evidence of life, but they tell different kinds of stories.

Not every fossil is a skeleton

Fossils include more than bones and shells.

Body fossils preserve evidence of organisms themselves. Trace fossils, such as tracks and burrows, record their activities. Microscopic fossils, including pollen and tiny shelled organisms, can also contribute to reconstructing past environments. [3]

This helps answer the question:

“If an animal’s body was never preserved, how could we know it existed?”

Sometimes its activity leaves evidence even when its body does not.

A trackway may show that an animal crossed a surface. A burrow may reveal an organism living within sediment.

But there are limits. A footprint does not always identify an exact species. A burrow does not necessarily reveal the complete anatomy of its maker.

Ask students to separate three statements:

1. What can we observe?
2. What can we reasonably infer?
3. What remains uncertain?

That distinction is useful in every experimental science.

Exceptional fossils show us what we usually miss

Soft tissues can sometimes be preserved under unusual conditions. Exceptional fossil deposits may retain fine details that are absent from more ordinary collections. [2]

These discoveries matter because they broaden our view of ancient life beyond the organisms and structures that normally survive.

However, an exceptionally preserved site is still a sample of a particular environment and set of circumstances. It does not remove every bias.

A useful question is:

“Does this discovery show us a more complete community, or a different selection from it?”

Often, scientists must investigate both possibilities.

Missing evidence is not automatically evidence of absence

Suppose students recover many shells from a sediment sample but no soft-bodied animals.

Can they conclude that soft-bodied animals never lived there?

No. Poor preservation is one possible explanation.

Could the absence still matter?

Yes. It becomes more informative if comparable organisms would be expected to preserve, suitable rocks have been sampled thoroughly, and the sampling method could detect them.

“We did not find it” and “it was never there” are different claims.

Equally, an incomplete record does not mean that every imagined organism existed. Scientific explanations must remain tied to evidence.

Taphonomy helps researchers judge what a gap can reasonably tell them.

A classroom model of a biased sample

Imagine an ancient community containing:

• 100 soft-bodied animals;
• 20 shelled animals.

Now suppose, purely for illustration, that the recoverable fossil record contains:

• 1 soft-bodied animal;
• 10 shelled animals.

Shelled animals were a minority in the original community but dominate the recovered sample.

These are invented numbers for teaching, not measured fossilisation rates.

The lesson is straightforward:

The most common fossil in a collection was not necessarily the most common organism in the living community.

For an A-level extension, ask students to explain why counts of fossils cannot simply be converted into original population sizes without considering preservation, transport and sampling.

Why I would use this in tuition

What appeals to me about this investigation is the change in the questions students are encouraged to ask.

“Which fossil is this?” is a good starting point.

“How did this evidence survive?” takes the thinking further.

In my home laboratory, I would pair the immediate satisfaction of making an impression with the slower burial investigation. One produces something to examine within minutes; the other asks students to predict, wait, compare and reconsider.

It also gives biology, chemistry and geology a shared purpose. Students consider biological structures, decomposition, material properties, sediment and the interpretation of incomplete evidence.

At Hemel Private Tuition, this is the kind of practical enquiry I want to encourage: using observations to build an explanation, then checking how far that explanation can go.

The wider thinking extends well beyond a particular examination specification, even where fossils and evolution are already familiar syllabus topics.

The missing pages are part of the lesson

The fossil record has revealed an astonishing amount about the history of life.

Its incompleteness does not make it useless. It makes understanding preservation essential.

A shell, a leaf impression and a trackway each carry information. Each also leaves questions unanswered.

The next time you look at a fossil, ask two things:

“What does this show me?”

“What had to happen for this evidence to reach me?”

The history of life includes everything that once lived. The fossil record contains the evidence that survived.

Learning to understand the difference is part of learning to think scientifically.

 

The Birthday Paradox — Why 23 People Are Enough

Put just 23 people in a room and there is already a better-than-even chance that two share a birthday. How can that possibly be true?

Best level: GCSE upwards
Area: Probability, complementary events, combinations and simulation
Investigation time: 20–40 minutes, with optional spreadsheet extensions

Make Your Guess Before Reading On

How many people would you need in a room before there is at least a 50% chance that two of them share a birthday?

By birthday, we mean the same day and month. They do not need to have been born in the same year.

Would you choose 100 people? Perhaps 150? Or would you halve 365 and suggest about 183?

The answer, under the usual simplified assumptions, is just 23.

With 23 people, the probability of at least one matching birthday is approximately 50.73%.

This is called the birthday paradox. There is no mathematical contradiction: the result simply conflicts with what many people expect.

What appeals to me as a teacher is that the surprise gives us a reason to investigate. A probability calculation becomes much more interesting when it challenges an answer we felt quite confident about.

The Question Your Brain May Have Answered Instead

Imagine standing in a room with 22 other people.

If you ask, “Does anyone here share my birthday?”, you are looking for one particular date. Each of the other 22 people gives you another opportunity to find it.

Under our simplified model, the probability that at least one of them shares your birthday is only about 5.86%.

But that is not the birthday paradox question.

We are asking:

“Do any two people in the room share a birthday?”

Two people on the other side of the room could share 17 March. Another pair could share 4 October. Your own birthday does not have to be involved at all.

Changing “my birthday” to “any birthday” changes the problem enormously.

This is a useful habit for students: before choosing a formula, say clearly what event you are trying to measure.

Twenty-Three People Create 253 Pairs

Start with a smaller group.

