When I started this blog I sought to share with everyone what might be considered "weird science". Not weird because it's not true, or it was discovered in some strange fashion but because the conclusions it gives us are not easy to accept into our daily lives.
The fact that the measured speed of light tells us that we are often looking into the past is one of those.
Let's start with some easy examples:
The Moon
The Moon is approximately 400,000 km (the amount of kms most cars end up going in their lifetime!) and speed of light is about 3 m/s, so the time it takes light to travel between Earth and the Moon is: 1.26 seconds.
So..if the Moon blew up, we wouldn't see the explosion for 1.26 seconds
The Sun
The Sun is about 150,000,000 km (no car can put that much on it's engine, not even a Honda) away from Earth.
So ..if the Sun blew up, we would still see the Sun up in the sky for about 8.3 minutes
Everything Else
Just recently I talked about a famous image from the Hubble space telescope containing thousands of galaxies. Now, if we apply the concept above to these images we get an astounding conclusion:
The stars and galaxies we are seeing in all of these images are actually in the past, not a few seconds or minutes..but years and years into the past:
As you can see from the image above the further out a telescope captures an object the further back it is in time as far as we can see (i.e almost a billion years).
Basically the light waves from that object took a billion years to reach us, so we have no idea what it's current state is and we wont know for another billion years.
Just another example of #Scale.
Always in the Past
My final thought that I want to leave you with is this. If light travels at a certain speed and is not instantaneous, does this mean we're always seeing things in the past? The simple answer is yes.
But, it's so fast that for all intents and purposes it's instant (nanoseconds). Still something to think about when you see your friend waving at you from a distance...
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