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http://news.yahoo.com/s/space/20080930/sc_space/doweliveinagiantcosmicbubble
Do We Live in a Giant Cosmic Bubble? Clara Moskowitz
Staff Writer
SPACE.com
Tue Sep 30, 7:03 AM ET
If the notion of dark energy sounds improbable, get ready for an even more outlandish suggestion.
Earth may be trapped in an abnormal bubble of space-time that is particularly void of matter. Scientists say this condition could account for the apparent acceleration of the universe's expansion, for which dark energy currently is the leading explanation.
Dark energy is the name given to the hypothetical force that could be drawing all the stuff in the universe outward at an ever-increasing rate. Current thinking is that 74 percent of the universe could be made up of this exotic dark energy, with another 21 percent being dark matter, and normal matter comprising the remaining 5 percent.
Until now, there has been no good way to choose between dark energy or the void explanation, but a new study outlines a potential test of the bubble scenario.
If we were in an unusually sparse area of the universe, then things could look farther away than they really are and there would be no need to rely on dark energy as an explanation for certain astronomical observations.
"If we lived in a very large under-density, then the space-time itself wouldn't be accelerating," said researcher Timothy Clifton of Oxford University in England. "It would just be that the observations, if interpreted in the usual way, would look like they were."
Scientists first detected the acceleration by noting that distant supernovae seemed to be moving away from us faster than they should be. One type of supernova (called Type Ia) is a useful distance indicator, because the explosions always have the same intrinsic brightness. Since light gets dimmer the farther it travels, that means that when the supernovae appear faint to us, they are far away, and when they appear bright, they are closer in.
But if we happened to be in a portion of the universe with less matter in it than normal, then the space-time around us would be different than it is outside, because matter warps space-time. Light travelling from supernovae outside our bubble would appear dimmer, because the light would diverge more than we would expect once it got inside our void.
One problem with the void idea, though, is that it negates a principle that has reined in astronomy for more than 450 years: namely, that our place in the universe isn't special. When Nicholas Copernicus argued that it made much more sense for the Earth to be revolving around the sun than vice versa, it revolutionized science. Since then, most theories have to pass the Copernican test. If they require our planet to be unique, or our position to be exalted, the ideas often seem unlikely.
"This idea that we live in a void would really be a statement that we live in a special place," Clifton told SPACE.com. "The regular cosmological model is based on the idea that where we live is a typical place in the universe. This would be a contradiction to the Copernican principle."
Clifton, along with Oxford researchers Pedro G. Ferreira and Kate Land, say that in coming years we may be able to distinguish between dark energy and the void. They point to the upcoming Joint Dark Energy Mission, planned by NASA and the U.S. Department of Energy to launch in 2014 or 2015. The satellite aims to measure the expansion of the universe precisely by observing about 2,300 supernovae.
The scientists suggest that by looking at a large number of supernovae in a certain region of the universe, they should be able to tell whether the objects are really accelerating away, or if their light is merely being distorted in a void.
The new study will be detailed in an upcoming issue of the journal Physical Review Letters
Any amature Scientists have a theory on what is doing that ?
This kind of thinking makes my brain bleed.
GratefulCitizen
10-01-2008, 00:06
Any amature Scientists have a theory on what is doing that ?
I'll bite.
Perhaps they should revisit their underlying assumptions.
Scientists love to pretend that their arguments do not begin with some basic assumptions.
The Copernican principle is an assumption.
The value of c being fixed throughout the history of the universe is an assumption.
You will often see attempts to "prove" these assumptions.
Such arguments usually amount to the logical fallacy known as "affirming the consequent".
Concerning the value of c being historically constant:
http://arxiv.org/PS_cache/astro-ph/pdf/0305/0305457v3.pdf
In order to discuss this we have to first understand the basic’s of “Quantum Mechanics”, which is the understanding or the investigation of systems at the atomic level. It is also the intense study of those systems. We study, at least in my mind, those systems to understand the function of classical mechanics. That is; the study of everything from the particle to the galaxies. Simply put, by studying the atom and its reaction to and in its environment; and the study of its interaction as it collides with the nucleus of an atom, it should reflect in its microcosm a similar reaction in the universe. Hence, the adherence to the laws of Newton and the Copernican test to justify any relevant application as it applies to physical properties as we know them here on earth, or as we have formulated as absolutes to comprehend our experience in this physicality.
Truths if you will, to define this reality. The problem arises by the simple question that if gravity is true here it should be true everywhere. Simple enough, but that doesn’t appear to be the case, which leads us to the two fields of physics.
Physics is broken into two fields of study, one is classical and the other is quantum. Classical studies the laws, gravity, light speed, Newton etc, in essence what in measurable, or what can be observed, while Quantum studies typically what is not observable.
The logical part of CM states as a principle; atoms, and the electrons in atoms will expands at the speed of light and collide with the nucleus and therefore make stable atoms, or stationary atoms impossible, according to the classical studies, the laws, or moving bodies governed by the laws adhere to this principal; but in the “natural world” electrons remain in a orbit around the nucleus and this contradicts the fundamentals of electromagnetism, which, if you will, is what our experience is based on, here on earth in relation to the universe at large.
What Quantum mechanics investigates is why the electron stays in place, or in their orbit; which by their doing so, negates Newton’s laws of motion and gravitational certainty. Quantum mechanics measures the wave of gravitational light to explain why it stays in its orbit, which can not be explained by the classical laws Newtonian electromagnetism.
