What makes the Earth suitable for life?
Life is vulnerable. Too much heat and harmful radiation, or too little water or energy, and our planet’s vibrant biosphere would vanish. Earth is our spaceship, protecting us from the harsh conditions in empty space.
No one knows exactly how life began. But we do know how tricky it must have been to sustain. Everything has to be just right: the amount of light and heat from the Sun; the availability of liquid water; protection from ultraviolet radiation and energetic particles; a relatively stable climate; the right chemical and energy balance; and so on. There have been times in the geological past when the Earth was on the verge of turning into a permanently frozen snowball or a superheated furnace, but so far our home planet has remained habitable.
Without the Sun, or the oceans, or the Earth's magnetic field, life would not be possible. We're lucky to live on a hospitable planet.