I found this fascinating:
Today, we bring you some food for thought about the reality of perception -- not the glass empty or half full debacle, but the sort of perception that seriously impairs us on a cosmological time scale, and biologically too. As we know, due to the finite speed that light travels in a almost-perfect vacuum, we are incapable of seeing things in "real time." We see the moon as it was 1.3 seconds ago, the sun eight minutes ago, Proxima Centauri (the closest star from Earth) as it was more than four years ago, and the Andromeda galaxy (our closest galactic neighbor) as it was more than 2.5 MILLION years ago.
In essence, observing anything in space from our little chunk of rock is surprising, in the sense that simply looking out into the night sky is the closest thing to time travel we currently know of. In the same way, observers in other parts of our galaxy could look at Earth's development over the course of our evolutionary time-line, and they would see the Earth as it appeared hundreds, perhaps thousands of years ago (depending on which part of the galaxy they live in and how far away this location is from Earth).
The phenomena of how fast the speed of light is also allows us to study the universe as it appeared mere hundreds of millions of years after the big bang occurred. The most distant sources of light were emitted from the first generation of stars and galaxies in the primordial universe more than 13.7 billion years ago.
Something else that limits our overall perception of the universe is our inability to see light in all of its various wavelengths. Light with properties of both particles and waves (in its various forms) is just like the universe, in that it is an expression of energy. Albeit, an extraordinarily unique expression of it. Most obvious to us is light at optical wavelengths, which is emitted from many stars glittering throughout the universe. Then there is light at ultraviolet and infrared wavelengths. Astonishingly, our sun only emits about 44% of its total electromagnetic radiation at optical wavelengths, the rest of it is emitted in other frequencies invisible to the naked eye (but their true nature can be discerned using special tools and filters).
These phenomena are most obvious at large distances, but they are also very applicable to our day to day lives here on Earth, though the effects are not nearly as extreme or noticeable.
I want all of you to stop whatever you are doing for a moment (unless all you are doing is reading this article) and participate in a little experiment with me.
First, close your eyes and extend both of your index fingers. After you've done that, take one of your fingers and touch your nose. With the other finger on the other hand, touch your knee or ankle. Repeat this a few times. (Even better, have a friend do it to you!) After which, you should be able to feel your fingers touching your nose and ankle simultaneously. Think about this for a second...the nerve signal from your ankle had to travel exponentially farther (about twenty times over) to get to your brain than the signal from your nose did, but it *FEELS* simultaneous, doesn't it?
Basically, (and this is trippy) we aren't sure if the ankle and the nose were truly touched at the same time, or if they were touched at slightly different moments, and the brain reassembled asynchronous signals which led to the sensory information being put together at exact same time.
There was actually an experiment done on this very subject where scientists had a group of volunteers press a button that would cause a light to flash after a small delay. After several rounds of this, they found that the volunteers were seeing the flash only milliseconds AFTER they pushed the button, as the brain edited the delay out after it got used to it...suggesting that our brain modifies the sensory information from our bodies in different ways, ways that would typically make more sense to us, causing our consciousness to exist in the past (on a microscale).. kind of like radio stations that operate on a delay of a few seconds to prevent the f-bomb (or something equally scandalous) from being played live on air.
Now, let's tie some of these portions together... if you were to stick your hand straight in front of your face, you will not see a present image of it. Instead, it will be delayed over the course of a few milliseconds due to the constraints of Einstein's theory of special relativity (given the time that it takes light to illuminate your hand, and the biological processes we must undergo before our brain can register stimulus). In addition, we must also factor in the speed of nerves traveling to the visual cortex in the back of our brain, where visual information is sorted through and the "speed of thought," which is largely different form person to person.
In conclusion, many things on a micro and macroscale are directly influenced from our perspective due to a myriad of variables placed on us by the laws of physics and our anatomy itself. There is the reflection and refraction of light scattered in our atmosphere, the observer effect witnessed with subatomic particles, light at various frequencies, and even the properties of time itself, or time dilation more specifically, whose effects can be seen on our satellites in LEO and the event horizons of black holes. All of this bring up an interesting philosophical question... Are we really observing reality, or can we only see into the past--glimpse the world as it was a nanosecond ago?
What are your thoughts?
http://blogs.scientificamerican.com/...of-perception/