Human Perspective: Human height, viewing altitude of  human eyes

We'll discuss here the comparison of altitudes or heights above the Earth's surface with which humans have experience in the contemporary world.  We will mostly stay away from discussing an astronaut's perspectives.  We'll discuss just your average humans riding in elevators, scaling mountains and traveling across countries and between continents. From this comparative discussion we'll then pull this all together to compare the world as we see it dimensionally through human eyes. 

Human eyesight at human height

"According to the U.S. Centers for Disease Control and Prevention (CDC), the average age-adjusted height for American men 20 years and older is is 69.1 inches (175.4 cm), or 5 feet 9 inches tall, and the average height of an American female over 20 years of age is 63.5 inches (161.5 cm), or 5' 3.5" tall."  This data comes from a table compiling height data across the countries of the Earth.  So, let's use the average of these two US values for men and women as an example of the viewing height humans typically experience.  You can look at the table presented [here] to scale to your own age group and nationality.

For this page's discussion, let's let an average human height be:

`"viewing height" = (63.5 "inches" + 69.1 "inches")/2 = 66.3 "inches"` or 

Heights above our level

You can of course climb a ladder to get a higher vantage point.  You can take an elevator to the top of a building. You can fly in an airplane. You can climb a mountain.  We will consider these heights as common human perspectives in the contemporary world.

So, let's compare some of those altitudes also.

Height in a building

The list of tallest buildings is compiled on Wikipedia.  The tallest of those is the Burj Khalifa in Dubai and that building is 2,717 ft (828 m) tall. I have a fear of heights, so I probably won't be experiencing the view from the top of that building anytime soon. 

For a US perspective, the tallest building listed in the US today is the Willis Tower (formerly the Sears Tower) in Chicago.  That structure is 1450 feet (442.1 meters).  The World Trade Center was 1776 feet tall and I stood atop that once.  Remembering that experience, I can't imagine being at the top of the Burj Khalifa.  I get a weird feeling in my chest just thinking about that.

Aircraft flight altitudes

The highest commercial airliner altitude was around 60,000 feet by the Concorde. The highest air-breathing engine airplane was the SR-71 — which set aircraft altitude records you can see at http://www.sr71.us/srrcd~1.htm. The record noted there is: 80,257.86 ft (24,390 meters).  You can imagine they were trying to be as accurate as possible in their recording of that maximum altitude because at the time of that flight they were still "competing" with the USSR for supremacy in all things technological.

By the way, if you want to see an SR71 Blackbird, which was a classified system at the time it was flying, there is one at the Air Force museum at Wright Patterson AFB.  It is truly impressive.

The SR71 had wings so did get lift from its powered flight in the thin atmosphere at those extreme altitudes -- as opposed to a rocket which would usually have fins to stabilize it's upward trajectory but would not rely on wings for lift.

The highest airliner flying today reaches 45,000 feet. The highest business jet flying today reaches 51,000 feet. These approximations came off a news site: ksdk.com, and despite the fact I don't like what is generally reported by "news" agencies, I'll use the values as our aircraft altitude approximations.  

When you fly commercial flights, the pilot sometimes reads off his instrumentation and reports information to the passengers, so next time you are flying ask one of the flight attendants to ask one of the pilots to report when you are at the highest altitude in your planned flight.  That shouldn't be too much trouble for them and you'll probably hear a pilot reporting something in the mid 30,000s feet range.

View from mountaintops

We have a unique perspective on views from mountain tops here in Colorado.  Pike Peak is 14,115 feet and the views to its East from the summit are unobstructed by other mountains so you can see far off toward Kansas in that unbroken and very flat expanse to the East of the Rockies.  The tallest peaks in many mountain ranges are surrounded by lower mountains and those by even lower mountains, so often the view from the highest peaks does not extend to the flatter lands beyond.

As I drive from vising in the Midwest it is always a thrill to see Pikes Peak for the first time on the trip as it comes into view, rising at last above the horizon.  And it grows in majesty as you approach Colorado Springs, coming full into view.

The highest peak in the world, measured as most things in terms of distance above an average sea level, is Mount Everest.  Mount Everest has the "highest altitude." Mount Everest is 8,850 meters (29,035 feet) above sea level.

The atmosphere as the Earth's "peach fuzz"

When people talk about the height of the Earth's atmosphere, they sometime use the analogy of a peach's fuzz to describe the very thin layer that our atmosphere is on this Earth. The density of the atmosphere decreases as you rise above the Earth's surface. The atmosphere continues upward until we get to a height where the atmosphere is so thin that there are very few molecules of what constitutes air per volume of space.  We call this the edge of space.  The approximation of this altitude -- because again there is no absolute cutoff of the atmosphere -- is considered to be about 220 miles.  Call it 225 miles or 207 or whatever.  There is some point, somewhere around 220 miles, where the density of air molecules is so thin that we consider the volume beyond space.  One of the main reasons military aircraft don't fly anywhere near this high is the wings of the aircraft and control surfaces cannot lift and control the aircraft above an altitude where the air becomes sufficiently less dense.  Weather balloons used in data collection and experimentation are often flown and recording data up to around 100,000 feet.

The US Air Force for a rule of thumb uses 62 miles, about 330,000 feet, (100 kilometers) as a discussion point boundary value for aeronautics and astronautics. 

So, the analogy is that our Earth's atmosphere is 220 miles thick, analogous to the fuzz on a peach.  And the Earth's diameter is 6,378 km (3,963 mi) at the equator.  The Earth is, in fact, a slightly squished ball, referred to geometrically as an ellipsoid.