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I am a low-level teacher with an amateur passion for the advancement of modern society. My specialty is physics but all forms of the advancement of knowledge are something I consider extremely important.

Friday, January 21, 2011

Dark Matter or, "we're pretty sure it's there"

First off, i'd like to thank everyone reading this page for their encouraging comments, I just hit 50 followers recently and I hope that the information I try to break apart here is of some use to you. If it's not, or if you interests lie in a different direction please let me know! I am always open to talking about specific topics of interest, if there is anything you feel you would like me to elaborate on or attempt to convey in an understandable manner just leave me a comment and ill do my best to accomodate.

Second, Comcast sucks, I don't know about the rest of you but I have always had problems with them trying to stayconnected when I need to, otherwise this would have gone up much earlier today.

Today I want to talk a little more about this stuff that scientists have dubbed "dark matter" and I think the best place to start is why we would even think it's there in the first place. I mentioned last time about how astronomers use gravity to notice something that should be there when you can't detect it normalls, but the manner in which they do that is much more refined. Over extremely great distances everything is affected by gravity, even light,  so one of the primary methods for detecting this dark matter is known as "gravitational lensing". When light from a very bright object in the sky (even brighter than most individual galaxies we are talking about exploding stars and large clusters of galaxies here) is distorted (or bent or however you want to say it) into arcs or curves then it's possible to measure the angle of this distortion and find out how large this invisible object is (or at least it's mass, which doesnt really tell us alot about it's physical size. You can see an example of lensing below.

There are a few other methods for detecting the presence of dark matter in the sky, including looking at the data provided for the CMBR (see earlier post) however let's talk about what we actually know about this stuff, this matter that we can't see. Most of the information about what dark matter is actually composed of is speculative (or nobody really knows but it's fun to make stuff up) and most of them revolve around large mass objects that we wouldn't be able to see normally: black holes, small faint stars, and some kinds of gas are all thought to be contributors.

Some have postulated that there are at least three forms of dark matter, cold warm and hot, however these terms deal more with their speeds than their temperature. Cold dark matter is the stuff that travels at speed we are used to, known as "classical" speeds. Warm moves at nearly the speed of light and so faces interaction with the doppler effect mentioned in an earlier post. Hot dark matter is thought to move at speeds extremely close to the speed of light, so close most people would just round up. The cold dark matter represents the greatest interest to modern scientists because of it's relatively "slow" speeds it would be a large factor in how galxies and their clusters were formed towards the beginning of the universe.

In any case attemting to directly detect dark matter is pretty frustrating. Most use one or two technologies to detect this stuff, and have to be situated deep within the earth to protect it from interference from all of the other radiation raining down on our planet at any given moment. One popular method is a detector so cold it reaches down near something dubbed "absoulte zero" if we are talking about celcius it's around -273, and detect the slight variation in temperatures. Needless to say keeping a detector that cold all the time is pretty expensive.

To summarize, dark matter is simply a term that reflects the modern scientific world's ignorance of what nearly 25% of all the detectable material in the universe is composed of. Detectable only through indirect methods, it will be some time before our techniques are advanced enough to really understand what's going on out there.

Next time I think we will go into the speed of light and why it's so important that nothing can ever pass it (think of it like a universal speed limit).

Thursday, January 20, 2011

Cosmological Recycling #3

So what can we piece together from all of this stuff. There is a somewhat uniform temperature across the entire universe (the CMBR), and as far as distant stars are concerned they are moving away rather rapidly (redshift). This leads us to believe that at some point in time everything was much closer together at a much higher temperature. How close? So close that the entire universe would exist as a "singularity" (a single point in space). How much of a higher temperature? So hot that even electrons could not stay attached to atoms, even hotter still that the parts that make up a neutron or a proton, known as quarks, could not stay together, and everything sort of floated around in a "soup". You can see an example of inflation below.

When scientists refer to this period of time, very shortly after this "singularity" began to expand (this is what's known as the big bang), it is called "inflation", or the very rapid expansion of all the material we see around us today, everything. The most important evidence of this occurring was detailed here.

