Space, Time, The Expanding Universe, and the Speed of Light

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KurtVonFritz

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Everything can be manipulated, the idea here is to start thinking on the manipulation itself, any insights on ultrahigh frequencies of ulterasound that can manipulate almost anything? i use it right now to make stuff "old", and it passes all scierntific tests, however precise guided action from multiple ultrasonic sources is what i think may become the right thing to do ... a single ultrasound emitter is able to move a single atom to a single defined location, or just change the state of another atom to the state of this one, this is also the key to "teleportartion"... interested in that? i would need help since I am working on some project here already.
 
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atlantisworp

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Time is just another name for dynamics. Who can stop motion can also stop time.
 
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Boilermaker

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atlantisworp":2rg67oy5 said:
Time is just another name for dynamics. Who can stop motion can also stop time.

I think that's partially right, whoever can stop the motion of space expansion can stop time.........I believe time to be the expansion of space, not motion in space. If there were no matter nor energy in space yet space were expanding I believe we would have time still, which should tell you, time is the expansion.

there was no time until the universe began to expand. there had to be at least one event as there was some "thing" which expanded bringing about our universe, space and time. So, the "thing" formed in some period when there was no time and it formed in some area where there was no space.

so time is distinct from movement within space and space is distinct from the area which the "thing" initially occupied, as small as it may have been it occupied an area. in the "area" there was a "thing" which existed without space or time existing as space and time were the result of the expansion of this "thing" which occupied an "area" from which space arose.

so, obviously, things can exist and happen without space or time to exist and happen in.
 
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KurtVonFritz

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I get the feeling that most guys here are some govenment agency prepaid clerks aiming to just fill up space and hide the truth with general bla-bla here...
 
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KurtVonFritz

Guest
After reading all the answers to my posts, i am definitely out of here. No bad feeling, guys, i am in some easterneuropean country anyway so good luck finding me.
 
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Boilermaker

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KurtVonFritz":1l3tn195 said:
After reading all the answers to my posts, i am definitely out of here. No bad feeling, guys, i am in some easterneuropean country anyway so good luck finding me.
well, being as I was the easterneuropean hide and seek champion your as good as found.....I'll be time traveling to a location near you instantaneously.......almost.
 
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xXTheOneRavenXx

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I have to ask. According to all the theories I have read, the speed of light cannot be exceeded. Now with the latest developments in technology, we may be able to be propelled to orbit via a laser beam (beam of light). If a beam is propelling a craft, does this mean the craft will essentially be moving at the speed of light?
 
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ramparts

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xXTheOneRavenXx":2512gjjb said:
I have to ask. According to all the theories I have read, the speed of light cannot be exceeded. Now with the latest developments in technology, we may be able to be propelled to orbit via a laser beam (beam of light). If a beam is propelling a craft, does this mean the craft will essentially be moving at the speed of light?
Good question! No, that wouldn't necessarily propel a craft anywhere near the speed of light, and for the same reason that if I pitch a fastball to you at 100 mph, you won't get flung back at 100 mph. When things collide, what's conserved is total momentum, which is speed times mass. So even if the baseball (or light) transfers all its momentum to whatever it collides with, if the other object is more massive, it won't travel as fast. And remember - light is massless! ;)
 
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xXTheOneRavenXx

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That was my next question, how can without mass move something WITH mass?
 
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ramparts

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Essentially, because light carries energy, and transfers that energy in collisions. More specifically, as I said, photons have momentum, which depends partially on mass, but has another component as well, which depends on energy. So light has no mass, but does have momentum, and that gets transferred in the collision.

If you're comfortable with a little bit of (pretty simple) math, there's a good description on Wiki:

http://en.wikipedia.org/wiki/Photon#Physical_properties

The full version of Einstein's E = mc^2 for a moving object (i.e. one with momentum) is:

E^2 = m^2 c^4 + p^2 c^2

Where p is momentum. So when p = 0 (an object is at rest), we have E^2 = m^2 c^4, or E = mc^2. In the case of light, however, p is non-zero but m is 0. So instead the energy becomes:

E^2 = p^2 c^2, or plain ol' E = pc

We know how to calculate the energy of a photon (the formulae are on the same page - it depends on the wavelength or frequency of the light), so once we have that, we just divide the energy by c, and find the momentum.

