Nothing special.
Its called the catastrophic alignment or planetary alignment
Yes. If it is not straight, then it is not a line.
No. Almost never happens. Depends on how well aligned you mean, occasionally all the planets will be within 45° (as seen from the Sun) or within a cone that has the vertex at the Sun and has an opening of 30°, this happens every decade or so. All the planets can never align less than 2° because the deviation from the ecliptic for some of the planets is greater than this.
If it is not straight, then it is not a line.
it just a straight line
Inertia is the tendency of objects to keep moving in a straight line. They "want" to go in a straight line, so to speak. However that is changed when a force acts on them. In the case of planets, that force is the gravitational force between the planet and the Sun.So that's why planets orbit the Sun instead of traveling in a straight line.
Straight line through 3 planets such as Sun, Earth and Moon
It wouldn't, but if it were to suddenly cease, the planets would carry on through space at the same speed, but in a straight line away from the sun instead of on a elliptical path.
Newton
The force of gravity.
They never did. In all the solar systems history, all 8 planets never alighned in a straight line
Kepler's Law: "The orbits of the planets are ellipses with the Sun at one of the foci."
It's not that there is some force keeping the planets from falling into the sun; the sun's gravity prevents the planets from travelling in a straight line out of the solar system. If you throw a ball in a straight line then it keeps going, but if you throw a ball on a rope tied to a pole then the rope pulls the ball toward the pole and keeps the ball moving in a circle.
The natural motion of the planets is motion in a straight line. They are prevented from straight line motion by the gravitational force of the Sun.
The sun moves in straight line and the planets move around it in spiral way
Its called the catastrophic alignment or planetary alignment
Gravity is what keeps the planets going in their orbits. If gravity just stopped, then the planets would go flying in a straight line tangent to their orbit.