With two people, there is one pair to compare.

Add a third person and there are two new comparisons: the newcomer with each person already present. That gives three pairs altogether.

The fourth person adds three more comparisons. The fifth adds four.

For n people:

Number of pairs = n x (n - 1) / 2

We divide by two because comparing Alice with Ben is the same pair as comparing Ben with Alice.

For 23 people:

Number of pairs = 23 x 22 / 2 = 253

That is the first clue. A modest-sized group produces a surprisingly large number of comparisons.

However, 253 pairs does not mean 253 independent attempts. In particular, if Alice shares Ben's birthday and Ben shares Chloe's, Alice must share Chloe's too.

The pair count explains the intuition, but it does not by itself give the exact probability.

Solve the Opposite Problem First

Trying to count all the ways birthdays can match soon becomes awkward.

There could be one matching pair, two separate pairs, three people sharing a date, or several overlapping groups.

Fortunately, the opposite event is much easier:

Everyone has a different birthday.

For this calculation, assume that:

• There are 365 possible birthdays; we leave out 29 February.
• Every date is equally likely.
• Different people's birthdays are independent.

Now imagine people entering the room one at a time.

Person 1: Any birthday is acceptable. There is nobody to match.

Probability of keeping all birthdays different = 365/365.

Person 2: Must avoid the first person's birthday.

Probability = 364/365.

Person 3: If the first two birthdays are different, must avoid both dates.

Probability = 363/365.

Person 4: Must avoid the three different dates already present.

Probability = 362/365.

Continue until person 23, who must avoid 22 dates:

Probability = 343/365.

Multiply these successive conditional probabilities:

P(no shared birthday) = (365/365) x (364/365) x (363/365) x ... x (343/365)

This gives approximately 0.4927.

Either everyone has a different birthday, or at least two people share one. These are complementary events, so their probabilities add to one.

P(at least one shared birthday) = 1 - P(no shared birthday)

P(at least one shared birthday) = 1 - 0.4927 = 0.5073

That is approximately 50.73%.

For 22 people the probability is about 47.57%, so 23 is the smallest group size that passes 50% in this model.

How Quickly Does the Probability Rise?

People in the room	Different pairs	Chance of at least one shared birthday
10	45	11.69%
20	190	41.14%
23	253	50.73%
30	435	70.63%
40	780	89.12%
50	1,225	97.04%

By 50 people, a match is very likely. But even 97.04% is not a guarantee.

In this 365-date model, a match becomes certain at 366 people. If you put 366 people into 365 birthday categories, at least one category must contain more than one person. This is an example of the pigeonhole principle.

Notice the distinction between likely and certain. Probability questions often depend on it.

Practical Investigation: Test a Real Group

A class, family gathering or club meeting provides a good starting point.

1. Ask everyone to predict whether there will be a match.
2. Record birthdays by day and month only; birth years are unnecessary.
3. Agree in advance how to treat 29 February. For a direct comparison with the model, use simulated dates instead if this creates a complication.
4. Check for repeated dates.
5. Compare what happened with the prediction for that group size.

Participation can be voluntary, and anonymous date slips work well.

The important discussion comes afterwards.

A room of 23 people without a match has not disproved the mathematics. That outcome has a probability of about 49.27%: it is entirely ordinary.

Equally, finding a match in a group of ten does not disprove an 11.69% prediction. Less likely events still happen.

One group gives one outcome. To investigate the probability properly, we need many repeated groups.

Simulate Birthdays Without Finding Hundreds of Volunteers

Label the possible birthdays with the integers 1 to 365. We do not need actual calendar dates because we are only checking whether two values match.

For one simulated room of 23 people:

1. Generate 23 independent random integers between 1 and 365.
2. Look for any repeated number.
3. Record “match” or “no match”.
4. Generate a completely new room and repeat.

If using numbered slips, replace and mix each slip after every draw. Drawing without replacement would prevent the very repeats we are investigating.

After many rooms:

Estimated probability = rooms containing at least one match / total rooms tested

For example, if 512 out of 1,000 simulated rooms contain a match:

Estimated probability = 512/1000 = 0.512 = 51.2%

This is an illustrative result, not a reported experiment. Your results will vary.

A larger simulation generally gives a more stable estimate, but it does not guarantee that every new batch moves closer to the theoretical answer.

A Spreadsheet That Makes the Pattern Visible

Use Excel or Google Sheets to simulate 1,000 rooms.

Each row represents one room; each of 23 columns represents one person.

1. In A2, enter =RANDBETWEEN(1,365).
2. Fill across to W2, then down to row 1001.
3. In X2, enter =IF(SUMPRODUCT(COUNTIF(A2:W2,A2:W2))>23,1,0).
4. Fill X2 down to X1001.
5. In a separate cell, enter =AVERAGE(X2:X1001) and format it as a percentage.

The formula in column X returns 1 when a room contains a match and 0 otherwise. If all 23 values are different, each occurs once and the count total is 23. Any duplicate pushes the total above 23.

Random-number formulas recalculate. Copy and paste values if you want to preserve a particular set of results before discussing it.

Repeat the investigation for 10, 20, 30, 40 and 50 people, adjusting the row range and the comparison number in the match formula. For example, 30 people require A2:AD2 and a comparison with 30.

Before running each simulation, predict the result. Then compare the experimental percentage with the table.

Three Tempting Mistakes Worth Discussing

“Surely the answer is about half of 365?”

