Have you ever wanted to look back in time?

What if I told you that every one of us have seen visions of the past dating back from a few minutes to as much as millions of years ago, would you believe it? It's true.

And when I say Vision I don't mean something symbolic or metaphorical. I literally mean you have seen the past with your own two eyes!

So to understand this we first need to understand what it means to SEE -- How exactly do your eyes work?

If you've ever seen white light hit a prism before you have seen it break up to its component colors in the light spectrum.

When our surroundings are brightened up by a light source most of the light is absorbed by the surroundings but some of the light that isn't absorbed bounces off the surroundings.

Light is what COLORS are made of. When you see something red it means that most of the light that hit the object had been absorbed but the Red from the light spectrum bounced off and reached your eyes.

Your eyes simply absorb the light bouncing off the surroundings and convert it to electrical signals that your brain understands -- That is your eyesight. The images you see are just combinations of different light beams bouncing off and reaching your eyes.

Although light is super fast (Speed of light: 3x10^8 m/s) it is still limited in covering large distances, and this is where it gets interesting: Your eyesight sees IMAGES which are light beams bouncing off the surrounding but there is a delay for the image to reach your eyes.

If you're just a few feet away from something you're looking at then the delay would be insignificant since the image you're seeing is moving at the speed of light.

But let's try and imagine if the object you're looking at was REALLY REALLY REALLY FAR AWAY but still be big enough for you to notice it, would there be a difference at all?

Let's take the Sun for example.

The Sun is really big not to notice and it's distance from the earth is around 149.6 Million Km. That means that the light from the sun to the earth would take a while for it to reach us.

We will determine the time it will take for the Sun's light to reach us using the speed equation:
Speed = Distance / Time
where
Time = Distance / Speed

T = D/S
T = (149,600,000,000 m) / (300,000,000 m/s)
T = 498.67 seconds or 8.31 minutes.

It takes the light from the sun 8.31 minutes to reach the earth. Or we could also say that the Image of the Sun takes 8.31 minutes for us to see it (WARNING: DO NOT LOOK AT THE SUN DIRECTLY!)

So how about something even farther? Let's try the nearest star from us: Alpha Centauri which is 4.367 LIGHT YEARS away.

Alpha Centauri

Note: A "Light year" is not a measurement of time but a measurement of the distance traveled by Light after 1 year.

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So that means that the image of Alpha Centauri takes 4.367 years to reach us here on earth. That delay is HUGE.

With our two examples so far we see the time delay of the images to reach us:

1. Sun - 8.31 minutes
2. Alpha Centauri - 4.367 years.

What does that time delay mean? It means that what you are seeing with your own two eyes are not the objects in the present time but an image of the object in the past long ago (8.31 minutes ago for the Sun and 4.367 years ago for Alpha Centauri)!

Just for fun let's try and see the distance of a nearby galaxy: The Andromeda Galaxy

Andromeda Galaxy is 2.537 Million Light Years away.

It takes 2.537 Million Years for the images of the Andromeda Galaxy to reach us.

This means that when we are looking up at the sky filled with stars and galaxies we are looking at an IMAGE that took millions or billions of years to reach our eyes. Even super advanced space telescopes experience this delay and are taking images of the past.

If there were aliens millions of light years away trying to observe us down here the images they would see would be the dinosaurs millions of years ago!

The reality is the stars we are seeing in the sky above is not the present stars today but the stars from millions or even billions of years ago...

Thanks for reading fellow Steemians! c",)

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