Questions on Spacecraft, Light Mass, Relativity & Quantum Theory

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Discussion Overview

The discussion revolves around various questions related to spacecraft, mass, relativity, and quantum theory. Participants explore concepts such as the relationship between mass and force in space, the implications of infinite energy on mass and time, the nature of light and its energy, and the compatibility of Newtonian and Einsteinian physics. The scope includes theoretical inquiries, conceptual clarifications, and some mathematical reasoning.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants assert that mass does matter in space, requiring more force to accelerate a heavier spacecraft.
  • There is a hypothesis that if a mass is accelerated with infinite energy, it could gain infinite mass and experience time differently.
  • Questions arise about how light, despite having energy, is proven to have no mass, with some suggesting that combining equations incorrectly can lead to confusion.
  • Concerns are raised about the appropriateness of equating Newtonian mathematics with Einstein's equations, with a general consensus that they are not directly comparable.
  • Participants discuss whether a mass in vacuum experiences any resistance, with some clarifying that it does not feel resistance in the traditional sense.
  • The phenomenon of redshift is debated, with some stating that it is related to the speed of the source rather than the distance traveled.
  • Questions are posed about the implications of relative velocity in relation to the speed of light, with some participants affirming that relative velocities cannot exceed the speed of light.
  • There is a discussion about whether light can travel below the speed of light in a vacuum, with participants emphasizing that light travels at a constant speed.
  • Participants express curiosity about the theoretical backing for mass gain as an object approaches the speed of light, with some indicating that the equations themselves provide the theory.
  • One participant suggests consulting resources on the definitions of mass in relativity to clarify confusions.

Areas of Agreement / Disagreement

Participants express a range of views, with some areas of agreement on basic principles, but many questions remain unresolved, particularly regarding the nuances of mass, energy, and the implications of relativity.

Contextual Notes

Some discussions highlight the importance of distinguishing between weight and mass, as well as the complexities of relativistic mass versus invariant mass. There are also unresolved assumptions regarding the nature of energy loss over distances and the implications of relativistic effects.

Who May Find This Useful

This discussion may be of interest to those studying physics, particularly in the fields of relativity and quantum theory, as well as individuals seeking to clarify foundational concepts in these areas.

The_Thinker
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Hey...
Its been a looong time since i posted here... :rolleyes: but there have been a few nagging questions in mind that i needed clarified. And i would appreciate it if someone were nice enough to answer them... :smile:
Anyway... here they are a few of them are very basic though..

1)Consider a spacecraft in space or vaccum, would its mass matter there? as in would you require more force to accelerate a heavier rocket than one with lesser mass?

2)If a mass is accelrated (hypothetically) with infinite energy... does it gain infinite mass? and does its time stop? relative to the rest of us...( of course we won't be there cause it the mass will be infinite and there won't be any space for us... but anyway... :rolleyes: )

3)If light has no mass but it has energy given by hf, taking energy and mass equilence, how did they prove that light had no mass?

4)Is it wrong to equate Newtonian mathematics with einstiens equations?

5)Does a mass in vacuum or free space truly feel no resitance whatsoever?

6)Does the energy of light reduce when it travels through long distances? If not... then why does red shift occur?

7)No mass is allowed to travel beyond the speed of light... But does that apply to its relative velocity as well? as in is an objects relative velocity not allowed to exceed the speed of light? (i know the answer for this is no... its relative velocity doesn't matter here... but i just wanted to make sure...)

8)Light travels at a constant velocity... but does it travel, can! it travel below the constant speed of light (in vaccum) i mean. I am not talking about the speeds in other mediums...

9)Why is it that when a mass is accelarated towards the speed of light that it gains mass? i mean should it not lose mass so that it can travel at the speed of light massless... i know its because it follows the equations... but what is the theory backing it up?

10)Could anyone let me know of some good books to read so that i can improve my knowledge in the fields of quantum theory, general and special relativity and string theory? I want books that go deep but not deep enough that a non physicst cannot understand.