This treats the calendar as though birthdays were filling dates without repetition. In our model, each new person can have any of the 365 birthdays, including one already present.

“There are 253 pairs, so the probability is 253/365.”

253/365 is about 0.693, but it is not the probability of at least one match.

It is the expected number of matching pairs. A room can contain several matching pairs, so that average count is different from the probability that a room contains any match at all.

Simply adding pair probabilities counts some rooms more than once.

“A 50% chance means exactly half our rooms must match.”

Probability describes a pattern across repeated trials. It does not impose a quota on a small experiment.

Even the theoretical probability here is slightly above 50%, rather than exactly half.

How Realistic Is the Model?

Real birthdays are not perfectly evenly distributed throughout the year. Leap days exist, and groups involving twins or selected birth dates can differ from a collection of independent random birthdays.

Those details affect the precise probability. The table describes a mathematical model, not an exact forecast for every real gathering.

That makes a useful extension: how would the result change if some dates were much more common than others?

As an extreme thought experiment, imagine that everyone could be born on only ten equally likely dates. Matches would become common in much smaller groups.

Students can explore a less extreme version by simulating a deliberately uneven distribution and comparing it with the uniform model.

Why I Like This as a Maths Lesson

The birthday paradox brings together several habits I want students to develop:

• Define the event before calculating.
• Count comparisons carefully.
• Look for an easier complementary event.
• Distinguish a model from the real world.
• Compare experimental evidence with a theoretical prediction.

It also gives students permission to revise an initial guess. Being surprised is a useful starting point for learning.

At Hemel Private Tuition, I want students to see mathematics as something they can question, test and explain. Investigations like this can begin with GCSE probability and develop into combinations, conditional probability and computer simulation.

The most valuable moment is when a student can explain why the answer makes sense, rather than simply remember the number 23.

The Real Surprise Is the Number of Connections

Twenty-three people do not seem like many. Two hundred and fifty-three possible pairs feel rather different.

Our intuition notices the people. The mathematics makes us count the relationships between them.

That is the lasting lesson: when a problem involves any pair matching, the number of opportunities can grow much faster than we first expect.

Next time you are in a room of around 23 people, make a prediction. Then ask about birthdays. A familiar group can become a surprisingly good mathematics laboratory.

 

Can We Make Light Turn Back? From Refraction to Optical Fibres

Put a pencil into a glass of water and it appears bent. Shine a narrow beam into a transparent block and its direction changes. Keep adjusting the experiment, however, and something more surprising happens: the light stops emerging through one surface and returns into the block.

There is no silver coating. No mirror has been added.

The boundary itself produces total internal reflection.

This is an experiment I would build a whole lesson around. It connects observation, careful measurement and mathematical prediction, then leads naturally to the optical fibres that carry information as light.

The journey is:

Reflection → refraction → critical angle → total internal reflection → optical fibres.

The real value comes from letting students discover why each stage follows from the previous one.

Begin with Snell’s Law — and Give the Symbols Meaning

Snell’s law describes what happens when light crosses a boundary between materials:

n1 x sin(i) = n2 x sin(r)

Here:

• n1 is the refractive index of the material the light is travelling from;
• n2 is the refractive index of the material it is entering;
• i is the angle of incidence;
• r is the angle of refraction.

Both angles are measured from the normal: an imaginary line perpendicular to the surface where the ray meets it.

They are not measured from the surface itself.

Refractive index relates the speed of light in a material to its speed in a vacuum:

n = speed of light in a vacuum / speed of light in the material

For an oblique ray, entering a higher refractive index material bends the ray towards the normal. Entering a lower refractive index material bends it away. At normal incidence, light can change speed without changing direction. OpenStax

I would introduce the equation alongside a visible beam. Before students enter numbers into a calculator, ask them to point to the angles the symbols describe.

That small step can reveal a misunderstanding before it becomes a page of incorrect calculations.

What You Need

For an investigation lasting around 45–60 minutes:

• A school ray box with a single narrow slit.
• A semicircular transparent acrylic block.
• A small plane mirror.
• Plain paper, a sharp pencil, ruler and protractor.
• A calculator in degree mode.
• White card to help locate emerging light.

A rectangular block is useful for investigating refraction, but a semicircular block makes the transition to total internal reflection easier to control.

Work in subdued lighting while keeping enough light to read instruments and move safely. Keep beams below eye level and never look into the source or emerging rays. A ray box is sufficient; lasers require appropriate educational equipment, beam stops and their specified safety controls. Ray-box lamps can become hot.

A practical observation: the beam may be easier to follow across the paper than inside a very clear block. Mark the visible incident and emerging paths, then reconstruct the internal ray.

Stage 1: Establish the Law of Reflection

Stand the mirror along a line drawn on the paper.

Direct the ray towards it and mark two points along both the incident and reflected paths. Draw the normal at the point of incidence and measure the angles.

Angle of incidence = angle of reflection

Repeat at several angles.

Then ask:

“If we replace the mirror with a transparent surface, will all the light pass through?”

Students may expect transparent materials to transmit everything. Looking for a reflected ray as well as a refracted ray makes the next stage more interesting.

Stage 2: Measure Refraction from Air into Acrylic

Place the semicircular block on the paper and trace its outline.

Mark the midpoint of its flat face. This is the centre of the circle from which the block was cut. Draw a normal through that point.

Direct the beam from air onto the midpoint of the flat face, initially at about 20 degrees to the normal.

Mark:

• Two points along the incident ray.
• The point where the light leaves the curved face.

