It is sometimes abbreviated Gy, Ga ("giga-annum"), Byr and variants. The abbreviations Gya or bya are for "billion years ago", i.e. billion years before present. The terms are used in geology, paleontology, geophysics, astronomy, and physical cosmology.
, the sun will run out of hydrogen. Our star is currently in the most stable phase of its life cycle and has been since the formation of our solar system, about 4.5 billion years ago. Once all the hydrogen gets used up, the sun will grow out of this stable phase.
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.
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.
Four billion years from now, the increase in Earth's surface temperature will cause a runaway greenhouse effect, creating conditions more extreme than present-day Venus and heating Earth's surface enough to melt it. By that point, all life on Earth will be extinct.
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.
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.
What would happen if the moon disappeared for 5 seconds?
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).
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.
The sun is no different, and when the sun dies, the Earth goes with it. But our planet won't go quietly into the night. Rather, when the sun expands into a red giant during the throes of death, it will vaporize the Earth.
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.
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.
Temperatures in the corona — the tenuous, outermost layer of the solar atmosphere — spike upwards of 2 million degrees Fahrenheit, while just 1,000 miles below, the underlying surface simmers at a balmy 10,000 F.
Would the Earth survive if the Moon crashed into it?
What would happen if the Moon crashed into Earth? Everything on Earth would die. The only way to survive this collision would be to leave Earth. The Moon and Earth would both be destroyed; the Earth would probably be split into numerous smaller pieces.
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.
You might be wondering just how many missions and how many people have been to the Moon. In fact, during nine Apollo missions, 24 astronauts went to the Moon, and 12 of them had the opportunity to walk on it.
But on Mars, carbon dioxide is 96% of the air! Meanwhile, Mars has almost no oxygen; it's only one-tenth of one percent of the air, not nearly enough for humans to survive. If you tried to breathe on the surface of Mars without a spacesuit supplying your oxygen – bad idea – you would die in an instant.
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.
At the Equator, the earth's rotational motion is at its fastest, about a thousand miles an hour. If that motion suddenly stopped, the momentum would send things flying eastward. Moving rocks and oceans would trigger earthquakes and tsunamis. The still-moving atmosphere would scour landscapes.
If the Earth stopped spinning, you wouldn't suddenly be launched off into space. Gravity would still keep you firmly on the ground. There would be lots of changes, though. If Earth were to stop spinning but continue to orbit the sun, a "day" would last half a year, and so would the night.