Giant Aliens

Here's a question for you to ponder, what size would an alien be? 

To answer that question you need to define a few things, let's start by saying we mean intelligent alien life, not just bacterial or microbial form.  Next we need to define what scale we would use to measure their size.  Let's use a single Human as our method of measurement.  So in this case a "giant" alien would be one that is considerably larger than a human maybe 10 times as an example.

We have to stop and think for a moment, what size do we expect an alien would be, and whether that is realistic to assume.  In terms of humanity our size is largely determined by gravity here on Earth.  If gravity were to be stronger then humans would get shorter as a result and likewise if gravity were to be weakened we would become taller as a result.  When you stop and think about that you can make assumptions of an alien's size dependent on the planet that it originated on and the gravity of that planet.  The problem with that assumption is that we are not the only species on this planet and there are many which are considerably larger or considerably smaller than humans by comparison.

This brings us back to square one, as there are many variable to consider here, why is it that in science fiction, even in the realms of science fact which actually takes the possibility seriously, our vision of an alien is always proportional in size to a human?  Is that even realistic to assume?  Given the likelihood that life exists what is the likelihood that it would look anything like us?

This all inspires another big question - or a small question to be more precise: what if aliens do exist and in reality they are incredibly small by human standards?  What if aliens exist 100th the size of a human - would we even detect their spacecraft enter our atmosphere?  Would we notice their descent, and crucially would the even be able to communicate with us?  Imagine if we found a planet 1,000 times the size of Jupiter inhabited be a race of aliens that were 100 times our size.  How would you even get them to notice you?  Would you even be able to communicate with them?

If you make assumptions based on technological advancement and assume they discover much of the same technology that we have such as Radio Frequency Communication then consider the idea of trying to communicate with a radio antenna 100, maybe even 1,000 times the size of our own - it would be impractical for us to even create a transmitter capable of generating a signal with enough power to be noticeable.  As for the idea that they would spot our communication that relies on minute barely detectable signals being scrutinized.  How much attention do we pay to such minute fluctuations ourselves? 

There is also the intriguing question of whether or not the human race would be prejudiced and deem an alien race so small as being insignificant - that prejudice would likely be the same we would face if we found a race considerably larger than us.