Because the internal ray starts at the circle’s centre, it reaches the curved face along a radius. It therefore meets that face normally and leaves without another change of direction.

Remove the block and draw the internal path from the midpoint to the exit point. Measure the incidence and refraction angles at the flat face.

Repeat for incident angles of approximately 30, 40, 50 and 60 degrees, replacing the block accurately each time.

Turn measurements into a refractive index

Suppose you measure:

i = 40 degrees

r = 25.5 degrees

Taking the refractive index of air as approximately 1:

n_acrylic = sin(i) / sin(r)

n_acrylic = sin(40 degrees) / sin(25.5 degrees)

n_acrylic = approximately 1.49

These are illustrative values, rather than results students should be expected to reproduce exactly.

For a stronger investigation, plot:

Vertical axis: sin(i)

Horizontal axis: sin(r)

For air-to-acrylic measurements, the gradient estimates the acrylic’s refractive index.

Ask why a graph using several measurements is generally more persuasive than one apparently perfect result.

Stage 3: Reverse the Journey

Now arrange for the light to travel inside the acrylic towards the flat acrylic–air boundary.

This is essential.

Simply increasing the angle of a beam entering acrylic from air will not produce total internal reflection at that entry surface.

Leave the block on its outline. Send the beam into the curved face, aiming along a radius towards the midpoint of the flat face.

The beam enters the curved face along its local normal, so it does not change direction there. Its first significant change of direction occurs when it reaches the flat face from inside.

Begin with a small internal incidence angle.

The emerging ray bends away from the normal.

Now move the source around the fixed block, always keeping the beam aimed along a radius towards the same midpoint. Increase the internal incidence angle in small steps.

Measure that angle at the flat face, inside the acrylic.

Do not measure it against the curved surface.

Stage 4: Find the Critical Angle

As the internal incidence angle increases, the emerging ray approaches the flat surface.

Near the transition, make smaller adjustments and use white card to locate the emerging beam.

At the critical angle, the refracted angle reaches 90 degrees to the normal. In the ideal ray diagram, the refracted ray runs along the boundary.

Above this angle, total internal reflection occurs. The two requirements are:

• Light approaches the boundary from the higher refractive index material.
• Its incidence angle exceeds the critical angle. OpenStax

In practice, a beam has finite width and some spread of directions. The transition may look less sharp than a textbook drawing.

Record a small angular range within which the emerging beam disappears, rather than claiming unrealistic precision.

Predict the turning point

At the critical angle, substitute r = 90 degrees into Snell’s law:

n1 x sin(c) = n2 x sin(90 degrees)

Since sin(90 degrees) = 1:

sin(c) = n2 / n1

For acrylic with refractive index 1.49, surrounded by air:

sin(c) = 1.00 / 1.49

c = inverse sine(1.00 / 1.49)

c = approximately 42.2 degrees

Use the inverse sine function with the calculator in degree mode.

Now compare prediction and observation.

Does 42.2 degrees fall within the transition range you recorded? If it does not, check the alignment and angle measurements before deciding the physics has failed.

Stage 5: Watch the Light Return

Increase the internal incidence angle beyond the critical angle.

The light reflects back into the acrylic at the flat surface.

Look for its subsequent exit through the curved face. Total internal reflection at one boundary does not mean the beam remains trapped inside the entire block indefinitely.

The reflected ray still obeys:

Angle of incidence = angle of reflection

I particularly like the teaching opportunity here. A student who predicts the transition before observing it has used mathematics to anticipate a physical event.

What should the results look like?

These are calculated predictions for acrylic with refractive index 1.49 and air with refractive index 1.00.

Internal incidence angle	Predicted refracted angle	Expected observation
20 degrees	About 30.6 degrees	Emerging ray bends away from the normal
30 degrees	About 48.2 degrees	Emerging ray moves nearer the surface
40 degrees	About 73.3 degrees	Emerging ray travels at a shallow angle to the surface
About 42.2 degrees	90 degrees in the ideal model	Critical-angle limit
45 degrees	No propagating refracted ray	Total internal reflection at the flat face

Students can add their measured values in another column and explain differences.

When the Calculator Reveals a Physical Limit

Try calculating the refracted angle for an internal incidence angle of 45 degrees:

sin(r) = 1.49 x sin(45 degrees)

sin(r) = approximately 1.054

But the sine of a real angle cannot exceed 1.

No refracted ray angle satisfies Snell’s law for this arrangement.

This gives total internal reflection a mathematical explanation as well as an observable one.

For interested A-level students, a further subtlety is that an evanescent electromagnetic field extends a short distance beyond the boundary. The elementary ray description concerns the absence of a propagating transmitted beam into the second material.

From the Block to an Optical Fibre

An optical fibre extends this boundary behaviour along a narrow guide.

In a simple step-index fibre:

• The central core has a higher refractive index.
• The surrounding cladding has a lower refractive index.
• Suitable rays meet the core–cladding boundary above the critical angle and remain guided along the core. OpenStax

The material outside the core does not have to be air.

An educational optical-fibre kit or curved acrylic light guide makes a useful follow-up. Couple light into one end and observe the output.

Compare gentle curves with tighter bends, staying within the equipment’s bend limits. Ask students to sketch how changing the guide’s shape could alter the angle at which a ray meets its boundary.

That makes “light travelling round a bend” something they can reason about.

The familiar zigzag diagram is a useful model, particularly for a multimode step-index fibre. More advanced explanations use guided waves and modes.

How does a fibre carry information?

