# Naked Science Forum

## Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Jealbr on 27/03/2016 22:10:50

Title: Time Dilation Gravity + Acceleration
Post by: Jealbr on 27/03/2016 22:10:50
This is my first post here guys, I was inspired to register because I ponder quite often and always seem to bottleneck to a point that I dont have any knowledge on. Anyway here's my question.

As far as I know when someone/something is close enough to a very powerful gravitational field they may experience a difference in time when compared to someone/something outside of that field. time for them will travel much slower compared to those outside of it, for example they would experience 1 hour from their perspective while the outside observer would experience perhaps a day. Something similar also happens when something travels at the speed of light, or as you approach it. Example, from a photons perspective the moment it leaves any given star and the moment it is absorbed by say an human eye is the same, while from an outsiders perspective it would take as many years as however many light years away the star was. If any of the above was wrong please correct me. Anyways to get to the question/s I have is could there be a mass that has a gravitational pull so strong that it would 'slow' someones time down to 0. If so could you not just simply add to that mass increasing its time dilating effects pushing it negative? If not then what would happen if you could say approach the speed of light while inside a very powerful gravitational field? I'm not sure but shouldnt a combination of some of the above result in someone/something moving in a negative time trajectory?

TL;DR Is there a limit to gravitational time dilation and/or compounding gravitational and acceleration time dilation or mathematically could some combination of these result in negative time?

I'd like to say thanks in advance for any responses and I'm definitely looking forward to finally getting answers to the questions that put my thinking to a standstill.
Title: Re: Time Dilation Gravity + Acceleration
Post by: Thebox on 28/03/2016 17:47:02

Anyways to get to the question/s I have is could there be a mass that has a gravitational pull so strong that it would 'slow' someones time down to 0.

Hello, it is the other way around, move away from a gravitational field and time slows down, approach a greater magnitude gravitational field time speeds up.

Title: Re: Time Dilation Gravity + Acceleration
Post by: timey on 28/03/2016 18:12:49

Anyways to get to the question/s I have is could there be a mass that has a gravitational pull so strong that it would 'slow' someones time down to 0.

Hello, it is the other way around, move away from a gravitational field and time slows down, approach a greater magnitude gravitational field time speeds up.

Oy... That's my theory... Lol!

However - according to "accepted physics" you have got it the wrong way round.  Time does slow for a body undergoing high velocity.  (Usually associated with travelling in space)  But... time slows the closer you get to a gravitational field, ie: in a stronger gravitational field, and time gets faster in the weaker gravity field.
Title: Re: Time Dilation Gravity + Acceleration
Post by: Thebox on 28/03/2016 18:16:50

Anyways to get to the question/s I have is could there be a mass that has a gravitational pull so strong that it would 'slow' someones time down to 0.

Hello, it is the other way around, move away from a gravitational field and time slows down, approach a greater magnitude gravitational field time speeds up.

Oy... That's my theory... Lol!

However - according to "accepted physics" you have got it the wrong way round.  Time does slow for a body undergoing high velocity.  (Usually associated with travelling in space)  But... time slows the closer you get to a gravitational field, ie: in a stronger gravitational field, and time gets faster in the weaker gravity field.

No its the other way around, the Caesium at ground state beats faster than the Caesium in flight.  Time slows down for the observer in motion, what do you mean your theory, that is how  it works isn't it and the present theory ?

I think what you may be referring to is the center of mass and time stops then.

Title: Re: Time Dilation Gravity + Acceleration
Post by: timey on 28/03/2016 18:32:46
K... Have it your own way!  But please know I'm just giving a brief synopsis of classic text book stuff... Just saying.  You might check on wiki perhaps.
Title: Re: Time Dilation Gravity + Acceleration
Post by: Colin2B on 28/03/2016 19:02:40
TL;DR Is there a limit to gravitational time dilation and/or compounding gravitational and acceleration time dilation or mathematically could some combination of these result in negative time?
Your understanding of time dilation is correct, as Timey says. (Hey Timey, we agree on this!  [;)])
Increasing speed and increasing gravity both increase the amount by which clocks run slow as seen by an observer at rest. The fastest running clocks are those in a zero gravity field or free falling.
When speeds near that of light are added together they do not add arithmetically, so a rocket travelling at 1/2 speed of light, might launch a missile at 3/4 speed of light but the resultant speed of the missile will be less than the speed of light see http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/einvel.html

Even if we could combine gravity and speed to slow time right down, it won't go negative. Think about a car braking, it stops, it doesn't go backwards, it would need an extra force to do that.
Title: Re: Time Dilation Gravity + Acceleration
Post by: Thebox on 28/03/2016 19:46:16
K... Have it your own way!  But please know I'm just giving a brief synopsis of classic text book stuff... Just saying.  You might check on wiki perhaps.

