Space/Time expansion to relative time??

[SpeedFreek]

<font color="yellow">What you said still works in the same way. If 'space' is purely surface area of our "balloon" and time is the radius you would see exponential surface expansion compared to relative time, while they both expand correspondingly. Does that make sense?</font><br /><br />If you measure the increase in surface area compared to the increase in radius, you find that the surface area increases by a much larger factor for each discrete segment of increased time, therefore they do not both expand correspondingly. As time passes constantly, surface area increases exponentially.<br /><br /><font color="yellow">But, does that possibly cause time to appear relativly slower closer to the 'Big Bang' than it would to someone viewing the universe from and outside perspective with time their own relative speed?</font><br /><br />I cannot speculate as to how time might pass outside the universe, but from within, time always passes at its fastest for an observer in free fall.<br /><br />The observation that supernovae last for a longer duration the further back in time you look does not mean that time passed at a different rate back in time, it only means that the light we observed has been stretched.<br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[americanpsycho]

On the first part, you misunderstood what I was saying. I was trying to say that 'space' was expanding at an exponentially larger rate than 'time'. I just meant that they both were expanding at the same time, just different rates. <br /><br />I've got to read the second part a few more time. <img src="/images/icons/smile.gif" /> <br />

 

[SpeedFreek]

It is the part about time "expanding" that I don't understand. Our observations tell us that time passes at the same rate now as it did early on in the universe, if the universe is expanding. To an observer in an inertial frame of reference, it took the same amount of time for light to travel a light year then, as it does now. Light-years as a distance have not grown in size due to the expansion, but more light-years have been added. <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[americanpsycho]

Actually, I do think a light year is different now than, lets say, that first millisecond out of singularity. <br /><br />Now, I have no credited training, so all of this is just opinions from understanding.<br /><br />I'm stuck on the expanding balloon over the TNT exploding Big Bang. I visualize a chess board drawn across the entire surface of a deflated balloon. And I imagine that each square of the board (space/time frame) is a square light-year. I feel that when the universe was the size of a baseball it still took light many many years to cross it (Have no facts or proof to back this up) because those 'square light-years' were relativly much smaller. I feel that those 'square light-year' frames grew as the universe (balloon) expanded, therefore, causing a difference in how someone internal to said universe would interpret that lapsed time differently....<br /><br />I don't mean to be difficult, I just think that if space/time expands with the universe itself that the relative speed of light would change from one point to the next. Relative to an outside observer, that is. <br /><br />I just think that that first millisecond it took for the universe to go from singularity to what it's enormous size would have taken billions of years to an inside observer. <br /><br />I think that if we lived during that initial expansion that millions of civilizations could have lived and died during that time.......... may be totally psychotic, but.....

 

[kelvinzero]

<font color="yellow">Our observations tell us that time passes at the same rate now as it did early on in the universe, if the universe is expanding.</font><br /><br />btw, at what rate <i>is</i> time passing where you are right now. Give me a number so I can see if it is passing at the same rate here. <img src="/images/icons/wink.gif" />

 

[SpeedFreek]

Ok, let's look at some details here. <img src="/images/icons/smile.gif" /><br /><br /><font color="yellow">I'm stuck on the expanding balloon over the TNT exploding Big Bang</font><br /><br />Good! The balloon model is a far better representation of the expanding universe than an explosion. An explosion the big-bang was <b>not!</b><br /><br /><br /><font color="yellow">I feel that when the universe was the size of a baseball it still took light many many years to cross it</font><br /><br />The <i>observable</i> universe is indeed theorised to have been the size of a grapefruit <i>after</i> the "inflation" stage. In order to acheive an expansion from being almost point-like to the size of a grapefruit in the merest fraction of a second, superluminal (faster than light) expansion must have occurred. This is where some popular media sites (and indeed some cosmologists) <b>incorrectly</b> state that the universe inflated from a singularity to something like the size it is today, in a fraction of a second.<br /><br />That is <b>not</b> how the theory goes. After the superluminal inflation, the observable universe was supposed to be only the size of a grapefruit. (The <i>whole</i> universe, could have been any size!)<br /><br /> This link sends you to a PDF file that I think you need to read. It is a very good guide to some of the misconceptions surrounding the big-bang and the expansion of space, and will help dispel some of the misconceptions you are working under.<br /><br /><br /><font color="yellow"> I just think that that first millisecond it took for the universe to go from singularity to what it's enormous size would have taken billions of years to an inside observer. </font><br /><br />I believe this is based on one of those misconceptions, as the universe is only actually theorised to have inflated to the size of a grapefruit, as I said above.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[SpeedFreek]

