Why do I believe there is intelligent life elsewhere in the universe? Pure numbers. There are an estimated 500 billion galaxies estimated to be in the observable universe. In each one of those galaxies, there are an estimated 200 billion stars. If you multiply that out using low-end numbers you get 100,000 billion billion (or 100 sextillion) stars.

A new study suggests there are a mind-blowing 300 sextillion of them [stars], or three times as many as scientists previously calculated.

Associated Press
December 1, 2010

If only 1 in a million have at least 1 planet, that gives us 300 quadrillion planets. If only 1 in a million of those have life, that leaves 300 billion planets with life. If only 1 in a million of those have intelligent life, that leaves 300,000 planets with intelligent life.

Think about that…300,000 other earths. And that’s if we use very conservative numbers. The numbers are probably (in my opinion) much higher. If we use a higher ratio, like 1 in a 1,000 instead of 1 in a million, the final number would be 300,000,000,000,000 (300 trillion) earths. My guess (somewhere in the middle) is that there are millions, if not billions, of intelligent life civilizations in the universe.

But the truth is that we really don’t know the ratios. We have only started discovering other planets and we have no idea if any of them have life. We just recently found out they exist. It’s frustrating to hear people say that since we haven’t found any evidence of life beyond earth so far, there must not be any.

To that I say…smack! We’ve only been looking for about 50 years, only 20-25 with any real technology. So, 20-25 out of 13.7 billion years that the universe has been in existence. And we’ve found, what…500 planets so far? How many of those have we actually sent probes to? Five? Six? How many of those have we studied closely? One? Two? (All within our Solar System.)

Heck, we’re still discovering things about our moon. We have yet to step foot on another planet. How can we possibly know that there’s no life elsewhere in our galaxy, let alone the universe? We have only seen a speck of what’s out there, one grain of sand from an entire coastline of beach…a mere sliver of possibilities. It would be like collecting an eye dropper of water from the ocean and from that determining that there’s no fish in the sea.

There’s a philosophical notion (I forget the name) that says if we are the only life in the universe, then we must be special, and hence, our part of the universe must be special as well. But that’s not what we see. The universe everywhere is very similar to what we have here.

So why do we believe ourselves to be special? Hubris. People want to believe that we humans are special, divine, the pinnacle of creation.

Balderdash, codswallop, wishful thinking I say. Delusions of granduer that arise from a mixture of mortality and abstract thought. It is likely that intelligent life elsewhere feels that they are special and divine, that they have a unique place among the stars, that they are their creator’s chosen ones (assuming they have religions), just as we humans do.

Having said that…

There is a more realistic question of whether we will ever contact another intelligent lifeform. While there may be millions or even billions of other civilizations in the universe, there are hundreds of billions of galaxies. So it is possible that there are not that many, if any others, within our own galaxy.

When we achieve efficient means of inter-stellar travel (yes, I said when), it is possible that we could travel our own galaxy for many lifetimes without bumping into any other beings. It’s that big. And at the moment, inter-galactic travel is so far beyond inter-stellar travel that civilizations in other galaxies don’t even merit consideration.

Even more, there is an element of time to consider. What’s to say that all civilizations are developing at the same point in history?

If an alien civilization did try to contact us at anytime in the past 4.5 billion years (other than right now), they would have found nothing here on this planet. We have only had the technology to send and receive communication signals from space for about 50 years (advent of communication satellites). Reversing that, what are the odds that we will be able to contact another planet during the exact time period that intelligent life exists there as well? Slim, very slim.

If we do ever contact intelligent alien life, it will truly be one of the greatest moments in human history. And we’ll probably have to reconsider how common life really is.

But to assume that we are the only ones in the entire universe is just absurd. Life is part of nature and there’s just too much nature for there not to be more.

Most people have a decent understanding of commonly used scales and measurements. If you ask someone to show you a foot, they will generally spread their hands out about 10-15 inches; close enough. But when people start talking about extremely large or small amounts, they become confused and often use the wrong words in their conversations.

For example, when talking about government spending it is not uncommon for people to mistake million with billion or trillion. Probably not important for the conversation at hand, because we know that what they really mean is “a large amount.” But in reality there is a huge difference between these numbers. A trillion is a million times more than a million. Big, big difference.

