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Take these two scenarios :

  1. If you might have seen Justice League, in the fight scene between Superman and other heroes take place, Flash moves at an incredibly fast speed. Since it is impossible to see what he's doing at such speed, the camera is slowed down to show us his normal speed while the background is slowed much more. In this case, when Flash moves much faster, the time in the background moves slower relative to him.

  2. In the stunning movie Interstellar by Christopher Nolan, the protagonist and his team revolve around a black hole implying that they are moving much much faster than the people on Earth. When they land on a planet in the black hole's orbit, it has been shown that 1 hour on the planet equals 7 years on Earth.

Now imagine you as the Flash. Time outside goes slower compared to you. When you imagine yourself as the protagonist, time outside(that is in Earth) goes faster. Can someone explain what is happening here?

Srivatsav
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2 Answers2

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The films are showing two different effects.

The first is simply the equivalent of slow-motion photography. If you want to see something that happens quickly, you simply reduce the playback speed, which reduces the speed of everything captured on the film. If you want to see a bullet speeding at 1,000 metres per second, and you slow the playback speed by 10,000, then the bullet will now seem to be moving at 10cm per second, while events in the background will seem to be frozen. In Justice League, the Flash is moving like a speeding bullet- the film shows the passage of time slowed down, so the Flash's movements can be seen, while the background looks almost frozen.

While the first effect is simply slow-motion, in which all events (the Flash's movements and the background) are slowed down by the same amount, the second effect is gravitational time dilation, which is a separate phenomenon altogether, in which time for the protagonist appears to pass at a slower rate from the perspective of the people on Earth.

The difference between the two scenarios might seem clearer if you imagine all the characters to be wearing watches. In the first scenario, the watch of the Flash and of all the people in the background will be ticking at the same (slow) rate. In the second scenario, the watches of the protagonist and crew will appear to be running slow compared with watches worn by people on Earth.

Marco Ocram
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I can answer the first but not the second example. The Flash's situation is actually more about the different individual perceptions of time, rather than real time dilation physics. This comes down more to biology, the speed of firing neurons in our brains, how consciousness is formed out of all this, and so forth... (Whether it's physically possible to move and react as fast as he does is altogether another question...)

But let's suppose that what feels like 1 second to us actually feels like 10 seconds to the Flash. To the Flash, watching a normal YouTube video would feel like like watching the same video at a speed of 10%, with everything happening in painfully slow motion.

Is the perception of time universal for everybody, and all across different species? Does everyone sense "1 second" to be the same "SI-unit" length of "waiting", or do some people perceive this longer and shorter than others?

And what about animals? For short-lived animals like the mayfly, with a lifespan of only 24 hours, do they perceive 1 second the same way we do? Are there living things (eg. plants) with no perceptions of time, and what is it like to live as one such organism? Is consciousness related to the ability to perceive time, ie. make if -> then decisions in our minds?