When combining these two disciplines’; the laws of the physical universe; Newtonian logic, to explain that the forces of electromagnetism, our static solar system, in relation to the galaxy, all should remain stationary and measurable. It is not, planets’ expand and collide. What Quantum mechanics tries to answer is that measurable prediction; as measured in gravitational light electromagnetism to predict what and where in the void, an electron or planet would appear base on its light wave’s gravitational signature.
The unity of these two, Quantum mechanics and classical mechanics, leads us to wave particle duality, a theory in which the particle and the wave is neither one, nor the other.
It gets technical from here and it is where Einstein Theory of Relativity begins.
Is anyone interested?
charlietwo
10-01-2008, 01:51
If it weren't 0250, I would consider pondering some of the points in this article, but I'll hold it off for tomorrow morning as I love this kind of stuff.
The real question that I know everyone else is thinking: What are all of the tortoises who hold up the world standing on? :confused:
Kyobanim
10-01-2008, 04:18
I just want to know one thing. . .
Where's my warp drive?
Hi Penn,
I read your post on Quantum Mechanics in relation to GR. It seems you captured the general gist. The qualm I am having is with Variable Light Speed. Now, I read the article you posted by Jo˜ao Magueijo. With VLS there are major causality issues which he never addresses a solution to. In fact he ends his essay stating the causality issue and leaves it at that.
The author even mentions in his premise that there has been no observable evidence in support of VLS as of yet. I skimmed over the math, as I am by no means an expert mathematician, especially when it comes to physics. I will be shooting my friend who is a Nuclear Engineer with NASA this link to see what he thinks of it.
I hope it is realized that VLS would mean that our Universe is far older than our present estimates as Parallax would be extremely scewed. I for one would love VLS to be possible, unfortunately though our observation of light and how it functions has yet to provide merit to VLS.
Just my 2 ever-devaluating cents
GratefulCitizen
10-01-2008, 07:45
The author even mentions in his premise that there has been no observable evidence in support of VLS as of yet. I skimmed over the math, as I am by no means an expert mathematician, especially when it comes to physics. I will be shooting my friend who is a Nuclear Engineer with NASA this link to see what he thinks of it.
I hope it is realized that VLS would mean that our Universe is far older than our present estimates as Parallax would be extremely scewed. I for one would love VLS to be possible, unfortunately though our observation of light and how it functions has yet to provide merit to VLS.
Magueijo's statements in 2.1 and 2.3 address the point I was trying to make.
(c being constant throughout history is an assumption)
Concerning the lack of observable evidence in support of VLS:
This does not logically lead to the conclusion that VLS is invalid.
To conclude that VLS is invalid would be a case of denying the antecedent.
That being said, I am not necessarily a proponent of VLS.
Rather, I am an opponent of the constant addition of assumptions in support of a given theory.
All theories, studies, and thought neccesarily begin with some sort of assumption or assumptions.**
From there, experimentation, observation, and logic lead to conclusion.
Whenever popular cosmology theories run into problems (or refutations of the desired conclusion), rather than revisiting the root assumptions, the problems are usually addressed by tacking on another assumption.
(Dark matter, dark energy, Oort cloud, etc...)
"Evidence" supporting these new assumptions is inferred rather than observed.
Logically speaking, this is a case of affirming the consequent.
Eventually, these additions start to bear a strong resemblance to Skinner's constant.
Occam's razor is a useful tool.
Maybe it's time apply it and revisit some of the base assumptions.
-My relative .02
**
Consider the case of Euclidean geometry.
5 basic assumptions:
1. A straight line can be drawn between any two points
2. A finite line can be extended infinitely in both directions
3. A circle can be drawn with any center and any radius
4. All right angles are equal to each other
5. Given a line and a point not on the line, only one line can be drawn through the point parallel to the line.
For 2000 years, various people tried to prove the 5th assumption from the other 4.
Euclid's genius was in recognizing that it had to be assumed.
In the last 200 years, different geometries (all logically consistent) have been constructed by changing some of the assumptions.
Ironic to this thread, replacement of the 5th assumption lead to the development of hyperbolic geometry, useful in relativity.
For those of you reading this thread, I brought this along to help out.
Help yourselves.
Red Flag 1
10-01-2008, 08:13
For those of you reading this thread, I brought this along to help out.
Help yourselves.
Just a couple now, and a couple for later. :D
All this on top of the financial mess...............Hell, give me the whole bottle!!
RF 1
RF 1
Doc Z and Grateful prove your question, or your point. I hate wasting my time. If your are serious, I have a few question you can help me explore; as we are way pass a+b=c.
Newton’s laws state that an object remains in place until a force acts on it; and once acted on, will remain in motion until a net force of equal quality acts upon it.
We know this in theorem as: “for every action there is an equal and opposite reaction”, but what it really defines is inertia, which is the resistance of an object to a change in its state of motion, or rest, along a straight line. Its one of the founding principles in classical physics use to define motion, time, speed and force; elegantly stated as time divide by distance equals speed, or the impact of a Barrett 50 cal round on a rag head at 1000 yards is a finite calculation responding to acceleration provided by grain load (force) vs. gravity, weight, and wind.
In a vacuum the round continues along its path unimpeded. Replace the word round with the word light and the question is: what of objects held in electromagnet space, or in the static balance caused by the electromagnetism, that’s moving in constant speed as measured in distance by the speed of which light travels’ . Are they moving through the vacuum of space at a constant speed relative to the measurements of other bodies within the static balance, or are they only relative to the speed of each others within the static balance confine as measured. Additionally, in which direction are they, or are we moving, as measured by light, relative to our position in the galaxy.