Of course, if you do the math, you'll find that even high energy light inelastically colliding with a massive body at rest won't move it very much at all ;)
 
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csmyth3025

Guest
It may be a bit late to add to this thread, since the last post was Aug 1. On the off chance that anyone is still monitoring it, I'd like to submit this conjecture/question:

General Relativity predicts that time for an object that's in a stronger gravitational field ticks slower than time for an object that's in a weaker gravitational field. I believe this prediction has been confirmed by a number of experiments, e.g. an experiment using atomic clocks - one on the ground and one in an aircraft on a long endurance, high altitude flight.

Our current universe is much more spread out than the early universe and, thus, the intensity of the gravitational field of all the "stuff" of the universe is correspondingly weaker than it was early on when it was all gathered together in a much smaller volume. (This is an intuitive guess on my part, so correct me if I'm wrong about it)

My conjecture/question comes as an outgrowth of a very good book I read almost 30 years ago entitled "The First Three Minutes" by Steven Weinberg. The book essentially describes the processes that occurred during the first three minutes after the Big Bang.

I'm wondering if the time period described in the book - albeit valid according to the watch of a scientist living at that time - might be considerable longer according to the watches of our present day universe, by virtue of the fact that we live in a much weaker gravitational field. For instance, if we could somehow view the first three minutes (as timed by a scientist who was "there") would we find these events unfolding over the course of 3 million years by our present day watches?

I think this line of inquiry fits into the "constancy of time" question in the original post.

Chris
 
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csmyth3025

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Ramparts wrote:
"...If you're comfortable with a little bit of (pretty simple) math, there's a good description on Wiki:

http://en.wikipedia.org/wiki/Photon#Physical_properties

The full version of Einstein's E = mc^2 for a moving object (i.e. one with momentum) is:

E^2 = m^2 c^4 + p^2 c^2

Where p is momentum. So when p = 0 (an object is at rest), we have E^2 = m^2 c^4, or E = mc^2. In the case of light, however, p is non-zero but m is 0. So instead the energy becomes:

E^2 = p^2 c^2, or plain ol' E = pc ...."

I can only say that regarding the linked article, your ideas and my ideas about what constitutes "pretty simple math" are light years apart. (Sorry, I couldn't resist the temptation of using that descriptive term in this context)

Still, I'm able to grasp the concept of energy having momentum. This brings me to my question about a classic "toy" that demonstrates (I believe) this principle. I can't recall the name given to this device - it's a simple paddle wheel balanced on a needle-like shaft and contained in an (evacuated?) glass bulb. The paddles are painted black on one side and white on the other.

When this device is exposed to light (e.g. sunlight) the paddle wheel rotates in a direction opposite the black-painted side of the paddles (I think). If my understanding about the direction of rotation is incorrect, please let me know.

My question is this: Is the rotation caused by simple heating of the black-painted side of the paddles which, in turn, heats the air molecules adjacent to that side which, in turn, "pushes" against the paddle by virtue of their more energetic (heated) motion? Or, is this action a result of the the black-painted side of the paddle absorbing more energetic photons (white light) and emitting less energetic photons (infrared light) while gaining the "momentum" represented by the difference in the energy levels of the adsorbed and emitted photons.

The reason I ask this question is that I speculate that light is absorbed and emitted by both the white sides and the black sides of the paddles. I'm guessing that the white sides would be mirrored surfaces if they just reflected light. This absorption/emission scenario presents two possibilities, as far as I can figure out. One possibility is that the light emitted by the white side is visible (white) light which doesn't heat up the adjacent air molecules as efficiently as the infrared light emitted by the black side. This could result in a "pressure differential" with the lower pressure (of the cooler air molecules) being on the white side and the higher pressure (of the heated air molecules) being on the black side.

The other possibility I see is the gain in "momentum" I described in the paragraph above. The question of which of these two possibilities is the mode of operation would be settled if the device was enclosed in a true vacuum, of course.

I'm sure there's a good explanation of this effect in an article or book somewhere - the problem is that I can't remember what the darn thing is called.

