|
Italy12246 Posts
I've wanted to write a blog about astrophysics for a while, but for some reason i've gotten around doing it only now.
Today is actually a very important day for us astronomers and astrophysicsts: it's the 25th birthday of the Hubble Space Telescope, which is one of the most awesome things humanity has ever built. 25 years after its launch, 30 years after its construction, and 38 years after its original proposal, it is still one of the most powerful and versatile telescopes we have; even new, state of the art ground-based observatories like VLT and Keck have a hard time matching its performance.
![[image loading]](http://www.teamliquid.net/staff/Teoita/Hubble/img29.gif) Infrared image of the same star cluster taken with the Hubble telescope, and with the ground-based Very Large Telescope, one of the best observatories ever built. Note how Hubble's resolution is better, even though the telescope itself is considerably smaller and more simple than VLT.
In this blog i'll illustrate a few basic astrophysical notions, along with some pretty pictures taken by Hubble. Most of the pictures are taken either from Hubble's webiste (hubblesite.org), or from the commemorative slides found on Nasa's website.
HST has gone through a messed up mirror that for a bit massively decreased its performance, 4 servicing missions with Space Shuttles that changed every instrument on board, a couple of broken gyroscopes that eventually got fixed, and a few failures on most instruments mounted on it. Despite this, the telescope is still able to operate at near 100% efficiency (which is pretty much unheard of for such an old satellite), and over its lifespan the data gathered has produced hundreds of scientific papers, a number unmatched by any other instrument minus the ground telescopes of the ESO observatory.
![[image loading]](http://www.teamliquid.net/staff/Teoita/Hubble/hs199401alarge_web.jpg) This is a picture of the galaxy M100 right after Hubble's launch, and after the first maintainance mission. Hubble's main mirror is slightly deformed - the curvature is off by 0,0022 millimeters, resulting in massive distortions. The first maintainance mission added correptive optics to fix this flaw, resulting in much better resolution.
One of the most important concepts in astrophysics is that, because the speed of light is finite, looking at objects farther away means we are actually looking back through time: light takes about 8 minutes to travel from the Sun to earth, about 4 years from the closest star to the Sun, 2 and a half million years from the closest massive galaxy. The farther away objects - which are also the faintest, whose light has a harder time reaching us - are also the oldest. The ability to see faint objects then becomes extremely important when one is trying to study the evolution of the universe.
The EM Spectrum and the atmosphere
Currently, the only way for astrophysicists to study any celestial body is to analyze the light it emits. However, simply being on Earth strongly limits the light we actually can see: our atmosphere only allows through a tiny portion of the entire spectrum, called the optical or visible range, as well as some radio waves. Anything more energetic, like ultraviolet light, x and gamma rays, or less energetic, like infrared, microwaves and some radio waves, are absorbed by our atmosphere; the only way to see a source emitting X raysthen is to have a satellite outside of the atmosphere, dedicated to that particular interval of the electromagnetic spectrum.
![[image loading]](http://www.teamliquid.net/staff/Teoita/Hubble/atmosphericopacity.jpg) The atmosphere lets visibile and radio light pass, but any other kind of radiation is blocked, meaning we need satellites to see Ultraviolet or Infrared light for example. This is one of the reasons why space observatories are so useful.
The atmosphere is problematic for a second reason, called atmospheric seeing. When we observe the stars from the ground, they appear to twinkle; this isn't caused by the stars themselves, but by any kind of turbolence present in the air, which distorts the original image. This distortion strongly limits the resolution of any telescopes on the ground; it can be corrected to a certain extent, but it's a very expensive procedure that still doesn't produce perfectly still images. This is the second reason why putting a telescope like Hubble in space makes perfect sense, even though it is designed to see light from the (near) ultraviolet to the near infrared, which would mostly be accessible from the ground.
![[image loading]](http://www.teamliquid.net/staff/Teoita/Hubble/eso9006a.jpg) This is a scientific image of two stars orbiting each other, before and after removing the atmosphere's turbolence; the difference is massive. Hubble, being in space, doesn't need this correction.