A simple classroom explanation has three stages:

1. A transmitter encodes information by varying light.
2. The fibre guides the optical signal.
3. A receiver detects it.

Real communications systems use more sophisticated encoding than a simple on–off sketch, but the connection with the practical remains powerful.

Also distinguish total internal reflection at a boundary from transmission through a complete system. Absorption, scattering, bends and connections can all reduce the signal.

Five Questions That Reveal Understanding

1. Why does light entering along the normal continue straight?

Its direction is unchanged, although its speed and wavelength can change.

2. Why use a semicircular block?

Radial alignment avoids directional bending at the curved face, isolating the flat boundary being investigated.

3. Can light travelling from air into acrylic undergo total internal reflection at entry?

No. It is travelling towards the higher refractive index material.

4. Is the critical angle 90 degrees?

No. The refracted angle is 90 degrees. The critical angle is the corresponding incidence angle inside the higher-index material.

5. Does reflection only begin above the critical angle?

No. Below it, reflected and transmitted light can both be present.

These questions also expose a limitation of memorising:

sin(c) = 1/n

That shortened expression assumes the second material is approximately air. The general relationship uses both refractive indices.

Make It a Genuine Investigation

Once the basic progression works, students can extend it.

Compare materials. Predict which material should have the smaller critical angle into air, then test the prediction.

Estimate uncertainty. Approach the transition from increasing and decreasing angles. Consider beam width, alignment and protractor resolution.

Test the alignment. Deliberately aim slightly away from the circle’s centre. Explain why extra refraction complicates the experiment.

Create a visual record. Photograph the setup from directly above at several incidence angles.

For my home laboratory and teaching studio, the overhead view is particularly appealing. A sequence of images would let students compare the stages without relying on memory.

Any lines added afterwards should be identified as annotations, especially where they reconstruct an internal path the camera cannot show clearly.

Why I Would Teach This as One Connected Story

Reflection and refraction are often practised as separate sets of diagrams. The critical angle becomes another equation, while optical fibres appear as an application at the end.

I would bring them together around one question:

“What happens if we keep increasing the angle?”

That question gives students a reason to measure, calculate and look again.

Unexpected observations become useful too: a faint reflected ray below the critical angle, an emerging beam that is difficult to locate, or a result that changes when the block slips.

At Hemel Private Tuition, this is the practical approach I value. Observations give the equations meaning, and the equations help students explain what they observe.

Conclusion: A Small Change of Angle, a Bigger Understanding

A transparent block, a narrow beam and a protractor can reveal a complete chain of ideas.

Students establish reflection, measure refraction, predict a critical angle and observe total internal reflection. They can then explain how the same boundary behaviour helps guide light along an optical fibre.

The most valuable outcome is the ability to connect those stages in their own words.

Light meets a boundary. We change the angle. A new question appears.

That is a strong foundation for learning physics: observe carefully, make a prediction, test it and explain the result.

If your child finds GCSE or A-level Physics difficult to connect with, Hemel Private Tuition brings practical observations, mathematical reasoning and exam technique together, in Hemel Hempstead and online.

 

Observe Cytoplasmic Streaming — The Inside of a Cell Is Moving

A plant cell in a textbook looks wonderfully organised. There is a cell wall around the outside, a large vacuole in the middle and green chloroplasts arranged around the edge.

Everything has a label. Everything stays where it has been drawn.

Then you look at a living leaf through a microscope.

At first, the view seems familiar: rows of cells, clear boundaries and little green bodies. Keep watching one cell, however, and you may notice something unexpected.

Some of those green bodies are moving.

You are watching activity inside an individual living cell. With a microscope camera and a large monitor, this small observation can become a memorable shared experience.

A Living Cell Is More Than a Labelled Diagram

Diagrams help students identify structures, but they can leave the impression that a cell is a container of stationary parts.

Cytoplasmic streaming, also called cyclosis, challenges that picture. It is the movement of cytoplasm within a cell. In suitable living aquatic plant leaves, moving chloroplasts provide visible markers of this internal activity. The Exploratorium uses Elodea videos to help learners explore this connection between structure and movement. Exploratorium

For me, this is the value of practical biology: a familiar diagram becomes something students can question.

Instead of asking only, “Can you label the chloroplast?”, we can ask:

“Where is it going, and how could we measure its movement?”

What Is Making the Inside Move?

Cytoplasmic streaming involves the cell’s internal framework and molecular motors.

Actin filaments form tracks. Myosin motor proteins move associated cellular cargo along them, drawing surrounding cytoplasm into motion. This actin–myosin system is central to plant cytoplasmic streaming. arxiv.org

The chloroplasts do not have little propellers. Their movement helps us detect an active transport system within the cell.

A useful analogy is a network of moving deliveries inside a building. However, the cell is a three-dimensional, fluid environment: different components need not move together at one uniform speed.

There is also an important distinction between what we see and what we explain.

We observe chloroplast movement directly. The molecular explanation comes from wider biological research. An ordinary school microscope cannot resolve the individual motor proteins responsible.

Why Might Internal Movement Matter?

Diffusion moves substances over short distances, but becomes less effective for transport over larger distances. Internal flow can help mix and distribute material.

Cytoplasmic streaming therefore connects with a wider biological question:

How does a living cell organise transport within its own boundaries?

Science & Plants for Schools describes streaming as a possible adaptation that increases mixing within large plant cells, and provides a practical investigation of chloroplast speed using Egeria densa. Science & Plants for Schools

This makes an excellent extension to GCSE and A-level discussions of diffusion, cell size and transport.

