# Relative time...

Discussion in 'Physics & Math' started by KneD, Jun 24, 2001.

1. ### KneDLe PenseurRegistered Senior Member

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can someone pls explain me why time goes 'slower' in the vicinity of mass.

I can imagine that time is relative.
But why is time influenced by gravity???

3. ### Spirit17Registered Member

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By no stretch of the imagination am I qualified to answer this question. But I'll take a stab at in anyway. Perhaps some one else can elaborate/replace!!!

My understanding is that gravity IS the warping of space/time. For instance, the very presence of an object (the earth), causes the space/time fabric around it to curve because of it's mass. The Earth's gravity keeps us firmly bound to it's surface, a surface that is spinning around at quite the velocity as well as keeping a firm orbit around the sun. The energy it takes for things to move through space is directly 'borrowed' from the energy we are moving through time with. It is theorized that all objects are moving through time constantly at the speed of light, thus, speed through space is the same energy only it's been diverted into speed through space. (hence, the assumption that light speed is unbreakable because there is no more energy possible).

5. ### KneDLe PenseurRegistered Senior Member

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NOTE:

When something (matter, photon, anything) falls into a black hole, it can never escape from the black hole.
So in fact, time stops for this 'something'.

Another point: When for example a rock falls into a black hole, we would see it like the rock is slowing down.
This is because of the light that is attracted by the black hole, so it takes longer to reach us.

I can understand all this.
So we can say that in a black hole time ends, and near a black hole we see things slow down.

But IS the rock really slowing down? When time slows down in the vicinity of a black hole, the rock isn't slowing down.

And, is it true what we see? I don't think so.
In my opinion it is just the light that makes it look like the rock is slowing down.
But in reality, the rock moves with an enormous speed (near the speed of light).

But why do scientists say that time IS slowing down near a black hole.....???

I don't get it.........

7. ### KneDLe PenseurRegistered Senior Member

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What I forgot to say; Thank you for this Spirit17, I've never looked at time/space this way....GREAT!!

8. ### JavierRegistered Senior Member

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Contribution

Okay,here goes my try,to complement Spirit 17 s:

As long as nothing can move faster than light,that means that the same event observed by different persons moving at different speeds,must deliver the same value for speed of light(C).

But as speed is constitued by space over time,to measure the same speed if your movement is very different from the one of the other observer,implies that are time and space what you will count diversely(and the same mathematical relation between them=C(10 secs 3000,000 kms,1 sec 300,000 kms));and as Spirit 17 said,the faster you move trhough space,the more you loss in time(because speed is a balance of the two factors,you can not aumengt one without diminishing the same part from the other):

Now,as energy equals mass,to apply an energy for accelerating an object is the same to increase its mass,or which is the same,a gravity field accelerates an object,thus reducing its path through time proportionally to the intensity of that gravitational field...

And if you were about to travel very near a blackhole(and be able to survive,somehow),and then go back to earth,you would be able to check out that a person born the same day you did looks much older,so time has passed differently in fact for both of you...

Last edited: Jun 26, 2001
9. ### thecurly1Registered Senior Member

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Javier, too much math bro.

Thanks for the Oxford version of your theory, let me simplify.
Space and time, though different dimensions are interwoven, just like the threads of a sweater.
When one is affected the other is mutually affected. To put this in a 2-D form, its like having a bowling ball sit in the middle of a rubber sheet. The rubber being space-time. The rubber sheet curves in towards the bowling ball. Actually in real space it's a little bit more like a bubble in the middle of a tank of water. Space-time is kinda pushed away.
Anyways, while matter is confined to the speed of light, energy isn't obviously. But few have raised the question about space-time. Can space-time travel faster than light, which travels in this medium. Since space-time, has no mass it theoretically should be able to travel faster, with little energy driving it (I.E.-the intertia from the big bang). If anyone would like to elaborate I'd be interested.

