Theory Of Time

[jaychant 0]

I believe the answer is more simple than all the scientific examples listed above.
If an object/vehicle was capable of traveling faster than the speed of light (note that there is no limit to speed, so it is possible in theory to go incredibly fast).

Einstein may have stated that an object was incapable of travailing faster than that speed because of friction (Ie. The thing catching fire and melting the people, cows, monkeys, etc--) But if something were put up which defies the laws of heat, similar to what NASA uses to protect the ship on its reentry into earth-- it is possible to conclude that an object can indeed travel faster than the speed of light.

Now, this may or may not mean that time travel is possible. You might just be getting to a very far place at a very fast time. I'd be kinda like saying a vehicle was capable of flying from Africa all the way to LA, California in 1.2 seconds. It's possible, but as far as moving forward, or backward in time-- I do not think it's possible.

I believe that the present time and reality is stable, hence-- going hella fast to a certain place wouldn't mean you went 500 years into the future. It would mean you got to some unknown galaxy, or whatever very quickly.

I could be wrong-- so it should be noted that my examples were opinion-based.

Actually, the reason things can't travel faster than (or even at) the speed of light is not because of friction, but because it would require an infinite amount of energy to do so (am I right to call this inertia?).

You are entitled to your opinion, but Einstein's theories have been proven on several levels, whereas your ideas have very little or no evidence. So you may be right, but the chance of that is very slim.

About the time thing: The theory is as you approach the speed of light, time slows down, and when you reach the speed of light, time comes to a stop. This isn't traveling through time; rather, it means that when you go faster, time passes slower from your perspective than it does in the real world. This means that if you travel at the speed of light to a star 8 lightyears away and back, the trip would take 16 years, but from your perspective, no time would have passed. This would also mean that you wouldn't age during the trip. Since you can't go past the speed of light, this can't cause time to go backwards. If it did, it would make you younger, but it can't because it isn't possible to go beyond the speed of light.
Edited March 28, 2009 by jaychant (see edit history)

[rvalkass 5]

Why is its relativity to the earth considered?

You just need a reference point. You could just as well do it from Mars, specifically from your house, whatever...

 

...to avoid confusion. Okay, let's see if i can add these things up. For simplicity's sake, let's stick to the ever-so-common E = mc² equation. Is it safe to assume that m here would = rest mass xor relativistic mass?

That part is the rest mass, and therefore calculates the rest energy of the particle (ie. the energy locked up in its mass while it is not moving).

 

Assuming it is, that would mean in order for the photon to reach the speed of light it would have to be at rest and bear 0 energy (i.e. E = 0), because anything multiplied or divided by zero is zero.

Not always. More often than not, dividing by zero leads to an infinity rather than zero.

 

However, you mention earlier that the photon carries energy regardless... But if it is at rest, how can it reach the speed of light? And how can it still have energy though E equals 0?

This is one area where the 'simplified' equation breaks down. With zero energy, the photon must have zero rest mass, and therefore doesn't exist (which makes sense). However, it still has relativistic momentum and therefore relativistic mass. This can contribute to the energy of the photon. This does give photons a small apparent mass when the move. High power lasers have actually been used to push objects around, implying the photons must have a (very small) mass and can exert a force.

[truefusion 3]

You just need a reference point. You could just as well do it from Mars, specifically from your house, whatever...

Does that imply that the speed of light cannot be determined without a reference point? I know the speed of light was (is) in the implied equation itself, but if these objects require a reference point, doesn't it follow that in order to determine the speed of anything else would itself require a reference point? Or perhaps better put: Why does the speed of light not require a reference point while everything else, as implied, does?

 

That part is the rest mass, and therefore calculates the rest energy of the particle (ie. the energy locked up in its mass while it is not moving).

So m always equals rest mass? But now you've introduced rest energy. How many invisible or hidden adjectives are there? And how does this word game fit into the all the equations that have been mentioned?

 

Not always. More often than not, dividing by zero leads to an infinity rather than zero.

Division by zero, at least from my knowledge, can only have three values: undefined, 0 or infinity. That means infinity is in the minority, and the reason why it's even considered a possible value is not because it is logical from a mathematical standpoint—that is, you really have to play around with everything in order to even consider the possibility of infinity. So wouldn't it be special pleading to go with infinity? What objective arguments are used to pick infinity over the others? If i were to assume that infinity is picked for the sake of progressing (since undefined or 0 is bound to prevent progression), that would be fallacious because anything following it would not be entirely accurate. If it's not entirely accurate, then we cannot claim anything following it to be absolute. So what's the reasoning behind choosing the minority?