Chris
 
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ramparts

Guest
csmyth3025":174xtdho said:
Ramparts wrote:
"...If you're comfortable with a little bit of (pretty simple) math, there's a good description on Wiki:

http://en.wikipedia.org/wiki/Photon#Physical_properties

The full version of Einstein's E = mc^2 for a moving object (i.e. one with momentum) is:

E^2 = m^2 c^4 + p^2 c^2

Where p is momentum. So when p = 0 (an object is at rest), we have E^2 = m^2 c^4, or E = mc^2. In the case of light, however, p is non-zero but m is 0. So instead the energy becomes:

E^2 = p^2 c^2, or plain ol' E = pc ...."

I can only say that regarding the linked article, your ideas and my ideas about what constitutes "pretty simple math" are light years apart. (Sorry, I couldn't resist the temptation of using that descriptive term in this context)
:) Well, this is really just high school algebra - so when I say simple, I mean simple relative to the rest of the math you'll find in physics. Calculus, for example, or worse off, the differential geometry of general relativity or (heavens forfend!) the mess that is quantum mechanics!

Still, I'm able to grasp the concept of energy having momentum. This brings me to my question about a classic "toy" that demonstrates (I believe) this principle. I can't recall the name given to this device - it's a simple paddle wheel balanced on a needle-like shaft and contained in an (evacuated?) glass bulb. The paddles are painted black on one side and white on the other.

When this device is exposed to light (e.g. sunlight) the paddle wheel rotates in a direction opposite the black-painted side of the paddles (I think). If my understanding about the direction of rotation is incorrect, please let me know.

My question is this: Is the rotation caused by simple heating of the black-painted side of the paddles which, in turn, heats the air molecules adjacent to that side which, in turn, "pushes" against the paddle by virtue of their more energetic (heated) motion? Or, is this action a result of the the black-painted side of the paddle absorbing more energetic photons (white light) and emitting less energetic photons (infrared light) while gaining the "momentum" represented by the difference in the energy levels of the adsorbed and emitted photons.

The reason I ask this question is that I speculate that light is absorbed and emitted by both the white sides and the black sides of the paddles. I'm guessing that the white sides would be mirrored surfaces if they just reflected light. This absorption/emission scenario presents two possibilities, as far as I can figure out. One possibility is that the light emitted by the white side is visible (white) light which doesn't heat up the adjacent air molecules as efficiently as the infrared light emitted by the black side. This could result in a "pressure differential" with the lower pressure (of the cooler air molecules) being on the white side and the higher pressure (of the heated air molecules) being on the black side.

The other possibility I see is the gain in "momentum" I described in the paragraph above. The question of which of these two possibilities is the mode of operation would be settled if the device was enclosed in a true vacuum, of course.

I'm sure there's a good explanation of this effect in an article or book somewhere - the problem is that I can't remember what the darn thing is called.

Chris
I'm unfamiliar with that sort of thing, but my guess would be that the paddle would rotate as if you were pushing the black side, since the black side would absorb photons, and their associated momenta, while the white side would just reflect them. That said, it would take a LOT of photons to noticeably move an object just by transferring momentum, so there's likely something more subtle at work - any of the things you mentioned are probably possibilities!
 
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csmyth3025

Guest
Well, shucks.

After writing that rather lengthy post - a vague, long-forgotten memory popped into my head. On a hunch I typed "radiometer" in the Wikipedia search box and, sure enough, an excellent article on Crookes Radiometer came up:
http://en.wikipedia.org/wiki/Crooke%27s_radiometer

It seems that "radiation pressure" is definitely not the mode of operation of this device. I found some comfort in the fact that, according to the article, others were at first unsure about it in the same way that I was and "...This explanation [light pressure] is still often seen in leaflets packaged with the device...".

On the other hand, "radiation pressure" is a valid concept with potentially practical applications - as I found in another Wikipedia article here:
http://en.wikipedia.org/wiki/Solar_sail

Hmmm.... I wonder if there's a "forum etiquette" rule against answering your own posts.

Chris
 
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Tuora

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Space.com post Aug 30 2009 – Tuora

My view of the arrow of time may be more straightforward, I hope. Time exists ONLY in an expanding universe as an intrinsic part of the whole, the 4-th dimension. Conversely, in a black hole, time stands still, swallowed by the gravity of the black hole.

