Eternal night would fall over the planet and Earth will start traveling into interstellar space at 18 miles per second. Within 2 seconds, the full moon reflecting the sun's rays on the dark side of the planet would also go dark.
With no sunlight, photosynthesis would stop, but that would only kill some of the plants—there are some larger trees that can survive for decades without it. Within a few days, however, the temperatures would begin to drop, and any humans left on the planet's surface would die soon after.
You might think it would suddenly become very cold. But it wouldn't. You wouldn't even notice the difference. Our planet has stored enough heat in its atmosphere and oceans to keep us warm for those five seconds without the Sun.
The current mean temperature of the Earth's surface is about 300 Kelvin (K). This means in two months the temperature would drop to 150K, and 75K in four months. To compare, the freezing point of water is 273K. So basically it'd get too cold for us humans within just a few weeks.
The gravitational pull of the moon moderates Earth's wobble, keeping the climate stable. That's a boon for life. Without it, we could have enormous climate mood swings over billions of years, with different areas getting extraordinarily hot and then plunging into long ice ages.
In other words, it's extremely unlikely that life on any planet can survive the death of its sun — but new life could spring from the ashes of the old once that sun shrivels up and turns off its violent winds.
Warmth: not too much and not too little
And we get the amount of warmth needed for humans, animals and plants to live. If the sun would go out, no life could survive on most of earth's surface within a few weeks. Water and air would freeze over into sheets of ice.
Earth will interact tidally with the Sun's outer atmosphere, which would decrease Earth's orbital radius. Drag from the chromosphere of the Sun would reduce Earth's orbit. These effects will counterbalance the impact of mass loss by the Sun, and the Sun will likely engulf Earth in about 7.59 billion years.
Stars like our Sun burn for about nine or 10 billion years. So our Sun is about halfway through its life. But don't worry. It still has about 5,000,000,000—five billion—years to go.
Retinal damage could occur in just 30–60 seconds, and sometimes even less, he says. Once the retina is exposed to sunlight damage, the macula's cells are damaged, rendering them unable to properly process visual information, says Habash. This is when you end up with dark spots in the center of your vision.
At the current rate of solar brightening—just over 1% every 100 million years—Earth would suffer this "runaway greenhouse" in 600 million to 700 million years. Earth will suffer some preliminary effects leading up to that, too.
The Sun survives by burning hydrogen atoms into helium atoms in its core. In fact, it burns through 600 million tons of hydrogen every second. And as the Sun's core becomes saturated with this helium, it shrinks, causing nuclear fusion reactions to speed up - which means that the Sun spits out more energy.
Within a week, the average global surface temperature would drop below 0°F. In a year, it would dip to –100°. The top layers of the oceans would freeze over, but in an apocalyptic irony, that ice would insulate the deep water below and prevent the oceans from freezing solid for hundreds of thousands of years.
But what of the average temperature of space away from the Earth? Believe it or not, astronomers actually know this value quite well: an extreme -270.42 degrees (2.73 degrees above absolute zero).
Suddenly, without the moon, our days would last between 6 and 12 hours, rather than the 24 hours we experience now. If our days became this short, then we would have significantly more days in our calendar year. Instead of 365 days in a year, we would have over a thousand.
Although you might think it would be cool, humans could not live on the moon! (Maybe one day in the future…) The moon has almost no atmosphere, so there's no air for us to breathe. There is no water on the moon either, and we need to drink water to survive.
The scientific consensus is that there is a relatively low risk of near-term human extinction due to natural causes. The likelihood of human extinction through humankind's own activities, however, is a current area of research and debate.
To conclude, any new human colonisation on another planet would be very difficult. The extreme weather conditions, the chemistry of the atmosphere and the vast amounts of resources needed to support human life all play into this.
Because the Sun continues to 'burn' hydrogen into helium in its core, the core slowly collapses and heats up, causing the outer layers of the Sun to grow larger. This has been going on since soon after the Sun was formed 4.5 billion years ago.
If Earth had two moons, it would be catastrophic. An extra moon would lead to larger tides and wipe out major cities like New York and Singapore. The extra pull of the moons would also slow down the Earth's rotation, causing the day to get longer.
During the summer in the Northern Hemisphere and the winter in the Southern Hemisphere, the rings would cast their shadows on the Southern Hemisphere, and vice versa. This could mean that winters in both hemispheres might be colder and more severe than they are on our Earth.
The Earth formed over 4.6 billion years ago out of a mixture of dust and gas around the young sun. It grew larger thanks to countless collisions between dust particles, asteroids, and other growing planets, including one last giant impact that threw enough rock, gas, and dust into space to form the moon.