The riddle of DARK ENERGY!

Hi,
today I will write about dark energy since last time I briefly covered the dark matter. The dark energy is even more unknown than the dark matter, let’s see why.


As I said before, there is about 70% of dark energy in the Universe of all the energy that there is, rest belongs to dark matter and tiny bit to normal matter.

Dark energy has to do a lot with expansion of Universe which was find out last century by Edwin Hubble. He found out that the Universe is expanding and right now we even know that the rate of expanding even increases (The Big Rip scenario).

Why? Because there is something called dark energy and we know that it works kind of like “anti-gravity” this could be misleading since the gravity is still there so it is also said that it has “negative” pressure.

Dark energy is everywhere at the same amount and as the space is expanding there is more of it created. This does not violate conservation of energy since the force of gravity decreases at the same time with the distance increasing. I guess that this is why the expansion increases.

There are four theories which I found about the dark energy, the first one is that dark energy is not a thing but rather property of empty space and empty space is expanding and as the expansion increases so does the rate.

Second idea is the idea of cosmological constant which was made by Einstein. At the start it was constant which would be zero so that space would be static but as Hubble found out Universe is expanding so the cosmological constant, which is kind of property of space must be higher than zero. Now lot of cosmologists are trying to measure this constant, this is a big problem since when we try to calculate it, it goes with orders of magnitude away from what we can observe and it is simply wrong.

Or also virtual particles popping in and out of existence in space could give energy to this dark energy.

Simply we do not know much about it but we know that it must exist in some kind of form.

Dragallur

 

Advertisements

How it started, featuring Big Bang!

Hi,
when you read the title of this post it is pretty clear that I am going to write about Big Bang, I already wrote about the ends of the Universe but it feels as lot of people are interested in the beginning and there are some misconceptions.
For example even the title is little bit wrong since you could assume from it that Big Bang was the start of everything..


So I will try to explain Big Bang and what happened right after and I want to start with first big misconception.
People think that Big Bang was explosion, nope it was not. It is thought that Universe expanded into space but actually Universe is already everything and it kind of expands into itself, if it makes sense.

BigBangIsExpansionOn the picture above you can see the example of expansion where space expanded not the things inside but the fabric itself. The space in the grid increased while nothing happened to the objects except that they are further apart. This is what is happening all the time and even if the Universe was infinite it could get bigger, kind of, because everything is going away from the rest of the stuff and NOTHING can be the center of the Universe. There was no explosion.
For the rest of the post I will follow the picture on the left.

On the bottom of the picture is the start of the big bang. This is outside of the graph because we are not able to investigate it using the laws we know now. This is until Planck time passed (10^-43 seconds). After Planck epoch which is big unknown, the time of grand unification came. This is time with extremely high energies involved and it is assumed that 3 fundamental forces are working as one at this time: electromagnetism, weak and strong nuclear force. This is extremely important but we are not able to reach such energies even in particle accelerators while it could help us a lot with Theory of Everything.

Few really really short moment later strong force separated and started to work alone. This took some really long time before all the forces separated to the state we know today. This is one picosecond after big bang. Then quarks became grouping together into hadrons. Those are particles with zero “color” charge like neutron or proton.
Some time later finally deuterium is created and through big bang nucleosynthesis some heavier elements like lithium, beryllium and helium too.

Then it takes really a long time before everything calms down so that first stars and then galaxies form.

Some time I will probably return to background radiation.

At the beginning I said that you can not really say that big bang was the start of everything since there are some theories like big bounce.

Dragallur

1st picture
2nd picture

What could happen to our Universe: Big Bounce

Hi,
with little break from Solar System I am returning to last post about end of our Universe. This time it is very optimistic, but we will die anyway..

Right now the Universe is expanding, it is expanding in high speeds but this theory is assuming that this process due to decreased amount of dark energy reverses at one point and everything will start to shrink back. This would heat Universe over time. About 100,000 years before big crunch space would be hotter than surface of stars which would make them cooked from outside (FUN).

Then all matter would fall into black holes and all of those black holes would fall into each other so that final singularity would be created.

Well then it could start all over again, big bang, zero expansion and big crunch. This scenario also assumes that Universe is going through infinite cycles of banging and crunching. While this is most optimistic, in the new Universe would be nothing from the one before.
Measuring of expansion of Universe does not give much points to big crunch because now it seams that expansion is speeding up. Scientists are not yet able to know why is this happening Big Bounce is still an option.

Dragallur

PS: I just lost the game… Here is post about heat death. And here about big rip.

What could happen to our Universe: The Big Rip

Hello,
before I continue with Apollo missions I will write something short about Space, this time what will happen to it.

There are three main hypothesis and in this post I will write about The Big Rip (TBR).t_{rip} - t_{0} \approx \frac{2}{3|1+w|H_0\sqrt{1-\Omega_m}}

Firstly I heard about it in the TV but it was not explained very well so I had to search on internet… i greatly recommend video by Kurzgesagt (its in english) and it summarizes perfectly what next posts will be about.

So TBR is theory about end of Universe  For the first time it was published in 2003.

It bases on the expansion of Universe which would increase over time so that observable Universe would shrink into area smaller than anything: atoms, quarks or even hypothethical preons so that no interaction would be possible. Everything would be torn apart because it would not be gravitationaly bounded.

This bases on thing called phantom energy (kind of dark energy) which would have “w” smaller than -1 (ratio between dark energy pressure and energy density).

In aprox. 22 billions years there would be nothing like Universe.

Dragallur