The Solar System
Hubble allows for very precise imaging and studies of planets in the Solar System; because it's so accurate, only a spacecraft actually visiting a planet can take higher quality pictures. The main advantage of using Hubble instead of a space probe to study a planet is that it's possible to look at each planet periodically, to study its changes and gain a unique insight in the object's geology or metereology. The following pictures show respectively the evolution of Jupiter's Great Red Spot, a massive storm that has lasted at least 150 years and covers an area comparable to the size of the Earth, and polar auroras on Jupiter and Saturn much like those that happen on Earth, showing that both these planets possess strong magnetic fields. The interaction of these magnetic fields with any charged particle present in space is what causes auroras, just like on Earth.
Stars and Nebulae
Some of the most known and prettiest images taken by Hubble are those of nebulae, like the Crab and Cat's Eye nebulae or the gas clouds known as the Pillars of Creation. The term nebula is actually really generic; until about the 1900's it meant any observable object that didn't have a spherical shape, like a star or a planet, but instead looked kind of like a cloud (nebula means cloud in latin). Since then we have learnt that those fuzzy patches of diffused light can be broadly classified in several types:
1) Star formation regions. These are massive clouds of hydrogen gas; because of gravitational instabilities, sometimes this hydrogen collapses on itself, heating up to the point of igniting nuclear reactions within it and forming a new, bright, hot blue star. This happens over and over in a star formation region; indeed, identifying these clouds tells an astronomer wether a certain galaxy, or a region of a galaxy, is actively forming new stars or is not.
![[image loading]](http://www.teamliquid.net/staff/Teoita/Hubble/Pillars1.jpg) ![[image loading]](http://www.teamliquid.net/staff/Teoita/Hubble/Pillars2.jpg) ![[image loading]](http://www.teamliquid.net/staff/Teoita/Hubble/Pillars3.jpg) One of the most known star forming gas clouds in the Milky Way Galaxy, called the Pillars of Creation. The first two images are in visible light, and show the gas clouds. The third one is taken in infrared light, which isn't observed by the clouds and allows to see the stars behind them.
2) Planetary nebulae. These clouds are created as a star evolves. During its lifetime, it will expel most of its envelope, until only a small core of the original star (called a white dwarf) remains. This is also how our own Sun eventually will evolve, about 6 billion years from now.
![[image loading]](http://www.teamliquid.net/staff/Teoita/Hubble/64884main_image_feature_211_.jpg) The Cat's Eye nebula is what remains of a star very simliar to our Sun at the end of its evolution: the envelope has been expelled, and all that remains is a small white dwarf star, the white dot at the center.
![[image loading]](http://www.teamliquid.net/staff/Teoita/Hubble/Carina.jpg) The Carina nebula contains the envelopes of several stars, including some between 10 and 100 times bigger than our Sun. Instead of turning into a white dwarf, they eventually will explode in massive supernovas, leaving behind a neutron star or black hole.
3) Supernova remnant. Supernova remnants are also created by a star's evolution, but their history is much more traumatic. When a very massive star reaches the end of its life, rather than "peacefully" losing its envelope and leaving a tiny remnant behind, it explodes in a massive explosion, called a supernova, possibly leaving a smallish, but very compact object, either a black hole or neutron star (basically a massive clump of neutrons). The matter that doesnt form the central object is ejected at massive velocities and forms a cloud-like structure around the original place where the star was.
![[image loading]](http://www.teamliquid.net/staff/Teoita/Hubble/eso9948f.jpg) The Crab nebula is what remains of the explosion that actually gave supernovas their name. The light of the explosion reached Earth in 1054, and its sudden appearance in the sky was recorded by astronomers all over the world, who thought they were seeing an incredibly bright new star, hence the name supernova (super new in latin).
