Which is the world's largest permanent scale model of the Solar System?

The Sweden Solar System is the world's largest permanent scale model of the Solar System. It is in the scale of 1:20 million and stretches 950 km across the country. The bodies represented include the Sun, the planets (and some of their moons), dwarf planets and other small bodies (comets, asteroids, trans-Neptunians, etc.). The Sun is represented by the Avicii Arena in Stockholm, the largest hemispherical building in the world. The planets, all appropriately scaled, are all around Stockholm and its suburbs.

So far, all eight official planets and dwarf-planet Pluto are in place, at distances from 2.9 km (Mercury) to 300 km (Pluto) from the Globe Northwards. Not limiting themselves to metallic spheres, Jupiter is presently a flower arrangement on a roundabout island outside Arlanda airport; Neptune is an acrylic sphere that shines with the planet’s iconic blue light at night. Comets like Halley and Swift-Tuttle have also been introduced to the system, though South-West of the Globe; foundations have been built for a representation of Termination Shock, the edge of the heliosphere, at the Institute of Space Physics in Kiruna, some 950 km North of the Globe, above the Arctic Circle.

Of course, most tourists do not have the time to fling up and down the coast of the Baltic Sea looking for a lot of small, round things, so it is fortunate that most of this Solar System can be found close to Stockholm.

Picture Credit : Google

Which is the hottest planet?

The farther you get away from the Sun, the cooler you get. So let’s take a look at those planets that sit between Earth and the Sun: Mercury and Venus.

Since Mercury sits closest to the Sun, it must be the hottest planet. Right? That only makes sense, doesn’t it? After all, Mercury receives more sunlight per square foot than any other planet in the solar system. Wrong! Venus is actually the hottest planet in the solar system.

On a hot day on Mercury, the temperature can rise to over 700 ºF. That’s hot! You’d definitely need plenty of sunscreen there. A hot day on Venus, however, is even hotter. How much so? The highest temperatures on Venus exceed 900 ºF. Yikes! Now that’s a scorcher, for sure.

Most friends are probably wondering why Venus is hotter than Mercury. After all, it’s farther away from the Sun. The answer lies in the atmosphere. 

Mercury is small and sits closest to the Sun. It also moves very quickly around the Sun. For these reasons, it doesn’t have an atmosphere. When the Sun’s rays hit Mercury, they just bounce off into space. There’s nothing to reflect them back toward the planet and retain their heat.

Venus, on the other hand, has a very thick atmosphere. Its atmosphere is actually over 90 times denser than Earth’s atmosphere. It’s also made up mostly of carbon dioxide, a greenhouse gas. Venus’s atmosphere acts like a one-way door. It lets in solar radiation, but it doesn’t let it back out.

This creates oven-like conditions on the surface of Venus. Because of this intense heat, no water can be found there. Moreover, carbon dioxide is a noxious gas. It creates raging winds that blow constantly across the surface of the planet. This gives it one of the harshest environments you’re likely to find in the entire solar system. Earth and Venus are sometimes called “sister” planets because of their similar sizes. But in most other ways, they couldn’t be more different.

Before scientists could see Venus with the help of unmanned probes and space telescopes, many of them thought Venus was a lush, tropical paradise. The truth is that it’s a barren rock that looks like Earth’s Moon. Its clouds appear yellowish because of the presence of sulfur dioxide alongside the huge amounts of carbon dioxide.

Credit : Wonderopolis 

Picture Credit : Google

Which is the only planet where day longer than year?

Just to be clear, this answer to ‘which planet has the longest day’ is based on this criteria: a planets day is how long it takes it to complete one rotation on its axis. This is also referred to as its rotational period. So, Venus has the longest day of any planet in our solar system. It completes one rotation every 243 Earth days. Its day lasts longer than its orbit. It orbits the Sun every 224.65 Earth days, so a day is nearly 20 Earth days longer than its year.

Now, back to why the Venusian day is longer than its year. Venus is closer to the Sun; therefore, its orbit takes a shorter period of time than its rotation upon its axis. The planet also rotates in retrograde. That means it spins in the opposite direction of the Earth. If you were standing on Venus, you could see the Sun rise in the West and set in the East.

