Assumption: all creation started from the big bang.

Assumption: nothing can exceed the speed of light.

Assumption: we can observe light that has been traveling for 13 billion years.

Assumption: the stuff that makes us us, started from the same point at the same time that light from the big bang did.

Question: How did we get here before the light in order to observe it?


<input id="gwProxy" type="hidden"><!--Session data--><input onclick="jsCall();" id="jsProxy" type="hidden"><input id="gwProxy" type="hidden"><!--Session data--><input onclick="jsCall();" id="jsProxy" type="hidden"><input id="gwProxy" type="hidden"><!--Session data--><input onclick="jsCall();" id="jsProxy" type="hidden"><input id="gwProxy" type="hidden"><!--Session data--><input onclick="jsCall();" id="jsProxy" type="hidden">

Dave,

You missed the part explaining that only "things WITHIN the universe" must obey the speed-of-light conundrum, not the universe as a whole!

As an example, the greater (than, say, our own) red shift galaxies (speaking from our reference point) are moving at the speed of light away from US at the same time WE are moving...thus, it is possible for the universe (as a whole) to exceed the speed of light...just not any entity within it.

Understood...NOT an easy subject to grasp!

Karl

Dave,

You missed the part explaining that only "things WITHIN the universe" must obey the speed-of-light conundrum, not the universe as a whole!

As an example, the greater (than, say, our own) red shift galaxies (speaking from our reference point) are moving at the speed of light away from US at the same time WE are moving...thus, it is possible for the universe (as a whole) to exceed the speed of light...just not any entity within it.

Understood...NOT an easy subject to grasp!

Karl

That does potentially technically solve the problem, but there are some other problems too. The other solution could be that we look at light coming from the far side of universe central. That could account for some of the time lag. That would suppose there was a universe central, and even though everything was supposed to come from a single place, in some theories, those same theories don't have a center of the universe. I don't know why we can't reverse current expansion (in a big computer) to see where we came from(universe center). For that matter, there doesn't seem to be a direction to the universe. No center and no edge. That really doesn't seem to support the big bang from a central point.

Everything seems to point to the ongoing creation of time and space, not from a single point, but from everywhere. That would account for the data, I believe. The big bang theory came from the evidence of an expanding universe. If there is no edge and no center, that doesn't seem to hold water.

What makes sense to me is the expansion of space actually creates matter. Until I hear something better, I'm going with that.

big bang would be a cool name for a putter.

If you were in a car traveling at the speed of light and you turned the head lights on, what would happen?

Who says we're looking at light that resulted from the time of the big bang? The light we are observing now from across the universe was generated long after the big bang. The photons from the big bang have long shot past the earth for us to observe.

Dave,

As I understand it, one of the tenets of the big bang theory is that there is a constant background radiation in the universe of about 3 degrees Kelvin, which somehow is consistent with the theory.

And I mention this in regard to your third assumption. As you are probably aware, light has a wave/particle duality, and it is able to be deflected, so we could detect light that has traveled for 13 billion years if it was deflected back in our direction during the last leg of its journey.

I am not saying I buy into the theory, just saying how I believe some parts of the theory appear to hold water.

Jerry,

Let's say that you were traveling at slightly less than the speed of light, because if the car was traveling at C, it would have infinite mass.

And by "what would happen", it depends on whether the observer was in the car or outside of the car.

If you were inside the car, what you would observe would be that your headlights would reflect from objects ahead of you, just as they do at terran speeds.

Who says we're looking at light that resulted from the time of the big bang? The light we are observing now from across the universe was generated long after the big bang. The photons from the big bang have long shot past the earth for us to observe.

600 million years after. We are at 13.5 billion or so. So we are supposedly looking back almost 13 billion years.

http://www.astro.ucla.edu/~wright/cosmology_faq.html

I don't know astrophysics. Are we always looking back (towards the location of the big bang event) at the stuff from the event? Is some of it "ahead" of us?

At any rate, an explanation (not particularly satisfying I admit) which does not contradict your assumptions is that stuff moves at different speeds out from the big bang event. We just happen to come from the fast stuff, and therefore rightly see the slower stuff closer to the event.

If you were in a car traveling at the speed of light and you turned the head lights on, what would happen?

^ ^ ^ That's a Steven Wright joke...:)

Assumption: all creation started from the big bang.

Assumption: nothing can exceed the speed of light.

Assumption: we can observe light that has been traveling for 13 billion years.