4) Dark Nebula. This kind of nebula isn't made of simple elements like the others, but of tiny grains of more complex molecules, which astrophysicists simply refer to as "dust". Dust has the particular property of absorbing most visible light, thus obscuring any object behind it at these wavelenghts. In order to penetrate a dust ring it's necessary to observe at some other wavelength.
Hubble has also given significant contributions to exoplanet research - looking for planets around stars far away from ours. This is usually done in two ways: either one blocks out the star's light with some filter, and tries to catch a glimmer of light reflected by any eventual planets that might be present, or tries to catch the "footprint" of the planet as it orbits in front of the star and absorbs part of its light.
![[image loading]](http://www.teamliquid.net/staff/Teoita/Hubble/Planet1.jpg) In this image, the central star is blocked out; the tiny dot the arrow points to is a planet reflecting the star's light. As the planet has orbited the star over the years, its position has changed slightly
Galaxies
Galaxies come roughly in two groups - ellipticals and spirals. As the name suggests, spirals are your typical, pretty galaxy that seems to have a central luminous "bulge", and several spiral arms that envelope the bulge. Ellipticals on the other hand are usually a bit less exciting - they appear as spherical or near spherical clumps of stars, almost like a spiral's central bulge without any arms.
These two kinds of galaxies are massively different from each other. Spirals tend to be filled with gas and star forming regions, leading to very young stellar populations that emit mostly blue and ultraviolet light. Ellipticals on the other hand show very little trace of gas, having already converted most of it in stars, or lost it through some other process. Their stars are very old, which means they mostly emit red and infrared light. This is why the are classified as "red and dead" galaxies. Spectroscopy shows that while a spiral galaxy rotates in a coherent way around its central axis, ellipticals don't have any notable "group" rotation.
![[image loading]](http://www.teamliquid.net/staff/Teoita/Hubble/8416833561_a5e096d251_o.jpg) The Whirlpool Galaxy, whose technical name is M51, is a prototypical spyral galaxy. It is interacting with a "companion" galaxy, and eventually the two will merge and for a single galaxy.![[image loading]](http://www.teamliquid.net/staff/Teoita/Hubble/rosegalaxy600v2.jpg) ![[image loading]](http://www.teamliquid.net/staff/Teoita/Hubble/joseph_comeau_1.jpg) PGC-6240, known as the Rose Galaxy, and also the "twins" NGC 4038/NGC 4039, aka the antenane galaxies are also a spiral galaxies undergoing a merger.![[image loading]](http://www.teamliquid.net/staff/Teoita/Hubble/AstronomyPictureOfTheDayTheS.jpg) M104, called the Sombrero galaxy, is an elliptical galaxy, but it is surrounded by a ring of dust which absorbs visible light.![[image loading]](http://www.teamliquid.net/staff/Teoita/Hubble/m87.jpg) M87 is a massive elliptical galaxy; there is no trace of the massive gas clouds present in spiral galaxies.
Cosmology
Cosmology is the study of the Universe on large scales - rather than focusing on individual objects like stars, clouds or galaxies, cosmologists study the structure of the entire Universe, its "shape", the way matter is distributed in it, its age, how it's expanding, and so on. In order to study exactly how matter is distributed in the universe, of course, we need to know the distance of the objects we see, which isn't nearly as simple as it sounds. Imagine you are seeing a faint dot of light in the sky; how can you tell wether it's a very close, not weak source of light, or really far, but powerful enough to reach us? For most astrophysical objects, it is impossible.
A special exception to this rule is a category of objects called "standard candles". These are objects whose inherent luminosity is known or easily computed, regardless of distance. Once we identify several of these objects it's then very easy to tell which ones are closer or farther away from us: the brightest will be closer, and viceversa. The tricky thing is that this process applies to very, very few phenomena and objects.
