Earth's Velocity: Lorentz Factor & Reference Frame

In summary, according to relativity, the velocity of Earth relative to that of the center of the universe or to a reference frame that gives maximum speed is zero.
  • #1
S. Moger
53
2
What's the velocity of Earth relative to that of the centre of the universe or to a reference frame that gives maximum speed.

What about the Lorentz factor? V signifies relative speed there?
 
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  • #2
Just consider the surface of a balloon, now where is the center? It could be argued that any, and every point is the center. Likewise for the universe, so it can be argued that our velocity wrt to the center of the universe is zero.

The v in the Lorentz transform is the velocity of the observed wrt to the observer.
 
  • #3
How do we know it's comparable with the surface of a balloon?

I'm curious about at what fraction of the speed of light Earth is moving. We have this self rotation, then orbit around the sun, galaxy and the galaxy around the local group. But after that? Does the local group move too?

And how do we know that we are moving and not someone who has 0 velocity compared to our reference frame? Won't time go faster for the one that moves? But how can we determine who's moving and who's not?
 
  • #4
S. Moger said:
But how can we determine who's moving and who's not?
Well, we can't. That's the whole point of relativity.
 
  • #5
There is no "center of the universe" to refer velocities to. There is no frame that results in a "maximum speed," but you can choose a frame in which the speed of the Earth is as close to c as you like.

As A.T. says, you can't determine who is moving and who is not. That's why it's called "Relativity."
 
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  • #6
The best you can ask is what is the velocity of the Earth relative to the reference frame where cosmic relic radiation is (almost) isotropic.
 
  • #7
If you have these movements away from a centre, can't we set that centre as a reference frame? Aren't the galaxies moving away from the location of the big bang? And if we interpolate we find that place?

What about space travellers whose local time passes slower than that of earth? Why isn't it the other way around? Is it just because they accelerated? But say we all forgot that, how do we then know whose time is going faster etc? Or let's say that it really was everything apart from the space travellers that accelerated. In that case why is time going slower for the people remaining on earth?
 
  • #8
There is no movement away from the centre because there is no centre =) there was an "explosion" of space itself, not like a big bomb. Imagine like we are on the surface of a balloon that is being inflated. Where is the centre of the surface? it is not in any point on the surface.
 
  • #9
S. Moger said:
If you have these movements away from a centre, can't we set that centre as a reference frame? Aren't the galaxies moving away from the location of the big bang? And if we interpolate we find that place?

No, you are suffering from a misconception. The galaxies are certainly NOT moving away from a center. There is no center, and no void into which they stream. The universe is uniformly filled with them everywhere and the distances between them are increasing.

What about space travellers whose local time passes slower than that of earth? Why isn't it the other way around?

Also a misconception. There is no absolute sense in which the space traveler's time is slower than that of the Earth. It is observed to be so from the Earth, but there are frames that disagree. In particular, the space traveler observes his clock to run normally and the Earth's to run slow. So it is also the other way around.

If the space traveler turns around, then when he returns to Earth, everyone agrees he is younger. In the Earth's reference frame, this is because the traveler's clock has run slow the entire time. To the space traveler, it is because when he turns around he switches inertial frames and in doing so shifts his slice of spacetime that he observes to be simultaneous. The solution to every "paradox" is that you have ignored relativity of simultaneity.
 

What is the Lorentz factor?

The Lorentz factor is a mathematical term used in physics to describe the relationship between an object's velocity and its mass, as it approaches the speed of light. It is denoted by the Greek letter "gamma" (γ) and is calculated by dividing the object's speed by the speed of light.

How does the Lorentz factor affect an object's mass?

The Lorentz factor states that as an object's velocity increases, its mass also increases. This means that the mass of an object moving at high speeds is larger than its rest mass (the mass it has when at rest). At the speed of light, the Lorentz factor becomes infinite, meaning that the object's mass would also become infinite.

What is the reference frame in relation to Earth's velocity?

The reference frame is the physical point of view from which an observer measures the velocity of an object. In terms of Earth's velocity, the reference frame is typically taken as the surface of the Earth, or the center of the Earth, depending on the specific situation being studied.

How does Earth's velocity affect time dilation?

According to the theory of relativity, time dilation occurs as an object's velocity approaches the speed of light. This means that time passes slower for an object in motion compared to an object at rest. As Earth moves through space, it experiences a very small amount of time dilation, but it is not noticeable to humans.

Does Earth's velocity impact its orbit around the sun?

Yes, Earth's velocity does impact its orbit around the sun. The faster Earth moves in its orbit, the longer its orbit becomes, and the slower it moves, the shorter its orbit becomes. This is due to the conservation of angular momentum, which states that the product of an object's mass, velocity, and distance from the center of rotation must remain constant. Therefore, as Earth's velocity changes, its distance from the sun must also change to maintain this balance.

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