 

This is one area where the 'simplified' equation breaks down. With zero energy, the photon must have zero rest mass, and therefore doesn't exist (which makes sense). However, it still has relativistic momentum and therefore relativistic mass. This can contribute to the energy of the photon. This does give photons a small apparent mass when the move. High power lasers have actually been used to push objects around, implying the photons must have a (very small) mass and can exert a force.

Given the equation, isn't the reason why it has no energy is because its rest mass is 0? Or are you flipping the equation around? But mind doing the non-simplified equation for me?

 

But if the photon doesn't exist, how can it still have relativistic mass? That would mean it would have to be brought into existence (i.e. created) and would have to be in motion the very instant it was brought into existence.

[rvalkass 5]

Does that imply that the speed of light cannot be determined without a reference point? I know the speed of light was (is) in the implied equation itself, but if these objects require a reference point, doesn't it follow that in order to determine the speed of anything else would itself require a reference point? Or perhaps better put: Why does the speed of light not require a reference point while everything else, as implied, does?

Everything else requires a reference point ebcause its speed is relative to the observer. For example, if you are doing 55mph on the road, and pass a car doing 50mph, your speed relative to the slower car is 5mph. However, relative to the ground, your speed is 55mph. This is the reason why we have to declare reference points when talking about velocities. However, the speed of light is a constant and not relative to anything.

 

So m always equals rest mass? But now you've introduced rest energy. How many invisible or hidden adjectives are there? And how does this word game fit into the all the equations that have been mentioned?

Generally m₀ is used for rest mass, and m for general mass (whatever seems appropriate at the time ) but I'm fairly lazy with writing all this down. Sorry. Rest energy is related to , and is the energy an object has locked up in its mass, ie. if you converted all its mass into energy, what would you get?

 

 

Division by zero, at least from my knowledge, can only have three values: undefined, 0 or infinity. That means infinity is in the minority, and the reason why it's even considered a possible value is not because it is logical from a mathematical standpoint—that is, you really have to play around with everything in order to even consider the possibility of infinity. So wouldn't it be special pleading to go with infinity? What objective arguments are used to pick infinity over the others? If i were to assume that infinity is picked for the sake of progressing (since undefined or 0 is bound to prevent progression), that would be fallacious because anything following it would not be entirely accurate. If it's not entirely accurate, then we cannot claim anything following it to be absolute. So what's the reasoning behind choosing the minority?

The use of infinity comes from a limit, a bounding condition. Take y=1/x. Let x get smaller and smaller, and y will rapidly increase. As x tends to 0, y tends to infinity. It describes the change based on the trend so far. Smaller numbers for x make y go up, and we can reasonably expect it to continue to do so. The same occurs in the relativity equations. As v tends to c (ie. you get very close to the speed of light), v/c will tend to 1, giving us sqrt(1-1), which is 0. The reason why we say at this point we get infinite energy, is because when v is very slightly smaller than c, you get very high values for the energy. You expect that to continue, and it makes physical sense based on our current knowledge.

 

Given the equation, isn't the reason why it has no energy is because its rest mass is 0? Or are you flipping the equation around? But mind doing the non-simplified equation for me?

I phrased it somewhat badly. Basically, if you say the energy of a photon is zero, then it can't be there, which makes sense. No light (or other electromagnetic radiation) = no photons. This also fits with them having zero rest mass. However, with the simplified equation there is no opportunity to introduce another 'source' of energy, so the photon would never exist. With the full equation we can include its relativistic mass and kinetic energy:

 

 

(It wouldn't display it correctly )

 

But if the photon doesn't exist, how can it still have relativistic mass? That would mean it would have to be brought into existence (i.e. created) and would have to be in motion the very instant it was brought into existence.

This introduces wave particle duality. The photon, in certain cases, is just a wave transferring energy. These waves are created all the time - they're just energy moving from one place to another. However, in other cases it can act as a particle (normally when interacting or colliding with something).

[truefusion 3]

Everything else requires a reference point ebcause its speed is relative to the observer. For example, if you are doing 55mph on the road, and pass a car doing 50mph, your speed relative to the slower car is 5mph. However, relative to the ground, your speed is 55mph. This is the reason why we have to declare reference points when talking about velocities. However, the speed of light is a constant and not relative to anything.