The Big Bang was the time when time begun, right along with the three-D universe. What triggered the Big Bang nobody knows, and I will stop at this junction. We do have several known facts to corroborate Big Bang event and what has followed since.

1. Background radiation at the temperature 2.725° above absolute zero to fix the beginning of time. http://map.gsfc.nasa.gov/universe/bb_tests_cmb.html
2. Hubble constant, http://www.universetoday.com/2006/08/08 ... -constant/
3. Hubble linear chart of distance (X axis) and velocity (Y axis) indicate the universe expanding at an even rate. That demands presence of force acting throughout universe in the real time of the universe. (Big bang alone, once exploded, would merely let the universe coast expanding along at a constant speed.) Enter Dark Matter and Energy, point 4 http://74.125.95.132/search?q=cache:ty- ... clnk&gl=us
4. Dark Matter and Energy: http://www.space.com/scienceastronomy/0 ... nergy.html “Astronomers estimate now that out of the total mass-energy budget in the universe, about 74 to 76 percent is dark energy, 20 to 22 percent is dark matter and 4 percent or so is normal matter that makes stars, planets and everything we see. And they know that some "force" is causing galaxies to fly away from one another, operating like antigravity.” Note: 75% of dark energy is the cost of creating time for the 4% of “normal” universe we are trying to decipher from within. Time is expensive, but without time to be, nothing is.

-For the sake of clarity, let us exclude the supernatural influence, which does nothing but super-elevates the answer to the wisdom unknown.

So where is the “deus ex machina”, the magic formula to make Universe be?
-Could it be so simple we cannot conceive of it, assuming it must be complex ?
If it were too complex, involving other inputs to make it work, it would not work for Universe to ever be.

We do know the total energy of the Universe is exactly Zero, and the only way to make it work is to fully account for it. Tune in next time. Tuora.



[The expansion of the universe happens over time. As the distances increase, they are moving in a timelike direction. As such, it makes no sense to talk about time expanding or speeding up.]


MeteorWayne said:
As far as we have been able to demonstrate. the speed of light is fixed. For the moving observer, the passage of time does not change; it only changes when observed by someone at a different rate of speed. For the person or object moving at any speed, time for them (or it) passes at the same rate.]
 
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Tuora

Guest
The constipated format of this forum favors well-stablished idiosincrasies of the inhabitants.
Not sure there is much left here, but listen without comment.
 
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Tuora

Guest
I am waiting for a resonable continuation of my thread. This site is difficult to navigate, though some have exploited it to prevaricate in terms of dominating the forum for their own sundry reasons. Failing any intelligence coming back, I conclude this forum has been left for maggots to thrive.

Tuora.
 
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MeteorWayne

Guest
Listen, this is not an IM site. It is a board where people get to read and respond as they read the material, and they wish to respond. If that doesn't fit your expectations, you can go elsewhere.

BTW, it's not your thread, the discussion started about 3 months ago. So stop whining, and participate or not as you wish.

Welcome to Space.com!
 
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Olib1990

Guest
Hey everyone im new to this forum, i have just been reading "A breifer history of time" and came along a section about the universe expanding. I understand how space-time is explained using a rubber sheet and where you place objects on it, it creates a dip and other objects get dragged in. So when reading about the universe not only expanding but speeding up! I thought perhaps this could be explained in the same way but flipped over...... What if the centre of the universe is at the top of a giant theoretical mountain in space time, and the surrounding universe is "falling" down what you would call a giant mountain and gravity is not strong enough to stop it falling. Then as everything gets further and further down the "mountain" gravity is getting weaker and weaker and thus the objects move faster and faster.

I dont know how possible this is but it seems in no way different to the earth sat in space-time and things falling in, just on a universal scale.

What do you think?

Thanks :)
 
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csmyth3025

Guest
Olib1990":3qfs9dg8 said:
Hey everyone im new to this forum, i have just been reading "A breifer history of time" and came along a section about the universe expanding. I understand how space-time is explained using a rubber sheet and where you place objects on it, it creates a dip and other objects get dragged in. So when reading about the universe not only expanding but speeding up! I thought perhaps this could be explained in the same way but flipped over...... What if the centre of the universe is at the top of a giant theoretical mountain in space time, and the surrounding universe is "falling" down what you would call a giant mountain and gravity is not strong enough to stop it falling. Then as everything gets further and further down the "mountain" gravity is getting weaker and weaker and thus the objects move faster and faster.

