# Observational cosmology and the acceleration of the universe

One of the facts that interest much physicists, especially astrophysicists and theoretical physicists is the Big Bang, Of all those who study could have before, there is now and may have after this event so important in our universe, observational cosmologists are special beings who study our universe, if history and evolution through the observation of it.

All because these people have played a major role for the problems they have to face and so, from here, wish to pay tribute.

## Before starting

A clause. I do not usually put equations because I see very cumbersome and for which of these items and do not want to lose your attention, but remember that you can ask me and I explayare with all the enthusiasm. In addition, I remind you that I am a little “grand’pa” and I digress, something I hope you make more interesting the article.

## Let’s begin

Problems than other physical not found than the observational cosmologist it’s that can not repeat the experiment, can not prepare the universe so you can re do the experiment every time you want to debug, either calculation or measurement what they It becomes a brave, at the same morons, to, have often rely on their intuition.

A clear example of what has been your intuition (and mathematics) was the discovery of dark energy (and dark matter that our colleague Arturo has spoken to us and I’ll dig a little deeper).

The most serious problem they face is, as I said, whether the data are real, casual or a mere measurement problem. How do you know that are casual ?. Let’s take an example to reverse a fact that is a coincidence and is not a standard and therefore is the result of chance.

It is no coincidence that the Sun and Moon are located too far away from Earth that today, in an eclipse, the moon cover the Sun revealing exactly his crown (and helping study). Come on, that there is no law that makes satellites are at that distance and if mere chance (lucky) that on Earth is so. And more knowing that the moon moves away from the Earth because it loses energy as it needs to, on Earth, creating tides and this … is an energy cost. Giving greater chance that, at the time we live have such a great chance.

As I said, observational cosmologists are dedicated to see the development and history of our universe and among other things they do thanks to see the expansion of this. How do ?, because through background radiation and measuring the distance of a standard, the explosion of a Type Ia supernova which it is known that the light emitted is always the same.

The cosmic microwave background, which certainly have heard and seen the photo and no one will explain it (which I am going to do now), comes from the hot universe, when it was a ball of fat plasma of about 4000 degrees Celsius. And, before that, to be so dense universe, photons and certain wavelengths were unable to escape the interior of this as everything it was so tight there. An example is trying to get out of a subway car, part of the center in rush hour to leave, salts, but you spend time with people bumping into you accomplish your goal to. As the universe after the Big Bang was the same way, energy photons and was unable to leave the hitting he was so tight until expanded and cooled enough to leave. Exactly the same happens with photons, the light and the sun’s interior where photons created in the core, take an average of 1000 years to reach the surface.

At that time, the severity of that mass had not formed anything and therefore the distribution of matter was “more or less uniform,” emphasizing the more or less. This more or less, with the expansion culminated in different areas of pressures and densities are those that have created the galaxies.

These “fluctuations” can still be measured. And you say How and why?. I’ll get a bit chive and I’ll leave the tangent, but it helps the explanation. Something very important and that even is unknown, is the topology of the universe, which is has. We do not know how it really is but we know that the universe is homogeneous, we, that is equal on all sides. It is known that nothing of what is inside can escape from it, ie, it has no edges, you can shoot “straight” all you want that you will not leave the universe by far to walk, as in Earth where you can walk on its surface indefinitely not you going to leave it as is spherical topology (physical joke that we had in my race times: run run torcuaz that the topology is spherical!). It can be a sphere, flat, slightly curved (so that if you get to the edge follow below) or a tape Meobius and we ant walking over.

Then the energy (radiation) that has escaped from the Big Bang still be measured as this turning even the universe, like the light (and therefore measure the distance of a star and its position has its complication not knowing whether we are seeing directly or bounced light that has traveled around the universe … curious right?).

Anyway, Ralph Alpher and Robert Herman in 1947 announced that, precisely, must, for the Big Bang exist electromagnetic radiation (microwave) floating around the universe and calculated with great precision (5 Kelvin) but it was not until 1965 Arno Penzias and Robert Wilson who had the technology to measure showing the dispersion energy quotas Planck formula was met hollow body allowing consider the universe as what it is, a hollow body closed on itself.

The cosmic background radiation as whole, depends on the frequency, ie the temperature of the microwave background (remember that use either phrase for the same) depends on the temperature of thermal radiation.

So anisotropies observed in the background radiation give us much information about the early days of the universe, such as the like, the way they release radiation when the universe cooled, the like gravity I think “lumps “in the density of the soup after the Big Bang, and the size, this period of rapid expansion was short, so you can see that the universe is expanding or expanded at different speeds, sometimes faster times slower and now plays another fast stage.

And thanks to Einstein’s equations (which has more apart from the famous relativity and energy) can make models of the distribution of matter and make models as it was, it is and will be the expansion of the universe.

## Expansion of the universe

And why the universe expands?. Well, here I become a bit chive grandfather so calm. As I think I have had the string theory, space itself, consists of strings (and not go into the simplification of loop quantum gravity) where space grows the more strings are created. The space itself is like a sponge and admits in a certain amount of energy. If more energy than will fit in the space (remember, it’s like a sponge you stick more water) it grows. And if the sponge, could grow “indefinitely” would our universe. That is, in the Big Bang there was so much energy that does not fit into the space that housed so the logical consequence is an expansion.

Turning to background radiation, scattering spectrum, as shown has a maximum (and minimum). What is this?. The curvature of space because, as I explained Arturo talking about gravitational lensing, gravity bends anything, even the waves of radiation (light it is, remember).

The fact is curious is that the curvature of space is not always constant, can be positive, negative or neutral (a plane) but our scale, space has virtually no curvature is flat. With what, or the universe is very large (and like on Earth we do not see the curvature of the same) or topology is not spherical.

The good image that I have set is that the peaks appear to contradict with the amount of matter that exists except that there is a type of unknown energy that does not cause serious and therefore the “lumps” but it is important for the curvature gravitational it generates … and what’s that kind of energy? … dark energy. This means that the peaks in the spectrum of background radiation gives us the idea of ​​the existence of dark energy by the curvature that stuff.

But not only that, the mass can not be attributed to dark energy is much greater than the matter we can see, which, besides the dark energy there is something else there, other energy, dark matter.

That is, that the image of background radiation have drawn conclusions sea of ​​interesting.

Now, for the last time, it is assumed that dark matter is a vibration of strings (string theory, remember) determined that vibrate so little that makes them impossible to see and to measure directly (for now, since we have technology for the vibration of a string … or to see it) and it does not emit radiation (or not enough to capture it), but thanks to certain observations as the polarization of the background radiation we know that not only is there but It allows us to see its gravitational effects to polarize the background radiation. This also helped the boys LIGO, famous for having detected gravitational waves to think through their detectors can be drawn ideas on the intensity of gravitational waves in ancient times (Big Bang, remember) and to even grasp, measure them and know how to run the universe in those days.

And if you come here reading, you are a brave and you deserve all respect and apologies for such “tostón” (spanish word from something pest) you’ve swallowed you.

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