Assumption: the stuff that makes us us, started from the same point at the same time that light from the big bang did.

Question: How did we get here before the light in order to observe it?

We didn't. No one has been able to observe light from the big bang.

Plus your first two assumptions are big ones that I'm not ready to make yet. I have a hard time believing that everything was "created" from the big bang. My thought is rather that everything has always existed. This is a sort of like the concept of infinate space and isn't graspable by us.

The Big Bang was a naked singularity.

Everything seems to point to the ongoing creation of time and space, not from a single point, but from everywhere.

The Big Bang is not the explosion of a mass into pre-existing space. The Big Bang WAS "everywhere". The center of the Big Bang is not a point in space, but a point in time.

The Big Bang is not the explosion of a mass into pre-existing space. The Big Bang WAS "everywhere". The center of the Big Bang is not a point in space, but a point in time.

Space and Time are one in the same. One can't exist without the other thus the Space Time Continuum.

My point is that as you move back in time space contracts. At no time is the Big Bang singularity a point that expands to fill space. There is neither method nor reason to try to locate the singularity in space. It is not like reconstructing the origin of an explosion.

edit -- Oh, and space and time are not one and the same. They are different components of spacetime.

Jerry,

Let's say that you were traveling at slightly less than the speed of light, because if the car was traveling at C, it would have infinite mass.

And by "what would happen", it depends on whether the observer was in the car or outside of the car.

If you were inside the car, what you would observe would be that your headlights would reflect from objects ahead of you, just as they do at terran speeds.

And the light frequency would be blue shifted

42

That is the calculated light billion year distance to the farthest objects we can see. This is based on both the direction of "initial" travel of the objects and the expansion of the universe. 13.7 billion light years later, we receive the light from these objects which are now both some factor of 13.7 billion light years farther away, (less if tangential distance), plus the expansion factor of space.

And by "what would happen", it depends on whether the observer was in the car or outside of the car.

If you were inside the car, what you would observe would be that your headlights would reflect from objects ahead of you, just as they do at terran speeds.

The observer outside the car would see the same thing.

42

That is the calculated light billion year distance to the farthest objects we can see. This is based on both the direction of "initial" travel of the objects and the expansion of the universe. 13.7 billion light years later, we receive the light from these objects which are now both some factor of 13.7 billion light years farther away, (less if tangential distance), plus the expansion factor of space.

Here I thought 42 was "The answer to the ultimate question of life, the universe, and everything."

Here I thought 42 was "The answer to the ultimate question of life, the universe, and everything."

yes, that is correct . according to the all knowing book to the galaxy and hitchhiking across it.

And what happens to the car if it turns on its lights at that speed AND the car is equipped with a flux capacitor?

My point is that as you move back in time space contracts. At no time is the Big Bang singularity a point that expands to fill space. There is neither method nor reason to try to locate the singularity in space. It is not like reconstructing the origin of an explosion.


Interesting, and counter to my unexamined conception of the big bang, or maybe spacetime.

I can sort of understand the futility of trying to plot a coordinate if the axes are in flux, if that is what you mean. However, my immediate response would be to imagine what the big bang exploded into, give it dimensions and use that to plot the time and place of the big bang. I sense that this must be considered folly by cosmologists.

The thing of it is, the expanding singularity is the whole of the universe. We have no way of assigning, determining, or measuring physical characteristics outside of the universe.

Nor is there a center of the universe to identify. We can't point in a direction and say "that way to the center". We cannot say we are closer to an edge than any other. The universe looks the same in every direction.

Expansion is happening equally in all directions from us, but we are not the center. An imperfect, but often used analogy is to imagine the surface of an expanding balloon. The inside of the balloon cannot be seen and has no meaning, only the surface. As the surface expands, all points move away from each other with no common reference point, or center.

Holy crud,

Do I understand Dave's question to be "how do we know the big bang occurred if we can't see it at it's start?" Can't be, please clarify Dave.

1. Go to wiki and read up on the big bang, I suspect any and all questions will be answered there.

2. Pay especial attention to redshift and how the theories of the status of the universe evolved from static to dynamic.

3. Doppler goes hand in hand with redshift and if you can figure out the relationship without going to wiki, you wins a cookie.

I haven't read this closely, but if my thinking is correct, you should be able to trace the expansion of bodies in the universe back to a close approximation of the singularity, the same as they determine where the shooter was by knowing the direction of a bullet by it's pathway through walls bodies etc.

