IF THE SUN DISAPPEAR TODAY,HOW LONG WOULD IT TAKE BEFORE EARTH WAS UNINHABITABLE?

If the Sun disappeared suddenly (don't ask how), people on Earth would not know of it for about eight minutes and nineteen seconds.
~ Earth normally experiences darkness half of each day and cools several tens of degrees. Now it would also cool during the other half so surface cooling is twice as rapid.
~ Within the first two days the air temperature would be so low that no moisture could remain in it. Without clouds the Earth's heat would radiate away more quickly.
~ Within four days all the Earths greenhouse gasses (water vapor, carbon dioxide, methane, nitrous oxide and ozone) in the atmosphere would have turned to a liquids and solids speeding the cooling even more.
Within one week all land areas would be frozen at least to a depth of 10 to 20 feet. The land would eventually freeze to a depth of about 1/3 to 2/3 of a mile. Except for the deepest areas, the oceans would freeze miles deep in less than a year. Near the ocean floor the water may not freeze because of Earth's internal heat.
Most animal and plant life would die when the atmosphere liquefies. Some single celled life forms would possibly continue to live deep in the Earth's crust (up to five miles) although the habitable zone may change dramatically and those life forms would not be capable of moving to better climes.Some life would continue at hydrothermal vents on the sea floor.

THE SMALLEST VERTEBRATE IN THE WORLD?

At an average of 7.7 millimeters long, the newfound Paedophryne amauensis is a hair smaller than the previous record holder, the Southeast Asian fish species Paedocypris progenetica, whose females measure about 7.9 millimeters.

During recent field surveys in southern Papua New Guinea, scientists found P. amauensis and  another new species of tiny frog, Paedophryne swiftorum, which measures about 8.6 millimeters,This frog is so small it fits on a coin of 10 cents.

Indeed, the frogs likely evolved their tiny sizes to eat tiny invertebrates, such as mites, that are ignored by bigger predators, said study co-author Christopher Austin, a bPaedophryne amauensis is a species of frog from Papua New Guinea discovered in August 2009 and formally described in January 2012. At 7.7 mm (0.30 in) in length, it is considered the world's smallest known vertebrate.

The newly described frog species was listed in the Top 10 New Species 2013 by the International Institute for Species Exploration for discoveries made during 2012. The list was announced on 22 May 2013
The frog species was discovered in August 2009 by Louisiana State University herpetologist Christopher Austin and his PhD student Eric Rittmeyer while on an expedition to explore the biodiversity of Papua New Guinea. The new species was found near Amau village in the Central Province, from which its specific name is derived. The discovery was published in the peer-reviewed scientific journal in January 2012.
Because the frogs have calls that resemble those made by insects and are camouflaged among leaves on the forest floor, were difficult to detect. While recording nocturnal frog calls in the forest, Austin rittember used triangulation to identify the source of an unknown animal and discovered the frogs by scooping up handfuls of leaf litter and putting it into plastic bags where they spotted the tiny frog hopping around.
This time they have returned from an expedition of three months on the island of Australasia with two new species of tiny frogs belonging to the same genus.. One is the vertebrate animal , the smallest animal bones is known.

The scientific description of the species is published in the latest issue of the journal,. The frog lives in soil, in wet litter under the tropical forest.

On the importance of the discovery, the child's father, Dr. Austin, has said: "New Guinea is a hotspot of biodiversity and everything new that we discovered adds another layer to our overall understanding of how biodiversity is generated and maintained ".

In that sense, the father of the child said: "The size limits that are vertebrates are of great interest to biologists because little is known about the functional limitations caused by extreme body size, whether large or small."

More than 60,000 vertebrates in the world and the largest of them are known is the blue whale, with more than 25 meters. The lesser known to date was a fish located in Indonesia that is between 7.9 and 10 millimeters.

WE WILL RUN OUT OF BREATHABLE OXYGEN

It would take a very long time for all the oxygen already in the atmosphere to be used up by respiration of the life on earth even if the generation of oxygen stopped immediately and completely tomorrow.  

I could not find data for the total respiration rate of life on earth, but since respiration is essentially the burning (with oxygen) of the food (fuel) that life consumes, we could instead look at the question of whether we would run out of oxygen if we were to burn all of the biomass on earth.  After all, when one organism eats another organism as food, it will eventually "burn" the food organism - so by considering the burning of all organisms we are considering the case where life eats all other life on earth.

Now according to Wikipedia the earth's total biomas is 560 billion tonnes. That total biomass is only about 1/45,000th of the mass of the atmospheric oxygen of the earth . So it is clear that burning all the biomass of the earth would only decrease atmospheric oxygen content by a tiny amount.

That is why short term fluctuations in the rate of oxygen generation in photosynthesis compared to the short term rate of oxygen consumption in respiration does not matter. The huge buffer of oxygen in the atmosphere totally damps out these short term fluctuations - it is only the long term balance of generation and consumption of oxygen which will make any change significant to the total oxygen content of the atmosphere. By long term I mean millions to billions of years! Any short term change in the atmosphere oxygen percentage would be insignificant compared to the ecological disaster of photosynthesis significantly decreasing on earth.  The disaster would be in the food availability, not in oxygen availability

So don't worry about oxygen depletion, but do worry about possible ecological disasters that would affect life on earth. The disaster will be ecological, not due to a lack of oxygen.

ALVARO EGIDO 

WHAT WOULD HAPPEN IF EVERY ELEMENT ON THE PERIODIC TABLE CAME INTO CONTACT SIMULTANEOUSLY?

The first method would require energy equivalent to dozens of Large Hadron Colliders-an impressive and extremely treacherous experiment indeed. The second method would be putting together a chunk of each element and observe what happens.Both, however, would eventually create carbon monoxide and a pile of rust and salts rather than a cool Frankenstein element.

Atoms are made up of a nucleus of neutrons and protons with a set number of electrons circling around them. Molecules form when atoms’ electron orbital’s overlap and effectively hold the atoms together. What you get when you mix all your atoms will be influenced by what’s close to what. Oxygen, for example, is very reactive, and if it is closest to hydrogen, it will make hydroxide. If it is nearest to carbon, it will make carbon monoxide. Certain elements, such as the noble gases, wouldn't react with anything, so you'd be left with those and a few commonly found two- and three-atom molecules.

Ramming the atoms together at 99.999 percent the speed of light—the top speed of particles in the Large Hadron Collider, at the CERN particlephysics lab near Geneva—might fuse a few nuclei, but it won't make that cool Frankenstein element. More likely, they would meld into a quark-gluon plasma, the theoretical matter that existed right after the universe formed.