Relativity

when you travel at speeds approaching that of light, is that not similar to traveling through time? i mean, lets say you leave earth on your near light speed journey and when you return, you will have experienced less time on the spaceship than people have on earth according to relativity. isn't that time travel? sorry if this is an obvious question but i have seen lots of people asking if "time travel" was possible.

One of the main concepts of Special theory of relativity is that The velocity of light is a constant in all frames of reference. This concept includes the entire universe. But we havenot even explored 10% of the universe. Then how is it that we can generalise this law to the whole universe. Doesnot it look arbirary.

Ok well im new here and i have this question that i keep thinking about, to find answer to. Is it possible to create a Time Machine that can take you future/past in given location? or a Time Machine that can just take you in random time?

[math]E=MC^2[/math] [math]1 kg * C^2 = 8.98755179 * 10^{16} joules[/math] What is [math]8.98755179 * 10^{16} joules[/math] used for? Is this just a conversion from mass to energy or energy needed to accelerate it to a certain speed in a given time?

I was reading the book reinventing gravity by John Moffat. I was wondering wat your guys thoughts on it were? Specificially the idea behind dark matter not really being necessary? I think it even goes into the inflationery theory not being needed as well. It's been a while since i could talk physics with anyone...Which I really don't understand. It's so interesting, The very making of yuor existence...i mean....how is that anyway boring? anyways here is some background info: http://www.space.com/scienceastronomy/071029-mm-mog-theory.html

does bent space use energy? if so, where does it get it? i dont see how it could condense something to singularity without using a vast amount of it. well, i do, but im curios. could you use bent space to make energy? i know it goes against the whole energy cant be made or destroyed, only converted to different forms, but i dont see why it couldnt. maybe have something on a {big} planet that makes energy from the compression being put upon it by that bent space.

Is the Chaos Theory relevant when it comes to time travel in terms of relativity? Let me lay out an example. A person (A) has figured out a way to go back in time. He travels back in time and somehow prevents his own conception. According to the Chaos Theory, he should simply blink out of existence, but I think not. He has traveled back in time, yes, but his actions in the past will have no bearing on the future that he left. It is true that if A prevents his own conception, he will not be born in this time, but he was still born in another time. I think of it as a sort of parallel universe. In the same way that a 2-dimensional "being" can go from one place to another…

Now" And the Big Bang The universe only exists "now". Its future is yet to come and its past is but history reflected as a collection of successive previous "nows". The "now” at the time of the big bang would have to have a history of previous "nows" or would have had to spontaneously come into existence. Such history could reflect a steady-state or a collapsing. I find the latter more palatable. With this we could envision a universe collapsing into the Big Bang, expanding and then collapsing again into a Big Bang in a cycle having no beginning and no end.

There is a new book out called Einstein's Mistakes, by Hans C. Ohanian. Ohanian is a really good relativist and an excellant textbook author. I just got a copy of this book. So far is prettty good. Its nice to have a good source like this so one can have a ready reference to Einstein's mistakes, especially since so many people like to think they've proven Einstein wrong. At least this book gives an authoritative collection of his real mistakes and not the claims of his mistakes. Good reading so far. Pete

The space twin after having run at a speed approaching the speed of light has docked in space. The earth twin visits him in his own space having traveled at a slower speed. When they meet in space it is the year 2000 on the space twin’s calendar,and the year 2010 on the earth’s twin’s calendar. When the earth twin steps aboard the space twin’s ship does he experience the calendar year 2000? If so what happens to his history to the year 2010?

If relativistic mass is only seen by an observer outside of the particular frame in question, it must be an illusion. You could have several inertial frames moving about at different speeds and no one could agree on the relativistic mass of each one, yet they would all agree that their own mass is at rest.

Every once in a while I think of a scenario that I can't figure out in my head. I'm sure the solution is simply something I missed, but here it is: 2 ships in Earth's reference frame... we'll call it 'frame 1'. So Two ships leave Frame 1 and accelerate in a given direction: (we'll call it:) North. They accelerate together until they are traveling with a velocity of .99c relative to frame 1... So they have a relativistic factor of about 7... which means that (among other things) their clocks are now running 7 times slower than frame 1 clocks. The ships are at rest relative to each other and we'll call their current reference frame 'frame 2' In the next paragraph, w…

this time dilation stuff is just so hard to wrap my head around. i get what the twins paradox says it would do, but i dont understand why it happens. i just dont see how something can age different if its moving at a different speed. please, any help? thanks.