Isn't the speed of light observed also (though the speed of light may be measured hypothetically in free space)? But to better explain what i mean, i'll use the example you provide but change one of the objects. That is, let the ground be the ground and have the car i'm in be the slow car, but change the fast car to light and have its speed be the speed of light. That is, relative to the ground i'm going 50mph and light is going approximately 669,600,000mph. My speed relative to the speed of light is 669,599,950mph slower. Being the scenarios similar, i don't understand why the cars aren't themselves constant or why the speed of light still remains or continues to be considered a constant.

 

The use of infinity comes from a limit, a bounding condition. Take y=1/x. Let x get smaller and smaller, and y will rapidly increase. As x tends to 0, y tends to infinity. It describes the change based on the trend so far. Smaller numbers for x make y go up, and we can reasonably expect it to continue to do so. The same occurs in the relativity equations. As v tends to c (ie. you get very close to the speed of light), v/c will tend to 1, giving us sqrt(1-1), which is 0. The reason why we say at this point we get infinite energy, is because when v is very slightly smaller than c, you get very high values for the energy. You expect that to continue, and it makes physical sense based on our current knowledge.

That's what i thought—even though once you reach zero you stop getting closer to the speed of light; which means you can't call anything that follows after it absolute.

[freenrg 0]

Hi rvalkass,

 

This topic is great. I am glad I found it. You seem to know quite a bit about this.

 

Here are some questions for you:

 

QUESTION 1.

How do we determine that an object is in motion?

 

QUESTION 2.

Newton used space as an absolute frame of reference?

Einstein said this was incorrect. Does Einstein use space-time as a frame of reference?

 

QUESTION 3.

As an object accelerates (I am assuming we have answered the previous questions) , time measured on that object slows down with respect to time measure on an object that is at rest.

Is this correct?

 

Let me know if you think I must rephrase my questions.

Thanks

[rvalkass 5]

QUESTION 1.

How do we determine that an object is in motion?

Mainly you detect its change in position relative to another object. So, if the distance between two cars decreases you can be confident there is some motion involved. How do we know which is moving? Use other reference points. If you can see one car is not moving relative to a nearby tree, you can say the other car is in motion relative to the first one.

 

The difficulty comes when there are no other reference points. If you've ever been in a traffic jam, especially next to a truck, and the truck pulls away, you can appear to be moving backwards. As you have no other reference, this is one option. The other, of course, is that the truck has moved forwards. Until you look round and see you are still relative to other cars, trees, etc. it is impossible to tell.

 

QUESTION 2.

Newton used space as an absolute frame of reference?

Einstein said this was incorrect. Does Einstein use space-time as a frame of reference?

An absolute frame of reference is generally considered to be one where Newton's laws of motion are valid. The problem was with Newton's original definition. He assumed that the stars were stationary and therefore could be used to create a stationary reference frame. This is not true, as we now know. Einstein extended this to say an inertial reference frame was one where light travelled at the speed of light in all directions, irrespective of wavelength.

 

However, Einstein also suggested we can't have an overarching inertial reference frame as it is impossible to tell if one exists. It is impossible to tell if a dropped object accelerates downwards due to gravity, or if everything else is moving upwards. As odd as that may sound, it is the same as the traffic jam analogy above.

 

QUESTION 3.

As an object accelerates (I am assuming we have answered the previous questions) , time measured on that object slows down with respect to time measure on an object that is at rest.

Is this correct?

More generally than that. Time slows down on an object in motion relative to another. Generally the effect is only noticeable at near-light speed, but you can see it using an atomic clock and flying around the world. Comparing the clock to one that stayed on the ground during the flight, you will find they have measured a different elapsed time period.

[freenrg 0]

More generally than that. Time slows down on an object in motion relative to another. Generally the effect is only noticeable at near-light speed, but you can see it using an atomic clock and flying around the world. Comparing the clock to one that stayed on the ground during the flight, you will find they have measured a different elapsed time period.

This is where I feel confused.

I had read about the atomic clocks and the difference in measured time.

You wrote that there is no absolute frame of reference. Then, as far as the plane is concerned, the earth could be the object moving, while the plane is at rest. Why does the clock on the plane slow down and not the clock on the earth?

What is special about the earth?
If there is no absolute frame of reference, why are the clocks acting as if the earth is at rest and the planes are moving?

[freenrg 0]

rvalkass,

 

These equations describe the differences in time measured by the clocks on the planes and on earth, am I right?

