In fact, on earth, the speed of light is also beyond everything. Do you know how fast it is? Next, let’s learn about whether it can fly to the edge of the universe if it turns on the flashlight and shines it towards the sky for 1 second and then turn it off?

Everyone knows that Speed ​​of light is the first speed in the universe . In fact, on Earth , the speed of light is also an existence that surpasses everything . Do you know its speed is ?

The speed of light refers to the propagation speed of light or electromagnetic waves in a vacuum or medium

According to the refractive index of light in the air in the air is .0008. We can calculate the propagation speed of light in the air

99552816m/s.

Light is How to propagate ? Where can the light on the earth spread as far as to ? Can the light on the earth shine on into the universe ? Where is the edge of the universe ? Next, let’s learn about it. If you turn on the flashlight and illuminate it towards the sky for 1 second and then close it, can it fly to and the universe edge ?



Will they reach the end of the universe?

light propagation

In the same uniform medium, light can propagate along the straight line . When light encounters different and non-uniform media during the propagation process, refraction is generated. In fact, it is when light encounters blocking during its propagation. The light reflected by this hinder is what we see with the naked eye. At the same time, this hindrance will also absorb some of the photons into .



Hurgens-Fresnel Principle: An analysis method for studying wave propagation problems

Generally speaking, Light Once Other media , the phenomenon of curve propagation will occur. But when it passes through this medium, it will still propagate in the form of straight line . According to General Relativity , when light propagates near large-scale objects, it will be affected by the gravitational field of object, resulting in deflection of of the light propagation path.

Because the light propagation speed is extremely fast , the human eye cannot capture . The light we observe is actually all the light refracted from in the process of light propagation in .



Spatial time and space curves and gravitational deflection of light

• The essence of light

When we discuss whether light on the earth can be transmitted to Cosmic , we need to explore the essence of light . Scientists have studied its essence thousands of years ago. The statement about whether light is wave or particle has been debated until later, Einstein proposed that light has wave-particle duality .

, but this statement has not been recognized by everyone's . At the level of atom atom internally has nucleus and motion electron , the arrangement of these electrons is related to the distance of energy level , and the closer to the atomic nucleus , the smaller the electron energy .



1905 Einstein summarized the famous photoelectric effect

When electrons appear stimulated radiation and spontaneous radiation , it will move from low-energy orbit to high-energy orbit . In this process, needs to absorb or release a certain amount of energy of , which is the photon (light energy) that we can see.

So according to our current research, the formation of of light requires energy , but its does not require energy , but the light here can refer more to in the universe . Under the vacuum state of , the propagation of light does not require too much energy .



photons (essential particles that transmit electromagnetic interactions) Overview diagram

Our Line of sight is limited by certain . There is no way to see the propagation of light all the time, but it does not mean that it is completely absorbed in the process of propagation .

Can the light of the flashlight reach space

When the flashlight is turned on, the photons generated by belong to a kind of is stimulated radiation , and its light production will be affected by the energy transmitted by the switch .



stimulated radiation diagram

Theoretically, according to the propagation speed of light in the air , and the distance between the earth's surface and the universe, the light is reflected in some particles in the air h After tml2 becomes the light we see, there will be a large part of does not take 1 second to reach in the universe, and then can continue to spread in the vacuum to reach the edge of .

But this can only exist in Theory . In fact, the light emitted by the flashlight has no way to reach the edge of the universe, and even to reach the universe may be difficult for to reach .



Light that can never fly to the edge of the universe

• The light of the flashlight will be gradually absorbed and diffraction

We also mentioned earlier that during the propagation of light, the propagation direction will be changed because of encountering different media , and will even be absorbed by obstacles . From the surface of the earth to the universe, it seems that only requires air , but there is a large amount of dust in the air, and there is also a large amount of atmospheric molecules in the earth's atmospheric layer .

According to calculations, every cubic centimeter of in the surface atmosphere contains about .7 billion atmospheric molecules. When the photons pass through the atmosphere, they will be absorbed by these molecules and converted into . Although it will also absorb energy in this process, it will appear particularly weak in front of 's large number of molecules .



