/sci/ - Science & Math

[Anonymous No.3149503]

hey /sci/,
I've been interested in cosmology lately and i've got some questions I'd like answered... or atleast give me something to read to get my answers. This is not hurrdurr homework.. it's summer... I'm just curious about all these things i've heard of and learned about briefly in my intro to astrophysics class last semester (option).

Can you describe the milky way galaxy. What's special about the bulge, the disk and the halo??

How does hubble’s observations indicate that the universe is expanding, and how it does not indicate that we are the center of the Universe. What's hubble's law? and how the fuck can we estimate the age of the universe with this "hubble constant"?

Why was it so difficult to obtain definitive values for this hubble constant?

What are the three (or four?) possible futures for the Universe? What is the physical property of the Universe which would ultimately determine its fate? How does it affect the age of the Universe?

What is dark matter? What evidence do we have that it exists? How is the rotation curve of spiral galaxies a direct proof for dark matter?? What are the most likely candidates for dark matter and how can they be detected?

What is dark energy? What evidence do we have that it exists? What impact does it have on the evolution (and fate) of the universe?

What is the most likely scenario for the future of the Universe. How can we take into account dark matter and dark energy?

[Anonymous No.3149533]

bump for answers, or atleast sources to answer them

[Anonymous No.3149542]

>sources to answer them

http://www.wikipedia.org/

[Anonymous No.3149551]

>>3149503
>How do Hubble's observations indicate that the universe is expanding...
Look into the Doppler effect, specifically redshift and blueshift. Hubble's law as a function can be traced back to when there was no distance between galaxies (where the curve hits the x-axis), which is assumed to be when the universe began (when it started expanding).

>Why was it so difficult...
Because distances between other galaxies were under dispute, since most were based on different physical assumptions.

>What are the three...
The four "Big" ones are Big Freeze, Big Rip, Big Crunch, and Big Bounce. I think the most supported is the Big Freeze theory, which says that the universe will continue to expand and the average temperature of the universe would approach absolute zero.

>What is dark matter?...
Let me Google that for you..

>What is dark energy?...
Let me Google that for you..

>What is the most likely...
Personally I see great sense in the Big Freeze theory, but I can't claim to understand the changes that dark matter brings to the discussion.

[Anonymous No.3149559]

>>3149542
summer /sci/.. gotta love it

[TRIPPY MC FAGFACE No.3149564]

BEFORE THE INTERNETT AND GAYGLE THERE WAS THESE THINGS CALLED BOOKS
READ THEM OP

NOW FUCK OFF

[TRIPPY MC FAGFACE No.3149566]

>>3149559
SUMMERFAG SUMMERFAG
IM SO SMART LOOK AT ME IM IN COLLEGE AND IM MAJORING IN DICKBUTTING
EVERYONE PAY ATTENTION TO ME AND MY ASSBURGERS

[Anonymous No.3149576]

>>3149566
>>3149564

[TRIPPY MC FAGFACE No.3149583]

>>3149576
YAH IM SUPER SUPER MAD BRAH
THE EXPIRMENT GOV SUPER SEKRET CRYSTAL DICK GUY LEFT AND I CANT BUST MY NUT ANYMORE
SHIT SUCKS

[Anonymous No.3149589]

>>3149583
OP here, stop derailing my thread.
For once there's a science related thread and u bring up this faggotry?

[Insinuations gOdS No.3149601]

>>3149551
>I think the most supported is the Big Freeze theory.

It is. But the big breeze doesn't necessarily rule out an eventual big crunch, depending on the definition. The debate is still open and the mathematical conclusions has yet to be drawn on what might happen. The Big crunch is still fully valid.

[Anonymous No.3149616]

bump

[Anonymous No.3149714]

[Anonymous No.3149732]

cmon I thought /sci/ was good at this

[Anonymous No.3149744]

>>3149732
If /sci/ were actually good at science and math, no religious or philosophical trainwreck of a thead would ever exist longer than it takes to ignore it.

>real scientists know when to ignore insignificant details

[Anonymous No.3149748]

>>3149744

Religion and philosophy are very important issues, seeing as how the entire world is ran by religious people. They decide what science gets to make it and what science gets to take hundreds of years to progress because it doesn't agree with God.