If we can explore these few question we should be able to contemplate where it will lead next in our discussion; if you can't, I'll sign off as I have other things to do.
Penn,
I seem to have made a mistake. I was making a response to GratefulCitizen's reference to VLS and seem to have unwittingly addressed you. Kind of brain fried on that one I suppose.
I understand your point. You are utilizing GR to question the very nature of C. I have never thought of FOR (Frame of Reference) in relation to our perception of Light Speed. GR clearly states there is no "Ultimate FOR" which would lead one to question the very notion of the "Constant" of light speed. Mathematically though we come to causality issues.
I need to ask what would cause you to compare an object with a "Rest Mass" (such as a projectile) to a photon. It does provide an illustration of the particle moving, but one may erroneously apply Newton's Laws to the scenario when there is no Rest Mass.
Grateful Citizen,
I think there is a misunderstanding of how cosmology operates. Dark Energy and Dark Matter are abstract names for things we have little knowledge of. We see the effect being caused and know from observation that what we know to be out there is not enough. I don't think any reputable cosmologist has come out and stated the nature of these exotic elements.
As I am sure you know, we are in the infancy of cosmology and physics as of right now. We have no idea what happened prior to 1 Planck time. We can't discern anything as the Laws of Physics did not exist as they breakdown within a singularity. I can imagine though that in 200 years humanity will be looking back at us much the same as we look back to the status quo broken by Galileo in his time.
All in all I would rather see cosmologists sticking their bare rear ends into the peer-review system, than give up hope of discovery. I mean, how many times did it take Thomas Edison to complete his famous pet project?
-Doc Z
Team Sergeant
10-01-2008, 09:27
I don’t believe we could discuss just one issue when it comes to "space" and arrive at any conclusions.
http://www.space.com/scienceastronomy/080930-st-universe-void.html
If you’re really interested in this stuff (as I am) go and read everything Clara Moskowitz has written at Space.com. The more pieces added to the puzzle allows for a better understanding of individual articles.
Also visit this page: http://public.web.cern.ch/public/en/LHC/LHC-en.html
And find out what scientists are doing to answer questions relating to particle physics.
“There are many theories as to what will result from these collisions, but what's for sure is that a brave new world of physics will emerge from the new accelerator, as knowledge in particle physics goes on to describe the workings of the Universe. For decades, the Standard Model of particle physics has served physicists well as a means of understanding the fundamental laws of Nature, but it does not tell the whole story. Only experimental data using the higher energies reached by the LHC can push knowledge forward, challenging those who seek confirmation of established knowledge, and those who dare to dream beyond the paradigm.”
http://public.web.cern.ch/public/en/LHC/LHC-en.html
I was using it as an introduction example; implying if you will the basic's of S/T=D in oder to simpify and to later introduce Mass; as it applies to and reacts to force and energy.
That said, by walking through the axioms, step by step, or historically proven, they would leads us back to the original article on the space bubble. It is my uneducated view, that by doing so, we could reach a point of defining our understanding and place just a little bit better.
GratefulCitizen
10-01-2008, 09:50
Grateful Citizen,
I think there is a misunderstanding of how cosmology operates. Dark Energy and Dark Matter are abstract names for things we have little knowledge of. We see the effect being caused and know from observation that what we know to be out there is not enough. I don't think any reputable cosmologist has come out and stated the nature of these exotic elements.
As I am sure you know, we are in the infancy of cosmology and physics as of right now. We have no idea what happened prior to 1 Planck time. We can't discern anything as the Laws of Physics did not exist as they breakdown within a singularity. I can imagine though that in 200 years humanity will be looking back at us much the same as we look back to the status quo broken by Galileo in his time.
All in all I would rather see cosmologists sticking their bare rear ends into the peer-review system, than give up hope of discovery. I mean, how many times did it take Thomas Edison to complete his famous pet project?
-Doc Z
Understood.
Just a little frustrated at the idea of "let's assume it's there" and then move forward.
Why not consider each case based on its own set of assumptions?
Why not consider the possibility that it's not there and see what that implies?
Concerning the causality issue, do the theories used in calculating this dilemma assume that the speed of light is constant?
If so, it is a case of circular reasoning.
*******
*******
In a vacuum the round continues along its path unimpeded. Replace the word round with the word light and the question is: what of objects held in electromagnet space, or in the static balance caused by the electromagnetism, that’s moving in constant speed as measured in distance by the speed of which light travels’ . Are they moving through the vacuum of space at a constant speed relative to the measurements of other bodies within the static balance, or are they only relative to the speed of each others within the static balance confine as measured.
According to special relativity:
The speed objects move cannot exceed the speed of light.
Light will be observed as moving the same speed, regardless of the frame of reference.
The observed speed of a non-light object depends entirely upon the frame of reference.
Various independent bodies can be observed as moving in a certain way (and at a certain speed) relative to a given frame of reference.
How they are moving relative to each other (and their speed) will change if the frame of reference is changed.
Additionally, in which direction are they, or are we moving, as measured by light, relative to our position in the galaxy.
Unsure what you mean by "as measured by light".
But, for an example:
Suppose there is a spaceship flying at 70% the speed of light, as observed by you while standing on planet Earth.