This may be in the wrong forum, but I'm told it's due to relativity, so this seems a decent place to put it... Occasionally as a chemist I have to deal with - eek - maths, some of which involve electron rest mass (for example). My question is, how is this measured? It seems absurd to suggest somehow isolating and 'freezing' an electron in its tracks, so I can only assume it's an extrapolation. It's something I've been curious about for some time. On a related note - why do we use 'rest' as a point of reference, if it is (as I assume above) strictly hypothetical? Why not the mass at a given energy? Math welcome in answers, though commentary would be appreciated…

What are the units of the metric : It seems components can have different ones ?

One of the foundations of GR as we were taught at school is that there is no way to differentiate between a force felt due to acceleration and a force of the same magnitude caused by a gravitational field. However, the acceleration caused by a rocket (for example) is linear, everything is being pushed in the same direction. A gravitational field, however, is invariably curved in some way....if I hold my arms out and drop a coin from each hand they won't fall in the same direction, they'll converge slightly because they're both heading towards the same place, the centre of the Earth. So given that an infinite plane (to give a perfectly linear gravitational field) …

Is it allowed to write : [math] G_{\mu\nu}(g)=R_{\mu\nu}-\frac{1}{2}g_{\mu\nu}R+\Lambda g_{\mu\nu}+\Lambda^1_{\mu\nu}=\kappa T_{\mu\nu} [/math] where [math]\Lambda^1_{\mu\nu}[/math] is a constant symmetric tensor (depending neither on space nor time)...and other symbols well-known in GR. We find, since in vacuum the Minkowski metric is a particular solution in cartesian coordinates, that [math]\Lambda^1_{\mu\nu}=-\Lambda \textrm{diag}(1,-1,-1,-1)[/math]. Else, could someone give a comprehensive summary of the conditions on [math]G_{\mu\nu}[/math] forbidding similar constant (of integration?) ?

The formula [math]E=mc^{2}[/math] is estimated as one of the top ten of most beautiful formulae at any epoch, but the its demonstration at firth contained mistake by just Great Einstein! The lack of logical fundamental of the Einstein had advised by Aivs in “Journal of the Optical Society Of America”, 42, 540 – 543. 1952. After that, nobody take author’s demonstration no more, but use dependent of inertial mass from velocity of a body: [math]m = \frac{m_{0}}{\sqrt{1-v^{2}/c^{2}}}=m_{0}\gamma[/math] (1) together with the Newton’s 2 law: [math]F = \frac{d(mV)}{dt}[/math] (2) for calculation that formula. But, the new mistake appear and, perhaps, in this situation, not …

My thoughts are, we cant go back in time, the reason for this is, it already happened, if this is so, time cant happen twice. If you dont agree, Why????

We are going to travel 113,242 light years across the Milky Way starting at rest in our galaxy's inertial frame near an outer edge. We will use a continuous 1G of acceleration the entire distance. The table below is from http://math.ucr.edu/home/baez/physics/Relativity/SR/rocket.html T= time in rockets inertial frame t= time in earths inertial frame d= distance in light years v= light speed Y= time dilation T --------- t ----------- d ----------- v -------------- γ 1 year --- 1.19 yrs ----- 0.56 lyrs --- 0.77c ----------- 1.58 2 ------- 3.75 -------- 2.90 -------- 0.97 ----------- 3.99 5 ------- 83.7 -------- 82.7 -------- 0.99993 -…

The Static Universe that Einstien predicted will come true. http://www.eurekalert.org/pub_releases/2007-05/cwru-cpa052407.php http://en.wikipedia.org/wiki/Static_universe

I have been trying to grasp the basics of "stress-energy tensor" and most information I have found starts above my head. I hope the basic concept can be put in English words without a ton of complicated math. It seems like more then just mass is being considered in GR when calculating the curvature of spacetime. Is that what it is all about? Links and explanations welcome.

what actually is a time, is a confusing question. i have got a real funny answer for it. can we explain time as distance between two point relative to observer with velocity c in the universe?? as i am a amature, this is a vague idea to think of(no scientific ideas or thoeries to support my idea). what actually is a time??

if ive read and watched correctly, einstein concluded that you can esseintelly travel back in time, or at least ''escape'' it, by travelling at the speed of light. how? i watched a thing on the history channel were there was an astrounaught on there, who had a twin brother, and when he went in to space, he went so fast that he is now actually like .511 seconds younger than his brother now. how? can anyone help me out here?

if you have a propeller spinning fast enough SR says time dilates with velocity so you get a gradient of time(s?) between the hub of the propeller and the tip. does this mean the propeller is bent in time? if it is bent, could it somehow be frozen in that bend so it remained curved after it stopped spinning? would such a thing bend space?