The fact that light travels faster than more corporeal bodies means nothing, especially since we don't even know if there was light at the big bang (at least I don't). What matters is that material started at a single point. Yes different materials travel differently but you can still measure how material travels through space using redshift.

I haven't read this closely, but if my thinking is correct...

Sorry, but your thinking is not correct as is indicated by the above discussion. Check out the FAQ linked above, or do a search on "center of the universe". Cheers!

Oh, and I suspect Dave is well aware of the Doppler effect and redshift as indicated by his correct blueshift comment above.

The thing of it is, the expanding singularity is the whole of the universe. We have no way of assigning, determining, or measuring physical characteristics outside of the universe.

Nor is there a center of the universe to identify. We can't point in a direction and say "that way to the center". We cannot say we are closer to an edge than any other. The universe looks the same in every direction.

Expansion is happening equally in all directions from us, but we are not the center. An imperfect, but often used analogy is to imagine the surface of an expanding balloon. The inside of the balloon cannot be seen and has no meaning, only the surface. As the surface expands, all points move away from each other with no common reference point, or center.

I understand the expanding universe, I just don't understand why the facts would point to a singularity as the origin of the expansion. Why not multiple singularities? Or infinite singularities?

So far the only facts I am aware of are the omnidirectional expansion, accelerating expansion, the lack of any evidence of anything but omnidirectional uniformity in time/space, and the evolution of matter/space over time.

No edge, no center, no direction. Why a singularity as opposed to some type of oscillation? Or my theory that has matter created from the expansion of space/time everywhere?




<input id="gwProxy" type="hidden"><!--Session data--><input onclick="jsCall();" id="jsProxy" type="hidden">

The Big Bang theory is actually a ramification of General Relativity. Since, at the time, expansion was thought to be absurd, Einstein introduced the "cosmological constant" to achieve a stationary universe. Later, Edwin Hubble observed that galaxies were receding, and that further galaxies were receding faster, speed being proportional to distance. This evidence of expansion made Einstein realize the universe might not be stationary and abandon the cosmological constant. Further measurements of cosmic microwave background radiation have indicated that the radiation from the Big Bang was warmer in the past, again indicating an expanding universe. If the universe is expanding, then in the past it must have been smaller. If the universe is homogenous then it must be expanding from a single singularity.

Why no oscillation? That is not a given. If the total mass of the universe is large enough, then eventually gravity will win and the current universe will end in a Big Crunch which may simply be then end of one and the start of another oscillation. However, recent WMAP (Wilkinson Microwave Anisotropy Probe) measurements have suggested that the total mass of the universe is just below that critical point and the universe will keep expanding forever.

New matter is not being created. The expansion of the universe is not an expansion of matter, but an expansion of space. There is the same amount of matter now as there was 13 billion years ago.

Talk of oscillation brings to mind membranes, or brane theory which is incomplete and an outcropping of string theory. In brane theory the sensed universe is a four dimensional occurrence in a larger, 11 dimension "space". Large, parallel membranes oscillate back and forth occasionally striking one another. Each strike is a Big Bang.

Obviously, I am unqualified to act as any kind of authority on this stuff. The following website has both an excellent book list and links to web sites with far more detail than I could ever offer: http://www.phys-astro.sonoma.edu/PEOPLE/FACULTY/TENN/CosmologyBooksAndLinks.html
Books by Brian Greene, Timothy Ferris, and Stephen Hawking are easily read and at least partially understood by the lay reader.

so if space is always expanding... where is it fitting in to? to put something somewhere there must be space for it. is space just creating "space" to fill? space isn't expanding, just infinite. our views of space and the length of it are expanding, but we'll never get to the end of it. if it was expanding, then we'd be able to track it, find the edge, and the center, and we all know that won't happen.

bigger question... how old is space? and time? it just always is and was and will be. it never started and will never end. how is something like that possible?

It is possible if the universe was Created.

Finally, a thread worth posting on. Thanks Dave!


Q: What would happen if the speed of light were only sixty miles per hour?