The spaceship fires a round from its forward-mounted trusty relativistic M2 Browning.
The bullet flys out of the bore at 80% the speed of light, as observed by the crew on the spaceship.
Down on Earth, the bullet appears to be going about 96% the speed of light.
(.7c + .8c) / (1 + ((.7c * .8c) / c^2) ) = .96c
Not sure if that's what you were looking for, but it's a start.
ZonieDiver
10-01-2008, 10:13
I just want to know one thing. . .
Where's my warp drive?
Warp drive...??? I'll settle for the "flying car" I was promised in 1961!
I believe your example is incorrect. As a shot from a forward gun position would only be measured in ft/per second, while your craft is moving in light speed at 186.000 miles per second. Therefore, if the bullet is fired, relative to its speed, it remains in the bore never exiting. The next round fired implodes the gun and your craft explodes.
Prove your math.
I believe your example is incorrect. As a shot from a forward gun position would only be measured in ft/per second, while your craft is moving in light speed at 186.000 miles per second. Therefore, if the bullet is fired, relative to its speed, it remains in the bore never exiting. The next round fired implodes the gun and your craft explodes.
Prove your math.
The M2 is traveling at the same speed as the ship, the round at the same speed of the M2. When fired the bullet will be travelling at ship speed plus it's generated muzzle velocity.
Reminds me of the "Can an aircraft take off if it's wheels........" Ah, lets not go back there.
I will try to explain what I think this article had to say in a more redneck way of understanding. Cause I don’t know anything about A+B=C
You ever go to the pond and put a stick in the water and it looks like the bottom part of the stick is in a different place then the top part.
well that’s what I think this dark matter is doing. And the dark matter is only around objects that have mass and gravity, we can’t measure that dark matter or see it yet, but once you get any distance away from the mass and gravity all that is in space is dark energy, the opposite of light.
So what is happening when light leaves a sun some place in the galaxy its passes threw the dark matter where it came from and then travels to us and passes threw our dark matter causing the light to look different just like the stick in the pond.
Pete, you are correct in that the M2 is moving with the ship at light speed.
The bullet, once charged, is not. It is only moving at the speed of its internal force; in feet per second, not miles/per second. Also, the force of wind on the bore retards any projection. In fact, the charge is negated by the external forward (force) movement of the ship.
S X T = D
SS1706 is moving @ 186,000 miles per second X 60 seconds = 11,160.000 Miles of space traveled
The bullet once fired is traveling at 2386 ft/per second X 60 seconds= 143,220 ft of spaced traveled.
To convert to miles 143,200 ft / 5286 ft in a mile = 27 miles +/- of spaced traveled.
The difference is that the wheels are attached to the plane. Here the internal force of the cartridge is independent of the speed and force of the Starship.
The bullet does not gain force because it is traveling inside a gun mounted in the forward section of SS1706
In order for it to be effective it must be project with a greater force than the speed of the ship which fires it.
GratefulCitizen
10-01-2008, 21:38
I believe your example is incorrect. As a shot from a forward gun position would only be measured in ft/per second, while your craft is moving in light speed at 186.000 miles per second. Therefore, if the bullet is fired, relative to its speed, it remains in the bore never exiting. The next round fired implodes the gun and your craft explodes.
Prove your math.
The inverse Lorentz velocity tranformation is applicable to my stated example:
Definitions:
u = velocity observed by an observer independent of the motion of the spacecraft and bullet
u' = velocity of the spacecraft relative to the independent observer
v = velocity of the bullet relative to the observers on the spacecraft
c = speed of light (983,571,056 ft/sec)
The transformation:
u = (u' + v) / ( 1 + ((u'*v) / (c^2)) )
u = (.7c + .8c) / ( 1 + ((.7c * .8c) / (c^2)) )
u = .9615384615 c = 945,741,400 ft/sec
This is a frame of reference issue, which is at the core of relativity.
If the spacecraft is considered the frame of reference, the bullet would appear to be going 80% of the speed of light in one direction away from the spacecraft while the Earth would appear to be going 70% of the speed of light in the other direction away from the spacecraft.
Your statement assumes a universal fixed frame of reference.
In a vacuum the round continues along its path unimpeded. Replace the word round with the word light and the question is: what of objects held in electromagnet space, or in the static balance caused by the electromagnetism, that’s moving in constant speed as measured in distance by the speed of which light travels’ . Are they moving through the vacuum of space at a constant speed relative to the measurements of other bodies within the static balance, or are they only relative to the speed of each others within the static balance confine as measured. Additionally, in which direction are they, or are we moving, as measured by light, relative to our position in the galaxy.
Chef Penn, isn't this addressed by the Lorentz transforms of space-time? If so, the physics seem to be undefined, since the equations require division by zero. Perhaps even more interesting is the implication of speeds greater than light, which are not prohibited by the equations - instead, the sqrt of a negative value produces imaginary numbers, which might be interpreted as a direction orthogonal to the 4 dimensions addressed in the transforms.
LINK (http://en.wikipedia.org/wiki/Special_relativity#Reference_frames.2C_coordinates _and_the_Lorentz_transformation)
With respect to our motion, is this addressed by the cosmic background radiation experiment?