A manned Venus flyby mission was proposed in the late 1960s. The mission was planned to launch in late October or early November 1973, and would have used a Saturn V rocket to send three men. The flight would have lasted approximately one year. The spacecraft would have passed approximately 5,000 km from the surface about four months into the flight. There have been several unmanned probes and flybys of the planet, including MESSENGER and the Venus Express. Future proposed missions include the BepiColombo, Venus InSitu Explorer, and the Venera-D.

Credit : Universe Today 

Picture Credit : Google

What is it called when the Earth orbits the Sun?

Imagine a line passing through the center of Earth that goes through both the North Pole and the South Pole. This imaginary line is called an axis. Earth spins around its axis, just as a top spins around its spindle. This spinning movement is called Earth’s rotation. At the same time that the Earth spins on its axis, it also orbits, or revolves around the Sun. This movement is called revolution. A pendulum set in motion will not change its motion, and so the direction of its swinging should not change. However, Foucault observed that his pendulum did seem to change direction. Since he knew that the pendulum could not change its motion, he concluded that the Earth, underneath the pendulum was moving. An observer in space will see that Earth requires 23 hours, 56 minutes, and 4 seconds to make one complete rotation on its axis. But because Earth moves around the Sun at the same time that it is rotating, the planet must turn just a little bit more to reach the same place relative to the Sun. Hence the length of a day on Earth is actually 24 hours. At the equator, the Earth rotates at a speed of about 1,700 km per hour, but at the poles the movement speed is nearly nothing.

For Earth to make one complete revolution around the Sun takes 365.24 days. This amount of time is the definition of one year. The gravitational pull of the Sun keeps Earth and the other planets in orbit around the star. Like the other planets, Earth’s orbital path is an ellipse so the planet is sometimes farther away from the Sun than at other times. The closest Earth gets to the Sun each year is at perihelion (147 million km) on about January 3rd and the furthest is at aphelion (152 million km) on July 4th. Earth’s elliptical orbit has nothing to do with Earth’s seasons. During one revolution around the Sun, Earth travels at an average distance of about 150 million km. Earth revolves around the Sun at an average speed of about 27 km (17 mi) per second, but the speed is not constant. The planet moves slower when it is at aphelion and faster when it is at perihelion. The reason the Earth (or any planet) has seasons is that Earth is tilted 23 1/2oon its axis. During the Northern Hemisphere summer the North Pole points toward the Sun, and in the Northern Hemisphere winter the North Pole is tilted away from the Sun.

Credit : Lumen Learning 

Picture Credit : Google

Which planets have no moons?

Of the terrestrial (rocky) planets of the inner solar system, neither Mercury nor Venus have any moons at all, Earth has one and Mars has its two small moons. In the outer solar system, the gas giants Jupiter and Saturn and the ice giants Uranus and Neptune have dozens of moons. 

Jupiter's menagerie of moons includes the largest in the solar system (Ganymede), an ocean moon (Europa) and a volcanic moon (Io). Many of Jupiter's outer moons have highly elliptical orbits and orbit backwards (opposite to the spin of the planet). Saturn, Uranus and Neptune also have some irregular moons, which orbit far from their respective planets.

Saturn has two ocean moons – Enceladus and Titan. Both have subsurface oceans and Titan also has surface seas of lakes of ethane and methane. The chunks of ice and rock in Saturn's rings (and the particles in the rings of the other outer planets) are not considered moons, yet embedded in Saturn's rings are distinct moons or moonlets. These shepherd moons help keep the rings in line. Titan, the second largest in the solar system, is the only moon with a thick atmosphere.

In the realm of the ice giants, Uranus's inner moons appear to be about half water ice and half rock. Miranda is the most unusual; its chopped-up appearance shows the scars of impacts of large rocky bodies.

Neptune's moon Triton is as big as Pluto and orbits backwards compared with Neptune's direction of rotation.

Credit : NASA Science

Picture Credit : Google