Ask Lemmy

Uhh, relativity, fun. This gets a lot more mind boggling, imagine 3 people, A and B are in a train and C is an observer outside. From C point of view, B will pass him first, then A. This train is going at 50% the speed of light and it's very long, A and B are 1 second light apart, i.e the distance that light takes 1 second to travel.

If A shines a flashlight B will see it 1 second later. However from C point of view since the light was shone the train moved forward 0.5 light seconds. So the light has to travel 1.5 light seconds distance, and it does so in exactly 1.5 seconds. So the observers disagree on the distance the light travel, but also disagree on the time it took, but they agree on the speed of light.

This makes things weird, because both A and B say that 1 second passed, but C says that 1.5 seconds passed. This means that people moving faster experience time slower. Which means that if you take two twins, put one on a fast moving ship, e.g. 80% speed of light, by the time he comes back only a few minutes would have passed for him, but years would pass for the other.

The back of my brain is fizzing.

I had the Relativity conversation with my 16 year old this past weekend, as he is taking AP Physics.

Yeah, he couldn't wrap his mind around it. Honestly, I can't say I understand it very well. I get that C (speed of light) is C in all reference frames. What I do not understand is for a spaceship traveling at C, the forces being transmitted between the atoms from stern to bow are unable to catch up to the next forward atoms. Hence time dilation, at least for those forces being transmitted "forward" in the ship's reference frame.

However, what happens to those forces being transmitted bow to stern or "backward" in the ship's reference frame? Would those forces be "dead stopped" in an external reference frame? Yet travel at C from bow to stern in the ship's reference frame? What does that mean for the ship if those forces are only being transmitted one way?

Or, as I very much suspect, do I just not have a clue as to how it really works. I always thought that "time dilation" was simply the inability of forces being transmitted from atom to atom. As those forces are limited to C and they are attempting to catch up to another atom also traveling at C. With that said, those forces are transmitted in multiple directions, not just the vector the ship is on.

Ok, another one of my very few brain cells just committed suicide and I'm not drinking anything, so I'll stop now.

If you’re on a truck traveling at 60mph, and throw a ball forward at 60mph, that ball is moving at 120mph.

Technically it would be moving at something like 119.99999999km/h and that discrepancy slowly increases the closer you get to the speed of light

Is that fucking garbage still going ahead!??

Sheeeeit

Same with people who complain qbout facebook and use facebook.

I think I've read before that our eyes are most sensitive to the color green out of any other color, something about it that wavelength of light is absorbed more readily by the cones in our eyes. Being exposed to it daily and maybe having their survival dependent on it probably helps them develop that ability.

Do you have a source? There is a common myth that innuits have 100+ words for snow, which is stretch beyond any reasonable sense, I'm afraid this might be similar.

Yeah, but it's from Apple! /s

To boldly go... where few men have gone before.

What happened exactly today that boggled your mind?

Where in the world did you get that number and what were the specific parameters?

Because "2.3 billion people — 29.6% of the global population — don’t have adequate access to food" and "9 million people die from hunger-related causes every year"

Perhaps. But infinite universes is still just a theory. So why let such a astronomical 'what if,' get you down?

Yep, if there's an infinite number of parallel universes then there's an infinite number where nothing is different. Maybe the only difference between the universes was the position of a mote of dust on an uninhabited planet in a galaxy on the other side of the universe.

If the many worlds interpretation is correct, that would mean that there's not really an infinite number of discrete realities, but more of a continuum. So there are infinite other realities in the same way that there are infinite points on a line, but this exact reality is still unique.

That's not right at all by my thinking.

Infinite multiverse means infinite exact same universe as ours, yes. But it also means there are also infinite different universes. But you can use comparisons to see that there would likely be more universes that are different than ours because of small permutations in history causing larger effects in the future. So I like to think there are both many exact universes, and many very different universes.

Let me see if I can try to explain this.

First off, light isn't just the fastest thing we know of, it is physically impossible to go faster than light according to the laws of physics as we understand it. This is because the speed of light is actually tied to the way spacetime works.

Imagine you are standing and you throw a ball. The ball travels at whatever speed you throw it, let's say 5 mph.

Now, let's put you on a train traveling at 20 mph and do the same thing. If you throw the same direction the train is traveling, your 5 mph adds to the train's 20 and the ball goes at 25 mph according to someone standing next to the track. Throw it the other way and they see it travel at 15 mph. To you, in either case, it appears to move at 5 mph.

Light doesn't do this. We've measured it, and in a vacuum light always appears to travel at the same speed (we call it c for short). If you hold a flashlight, your friend next to you can measure the speed of light and will find it to be c. If we put you back on that train and stand your friend next to the track, you will see the light moving at c, but so will your friend. Not c +/- 20 mph, but c. Even if we put you on a rocket traveling at some significant portion of light speed, say 0.5 c, both you and your friend would still observe the light from your flashlight to be traveling at c.

This is what Einstein figured out, and this is what we mean by Relativity. From this, we also know that objects moving faster experience an increase in mass (you have to get moving pretty close to c to really notice), and as you approach c that mass trends to infinity. That's why anything with mass cannot achieve the speed of light, it would be infinitely massive, and thus require infinite energy to accelerate to that speed. Thus, only things with no mass (such as light) can move that fast.

The speed of light is the speed of information, including gravity, electromagnetism, and some other things I am not thinking of off the top of my head. For example, if the sun disappeared right now, the lack of gravitational pull would reach Earth at the same time as it blinked out from Earth's perspective.

What if you think of it this way. If the Sun exploded right now, we wouldn’t know for 8 minutes, but if you were to leave at the same time, at twice the speed of light and traveled for 8 minutes, you would be 24 minutes away from the explosion now.

So if you travel away from the earth and view it through a telescope, you would see back in time as you flew away, since the light traveling from earth wouldn’t be traveling as fast.