A: As we approach the speed of light, the aging process slows down. So, if
the speed of light were sixty miles per hour, we would have even more
people speeding, especially older people trying to stay young. As a matter
of fact, physics would demand that we go faster than the speed of
light. The safest thing is to drive at a steady sixty to keep time and the
highway patrol off our necks. Airplanes would become obsolete in this slow
light world, because you would be going so fast, relatively speaking, that
you'd be back before you even left. This would make business trips
unnecessary and lead to economic collapse. So, to answer your question,
life, if the speed of light were sixty miles per hour, would be youthful,
fast, and dark. -- Dr. Science

New matter is not being created. The expansion of the universe is not an expansion of matter, but an expansion of space. There is the same amount of matter now as there was 13 billion years ago.

http://www.phys-astro.sonoma.edu/PEOPLE/FACULTY/TENN/CosmologyBooksAndLinks.html
Books by Brian Greene, Timothy Ferris, and Stephen Hawking are easily read and at least partially understood by the lay reader.

I meant that the expansion of space creates matter. How do we know that new matter is not being created? I have read that astrophysicists have only recently (last 10 to 20 years) "discovered" the majority of the mass in the universe. It is theoretical dark matter, that seems to be held as fact in the present. In light of this, how can we be certain of the constancy of matter?

What about the oscillation of the universe in conjunction with the oscillation of dark and light matter?

What would that matter be created from? New matter created from nothing violates the law of conservation of energy. You are postulating a universe that is not a closed system.

Useful theories make falsifiable predictions. The estimated amount of matter in the universe is a consequence of general relativity and the observed rate of expansion. General Relativity has either made or led to successful predictions including gravitational lensing, cosmic microwave background radiation, the large structure of the universe, the initial abundance of chemical elements, round trip time delay in radar signals bounced off of other planets, gravitational waves, and on and on. Increasing matter in the universe would radically alter the observations and not allow them to fit the equations.

Dark matter is not "discovered" but is postulated beginning in the early 1930s. It is simply the difference between all the observed matter and theoretically estimated matter. There are theories for what might be the nature of dark matter (Weakly Interactive Massive Particles or WIMPs) and detection experiments are ongoing, but to date are not positive. There is some hope that the nascent Large Hadron Collider at Cern will allow detection of WIMPs. Dark energy is a more recent hypothetical dating from the 1990s to try to explain apparent expansion acceleration (increasing matter would decrease expansion BTW). In many ways it is a reintroduction of Einsteins cosmological constant.

Check out that page of links I posted earlier. Lots of this is discussed better and with more detail in those links.

If you find all this to be not weird enough, then move to the very small. Check out Quantum Entanglement or what Einstein referred to as "Spooky action at a distance."

What would that matter be created from? New matter created from nothing violates the law of conservation of energy. You are postulating a universe that is not a closed system.



I almost added the note about conservation of energy, but.....Anyway, the matter might be created from the splitting of the universes. Of course this would have to assume there might be an anti universe as well as our own positive universe.

In order for this to work you might have to think in four dimensions, and the fourth would not be time. The fourth might have to be the end of the curvature of space that comes back to the "beginning".

Another potential source of matter is from what seems to be the "ether" of space. It seems highly likely to me that the space between visible matter is composed of something. Otherwise we would have to invent another propagation method for electromagnetic radiation. Radio and light wave action seems to be no different in other mediums such as water and glass than it is in space. With the assumption that space is composed of some medium, (say ether), then movement of the medium, and objects through the medium would be a source of energy and therefore matter, especially accelerated movement.

Electromagnetic radiation is not a mechanical wave. The idea that it needs a "luminiferous aether" to propagate was discarded in the very early 20th century. See the famous Michelson-Morley experiment in the 1880s and Einstein's Special Theory of Relativity.

Again, increasing matter in the universe does not fit the observation.

Radio and light waves act far differently through other mediums than they do through space. Buy a prism, or look at the light passing through the beveled glass of your office windows.

Electromagnetic radiation is not a mechanical wave. The idea that it needs a "luminiferous aether" to propagate was discarded in the very early 20th century. See the famous Michelson-Morley experiment in the 1880s and Einstein's Special Theory of Relativity.

Radio and light waves act far differently through other mediums than they do through space. Buy a prism, or look at the light passing through the beveled glass of your office windows.


Please expand on "far differently"

It makes no sense to me that light isn't being propagated in space. Something is determining the speed of light and causing the frequency shifts of relative speeds.

Please expand on "far differently"

It makes no sense to me that light isn't being propagated in space. Something is determining the speed of light and causing the frequency shifts of relative speeds.

You need to do some basic physics research. The speed of redshifted light in space is no different from blueshifted light in space. It's the observers relative motion to the light that causes said observer to encounter wave peaks and troughs slower or faster.

The speed of light is not the same through glass, or air, or water, or plastic, or copper wire, or your desk as it is through a vacuum. Light refracts when passing through a medium.