The most famous of these are particular stars called Cepheids. Cepheids are massive, pulsing stars whose luminosity varies over very regular periods of a few days or weeks. The length of the period is related to the star's absolute luminosity: the longer the period, the brighter the star. In fact, it's thanks to this kind of stars that astronomer Edwin Hubble in the 1920's first discovered that the universe was expanding: far away galaxies are also running away from us faster, following a very simple linear law: v=H * d, where v is the velocity, H is a constant, d is the distance. The Hubble telescope among its other great contributions to cosmology has helped in making more accurate measurements of the distance of Cepheid stars as well as other standard candles, improving the precision with which the constant H is known.
Hubble has also been able to take pictures of the farthest galaxies ever seen, in an observation survey called the Hubble Deep Field (and later, Ultra and Extreme Deep Fields). The telescope pointed at what seemed to be a mostly empty area of space, watching the same tiny area of about one thirteenth-million of the total area of the sky, over several months, searching for the faintest objects we had ever seen. The result was discovering roughly 10000 galaxies, some of which had formed as little as 450 million years after the Big Bang
![[image loading]](http://www.teamliquid.net/staff/Teoita/Hubble/hubbleultradeepfield_full.jpg) Part of the Hubble Ultra Deep Field. The two objects that seem to form a "cross" of light are very, very faint stars, while all the others are galaxies.
This survey among others has helped our understanding of the so-called Cosmic Web. Matter tends to clump up, forming stars, which then form galaxies, which tend to clump up in galaxy clusters of thousands of galaxies, leaving immense voids between them. Clusters in turn also clump up in massive structures called superclusters,4. If you could zoom out and see how superclusters are distributed, you would see something that looks like a web, or a sponge: superclusters are tendrils of relatively high mass density, with massive voids in between them:
![[image loading]](http://www.teamliquid.net/staff/Teoita/Hubble/all30.jpg) The Cosmic Web. The red and yellow areas are high density superclusters, while the darker ones are the voids between them.
I hope this was a good and educational read for anyone that made it all the way to the end! If you have any questions on anything, or if you would like to know more details, feel free to let me know!
 
|
|
|
Italy12246 Posts
Sure, about what? There's is so much stuff to write about it really is impossible to include everything without writing a book, even without showing any math
|
I never quite understood what happens when a star collapses to a black hole.
I can imagine how that works with neutron stars that the electrons merge with protons and that the neutrons cannot collapse any further.
What happens to all the particles when a black hole forms?
Also, those deep field images are the most amazing photos ever taken.
Like every little dot is one whole galaxy. It's completely, utterly unimaginable.
Also, I had to google how many galaxies there are in the universe and now my mind has burst. What to do?
|
On April 25 2015 01:39 Teoita wrote:
Sure, about what? There's is so much stuff to write about it really is impossible to include everything without writing a book, even without showing any math
i'd like something about inflation. maybe something about slow roll
|
Italy12246 Posts
What actually happens is unknown. It's even possible that quarks might stop the gravitational collapse and form a quark star, like neutrons can do when a neutron star forms, but that idea is waaay out there.
As to what actually happens to matter past the event horizon during and after the collapse, we don't know yet. We know that there's basically always a point when nothing can stop gravity, and the entire core collapses on itself, and we know the properties (or at least, some fo them) of a black hole once it's formed, but other than that we don't have very clear ideas.
Someone likely has solved relativity's field equations for the entire gravitational collapse, but even those do not work at small scales where you'd need to reconcile gravity with quantum mechanics to know what is going on exactly, and that's not really my field so i can't say anything more specific.
The TLDR is as far as we know, somehow shit doesn't stop collapsing until the entire stellar core is concentrated in a single point. At that point however, every physical law we know actually doesn't work, so really we don't know
edit: also
Also, those deep field images are the most amazing photos ever taken.
Like every little dot is one whole galaxy. It's completely, utterly unimaginable.
Also, I had to google how many galaxies there are in the universe and now my mind has burst. What to do?
Yeah i have a poster of the Ultra Deep Field in my room, it's just great. And that's just a tiny little dot in the sky that isn't supposed to have much in it, that's the great part.
