What is humidity?
Summary
TLDRThis video script explores how weather affects hair texture, with high humidity causing straight hair to become wavy and curly hair to frizz. It delves into the science behind hair's sensitivity to atmospheric changes, mentioning the first hair tension hygrometer invented by Horace Benedicta Saussier in 1783. The script explains the workings of a wet bulb thermometer, which measures humidity by the rate of evaporation and condensation, and how it differs from a dry bulb thermometer. It also covers the concepts of relative humidity, dew point, and specific humidity, and how they relate to our perception of humidity and its impact on our comfort and hair.
Takeaways
- 🌧️ Weather conditions, particularly humidity, can significantly affect the appearance of your hair, causing straight hair to become wavy and curly hair to frizz.
- 💧 The bonding of hydrogen atoms in water molecules with proteins in hair leads to changes in hair shape, demonstrating hair's sensitivity to atmospheric humidity.
- 🧬 Human hair is so sensitive to humidity that it was used by Horace Benedict de Saussure in 1783 to create the world's first hair tension hygrometer.
- 🌡️ Modern methods for measuring humidity include the use of wet bulb thermometers, which differ from dry bulb thermometers by having a damp cloth around the bulb.
- 💦 The process of evaporation, which requires heat energy known as latent heat, is key to understanding how wet bulb thermometers measure humidity.
- 🚿 When you sweat, the latent heat of evaporation from the moisture on your skin helps cool you down, similar to how a wet bulb thermometer cools as it evaporates.
- 🌬️ The rate of evaporation from the wet bulb of a thermometer indicates the dryness of the air; the drier the air, the lower the wet bulb temperature compared to the air temperature.
- 🌫️ Relative humidity is measured when the rate of evaporation equals the rate of condensation, and it reaches 100% when the air is saturated with water vapor.
- 🌌 The dew point temperature is the point at which the air must be cooled for dew to form, indicating the temperature at which the air is fully saturated with water vapor.
- 🌬️ Specific humidity refers to the amount of water vapor in the air, measured in grams of water vapor per kilogram of air, influencing how humid the air feels.
Q & A
How does humidity affect hair?
-Humidity can cause straight hair to become wavy and curly hair to become frizzy. This is due to hydrogen atoms within water molecules bonding with certain proteins in the hair, altering its shape.
What is the role of hydrogen atoms in water molecules when it comes to hair?
-Hydrogen atoms within water molecules bond with certain proteins within hair, which can cause the hair to change shape in response to changes in atmospheric humidity.
Who built the world's first hair tension hygrometer and in what year?
-Swiss physicist and geologist Horace Benedicta Saussier built the world's first hair tension hygrometer in 1783.
What replaced the hair tension hygrometer for measuring humidity?
-The hair tension hygrometer was replaced by hygrometers that used charcoal, metal coils, and sheep's wool, and nowadays, a wet bulb thermometer is often used instead.
How does a wet bulb thermometer measure humidity?
-A wet bulb thermometer measures humidity by having its bulb wrapped in a damp cloth. The evaporation from the wet bulb causes it to cool down, and the rate of evaporation and condensation can indicate the dryness of the air.
What is latent heat and how does it relate to the feeling of cold after a bath or swimming?
-Latent heat is the heat energy required for water to evaporate. When we get out of the bath or a swimming pool, we feel cold because the evaporation of water on our skin takes away latent heat, helping us to cool down.
How does the wet bulb thermometer's temperature compare to the air temperature in dry air?
-In dry air, there won't be as much condensation, so it will take more evaporative cooling for equilibrium to be achieved, resulting in a lower wet bulb temperature compared to the air temperature.
What does it mean when the wet bulb temperature is the same as the air temperature?
-When the wet bulb temperature is the same as the air temperature, the rate of evaporation and condensation are already equal, indicating that the air is saturated and has 100% relative humidity.
What is the dew point temperature and how is it related to humidity?
-The dew point temperature is the temperature to which air needs to be cooled for dew to form. It is related to humidity as it indicates the temperature at which the air becomes saturated with water vapor.
How does specific humidity differ from relative humidity?
-Specific humidity is related to the amount of water vapor in the air, measured in grams of water vapor per kilogram of air. It differs from relative humidity, which is a percentage that represents the current amount of moisture in the air relative to the maximum amount of moisture the air can hold at a given temperature.
What factors determine how high the dew point needs to be for it to feel oppressively humid?
-The feeling of oppressive humidity depends on subjective factors, including the climate one is accustomed to and the amount of water vapor in the atmosphere, which affects the dew point.
Outlines
🌦️ The Impact of Humidity on Hair
This paragraph discusses how humidity affects hair texture. On humid days, straight hair may become wavy, and curly hair can frizz due to hydrogen atoms in water molecules bonding with hair proteins, altering its shape. Human hair is so sensitive to humidity that it was historically used to measure atmospheric conditions. In 1783, Horace Benedicta Saussier invented the first hair tension hygrometer, which was an advancement over previous hygrometers that used charcoal, metal coils, and sheep's wool. Modern alternatives to these include wet bulb thermometers, which measure humidity by the rate of evaporation from a damp cloth around a thermometer bulb. The paragraph explains the concept of latent heat, which is the energy required for water to evaporate, and how this affects our perception of temperature and the operation of wet bulb thermometers.
