In the standard model, yes, exactly. Aviation describes a non-standard day as ISA + ΔT: the whole column shifted by the same number of degrees, so a day 20 °C hot at the ground is 20 °C hot at the tropopause too. The temperature lines on the left run parallel by construction.
What does converge is density. Warm air near the ground is thinner, but a warm column is also taller, so it holds more air higher up. The two effects cancel at around 8 to 9 km, the height meteorologists call the isopycnic level: above it, the warm day is denser than standard. Pressure does the opposite of converging: the warm column's pressure pulls further ahead the higher you go.
The real atmosphere adds one thing the model leaves out. The day-to-night swing in temperature happens because the ground heats and cools, and it is felt mainly in the lowest one to two kilometres, the boundary layer. Above that, a sunny afternoon and the night before differ by only a degree or two. So the daily swing does fade with height, as you might expect; differences between seasons and air masses do not, and that is what ISA + ΔT describes.
The International Standard Atmosphere, all seven layers of ISO 2533 to 84,852 m. Pressure halves by about 5,500 m and keeps falling.
Water is about 800 times denser than air and nearly incompressible: one more atmosphere every ~10 m (seawater, about 1,025 kg/m³), all the way down.
Always 20.9% of the air. What altitude removes is total pressure, so each lungful holds fewer molecules of everything.
Clausius–Clapeyron anchored at 100°C and 1 atm. Less pressure, an earlier and cooler boil; more, a later and hotter one, until the critical point.
The model predicts about 31% of sea-level oxygen, close to the measured value of roughly a third. The real summit runs a little higher than the standard atmosphere predicts, thanks to a persistent high-pressure pattern over the Himalayas: part of why the mountain is climbable without bottled oxygen.
Enough to put roughly 11,000 tonnes-force on a single square metre. F = ΔP × A, the same relation a hydraulic press or a dam wall uses: multiply a pressure by a porthole, a window or an eardrum and the real physical danger, or design requirement, becomes vivid.
Air thins on a curve, so pressure falls fastest near the ground and levels off higher up. Ocean pressure climbs in a straight line, almost exactly one more atmosphere every 10 m to the seafloor.
The air is 20.9% oxygen from sea level to the edge of space. That is why supplemental oxygen at altitude works by adding pressure, not purity.
At Base Camp a 1.5 kW kettle reaches “boiling” in about 3.1 minutes rather than the sea-level 3.95: there is less temperature to climb to. The egg cooks at whatever temperature the water actually holds, so a cooler boil is a less effective cooking bath. Same falling boiling point, opposite consequence, depending on whether “reaching boiling” or “using boiling” matters.
Here pressure drops to the vapour pressure of water at body temperature (37°C). Above it, without a pressure suit, bodily fluids would begin to boil at body heat alone: a hard ceiling for unprotected exposure, well below the edge of space at 100 km.
Beyond about 22.06 MPa (roughly 2,185 m of water) liquid and gas stop being different things, and there is no boiling point left to reach. The tool flags it as supercritical.
It doesn't run out in percentage — oxygen stays about 20.9% of the atmosphere all the way up. What drops is the total pressure, so each lungful contains far fewer molecules overall, oxygen included. That's why supplemental oxygen at altitude is delivered at higher pressure, not higher purity alone.
Boiling happens when a liquid's vapour pressure matches the surrounding pressure. Squeeze the surrounding pressure higher (as water depth does) and the liquid has to get hotter before it can boil — the same principle a pressure cooker uses. Push far enough (beyond about 2,185 m depth, 22.06 MPa) and water crosses its critical point: the distinction between liquid and gas disappears entirely, and there's no boiling point left to reach.
Around 19,000 m, pressure drops so low that it matches the vapour pressure of water at normal body temperature (37°C). Above that altitude, without a pressure suit, bodily fluids would begin to boil at body heat alone — a hard physiological ceiling for unprotected human exposure, well below the internationally recognised edge of space at 100 km.
Pressure alone doesn't feel intuitive — force does. The same 1,086-atmosphere pressure at the Challenger Deep becomes a very different, very physical number once you multiply it by a porthole, a window, or an eardrum: F = ΔP × A, the same relationship a hydraulic press or a dam wall uses.
Boiling just means bubbling, not a fixed temperature — at altitude, water boils at a genuinely lower temperature, so a "rolling boil" on a mountain is actually cooler than a gentle simmer at sea level. The egg cooks at whatever temperature the water actually reaches, not at a fixed 100°C most recipes assume.
They're opposite sides of the same fact. The kettle only has to climb from tap temperature to whatever the local boiling point is — a lower boiling point is simply a shorter climb, so it finishes sooner. The egg, though, cooks at whatever temperature the water actually holds once it's boiling — a cooler boil is a less effective cooking bath, so it takes longer to reach the same doneness. Same falling boiling point, opposite consequence, depending on whether "reaching boiling" or "using boiling" is the part that matters.
Yes — the column is a direct input, not just a display. Click anywhere on it to jump straight there, or press and drag to scrub continuously from the ocean floor to the stratosphere and watch every number update live.
Releases in which this page changed, newest last. Derived from the archived copy of every release, not from notes written afterwards — so it reflects what actually shipped. Site-wide passes are left out; they are in the full changelog.