The Practical: Watch a Living Leaf

Allow approximately 45–60 minutes for preparation, observation and recording. Measurement can become a follow-up activity.

What You Need

• A compound light microscope with transmitted illumination.
• Fresh, healthy Elodea or another suitable aquatic plant supplied for microscopy.
• A clean microscope slide and coverslip.
• A dropper, fine forceps and water from the plant’s container.
• A microscope camera, or a phone with a secure eyepiece adaptor.
• A computer or monitor for shared viewing.
• A stage micrometer if you want to measure actual distances.

Plant identity matters. Aquarium plants sold under similar common names are not necessarily the same species or equally suitable.

Use responsibly sourced material, keep aquatic plant fragments out of ponds, rivers and drains, and follow the supplier’s disposal guidance. Handle glass carefully and keep water away from electrical equipment.

1. Prepare a Thin, Unstained Wet Mount

Place a drop of the plant’s water on a slide.

Using forceps, remove a small, healthy leaf near the growing tip. Lay it flat in the drop and lower a coverslip gently at an angle to reduce trapped air.

Do not press on the coverslip. A crushed leaf may show recognisable structures but poor living activity.

Leave the specimen unstained. The green chloroplasts already provide contrast, and the aim is to observe living cells.

2. Find the Cells Before Looking for Movement

Begin with the low-power objective. Locate a flat, clearly visible region, then increase magnification.

With a 10x eyepiece:

total magnification = eyepiece magnification x objective magnification

10x x 10x = 100x

10x x 40x = 400x

Around 100x helps you locate suitable cells; 400x often provides a useful closer view. Use fine focus at higher power and keep the objective clear of the coverslip.

Higher magnification helps only if the image remains clear.

3. Stop Moving the Slide and Start Watching

Choose a cell with sharp boundaries and distinct chloroplasts. Focus on one layer of the leaf rather than trying to see its full thickness at once.

Take your hands away from the stage controls.

Watch the same cell for a minute or two. Look for a chloroplast changing position relative to a fixed point on the cell wall.

You may see chloroplasts following paths around the cell’s periphery. Movement can be uneven, and some chloroplasts may remain stationary.

Do not expect every cell to show a perfect circulating procession. Finding a suitable living preparation is part of the investigation.

Why Are Many Chloroplasts Near the Edge?

A large central vacuole occupies much of the space in a mature plant cell. Much of the cytoplasm forms a relatively thin layer around it, helping explain why chloroplasts are often seen near the boundary.

The clear-looking centre is not simply an empty hole. Nor should a moving chloroplast be assumed to be travelling through the vacuole. Elodea teaching videos illustrate streaming around this central region. Exploratorium

Ask students to sketch what they can actually see first. Then add a separate interpretation of the structures responsible.

That small change helps distinguish observation from inference.

Is It Streaming—or Is the Whole Image Moving?

Before announcing success, check the cell walls.

Observation	What to consider
Chloroplasts move while the cell wall stays fixed	Consistent with movement inside the cell
Cell walls and chloroplasts slide together across the screen	Slide, camera or stage drift
Tiny particles jitter without a sustained path	Could involve Brownian motion; this alone does not establish streaming
Chloroplasts slowly redistribute after illumination changes	May involve a light response as well as internal transport

Keep the first investigation simple: use stable illumination, let the preparation settle and track movement against a fixed cell boundary.

Put the Cell on a Large Monitor

A microscope camera allows everyone to follow the same chloroplast together.

This is especially useful when a learner is unsure what counts as movement. On a shared screen, you can point to a fixed corner of the cell, choose a nearby chloroplast and return to it several seconds later.

Ask viewers to predict its next position before showing the next section of video.

In my teaching, I want practical work to create opportunities for students to explain what they notice. A shared image makes that conversation much easier than taking turns at an eyepiece.

Record Real Time First, Then Make a Time-Lapse

Secure the camera or phone so it cannot wobble. If the camera allows it, lock focus and exposure once the image is clear.

Record 30–60 seconds at normal speed. Keep the original file.

You can then make a faster version for a blog or social post:

playback speed-up factor = original duration / edited duration

60 seconds / 10 seconds = 6

Label the edited clip:

“6x speed — 60 seconds shown in 10 seconds.”

Continuous video played faster is a simple alternative to capturing separate time-lapse frames. Either approach should preserve a reliable record of the original timing.

Use original elapsed time for calculations. A chloroplast does not move faster because we make the video play faster.

Can We Measure How Fast a Chloroplast Moves?

Yes—provided we calibrate the image.

A microscope’s magnification label does not tell you the actual distance represented by a centimetre on a monitor. Camera settings, cropping and display size can change that relationship.

Calibrate the Camera Image

1. Put a stage micrometer under the microscope.
2. Record its scale using the same objective and camera settings as the leaf recording.
3. Determine how many pixels represent a known distance.
4. Use that conversion to measure movement in the leaf video.

For example:

200 pixels represent 100 micrometres

distance per pixel = 100 / 200 = 0.5 micrometres

Suppose a chloroplast travels 80 pixels along its visible path in 20 seconds:

distance travelled = 80 x 0.5 = 40 micrometres

speed = distance / time

speed = 40 / 20 = 2 micrometres per second

These are illustrative numbers, rather than a promised result.

Use “micrometres” or “um” if your publishing platform does not display the micro symbol reliably.