The same holds true when people talk about space. I have watched sci-fi TV shows that don’t know the difference between a galaxy and the universe. I think hearing and seeing these perpetual mix ups contribute to a communal misunderstanding of our universe.

So I have created a list below as a chart of how big or small things are and how they fit together.

From largest to smallest:

Object	Size Across	Comment
Multiverse	??	Theoretical. Contains multiple universes
Universe	93,000,000,000 (93 billion) light years	Everything there is. All of space.
Universe, Observable	14,000,000,000 (14 billion) light years	Everything we can see. The universe is estimated to be 14 billion years old. The light from an object more than 14 billion light years away would take longer to get to us than the universe has existed. As such, these objects are beyond our ability to observe.
Galactic Supercluster	150,000,000 (150 million) light years	A collection of galactic groups (or clusters). Ours is called the Local Supercluster.
Galactic Group	10,000,000 (10 million) light years	Groups of galaxies. Our Local Group includes our Milky Way Galaxy, the Andromeda Galaxy, the Triangulum Galaxy, and about 30 others. The next closest group is called the Virgo Group.
Galaxy	120,000 light years	Current estimates put the number of galaxies in the observable universe to be 500 billion. Our galaxy is called the Milky Way. Other galaxies include the Andromeda Galaxy (M31) and Virgo A (M87).
Nebula	1-25 light years	Well-known nebulae in our Milky Way Galaxy are the Crab Nebula, Orion Nebula, and Eagle Nebula (which contains the recently famous Pillars of Creation).
Planetary System	0.15 light years (1.5 trillion kilometers)	Planets and other gravitationally bound objects orbiting a star. Ours, the Solar System, contains the Sun, the Earth, the other planets, many moons, an asteroid belt, and some other objects.
Star	1,400,000 kilometers	Current estimates put the number of stars per galaxy to be 200 billion. Our star is called Sol, which is why we call it the Sol-ar System.
Earth	12,700 kilometers	You are here.
United States	4,200 kilometers	Wider than our moon (3,500 km) and Pluto (2,300 km). Almost as wide as Mercury (4,900 km).
Marathon	42 kilometers (26 miles)	All true marathons are 26 miles in length, including the annual Boston Marathon.
Mariana Trench	11 kilometers	Lowest recorded point on our planet (Pacific Ocean).
Mt. Everest	8.8 kilometers	Highest record point on our planet (Nepal)
Eiffel Tower	320 meters	Viva La Paris
Oak Tree	20 meters	Typical height
Human	1.7 meters	Typical height
Microwave wavelength	1 centimeter	Cooks your food fast
Ant	4 millimeters	But a lot of them add up quickly!
Human Eyelid	0.5 millimeter	Thinnest skin on your body
Dot	0.1 millimeter	Smallest size observable to the naked eye.
Pollen	50 micrometers	You can’t see individual pollen particles, only clumps of pollen.
Red Blood Cell	7 micrometers	Average human has 25 quadrillion RBC’s. That’s 25,000,000,000,000,000,000.
Bacteria, Average	1-2 micrometers	Smaller than blood cells, but larger than viruses
HIV Virus	90 nanometers	Slightly smaller than the grooves of information on a CD or DVD.
DNA	3 nanometers	Thickness of a DNA strand
Computer Transistor	2 nanometers	1-2 billion transistors on a typical computer processor chip.
Water Molecule	280 picometers	You can see that computer transistors are getting down to the molecular level.
Hydrogen Atom	25 picometers	Smallest atom
X-Rays	5 picometers	Not the smallest wavelength, but getting there.
Proton	1 femtometer	Neutron is about the same size. Proton and neutron together make up nucleus of an atom.
Quark	1 attometer	Quarks are particles that make up protons and neutrons.
Preon	1 zeptometer	Building blocks of quarks.
Neutrino	1 yoctometer	Pass through solid objects undetected.
Superstrings	Planck Length (0.0000000001 yoctometers)	1-dimensional strings of energy that make up the all matter and energy in the universe. There is no shorter length, even theoretically. This is also called quantum foam; the fabric of spacetime.

I also found a very cool visual display of this chart from Primax Studio.