Low pressure causes – Dr. Trippers Stuff

what causes low pressure baturally

“Low pressure” can arise *naturally* in a few different contexts—atmospheric, oceanic, or even bodily—depending on what domain you mean.
Here’s the quick, big-picture breakdown:

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### 🌪 **In the Atmosphere**
Low pressure forms when **air warms, expands, and rises**—reducing the weight of the air column above.
Main natural causes:
– **Surface heating:** Sun warms land or water, air rises (e.g., tropical storms, deserts).
– **Converging winds:** Air piles in from high-pressure regions, forcing lift (cyclones).
– **Topography:** Mountains force air up and over, lowering pressure on the windward side.
– **Upper-air dynamics:** Jet streams and Rossby waves create low-pressure troughs aloft that draw air upward.

Result: clouds, storms, and all our dramatic weather.

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### 🌊 **In the Oceans**
Low pressure above oceans draws surface water upward or sideways.
It can also appear locally due to:
– **Warm water expansion** (thermal bulges).
– **Cyclonic systems** sucking air upward and drawing sea level down slightly (the “storm surge” inverse barometer effect).

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### 🧍 **In the Human Body**
If you meant *blood pressure*:
– Naturally low pressure can result from **genetics, dehydration, rest/sleep, altitude adaptation**, or **efficient cardiovascular conditioning** (common in athletes).
– Less natural: dehydration, shock, endocrine issues.

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### 🧭 **Physics Generalization**
Low pressure always means *fewer particles per unit volume*.
Nature achieves that by:
– **Heating (expands)**
– **Rising (reduces overlying weight)**
– **Moving faster apart (divergence)**

Or as thermodynamics puts it: when energy increases or density drops, pressure falls.

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Would you like me to focus on *weather systems*, *human physiology*, or *vacuum/physics* causes next?
What is our atmosphere mostly composed of

Earth’s atmosphere is mostly made of *a few very boring gases doing very interesting things.*

Here’s the mix by **volume** at sea level:

So in short:
**≈99% of Earth’s air is just nitrogen and oxygen**, the rest are trace gases that *make the magic happen*.
how many molecules need to ne rmoved from a system to make it low pressure?

Excellent question — and a sneaky one, because the answer is **“it depends on how much lower you want the pressure to go.”**
Let’s unpack that precisely but quickly.

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### 🧪 The Core Relationship
Pressure comes from molecules bouncing off surfaces.
The relationship is given by:

[
P = frac{N k T}{V}
]

where
– (P) = pressure,
– (N) = number of molecules,
– (k) = Boltzmann’s constant,
– (T) = temperature (Kelvin),
– (V) = volume.

If **temperature and volume stay constant**, pressure is *directly proportional* to the number of molecules:

[
frac{P_2}{P_1} = frac{N_2}{N_1}
]

—

### 🌬 Example: Cutting Pressure in Half
Let’s say you start with air at **1 atmosphere** (101,325 Pa).

To make it **0.5 atm**, you need to remove **half the molecules**.

[
N_2 = 0.5 N_1
]

So, remove **50%** of the gas.

—

So:
– To *halve* pressure, lose half your molecules.
– To get a **good vacuum**, you must remove **over 99.9999%**.
Nature rarely goes that far; even a gentle rise of warm air can lower pressure just a few percent.

—

Would you like me to show a concrete example (like “in a 1 m³ box of air, how many molecules would that be”)? It’s a fun number—spoiler: it’s absurdly huge.
This i snot have helicopters fly though. They create low pressure by movving it out of the waqy, right?

Exactly — you’ve got the right intuition.

A **helicopter** doesn’t remove air molecules from the system like a vacuum pump — it *moves* them. The “low pressure” under a rotor blade is **dynamic**, not missing air, just **redirected air**.

Let’s break it down cleanly:

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### 🚁 **How a Helicopter Creates Lift**

1. **Rotor blades act like spinning wings.**
Each blade is shaped like an airfoil — curved on top, flatter underneath.

2. **As the blades spin**, they slice through the air, deflecting it **downward** (that’s the “downwash”).

3. **Bernoulli & Newton team up:**
– **Bernoulli’s principle:** Faster air over the curved top = lower pressure above.
– **Newton’s third law:** Air pushed downward = equal and opposite force pushing the blade upward.

4. The result: **higher pressure below, lower pressure above** the rotor = lift.

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### 🧠 **So what’s really happening?**
– The air isn’t being “sucked away.”
– It’s **accelerated**—the blade *forces* air downward, which creates a *region of reduced pressure* above the blade’s surface relative to below.
– This differential is enough to lift thousands of pounds, even though the actual pressure difference is only a few percent of ambient air pressure.

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### 📉 Example Numbers
At hover:
– Top of blade: ~0.95 atm
– Bottom of blade: ~1.05 atm
That 0.1 atm (≈10%) difference across the rotor disc is plenty to hold the whole chopper up.

—

So yes — you’re right:
**Helicopters fly by moving the air out of the way, not by removing it.**
They make a *temporary pressure imbalance* — a dynamic, flowing low pressure — not a vacuum pocket.