[Anonymous No.3149751]

>>3149503
homeworkhomeworkhomeworkhomeworkhomeworkhomeworkhomeworkhomeworkhomeworkhomeworkhomeworkhomeworkhome
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[Anonymous No.3149754]

bumpan

[Anonymous No.3149762]

>>3149751
>This is not hurrdurr homework.. it's summer... I'm just curious about all these things i've heard of and learned about briefly in my intro to astrophysics class last semester (option).

read first, retard.

[Anonymous No.3149763]

>>3149748
>completely misses the premise

[Anonymous No.3149772]

>>3149763

You're saying people should dismiss any discussions of religion or philosophy, I'm explaining why they're important. Enlighten me as to how I missed the point...

[Anonymous No.3149783]

bump

[space nerd No.3149784]

Not sure what you mean by special, the bulge in the center is because of stars being pulled into the super massive black hole in the center, it thins out with ditance because gravity is inversely related to the square of the distance.

Hubble observed that light from distant galaxies is red-shifted which occurs when the wavelength increases because it moves away from the observer (see Doppler effect). Because of the amount it was red-shifted it can be calculated how fast the universe is expanding (hubbles constant), reversing it until everything is infinitesimally close gives us the age and the Big Bang theory. We ARE NOT the center of the universe, nothing is, everything is moving away from each other equally, not away from us alone, imagine a balloon with dots on it inflating, no dot is in the center.

The constant was difficult because of what was said already, the distances where under dispute

The theories of the end of the universe were mentioned.

Dark matter is matter that doesn't give off electromagnetic radiation (light) but was deemed necessary to explain why certain galaxies without enough stars don't fall apart and why the stars at the edge revolve aroun the center as quickly as they do.

Dark energy another made up thing to make sense of our observation. it's the energy that causes the universe to expand and at an increasing rate.

Big Freeze is most likely, the gravity of dark matter and matter likely wont be able to overcome dark energy and the universe will expand indefinitely.

[Anonymous No.3149786]

>>3149772
>strikes out again

[space nerd No.3149787]

>>3149772
If it was for actual discussion it would be nice but it's not, it's about bashing and prevents threads like this that are about math and science from being made because people who care don't bother to come here.

[space nerd No.3149802]

You should read Brian Greene's books if your interested in this stuff, Fabric of the Cosmos or the Elegant Universe. Hawkins also has some basic books like the grand design or somewhat more in depth ones like A Short History of time or A Shorter History of Time. One of the first books I read was Quarks, Leptons and the Big Bang by Jonathan Allday and it was rather good for getting an understanding.

[Anonymous No.3149823]

>>3149802
ty I'll try to get ahold of these

[space nerd No.3149837]

>>3149802
>brief history of time, briefer history of time

[Anonymous No.3150031]

PREPARE TO SCIENCE
Hubble’s observation is that the farther away a galaxy is, the faster it is moving away from us, and that this is true for all galaxies, in every direction (pretty much symmetrically too). This means that the universe is expanding, because duh. We are not the center of the universe because the universe is isotropic and homogeneous on cosmic scales, meaning that on sufficiently large scales, if you look from any direction from any particular spot, the universe will look the “same” to you. Even though galaxies are symmetrically travelling away from us (so it would seem like we are at the center of an expanding sphere), this observation would be true if we were 50 billion light years away from earth too. Both spots cannot be the “center”, so it doesn’t follow from Hubble’s law that we are the center of the universe. Hubble’s law is v = H * r, where v is the velocity of a galaxy at a distance r from us, and H is Hubble’s constant.

[Anonymous No.3150040]

>>3150031
This constant is so hard to determine because distances are hard to measure, velocities are hard to measure, and galaxies have “peculiar velocities”, which are velocities in random directions with respect to the overall radial velocity from expansion. So the two variables v and r are not easily determined, and when we measure them for a bunch of stars and put the results on a graph, we get a not very straight line, meaning there is a lot of error in the slope of the line (the slope being Hubble’s constant). We can estimate the age of the universe using Hubble’s constant because if galaxies are expanding away from each other now, it follows that they were all close together at some point before. The time that this is so is given by the distance they have travelled divided by the velocity at which they travelled (this estimation assumes no forces accelerate or decelerate galaxies velocities). Thus time = r/v, and by plugging in Hubble’s law we get time = 1/H. Thus the “Hubble time” is an estimate for the time at which all galaxies were at a single point (the moment of the Big Bang). It has a value of 14 Gyr or so.