For a very interesting and detailed treatment pick up a copy of Richard Feynman's Q.E.D.

And definitely research Special Relativity.

You need to do some basic physics research. The speed of redshifted light in space is no different from blueshifted light in space. It's the observers relative motion to the light that causes said observer to encounter wave peaks and troughs slower or faster.

The speed of light is not the same through glass, or air, or water, or plastic, or copper wire, or your desk as it is through a vacuum. Light refracts when passing through a medium.

For a very interesting and detailed treatment pick up a copy of Richard Feynman's Q.E.D.

And definitely research Special Relativity.

Yes, I understand all this. What I don't understand is why the notion that there was no medium necessary for the propagation of light in space. Something is determining light speed in space, just as light speed is determined in other mediums.

The speed of light in a vacuum is a fundamental law of the universe. It is the speed at which all massless particles travel in a vacuum. It's independent of the relative motion of the observer. It's believed to be the speed of gravity, and gravitational waves. It's fundamental to the relationship between mass and energy (E=mc^2). It is the link between space and time. Why is it 299,792,458 m/s? I don't know. But to reiterate, thoughts of a medium through which light travels in space were discarded a century ago.

"Why isn't the speed of light infinite?" (http://www.scientificamerican.com/article.cfm?id=why-isnt-the-speed-of-lig)

But to reiterate, thoughts of a medium through which light travels in space were discarded a century ago.

"Why isn't the speed of light infinite?" (http://www.scientificamerican.com/article.cfm?id=why-isnt-the-speed-of-lig)

The speed of light is a constant, in a constant medium. The medium or maxtrix of space is what causes gravity, according to Einstein. Mass, like planets and stars, displace space, and it is that displacement, (or warping), that is the cause of gravity. Further, there is evidence, (extrapolating from the Shipiro effect) that light travels slower in areas of higher gravitation (around stars etc.).

Now, even though the evidence seems indicate that light travels slower in denser gravitational regions, (just like water and glass and air) they choose to believe that time travels slower instead.

Now, even though the evidence seems indicate that light travels slower in denser gravitational regions, (just like water and glass and air) they choose to believe that time travels slower instead.

The bastards.

Do you argue, then, that the stated effects of gravitational time dilation on GPS clocks is part of the same conspiracy? :)

The bastards.

Do you argue, then, that the stated effects of gravitational time dilation on GPS clocks is part of the same conspiracy? :)

I would, if I could find some basis for my argument. I would have to know how the GPS clocks function.

If the rate of expansion of the universe is accelerating, how does that affect the calculation of the age of the universe and age and distance to the observed stars in earlier stages of formation?

Is the rate of acceleration, accelerating? Or has the rate of acceleration been constant?

I went on a physics forum to ask theses kinds of questions, but so far I have been disappointed with the answers.
<input id="gwProxy" type="hidden"><!--Session data--><input onclick="jsCall();" id="jsProxy" type="hidden">

Sorry, but your thinking is not correct as is indicated by the above discussion. Check out the FAQ linked above, or do a search on "center of the universe". Cheers!

Oh, and I suspect Dave is well aware of the Doppler effect and redshift as indicated by his correct blueshift comment above.

I think Mr. Krasinski, that you may misunderstand me. If my understanding of Dave's question is correct (and I'm not saying it is) then the basic issue becomes, how do you answer the question? Your approach is one of physics, mine instead is one of philosophy. I take a philosophical approach because as I think has been discovered in this thread, there is no solution through physics, hence the question has a dead end. How boring.

1) That we currently don't have the tools to move backwards to the start of the "big bang" by observation or calculation is irrelevant. It is only human hubris that makes us think we never will, that our current understanding or ability is developed enough that we can see no possibility of ever answering the question. The plain and simple fact is that if you give me an unlimited supply of monkeys, with unlimited amounts of pencils, paper, time and knowledge, eventually they would draw a picture of the universe as it existed at the big bang (whether it be a small singularity [or multiples as Dave offered], or an equal distribution of energy throughout the universe as it existed at that time) and human kind would be able to discern the correct picture.

2) Red Shift and Doppler, no cookie KK, sorry, although I am disappointed that you didn't think I had the patience to pre-read the thread. Red Shift and Doppler have more than a "physics" relationship, they demonstrate, IMSWO, a philosophical point. If we know of Doppler, but not of Red Shift, and assume we know all there is about the movement of physical bodies and their impact on their environment, then we never make the leap to the use of Red Shift to determine that stellar bodies are moving away from us in space. We are left with a static universe, and the question becomes moot. If we assume, because we can't at this time measure the movement and evolution of the universe, tracing it back to it's origins (using something infinity more advanced than tracing a bullet back to the shooter, and yet following similar principles) then we probably never will.

