EXPANDING UNIVERSE

      Hello all and welcome to my Blogspot EVERYTHING ASTRONOMICAL. In this blog, let's discuss some of the ideas about expanding the universe and Hubble's contributions.

Expanding Universe:

    We are going to talk about the evidence that shows that the space is expanding, getting bigger, which sounds pretty ridiculous😳. However, that's not an unsolved mystery, we are actually pretty sure that space is expanding, perhaps not quite 100% sure, but certainly 95% sure😌.

( Expansion of the Universe )

    But then the real mystery will come into play, which is... okay so let's say that space is expanding, where is it expanding from? Was there some sort of Big Bang at the beginning? And if so, where did the Big Bang come from?🤔 ( Leave your thoughts in the comment, let's discuss.)

    The description of the expansion of the universe is called the Big Bang Theory. The Big Bang explains the evolution of the universe after its beginning. 13.82 billion years later, we find ourselves here on the Earth learning about Black Holes. 

    Okay, let's switch to Hubble's contribution now.

Hubble's Law:

    In 1929, Hubble continue the observations in Doppler shift and found a relationship between the distance and the redshift of galaxies. Hubble found that galaxies that are outside of our group of galaxies have the light that is redshifted.

    Not only is the light redshifted, but he also saw that the further away the galaxy is from us, the larger the change in wavelength or the larger the redshift.

    If the change in wavelength is interpreted as a Doppler shift due to the motion, then Hubble's observations suggest that the galaxies appear to move away from us. Galaxies that are further away from us are moving away from us at a fastest speed.

    The modern interpretation of Hubble's observations is that the universe is expanding, which makes it look like galaxies are moving away from us. Clear!

    So the further away you go, the faster the motion of the celestial objects. This is known as the Hubble law and it is parameterised as a velocity that is proportional to a constant called Hubble's constant, which is about 70(km/s)/Mpc.

Hubble's law formula:

                      v = Ho.D

    where v is recessional velocity, Ho is Hubble's constant and D is the proper distance to a galaxy or any other celestial body.

( Hubble Diagram )

   

     This graph clearly depicts the expansion of the universe and the Hubble value to be constant since the slope is a linear one. I still have some thoughts that how this value to be constant?🤔 Since each layer in the universe will expand at its own pace and how is the expansion rate to be constant?🤷( Leave your valuable thoughts. )  And one more thing, you can't compare this expansion with the speed of light.

    I hope you have a good idea about this universe expansion in general.

    I think it's enough to discuss some basic ideas, let's get into our topic of discussion Black Holes in my successive blogs.