Thats it... if you reply to this... thanks a lot... i really appreciate it... :smile: and thank you for your patience... :approve:
 
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The_Thinker said:
1)Consider a spacecraft in space or vaccum, would its mass matter there? as in would you require more force to accelerate a heavier rocket than one with lesser mass?
F=ma. Don't confuse weight and mass.
2)If a mass is accelrated (hypothetically) with infinite energy... does it gain infinite mass? and does its time stop? relative to the rest of us...( of course we won't be there cause it the mass will be infinite and there won't be any space for us... but anyway... :rolleyes: )
Basically yes - and don't roll your eyes: Don't confuse mass and volume.
3)If light has no mass but it has energy given by hf, taking energy and mass equilence, how did they prove that light had no mass?
Don't combine equations that don't match (just because the units match, doesn't mean the equations can be combined).
4)Is it wrong to equate Newtonian mathematics with einstiens equations?
That's not very specific, but generally yes.
5)Does a mass in vacuum or free space truly feel no resitance whatsoever?
No. Again, don't confuse weight and mass. f=ma
6)Does the energy of light reduce when it travels through long distances? If not... then why does red shift occur?
Yes, but its not the distance but the speed of the source.
7)No mass is allowed to travel beyond the speed of light... But does that apply to its relative velocity as well? as in is an objects relative velocity not allowed to exceed the speed of light? (i know the answer for this is no... its relative velocity doesn't matter here... but i just wanted to make sure...)
Since all velocity is relative, yes.
8)Light travels at a constant velocity... but does it travel, can! it travel below the constant speed of light (in vaccum) i mean. I am not talking about the speeds in other mediums...
Light travels at constant speed, not velocity.
9)Why is it that when a mass is accelarated towards the speed of light that it gains mass? i mean should it not lose mass so that it can travel at the speed of light massless... i know its because it follows the equations... but what is the theory backing it up?
The equations are the theory. Others can give more detailed explanations of how it works, but "why" tends to head toward philosophy.
 
Why don't you read the sci.physics.faq about the two common (and different!) defintions of mass in common use in relativity

http://www.math.ucr.edu/home/baez/physics/Relativity/SR/mass.html

and trim your questions down to just the single most important one (or perhaps a couple of closely related questions).

As is, with so many questions (and so many assumptions on your part), I'm not sure where to start.
 
k... cool will do... thanks for the prompt replies though... :)
 
k got it... most of the confusions gone... but...
russ_watters said:
No. Again, don't confuse weight and mass. f=ma
k... in general do objects feel any sort of resistance when traveling through vacuum irrespective of their mass... as in... is there any data that indicates that objects do tend to lose some energy when traveling long distances?

russ_watters said:
Yes, but its not the distance but the speed of the source.

k got it... so what you mean is that redshift occurs because of the speed of the source and has nothing to do with its distance?

russ_watters said:
Since all velocity is relative, yes.
k cool... so its relative velocity also must not exceed that of c, is that right? then what would happen if one photon comes in one direction and the another comes opposite to it... what would be the relative velocity that these two would see then? or is it erronous to compare light as an observer?

article about relativistic mass pointed to by pervect said:
"Ouch! The concept of `relativistic mass' is subject to misunderstanding. That's why we don't use it. First, it applies the name mass--belonging to the magnitude of a four-vector--to a very different concept, the time component of a four-vector. Second, it makes increase of energy of an object with velocity or momentum appear to be connected with some change in internal structure of the object. In reality, the increase of energy with velocity originates not in the object but in the geometric properties of space-time itself."
Does this mean that with added energy to the object the space time around the object curves more than if it was at rest?

and also does relativistic mass... add to its weight?

thx for your patience guys... :smile:
 
The_Thinker said:
then what would happen if one photon comes in one direction and the another comes opposite to it... what would be the relative velocity that these two would see then

This is one thing that is quite easy to understand about relativity imo. "The speed of light appears constant to every inertial observer" is a postulate of relativity. This implies that for anyone moving without accelerations (e,g, a particle of light) that any particle of light appears to move with a speed c. Even if the observer is a photon moving at c and another photon is hurtling towards it at c from the opposite direction.

If you want to know how to deal with the more general case of objects moving at any given velocity, you should look up the addition of velocities.
 

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