3) Physics is particularly prone (IMNSHO) to filling in gaps with, "we don't know therefore it's not important) or guesses that are incorrect. Take for an example Newton's exploration of the speed of sound. He hypothesized, but the math didn't fit his observations. Therefore, he invented a constant to fill in the difference. He was wrong. Dark Matter is IMO a classic case, observation doesn't fit theory, therefore, there has to be an undefined material that fills in the difference. Heaven forbid that we consider Occam's Razor, and go with the simple solution, there is a flaw in the theory, or in the observation (please remember I don't know all the logic behind DM, but I do understand OR quite well). On the other hand, let's go with Dark Matter, and explore one of Dave's notions. What if Dark matter isn't just material that adds to the mass of the universe? What if instead Dark matter consists of some amount of matter, and some amount of anti material (no not antimatter) that takes away from the mass of the universe. All kinds of interesting things could be going on there that we can't or don't observe, how wonderful. Dave's notion that there could be other things going on is right on point, IMO.

It truly is only our hubris that makes us think that only testable theories have value, and then to try and make things that aren't testable fit into those "theories." It is only our self limitation that makes us think that some things can't be figured out and therefore, aren't important.

BTW Dave, according to wiki, most generally accepted theories revolve around the notion that the starting state was indeed a uniform distribution of energy throughout the universe as it existed at that time, although the links that Mr, Kasinski provided paint the picture differently, and this is subject to my ability to understand what is written. I believe they do say that how far back you can extrapolate is debatable. Personally, strictly from a philosophical point of view, I'm much more interested in what started the original cosmic inflation? That may be out there (I'm guessing it is) somewhere in the literature, I haven't looked.

<object width="425" height="344">


<embed src="http://www.youtube.com/v/y53hh-LAbLk&hl=en_US&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></object>

...

I would, if I could find some basis for my argument. I would have to know how the GPS clocks function.

Essentially like this:
http://www.nrc-cnrc.gc.ca/eng/services/inms/time-services/faq-time.html#Q10

If the rate of expansion of the universe is accelerating, how does that affect the calculation of the age of the universe and age and distance to the observed stars in earlier stages of formation?

Accelerating expansion increases age estimations.

I don't understand the second part of your question. Stars within our galaxy our not really affected relative to each other by expansion as gravity has far more influence. Using the Hubbel telescope and an exposure time of several hours a star that is one million times brighter than the sun can only be observed to about 3 billion light years away. Distances to far objects are calculated a variety of ways, depending on distance (for example parallax only works with relatively near objects) with some overlap that helps calibrate successive techniques.

Is the rate of acceleration, accelerating? Or has the rate of acceleration been constant?

I don't know. However, the closer the rate of expansion is to constant, the closer the age of the universe is to 1/H with H being the current value of the Hubbel Constant, or about 14 billion years.

Essentially like this:
http://www.nrc-cnrc.gc.ca/eng/services/inms/time-services/faq-time.html#Q10



Accelerating expansion increases age estimations.

I don't understand the second part of your question. Stars within our galaxy our not really affected relative to each other by expansion as gravity has far more influence. Using the Hubbel telescope and an exposure time of several hours a star that is one million times brighter than the sun can only be observed to about 3 billion light years away. Distances to far objects are calculated a variety of ways, depending on distance (for example parallax only works with relatively near objects) with some overlap that helps calibrate successive techniques.



I don't know. However, the closer the rate of expansion is to constant, the closer the age of the universe is to 1/H with H being the current value of the Hubbel Constant, or about 14 billion years.

For the GPS clock. Do acceleration moments on the clock affect it's time keeping? For instance, would having a cesium clock in a centrifuge make it run slower?

For the second part of the second question. (I should have had two sentences) How does the accelerating rate of the universe's expansion affect the calculation of age and distance of very distant starts or stars as they existed billions of years ago? Would that make them younger or older than previously calculated. Would that make them closer or father than previously calculated?

Thanks for the help.

<input id="gwProxy" type="hidden"><!--Session data--><input onclick="jsCall();" id="jsProxy" type="hidden">

For the GPS clock. Do acceleration moments on the clock affect it's time keeping? For instance, would having a cesium clock in a centrifuge make it run slower?

