Do Aliens Really Exist Essay Format

While I sit very firmly on the side that believes these reports more likely have an unremarkable and terrestrial explanation, whether alien life exists is a very real and credible scientific question. What is the possibility that life -- and even intelligent life -- exists around a star other than our own? And how can we find out?
In 1961, Frank Drake wrote down what is now called the Drake Equation, which is frequently used to help guide thinking about extraterrestrial life. The equation multiplies a string of probabilities -- such as the fraction of stars with planets, the fractions of planets that are habitable, and the percentage of times intelligent life forms -- to give an estimate of the likelihood that we are not alone in the universe.
When Drake wrote down his equation, very little was known about any of these probabilities. They were all pretty much guesses. However, using the best guesses of the day, he estimated there were 10 planets in the Milky Way galaxy emitting radio waves and thereby detectable in principle by Earth-based radio telescopes.
A lot has changed in the last half-century and we now have a much better understanding of some of these numbers.
So, what do we know for sure?
While the universe is vast, let's restrict our investigation to only our own Milky Way, as other galaxies are very far away and the idea of traveling between them is even more daunting than interstellar travel. So, I'll only talk about our celestial neighbors.
The Milky Way has about a hundred billion stars in it, with some estimates four times larger than that. In 2009, NASA launched the Kepler spacecraft to search for planets around distant stars. What the Kepler mission found was nothing short of astounding. We know that most stars have planets (over 80%). About a quarter of those planetary systems have a planet at a distance from the star that would allow for liquid water. And, of those, 10% to 20% of the time those planets are around the same size as Earth. Combining those numbers, we can estimate with some accuracy that the number of possibly habitable planets in our galaxy is in the neighborhood of 2 billion.
While there is some uncertainty in this estimate, it is relatively firm. We are far less certain in our estimation of whether life will be created, if it will survive, and if intelligence will evolve. If these life-related probabilities are high, say above 50%, then life should be extremely common in our galaxy. If those numbers are low, we could be alone.
For all these factors, we only have our own Earth to guide us. And, of course, generalizing from a single instance is not a wise thing to do. However, we are not completely ignorant even with just our single planet to study.
The Earth is about 4.55 billion years old. However, the early Earth was molten and inimical to life. However, by about 4.4 billion years ago, the Earth cooled enough for water to exist on it. We are not certain exactly when life formed on Earth, but conservative estimates suggest that it was no later than 3.8 billion years ago, with some estimates suggesting the earlier date of 4.29 billion years ago.
No matter the estimate, it is clear that life formed on Earth very soon after the planet cooled enough to have liquid water. This suggests that the formation of life is easy. Were it difficult, one would expect that it would have taken longer. This is not an airtight argument, to be sure. But it is a reasonable one.
Although life formed very early in the life of our planet, multicellular life came much later. It wasn't until oxygen permeated the atmosphere that more complex life could be supported. It was about 540 million years ago that life from which humans evolved came into existence. The fact that it took 3-4 billion years for "our" kind of cells to evolve suggests this process is slow and not at all guaranteed. It requires an abundant supply of a volatile chemical like oxygen to happen at all.
However, we also know that life has survived for about 4 billion years, no matter how many times the universe has tried to snuff it out. The impact 65 million years ago that killed the dinosaurs was a dramatic event in the history of Earth, but it was dwarfed by the Permian extinction 250 million years ago, when 90% of the species on the planet went extinct. Yet life survived. Under Earth-like conditions, life is hardy.
The evolution of intelligence seems to be rarer. Until humans evolved, no other forms of comparable intelligence existed. It is somewhat arbitrary where to draw the line, but our own species, Homo sapiens, came into existence perhaps 200,000 years ago. The earliest species of the genus Homo was Homo habilis and they first evolved around 2 million years ago. By either definition, humanlike intelligence took a long time to appear. Further, if humanity were to go extinct tomorrow, there are no species around that are likely to quickly evolve intelligence. Granted, there are species that are more intelligent than others, but their path to humanlike intelligence is by no means assured. From this, it is possible to provisionally conclude that the evolution of intelligence is rare.
Thus, from what we know and can infer from observation, planets are common, life is probably common and intelligence is rare. We can also conclude that life is hardy on Earth, but Earth may exist in an unusual environment. After all, for life to exist, its host star must be stable and it must not be too close to other stars that could go supernova and bathe the Earth with sterilizing radiation. Indeed, some calculations predict that stars near the center of our galaxy -- a relatively hostile environment -- are not good candidates for life to flourish. Some predictions say that only about 2% of stars exist in benign portions of the galaxy, which means that there are maybe 40 million Earth-like planets in our galaxy.
So, what's the answer? Are we alone in the universe? The honest answer is that we don't know. We know that planets that could support liquid water are common. But we don't know much about the origin of life and the probability that it will evolve as it did on Earth. From what we have seen on Earth, it seems that the creation of life is relatively easy, but the evolution of intelligence is hard. Taken in aggregate, it does seem that extraterrestrial life should exist and there may be planets where our cosmic cousins also look at the sky and dream.
Nobody can tell you for sure what those Navy pilots saw (although I'd bet real money that it was something ordinary). But it's a big universe and it seems that life could very well be common. There may come a day when an alien craft lands on the White House lawn like in the 1950s movie "Earth vs. the Flying Saucers," or, more likely, we hear the first signals in our giant radio telescopes.
Then we would know, once and for all, that we are not alone.
Correction: An earlier version of this piece incorrectly stated the numbers for the possibly-habitable and Earth-like planets in the Milky Way galaxy.