 

where

 

So how do we calculate v?

 

example...

v of earth = 0

v of plane = 2,000 mph

 

how do we reach these values?

why is v of earth 0 and v of plane 2,000 mph and not the other way around?

[rvalkass 5]

These equations describe the differences in time measured by the clocks on the planes and on earth, am I right?

 

where

Yes. They're known as the Lorentz transforms and are used to change both time and position to account for relativistic effects.

 

So how do we calculate v?

 

example...

v of earth = 0

v of plane = 2,000 mph

 

how do we reach these values?

why is v of earth 0 and v of plane 2,000 mph and not the other way around?

If you did take a view of the Earth from a distance, you would see the plane was moving faster than the Earth. Therefore the plane is travelling at a speed v relative to the Earth.

[freenrg 0]

Yes. They're known as the Lorentz transforms and are used to change both time and position to account for relativistic effects.

 

 

 

If you did take a view of the Earth from a distance, you would see the plane was moving faster than the Earth. Therefore the plane is travelling at a speed v relative to the Earth.

So does this observer watching both the earth and the plane from a distance constitute an inertial frame of reference?

[rvalkass 5]

So does this observer watching both the earth and the plane from a distance constitute an inertial frame of reference?

Not necessarily. An inertial reference frame is one where the observer's speed is 0 and every physical law obeys its standard form. In the example of the Earth and the plane, by standing on the Earth as an observer, you make it your inertial reference frame and define its speed as 0 (which makes sense, the Earth's speed relative to the Earth would be 0). This then means the plane is moving relative to you, and hence the value of v in the equation.

[freenrg 0]

Not necessarily. An inertial reference frame is one where the observer's speed is 0 and every physical law obeys its standard form. In the example of the Earth and the plane, by standing on the Earth as an observer, you make it your inertial reference frame and define its speed as 0 (which makes sense, the Earth's speed relative to the Earth would be 0). This then means the plane is moving relative to you, and hence the value of v in the equation.

OK.
So, if I am standing in the plane looking at the plane's clock, then for me (and for that clock) the plane is an inertial frame of reference and the earth is moving at speed v, in the opposite direction?

[freenrg 0]

wait a minute...I was swimming this morning and thinking about this (yes, I am that weird).The apparent lack of symmetry between the earth and the plane kept me puzzled. Why does the plane clock slow down with respect to the one on earth and not the other way around?You (rvalkass) mentioned that a distant observer could tell which one was moving and which one was not. But how do the clocks "know"?Then I thought...The clocks have to be synchronized at some point. ... So, the clocks are synchronized when the plane is still on the earth, right?. Then the plane takes off and moves around, and finally lands on the earth again and we check the clocks and find the difference.Does this synchronization and the fact that is takes place on the earth break the symmetry? I think it may, but I am not sure why.Does it?Why?

Edited May 13, 2009 by freenrg (see edit history)

[rvalkass 5]

Then I thought...The clocks have to be synchronized at some point. ... So, the clocks are synchronized when the plane is still on the earth, right?. Then the plane takes off and moves around, and finally lands on the earth again and we check the clocks and find the difference.
Does this synchronization and the fact that is takes place on the earth break the symmetry?
I think it may, but I am not sure why.

Does it?
Why?

You are correct that the fact the synchronisation occurs on Earth is an issue. What you have stumbled across in a round about way is known as the "Twins Paradox". You have also managed to reach the solution to it The paradox is normally explained with spaceshuttles as the effect is more obvious, but planes work just as well.

Consider two twins: Laura and Emily. Emily stays on Earth while her twin, Laura, is put in the space shuttle and fired off into the distant reaches of space. Because of the speed of the shuttle, Emily observes time as proceeding more slowly in the space shuttle than on Earth. So, when Laura returns she will be younger than Emily.

However, to Laura the space shuttle is an inertial reference frame. As the Earth moves relative to her, she thinks Emily is ageing slower than her. When she returns, Laura thinks Emily is younger. So, who's right?

Laura's space shuttle has had to accelerate relative to the Earth to take off. Then again as it turns round to return. However, Emily has remained fairly inertial throughout the entire process. Laura's frame of reference (the space ship) therefore cannot be considered inertial, and her calculations are incorrect. Emily's are right, and Laura is the younger of the twins when she gets back.

The same can be said of planes. As they need to accelerate away from the Earth, and then back towards it, they can't be considered inertial.