Experimentation has shown that atomic clocks are not impacted by orientation with respect to acceleration. They are only affected by the depth of the gravity well.

For the second part of the second question. (I should have had two sentences) How does the accelerating rate of the universe's expansion affect the calculation of age and distance of very distant starts or stars as they existed billions of years ago? Would that make them younger or older than previously calculated. Would that make them closer or father than previously calculated?

Neither age nor distance of stars are extrapolated from expansion. For example, a common method of determining distance to far galaxies is through the luminosity of type la supernova, which all have the same absolute magnitudes. Age is primarily determined through analysis of chemical composition. Both very young and very old stars can be found in the Milky Way and the most massive stars have a life span of only around one million years.

Thanks for the help.

You're welcome, but I must re-emphasize that in no way should my posts be considered authoritative. I respond only to the best of my unqualified understanding.

Experimentation has shown that atomic clocks are not impacted by orientation with respect to acceleration. They are only affected by the depth of the gravity well.

You're welcome, but I must re-emphasize that in no way should my posts be considered authoritative. I respond only to the best of my unqualified understanding.

If the clocks are affected by the depth of the gravity well, could that account for the apparent slowing of time?

You may not consider your posts to be authoritative, but I have been on a physics forum and you give better answers. The only one I have talked to that seems to know more is Dave Devine, a disc golfer.

I had a rousing discussion with him this weekend at the NorCal SoCal challenge. His contention, (which is the commonly shared view), is that it has been proven "over and over", to quote him, that time not only appears to flow differently relative to the observer, but actually does flow differently. I disagree, but need a mechanism to disprove the atomic clock "proof".

The twin paradox has two twins. One leaves planet Earth and travels around the galaxy and returns. The traveler returns younger than his twin. If everything is relative to the observer, who's to say which twin is moving? The answer is acceleration. Whoever feels the acceleration is the one who moved according to the answer to the twin conundrum. That is the only difference.

But if the time differences measured in atomic clocks can be attributed to gravity wells, (acceleration), that might account for it as an artifact rather than a real "proof".

If the rate of expansion of the universe is accelerating, how does that affect the calculation of the age of the universe and age and distance to the observed stars in earlier stages of formation?

Is the rate of acceleration, accelerating? Or has the rate of acceleration been constant?

I went on a physics forum to ask theses kinds of questions, but so far I have been disappointed with the answers.
<input id="gwProxy" type="hidden"><!--Session data--><input onclick="jsCall();" id="jsProxy" type="hidden">

consider that the space itself between all objects in the universe is expanding, this is the dark matter. dark matter or dark energy does not interact with any other matter in the universe except gravity. it is also taking over gravity as the dominant force, causing greater acceleration. all objects not tied to each other in a gravitational field are moving away from each other

standard particles must stay below the universal speed limit, but theoretically particles should exist that travel faster than the speed of light and cannot go below it (axions). these have not yet been captured but apparently are moving through us at all times.

If the clocks are affected by the depth of the gravity well, could that account for the apparent slowing of time?

I guess I phrased that poorly. It accounts for the actual slowing of time. Gravitational Time Dilation. :)

The twin paradox has two twins. One leaves planet Earth and travels around the galaxy and returns. The traveler returns younger than his twin. If everything is relative to the observer, who's to say which twin is moving? The answer is acceleration. Whoever feels the acceleration is the one who moved according to the answer to the twin conundrum. That is the only difference.

No, the difference is that the twin which leaves earth leaves one inertial frame of reference and enters another one for the return trip. What is important is not the feeling of acceleration, but the fact that the traveller requires more than a single frame whereas the stay at home twin requires only one. The same effect as in the twin paradox can be demonstrated without accelerations using a third person to occupy the third frame. See the bottom of this page: http://www.phys.vt.edu/~jhs/faq/twins.html

Here's a pretty good fairly technical description of some of the historical tests of general relativity: http://luth2.obspm.fr/IHP06/lectures/mester-vinet/IHP-2GravRedshift.pdf

Howdy Dave!

Glad to hear you are still chewing on this stuff. It might help if you try to get in the habit of thinking about space-time rather than space and time. Just like the shadow of a pole can have different lengths on the ground (projections), time intervals can have different values for different observers (time is a projection, or shadow, of space-time). Time does indeed flow at different rates for different observers. If it did not then the high energy atom smashing machines would not give the results that they have since the 20s and 30s. Any alternate theory is going to have to be able to explain those results as well.

