At first glance, this seems like a simple, straightforward question. Straightforward and simple, usually meaning there is much more to the question than meets the eye. Seriously, this is an excellent question and one that deserves a serious answer. From scientific to philosophic, it’s all how you look at the question.
So, how far can you see from a plane?
Here is the theoretical distance you can see from a plane at different altitudes, given perfect weather conditions:
- at 1000 feet: 38.7 Miles (62km)
- at 5,000 feet: 86.6 Miles (140 km)
- at 10,000 feet: 122.5 Miles (195 km)
- at 20,000 feet: 173.3 Miles (277 km)
- at 30,000 feet: 211.3 miles (340 km)
- at 39,000 feet: 235 miles (391 km)
The technical answer is all well and good, but there are other things involved that could change that answer. That actual distance you can see can be affected by weather conditions, time of day, even the direction you look. Taking these things into consideration makes this more of a bar bet question than a scientific exercise.
How to Calculate How Far You Can See From a Plane
Well, the answer is quite short. In order to calculate how far you can see at any given height, you use any of the following formulas, depending on if you’re using the metric or imperial system.
Metric System
d≈3.6√h where
- d = distance in kilometers you can see
- h = height in feet above sea level
Imperial System
d≈1.22√h where
- d = distance in miles you can see
- h = height in feet above sea level
Here is a nice calculator that does the calculation for you!
Factors Determining How Far You Can See From a Plane
The straightforward mathematical answer uses trigonometry. The equation calculates the distance from the observer to the point on the circumference of the earth the furthest away that can be seen, the horizon.
To get a slightly more elaborate answer that takes more aspects into account, we must describe the different conditions.
There are other ways to look at the question and other considerations to be taken. Before we get deeper into the discussion, let’s look at some of the more obvious physical factors that can be involved.
Here are the most prominent ones:
- In which direction are you looking?
- What are you looking at?
- What are the weather and atmospheric conditions at the time of the observation?
- Is it dark or light?
Let’s now look closer at these factors.
1. Is the Earth Really a True Sphere?
The formula used above to calculate the distance you can see the horizon from some height above sea level assumes a spherical earth. The truth is the earth is not a true sphere. As the earth spins, it bulges around the equator, but it doesn’t even bulge evenly. The masses of the continents are spread unevenly around the surface, causing even more distortions in the shape of the earth as it rotates.
The effect of this means that how far the horizon is from your eye is also a function of which direction you look.
- Looking east or west makes the horizon a bit further away.
- Looking north or south puts the horizon just a small amount closer to your eye.
Our mathematical model also assumes that the earth is a smooth sphere with no distortions on the surface.
- The earth’s surface is anything but smooth and regular. Mountains and valleys make the earth’s surface rough and uneven.
- Even the surface of the oceans is not consistent. Tidal forces create bulges on the surface of the ocean, depending on where the moon is in relation to the earth.
Anything tall can affect the distance you can see when flying at altitude in a plane. For example, a 10,000-foot-tall mountain many miles over the horizon may still be visible above the edge of the horizon when viewed from 30,000 feet.
This can effectively add hundreds of miles to the distance you can see.
2. Light Can Bend (Refraction)!
Light doesn’t always travel in a straight line for one point to another, especially at great distances. Atmospheric conditions can reduce or enhance the distance one can see. A curious phenomenon that occurs in the atmosphere that surrounds the planet is called refraction.
The refraction of light in the atmosphere is caused when:
- a dense layer of colder air forms above a warmer mass of air. This usually happens over oceans where warm currents of water keep surface temperatures elevated.
- light passing from the warmer layers of air into the colder layers of air and then out again is bent slightly. This is called atmospheric refraction and adds distance to the path of the light reaching your eye.
This bending of light can cause light to seem to bend or curve over the horizon line, making it possible to see slightly further than the horizon, especially if looking at tall objects that appear over the horizon line. The overall effect is to make the taller object appear just a bit further away because the light is traveling further to get to your eye.
3. Atmospheric Conditions
Other atmospheric effects can certainly prevent you from seeing very far. If the plane happens to be flying through or over clouds, the distance you can see maybe nearly zero. Flying above clouds makes calculating the distance you can see more difficult.
In remembering our earlier calculation, there appeared a constant, 1.22 (3,6 in the metric system). That constant is mathematically derived using an approximation of the radius of the earth. You must rethink the entire equation to compensate for the altitude of the clouds.
Without going into a lot of in-depth trigonometry, let me say that the distance you can see is shortened because you are effectively closer to the top layer of clouds.
Other things in the air can also reduce the effective distance you can see.
- Natural phenomena such as dust storms
- High humidity
- Man-made pollutants
These are all capable of reducing over distance and must be considered when judging the distance you can see from the airplane.
3. Impact of Darkness and Light ( A little off-topic…)
Flying at night offers an entirely different view of the world below. I think most people would argue that after dark, the distance you can see from an airplane is considerably reduced. The answer for me comes from looking at things from a different perspective.
At night, a completely different opportunity presents itself. Consider not looking down but looking up. Sitting in that airplane cruising through the atmosphere at 30,000 feet, you have a unique opportunity that most people never think about.
The greatest hindrance to observing space from the earth is the thick blanket of atmosphere that surrounds us. Astronomers go to great lengths to mitigate the effects of the atmosphere on their telescopes by locating themselves at extreme altitudes on mountaintops.
In that airplane, you are 30,000 feet high. Much higher than the most remote observatory built on the ground.
Look up!
The atmosphere is much thinner and you will be surprised at what you can see.
Consider this:
At night, flying at 30,000 feet, the Andromeda galaxy is easily visible.
- The Andromeda galaxy is more than 2.5 million lightyears from earth.
- One light-year is 5,879,000,000,000,000 miles.
- 2.5 million light-years multiplied by 5.879e+12 miles per light-year equals 1.5e+19.
- 150,000,000,000,000,000,000 miles
That’s a long way. I guess, in a way, you can say that you are able to see that far at night flying in that airplane.
Final Notes
So, the answer to the question, “How far can you see from an airplane.” is not always what meets the eye. Scientifically and mathematically, that distance can vary a lot because of many different factors.
Environmental conditions, geological factors, and the time of the observation all make a difference in how far you can see from that plane in which you are riding. Your philosophical perspective can also provide an entirely different sort of answer by just looking away from earth and toward the heavens.
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