I dont know how possible this is but it seems in no way different to the earth sat in space-time and things falling in, just on a universal scale.

What do you think?

Thanks :)
One thing that you have to keep in mind with your hypothesis is that the currently accepted view of the expansion of the universe is not that everything is running away from some central point - as in customers of a shopping mall running for the exits when a fire alarm is set off. Rather, the large structures of the universe are remaining fairly stationary (by cosmological standards) within their own region of space. It is the space itself between these large structures that is expanding. The structures themselves are somewhat like dots on a cosmic baloon that's being blown up bigger and bigger. The structures stay more-or-less in their own "spot" in space. The apparent speed at which they are moving away from us (and from every other large structure in space) is the result of the space between these structures growing larger.

The notion that space itself may have been more concentrated in the early unverse and is "deompressing" by some mechanism that we don't yet understand is an interesting thought. If you can present this idea in a plausible theory backed up by sound, self-consistant mathematical equations you would get a lot of attention (not all good). One of the features of the "peer review" process is that experts in the field get to try their best to poke holes in your theory. It has to be pretty darn solid to stand up to this test.

Chris
 
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Mamluk

Guest
The notion of an expanding universe has its base on the precept that light travels at a constant speed in specific situations (in a vacuum etc). For the past 100 years or so, physicists have been taught that electromagnetic radiation (including light) travels at the same constant speed ad-infinitum. The generally accepted theories on the nature of the universe and its physical properties are significantly influenced by this precept. In order to keep this precept intact, many theories have had to be devised to cater for the situations where the observed reality diverged from the predicted. These may include notions of space-time, dark matter, dark energy, big-bang theory and the expansion (and acceleration of that expansion) of the universe. It is my contention that this precept is not entirely correct. Can I prove it? No is the short answer, but perhaps one day I will be able to do so. I can however forward an argument that supports this claim.

It is my contention that the speed at which electromagnetic radiation travels decreases at a fixed rate. Without external influences, it will do so until it stops. The rate at which the speed decreases is around (surprise, surprise) 72.5 +- 2.5 (km/s)/Mpc – the Hubble Constant. This is the same rate at which the universe is said to be expanding. So which is likely to be more correct? The expanding universe with a constant speed at which electromagnetic radiation travels as accepted by almost all physicists, or a relatively static universe (in terms of expansion/contraction) with a decreasing speed at which electromagnetic radiation travels as proposed here?

If my proposal is correct, then we will never be able to receive any electromagnetic radiation beyond a physical distance. If I am incorrect, then we either can (obviously I wouldn’t be writing this if I already though we already could) or will do at some point in the future. So:

Mdt = Mpc * (c / H) / cy

Where:

Mdt = Maximum distance electromagnetic radiation can travel
Mpc = Megaparsec = 3.0857^19 km
c = speed of light = 299,792 km/s
H = Hubble constant = 72.5 km/s/Mpc (in this example)
cy = distance light travels in a year at c = 9.460528^12

Therefore Mdt = 13.5 billion light years. Let us say between 13 and 14 billion light years given the vagaries of the value of the Hubble Constant.

And so, we on earth should never be able to receive any electromagnetic radiation (light, microwave background radiation etc) beyond 14 billion light years away. Strangely enough, this is exactly the outer limit of what we have seen/received to date.
 
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csmyth3025

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by Mamluk » Fri Sep 04, 2009 7:33 am

It is my contention that the speed at which electromagnetic radiation travels decreases at a fixed rate. Without external influences, it will do so until it stops. The rate at which the speed decreases is around (surprise, surprise) 72.5 +- 2.5 (km/s)/Mpc – the Hubble Constant...
I wonder what experiments have been or can be devised to test this conjecture. Any thoughts?

Chris
 
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SpeedFreek

Guest
My first thought is that this conjecture would mean that the light from galaxies 2 billion light-years away would be travelling slower when it reached us, than the light from a galaxy 1 billion light-years away.

In fact, it means that all the light that reaches us would be travelling at different speeds... :shock:

The CMBR would have hardly any speed at all!
 
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