Science

Why a look at the night sky is a glimpse of the past

The universe and its whims are wondrous and often beyond our perception of what is and what isn’t. 

The night sky is simply a beautiful sight to behold. Glittering with uncountable stars with the darkest backdrop of the vast space of the universe – the night sky serves as a reminder of where we stand in the vastness of the cosmos. Ours is a universe so vast that the fastest entity known to us takes millions of years just to reach us and then fly along its own path.

Light: The teller of a billion stories

Our understanding of the universe is majorly based on this one entity. The fastest one in the universe. We call it light. How light came into existence in the first place is in itself an enigma. But howsoever it came, its radiation showed us the picture of the entire universe at once.

Universe’s Self Portrait: The Cosmic Microwave Background Radiation

After the advent of radio astronomy, scientists picked up some strange signal noise emanating from all directions across the universe. They picked up this signal and built a model of the universe with it. And it was called the CMB (cosmic microwave background) radiation.

This radiation pans out across the universe and leads us to believe that this place we live in is quite the well-distributed symmetric place. But this is about the light that we do not see. What about the one we do?

What’s in the light: What we stare at in the night sky

There in the night sky, we see a billion lights. If the skies are clear and the places are too, that’s the captivating sight we witness. Light – irrespective of its energy or frequency, always moves at a constant speed of 299,792,458 m/s. And the universe is so large (at least the part we can observe) that it’ll take the fastest entity, light, about 93 billion years to travel across all that space.

The light we see: The light takes several years to reach us – hence, a glimpse of what was, not what is

So, every star which you stare at in the sky does not presently look the way you observe it to be. The truth is that it used to look that way some years back because the light which you see now took all that time to travel from there to your eyes. Even our sun which you see in the day is not the image of our sun at the moment. It’s a stare at 8-minutes into the past.

In fact, some stars which you look at might’ve disappeared already.

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