A specific reference frame that describes its coordinates in a manner that does not depend on time and is isotropic.
Questions tagged [inertial-frames]
2811 questions
161
votes
7 answers
Is temperature a Lorentz invariant in relativity?
If an observer starts moving at relativistic speeds will he observe the temperature of objects to change as compared to their rest temperatures?
Suppose the rest temperature measured is $T$ and the observer starts moving with speed $v$. What will be…
Sahil Chadha
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115
votes
12 answers
How can time dilation be symmetric?
Suppose we have two twins travelling away from each other, each twin moving at some speed $v$:
Twin $A$ observes twin $B$’s time to be dilated so his clock runs faster than twin $B$’s clock. But twin $B$ observes twin $A$’s time to be dilated so…
John Rennie
- 367,598
65
votes
15 answers
Why do we say that the Earth moves around the Sun?
In history we are taught that the Catholic Church was wrong, because the Sun does not move around the Earth, instead the Earth moves around the Sun.
But then in physics we learn that movement is relative, and it depends on the reference point that…
HappyDeveloper
- 1,397
64
votes
7 answers
If I run along the aisle of a bus traveling at (almost) the speed of light, can I travel faster than the speed of light?
Let's say I fire a bus through space at (almost) the speed of light in vacuum. If I'm inside the bus (sitting on the back seat) and I run up the aisle of the bus toward the front, does that mean I'm traveling faster than the speed of light?…
ed209
- 775
56
votes
8 answers
Proof that the Earth rotates?
What is the proof, without leaving the Earth, and involving only basic physics, that the earth rotates around its axis?
By basic physics I mean the physics that the early physicists must've used to deduce that it rotates, not relativity.
user8721
- 563
56
votes
3 answers
What is a Lorentz boost and how to calculate it?
I know very little about special relativity. I never learnt it properly, but every time I read someone saying
If you boost in the $x$-direction, you get such and such
my mind goes blank! I tried understanding it but always get stuck with articles…
user09876
- 877
50
votes
7 answers
Is the presence of a magnetic field frame-dependent?
I do not have a strong background in physics, so please refrain from using complex mathematics in any answers :)
I was on
this site, and I read:
When an electrical charge is moving or an electric current passes through a wire, a circular magnetic…
Cyclopropane
- 819
48
votes
2 answers
Why didn't Lorentz conclude that no object can go faster than light?
Based on Lorentz factor $\gamma = \frac{1}{\sqrt {1-\frac{v^2}{c^2}}}$ it is easy to see $v < c$ since otherwise $\gamma$ would be either undefined or a complex number, which is non-physical. Also, as far as I understand this equation was known…
Rob
- 429
48
votes
2 answers
Does the speed of light vary in non-inertial frames?
The speed of light is the same in all inertial frames.
Does it change from a non-inertial frame to another? Can it be zero?
If it is not constant in non-inertial frames, is it still bounded from above?
Revo
- 17,504
48
votes
5 answers
Why is Newton's first law necessary?
Newton's second law says $F=ma$.
Now if we put $F=0$ we get $a=0$ which is Newton's first law.
So why do we need Newton's first law ?
Before asking I did some searching and I got this: Newtons first law is necessary to define inertial reference…
Murtuza Vadharia
- 1,867
47
votes
10 answers
Without the Michelson-Morley experiment, is there any other reason to think speed of light is the universal speed limit?
If the Michelson-Morley experiment hadn't been conducted, are there any other reasons to think, from the experimental evidence available at that time, that Einstein could think of the Special Theory of Relativity?
Is there any other way to think why…
Vivekanand Mohapatra
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46
votes
7 answers
Does a photon in vacuum have a rest frame?
Quite a few of the questions given on this site mention a photon in vacuum having a rest frame such as it having a zero mass in its rest frame. I find this contradictory since photons must travel at the speed of light in all frames according to…
Physiks lover
- 3,178
46
votes
3 answers
History of interpretation of Newton's first law
Nowadays it seems to be popular among physics educators to present Newton's first law as a definition of inertial frames and/or a statement that such frames exist. This is clearly a modern overlay. Here is Newton's original statement of the law…
user4552
45
votes
12 answers
Is Mach's Principle Wrong?
This question was prompted by another question about a paper by Woodward (not mine). IMO Mach's principle
is very problematic (?wrong) thinking. Mach was obviously influenced by Leibniz. Empty space solutions in GR would result in a Minkowski metric…
Gordon
- 4,413
43
votes
10 answers
How does a spinning object "know" that it is spinning?
I am constructing a thought experiment about a spinning object that is floating in intergalactic space. I assume that this object is about the size of a planet so that it will have enough gravity so that a Foucault pendulum will work, although I'm…
user1928764
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