And yeah the universe is...really overwhelming. I fucking love it 
|
Italy12246 Posts
Regarding inflation: i made a post about cosmology and inflation in some thread that got closed a while ago:
Essentially, the most accepted cosmological model for the behavior of the universe in large scales, called the lambda-cold dark matter model, predicts among other things that the universe MUST have had to go through a period of extremely accelerated expansion in its early stages.
The reason for this is the existance of three very basic problems im lambda-cdm models that do not include inflation. These are called the flatness problem, the horizon event problem, and the magnetic monopole problem. In order:
1) Flatness: we know from empirical observation that the structure of space-time is flat. Ideally, it could be any kind of 4-dimensional surface with positive, negative or null curvature (just to picture things, in 3 dimensions a sphere has positive curvature while a plane is flat). Not only is the universe flat, but it can be shown easily that the further back in time you go, the more flat the universe gets. This is seriously bizarre; why the hell would the universe be absolutely perfectly flat at its start, when it can assume any possible value for its curvature while still following the same exact physical rules? It's an amazing coincidence, and it's extremely unlikely to just so happen by chance.
2) Horizon distance: this is even wierder. Basically, most photons existing in the universe are part of what is called CMB, or cosmic microwave background. These photons were emitted together billions of years ago, when the universe was still extremely hot. In fact, it was so hot that photons kept interacting with matter, keeping atoms from forming, bouncing from one nucleus to the other instead of being free to go their own way. As soon as the universe cooled enough, the photons suddenly stopped interacting with matter so strongly, and were free to go their own way. This radiation permeates the entire universe. By studying the CMB you can easily see that it was emitted at the same exact temperature at every point in the sky. On paper this makes sense, but if you look at things more carefully, you realize that light (and therefore, information) at the time of the CMB emission did not have time to travel through the entire sky as we see it. In fact, you can divide the sky in roughly 20000 patches of equal size; each of those would be able to transmit information within itself, but not to its neighbours. If these patches can not transmit any information to each other (ie, they can not reach the same temperature), why the fuck are they at that temperature?
3) Magnetic monopoles: this comes from more complex quantum mechanics stuff so i won't go in detail about it. Essentially, some quantum mechanics models predict that magnetic monopoles should exist, and their presence should be easily detectable. So why do we not see them? Is it possible that the universe evolved in a way that made them disappear?
Inflation theories solve all these problems. Inflation essentially states that there was a period in the early history of the universe, during which the expansion of the universe was INSANELY fast. This solves the 3 problems of traditional lambda cdm models:
1) Even if you start with a very curved universe, if you stretch it immensly it ends up being very very flat.
2) If the universe expands extremely fast for a while, then before it expanded it was extremely tiny, to the point where it could exchange information with every part of it, reaching the same temperature easily.
3) Slightly more complex, but ideally even if magnetic monopoles exist, the expansions "stretches" them so much that they become insanely rare, almost non existant.
How here's the problem: well shit if everything becomes perfectly uniform, how come the universe we see isn't uniform? Why do we see stars, globular clusters, galaxies, galaxy clusters and superclusters? So far, you'd think that inflation would make everything perfectly homogeneous.
However, what does happen is that when you first start with your tiny, small universe before inflation, it isn't perfectly homogeneous because of quantum mechanics. At a very very tiny scale the universe isn't empty: particles are constantly destroyed and created, according to Heisenberg's uncertainty principle: E*t>h, where E is the energy, t is the time, h is planck's constant. As long as a pair of particles of energy E exist for a time shorter than t, in order to respect the uncertainty principle, they are free to be born out of nothing, and return to nothing shortly after. This phenomenon is called vacuum energy. The way it ties into inflation is simply that these fluctuations are blown to huge sizes when infllation starts, and are what forms the large scales structures like galaxy superclusters that we see today.
