- #1
Nantes
- 54
- 5
- TL;DR Summary
- A film that blends romance and physics in a very interesting way poses a rather weird relativistic consideration.
Background: There is a very interesting Catalunyan film on Netflix called "Las Leyes de la Termodinámica" (The Laws of Thermodynamics) which is perhaps the world's first hybrid of a physics documentary and a romance film. The main character is a physics professor who falls in love and attempts to explain everything that happens in his love life through the optics of the laws of physics. It is smattered with commentary from actual physicists as well. Very interesting movie that everyone here should watch!
Discussion: There is a sequence beginning at 54:30 where the characters are in a Gay Pride parade and one of them is dancing on top of a bus. The bus stops, but suddenly has to leave again, which makes the guy lose balance and fall. The film discusses the "point of view paradox" of how two observers see the same event differently: people on top of the bus see him falling in a straight line, whilst people on the ground see him falling in a parabola, since the bus is moving. Because the parabola is necessarily longer than the straight line, the people on the ground see him "falling faster" than the people on the bus.
Then the film states: "The two observers have to see exactly the same event, because the speed of light is constant. And this is exactly what Einstein realized. Einstein proved that not only space contracts and stretches depending on the position of the observer, but time itself is also relative".
The film's statement that the guy is "falling faster" for the people on the ground is a bit confusing to me. He's only observed as having a horizontal velocity component, which is not perceived by people on the bus, but the vertical component of the velocity in both situations is the same, no? Shouldn't the vertical component be the only one that counts in this scenario?
Or maybe the film is alluding to the fact that light would take different amounts of time to reach each observer's eyes because, for a given person on the ground, he's getting farther or closer away with each second. But the rays of light that reach both observers are not the same, so there is no reason in my mind why they would have to match up. Their emissions are separate occurences to me, so it is fine that light takes a little longer to reach one than the other.
Background on me: as you can tell, I'm not a physicist, I just have considerable interest in it and in science in general, and probably more basic knowledge on relativity on than your average joe.
Discussion: There is a sequence beginning at 54:30 where the characters are in a Gay Pride parade and one of them is dancing on top of a bus. The bus stops, but suddenly has to leave again, which makes the guy lose balance and fall. The film discusses the "point of view paradox" of how two observers see the same event differently: people on top of the bus see him falling in a straight line, whilst people on the ground see him falling in a parabola, since the bus is moving. Because the parabola is necessarily longer than the straight line, the people on the ground see him "falling faster" than the people on the bus.
Then the film states: "The two observers have to see exactly the same event, because the speed of light is constant. And this is exactly what Einstein realized. Einstein proved that not only space contracts and stretches depending on the position of the observer, but time itself is also relative".
The film's statement that the guy is "falling faster" for the people on the ground is a bit confusing to me. He's only observed as having a horizontal velocity component, which is not perceived by people on the bus, but the vertical component of the velocity in both situations is the same, no? Shouldn't the vertical component be the only one that counts in this scenario?
Or maybe the film is alluding to the fact that light would take different amounts of time to reach each observer's eyes because, for a given person on the ground, he's getting farther or closer away with each second. But the rays of light that reach both observers are not the same, so there is no reason in my mind why they would have to match up. Their emissions are separate occurences to me, so it is fine that light takes a little longer to reach one than the other.
Background on me: as you can tell, I'm not a physicist, I just have considerable interest in it and in science in general, and probably more basic knowledge on relativity on than your average joe.