The vertical hierarchical structure diagram of the atmosphere

Although we mentioned earlier that under stimulated radiation , the photon will go from low energy field to high energy field , but in this state, it no longer has more energy . Then will fall back to the original energy level , and then will release a photon.

And this photon is no longer the original photon 's . Its 's advance direction has changed, which means it may not move towards the universe any longer.



Reflection and refraction of light

Here, except that, if these parts of are absorbed by , the photon will also be reflected and diffracted by a large number of , causing the propagation direction of light to change, and the propagation direction of will be transmitted from the original to linearly become to diverge in all directions .

If explained according to fluctuation , the light emitted by the flashlight shows obvious divergence . When the brighter the of light is, and the closer it is to the illumination object , the better the monochromaticity of light is, the better the monochromaticity of light, and vice versa, there will be obvious divergence. When we turn the flashlight towards the sky, we can see the divergence of light , which is the diffraction of light .



Different phenomenon of light

So when the light from the flashlight shines into the sky, the process of dissipation may faster than 1 second . It may have not touched the outermost layer of the atmosphere , and it has disappeared .

• If light comes to the universe

If we put aside the in the atmosphere different media , so that some photons can come to the universe smoothly, can we reach the edge of the universe ? In fact, is also not feasible .



Concept of seeing the beam of light in the universe

We say that light propagates the fastest under the vacuum state of , but in the universe is not completely in the vacuum , there are also a large number of particles in the universe . When the photons come to the universe, they still cannot escape colliding with these particles , is absorbed and converted into energy . At this time, the photons are still very likely to be able to continue to propagate .

If it luckily avoids particle , what will continue to spread? Here we have to mention cosmic expansion theory . In the Big Bang cosmology, we learned that the universe exploded from a dense starting point of , and based on the universe redshift phenomenon , we also observed that the universe is still in expansion .



galaxy redshift phenomenon observed through telescope yanshitu

Until now, we cannot know The edge of the universe where is it. In the process of getting away from us, light will also expand as the universe becomes farther and farther away from us . At this time, the wavelength of light will experience Doppler effect . That is to say, when the light source is far away from us, will reduce the frequency and stretch the wavelength .

When the wavelength is stretched, it will form redshift , which is finally called infrared or radio wave , but we cannot observe these with naked eyes . Even if we use some electronic device for observation, it is difficult to know where this photon comes from, where is going, and whether it is the light emitted by our flashlight .



Universe redshift phenomenon demonstration diagram

Moreover, as for the photons emitted by the flashlight, it is also a question whether we can observe to .Currently, what we can observe with telescopes include radio, infrared, ultraviolet, X ray and gamma ray . The prerequisite for observing them is that generates enough energy to be sufficient to observe .

For example, the reason why we can observe the celestial body of 0 million light years away is because it emits photons , and there are also a large number of X rays or gamma rays , etc. And even if the light that flashlight can be emitted by luck, it can be ignored by and .



739 strong gamma ray sources in the universe - the light emitted by the radiant variant

The edge of the universe is far away from

And we have almost no way to talk about The edge of the universe exactly where is located, because the universe has been in the expansion state . When the singularity of exploded in the early days, the speed of the universe expanded even exceeded the speed of light . The most distant light of we have observed now, has passed more than 110 billion light years of . This shows that the photons emitted by large-mass star bodies have a long lifespan.

But according to modern universe model , the diameter of the universe we can observe reaches 3 billion light years . The center of this diameter is Earth . How can the light of the flashlight pass through a long time to touch the edge of the universe ?



Symbol Explosion Generation of Universe Schematic

Not to mention that this universe is still expanding in . Even now, we cannot guarantee that those lights with super-energy can continue to spread in the universe of under the state of not completely vacuum. Then the light of the flashlight shot from the earth is even more like and cannot reach the edge of the universe.

In the universe we are in now, it can be said that Where we stand , Wherever we stand , The space of the universe is . And the farthest place in the universe we finally arrived at , , we can also say that it is the edge of the universe .



Light concept map in the universe

But we all know that The vastness of the universe is hard to imagine . There are many phenomena and facts in it. Our science has not yet come up with the accurate answer to , so this is not something that can be done by a beam of light .