When the Sun exhausts its store of nuclear fuel, some 5 billion years from now, it will evolve into a bloated red giant, gobbling up Mercury and Venus, and scorching the Earth. After ejecting its outer layers in the form of a colourful planetary nebula, the Sun will then be compressed into a tiny white dwarf star.
As per space agencies and researchers, the Earth will no longer be a habitable planet if the Sun dies, since it is the source of all life. All the plants and food grain will die, leading to the death of animals who rely on plants for food, eventually disrupting the entire food chain.
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.
Our Sun is doomed. Billions of years from now, the Sun will deplete its hydrogen fuel and swell to a red giant before becoming a white dwarf. It's a well-known story, and one astronomer has understood it for decades. Now, thanks to the latest data from Gaia, we know the Sun's future in much greater detail.
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.
Take a deep breath—Earth is not going to die as soon as scientists believed. Two new modeling studies find that the gradually brightening sun won't vaporize our planet's water for at least another 1 billion to 1.5 billion years—hundreds of millions of years later than a slightly older model had forecast.
Within a few days, however, the temperatures would begin to drop, and any humans left on the planet's surface would die soon after. Within two months, the ocean's surface would freeze over, but it would take another thousand years for our seas to freeze solid.
Once the sun becomes a giant, the habitable zone will move out to between 49 and 70 astronomical units. Neptune in its current orbit would probably become too hot for life; the place to live would be Pluto and the other dwarf planets, comets and ice-rich asteroids in the Kuiper Belt.
Eventually, the entire contents of the universe will be crushed together into an impossibly tiny space – a singularity, like a reverse Big Bang. Different scientists give different estimates of when this contraction phase might begin. It could be billions of years away yet.
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.
It is the pull of the Moon's gravity on the Earth that holds our planet in place. Without the Moon stabilising our tilt, it is possible that the Earth's tilt could vary wildly. It would move from no tilt (which means no seasons) to a large tilt (which means extreme weather and even ice ages).
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.
Our Sun is just one of about 200 billion stars in our galaxy.
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.
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.
As the universe keeps ballooning, stars, including our own sun (after first becoming a red giant and incinerating the Earth), and even black holes will eventually radiate away all their energy, and the universe will go dark, forever.
Even though certain features of the universe seem to require the existence of a multiverse, nothing has been directly observed that suggests it actually exists. So far, the evidence supporting the idea of a multiverse is purely theoretical, and in some cases, philosophical.
The trite answer is that both space and time were created at the big bang about 14 billion years ago, so there is nothing beyond the universe. However, much of the universe exists beyond the observable universe, which is maybe about 90 billion light years across.
Mercury will be swallowed by the Sun during its first red giant phase. Venus may survive the first phase, but will be consumed during the second giant phase. In all but the direst scenarios, Mars will survive the Sun's final stages of evolution.
Potential for Life. The surface of Pluto is extremely cold, so it seems unlikely that life could exist there. At such cold temperatures, water, which is vital for life as we know it, is essentially rock-like. Pluto's interior is warmer, however, and some think there could even be an ocean deep inside.
In about 5 billion years, the Sun is due to turn into a red giant. The core of the star will shrink, but its outer layers will expand out to the orbit of Mars, engulfing our planet in the process. If it's even still there. One thing is certain: By that time, we won't be around.
In space or on the Moon there is no atmosphere to scatter light. The light from the sun travels a straight line without scattering and all the colors stay together.
By 2050 , the world's population will exceed at least 9 billion and by 2050 the population of India will exceed that of China. By 2050, about 75% of the world population will be living in cities. Then there will be buildings touching the sky and cities will be settled from the ground up.