[Anonymous No.3150043]

>>3150040
Dark matter is matter that doesn’t interact with light. Therefore it is non-baryonic matter, since baryonic matter (which is made up of protons and neutrons) does interact with light. It isn’t something we’ve detected directly, since the non-baryonic matter in the universe that we know of (neutrinos, for one) doesn’t account for all the of the dark matter we think is there. We infer the presence of dark matter because of the so-called “galaxy rotation problem”, which is the observation that using standard gravity theory (Einstein/Newton) and the amount of luminal matter (matter we can see—non dark matter), the velocities of the outer regions of spinning galaxies are moving too fast to be held in by the gravity of the galaxy itself. This is not true if there is more mass than we can see, and we can infer the amount of “extra mass” needed very simply, by using Einstein’s/Newton’s equations and the velocities we observe. Another possibility to this “rotation problem” is that Einstein/Newton are simply wrong about gravity on such massive scales. It is possible that on terrestrial and even solar system scales that their gravitational theories only work so well because they are an approximation in this small scale limit. It could be that gravity works differently on large scales, and that we only notice this effect on the scale of galaxies and clusters of galaxies. So galaxies rotations are NOT direct proofs for dark matter.

[Anonymous No.3150046]

>>3150043
There are even modified gravity theories that successfully account for the rotation problem, such as MOND and MOG theories (google them if you’re curious). MOND theory turns out to be crap, because it didn’t work when it modeled the “Bullet Cluster” of galaxies (which is a cluster of galaxies that collided, and where the centers of luminal masses don’t line up with the centers of curvature). The bullet cluster can be explained by dark matter or MOG theory, however. But as of yet, MOG theory isn’t theoretically justified enough to be a convincing alternative to dark matter because it requires the introduction of parameters that have no theoretical basis. Basically, they have to bullshit numbers to make it work. So the best explanation of the galaxy rotation problem and the bullet cluster’s behavior is dark matter.

[Anonymous No.3150058]

Three candidates for dark matter are axions, MACHOs and WIMPs. Axions are theoretical particles similar to neutrinos, and we haven’t seen them. Axions have pretty much been given up on. MACHOs are “Massive Compact Halo Objects”, and include brown dwarfs, white dwarfs, neutron stars, and black holes. All of these we know exist, and account for some of the dark matter present in the universe, but not nearly enough. The best candidate for the remaining dark matter are WIMPs, or Weakly Interacting Massive Particles. These particles are theoretical as well, but better founded in particle physics. They only interact with the weak force and gravity, and thus would not interact with light (which is a manifestation of the electromagnetic force). One predicted particle is called the neutralino. There are predictions about the characteristics of neutralinos based on particle physics, and using this expectation and our knowledge of particle physics, we can use the bullet cluster to test whether these account for dark matter. Basically, dark matter and dark antimatter collisions should produce electron/positron pairs that should map a trajectory of the bullet cluster’s path in a specific way if neutralinos are this dark matter. If this is observed, then this is strong evidence for the existence of neutralinos. I don’t think the observations have been able to be made yet, though… I’m not up to date on the success or failure of this.

[Anonymous No.3150067]

Could someone explain the big freeze to me? I thought entropy will continue to increase? Doesn't that imply higher temperatures?

[Anonymous No.3150076]

>>3150067
no? The universe will lose radiation to the point where all matter is diffuse.

After that, it should collapse.

[Insinuations gOdS No.3150111]

>>3150076
I endorse this, but there might be more phases in between. There are still some exotic materials out there still not even experimentally proven, but mathematically. We know nothing of how these interact with known matters, nor about their history or future. Such as negative matter, and negative energy. How do negative matter intereact nuclei-wise, how does it interact with the strong/weak force. How does it work with gravity? Can it become plasma? There is so much to do ..