<font color="yellow">at what rate is time passing where you are right now?</font><br /><br />It is passing at pretty much the same rate as where <i>you</i> are, if you are only a few meters above sea-level and at rest upon the Earth. <img src="/images/icons/tongue.gif" /> <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[americanpsycho]

Today I feel like time is moving slower right here than anywhere in the universe. <img src="/images/icons/tongue.gif" /><br />I meant to an observer outside our universe (which I'm sure isn't possible). <img src="/images/icons/smile.gif" /><br /><br />Thanks for the link, going to check it out right now.

 

[kelvinzero]

<font color="yellow">It is passing at pretty much the same rate as where you are, if you are only a few meters above sea-level and at rest upon the Earth. </font><br /><br />Im sure it is. But Im asking something much simpler. We are so sure time is passing at a constant rate, but just try to put a number to that rate. Or even tell me the units of that rate. Time passes wrt to what?<br /><br />No doubt it can be explained with some subtle examination of entropy and the reversibility (or not) of calculations, but this notion of time passing is no where near as obvoius to physics as it is to us.

 

[SpeedFreek]

Yes, I knew what you meant, but I wanted it spelt out. <img src="/images/icons/smile.gif" /><br /><br />It seems to me that how we experience time is directly related to two factors - the amount of gravity we experience and the speed of light. So on the face value it might seem like <i>americanpsycho</i> is on to something.<br /><br />The closer to the speed of light you travel, over a given distance, the slower you experience time. The more gravity you experience, the slower you experience time. Time passes at its fastest when you are "at rest" and under the least gravitational influence. So in this universe, that would be when you are in free fall in the voids between the galactic superclusters. Sure, there is still some very slight almost infinitesimally small gravitational influence upon you, so you wont be experiencing time passing as fast as is <i>theoretically possible</i>, but those conditions are the closest you will get within this universe.<br /><br />So, the question is, has the rate that time passes at its fastest remained constant throughout the history of the universe? Americanpsycho asks this in relation to an observer "outside" the universe, which I feel is unanswerable as we have no conception as to how time might pass from that viewpoint, if there <b>is</b> such a viewpoint.<br /><br />All we can do is look at this issue from the inside, and there lies the problem. If light-years are a different "absolute" size now, to how they were early on in the universe, how could we know?<br /><br />Well, firstly let's look at the epoch in which americanpsycho wants to perform this thought experiment - the inflationary epoch. He was using an example where the universe inflated from almost point-like size to a size approaching the size the universe is today, in a fraction of a second. But our observable universe is thought to have only inflated to the size of a grapefruit during that epoch. Now he wants to use a viewpoint of "outside" the universe for this experiment. If <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[kelvinzero]

Nah I was just pointing out the concept that time <i>passes at a rate</i> is very weak in physics. The notion is unnecessary to explain anything. However im not really talking about relativity, gravity or inflation. I didnt intend to take up much space in this thread with this observation so I wont argue it further here.

 

[lizhare]

in regards to the expansion of the universe, do you think it is possible that though we think that the universe is expanding due to red shift etc, is it not possible that the galaxies are 'repelling' each other, and we are not actually expanding at all?

 

[SpeedFreek]

Whether galaxies are "repelling" each other or space is expanding between them, the end result is that the distance between those galaxies has increased.<br /><br />Seeing as the most distant galaxies seem to be receding from us at many multiples of the speed of light, those galaxies inertial motion cannot be the cause. <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[lizhare]

i understand this, what i am curious about, it that the idea that our universe is expanding is based on this theory, i am not disputing the expansion of the mass, rather what we are exanding into, for example if it is a limited distance etc!

