The Teeny Tiny US!

In this post, you are going to realize how massive a light-year is and how negligible we are! For someone who does not have a physics background, you may think that light-year is something to do with the time derivative due to the representation of ‘year’ in the word. But it isn’t. Light-year represents the distance. The numbers dealt in Cosmological level are pretty big. When representing distance in meters, Kilometers or miles, it goes like 10 digits and it’s hard to enter the whole value. For example: distance from Earth to Jupiter is 783.13 million km or 782,643,029 km or 7,82,64,30,29,000 m. Due to this trouble, astronomers thought that they must do the reduction and have an equivalent value.

We all know that the speed of light is constant throughout the universe. So, astronomers decided to use light as a parameter and measured distance for large scales using light-years. Basically, light-year is nothing but the distance of light travels through space in one year (1 Light-year = ‎9.4607×10¹⁵ m). Interestingly, light-second, light-minute or even light-day can be represented in distance.

For the planets in solar system, refer the below table to know the distance from the Sun to the respective planet in terms of Light travel time

Planet	Light Time Travel
Mercury	3.3 Light-minutes
Venus	6.1 Light-minutes
Earth	8.5 Light-minutes
Mars	12.9 Light-minutes
Jupiter	43.2 Light-minutes
Saturn	1.4 Light-hours
Uranus	2.7 Light-hours
Neptune	4.1 Light-hours

Also, the center of our galaxy is about 27,000 light-years away. Whereas, Andromeda galaxy (the nearest spiral galaxy to ours) is about 2.5 million light-years away.

Here, on Earth, you see objects because the light gets reflected by the object so that it is detectable to our naked eyes. But that’s not the case when it comes with larger scales. Every stellar object emits its own Electromagnetic radiation (i.e.) light. In such cases, the object may be several thousand light-years or even a light-hour away. But the thing is light takes time to reach us! So, if you are observing any stellar object which is 1 light-year away from Earth, you see it as it appeared exactly one year ago. You encounter that object’s past conditions which may or may not be similar to its present condition. The most distant stellar object you see, is also your oldest view of the universe, occurring just after the Big Bang. It is cool, isn’t it?

There are other units used to measure distance in outer space such as Astronomical units(AU), parsecs(pc), which again uses light as the parameter.

1 AU = 1.495978707×10¹¹ m or 1.5813×10⁻⁵ ly

1 pc = 3.26156 ly

After realizing how small we are in our solar system, in our galaxy or in this universe, the hard-true fact is that we are tiny. Yet, we matter! Everything around us matters! But it is important to know that we are negligible when compared to this Universe!