I drew it

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t is clock

Title: Re: Time Dilation Gravity + Acceleration
Post by: Bill S on 28/03/2016 20:52:48
Hi Jealbr, welcome to TNS.

I am not an expert, so will not attempt to offer answers.  However, there are one or two things I have done some thinking about, so here are some thoughts.

Quote
Something similar also happens when something travels at the speed of light, or as you approach it.

Only massless particles can travel at “c”, so there is a fundamental difference between approaching “c” and travelling at “c”.

Quote
Example, from a photons perspective the moment it leaves any given star and the moment it is absorbed by say an human eye is the same

There is a lot of discussion about this, but it is probably not scientifically possible to establish if a photon can be said to have a “perspective”.

Attempting to assign a reference frame to a photon is pushing special relativity beyond its limit.

Quote
…could there be a mass that has a gravitational pull so strong that it would 'slow' someones time down to 0.

I don’t know, but I suspect that such a mass would have to be infinite; which would not be possible.

Title: Re: Time Dilation Gravity + Acceleration
Post by: evan_au on 28/03/2016 21:53:57
Quote from: Jealbr
could there be a mass that has a gravitational pull so strong that it would 'slow' someones time down to 0.
If you approach the event horizon of a black hole, time slows down to a near standstill.

Extrapolating this, as you cross the event horizon, in theory time would stop for you; but noone will ever know, because no signals can reach outside the event horizon to tell anyone what it is like.
- If you are falling directly into a black hole, your speed will increase to a significant fraction of the speed of light - so the experience won't last very long!
- On the other hand, if you are in orbit close to the event horizon of a massive black hole (eg the one near the center of our galaxy), your orbital velocity will be a significant fraction of the speed of light. Time would be significantly slowed. Just watch out for any other matter also orbiting at relativistic speeds - a grain of sand striking at these velocities would go off like an atomic bomb!

Quote from: TheBox
the Caesium at ground state beats faster than the Caesium in flight.
Here we are talking about measuring time with a Caesium clock (http://en.wikipedia.org/wiki/Caesium_standard).

These clocks utilize the periodic oscillation of electrons in the ground state of Caesium, which is defined to beat at 9,192,631,770 Hz, for someone in the same laboratory (in the same frame of reference).

The "ground state" means that there is no lower orbital into which an electron can fall.
- It does not mean that the Caesium clock is sitting "on the ground".
- It does have to do with the temperature of the Caesium atom - if it is heated to a plasma, it is no longer in the ground state, even if your lab is on the ground floor.

Whether the Caesium atom is in the ground state or not has nothing to do with the velocity of the Caesium clock - it could be on the Earth, orbiting around the Sun, or on a satellite orbiting the Earth, or in deep space on its way to Alpha Centauri.

Whether a Caesium clock in another frame of reference seems to beat faster or slower than the one in your lab depends on both the relative velocity and the relative gravitational field. A clock orbiting close to the Sun (eg near Mercury) would tend to beat slightly slower than one on Earth; one orbiting far from the Sun (eg out near Pluto) would tend to beat slightly faster than one on Earth. This effect is modified by the relative velocity - clocks traveling at high relative velocity seem to beat more slowly than clocks that are stationary compared to the one in your lab.

So you can't make a general statement about behavior of another Caesium clock "in flight" without providing more information.
Title: Re: Time Dilation Gravity + Acceleration
Post by: Thebox on 29/03/2016 08:28:30

So you can't make a general statement about behavior of another Caesium clock "in flight" without providing more information.

My apologies, it was presumption of me to assume the poster of the question would automatically know what I meant by the Caesium in ''flight'' and understand the importance of why brief answers can lead to ambiguity. Let us face it the Caesium does not have wings, I should of explained the Keating experiment and answered in full, sorry for my lazy reply.

Title: Re: Time Dilation Gravity + Acceleration
Post by: JoeBrown on 29/03/2016 09:03:18
...
I think what you may be referring to is the center of mass and time stops then.

In general or General Relativity (GR) specifically, this statement is incorrect.

In GR its relevant to note this statement would hold true only in a very limited set of circumstances.

1. it's highly unlikely that a blackhole or singularity would be limited to the exact amount of mass for this statement to hold true.

2. in theory GR breaks logic when a blackhole contains more mass than the exact amount.

This is not necessarily due to a flaw in GR.  It happens that the consequence of exceeding the critical exact solution requires that space-time definition must change to somehow reflect an opposing meaning to that which is understood on the outside of the singularity point.