IT'S the biggest question in the universe and scientists are no closer to answering it.

Do aliens exist or are humans totally alone?

Stargazers have spent much of the past century trying to solve this conundrum and have made several unexplained observations along the way.

Once these puzzles are solved, we may have finally proved that aliens exist - or got one step closer to discovering that humanity is the only lifeform in the universe.

Of course, we won't know whether extraterrestrials are real until they get in touch with us or we find evidence of their existence.

And even if we do find alien life, it might be in the form of bacteria or other microorganisms, rather than fully fledged intelligent beings.

But that won't stop astronomers from looking.

We've collected some of the biggest unsolved space mysteries.

Let us know what you think about them by voting in our poll, which is at the bottom of this article.

Is there life on Mars?

The Red Planet is a bit like Earth and is thought to have been covered with water at some point in its ancient history.

Spaced out stargazers claim to have spotted all manner of weird things on Mars, from pyramids to alien bears.

But real scientists are no closer to discovering whether the Red Planet is actually a dead planet, or whether it once supported life.

It is thought Mars was frozen over roughly 3.8 billion years ago before warming periods melted the surface and created deep valleys and canyons.

A build-up of greenhouse gases in Mars’ dense atmosphere is thought to have sparked dramatic climate cycles.

Scientists believe this could by why the planet has water-carved features.

Water provides the conditions needed for life – so there could have been living organisms on Mars billions of years ago.

However,  they could very well have been wiped out by the changing climate.

Is an alien megastructure orbiting a distant star?

In October last year, scientists offered a new theory to explain why a distant star called KIC 8462852, or Tabby’s Star, was displaying a bizarre “blinking” behaviour which caused its light to dim periodically.

One researcher made the serious suggestion that the light was being blocked by a huge object called a Dyson Sphere – a theoretical structure which could be built around a star in order to harvest its energy.

Last year, Jason Wright of Penn State University said the bizarre signals around Tabby’s Star looked like a “swarm of megastructures” and suggested they were “something you would expect an alien civilisation to build”.

“I can’t figure this thing out and that’s why it’s so interesting, so cool – it just doesn’t seem to make sense,” he told The Independent.

Other scientists have claimed the behaviour of Tabby’s Star could be caused by a swarm of orbiting comets which periodically block out its light or suggested it was the result of a complex phenomenon called "avalanche statistics".

Are aliens trying to contact us?

Scientist have picked up number of strange signals from distant stars in recent years.

Whilst most of them probably come from natural sources, some signals may have been sent by aliens.

Last year, astronomers Ermanno F. Borra and Eric Trottier published a paper with the title "Signals probably from Extraterrestrial Intelligence" detailing the discovery of 234 signals.

The duo wrote:  "We consider the possibility, predicted in a previous published paper, that the signals are caused by light pulses generated by Extraterrestrial Intelligence to make us aware of their existence."

Sadly, we're no closer to working out what aliens are trying to say - or whether they were actually saying anything at all.

Are extraterrestrials living in an ocean on Jupiter's moon?

Some scientists believe Europa, which is about the size of Earth’s moon, has an ocean hidden beneath its frozen crust.

If the predictions turn out to be correct, this could be a great place to look for alien organisms.

“With abundant salt water, a rocky sea floor, and the energy and chemistry provided by tidal heating, Europa could be the best place in the solar system to look for present day life beyond our home planet,” NASA said last year.

The moon is thought to boast a huge global ocean containing twice as much water as Earth's oceans lurking beneath a layer of extremely cold and hard ice of unknown thickness.

NASA believes it has found evidence of water vapour plumes erupting off the surface of Jupiter’s moon.

Could these plumes contain traces of life that allow scientists to solve this space mystery?

Are we aliens?

Some scientists believe humans are the descendants of Martian life which was carried to Earth billions of years ago on an asteroid. 

Scientists believe life might have begin on Mars and then “contaminated” our own planet.

It’s believed life had a better chance of getting started on the now arid planet in ancient times because it used to have the right conditions for alien life – like water and a possible atmosphere.

They think that an asteroid collision caused by space rocks in our solar system smashing into each other might have caused a chunk of life from Mars to land on Earth.

Astronomer Caleb Sharf told Business Insider: “We can find pieces of Mars here on Earth and we suspect that there are pieces of Earth on Mars.

Are there any inhabitable planets near Earth and are they home to life?

Stargazers have already spotted several "exoplanets", which is the name given to planets outside our own solar system.

Since its launch in 2009, NASA’s planet finding Kepler Spacecraft has discovered more than 4000 exoplanet candidates.

Of these, there have been 216 Earth-like located within the Goldilocks Zone — the region around a star in which the surface temperature of an orbiting planet might support water.

The problem is that while most of these Earth-like planets are habitable, they are located thousands of light years away, which means they are out of our reach.

However, astronomers recently found a “second Earth” capable of supporting life.

Astronomers at the European Southern Observatory (ESO) spotted an alien world orbiting Proxima Centauri — a red dwarf, a small low-mass star about 4.25 light-years from the Sun, which they called Proxima b.

They also found a world orbiting a nearby star 14 light years away, which may have an atmosphere that can support life.

European stargazers trained their telescopes on a planet called GJ 1132 b to discover that its blanketed by a thick atmosphere of “alien air”.

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