Let's now discuss some of the problems with this theory of how everything began. Probably the most visible and least solvable problem is the existence of "dark matter" and "dark energy" now they didnt give this stuff these names because they are evil, just that they are impossible for us to see directly. If we can't see it, then how do we know it exists? Imgaine you are looking at our solar system, with the sun in the middle and 8 planets (I know it should be 9, astronomers are a crazy bunch) revolving around it in harmony like normal. Now imagine you cant see the sun, you still see all these planets orbiting around the sun, but you cant see the big thing in the middle that is causing them to orbit that way. That is the idea behind dark matter, although not as specific as that. Looking for actual dark matter is much more difficult, since you can only rely on what you know should be there, instead of what actually is.

Dark energy works in much the same way. Since every star we look at is redshifted in some manner, and the further away it is the more redshifted it looks there is evidence that instead of slowing down (as you might expect at the end of a large explosion) all these stars are actually moving faster. Thus there must be some kind of extra energy, dubbed "dark energy" with a negative pressure. To understand what I mean by negative pressure think about being in an airplane cabin. If someone were to open one of the airplane doors while in flight all of the easily breathable air would escape, since the air is so thin while you are flying. Then we say the air inside the cabin is pressurized, and presents a positive pressure to the outside, it is trying to force its way out. Conversely the air outisde has a negative pressure, it is trying to suck up all of the air from the inside. The same is true for this "dark energy" as it causes the universes' expansion to accelerate.

Next time ill talk further on what people believe dark energy and dark matter to be, and why understanding these forces we cannot see may be the most important step to understanding the formation of our universe.

Wednesday, January 19, 2011

Redshift and you, Dopplers' legacy

I have mentioned recently a little about what the CMBR is and why scientists think its so important to understanding the formation of our universe. it's easy to wonder though, just because you can see a relatively uniform (at least in the space between galaxies) wash of microwaves, how does that indicate some kind of formative explosion?

To undertsand that we have to understand something called redshift.

Ever stand near a moving train or car while some sort of horn is blowing and noticed that it was a little higher pitch before it passed you, and lower afterwards? Or perhaps you saw a jet plane pass over you before you heard it, and when you did it was really loud? The reason for this occurence is known as the Doppler effect (I just like to call it Doppler Shift). To undertstand what that is first you have to know a little about how sound works.

Imagine a perfect peaceful pond, and you drop a single stone into it such as the picture above. It creates ripples that move outwards, the same thing happens every time you hear a sound. From the tapping of your fingers on a keyboard, to merely the sound of your voice all sound ripple outwards like that.

Now, we call those ripples waves, and they only stay circular like that as long as nothing is moving. In the case of a moving car or train, or even if you are talking to someone while walking these sound waves can "bend" a little. Right in front of the car or train or whatever is making noise these waves can "bunch up" and get compressed, because of this you hear it at a higher pitch than normal. And behind the source of this noise the waves get "stretched out" and you hear them at a lower pitch. This happens more and more as you approach the speed of whatever it is we are talking about (in this case the speed of sound).

Anyway, thats the idea behind doppler shift, in case you were wondering where I was going with this, many different things are expressed as these waves not just sound. Earthquakes, waves in water, and most importantly light are all different kinds of waves. All that matters is what they move through (sound through air, waves in water, earthquakes in land) however light is special, as of the current day nobody understand exactly what it is that light moves through, or if it has to move through anything at all since it can exist in a perfect vaccuum.

Everything I just mentioned applies to light as well as sound, however light is much less noticable, and it only really matters when you start approaching the speed of light (so very incredibly fast that nothing we have created even comes close, breaking the speed of sound was hard enough). Being able to notice these small distortions in light is the basis of why physicists think the universe was created in a large explosion, or "big bang".

To relate, just like the sound waves bunch up in the direction the car is moving, if you were to take a lightbulb and move it really fast the light waves would bunch up too, and you would see the light as "blueshifted", contrary to that behind the lightbulb you would see light that has been stretched out or "redshifted".