Possible solutions might be:   (inability to verify by experiment, they are only theory, no proof)

1 would be that time runs backward.

2 space would have an anti-space quality

3 perhaps a combination of both 1 & 2
Title: Re: Time Dilation Gravity + Acceleration
Post by: Thebox on 29/03/2016 14:13:59
...
I think what you may be referring to is the center of mass and time stops then.

In general or General Relativity (GR) specifically, this statement is incorrect.

In GR its relevant to note this statement would hold true only in a very limited set of circumstances.

1. it's highly unlikely that a blackhole or singularity would be limited to the exact amount of mass for this statement to hold true.

2. in theory GR breaks logic when a blackhole contains more mass than the exact amount.

This is not necessarily due to a flaw in GR.  It happens that the consequence of exceeding the critical exact solution requires that space-time definition must change to somehow reflect an opposing meaning to that which is understood on the outside of the singularity point.

Possible solutions might be:   (inability to verify by experiment, they are only theory, no proof)

1 would be that time runs backward.

2 space would have an anti-space quality

3 perhaps a combination of both 1 & 2

Interesting point,  but talking about a point, what about the C.O.M , 0 point source?

Title: Re: Time Dilation Gravity + Acceleration
Post by: JoeBrown on 29/03/2016 15:04:32
Interesting point,  but talking about a point, what about the C.O.M , 0 point source?

I'm sorry, but I request clarification because the topic is inherently complex and I can infer intended meaning of "point source" in context too many ways.  If I infer part of your question clarification becomes and ASSuMEing problem, further complicating an already complex question.

I think I can reply to the question.  Presently I have been and am still trying to workout a problem related to GR (and my understanding thereof) that I also see as inherently complex and horrifyingly difficult to resolve.

The problem I'm working on is one of avoidance and consequences.  When one referrers to all bodies of mass as in prospective of COM as a point, size of mass complicating GR can be completely ignored (avoidance) as to having any consequence in relevance as an additional dimension to contend with.

COM has no size.... if it's always referred to as a point.
Title: Re: Time Dilation Gravity + Acceleration
Post by: Thebox on 29/03/2016 15:10:42
Interesting point,  but talking about a point, what about the C.O.M , 0 point source?

I'm sorry, but I request clarification because the topic is inherently complex and I can infer the "point" meaning.  If I infer part of your question clarification becomes and ASSuMEing problem, further complicating an already complex question.

I'm always complicated in my thought , to clarify , the dead center of a point source,  or to express in maths

4/3 pi r³   -   4/3 pi r³

or

r1-r1

A volume take away an equal volume , equals absolute nothing or a 0 point.

ok?
Title: Re: Time Dilation Gravity + Acceleration
Post by: Thebox on 29/03/2016 15:25:18

COM has no size.... if it's always referred to as a point.

Yes exactly that points and zero points being the com

Title: Re: Time Dilation Gravity + Acceleration
Post by: JoeBrown on 29/03/2016 16:27:20

Yes exactly that points and zero points being the com

I started working a theory that had nothing to do with this (or so I thought).

I love contemplating GR because it's a simple solution to a problem I never would have realized existed.

However!!!!  GR has a problem, seems nobody remembers to go back and fix.

zero point concept makes no allocation for size of mass.  size of mass is a separate dimension that is ignored and avoided.  Problem identified consequences unknown because of ignorance requirement.

Whoah.  I'm having a hard time spelling that out clearly in my own head.  Hope I got the "point" across.
Title: Re: Time Dilation Gravity + Acceleration
Post by: JoeBrown on 29/03/2016 16:31:18
State it another way, one cannot solve a problem of a singularity solution when the problem starts with a singularity solution, when one wishes to address a problem of the singularity solution.

NO! that simply hurts my head.  But it works.  I'm trying to simplify the problem by spelling it out as simple as possible.

One would note, the current topic of discussion is off topic.  It deserves a thread of its own.  This thread brought to the divergent topic to my attention, prior to COM being referred to as the specific cause of divergence.  I'll be starting a new thread shortly.  I (was drawing just a few moments ago...) drew a picture I've may have referred to before but never have drawn until now.

Why does everything simple always gotta be so complex?
Title: Re: Time Dilation Gravity + Acceleration
Post by: evan_au on 30/03/2016 21:16:32
Quote
zero point concept makes no allocation for size of mass.
But astronomers do take size into account (mass and size together define density).

