Imagine, if you will, a very long length of elastic rope, say, 10 metres long. Take a permanent marker, and while the elastic is "at rest" make
a mark on it every 10mm along its entire length. Now, find two assistants, hand each one an end of the elastic, and instruct them to "take up
the slack". Now, find an ant. Place the ant on one end of the elastic. This is a very special ant, however, as it is very cooperative, and only
walks in perfectly straight lines on lengths of elastic. "On your marks, set, GO!" Time him from one end of the elastic to the other. This we
will call value "c". (Representing the speed of light) The 10 metre length we will call value "d". (representing the diameter of the whole
universe, not just the visible part) Now that the ant is at the other end of the elastic, instruct him to turn around and repeat the process in
the opposite direction. At the same time, instruct your 2 assistants to move apart, stretching the elastic as they go. Additionally, they are
accelerating, taking small steps at fist, then walking, running, sprinting! Now, as you are a perfectly "external" observer, you see the ant
moving at the same velocity "c" in relation to the piece of elastic he is running on. However, his frame of reference, "d", is changing with the
passage of time. If the ant represents the speed of light, then quickly run to catch up with one of your assistants, then look back at the other
assistant. Their relative velocity is MUCH higher than the ant's velocity. But no fundamental laws are being broken, as - to put it simply -
none of those adjacent black marks you made earlier (representing "local" space) are moving apart faster than the ant. Almost, but not quite.
Now... Reset the experiment, make the elastic 1mm long, and attach each end of the elastic to two rifle bullets pointing in opposite directions. (This is INCREDIBLY stretchy elastic, trust me!) Place the ant (this one is a very very small ant!) between the bullets, not quite in the middle of the elastic, and instruct him that when the bullets are fired, he is to run at his standard speed "c" (representing the speed of light) towards the middle of the elastic. Fire the bullets... Watch and be amazed, as within a few thousands of a second, the elastic reaches 10 metres in length, and the ant, running at "light speed" has only covered 1mm or so in the same amount of time. For arguments sake, lets say the bullets each hit a target, lodging in place with the elastic still attached. This represents "now". The ant is representing a photon from the beginning of the universe and it hasn't yet reached the middle of the elastic, and won't do for probably a couple of minutes. This represents how we can only just be seeing events that occurred at the Beginning. Thanks to the inflationary properties of the early universe, we will continue to receive this light for, well, the remaining lifetime of the universe. Hard to believe that two photons that left their source perhaps a few billionths of a second apart, might (thanks to inflation) reach their target a few billion seconds apart!
Slashdot Mirror
Imagine, if you will, a very long length of elastic rope, say, 10 metres long. Take a permanent marker, and while the elastic is "at rest" make a mark on it every 10mm along its entire length. Now, find two assistants, hand each one an end of the elastic, and instruct them to "take up the slack". Now, find an ant. Place the ant on one end of the elastic. This is a very special ant, however, as it is very cooperative, and only walks in perfectly straight lines on lengths of elastic. "On your marks, set, GO!" Time him from one end of the elastic to the other. This we will call value "c". (Representing the speed of light) The 10 metre length we will call value "d". (representing the diameter of the whole universe, not just the visible part) Now that the ant is at the other end of the elastic, instruct him to turn around and repeat the process in the opposite direction. At the same time, instruct your 2 assistants to move apart, stretching the elastic as they go. Additionally, they are accelerating, taking small steps at fist, then walking, running, sprinting! Now, as you are a perfectly "external" observer, you see the ant moving at the same velocity "c" in relation to the piece of elastic he is running on. However, his frame of reference, "d", is changing with the passage of time. If the ant represents the speed of light, then quickly run to catch up with one of your assistants, then look back at the other assistant. Their relative velocity is MUCH higher than the ant's velocity. But no fundamental laws are being broken, as - to put it simply - none of those adjacent black marks you made earlier (representing "local" space) are moving apart faster than the ant. Almost, but not quite.
Now... Reset the experiment, make the elastic 1mm long, and attach each end of the elastic to two rifle bullets pointing in opposite directions. (This is INCREDIBLY stretchy elastic, trust me!) Place the ant (this one is a very very small ant!) between the bullets, not quite in the middle of the elastic, and instruct him that when the bullets are fired, he is to run at his standard speed "c" (representing the speed of light) towards the middle of the elastic. Fire the bullets... Watch and be amazed, as within a few thousands of a second, the elastic reaches 10 metres in length, and the ant, running at "light speed" has only covered 1mm or so in the same amount of time. For arguments sake, lets say the bullets each hit a target, lodging in place with the elastic still attached. This represents "now". The ant is representing a photon from the beginning of the universe and it hasn't yet reached the middle of the elastic, and won't do for probably a couple of minutes. This represents how we can only just be seeing events that occurred at the Beginning. Thanks to the inflationary properties of the early universe, we will continue to receive this light for, well, the remaining lifetime of the universe. Hard to believe that two photons that left their source perhaps a few billionths of a second apart, might (thanks to inflation) reach their target a few billion seconds apart!