"I am putting myself to the fullest possible use, which is all I think that any conscious entity can ever hope to do." --HAL 9000, from 2001: A Space Odyssey

10. ### JavierRegistered Senior Member

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Less math

Hi,thecurly1

Hey,man, that was a very neat version of Einsteins conclusions,not my ones...

Yes,I ve heard about the expansion of the universe at more than lightspeed,this is called "inflationary expansion"and is used to explain the uniformity that the universe shows at big scale(this is all I know about it)...

But if you take a look at the mass of stars(galaxies of them)and planets and asteroids,etc,seems to me that the Big Bang was some very energetic event...

And, maths appart, matter cannot achieve lightspeed for it would be needed infinite energy to reach such acceleration;only massless particles(like photons), can,and as they consume all of the balance of speed travelling by space,they experiment zero time,and hence... are inmortal¡¡

11. ### thecurly1Registered Senior Member

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Sorry I wasn't more exact

Thank you for giving me kudos on concluding Einstein's theories. I'm well aware of how the theory of relitivity prevents matter from traveling at, or exceding the speed of light. As a matter of fact, I've written about it in two other threads.

I seem a bit confused about exactly what your were trying to prove or disprove about my thread. But besides that I was just saying that I believe that space-time, not the matter inside it, or light for that fact, but barren space-time may be able to travel faster than light, for it isn't matter or energy.

Thats all I wanted to say, thanks for sharing your oppions with me and the others at Scifourms.

12. ### CrispGone 4everRegistered Senior Member

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Small detail...

Hi Thecurly1,

Just a small detail perhaps: it is not really possible to speak of the velocity of the expansion of the spacetime structure. Velocity is defined as the amount of distance travelled in a specific time (even in the theory of relativity) but since spacetime defines the distance and the required time to travel, you're eventually going to wind up in trouble defining the expansion velocity (in more convenient astronomy, the expansion velocity is taken to the be velocity at wich matter receedes from us).

To talk about the expansion velocity requires a definition of what the universe is expanding into. The theory of relativity (used in this discussion) does not talk about that, so in a sense it's not really applicable. AFAIK the only theory capable of somewhat defining an expansion velocity would be string theory (by using the recently announced model of the universe as originated from a collision of branes).

Anyway, I'm just trying to point out that describing the universe as an object is not really as trivial as it seems.

Bye!

Crisp

13. ### JavierRegistered Senior Member

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Crisp,

Interesting¡

thecurly1:

I m not trying to disprove nothing of your opinions,just post my ones regarding yours and,more important,the general orientation of the author of the thread;you said "my" theory,I told you Einstein s;you asked about spacetime expanding faster than light,and I told you that indeed is thought to have happened,but as you perfectly understand for having posted repeatedly about this subject(sorry for not having read them¡¡),spacetime CONTAINS MATTER (that would be travelling faster than light but not relative to spacetime,in a theory counting relativistic restrains and a description of spacetime expansion,if I got right what Crisp explained) and therefore cannot expand without "carrying" it,for, as you already know,matter warps spacetime onto itself, i.e. attracts:

I quote you "since spacetime has no mass it theoretically should be able to travel faster":

This is why I thought useful to tell you that energy is massless and yet "confined to the speed of light"(mass is,precisely,confined OUT of the speed of light)

Ah,but you already know this all,didn t you?

Thanks for sharing your opinions with me and the others at Sciforums.

Last edited: Jun 30, 2001
14. ### James RJust this guy, you know?Staff Member

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31,341
Spacetime

When you're thinking relativistically, you have to throw away the idea that time and space are separate entities. Instead, we have a single 4-dimensional canvas called spacetime.

To sum up general relativity in a single quote: "Matter tells spacetime how to curve, and spacetime tells matter how to move".

Wherever there is mass, spacetime curves. That means that both space and time become different near a mass compared to far away from it. The "force" of gravity is another apparent effect of the spacetime curvature.