Velocity relative to CMB anisotropy
From the CMB data it is seen that our local group of galaxies (the galactic cluster that includes the Solar System's Milky Way Galaxy) appears to be moving at 627 ± 22 km/s relative to the reference frame of the CMB (also called the CMB rest frame) in the direction of galactic longitude l = 264.4o, b = 48.4o. [32] This motion results in an anisotropy of the data (CMB appearing slightly warmer in the direction of movement than in the opposite direction). The standard interpretation of this temperature variation is a simple velocity redshift and blueshift due to motion relative to the CMB, however alternative cosmological models can explain some fraction of the observed dipole temperature distribution in the CMB (see reference for one example). [33]
LINK (http://en.wikipedia.org/wiki/Cosmic_microwave_background_radiation#Velocity_rel ative_to_CMB_anisotropy)
In classical Mechanics, the acceleration of a body is proportional to the resultant force acting on it, 2nd law of Newton….
I think we have a bit of apples (Classical Mechanics) and oranges (Quantum). The question is based in/on Newton’s second law of classical mechanics; where force = mass X acceleration. Thanks to nmap, I think I just stumbled upon the confusion; which, if I have read it correctly, discounts the position of Lorentz in this particular incidence.
I tend to gravitate to the most simplistic form of expression in exampling ideas. This explanation is not simple, but I think it validates the CM argument that I was attempting to explore, before leaping to the quantum. At any rate, and I hate saying this, but the discussion might be more relative based of the this and it may be possible that we are all correct. However, I am uncertain of that.
The link should lead you to Relativistic mechanics
http://en.wikipedia.org/wiki/Special_relativity#Reference_frames.2C_coordinates _and_the_Lorentz_transformation
Relativistic mechanics
Main article: Mass in special relativity
Main article: Conservation of energy
In addition to modifying notions of space and time, special relativity forces one to reconsider the concepts of mass, momentum, and energy, all of which are important constructs in Newtonian mechanics. Special relativity shows, in fact, that these concepts are all different aspects of the same physical quantity in much the same way that it shows space and time to be interrelated.
Grateful,
If the spacecraft is considered the frame of reference...what if it not, if there is no reference point and craft only reference is itself?
and from the The black sheep of “varying-constant” theories my new favorite concept....
....there is a priori nothing wrong with using my pulse as the unit of
time, and rephrasing physics in “egocentric” units.
SS1706 is moving @ 186,000 miles per second X 60 seconds = 11,160.000 Miles of space traveled
The bullet once fired is traveling at 2386 ft/per second X 60 seconds= 143,220 ft of spaced traveled.......
The bullet does not gain force because it is traveling inside a gun mounted in the forward section of SS1706
In order for it to be effective it must be project with a greater force than the speed of the ship which fires it.
My brain is having a hard time with this because a bullet is a pretty stupid critter. It only knows that when the pimer goes off it starts running down the barrel and comes out the other end - the muzzle - at 2386 relative to the brass case down at the other end.
An aircraft flying at 400 mph is doing about 586 fps. If it fires the same M2 round - when the bullet is coming out of the muzzle is it travelling at 2386 fps or 2972 fps relative to the space around us?
If it is only travelling at 2386 than that means an M2 could not be fired from an aircraft travelling 1600 mph as that would be something like 2344 fps. The round would only come out at 42 fps.
I know, I know, a bullet at that speed is impractical because drag, et al - the aircraft would run right past it as it slowed down but.......
Man, and we still have not talked about recoil and it's effect in this whole thing.:D
Pete, I believe (In the relative sense) that was the exact problem when weapons were first placed in Jets.
I just sent this thread to Professor Clarke @ UPENN, hopefully he'll answer our questions.
Pete, I believe (In the relative sense) that was the exact problem when weapons were first placed in Jets.
Guns worked quite well in jets during the Korean War. What killed the gun was the Air to Air Missle and the mindset that dog fighting was a thing of the past.
Thats how we ended up with Phantoms in VN without guns trying to dog fight which lead "back" to a pod mounted gun.
I would say engagement distance had more to do with killing off guns on aircraft. Guns have became extra weight with no plus in the modern age.
But I'll try a differnt tack. An aircraft carrier is moving at 20 knots, you can jog at 10 knots and are standing in the middle of the flight deck. You jog to the bow. What was your running speed? 10 knots. Your true ground speed? 30 knots. You jog to the stern. What was your runnig speed? 10 knots. What was your true ground speed? Man, you were backing up at 10 knots.
Your actions are in relation to the flight deck not the ocean/ground. Just as the M2 reacts to the spaceship not the area outside the ship.
Maybe I'm just hardheaded but I'm seeing a space walk in my head. The astronaut and the space ship orbiting the earth. The astronaut moves to the front of the ship, places his hand on the nose and pushes off. No matter what the speed of the ship, his push (recoil) has slowed it a hair and he is now moving forward, away, from the ship just a little faster. Again, the action was to the two objects - not the space around them.
Maybe I should just go to the back of the class and wait for recess.:D
But I'll try a different tack. An aircraft carrier is moving at 20 knots, you can jog at 10 knots and are standing in the middle of the flight deck. You jog to the bow. What was your running speed? 10 knots. Your true ground speed? 30 knots. You jog to the stern. What was your running speed? 10 knots. What was your true ground speed? Man, you were backing up at 10 knots.
So, in essence, you're saying that speed depends on the reference frame of the observer. If our observer was on the Moon, we would simply add a factor for the relative motions of the Earth and Moon to your work above. That was exactly what Newtonian physics described, at least according to my understanding.
Your actions are in relation to the flight deck not the ocean/ground. Just as the M2 reacts to the spaceship not the area outside the ship.