Follow the Path

If a chloroplast travels around a bend, the straight line between its first and last positions underestimates the distance travelled.

Trace its position at several intervals and add the short distances, or choose a reasonably straight section of its path.

You are estimating average speed in the image plane. Movement towards or away from the camera is not fully captured by that two-dimensional measurement.

Repeat with several chloroplasts in several cells. Report the spread of results alongside any mean. Multiple tracks from one cell are useful observations, but they are not independent samples of different plants.

When Nothing Seems to Move

A quiet preparation is a reason to troubleshoot.

Problem	Practical response
Overlapping structures	Find a flatter area and refocus on one cell layer
No obvious movement	Observe longer, then try another cell or a fresh leaf
Leaf drying beneath the coverslip	Add a small drop of water at the coverslip edge
Image drifting	Secure the camera and allow the slide to settle
Glare or poor contrast	Adjust illumination and condenser settings
Specimen becoming warm	Reduce illumination and give it a rest

Do not try to force a result with strong heating or intense light. Conditions that stress the specimen can change the activity you are trying to observe.

Turn Observation into an Investigation

Once the basic preparation works, let students choose a question.

Do chloroplasts move at similar speeds within one cell?
Track several over equal intervals and compare their paths.

How much variation is there between cells?
Sample cells systematically, rather than selecting only the fastest or most striking examples.

Does the apparent speed remain constant?
Divide one track into equal time intervals and calculate a speed for each section.

For A-level students, a further challenge is to design a temperature investigation. Before attempting it, they should explain how they would measure the specimen’s temperature, allow equilibration and keep illumination, hydration and recording conditions consistent.

Changing lamp brightness alone is a poor way to test temperature: it changes light conditions at the same time.

What Does This Teach Beyond Cell Biology?

This modest preparation brings together several valuable habits:

• Patient observation before explanation.
• Calibration before measurement.
• Consistent units and sensible calculations.
• Distinguishing biological movement from equipment drift.
• Repeated observations and honest treatment of variation.
• Accurate labelling of edited scientific video.

At Hemel Private Tuition, this is the connection I want students to make between biology, mathematics and evidence.

A student who can calculate speed has one skill. A student who can explain whether that estimate deserves confidence has taken an important further step.

Conclusion: Keep Watching After You Have Named the Parts

A labelled diagram introduces the parts of a cell. A living leaf reveals something a still diagram cannot show.

The cell wall stays in place. Inside it, chloroplasts change position. With careful recording and calibration, an intriguing movement becomes something we can investigate and measure.

The equipment can be modest. The change in understanding can be substantial.

Next time you look down a microscope, identify the structures—then keep watching.

You may discover that the most interesting part of the picture is what happens next.

 

“She’s Clever.” “He’s Trouble.” Can a Label Change Someone’s Future?

A label takes seconds to attach. Its consequences may last much longer.

Two pupils call out in the same lesson. One is known for asking good questions. The teacher smiles and says, “Hold that thought.” The other has a reputation for disrupting lessons. The teacher writes his name on the board.

The two pupils have done the same thing. Yet one leaves the exchange with an idea worth hearing, and the other with another entry on his behaviour record. Imagine what might happen if that difference were repeated across a term.

That is a question for A-level Sociology, but it is also one worth asking in a staffroom, at work or around the kitchen table. How much of a reputation comes from what a person does, and how much comes from what other people have already decided to see?

When a description becomes a reputation

“Amir missed two deadlines” is a claim you can check. “Amir is lazy” turns those two events into a judgement about his character. Once that judgement is shared, it can travel ahead of him. A teacher who has never met him might read the same late homework differently after hearing the label.

Labelling is the process of assigning a social meaning or identity to someone. From an interactionist perspective, we can examine how these meanings arise through everyday exchanges and how they shape what happens next. A reputation gathers force when others repeat it, when it changes decisions, or when it becomes part of a record that follows the person.

Think of the employee called “a safe pair of hands”. She gets the first chance to lead a project, meets senior colleagues and has something concrete to show at her next appraisal. Or think of the child known as “the disorganised one”. If a parent always packs his bag for him, he has fewer chances to learn how to do it himself. In each example, what matters is the opportunity that follows the label.

Becker and the “ideal pupil”

In his 1952 study of teacher–pupil relationships, sociologist Howard Becker drew on interviews with Chicago teachers to examine how their ideas about teachability, behaviour and other characteristics varied with pupils’ social class. The idea often taught as the ideal pupil gives students a way to think about this. What picture of a “good pupil” is a teacher using, and whose behaviour fits that picture most easily?

Imagine two pupils who both need help. One confidently asks the teacher to explain a point again and is seen as engaged. The other waits quietly and is seen as indifferent. Those interpretations may tell us as much about what the teacher expects engagement to look like as they do about either pupil’s interest. Becker’s interviews help us investigate the assumptions teachers bring to an encounter. The interviews give us evidence about their accounts and judgements, with more evidence needed to establish the effect on grades. Becker’s 1952 article excerpt

Rosenthal and Jacobson put expectations to the test

Robert Rosenthal and Lenore Jacobson approached the question experimentally. In research reported in 1968, teachers in a US elementary school were told that certain pupils were likely to make unusual intellectual gains. Those pupils had actually been selected at random. The researchers later reported greater gains on the IQ test for the identified group overall, with the clearest differences in the younger year groups.

