Mass/Energy relationship of Particles Traveling Light Speed

[Steve Hulowski]

Relativity has always been a stumbling block for me. No matter how much I read about and try to understand it, I find myself with more questions than when I started. Here are a few that have been picking my brain recently:

 

It's my understanding that as any mass approaches the speed of light, its mass approaches infinity--or do you just say that its energy approaches infinity? I get confused with the mass energy relationship when something is accelerated to near light speeds. If mass and/or energy approach infinity with increasing velocity then shouldn't subatomic particles, such as neutrinos, possess infinite mass? Do they travel just shy of the speed of light? If an object increases in mass as it is accelerated faster, what happens to its gravitational field strength? You'd think any mass traveling at light speed would be a moving black hole.

[Janus]

Relativity has always been a stumbling block for me. No matter how much I read about and try to understand it, I find myself with more questions than when I started. Here are a few that have been picking my brain recently:

 

It's my understanding that as any mass approaches the speed of light, its mass approaches infinity--or do you just say that its energy approaches infinity?

The energy increases towards infinity is generally how modern science describes it.

 

I get confused with the mass energy relationship when something is accelerated to near light speeds. If mass and/or energy approach infinity with increasing velocity then shouldn't subatomic particles, such as neutrinos, possess infinite mass?

They would have infinite energy only if they traveled at c itself. Anything less results in something less than infinite. Neutrinos have a very small rest mass so they can travel very close to the speed of light and still not seem very "massive". Other sub-atomic particle don't naturally have velocities that take them that close to the speed of light.

Do they travel just shy of the speed of light? If an object increases in mass as it is accelerated faster, what happens to its gravitational field strength? You'd think any mass traveling at light speed would be a moving black hole.

 

Remember, as far as the object itself is concerned, it is not moving with respect to itself and its mass does not increase. Thus it does not collapse inot a black hole in its own frame. If it doesn't collapse into a black hole in its own frame it does not do so in any other frame. So the answer is no, an fast moving object will not form a black hole.

[Steve Hulowski]

Thanks for the reply.

 

So if I understood correctly, the reason these subatomic particles do not possess infinite energy and/or mass is because they are traveling just shy of the speed of light "c"?

 

This is the other thing about relativity that confuses me (reference frames and time dilation):

 

I'm told that if someone blasts away (I'll call this person Steve) from Earth and approaches light speed, that when Steve returns he'll have aged less than everyone else. Relative to observers on Earth, Steve's reference frame has slowed down. Now wouldn't Steve likewise see the Earth moving away from him at light speed? If velocity is only a "relative" phenomenon, why is it that one reference frame slows down but the other does not?

 

I like to use the bus analogy; whereas, when you're sitting on a bus when it starts to accelerate, you can get the brief feeling that it is the vehicle next to you that is moving and not yourself. Likewise, if two people, say Steve and John were in the abyss of space in their own separate space ships (ie. no visible light except from their ships to serve as reference to) and Steve sees John start to move away from him and eventually approach light speed, how can he know if it is himself moving or not? The only difference I could see is that only one of them will experience the acceleration. Is that what makes the difference as to who ages faster than the other--who experiences the acceleration?

 

If acceleration is taken out of the picture, and both Steve and John pass each other pass each other at some constant velocity, which one is aging faster? They can only measure their velocity relative to each other. They could then rondevu by sharing the amount at which they decelerate and then meet up for coffee in either ship. In this case, they would have both experienced the same acceleration. Which one has aged more?

 

Newton viewed the universe as though objects moved relative to some universal reference frame--as if there was a grid in the background that all objects (solar systems, galaxies ect) move relative to. Relativistic physics says otherwise, in that velocities are only relative to other objects. With the later being the accepted theory, why is time-dilation experienced differently for Steve and John without this "universal reference frame"?

[Janus]

Thanks for the reply.

 

So if I understood correctly, the reason these subatomic particles do not possess infinite energy and/or mass is because they are traveling just shy of the speed of light "c"?

 

This is the other thing about relativity that confuses me (reference frames and time dilation):

 

I'm told that if someone blasts away (I'll call this person Steve) from Earth and approaches light speed, that when Steve returns he'll have aged less than everyone else. Relative to observers on Earth, Steve's reference frame has slowed down. Now wouldn't Steve likewise see the Earth moving away from him at light speed? If velocity is only a "relative" phenomenon, why is it that one reference frame slows down but the other does not?