Maybe I'm just hardheaded but I'm seeing a space walk in my head. The astronaut and the space ship orbiting the earth. The astronaut moves to the front of the ship, places his hand on the nose and pushes off. No matter what the speed of the ship, his push (recoil) has slowed it a hair and he is now moving forward, away, from the ship just a little faster. Again, the action was to the two objects - not the space around them.
Maybe I should just go to the back of the class and wait for recess.:D
Or perhaps you should go to the podium and teach the class.
Just as you say, the astronaut's actions will slow the ship in accordance with the principle of conservation of momentum. The astronaut will move in one direction at some speed, and this determines the change in speed and direction of motion for the ship.
More formally:
Third law
Whenever a particle A exerts a force on another particle B, B simultaneously exerts a force on A with the same magnitude in the opposite direction. The strong form of the law further postulates that these two forces act along the same line. This law is often simplified into the sentence "Every action has an equal and opposite reaction."
LINK (http://en.wikipedia.org/wiki/Newton's_laws_of_motion)
This leads into the issue with relativity. If instead of an airplane with a gun, what if we have a spaceship with a particle beam. The spaceship travels at 90% of the speed of light, and so do the protons from the particle beam. So - if we used a Newtonian approach, we would wind up with protons exceeding the speed of light from the perspective of some hypothetical stationary observer. That's where the Lorentz equations, nicely presented by Grateful, come in. The protons would not exceed the speed of light; rather, they would approach it.
Thus (stealing Grateful's equations)
u = (u' + v) / ( 1 + ((u'*v) / (c^2)) )
u = (.9c + .9c) / ( 1 + ((.9c * .9c) / (c^2)) )
u = (1.8c)/(1 + ((0.81c^2)/(c^2)) )
u = (1.8c)/1.81
u = 0.994c
That whole space-time continuum thing.
But what if the math is wrong somewhere? Just a small little glich somewhere that everbody assumes is correct?
That's what I like about humans. Always trying to go deeper, higher, faster than anybody else. And somebody just might come up with it.
The speed of sound came with a few bumps in the road.
Faith, ya' got to have faith. Otherwise we're stuck on this rock with no place to go.:D
But what if the math is wrong somewhere? Just a small little glich somewhere that everbody assumes is correct?
No what if's are needed. There are glitches. That's one of the "grand challenges" we face today - general relativity explains some things, particularly large things such as gravitational effects.
Quantum theory addresses the very small. But, according to my very limited understanding, general relativity does not apply at the quantum level. For example, conservation of mass may not apply to fluctuations of very short duration. Even the speed of light may not apply at the quantum level - one such effect is called "spooky action at a distance".
So the problem becomes putting the two theories together into a seamless whole - a grand unified theory.
Einstein worked on this at the end of his career and didn't come up with an answer. Others have tried, but it doesn't appear that an answer has yet been found.
Whoever gets it has a certain place in the history books....
GratefulCitizen
10-02-2008, 09:26
Maybe I'm just hardheaded but I'm seeing a space walk in my head. The astronaut and the space ship orbiting the earth. The astronaut moves to the front of the ship, places his hand on the nose and pushes off. No matter what the speed of the ship, his push (recoil) has slowed it a hair and he is now moving forward, away, from the ship just a little faster. Again, the action was to the two objects - not the space around them.
Maybe I should just go to the back of the class and wait for recess.:D
There has been a lot of mixed ideas presented in this thread.
My example was meant to be illustrative and was restricted to the idea of non-accelerating motion and special relativity.
In that example, I shouldn't have said that the spaceship "fires" its forward gun.
Rather, I should've said that the spaceship had "already fired" its forward gun.
The spaceship is going 70% of c, as observed by the guy on Earth.
The bullet (fired from its "relativistic" M2) is going 80% of c, as observed by the spaceship crew.
The illustration was meant to show that the speed of any object will remain less than c, regardless of who is observing it.
It starts to get fun when you turn on the laser sight for the M2.
Any guesses has to how fast the laser beam is traveling?
-As observed by the crew?
-As observed by the bullet?
-As observed by the guy on Earth?
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Concerning the spacewalk and the spaceship:
If the spaceship is traveling at some high speed as observed by a guy on Earth, and the spacewalker pushes off of the ship, relativistic momentum will be conserved.
Actually, relativistic momentum is conserved regardless of speed.
In classical mechanics, momentum is described: p = mv
p = momentum
m = mass
v = velocity
The relativistic momentum:
p = mv / (sqrt(1 - ((v^2) / (c^2))))
When the value of v is small compared to c, the value of that mess on the bottom approaches 1.
This means, at low speeds, it's basically p = mv.
You guys trying for one of these? (attchd jpg) :rolleyes:
Richard :munchin
You guys trying for one of these? (attchd jpg) :rolleyes:
Richard :munchin
Sir, I regret to inform you that this site has become the target of a clandestine infiltration operation. I hesitate to mention the organization behind the effort, and will restrict myself to including its symbol. :D
ZonieDiver
10-02-2008, 09:58
You guys trying for one of these? (attchd jpg) :rolleyes:
Richard :munchin
"Who ya gonna call?" Ghostbusters is the source of two of my other favorite movie lines - "A unique fixer-upper opportunity" and "you never studied".
GratefulCitizen
10-03-2008, 09:07
Sir, I regret to inform you that this site has become the target of a clandestine infiltration operation. I hesitate to mention the organization behind the effort, and will restrict myself to including its symbol. :D
Sorry Nmap, but when I look at that symbol, I can't help but think of a top-view of a Klingon Bird of Prey.