The paramount role of observers in SR and GR can be looked at in another way. It does not matter where sentient life arises, that life will discover the same relationships (physical laws) independent of the local gravitational field (planet). If the laws of physics depended on absolute motion then we would have been screwed, because we would have had to have known about stuff like the motion of the Sun around the center of the Milky Way etc. in order to explain phenomena we observe here on Earth. SR frees us from the chains of Absolute Motion, and GR frees us from the chains of having to be at a special location in order to unravel Natural Pheneomena. The fact that the laws can be written in terms of relative motion alone is an affirmation that the Universe is comprehensible, no matter where we happen to spring up. It seems that the idea of Absolute Time has to take a back seat to this freedom.

As always, I love the conversations. Beats the hell out of grading!

Cheers, David

Howdy Dave!

Glad to hear you are still chewing on this stuff. It might help if you try to get in the habit of thinking about space-time rather than space and time. Just like the shadow of a pole can have different lengths on the ground (projections), time intervals can have different values for different observers (time is a projection, or shadow, of space-time). Time does indeed flow at different rates for different observers. If it did not then the high energy atom smashing machines would not give the results that they have since the 20s and 30s. Any alternate theory is going to have to be able to explain those results as well.

The paramount role of observers in SR and GR can be looked at in another way. It does not matter where sentient life arises, that life will discover the same relationships (physical laws) independent of the local gravitational field (planet). If the laws of physics depended on absolute motion then we would have been screwed, because we would have had to have known about stuff like the motion of the Sun around the center of the Milky Way etc. in order to explain phenomena we observe here on Earth. SR frees us from the chains of Absolute Motion, and GR frees us from the chains of having to be at a special location in order to unravel Natural Pheneomena. The fact that the laws can be written in terms of relative motion alone is an affirmation that the Universe is comprehensible, no matter where we happen to spring up. It seems that the idea of Absolute Time has to take a back seat to this freedom.

As always, I love the conversations. Beats the hell out of grading!

Cheers, David

I as said, I always got all that. It was having a different time after return of traveler, that I disagreed with. There is a thread (kkras jan 18) that talks about the twins. It states that acceleration is not necessary.

Also, if you can go .75 C and I can go .75C in the opposite direction, why are we not receding from each other at 1.5C?

<input id="gwProxy" type="hidden"><!--Session data--><input onclick="jsCall();" id="jsProxy" type="hidden">

Howdy Dave

Check out how velocities are added in Special Relativity to see why the relative speed of two frames moving in opposite directions at .75c is not 1.5c. The standard method (just add velocities v1 + v2) works in the limit of small v/c. The correct formula includes space-time dilation effects that are contained in the Lorentz transformation. The same effects are related to the different values for acceleration that tie into the speed limit c. I hope that we figure out how to expand these results to get to speeds greater than c so we can travel to the stars, but that is beyond our current understanding of space and time.

I am not a fan of using three different observers to resolve the twin paradox since the premise of the twin paradox involves two twins that separate and then are rejoined. The necessity of acceleration for one of the twins to go and then come back breaks the symmetry of the twins' reference frames. Introducing a third reference frame gives the same result but throws out the original "paradox" since you are no longer directly comparing the twins with each other. The difference in age in both cases is related to the different rates for the flow of time for frames that move relative to each other.

Thanks for not going with the flow. Questions always lead to a deeper understanding for both parties.

Cheers, DD

Howdy Dave

Check out how velocities are added in Special Relativity to see why the relative speed of two frames moving in opposite directions at .75c is not 1.5c. The standard method (just add velocities v1 + v2) works in the limit of small v/c. The correct formula includes space-time dilation effects that are contained in the Lorentz transformation. The same effects are related to the different values for acceleration that tie into the speed limit c. I hope that we figure out how to expand these results to get to speeds greater than c so we can travel to the stars, but that is beyond our current understanding of space and time.

I am not a fan of using three different observers to resolve the twin paradox since the premise of the twin paradox involves two twins that separate and then are rejoined. The necessity of acceleration for one of the twins to go and then come back breaks the symmetry of the twins' reference frames. Introducing a third reference frame gives the same result but throws out the original "paradox" since you are no longer directly comparing the twins with each other. The difference in age in both cases is related to the different rates for the flow of time for frames that move relative to each other.

Thanks for not going with the flow. Questions always lead to a deeper understanding for both parties.

Cheers, DD

Thanks DD,

DD