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Comment by bArray | Hacker News Reader

The way I like to think of it is like moving your hand through water in a swimming pool; the faster you try to move, the more the water (time) pushes against you. If you don't try to move your hand at all, the water (time) has seemingly no affect on you. In this analogy the water itself is space and time is the measurement of movement resistance.

Of course there are nice little things to explore with this, like moving through running water, currents (localized loops), deep water (dense space), resistance on small vs large things, etc.

If we imagine on the small enough scale where we're looking at single water molecules, resistance (time) doesn't even mean too much. As long as your water is liquid, your little molecules are bouncing around in all directions, only tending towards a given direction with some probability. Otherwise each direction is near and damnit equally easy to travel in.

That's my two cents anyway.

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This is not really an accurate analogy sorry. What is really happening is that everything (atoms etc..) are made of fields in which disturbances/patterns travel at the speed of light. When an object is moving through space, the fields have to move extra far to cover the distance through space, as well as to do the usual oscillations/vibrations/movements that give timing effects. This is where time dilation comes from. It's best understood with the reflecting-mirror-as-clock thought experiment.

> This is not really an accurate analogy sorry.

Well of course, it's an analogy, it only needs to be roughly correct. The idea is simply to build a mental model that many people can picture.

> It's best understood with the reflecting-mirror-as-clock

> thought experiment.

It's good, but not something that really resonates with people's first-hand experiences.

Well I don't think it's even roughly correct. Time is not friction or resistance.

To add to my comment: If you really want to understand relativistic time dilation, you want to understand the bouncing-light mirror-clock experiment. It's even in the article. And it's not even an analogy, it's really why moving objects run slow. You can derive the exact special relativity time dilation factor from it.

https://xkcd.com/895/

The thing is, in this case, the actual cause of time dilation is reasonably understandable. There's no need to go off and invent some wild analogy. But apparently the average HN reader prefers a wildly inappropriate and ungrounded analogy to putting in a little time to understand the commonly accepted reasoning behind time dilation.

This is an interesting analogy which might be helpful; but I don't think taking it down to an atomic level is useful, since it breaks the analogy. Time means just as much to a single atom as it does to your entire hand, the speed limit and "increase in drag" (in the context of this analogy) is the same. The hand takes more energy to accelerate than a single atom does, but that's not because of temporal dilation--it's just the normal old classical inertia.

> I don't think taking it down to an atomic level is useful,

> since it breaks the analogy

It was simply a suggestion as to why things might start behaving weirdly at the quantum level. My understanding is that very small things seem to act as if time doesn't really have any real favoured direction.

Of course the analogy is not perfect and does not measure correctly the scale of forces involved, or even how they behave at different extremes. It's just a rough and ready mental model to begin to see things in this framing.

You should scale time proportionally to the scale of space. Let's call one complete orbital cycle of one thing around another thing a "year", and one spin a "day". For example, one orbital cycle of the Sun around the center of our galaxy is "galaxy year".

If we measure a human body at the scale of seconds, then we can measure position of the human with precision to single digit meters. It will behave like a particle.

If we measure it at the scale of days, then it will start to blur, like a quantum particle: 30% at home, 30% at work, 30% everywhere else, including the Moon. We can use probabilistic math at this scale, to describe this weird behavior.

If we measure human at the scale of years, then the human body will demonstrate dynamics and predictable trajectory: home -> school -> work -> home. We can even invent a math formula, which will correctly predicts trajectory for a human at average.

If we try to measure a human at the scale of galactic year, then our detector will fail completely, because humans are short living objects.

When you measure your particles, you measure it at particle seconds, particle days, particle years, or at much higher scale?

Thanks for this! Never thought about it this way, but it's a terrific perspective / way to frame and explain probabilistic measurements in an intuitive way.

The difference though is that for a quantum particle, there is no "particle second" in the sense that you can't measure exactly where it is however fast you try.

"we can't measure it" doesn't imply "it doesn't exist". Maybe it exists, maybe not. Let's improve our tools and try again.

For example, it's impossible to measure distances shorter than photon wave length using photon stream, but it's easy to do using beam splitter and interference.

I never suggested that it didn't exist. It's just not a simple ball-like or point-like object, more like a cloud changing its form perhaps.

Your understanding of what is quantum and what is not, is dead wrong.

https://www.scientificamerican.com/article/giant-molecules-e...

IMHO, you should look at this video, where water droplet at macro scale «exists in two places at once» (demonstrates self interference when passing two slits).

https://www.youtube.com/watch?v=nsaUX48t0w8

Our solar system is just a few galaxy years old. Our circles (I hope they will be circles) around Big Attractor and Shapley Cluster are just started, so we are at year one.

If we scale up infinitely, then we will see that our Universe is "forever young", frozen in time.

If we scale down, we will see more and more exceptionally stable "dead" objects, completely missing short living ones, so our Universe will look "forever dead" for us again. Anything interesting will happen at our own scale only.

ahh. let's call your spacetime water something that evokes these qualities...

"ether"!

(this is not meant to be substantive criticism of your idea; I just think it's funny how much this sounds like the 19th century concept of ether that was abandoned)

If that sounds like an "ether" to you, wait until you read about https://simple.wikipedia.org/wiki/Higgs_field

Do you see much difference between ether, which is presented everywhere in our Universe, and Higgs field, which is presented everywhere in our Universe? Quote from your link:

«To justify giving mass to a would-be massless particle, scientists were forced to do something out of the ordinary. They assumed that vacuums (empty space) actually had energy, and that way, if a particle that we think of as massless were to enter it, the energy from the vacuum would be transferred into that particle, giving it mass.»

Haha, I do like the word "ether"!

I personally think of the water as space, rather than spacetime. I think time is a byproduct of space-mass interactions. I could of course be very wrong!

Space in [x,y,z], spacetime is [x,y,z;t]. It's math. Space represents the physical object, which is currently named as "physical vacuum" (literally "physical emptiness", where "physical" means that emptiness is not empty). It's hard to say what is represented by spacetime in math models.

> The way I like to think of it is like moving your hand through water in a swimming pool; the faster you try to move, the more the water (time) pushes against you. If you don't try to move your hand at all, the water (time) has seemingly no affect on you. In this analogy the water itself is space and time is the measurement of movement resistance.

Temporal friction!

I find it much easier to picture in relation to the unit circle. We're always moving at the speed of light, it just depends on whether that's at 1 second per second, 300,000 km/sec, or somewhere in between.

[1] https://en.wikipedia.org/wiki/Unit_circle

that was a really cool explanation and helped me create a mental model much easier than typical analogies, thanks!

I am not sure how accurate that analogy is, ( I guess most analogy are not made to be 100% accurate anyway ) but it explains the problem or help creating the image in my metal model far better than any thing else.

Thank You.

The map is not the territory.

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