Members of that "organization" would probably take such an observation as a complement.
Sorry Nmap, but when I look at that symbol, I can't help but think of a top-view of a Klingon Bird of Prey.
Members of that "organization" would probably take such an observation as a complement.
(Chuckle) They might start talking to you in Klingon. You did click "save picture as" didn't you? That provides the name of the picture, and hence the name of the organization. You don't actually have to save the picture, but it does give the name.
If you haven't done so, you may get a laugh out of it.
GratefulCitizen
10-04-2008, 22:15
Perhaps even more interesting is the implication of speeds greater than light, which are not prohibited by the equations - instead, the sqrt of a negative value produces imaginary numbers, which might be interpreted as a direction orthogonal to the 4 dimensions addressed in the transforms.
This hit me right in the obsessive-compulsive disorder.
Been thinking about it for a few days.
From what I remember about hyperbolic geometry, an orthonormal basis will always be constructed of 2 spacelike and 1 timelike vectors.
I'm unsure of the effect on the basis that the imaginary number would have.
My intuition tells me that, in the case of a hyperbolic plane, the worst effect it could have is to change the basis to 1 spacelike and 2 timelike vectors.
This is essentially no change.
The basis in 4-space is 3 and 1.
It's hard to imagine (pun intended) how this would be disrupted.
I dunno.
The class in which I studied the hyperbolic stuff was a math class and didn't directly address relativity.
(but it did cause severe headaches)
The relativity stuff was studied in a physics class and didn't directly address hyperbolic space.
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Concerning the Klingon comments...
I do have an English/Klingon dictionary (circa 1992) buried somewhere. :rolleyes:
When digging through my library for some of the relativity stuff, I discovered an old college quiz.
The instructor required us to sketch a diagram as part of the answer (spaceships closing at relativistic speeds).
...the sketch had a Federation Constitution class cruiser closing with a Klingon D7 cruiser (it's sad that I still recognize them). :rolleyes:
That nerd gene keeps manifesting itself...
Irishsquid
10-05-2008, 00:02
Geez...and here I thought I was smart because I understand that a computer is a box full of switches, and not some magical device...the wealth of knowledge found here and on Socnet never ceases to amaze me. Keep it up guys. When I grow up, I want to be smart like you. ;);)
GratefulCitizen
10-05-2008, 15:48
Geez...and here I thought I was smart because I understand that a computer is a box full of switches, and not some magical device...the wealth of knowledge found here and on Socnet never ceases to amaze me. Keep it up guys. When I grow up, I want to be smart like you. ;);)
This stuff sounds much worse than it really is.
"Orthogonal" is basically the same idea as "perpendicular".
In 3 dimensions, you have an x, y, and z axis; all of which are perpendicular to each other.
In 4 dimensions, there is another axis which is "perpendicular" to the other three.
It's not really meant to be visualized, but the mathematics work.
In the case of spacetime, the math doesn't work exactly like it would in a regular 4 dimensional space.
Things get "bent" or "warped".
To visualize the bending of a 2-dimensional surface is relatively (pun intended) easy.
We do it all the time with the surface of the earth.
A flat map is a bent/warped version of a curved surface.
Trying to visualize bends/warps in these greater dimensions is another matter.
It's difficult to understand this stuff because our brains work too well, not because they don't work well enough.
Our brains readily recognize patterns and how they relate to one another.
This is all grounded in what our senses perceive in the world around us.
However, the human mind also has the ability to operate "offline" and consider things which have never been actually perceived by senses.
Can you imagine and describe a unicorn?
Have you ever seen one?
In the case of mathematics, there are things which can only be described abstractly, have no good real world analogies, and cannot be easily visualized.
There's a book by Keith J. Devlin (The Math Gene) which addresses this idea of "abstraction" quite well.
It's a good read and doesn't require a math background to understand.
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Some other odds and ends...
"Imaginary" numbers is a bit of a misnomer.
They're just numbers.
Consider the number "0".
How many is that? Can I show you "0" of something?
There are also the integers...how many is "-3"?
The rational numbers work a little better. 2/3 of a pie is pretty obvious.
Irrational numbers (like the square root of 2) seem like they're easy to understand.
This is only because the notation has been popularly accepted.
It is rumored that, upon the discovery of the irrationals, the Greeks found this concept so disturbing that they tried to suppress the knowledge.
It the case of "imaginary" numbers, it just involves the square root of a negative number.
The numbers work just fine and are useful in fields such as electrical engineering.
The better term for these is "complex" numbers.
They basically act like a 2-dimensional measurement, whereas "regular" numbers are 1-dimensional.
"Spacelike" and "timelike" vectors are just naming conventions.
A "vector" is basically just a certain distance in a certain direction.
The names have to do with particular properties of a given vector.
Many members of this site are familiar with the idea of the "dot product" (also known as the "inner product").
This is what you use to calculate the effective range when shooting uphill or downhill.
A similar idea exists in hyperbolic geometry, called "bilinear form".
The bilinear form of a vector with itself will result in a number.
If this number is > 0, the vector is "spacelike".
If this number is < 0, the vector is "timelike".
(and if the number = 0, it's "lightlike")
What an "orthonormal" basis means:
It's basically just like an x, y, and z axis.