 

As long as Steve and the The Earth maintain a velocity with respect to each other, there is n absolute answer to that question. According to Steve, the Earth ages slower and according to the Earth, Steve ages slower. Who aged slower than who at different points of the trip is a question that does not have an definite answer. You can't say who accumulated more time until you bring them back together.

 

I like to use the bus analogy; whereas, when you're sitting on a bus when it starts to accelerate, you can get the brief feeling that it is the vehicle next to you that is moving and not yourself. Likewise, if two people, say Steve and John were in the abyss of space in their own separate space ships (ie. no visible light except from their ships to serve as reference to) and Steve sees John start to move away from him and eventually approach light speed, how can he know if it is himself moving or not? The only difference I could see is that only one of them will experience the acceleration. Is that what makes the difference as to who ages faster than the other--who experiences the acceleration?

 

The acceleration that causes their separation isn't a factor. The acceleration that one of them experiences when he turns around to rejoin the other does. Th eproblem is that you cannot analyze this problem by time dilation alone, you also have to consider length contraction and the Relativity of simultaneity.

For instance, say that John is traveling to a distant planet 7 ly away at 0.99c. According to Steve, the round trip will take ~14 yrs, during which time John will age 1/7 as fast and will return 2 yrs older. According to John, it is Stave and the distant planet that are moving at 0.99c wit respect to him. Thus the distance between the two undergoes length contraction and is only 1 ly. It only takes ~2 yrs by his clock to make a round trip of 2 ly at 0.99c, so that is how much he will age during the trip. This is why they both agree that the trip only takes 2 years of John's life.

As to why John expects Steve to have aged 14 yrs, you have to invoke the Relativity of simultaneity which causes Steve's clock to Jump ahead of John's clock when John does the turn around at the planet.

 

If acceleration is taken out of the picture, and both Steve and John pass each other pass each other at some constant velocity, which one is aging faster? They can only measure their velocity relative to each other. They could then rondevu by sharing the amount at which they decelerate and then meet up for coffee in either ship. In this case, they would have both experienced the same acceleration. Which one has aged more?

 

If they both traveled for the same time according to their own clocks and returned to the original point that they passed each other at the same time, neither will have aged more than the other.

 

Newton viewed the universe as though objects moved relative to some universal reference frame--as if there was a grid in the background that all objects (solar systems, galaxies ect) move relative to. Relativistic physics says otherwise, in that velocities are only relative to other objects. With the later being the accepted theory, why is time-dilation experienced differently for Steve and John without this "universal reference frame"?

 

Let's try an analogy. Imagine steve and John walking side by side on a featureless plane. John changes direction with changing his pace. After a while he decides to check up on Steve. He sees that Steve is no directly to the side of him but is slightly behind him, and getting further and further behind all the time. If John measures "progress" as distance traveled in the direction that he is walking then Steve is making progress at a slower rate than he is.

 

Steve notices the same about John. John is making less progress in the direction that Steve is walking than Steve is.

 

If we we think of the direction each man is walking as time, we have time dilation. Each man sees the other as progressing in time slower than he is (aging slower)

 

Now let's have John change direction again. This time he turns so that he walking back towards Steve's path.

 

As far as Steve is concerned this changes nothing as far as John's relative progress with respect to his own. He is still behind him and continue to fall further behind.

 

According to John though Steve's respective progress does change. as he turns towards Steve's path, Steve goes from being behind him to being in front of him. ( Imagine an object behind you and to your right. As you turn to your right, the object will move to being in front of you from your perspective.) Since John judges judges progress relative to the direction he is walking, Steve has gone from having made less progress to have having made more progress than John. The "direction of time" turns with John to match which way he is facing.

 

This is the equivalent of when John reaches the planet and then stops and accelerates back to Steve. Steve is seems to jump forward in time to now being older than John.

 

As john continues to walk back towards Steve's path he will note that he is "gaining" on Steve, but does not catch up to him before crossing Steve's path.

 

If John now turns to walk in the same direction as Steve when he crosses Steve's path, he will still find himself behind Steve, and Steve will agree. In terms of time, both Steve and John agree that John aged less when they are reunited.

[Genius13]

can any1 pls tell me what will this new ''faster than light nutrino'' do to the relativity theory