Mindmap
Keywords
💡Humidity
💡Water Molecules
💡Hair Tension Hygrometer
💡Wet Bulb Thermometer
💡Latent Heat
💡Evaporation
💡Relative Humidity
💡Dew Point
💡Specific Humidity
💡Clouds and Fog
Highlights
Bad hair days can be attributed to weather conditions, particularly humidity.
On humid days, straight hair may become wavy and curly hair can become frizzy due to water molecules interacting with hair proteins.
Human hair is sensitive to atmospheric humidity changes, making it a potential indicator of humidity levels.
In 1783, Horace Benedicta Saussier built the world's first hair tension hygrometer using human hair.
The hair tension hygrometer replaced earlier hygrometers that used charcoal, metal coils, and sheep's wool.
Modern humidity measurement often utilizes a wet bulb thermometer instead of the hair tension hygrometer.
Air temperature is measured by dry bulb thermometers, while humidity is derived from wet bulb thermometers.
Latent heat is the energy required for water to evaporate, which is why we feel cold when exiting a bath or pool.
Sweating is a body's reaction to heat, as the evaporation of sweat cools us down by removing latent heat.
A wet bulb thermometer's cooling is due to evaporation, which can indicate the dryness of the air.
Evaporation and condensation reach an equilibrium, which is affected by the temperature of the water and air.
The drier the air, the lower the wet bulb temperature compared to the air temperature, indicating less condensation.
When the wet bulb temperature equals the air temperature, the air is saturated, and the relative humidity is 100%.
The dew point temperature is the point at which air needs to be cooled for dew to form.
A dew point of 5 Celsius may not feel humid despite 100% relative humidity, due to the specific humidity of the air.
Specific humidity is related to the amount of water vapor in the air, influencing the dew point and perceived humidity.
The feeling of oppressive humidity is subjective and depends on factors such as climate and personal comfort levels.
The dew point's impact on hair and its perceived 'bad hair day' factor is subjective and open to individual interpretation.
Transcripts
[Music]
are you having a bad hair day
you may be able to blame the weather on
a humid day straight hair can become
wavy and curly hair can become frizzy
hydrogen atoms within water molecules
bond with certain proteins within your
hair
and cause it to change shape in fact
human hair is so sensitive to slight
changes in atmospheric humidity that it
can be used to measure it
in 1783 swiss physicist and geologist
horace benedicta sousier built the
world's first hair tension hygrometer
using human hair
this replaced earlier humidity
instruments known as hygrometers
that used charcoal metal coils and
sheep's wool
nowadays we often use a wet bulb
thermometer
instead whilst air temperature can be
measured by thermometers
whose bulb is dry humidity
is derived from thermometers whose bulb
is swaddled in a damp cloth
water needs heat energy in order to
evaporate
this is called latent heat that's why we
feel cold when we get out of the bath or
swimming pool
or if we get too hot our bodies react by
sweating
sweat or water on our skin takes latent
heat away from our body as it evaporates
helping us to cool down this evaporative
cooling
also affects a wet bulb thermometer and
it can tell us
how dry the air is to understand
why take a bottle of water what you
can't see
are the many tiny molecules of water
that are escaping from the liquid
into the air above the liquid water is
slowly evaporating into water vapor
but there are also many molecules of
water vapor
returning back into the liquid if i put
a lid
on this water eventually the same amount
of liquid molecules are escaping
as vapor molecules are returning
an equilibrium is reached if i remove
the lid
and heat up the water so that it's now
warmer than the air
its molecules move around faster and
more of them
will escape there's an increase in
evaporation
whilst condensation remains the same
back to the wet bulb thermometer at
first it has the same temperature as the
dry bulb thermometer
but evaporation from its wet bulb causes
it to cool down
as the wet bulb cools down its rate of
evaporation
slows down until the rate of evaporation
and condensation
are the same when the air is dry there
simply won't be as much condensation
so it will take more evaporative cooling
for equilibrium
to be achieved the drier the air
the lower the wet bulb temperature
compared to the air temperature
when the wet bulb temperature is the
same as the air temperature
the rate of evaporation and condensation
are already
equal the air is saturated and we say
that the air has 100
relative humidity tiny water droplets
will start condensing onto
any surface for example specks of dust
in the sky above us
to form clouds or fog if it's the air
near the surface that is saturated or
due if it's the air near the ground
that has 100 relative humidity
in fact the dew point temperature is the
temperature the air needs to be cooled
to
for due to form for example when the
temperature drops overnight
just like the wet bulb temperature when
the dew point and
air temperature are the same the air has
100
relative humidity it doesn't mean it
will feel humid
a dew point of 5 celsius won't feel
humid at all whatever the relative
humidity
that's because there's another
definition of humidity
specific humidity this is simply related
to the amount of water vapor in the air
for example how many grams of water
vapor per kilogram of air
the more water vapor in the atmosphere
the higher the specific humidity
and the higher the dew point how high
the dew point needs to be for it to feel
oppressively humid
is subjective it will depend on lots of
different factors including the kind of
climate you're used to
for example if you're used to the
climate of the uk anything higher than a
dew point of 15 celsius may make you
sweat
and how high does the dew point need to
be for a bad hair day
well we'll let you be the judge of that
you
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