-
Looking for HSC notes and resources? Check out our Notes & Resources page
relative? meaning? (1 Viewer)
- Thread starter cd285
- Start date
darkchild69
Nanotechnologist
Think about reference frames.
If the speed of light is constant in all reference frames, then space and time must change depending upon the velocity of the frame of reference.
Basically talking about time dilation and length contraction
If space and time change depending on the velocity of the frame of reference, then they are relative.
Think about this:
Frame of reference A: Person on a train travelling at 0.5c, passing a platform
Frame of reference B: Stationary person on the platform
At the moment Person A passes Person B, he shines a light. Both people see light travelling at c. But, how can this be possible? Because Newtonian physics was of the opinion that the velocities would add together and person B would see the light travelling at 1.5c (speed of light + 0.5c (velocity of the train))
If the speed of light is constant in all frames of reference, then space and time themselves must change in order to accomodate this!
Sorry, i think thats about as lay as I can get
If the speed of light is constant in all reference frames, then space and time must change depending upon the velocity of the frame of reference.
Basically talking about time dilation and length contraction
If space and time change depending on the velocity of the frame of reference, then they are relative.
Think about this:
Frame of reference A: Person on a train travelling at 0.5c, passing a platform
Frame of reference B: Stationary person on the platform
At the moment Person A passes Person B, he shines a light. Both people see light travelling at c. But, how can this be possible? Because Newtonian physics was of the opinion that the velocities would add together and person B would see the light travelling at 1.5c (speed of light + 0.5c (velocity of the train))
If the speed of light is constant in all frames of reference, then space and time themselves must change in order to accomodate this!
Sorry, i think thats about as lay as I can get
so relative means they have a direct relationship with each other? like i get the concept of reference frames and that since c is constant, therfore distance (space) and time must change and hence it means they're relative? :S is that right??
darkchild69
Nanotechnologist
Quite simply put, remember from the preliminary course:
Velocity = distance/time
yeah?
So, think about this.
If two observers, travelling at different speeds both observe the speed of a light beam to be the same, then the length and time interval which is measured by both observers must be different in different reference frames.
So basically, if 'c' is constant, then space and time are relative, and vary depending on the frame of reference.
Going a little further, seeing as space and time are not absolute, relativity uses the concept of a space-time continuum within which any event can be characterised by three spatial dimensions and the 4th dimension (time). These 4 dimensions are what define the position of the object within its frame of reference.
OK, let me see if I can get very layman and not use the technical words.
Relative = in comparison to
Imagine you are at the airport with a friend, John, where they have those funky travellators for people who don't want to walk very far.
You and John stand next to each other. Relative to each other, you are not moving. Relative to the rubbish bin next to you, you are not moving either.
You and John get on a travellator together and stand still. Relative to each other, you are not moving. Relative to the bin you are now moving away from it at travellator speed.
You have some time to kill before your plane goes, so you jump on a travellator going North and John jumps on the travellator going South. Relative to the bin you are both moving at travellator speed. Relative to each other, however, you are travelling at twice travellator speed.
OK, now going to your point. If we want to assume that the speed of light is constant at c, then in the last example, where you and John are travelling at twice the speed of the travellator, relative to each other, then we have to explain it another way.
To the rubbish bin you are travelling at travellator speed, c, and to each other you must be travelling at travellelator speed, c. SO what must be different when you look at John and he looks at you? It must be the other stuff, length and time: v= d/t
That pretty much says what everyone else has said, so I hope it has helped.
Relative = in comparison to
Imagine you are at the airport with a friend, John, where they have those funky travellators for people who don't want to walk very far.
You and John stand next to each other. Relative to each other, you are not moving. Relative to the rubbish bin next to you, you are not moving either.
You and John get on a travellator together and stand still. Relative to each other, you are not moving. Relative to the bin you are now moving away from it at travellator speed.
You have some time to kill before your plane goes, so you jump on a travellator going North and John jumps on the travellator going South. Relative to the bin you are both moving at travellator speed. Relative to each other, however, you are travelling at twice travellator speed.
OK, now going to your point. If we want to assume that the speed of light is constant at c, then in the last example, where you and John are travelling at twice the speed of the travellator, relative to each other, then we have to explain it another way.
To the rubbish bin you are travelling at travellator speed, c, and to each other you must be travelling at travellelator speed, c. SO what must be different when you look at John and he looks at you? It must be the other stuff, length and time: v= d/t
That pretty much says what everyone else has said, so I hope it has helped.