On Earth, people often measure the length of distance in meters or kilometers, because the diameter of the Earth is only 12756 kilometers, which is enough to use this distance unit, but once we go into space, we can no longer use it.
Because the universe is so vast, the distance between celestial bodies and celestial bodies can no longer be measured in meters or kilometers on Earth, thus deriving a longer unit of length of light years to represent the distance between celestial bodies! For example, how many light-years away is a certain star or galaxy from Earth.
So what is the concept of a light-year, how long is it, and how long does it take for a person to walk? Today we're going to talk about light years!
A light-year, taken literally, may be mistaken for a unit of time, although he carries the word "New Year". However, it is a unit of length, that is, the distance at which light travels in a vacuum for a year.
We know that the speed of light is the fastest speed of matter in the universe, any object with stationary mass can not reach or surpass him, and in any inertial reference frame will remain the same, about 300,000 kilometers per second, only one second can circle the earth 7.5 times, so the light-year unit can let us better understand the distance of celestial bodies in the universe, but also simplified a lot.
If a light-year is converted into kilometers, then the speed of light can be multiplied by a year's time to obtain a distance of one light-year, and a light-year is 9.46 trillion kilometers.
How long is 94,600 kilometers? Many people may not have any concept
We take the Voyager I launched by the United States in 1977 as the farthest artificial probe for mankind to fly, it has been flying in the universe for more than 40 years since the last century, accelerated by the planetary gravitational slingshot effect, and is currently flying at a speed of 17 kilometers per second to the outside of the solar system, and it is now about 22.5 billion kilometers away from the Earth, which is only about 20 light hours or so if he is converted into light years, or even less than one light day.
This means that even a traveler who flies so fast will take 17,600 years to cross 1 light-year. So how long does it take to walk a light-year at the speed of a person?
Generally speaking, most people have a stride length of about 1 meter, about 4 to 5 kilometers per hour, if a person does not eat, drink or rest, and continues to walk, then it can be calculated that walking for 1 light year will take about 216 million years. If you can maintain bolt 100 meters speed all the time, it will take 65 million years to run a light-year. You can imagine how long a light-year can be
Combining the above data, we can see that a light-year is far enough for human beings, but in fact, it is relative to the large scale of the universe, a light-year is incomparably small, in fact, a light-year is only the radius of our solar system, and above the solar system there is our Milky Way, which has a diameter of up to 160,000 light-years
And above the Milky Way there are larger local and superclusters, as well as known observable universe diameters, according to current data, our universe is estimated to be about 93 billion light years long, which means that even a beam of light travels through it, it will take 93 billion years!