1. Why in all the pictures presented by NASA and other spatial agencies the Earth is perfectly round but in geography books the Earth is an oblate spheroid? I have personally watch Apollo mission on the moon from NASA website and even in the video presented the Earth looks perfectly round and about the size of the moon, should'n be about 4 times bigger than the moon? Also I've watch another video presented by NASA from Hubble Telescope and in the video is showing the moon crossing the face of the Earth, but the question here is why when viewed from the moon(384,400 km) the earth has moon's size but when viewed from Hubble (a million miles away) the Earth is bigger and of course perfectly round?
Firstly, it isn't.
The equatorial radius (half the "width" of Earth) is roughly 6378.1 km.
The polar radius (half the "height" of Earth), is roughly 6356.8 km.
That means Earth's "width" is roughly 100.34% of its height.
This is a very small difference, so without actually measuring, it will look round.
This image shows just how close it is to a perfect circle:
https://upload.wikimedia.org/wikipedia/commons/f/f9/Earth_oblateness_to_scale.svgHow does this compare to actual pictures?
Well take this one on wikipedia from Apollo 17
https://upload.wikimedia.org/wikipedia/commons/9/97/The_Earth_seen_from_Apollo_17.jpgAgain, hard to tell, but fortunately there is an objective measurement, the number of pixels (however it can vary depending on the camera lens. It is not always equal in x and y).
So in this picture, the width of Earth is 2676 pixels (although it is a bit blurry at the edge).
The height is 2690 pixels.
So while it looks like a sphere (or circle), it actually isn't, however, as I said, the edge is blurry so there is some significant error here.
This is mainly due to not having all of Earth illuminated by the sun.
Using more modern pictures, like those of EPIC, such as this one (this one is in L1 so basically all of Earth that it can see is illuminated):
https://epic.gsfc.nasa.gov/archive/natural/2017/05/30/png/epic_1b_20170530000830_02.pngyou get a width of 1642 pixels and a height of 1638 pixels.
That makes the width 100.24% of the height.(each pixel gives around 0.05%.
Also, I'm pretty sure you didn't see it from Hubble. You likely saw it from EPIC (on DSCOVR).
This all depends on the distance, and they aren't all the same size.
All you can compare is the relative apparent size.
For Apollo, they were on the moon. This makes the moon appear very big.
Meanwhile, Earth was roughly 400 000 km away. This makes Earth appear quite small, however it would appear larger than the moon would appear from Earth.
For EPIC, that is in L1, 1.5 million km from Earth.
The moon is thus roughly 1.1 million km from EPIC.
As they are now both quite some distance away, they will appear closer to the relative sizes, however the moon will still be slightly larger than the simple ratio.
If you view it on the far side, the moon will be slightly smaller.
2. According to science the Earth spins on its axis at a speed of about 1,600 km/h=444.44 km/s ( sound's speed about 343 km/h ). Earth rotates eastward, in prograde motion ( according to Google). So if I take a plane from Madrid to Paris, from west to east, the flight will be about 2h 15min, the distance between Madrid and Paris is 1,270.2 km, that means Paris, from the moment my airplane takes off is moving away from that spot at a speed of 444.44 km/s, but my plane is flies at about 258.33 m/s, is the actual speed of an airplane 258.33 m/s + 444.44 m/s)? According to Google an aircraft cruise at about (740 – 930 kph) so the maximum speed would be 258.33 m/s. Now if I take the plane from Paris to Madrid, from east to west, the flight time would be 2 h 15min, so Madrid every second is coming closer with 444.44 m/s and I fly towards Madrid with 258.33 m/s. Why the same flight time?
The plane is flying through the air. Moving through the air will result in drag. This will attempt to have the plane become stationary with respect to the air.
The engines provide thrust and combat this drag.
The maximum speed of the plane is thus a speed relative to the air.
As the air (for the most part) is moving with Earth, that means the trip will take roughly the same time in each direction.
However, note that this is not always the case.
There are various Jet-streams around the world.
One is one which blows east from Perth to Sydney.
The plane still flies with a speed relative to the air, however now the air is moving relative to Earth.
This results in trips from Perth to Sydney taking much less time (roughly 4 hour 10 minutes), than the trips from Sydney to Perth (roughly 5 hours and 5 minutes).
This is akin to trying to swim in a current.
3. '' To make one complete rotation in 24 hours, a point near the equator of the Earth must move at close to 1000 miles per hour (1600 km/hr). The speed gets less as you move north, but it's still a good clip throughout the United States. Because gravity holds us tight to the surface of our planet, we move with the Earth and don't notice its rotation in everyday life.'' Source: https://astrosociety.org/edu/publications/tnl/71/howfast.html.
What I understand from here is that if I place two cities, A in the North and B at equator on the imaginary latitude the city in the north A will move slower comparing with the city B at equator? How is this possible? City A moving slower means city B will be much ahead? If the speed is decreasing does it mean that at the poles the speed is 0? When I look at a bicycle's wheel the center of the wheel appears to move faster than the tire. I think I've lost it here!
The rotational speed remains the same.
But the linear speed does not.
To try this yourself, spin a bike wheel slowly so you can clearly observe its motion. Perhaps put some tape on it (radially) so you can watch it better rather than having a bunch of spokes).
It is a simple consequence of the constant angular speed and circumference.
If the wheel turns once in a day, that means the centre basically just spins, while the rim will have to move the entire length of the circumference of the wheel.
You can also try this with a friend. Have a friend walk in a small circle and you walk around outside them. You will need to walk much faster to keep up.
This is also why in races (at the Olympics for example), if you are confined to lanes and there is a curve, the people on the inside track start back further to make it so they travel the same distance.
4. The Earth is surrounded by an immense vacuum and other stars, planets etc. Our planet is surrounded by atmosphere (air, gas) and gases are expandable which means they will fill any available space. We also see the smoke from furnace going up, so the smoke goes against gravity. My question is why the vacuum stopped absorbing us? Are we loosing air?
It is somewhat the other way around.
Smoke isn't rising against gravity.
The denser air around it is being pulled down to gravity and displacing the lighter air in the process, just like when you fall you displace the less dense air or if you drop a steel ball in water, it displaces the less dense water.
As for why the gas doesn't escape, this is due to what causes the air pressure in the first place and how vacuums work.
Vacuums don't actually suck at all.
Instead it is the air pressure which pushes things into the vacuum.
The gas would happily act as a bunch of particles flying through space, and that is what they do in space, or close to it.
However, when near a planet (such as Earth), the gravity of the planet pulls them down.
If you just had a little bit of gas, it would just bounce of the planet and keep flying following parabolic arcs.
That is similar to what the gas quite high up does.
But instead of bouncing off Earth, it hits other gas below it and the other gas below it supports its weight.
Thus the gas below it has its parabola cut short and starts falling not only with its momentum but also that transferred from the gas above it.
This gas also hits more gas below. This gas below is holding up not only this layer of gas, but all that above it.
This process continues until you get to Earth where finally the surface of Earth (or whatever is in the way) is holding up all the gas above it.
In each layer you have a balance of forces.
You have gravity pulling the gas down. You have the gas above it weighing down on it forcing it down and you have the pressure below forcing it up.
In each layer, these forces are balanced to produce no net force.
So effectively, gravity is holding the atmosphere to the surface of Earth.