IM Egdall

OK. Thanks for the clarification. So if you walk down the road and return, your wristwatch will show that less time went by for you than the clock at rest on the road (assuming extremely accurate clocks). So more time has gone by on that spot on the road than time for you. So you return to that spot on the road a tiny bit into the future. (I think I got this right). This kind of time travel is just what happens any time we leave a place and return to it. It's just that the effect is so small we don't notice it.

I agree. And ThoR should consider the evidence. The Cosmic Microwave Background and other observations indicate the universe is flat. So infinite in extent. (But this is evidence for the observable universe.)

Do you mean by moving down the road, your time is running slower than time for a clock on the road? In other words, time dilation?

And this is a fundamental problem with physics. The equations of physics show no preference for the arrow of time. So it is difficult to explain using physics why in reality time moves forward. Entropy does imply a forward arrow, but it is a statistical concept and applies only to a large number of particles. see http://en.wikipedia.org/wiki/Arrow_of_time

Yes. We would also "see' the Sun for the same 8 minutes or so.

Yes. You are describing the four co-ordinates of an event in spacetime.

I did not say gravity = time. I said gravity is the warping of space-time. Per general relativity, both space and time are warped in the presence of mass/energy. The mass and energy of the Earth, for example, warps space and time in its vicinity. (Clocks run slower and radial distances are stretched.) This warping of time and space causes objects to fall to the Earth, holds me in my seat as I type this, holds the Moon in it orbit around the Earth, etc. In short, all phenomena we attribute to "gravity" are the result of the warping of space and time (spacetime curvature). This is what the mathematics of general relativity shows.

Fascinating! Thanks for the clarification on "weak" clumping and the dark star links.

I believe modern cosmology leans toward the "cosmos is infinite" idea. But per Einstein's general relativity, even an infinite cosmos can expand. As to an eternal cosmos, it may very well be. We just don't know. Since general relativity fails at time zero of the big bang, we cannot project to before the big bang. Did time begin with the big bang or was there time before the big bang? We don't know. So an eternal cosmos remains an open question in our current understanding. As to your saying it is all a waste of time, I totally disagree. The fact that some brilliant human minds on this tiny planet somewhere in the vast cosmos have developed a scientific theory on the creation and evolution of the universe which is supported by empirical evidence (lots of it) is extraordinary, to say the least. Yes we only observe a tiny portion of the universe (we think) and yes, the big bang theory may be subject to future modification and change (like any scientific theory). But all-in-all, I for one am thankful to be alive in this age of wonder and cosmic discoveries.

Gravity is the warping of space-time. They are one and the same.

I believe the use of time as the "fourth" dimension started with the spacetime physics of Poincare and Minkowki in 1907 or so. And it is rooted in the concept of the spacetime interval. Einstein showed in 1905 that time and space are relative -- the time interval and space interval between two events is different depending on the (uniform) motion of the observer. Poincare and Minkowski showed that a combination of time and space called the spacetime interval is absolute. It is the same for all observers, no matter what their (uniform) motion. From this a new set of mathematics was developed in four dimensions -- three space and one time. See link: http://en.wikipedia.org/wiki/Spacetime

So what interpretation do you propose which matches all the observations?

If anything you do allows you, in principle, to tell which slit an individual electron went through, then there will be no interference.

The satellite clocks show a net (or combined) effect of both time dilation and gravitational time dilation.

Ya, I am aware of all this. My question was not about dark matter and strong force, weak force, or EM force. It was about dark matter and gravity. I was asking for a good link which explains the "weak" clumping of dark matter due to gravity.

They combine. For example, clocks on GPS satellites must be corrected for both effects: Time dilation: Atomic clocks on board GPS satellites run slower than clocks on Earth by about 7 thousand nanoseconds per day -- due to their motion relative to the Earth. Gravitational time dilation: The satellite clocks run faster than Earth surface clocks by about 45 thousand nanoseconds per day -- due to their higher altitude. Taken together, there is a net gain of about 45 -7 or 38 thousand nanoseconds per day. Since GPS needs an accuracy of 20-30 nanoseconds to work, the combined effect must be taken into account. See link: http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html <br clear="all"> http://www-astronomy.mps.ohio-state.edu/~pogge/Ast162/Unit5/gps.html

The big bang model is the best theory we currently have on the creation and evolution of the universe. Why? Because of all the evidence from a number of independent observations which agree with its predictions. See link: http://en.wikipedia.org/wiki/Big_Bang#Observational_evidence If you challenge the theory, then please give us an alternative theory which also fits with observations and offers new predictions which can be verified.

Hmmm. Very interesting! Thanks. Do you know of a link where I could get more info on this effect where dark matter does not tend to form into stellar objects?

Ya I thought it was something like that. There is so much space between stellar objects. The link you provided is very helpful . Thanks. I still have a question though. Why is it dark matter doesn't clump due to gravity like ordinary matter into dark matter stellar objects?

So, based on the motion of stars in galaxies and galaxy cluster motion etc., there is roughly 5 times more "dark matter" than ordinary matter in the universe. No one knows what this dark matter is. But, presumedly, it is in our solar system. So how does it affect the orbits of our planets around the Sun and moons around the planets, not to mention comets etc. ? How is it that we can explain these orbits and motions to such great accuracy using general relativity and only the masses of the Sun, planets, moons, etc? These do not include the effects of dark matter. If there is 5 times as much dark matter as the ordinary matter which makes up our stellar objects, why does it not affect these motions more? Edited to fix my dumb typos.

I am pretty inept at this, but I still don't know how to put web links into my blog. I put in the URL address in my text, highlight it, and then press the blue LINK button. It does some code thing to the address, but when I do a Preview, there is no link. And how do I fill out the form that comes up? Any help is most appreciated.

Here's how I think it goes. I know this explanation is not rigorous, but I think it gives the gist of what is going on. Per general relativity, spacetime curvature is the warping or change in spacetime due to the presence of mass/energy. The mass and energy of the Sun, for example, warps both time and space in its vicinity. This warping is what makes planets orbit the Sun. So so-called spacetime curvature is gravity itself. The word "curvature" is a mathematical term. I don't think it should be taken literally as something curving. In gr, it refers to the generalized spacetime interval (the metric) changing globally in a gravitational field. Space warp (distance change): Imagine two points in empty space with a certain distance between them. Now place the Sun between the two points. Now, as seen from far away, the distance between the same two points is greater! One can think of this as space having been stretched by the mass/energy of the Sun. Time warp (time interval change): Imagine a clock in empty space. It runs at a certain rate. Now place the same clock near the Sun. It now runs slower. Time is slowed by the mass/energy of the Sun. Taken together and represented mathematically by the generalized spacetime interval, this slowing of time and stretching of space in the Sun's presence, this warping of spacetime is spacetime curvature is gravity. I hope this helps.I welcome comments and corrections.

Are you thinking of the amplitude? They can be positive or negative. You add the amplitudes then square the result. This is the probability of finding the particle in a certain location. And since you square, it is always positive.

Thank you for the enlightenment.

I believe the spacetime curvature (gravity) of a black hole is so strong it overcomes all forces, including atomic bonds and nuclear bonds. But i am not sure about your quark question.