"I hope you feel things you never felt before. I hope you meet people who have a different point of view. I hope you live a life you’re proud of, and if you’re not, I hope you have the courage to start all over again." -Eric Roth, screenwriter

Forget the prognosticators, the fortune-tellers and the mediums. Pay no mind to the soothsayers, the prophets, the augurs and diviners. The seers see no more than any other sighted person, the omen-interpreters have been superseded by the ornithologists, the psychics made obsolete by the scientists.

Because if doomsday ever does approach, we won't be warned because of an ancient prediction, but rather because we listened to and made steps towards understanding the Universe around us.

Image credit: NASA / Paul Chodas, Jon Giorgini & Don Yeomans / JPL NEO Program Office.

So forget about whatever end-of-the-world conspiracy you've heard, whether it's the current flavor or any other, and let's get right down to the science of it.

The world -- the beautiful, terrifying, and wonderful Earth that all humans and our distant cousins and ancestors have lived upon -- will not last forever, and neither will we, nor will our descendants. At some point, this will all be gone.

Image credit: the MODIS instrument on NASA's Terra satellite.

Our living world, the Earth, will not live forever, and neither will anything on it. But that is a simple scientific truth, and it is a consequence of the way we came to exist. We continue to learn as much as we can about how everything in the Universe works -- from the origin of spacetime and matter to the origin and evolution of life on Earth -- and it is, without a doubt, the most remarkable story ever conceived of.

Image credit: The Flame Nebula in IR by ESO / J. Emerson / VISTA. Mods unknown.

This Universe was born without life, planets, or even the elements needed to piece them together. It was only through a series of the most violent processes known in nature -- where the plasma of the hot, early Universe cooled to form nuclei and atoms, those atoms cooled and contracted under gravity to form stars, generations of stars burned through their nuclear fuel, enriching the Universe with heavy elements -- that enabled the Universe to eventually form new generations of stars with planets, complex molecules, and eventually life.

But just as Carl Sagan did exactly 16 years ago today, no living organism lives forever, and we all succumb to the mercy of time.

Image credit: Johan Mathiesen of http://bloggingadeadhorse-dmt.blogspot.com/.

The death of an individual life is not the end of the world, but for each of us, when it comes to our own lives, it may as well be; it is the end of our personal world.

Coming to terms with our own mortality is something that it would not only serve us all well to do, but to recognize that this is a journey and an existential struggle that all humans should have the intelligence and bravery to face. If you don't come to terms with that, how else would you come to terms with this next fact?

Image credit: Tony Narcisse.

Human life on this world will very likely continue to exist after you have ceased to do so.

There are seven billion of us now, inhabiting all seven continents, including many regions that were once thought to be uninhabitable. The damage that we do to this world and to one another can be catastrophic, but life is resilient and there are a great many of us. Moreover, the Earth comes equipped with a number of defenses against the most common types of dangerous occurrences, such as our substantial, layered atmosphere and our self-sustaining magnetic field.

Most of the doomsday scenarios you hear of -- earthquakes, volcanoes, solar flares, nearby supernovae, asteroid strikes, etc. -- would be potentially destructive to humans, but wouldn't wipe out all humans on Earth. Unless a real catastrophe happens, humans will continue to exist for many generations to come.

But that does not equate to forever.

Image credit: Nuclear test on the Mururoa atoll in French Polynesia; AP Photo.

At some point in time, either through catastrophe or evolution, human beings will cease to exist.

There are some real catastrophes that can cause the extinction of our species. These can be man-wrought, such as through catastrophic modification of the environment, global nuclear war, or collapse of the food chain, or it can be natural, such as an "Earth-killer" asteroid strike, a very nearby supernova, or -- perhaps most prosaically -- enough time, genetic mutation, and natural selection so that our surviving descendants, long-term, cease to possess the qualities that we have determined "make us human."

Image credit: Patrick Bolvin. Yes, it's a joke; I know that's not how evolution works!

But even in these catastrophic cases, even after the last human has died off, life on Earth will continue to exist.

During the worst mass extinctions in Earth's history, 30-to-50% of the species living on our planet at that time died off. Even 65 million years ago, with the asteroid that wiped out the dinosaurs, more than half of the species survived! And no matter what doomsday scenario we concoct, there is nothing we've yet conceived of that could halt the life cycle of every bacteria, virus, protist and fungus on Earth, including species so far removed from our experience that they don't even require the Sun!

Image credit: NOAA PMEL Vents Program.

The day will come, however, where even the most elusive life in the deepest hydrothermal vent will cease to survive and reproduce. An estimated one-to-two billion years in the future, all life on Earth will cease to exist. And you can thank the Sun for that.

Image credit: Wikipedia user RJHall, based on Ribas, Ignasi (2010).

As the Sun continues to burn through its nuclear fuel, it burns faster and more luminous, and over time, that increased energy output will be sufficient to increase the surface temperature of the Earth above the boiling point of water. And when it does, the oceans will cease to exist, and so will the basic biological processes that drive all life on Earth as we understand it.

In one sense, one-to-two billion years from now, that will be the end of the world. But in another sense, the Earth will still be here, albeit devoid of life, just like all the other worlds (we think) in our Solar System. But even that will not last forever.

Image credit: Atacama Large Millimeter/submillimeter Array (ALMA).

Because in five-to-seven billion years, the Sun will run out of hydrogen in its core and become over a hundred times as large and luminous as it is today, entering its red giant phase. At this point, it will roast the Earth with wave after wave of ionized plasma, stripping off our entire atmosphere and possibly engulfing our entire world into the central star itself.

That, truly, will be the end of the world.

Image credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA).

And yet, the many atoms that made up the Earth, that made up past and (relative to us) future life on Earth, and that make us up right now, will be returned to the interstellar medium, where they will someday make future generations of stars, planets, and possibly living creatures once again.

The real end of the world is not yet upon us, but when it does come, it is far more wonderful and terrifying than any doomsdayer has ever prophesied. And I hope you never forget just how spectacular and precious your existence -- in the midst of all of it -- happens to be.