 

[SpeedFreek]

If I understand you correctly, you are asking if the redshifts of distant galaxies might be due to something like galaxies repelling each other and moving apart through space, rather than the space in between galaxies expanding.<br /><br />No object with mass, be it a galaxy or a grain of sand, can be caused to <i>move</i> through empty space faster than the speed of light and yet we see distant galaxies whose redshifts show them to be receding from us faster than light.<br /><br />Conclusion - those objects aren't moving away at that speed, but the space in between them and us is expanding.<br /><br />What specific questions do you have? <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[lizhare]

i understand what you mean, thankyou. its been bothering me all day!

 

[bass901]

"No object with mass, be it a galaxy or a grain of sand, can be caused to move through empty space faster than the speed of light and yet we see distant galaxies whose redshifts show them to be receding from us faster than light. "<br /><br />This makes no sense to me. If they are moving away from us faster than the speed that light travels, then the light from these objects would never overcome that speed to reach us.<br /><br />If you move faster than the speed of sound, sound waves would never catch up to you for your ears to hear them. The same with light. If the space between us and these distant objects is expanding faster than the speed that photons can travel, those photons would never reach our planet.<br /><br />Another analogy would be that if your car is going 50 MPH and the street is expanding at 80 MPH, your car would never go past the center of the expansion point in the street.<br /><br />How is it possible for us to continue to receive light from those galaxies?

 

[americanpsycho]

This whole idea just came to me the other night, sort of twisted my brain. <img src="/images/icons/smile.gif" /> I love some of the information 'speedfreak' has. Sheds light on a lot of my questions. I have more to my question, just have to figure out how to word it. Hope I've made some of you think as hard as I have. Thanks

 

[origin]

<font color="yellow">This makes no sense to me. If they are moving away from us faster than the speed that light travels, then the light from these objects would never overcome that speed to reach us. </font><br /><br />He is not say that the light we see was from a galaxy receding faster than c, he is say that redshift indicates that it is NOW receding faster than c. Remeber the light we see now was emitted billions of years ago. <br /> This explains it well. <div class="Discussion_UserSignature"> </div>

 

[SpeedFreek]

And, just to confuse things, we <i>can</i> see the light from objects that have <i>always</i> been receding from this point in space at velocities greater than the speed of light!<br /><br /> This link is a scientific paper that explains the process. From the introduction to that paper:<br /><br /><i>"We use standard general relativity to illustrate and clarify several common misconceptions about the expansion of the universe. To show the abundance of these misconceptions we cite numerous misleading, or easily misinterpreted, statements in the literature. In the context of the new standard ΛCDM cosmology we point out confusions regarding the particle horizon, the event horizon, the `observable universe' and the Hubble sphere (distance at which recession velocity=c). <b>We show that we can observe galaxies that have, and always have had, recession velocities greater than the speed of light. We explain why this does not violate special relativity and we link these concepts to observational tests.</b> Attempts to restrict recession velocities to less than the speed of light require a special relativistic interpretation of cosmological redshifts."</i><br /><br />A synopsis of this paper, in the form of a Scientific American article by the same authors, is available here. <br /><br />From that article:<br /><br /><i>"Notice that, according to Hubble's law, the universe does not expand at a single speed. Some galaxies recede from us at 1,000 kilometers per second, others (those twice as distant) at 2,000 km/s, and so on. In fact, Hubble's law predicts that galaxies beyond a certain distance, known as the Hubble distance, recede faster than the speed of light. For the measured value of the Hubble constant, this distance is about 14 billion light-years.<br /><br />Does this prediction of faster-th</i> <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[bass901]

So you are saying that the expansion is pushing the galaxy away faster than the speed of light but the light can still make it here eventually as the expansion slows down. Got it.<br /><br />What keeps the earth (and us) from expanding? The Sun or Milky Way's gravity field? Would that mean that empty space, void of a strong gravity field is the only thing expanding?

 

[SpeedFreek]

Gravity overwhelms the expansion of space, so only where there are no gravitationally bound systems can space expand. This means that space expands only in the large empty voids between the galactic clusters.<br /><br />Where galaxies cluster together due to gravity, their gravity dominates over the expansion, and the same is true inside galaxies and solar systems. <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>