Can Light from Outside the Hubble Sphere be Observed?(허블 지름)

- from research in 10/09/29 -

 

What is the Hubble Sphere?

Currently, the universe is known to be expanding at an increasing rate. It means that the farther away from us(observer), the faster it expands. The universe is expanding at about 70 killometers per second per megaparsec (2.2685455 × 10-18 hertz). A megaparsec is an incredibly long amount of distance, and is about 3.085677581E+24 (or 3.085677581 X (10^24)) meters. A galaxy 1 megaparsec from earth moves at 70km/s away from us, and a galaxy twic as far away moves in a speed twice faster. At some point, space begins to recline away faster than the speed of light. This imaginary boundery is called the Hubble Sphere.

Hubble Volume - https://en.wikipedia.org/wiki/Hubble_volume

How can space move faster than the speed of light?

According to Einstain, everything within space cannot move at a speed faster than light. Then how does something like the hubble sphere even exist? In this case, not an object in space but the space itself is moving. As a result, at some point, it can exceed the speed of light and not break Einstein's rule.

 

The Answer?

It is possible to observe the light emitted from a celestial body from outside the hubble sphere, although it may take some time to observe light that is emitted outside the hubble sphere right now. Just like the universe expands, the hubble sphere expands too. Imagine making a lot of balls collide in one spot, and see how it spreads out after the collision. The boundery in which the balls are moving at a speed will move away from the collision point. Light in the universe that is headed towards the earth will move slower than the expanding universe, finally in the hubble sphere at some point. After that, though it will take a long time, the light will be able to reach the earth.