Comments
lilafrika t1_iyf2fpt wrote
Is this how a fly in your car also works? Even though we are moving at 60mph, they can still fly around the car as if it was sitting still because the atmosphere for the is also moving?
Gathorall t1_iyf2y5e wrote
Well, is it windy inside your car when you're driving?
lilafrika t1_iyf35eb wrote
Not if the windows are up/closed.
Jnsjknn t1_iyf3b25 wrote
Yes, but when you're accelerating, the air lags behind slightly and the pressure in the rear of the car is slightly higher than the front.
lilafrika t1_iyf3u55 wrote
I ask because Ive seen insects fly and sometimes hover in place, even though we are barreling down the freeway.
JoyGodLives OP t1_iyf08la wrote
Thank you!
DarkAlman t1_iyf202d wrote
TLDR: no
The short answer is planes can't hover because they need air flowing over their wings to fly. If they were to have zero ground speed they would immediately crash.
To achieve what's called a Geo-synchronous orbit (where the GPS satellites are), meaning that you are hovering directly above a specific spot and stay there, you actually need to go very high into space and speed up a lot to get there and stay there. It has to do with orbital mechanics, and outside the scope of this ELI5.
The long answer is that you have to factor in is momentum.
The reason we have a hard time conceptualizing this is because humans don't feel how fast we are moving, we feel acceleration and deceleration. That's why when a car or a plane gets up to speed you feel the same as if you are standing still. You only feel it when the vehicle is speeding up or slowing down.
You sitting still is actually moving around at around 1000mph because that's the speed the Earth is turning. You are also moving at around 30km per sec because that's how fast the Earth orbits the sun, etc etc
That's why we have to speak in relative terms. You sitting still means you aren't moving relative to the Earth spinning, because everything you are comparing yourself against in terms of movement is also spinning around at 1000mph.
If you were to suddenly remove all the momentum an object has relative to the Earth, the Sun, the Galaxy, etc it would go flying off into space at several thousand meters per second... because everything else would fly away from it in an instant.
If you really want to blow your mind, The Earth is rotating from West to East, so when you move East you are moving the speed you are walking + the rotation of the Earth. But when you are moving West you are moving the speed of the Earths Rotation minus you walking speed. So a person walking due West is moving slower than a person sitting still. It's all relative to how you measure it.
Invisabowl t1_iyf4eel wrote
>The short answer is planes can't hover because they need air flowing over their wings to fly. If they were to have zero ground speed they would immediately crash.
I’m sure you already know this and were just simplifying it to make your point but planes don’t care about ground speed. It’s not super common but planes can hover if they have enough wind. It’s called perching. As you said they require airflow.
Some aircraft have a very low stall airspeed such as STOL aircraft so it doesn’t take more than about 45-50 knots of wind to start perching. In some cases they can even fly backwards lol.
Some other interesting things that happen are the transatlantic commercial flights that end up with a supersonic ground speed because of very high tailwinds in the jet stream, yet if the plane was actually supersonic it would destroy the aircraft.
Again, not bringing this up to detract from your well explained comment. I just really like planes lol.
JoyGodLives OP t1_iyf2ux3 wrote
Wow, that's cool. Thank you! I feel dizzy now. In a good way!
greenvillain t1_iyf4qg2 wrote
Look at non-stop flights from Tokyo to Chicago (I've taken this flight a few times). Note the local departure and arrival times. The plane arrives in Chicago before it leaves Tokyo.
RSwordsman t1_iyf4599 wrote
> If they were to have zero ground speed they would immediately crash.
Just some clarification here you probably mean zero airspeed. If the wind is blowing 70mph and a plane's stall speed is 60, it could very well hover above the ground while the gauge reads 70mph.
RSwordsman t1_iyf1661 wrote
It depends on how you consider "hovering." If you mean zero ground speed, it would rotate with the earth. If you mean zero orbital velocity, the earth would rotate under it but it might have to maintain some crazy airspeed to keep that location in the sky.
JoyGodLives OP t1_iyf1rkp wrote
Oh, that sounds interesting. Just going to find out what orbital velocity means..(don't judge!)
krista t1_iyf2dox wrote
”orbital velocity” is the speed and direction you need to go to continuously fall and always miss the ground.
JoyGodLives OP t1_iyf32lp wrote
Ooh, I much prefer your definition than Wikipedia's. Good one!
krista t1_iyf4rmz wrote
based off the late, great douglas adams.
RSwordsman t1_iyf2ixa wrote
All good, I first internalized the difference for real after playing Kerbal Space Program. It starts off measuring your velocity relative to the surface, where 0 meters per second means you're not moving with respect to the ground. But get high up enough and it measures your speed by how fast you actually go around the planet, not respective of the spin. It makes a huge difference for space travel. *A geostationary satellite is traveling at some orbital velocity but its surface velocity would be zero.
JoyGodLives OP t1_iyf38g1 wrote
Cool!
occationalRedditor t1_iyf5z3e wrote
Aircraft don't hover they fly in circles. Usually an aircraft will fly around in a hold pattern which is two straight legs with semi circles at the end, often centrerd on a navigation beacon on the ground. So in that case it would stay over that location.
If an aircraft flies circles without reference to the ground. Flying the same speed all the time and turning at the same rate all the time, it would move with the airstream rather than the ground. If the wind at the aircraft's high altitude is say 100kts (nautical miles per hour) then it would move in the wind direction at 100kts (115mph, 185 kph) along the ground while appearing to just fly in circles.
If the aircraft left the atmosphere (above 100km, but wings struggle much lower) it wouldn't be using aerodynamics at all and it would have to keep itself up by going a lot faster so it couldn't stay still over a point on the earth until reaching geostationary altitudes at 35,000km amd speeds of 3 km/sec (67,000 mph).
JoyGodLives OP t1_iyf6imu wrote
Interesting, thank you!
druppolo t1_iyf7lkj wrote
Yes and no.
It depends on what the plane speed, what direction you fly and if you are far or close to equator.
But sure, you can fly west and see continents passing below you while you stay always in daylight or night or whatever. You can easily fly as fast as the earth rotation (1000mph at equator, less and less towards the pole where it’s zero) meaning you will see the sun always at the same angle to you while they planet below you revolves.
This happens only if you fly west as you are chasing the sun going west. To land at exactly the same local time you need a very fast plane, maybe supersonic, or take a route in a northern region with a normal jet (works also south but there’s no destinations close to the South Pole to try this trick for cheap). For example Toronto-Vancouver is 5 hours of flight, and only 2 hours in local time. Meaning you lost your race with the sun but slightly, considering those 5 hours include the plane moving in the airport, you probably lost one hour out of four spent in actual flight. Similarly, London-Vancouver is 9:45 hour flight and 1:45 time difference, quite close to see the earth rotate below you while not moving relative to the sun.
You just need to match the earth rotation speed in your area. Which again can be between 1000 and zero mph. Altho standing still in the North Pole is a bit of a cheat.
Jnsjknn t1_iyf01xf wrote
The plane needs the atmosphere to float. The atmosphere rotates with the Earth and so would the plane.