Since space and time are relative shouldn't matter and energy be also?

• Gregory.gags
In summary, the speed of light is constant regardless of the observer's frame of reference, but the speed of matter is relative. This can be seen in the example of a bullet being fired from a moving car, where the velocity of the bullet is the sum of the car's velocity and the bullet's velocity with respect to the shooter. From a Newtonian standpoint, you simply add the velocities, but in special relativity, it is more complex. Energy is also relative, with the kinetic energy of a bullet being 0 in its own frame of reference but much larger in the frame of the person who shot it. The rest mass of a particle does not change with reference frame, but the relativistic mass does change. The energy-m
Gregory.gags
Its known that the speed of light is constant...(if you emit a light Eastward while your physically traveling East c will still be the same as if you were still) but also, through an experiment i am imagining, the speed of matter should be relative as well...(if your traveling Eastward and you shoot a bullet to the East it will travel at the same speed as a shooter facing East standing still would). But HOW can matter have the same properties as energy is one has mass and the other not? could matter=energy/frequency?

Gregory.gags said:
(if your traveling Eastward and you shoot a bullet to the East it will travel at the same speed as a shooter facing East standing still would).

This is not correct. If a person fires a bullet while moving with respect to some stationary observer, the bullet will travel faster with respect to the stationary observer than it would have if the shooter was standing still.

If you replace 'bullet' with 'photon', then you'ld be correct.

elfmotat said:
This is not correct. If a person fires a bullet while moving with respect to some stationary observer, the bullet will travel faster with respect to the stationary observer than it would have if the shooter was standing still.

but what would the mathematics behind this be? would the kinetic force of the car be ADDED to the velocity of the bullet?
also
if the bullet is already in motion, as per the moving car, wouldn't the thrust of the gunpowder need to be greater to overcome the *inertia?* of the bullet?

ps I'm probably not making a lot of sense since I only know a little bit about a lot of stuff, but please bear with me :)

Gregory.gags said:
but what would the mathematics behind this be? would the kinetic force of the car be ADDED to the velocity of the bullet?

From a Newtonian standpoint, you just add the velocity of car to that of the bullet with respect to the shooter in the car. If a car is moving at velocity vcar and a passenger fires a bullet that travels at velocity u, then the velocity of the bullet with respect to a stationary observer is just:

vbullet = vcar + u

In special relativity, "adding" velocities isn't quite this simple, but it's the same general principle.

Gregory.gags said:
also
if the bullet is already in motion, as per the moving car, wouldn't the thrust of the gunpowder need to be greater to overcome the *inertia?* of the bullet?

Nope, for the same reason you don't fly backwards at over 300 mph when you stand up in an airplane.

Responding to the original post: yes, energy is relative. The kinetic energy of a bullet is 0 in the frame of reference of the bullet. It's much larger in the frame of a person who has shot it. As far as matter, that depends on how you define matter. The rest mass doesn't change with reference frame, but the relativistic mass does change.

What doesn't change is the length of the energy-momentum 4-vector. This is the rest mass for an atomic particle, but includes internal energies for a composite system.

1. What does it mean for space and time to be relative?

Relativity, in the context of space and time, refers to Albert Einstein's theory of special relativity which states that the laws of physics are the same for all observers in uniform motion, regardless of their relative velocities. This means that measurements of space and time can vary depending on the observer's frame of reference.

2. How does relativity affect matter and energy?

Einstein's theory of relativity also includes the famous equation E=mc², which shows the relationship between matter and energy. It states that matter can be converted into energy and vice versa, and the amount of energy produced is equal to the mass of the object multiplied by the speed of light squared.

3. Why is it important to consider relativity in scientific studies?

Relativity is important in scientific studies because it helps us understand the fundamental laws of the universe and how they apply to different frames of reference. It also allows us to make precise measurements and predictions in fields such as astrophysics and engineering.

4. Can we observe the effects of relativity in our daily lives?

Yes, we can observe the effects of relativity in our daily lives, although they may be very small. For example, GPS systems need to take into account the effects of relativity in order to provide accurate location data due to the difference in the passage of time for satellites in orbit and observers on Earth.

5. Are there any limitations to the theory of relativity?

While the theory of relativity has been extensively tested and confirmed, it does have its limitations. For example, it does not fully explain the behavior of very small particles in quantum mechanics. Scientists continue to study and refine the theory in order to better understand the universe and its workings.

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