What is the size of our Earth as compared to the Sun? Try and imagine that you are able to shrink the Sun into the size of a football. At this point, the Earth would be reduced to the size of a small seed. That’s how small our earth is as compared to the Sun.
But what would happen if our star, Sun was not the biggest thing in our solar system? Would our Earth and other planets still orbit the Sun? Would earth continue to rotate around the Sun or would Sun rotate around the Earth? How would it affect our neighboring planets?
If you put our star, Sun next to supergiant star and you would not be able to spot our Sun. But compared to the Earth, the Sun is huge.
To fill up the volume of the Sun, it would take the equivalent of 1.3 million Earths. Sun makes up for over 99% of the total mass of our entire solar system, that’s how huge it is. It only looks small to our naked eyes just because it is 150 million kilometers away from Earth.
Let’s see what would happen if the Sun was smaller as compared to the Earth. Surely, our solar system would look completely different.
Earth would be inhabitable and the Sun would no longer be a star. In the cosmos, distance matters and so does the size.
Earth falls under the habitable zone around the Sun. Earth is close enough to the Sun that it doesn’t freeze like Mars, nor is it far away that it doesn’t get scorched like Venus.
This means that the size of the Sun, the size of our planet and the distance between Sun and Earth, is what has made it possible for life to evolve here on Earth. What would actually happen if the Sun was smaller than Earth?
Mass of the star determines its color and temperature. Smaller stars are cooler and redder, while bigger stars are hotter and bluer. Our Sun is a white star – not as small as a red dwarf star and not as big as a supergiant.
One might think that if we make the size of Sun a bit smaller, it would just become a red dwarf with the smaller habitable zone. But reality would be far from it. By the definition of a star, it is a star only if there is a thermonuclear fusion in its core.
You might ask, how small can the stars get? The smallest star we ever came across is the one with a mass of ten earths. This is very close to the theoretical size required for a star to sustain the fusion reaction. If it is smaller than this, then it would not be a star anymore, but rather a cold and dark stellar remnant.
In any possible hypothesis, if the Sun shrank smaller than the size of Earth, this Sun would not have the mass to create fusion reaction and would quickly burn out completely. The solar system would no longer have a star.
Sun if the only source of gravity in our solar system that keeps all planets in orbit. Otherwise, planets would just float away into space till they find other stars.
So, simply said, there is no case that would bring a happy ending for life on earth.
Let’s try out a different approach. Let’s keep the size of the Sun the same and make the Earth bigger than the Sun.
This would make Earth’s mass to be at least 330,000 times bigger than it is now. Just imagine the gravity of the Earth with such mass. Our body would not even able to handle the gravitational pull of this giant Earth. It would easily be able to keep us on the ground and even crush our bones.
The planet with so much mass and gravity would no longer be a planet. It would have enough heat and pressure to become a star itself.
There would be no life left on this hot star. Our solar system would not have one sun but two suns. It would become a binary star system with two stars, Sun and Earth, orbiting around earth other, and other planets circling them both.
In both cases, life on Earth would not survive. But it could make it possible for life to evolve on other planets or even our moon.