A star with 1.4 times the mass of the Sun:
• is fine as long as it is burning Hydrogen, and is a main-sequence star roughly the size of the Sun.
• is fine as long as it is burning Helium, and is a red giant roughly the size of the Earth's orbit.
• is fine as long as it is not actively fusing matter, and is a white dwarf shrinking to much less than the size of the Sun.
• at some point as it shrinks further, this white dwarf will exceed electron degeneracy pressure, quite possibly forming a black hole.
Title: Re: Time Dilation Gravity + Acceleration
Post by: Bill S on 30/03/2016 22:05:56
Quote from: Evan
If you approach the event horizon of a black hole, time slows down to a near standstill.

Extrapolating this, as you cross the event horizon, in theory time would stop for you;

Quote
If you are falling directly into a black hole, your speed will increase to a significant fraction of the speed of light

How could anything continue to happen if time had stopped in your RF?

Isn’t the apparent stopping of time something that is seen only in the RF of an outside observer?
Title: Re: Time Dilation Gravity + Acceleration
Post by: jeffreyH on 30/03/2016 23:04:30
At relativistic levels the expression for the energy of electron degeneracy is of the form

The equation for rs is rs = (2Gm)/c^2. This can be rearranged as 1/(2m) = G/(c^2rs). The energy equation then becomes (h^2k^2G)/(c^2rs). Whether this bears any relationship to black hole collapse depends upon whether it is valid to derive the equation in this way. I personally can't say. BTW for h read hbar above.
Title: Re: Time Dilation Gravity + Acceleration
Post by: jeffreyH on 31/03/2016 23:48:55
Now the interesting question. What type of boson would the above expression lead to to describe the state of matter behind an event horizon?
Title: Re: Time Dilation Gravity + Acceleration
Post by: Jealbr on 02/04/2016 03:12:57
Thanks so much for all the great replies and discussion! I got a little lost during the progression of the thread, when everyone was talking about the COM etc. Could someone explain what they were discussing in a more basic way?
Title: Re: Time Dilation Gravity + Acceleration
Post by: Thebox on 02/04/2016 11:07:40
Thanks so much for all the great replies and discussion! I got a little lost during the progression of the thread, when everyone was talking about the COM etc. Could someone explain what they were discussing in a more basic way?

The COM is the center of mass, no different to the center of anything,   take any object and measure its dimensions, at the center of a singular central point of an object is the center.

see this dot (.)

the center of that is the center of mass, a 0 point.

This is why singularities are mentioned because i........................................i   is n -dimensional and multidimensional and can't really be measured without uncertainty principle.

A problem is , imagine a cube and taking a chunk out of the cube, there is now two center of masses, and so on if you split it up more.

Title: Re: Time Dilation Gravity + Acceleration
Post by: evan_au on 02/04/2016 12:21:45
Quote from: Bill S
How could anything continue to happen if time had stopped in your RF?
Isn’t the apparent stopping of time something that is seen only in the RF of an outside observer?
Mathematicians often "cheat", and just describe the behavior as you approach a point where some property becomes infinite. If they can't reformulate the problem so the infinity disappears, they just avoid talking about it.

Imagine a distant observer watching a space probe orbit a black hole once per day (measured relative to the distant stars).
If the space probe is close to the event horizon, time may be slowed by a factor of 2 for the space probe. Comparing to the position of the distant stars, they will see their orbit as taking only 12 hours, according to their onboard clocks. In other words, the space probe has a wilder ride than that seen by the distant observer.

The closer to the black hole the space probe approaches, the more dizzying the ride for the space probe, even though the distant observer sees the orbit as being much more sedate.

So, emulating the mathematicians, I would say that the time dilation becomes more extreme the closer the space probe approaches to the event horizon. The space probe ride becomes ever more dizzying the closer the space probe approaches to the event horizon. So things appear to happen faster the more time is slowed for the space probe.

Once the space probe reaches the event horizon, the distant observer would just see a faint glow from the space probe, rapidly red-shifting into oblivion. Like a mathematician, we can only speculate on how this gut-wrenching ride ends for the  space probe (and avoid talking about it with any authority).
Title: Re: Time Dilation Gravity + Acceleration
Post by: jeffreyH on 02/04/2016 12:56:46
An orbit by definition is on average perpendicular to the gravitational field. In an elliptical orbit it is exactly perpendicular at the two extremities. With parabolic trajectories perpendicular velocity is unaltered. This means that any trajectory that misses contact with the central object must be defined differently to an impact trajectory. Here is a thought experiment. Take an object at rest at infinity and calculate its instantaneous velocity on impact with a massive object. Now do this same calculation with the object at infinity starting off with a velocity 99.99% light speed. What prevents the wild riders on that object from experiencing superluminal speed at some point before impact? Time dilation must increase due to special relativistic effects and be further increased by general relativistic effects.