Now, regarding slow/fast roll specifically, i'm not sure how to explain it without math so i will just assume you know roughly how a scalar field works. This is how we imagine the inflation scalar field looks like:
![[image loading]](http://universeinproblems.com/images/thumb/4/4d/Inflation_3_2_1.jpg/300px-Inflation_3_2_1.jpg)
Imagine a ball sliding on a plane shaped like that potential; initially it will move very slowly, as the potential is kind of flat. This is called the slow roll condition. As it moves, it picks up more and more speed until it reaches a minimum, which is the fast roll condition. Inflation works just like that. On the left side of the curve, where it's relatively flat, the field isn't "pushing" the universe to expand very quickly, meaning the universe is "slowly" rolling towards the minimum. As inflation continues however the curve becomes more and more steep, and the universe keeps accelerating its expansion until it reaches the minimum of the potential.
I hope that made sense.
|
So what kind of telescope do I need to attach my camera to in order to take some sweet ass stellar photos?
|
Italy12246 Posts
|
Is there a general sense of "up" and "down" in space? For example, on Earth, if I stand on my hands, blood will come down and I will feel the pressure in my head so I'm clearly aware than I am upside down. If I was in space, will I have any sense of up and down?
I ask because I'm looking at the gas cloud pictures you posted (pasted one of them below), and it looks like the top area is most dense, and as you go down, it gets less dense, like remnants of the gas are falling. Are there clouds where the formation is reversed? As in the clouds are dense on the bottom and as you go up in the formation there is less density.
+ Show Spoiler +
|
What's next for telescopes? Crazy that we're using the same telescope for 25 years, and it's been top of the line.
Any new larger telescopes to put in orbit, or an asteroid, etc? Anyway, the pictures were really pretty, thanks the write up.
|
Italy12246 Posts
Well up and down is defined by the gravitational field being present. If you were floating in orbit on the space station, (or ina gas cloud really) you couldn't tell up from down since nothing is pulling you. In taking that picture Hubble most likely just rotated on itself to make the pillars look straight and "right".
|
Italy12246 Posts
On April 25 2015 02:52 FiWiFaKi wrote:
What's next for telescopes? Crazy that we're using the same telescope for 25 years, and it's been top of the line.
Any new larger telescopes to put in orbit, or an asteroid, etc? Anyway, the pictures were really pretty, thanks the write up.
Regarding space telescopes, the next two bigass missions are the James Webb Space Telescope and, hopefully, ATLAST.
JWST is kind of Hubble's successor, but it's mainly an infrared mission so it's not quite the same. It's been delayed for a while, and hopefully it will be launched in 2018, and hopefully it will start gathering data around 2019-2020. It won't be orbiting Earth like Hubble does, so it will take a while after launch before it can actually be used. In those couple of years it should actually work together with HST, which is really cool. For comparison, Hubble's main mirror is two meters, Webb's is 6.5.
ATLAST (the name is actually a pun on how long it took to decide the exact band the telescope is supposed to work on) is Hubble's true successor as far as the part of the em spectrum it will study, but it's just a proposal now that will hopefully be built in the next decade or two. It will also go far away from Earth, on a similar orbit to JWST. People are expecting it to have an 8 to 16 meter mirror, which is absolutely unheard of for a space telescope.
Regarding ground telescopes, while it's true that HST still has the best resolution, the last generation observatories like Subaru, VLT and Keck are close to matching that performance, and the next one should be able to surpass it. The technology used to correct the deformation introduced by the atmosphere (which is pretty much the biggest limiting factor for ground observatory) has improved immensly, allowing us to build even bigger telescopes. For example, VLT has 4 mirrors of 8.2 meters each; the next generation is expected to have between 25 and 40 meters of aperture.
|
What's the current state of astrophysical research?
What was the last big finding?
How big are hopes for new findings and how much is still unsolved?
|
Italy12246 Posts
As with all science, for every answer we find, we come up with 10 more things we dont know. We really dont know shit, and this goes for pretty much everything, not just astrophysics. It's really exciting.
I guess the biggest last finding is the discovery of the acceleration of the expansion of the universe in the early 2000's, and along with that all the observational confirmations for the lambda cdm model in these past decade.