So here is the deal, and kinda the point of this whole thing. When an astronomer analyzes light coming from a star thats really far away, it looks as if it is redshifted, that is the star he is looking at is moving away from us at some speed based on just how red it is. The thing is, no matter what star you are looking at the further away it is the more redshifted it looks. This leads scientists to believe that the universe is expanding in every direction at all times, thus that a large "explosion" was where the universe began.

To summarize stars that are very distant are "redshifted" or moving away quickly. This combined with the CMBR are the basis for the "big bang theory", and its why scientsts tell you they can figure out just how long the universe has been around, because if we know how fast everything is moving away we can figure out how long its been moving like that.

Next time ill wrap up Cosmological Recycling and explain why these scientists may have been mistaken, as always the facts dont neccecarily add up to the conclusions we want to believe.

Cosmological Recycling #2

Last time I talked a little bit about the CMBR, which is one of the major arguments for the big bang theory (not the show mind you), but how can scientists be sure that there is this uniform level of energy all around our universe, even in the spaces between galaxies?

Once the beginnings of the CMBR were detected there was a great push to create a satellite with the capability of measuring it more completely. Why would they use a satellite? It just so happens that as the sky above us protects us from harmful radiation both from our star (the sun) it also acts like a filter, removing some kinds of light (or radiation) that we use to "see" in space. In the case of the CMBR we want to see microwave radiation (yes the kind in your kitchen, just not as energetic).

So NASA got together with a few other scientists and lauched what is known as the Wilkinson Microwave Anisotropy Probe (lets just call it the WMAP, everyone else does). This probe has been running since 2001 and returning large amounts of microwave data as it orbits our planet earth. Over this time it has measured the temperatures (or concentrations) of the CMBR all across the visible sky. You can see a diagram of the WMAP below.

In light of this data a whole field of physics known as Cosmology became much more viable. Now Cosmology isnt what your hairdresser went to at night school or something, Cosmology is the study of the biggest concepts. The formation of the universe, the structure of billions of galaxies across the current universe, and the prediction of what will happen when our universe begins to run its course (if it can ever run its course at all, really). I like to think of Cosmology as science of philosophy, and the people who will tell you all about how they believe the universe began are known as Cosmologists.

So really, the CMBR, what scientists have believed to be the "echo" of the very beginning of our universe, is the largest form of basis for cosmologists to tell you how the universe began. The data they use for this comes from the WMAP, a probe that only ready microwave radiation. There are a few other things we need to talk about, before we can determine if these scientists really know what they are talking about.

Next time in the Laymans' Laboratory, redshift, and why everyone thinks the universe was created in an explosion.

Tuesday, January 18, 2011

Cosmological Recycling

This will be a multi-part post,

When people get together to discuss how scientists believe the universe began the most powerful example is something called the Cosmic Microwave Background Radiation (dubbed the CMBR). Many scientists believe the CMBR is the leftover "echo" of the extreme temperatures that occured towards the beginning of the universe. What it really is, as far as most of us are concerned, is a very slight amount of heat (or just energy, however you want to think about it) that exists everywhere in the noticable universe. The first two images at the top of this article refer to the time periods of expansion as the universe began to cool, I will discuss these at greater length later. Whats most important to us is the third picutre, that is supposed to be a picture of the entire viewable universe done in the levels of temperature. Blue areas represent the great expanse between galactic clusters (large groups of galaxies) and the warmer areas represent the heat generated by those clusters.

So to summarize all this stuff,
There is a level of heat or energy that exists everywhere in the universe, even in the space between stars and galaxies, and many believe that this is the leftover radiation (or heat/energy) from the expansion of the universe. It is hard to deny the reality of the CMBR but it may not mean quite as much as modern scientists believe, more on that next time in the Laymans' Laboratory.


Hello there,

I have created this website to catalouge what i believe are important technological advances in recent history (ideally within the last 5 years) and present them in such a fashion that can be understood by the majority of readers with little to no technical background. If my explanations are too complex please feel free to comment as my intent is to facilitate understanding and not increase confusion. In addition if you feel there is an important scientific or technological breakthrough that I have neglected please comment on that as well.