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On June 28 2010 12:57 Sparkyrabbit wrote:
When light travels through the universe while the universe is expanding the light becomes redder.
That is correct.
If we look at the redshift in light from super nova's from stars farther away as opposed to those closer we can notice something almost chilling. The redshift is disproportional. How so? Well the redshift from the super novae farther have undergone lest redshift then those super novae closer to us in relationship to their distance.
That is incorrect. The wavelength of light increases as it travels through expanding space. The light from more distant stars travels through more expanding space and has a longer (redder) wavelength as a result.
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I am no expert here. Just a high schooler who enjoys astronomy.
No theories can be confirmed really. Take for example, gravity. This moment, it exists as the laws of the 'theory' indicate, but there's nothing to prove that in the next moment, it'll disappear. Sure, you don't expect it to happen, but you can't 100% predict it.
To try and figure out how the universe works, people make theories to try and explain it. No one knows if the theory of relativity is correct, we assume it is and base other observations from it. If we look back in history, there were so many 'theories' that were assumed to be 100% correct. The simplest example, the Earth is flat. It was just assumed that it was. Everyone believed it until it was proven false.
Until better theories come up to explain how the universe work, there's nothing much else we can do but rely on our current findings about dark energy and dark matter, etc, etc. Work with that or find a theory that explains everything we can observe better.
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Dark matter = something that we can measure the gravitational effects of but we cannot see
As a more concrete example, think of the solar system.
The planets on the farthest reaches travel at a slower rate than the ones near the Sun.
(and if we had a more massive Sun, everything would be sped up)
If you look at a distant galaxy, the stuff on the outer edges is moving too fast for the amount of visible matter.
So either theory is incomplete or there is invisible matter.
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Mindcrime you misinterpreted my explanation. Allow me to rephrase: When comparing the redshift of supernovae, one much farther away then the other we can notice two things. The first thing is that the redshift from the farthest nova has a redder light. The other thing is the the closer nova has undergone more redshift in proportion to it's distance as compared to the otherone. What we can infer from this is that the universe is expanding faster then it was long ago.
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It's true that a lot of these ideas originate from attempts to account for inconsistencies between theory and observation (dark matter), or attempts at mathematical reconciliation of incompatible theories (string theory). However, the fact that many of these ideas seem bizarre and relatively incomprehensible shouldn't really bother you. For starters, you need to consider the fact that extant theories which have been incredibly successful seem really weird when we try to conceptualize them. Quantum mechanics and general relativity at their core result in some extremely weird ideas (the particle is everywhere at once given certain probability boundaries, until you see it - then it's only in one place!; space and time are a continuum, and they are curved? what does that even mean).
Quantum mechanics and general relativity can only be conceptualized by distant analogy, and the physical realities they describe have no meaningful relation to our everyday experience of the world. What is important about those theories is not that they tell us how to look at the world, but rather because they are scientifically useful. The lines, of course, get blurred when these ideas are represented on tv-shows. The general viewer doesn't want to hear "scientists have foundl mathematical reconciliation between special relativity and newtonian gravity to be useful in more accurately describing the motions of large bodies", they want to hear "scientists have found that space and time are one, and you can travel back in time...maybe".
Essentially what I mean to say is that nothing in science is really true, it is only ever useful. Further, if current speculations and areas of theoretical research bother you, then so too should well established sciences (because they are just as weird).
Gyth: Have you read the book "Faster than the Speed of Light"? It talks about how a variable speed of light might provide an alternative to inflation (although it is talking about variation over time, not variation in different regions). It might interest you (it is a bit light on the science though...)
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On June 28 2010 14:02 gyth wrote:Show nested quote +Dark matter = something that we can measure the gravitational effects of but we cannot see As a more concrete example, think of the solar system. The planets on the farthest reaches travel at a slower rate than the ones near the Sun. (and if we had a more massive Sun, everything would be sped up) If you look at a distant galaxy, the stuff on the outer edges is moving too fast for the amount of visible matter. So either theory is incomplete or there is invisible matter.
What theory is incomplete? I dont get what youre geting at
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On June 28 2010 14:02 gyth wrote:Show nested quote +Dark matter = something that we can measure the gravitational effects of but we cannot see As a more concrete example, think of the solar system. The planets on the farthest reaches travel at a slower rate than the ones near the Sun. (and if we had a more massive Sun, everything would be sped up) If you look at a distant galaxy, the stuff on the outer edges is moving too fast for the amount of visible matter. So either theory is incomplete or there is invisible matter.
Huh? The planets further from the sun travel at a slower rate because they have further to go around the sun then the ones closer, not because of dark matter. Also the suns gravitational pull on those planets is less... g = GmM/r^2
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Most of the local stuff around Earth works fine without Dark Matter and Dark energy as far as I know. It's just the Universe as a whole that needs the two to work in our current physics model.
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On June 28 2010 14:03 Sparkyrabbit wrote:
Mindcrime you misinterpreted my explanation. Allow me to rephrase: When comparing the redshift of supernovae, one much farther away then the other we can notice two things. The first thing is that the redshift from the farthest nova has a redder light. The other thing is the the closer nova has undergone more redshift in proportion to it's distance as compared to the otherone. What we can infer from this is that the universe is expanding faster then it was long ago.
You're contradicting Hubble's Law. What is observed is that there is a linear relationship between redshift and distance.
This is why we think the universe is expanding at an accelerating rate.