There's MASSIVE things we haven't discovered yet, and that we will hopefully figure out in the next decades. The ESA mission Lisa Pathfinder should be the first to detect gravitational waves from astrophysical sources, exoplanet research is skyrocketing, the AMS particle detector on the international space station just recently detected what could be the signature of dark matter particles annihilating each other. These are just the flashy things, there's plenty more don't know.
|
Teo are you an astrophysicist? 
That's what I'm trying to get into (finally going through school now), working as an architect right now. I didn't know that you were so interested in space. This is my favorite blog EVER lol, I love finding stuff that I might have just written in my sleep Fight Club style.
Happy birthday hubble!
|
Italy12246 Posts
Yeah i am, i'm getting my master's and i want to pursue it as a career
|
cool to see such dedication to outreach!!. my wife has a phd in astrophysics (galactic dynamics) and i am a "half-assed astronomer" myself (astroparticle physics.7th year grad student...) so if you ever feel we can be of service, drop me a message
|
The most interesting thing to me in all of physics (okay i guess this is kinda only tangentially related but still) is why there is no good quantum theory of gravity
|
On April 25 2015 05:04 Teoita wrote:
Yeah i am, i'm getting my master's and i want to pursue it as a career
Who hires an astrophysicist?
I mean, what you know is great, but is there anyone in the public sector that desires this kind of knowledge about the universe? If all of the sudden everyone in the world forgot how everything functions beyond our solar system, I don't think much would change for anyone's life (minus the astrophysicist, pardon me, I'm a mechanical engineer). Anyway, seems mostly the government bodies of NASA or large EU programs, and universities, etc.
Anyway, thanks for answering my question. My real interests lie in the questions we don't have answers for yet, it's just the classical big bang theory is very unsatisfying to me, and I have a desire to understand what was before, what initiated the big bang, why was it at that point in time exactly, etc etc.
The other thing you mentioned in another reply is you gave the rolling ball example, to determine where the lowest potential would be. But if we make the assumption that there is nothing in the universe outside of what was created during the big bang, we can look at our 3(or 4 however you look it) fundamental forces.
Gravity: Okay, so this force should result in everything attracting back together
Strong Interaction: Isn't this only the interaction between quarks, and as such, we never really experience it in the observable universe? All the effects we see are the residual strong force, which is a result to quarks not lying on the exact same point in space, and thus a nucleus can exist?
Weak Interaction:
Electromagnetism: Aren't things mostly charge neutral once you get big enough, don't see how this force should be at all significant in the grand scheme of the universe, only microscopically?
Weak Interaction: Know little about this (like everyone else it seems), but I know it's a super short range force associated with changing quarks to different flavors?
So the only way to make everything work is assume that our universe is made up of 70% and 25% energy and mass respectively, and say we have no way of detecting it with anything, it does not have any interactions with anything "real" (otherwise we could recognize it's there), and yet it's still able to somehow speed of the expansion of the universe? Just confusing as to what the current theory is. And also, gravity acts even when thermodynamic equilibrium has been reached, so isn't the location of lowest potential somewhere close to a compaction of the universe?
My other question was about the loss of information principle, or whatever it's referred to. Saying that if we knew the exact property of every single property in the universe, we could predict the exact future or past of everything. Is this possible, is information conserved? Because the two things that came up were the Heisenberg's uncertainty principle, and the information loss in a black hole... Anyway, just was wanting your input on that, kind of related to determinism and being able to trace origins back before big bang, etc.
And lastly, my other question was benefits do you see from astrophysics coming in the future? It seems like where all the interesting stuff has been occurring recently, are the particle accelerators. Most of everything that occurs in the solar system can be explained quite well to a layman in the subject like me.
Feel free to pick just little tidbits you wish to answer, if none at all. Thanks!
|
|
|
|
|
|
EPT![[image loading]](http://www.teamliquid.net/staff/Teoita/Hubble/14135jupiter2.jpg)
![[image loading]](http://www.teamliquid.net/staff/Teoita/Hubble/Auroras.jpg)