In the case of hyperbolic geometry, two of these axis have to be "spacelike" and one "lightlike" in order for them all to be "perpendicular" to each other.
In the case of 4 dimensional hyperbolic space, it's 3 and 1.
(again, all 4 are "perpendicular" to each other)
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It does take time and study to get into the nitty-gritty of this stuff.
While visualizing the whole may well be impossible, understanding each of the pieces isn't too difficult if you don't get hung up on the terminology.
HTH.
I sent and ask the Chair of Astrophysical Science at Princeton University, Professor David Spergel,
to weigh in on our discussion. Here is his reply.
Dear Dennis,
This is a more of a problem in special relativity than quantum mechanics.
In special relativity, the mass of an object increases the faster it is moving (as seen from our point of view). A spaceship moving at 75% of the speed of light has double its rest mass. The mass of spaceship moving at 99% of the speed of light is ten times its rest mass. It would take an infinite amount of energy for a spaceship (or a rifle) to move at the speed of light. So, let me reword your question.
Consider a spaceship moving at 75% of the speed of light away from Earth. The spaceship fires a missile that moves away from the spacecraft at 50% of the speed of light (as seen from the spacecraft). If we gave this problem to Galileo (who did military science work for the Italian Dukes), then he would have concluded that the missile would be seen to move away from us at 1.25 times the speed of light. What Einstein taught us was that we need to include
the fact that we measure the speed of an object by measuring arrival time of pulses of light. If we think about the missile send out a flash every second, an observer on Earth would find that the arrival time between pulses was not one second but over 1.3 seconds as every time the missile sends out a pulse, it is further away. Thus, as seen from the Earth, the missile would be moving at less than the speed of light. As seen from the spaceship, the missile would be moving away at close to half the speed of light.
If I reword your question and consider a bullet fired from a spaceship going at 99.999999% of the speed of light. Then, an observer on the spaceship would see the bullet leave at 2360 ft/s. However, an observer on the Earth would see it move very slowly out of the rifle as the spacecraft's motion carries both the ship and the bullet rapidly away from Earth.
This result may sound at first counter-intuitive. However, we observe these effects in the laboratory. I believe that these relativistic corrections are incorporated into GPS and effectively into missile guidance systems even for our "slow" missiles.
If you and your readers are interested in delving into special relativity, I would recommend Space time Physics by Taylor and Wheeler or the "Fabric of the Cosmos" by Brian Greene.
Sincerely,
David Spergel
Thank you, Chef Penn!
Those sound like interesting books...
What force acts on the object to increase its mass as it approaches c?
I love this stuff but it is like trying to read the mind of God.
Guys, Guys,, Less coffee and more sex,, You'll live longer.. :D
Irishsquid
09-02-2010, 02:27
Do you mean our brains ARE powerful enough...?
Work in cryptography for a while...you'll understand how powerful the human brain really is. And yes...I believe our brains ARE simply too streamlined to understand some things. We don't understand some things on a qualitative level, simply because qualitative, by definition, means a number can't be applied. Qualitative descriptions are "big," "small," etc. Our brains are too streamlined for that. We understand "6 ft. tall," "3 ft. long," "15 lbs," etc.
If you ever doubt the power of the human mind, think about the work your brain does to understand something as simple as the number 1,024.
4X10^0 + 2X10^1 + 0X10^2 + 1X10^3
4 + 20 + 0 + 1000
1024.
All that math is done so quickly that your brain knows 1024 so quickly you don't even know you've done the math. Pretty amazing.
Your brain processes all of that so fast you don't even know it's happening. After working with it for a while, you realize that almost all number systems work the same way...and that with sufficient exposure, you can become almost that efficient when dealing with binary, hexadecimal, octal...whatever. The human brain is immensely powerful, from a standpoint of pure logic and math. Where we are weak is with descriptive, qualitative, or emotional arguments.
Dozer523
09-02-2010, 06:58
4X10^0 + 2X10^1 + 0X10^2 + 1X10^3
4 + 20 + 0 + 1000
1024.
All that math is done so quickly that your brain knows 1024 so quickly you don't even know you've done the math. Pretty amazing.
I don't think my brain conceives a number in it's exponential state (otherwise we shouldn't have to teach kids exponents)
I think it is more like this"
@ = a beer
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@@@@@@@@@@ @@@@@@@@@@ @@@@ = 1,024 (man that's a lot of beer!)
GratefulCitizen
09-02-2010, 19:35
That's interesting, but not sure I agree; for one, humans seem far more driven by emotions than logic, right? Also, when people think of a number like 1,024, I don't think your brain actually does any calculations. It is just a number. If I think 2,000,000, again I'm not doing any calculations. And I can't per se visualize two million, it is just a number.
Driven by emotions?
That is the difference between animals and humans.
There is a "gap" between stimulus and response where we get to choose.
Moral responsability.
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Don't need to visualize 2,000,000.
That's why we have numbers.
. = 1
.. = 2
... = 3
etc.
2 groups of ... ... ... . = 20
Symbolic logic takes the place of visualizing things which are too difficult or impossible.
Ironically, symbolic logic can show that there are ideas which cannot be represented by symbolic logic.
There are many adults who I've taught algebra in a few short lessons.
The problem they ran into during their schooling was usually confusion resulting from the use of letters when algebra is taught.
The symbols used are irrelevant.
Smiley faces, frowny faces, and arbitrary squiggles work the same as letters.
The problem is that letters already have meaning.
It's a case of the brain working too well, rather than not well enough.