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Huh? The planets further from the sun travel at a slower rate because they have further to go around the sun then the ones closer, not because of dark matter. Also the suns gravitational pull on those planets is less... g = GmM/r^2
Yes, and the stars traveling around galaxies can be observed to NOT follow the same relationships.
You're contradicting Hubble's Law. What is observed is that there is a linear relationship between redshift and distance.
The theory of dark energy came about because observation diverges from hubble's law.
P.S. The link contradicts hubble's law too.
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Dark Energy and Dark matter Particles have NOT been found yet. They're numerous experiments today to try and detect such particles (through gravitational waves though to be produced from black holes) Off the top of my head the current Experiments include the Large Hadron Collider (LHC) which is trying to produce said particles artificially for a fraction of a microsecond. They're also satelites in space which try to detect gravitons and gravitational waves as i Said earlier, however we still have no direct hard evidence for the existence of Dark Matter. (sorry had to bring that up after i skimmed some posts saying we had found particles or that Dark matter HAS to exist, its still just theoretical.
For my second part, im going to drop a twist on the big bang theory that i absolutely love. The Theory states that our universe could have been born in a black hole. Link to the story Here
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On June 28 2010 14:31 gyth wrote:Show nested quote +You're contradicting Hubble's Law. What is observed is that there is a linear relationship between redshift and distance. The theory of dark energy came about because observation diverges from hubble's law. P.S. The link contradicts hubble's law too.
....no
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Aotearoa39261 Posts
On June 28 2010 13:52 gyth wrote:I think you guys are being a little cavalier. An apple falling from a tree is an observation. But the reason is not so clear. Is it because all massive objects attract each other, or is it because massive objects distort space-time? (or is it just seeking its natural place?) Dark matter/energy make an assumption about what would be needed in order for the observation to fit current theory. But it could be that current theory just needs an overhaul. P.S. And observation based on doppler shifting would get a little dicey if assumptions, like the speed of light being constant, aren't right. To be perfectly honest, Dark Enery or Dark Matter doesn't "have" to exist. But the alternatives are really quite silly. The only other reasonable explanation is that Newton's law of gravitation behaves differently macroscopically. This really doesn't have much traction though, because at the moment there is no indication of the law breaking down at all so.... yea... Dark matter/energy is the most logical explanation for what we observe at the moment.
iirc, they ran a computer simulation of the galaxy being "born" from the big bang with the appropriate quantities of matter and dark matter and whatnot and the result was surprisingly accurate.
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I agree with Plexa for the most bit. Some of you are saying "dark energy HAS to exist" or "dark matter CANT exist" but the truth is, we don't know. We do know its the best theory we have right now. I read a few articles about how we "filled in" our lack of understanding with supernatural forces to explain why our theories don't make sense. It's akin to us inventing the mystical aether mentioned in the OP, but what scientists failed to realize was that their theories just didn't work, and a new theory was invented without use of the aether.
Note: Dark matter probably DOES exist, plenty of indirect evidence such as gravitational lensing. Dark energy..... ehh...... perhaps not.
There were a few articles on Science daily about how the cosmic microwave background radiation might be distorted, the distorition affecting the evidence for dark energy/matter. I'll have to check up on that.
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United States10328 Posts
On June 28 2010 14:31 gyth wrote:Show nested quote +Huh? The planets further from the sun travel at a slower rate because they have further to go around the sun then the ones closer, not because of dark matter. Also the suns gravitational pull on those planets is less... g = GmM/r^2 Yes, and the stars traveling around galaxies can be observed to NOT follow the same relationships.
For example, take the milky way galaxy. If there ere no dark matter and our existing theory of galactic formation (spinning glob flattens) holds, then the galaxy's rotation curve should look a certain way. Specifically, beyond the edge of the visible galaxy, objects' angular momentum should decrease... But that's not what's observed (observations indicate there's more mass inside those objects' orbit than can be seen, and we infer that mass to come from dark matter.
Show nested quote +You're contradicting Hubble's Law. What is observed is that there is a linear relationship between redshift and distance. The theory of dark energy came about because observation diverges from hubble's law. P.S. The link contradicts hubble's law too.
Hubble's law isn't contradicted; it holds at any instant in time (or so we believe). What's happening is Hubble's constant is changing.
See http://en.m.wikipedia.org/wiki/Hubble's_law, the graph on the "fate of the universe."
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as pandain said, dark matter probably does exist, just cuz of stars forming where nothing was before. could b black holes, but gravitation is not big enough for THAT. so yea, dark matter probably does exist. dark energy? idk.
btw: its just called "dark" cuz we cant observe it directly, in opposition to the rest of the universe. and, for the sake of completing the statement, most of the universe has to consist of "dark whatever". estimates are like: 74% dark energy, 22% dark matter and like 4% of visible matter. if the estimates are that high for things we cant observe, something has to be up and coming in the next few years. maybe LHC will shed some light on all that "dark" matters 
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The only other reasonable explanation is that Newton's law of gravitation behaves differently macroscopically. This really doesn't have much traction though, because at the moment there is no indication of the law breaking down at all so...
Newton's law of universal gravitation did break down. (general relativity)
Mindcrime
You're contradicting Hubble's Law. What is observed is that there is a linear relationship between redshift and distance. ]343[
Hubble's law isn't contradicted; it holds at any instant in time (or so we believe). What's happening is Hubble's constant is changing.
I was arguing over the linearity of the relationship.
My understanding is that we don't observe a linear relationship and that dark energy is the hypothetical reason for the change in slope.
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EPT