Random selection matters because it helps separate a teacher’s expectation from information they already had about a pupil’s ability. The finding concerns a particular school, particular age groups and a particular measure. The test scores alone cannot tell us whether teachers gave more thinking time, more encouraging feedback or more demanding work. Those are possible routes that need their own evidence.

For revision, keep the questions distinct. Becker investigated the social judgements teachers make. Rosenthal and Jacobson tested what might happen when researchers changed the expectations teachers were given. Rosenthal and Jacobson’s 1968 report

How a prediction can help bring itself about

Suppose a teacher assumes that Maya will struggle with extended answers. When the class practises a 12-mark question, Maya is asked to finish a definitions sheet instead. A classmate attempts the full question, receives feedback on linking ideas and tries again. After several lessons, the classmate has practised an exam skill that Maya has barely had a chance to use.

When Maya scores poorly on the next extended question, the teacher may see the result as confirmation of the original judgement. Yet the decision about what Maya was given to do helped produce that result. This is a possible self-fulfilling prophecy.

Teacher expects difficulty -> pupil gets fewer chances to practise extended writing -> pupil has less feedback and less opportunity to improve -> a low mark appears to confirm the expectation.

Maya could remain thoroughly unconvinced by the label and still lose out on practice. Alternatively, she might begin to think “I can’t write essays” and avoid attempting them. The first pathway works through opportunity. The second adds a change in pupil identity. Both can operate together.

Positive labels can also change opportunities. A pupil described as “clever” may get more time to work through a difficult answer. That same pupil might also start hiding mistakes to protect the reputation. What follows the label depends on how people use it and how the pupil responds.

What I would want to know as a tutor

If a student tells me, “I’m bad at maths,” I’d want to put a question in front of them and watch where they get stuck. Can they set up the problem? Do they lose track of a negative sign? Can they explain the method aloud but struggle to organise the working on paper? Each answer gives me a different next step.

There’s a practical question for me as well. If I expect a student to struggle, how quickly do I take over? In a science practical, am I giving them time to work out why a reading looks odd, or do I reach for the apparatus and solve the problem myself? I may think I’m helping while taking away the most interesting bit of the experiment.

Try replacing a character judgement with an observation and a next step. “You’ve given the definition. Now show me how it explains what happened in this example.” A student can act on that feedback and see whether the next answer improves.

From the school corridor to crime and deviance

In Outsiders (1963), Becker asked who makes rules, how they are enforced and who comes to be treated as an outsider. Deviance involves behaviour defined as breaking a group’s norms. Crime involves breaking the criminal law. A school sanction offers a small-scale comparison with selective rule enforcement, while a criminal conviction carries very different formal consequences.

Imagine two teenagers painting their names on a wall without permission. One is seen and dealt with formally. The other is never identified. Their actions may be similar, but their recorded histories differ. If the first teenager later becomes known chiefly for that incident, other qualities can recede in the eyes of teachers, neighbours or employers. When one identity dominates how someone is seen, sociologists call it a master status.

The label might close off opportunities, change whom the young person spends time with, or lead to closer scrutiny and therefore more recorded incidents. These are distinct possibilities. An increase in recorded incidents could reflect more detection, more rule-breaking, or both. Labelling helps explain how a deviant reputation develops and what it might do afterwards. To explain the original graffiti, we would need to look at motives and circumstances as well. Becker’s Outsiders, publisher excerpt

Student activity — one label, two routes

Starting point. After missing several homework deadlines, Sam overhears a teacher describe him as “someone who never tries”. Draw two arrow chains from that same starting point.

Stage	Sam accepts the label	Sam resists the label
Adult response	Sam receives shorter tasks and less feedback.	The same teacher offers shorter tasks, but another teacher asks what is causing the missed deadlines.
Pupil response	Sam starts to see effort as pointless and attempts less homework.	Sam rejects the judgement, uses a lunchtime study space and asks to attempt the full task.
Possible outcome	Sam gets less practice and a weak result reinforces the original judgement.	Sam completes more work and produces evidence that challenges the judgement.

Now change one condition. The study room closes, Sam’s friends begin helping him revise, or he has caring responsibilities after school. Mark the arrow your change affects and explain why. Then ask what evidence would distinguish a change in Sam’s confidence from a change in the opportunities available to him.

Essay skill — explain what happens between the label and the result

Try this question. Explain one way teacher labelling may influence educational achievement.

Teachers may interpret a pupil’s low mark as evidence of limited ability and give that pupil less demanding work. This reduces the pupil’s opportunities to practise the extended reasoning assessed in examinations and to get feedback on it. If the pupil later scores poorly on those questions, the result may appear to confirm the teacher’s original expectation, even though the work the teacher allocated helped produce it. This is one way a label can contribute to a self-fulfilling prophecy.

For an evaluation question, test one link in that chain. A pupil might reject the judgement and get demanding work and feedback from another teacher, weakening the link between the original expectation and achievement. Conversely, a pupil who wants to do well may still have little time or space to study at home. Peer support, material circumstances and individual responses help explain why the same label can have different effects.

What happens the next time?

Go back to the pupil whose name went on the board. The next day he puts up his hand and hesitates halfway through an answer. Does the teacher wait? Does she ask him what he means? Or does she move straight to the pupil everyone expects to get it right?

There is no way to know from that moment what either pupil will go on to achieve. But you can see who gets the chance to finish a thought. Multiply that by a term’s worth of lessons and you begin to see how a reputation can shape the evidence people later use to justify it. The next time you hear “She’s clever” or “He’s trouble”, ask what the person gets to do next because someone said it.