Everyone knows what Time means, but do we really? How would you define Time to a 5 year old? Is our concept of time universal across cultures? Would every culture have similar explanation for what Time is?
Everyone knows what Time means, but do we really? How would you define Time to a 5 year old? Is our concept of time universal across cultures? Would every culture have similar explanation for what Time is?
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Time is a made up math problem for us to schedule things with.
Time is a dimension that we move through at a constant rate relative to our induvidual reference frame. It is similar to how we move left, right, forward, back, up, and down in our 3 spacial dimensions but we have less control over our movement through time than those as so far we can only move forward in time. If we greatly increase our speed we slow down our reference frame relative to other things moving slower than us and as a consequence move slower through time relative to things moving much slower. In a practical sense time is how we measure duration or the distance in a timeline between one event occurring and another.
>Everyone knows what Time means, but do we really?
What do you mean? We created the world and can define it how we please. Are you asking if we know what the thing we call time is? I mean, yeah. It’s a measuring stick for the linear sequence of events that make up the observable universe.
>How would you define Time to a 5 year old?
To someone that young, I’d just tell them it’s how we tell when to do things, and how close it is to morning or night, etc. We go to school at X time because the sun is up and we can see. Then the sun travels through the sky and sets, so it gets dark and we go to bed.
>Is our concept of time universal across cultures? Would every culture have similar explanation for what Time is?
Cultures across the planet have been measuring time by the movements of the sun and other stars for a very, very long time.
in thermodynamics, time is linked to entropy. We all know conservation of energy: energy cannot be created or destroyed.
However, energy can still be wasted. By burning fossil fuels, we convert chemical energy stored in the coal to heat energy. In this process, entropy is increased.
So if coal can be converted to heat, can we convert heat back to coal? No, that’s impossible. Even though the energy before and after the process is the same, it only works in one direction. Turning heat into coal would require to reduce entropy again.
And now time comes into play: Entropy can only increase over time. It can never reduce. the only way to reduce entropy would be to travel back in time.
During a car crash, the kinetic energy of the car is used to deform the car which produces heat. Again we cannot use the heat to turn the car back to its shape and accelerate it. So while certain states may be equal in energy (moving car, crashed car), the entropy and time determine in which direction the processes happen.
A common counter example is a pendulum or a swing. It converts potential energy to kinetic energy back and forth. The processes may works in both directions. You can play it backwards and wouldn’t notice it. So even though we see it moving, we don’t see in which direction of time it’s moving. Of course we know from experience the direction of time but in a video you couldn’t tell.
edit PS: this means an ideal pendulum or swing doesn’t produce entropy. In real life we have friction of course and if you fast forward the pendulum eventually stops.
For an actual five year old or someone not mathematics literate?
Okay you know how you used to be a baby but you can’t become a baby again? Everything that already happened is the past. And everything that hasn’t yet happened yet is the future. The trees you see used to be shorter. And in the future they’ll almost surely be taller, although we’ll have to watch to know for sure. But everything changes. Time is just how to count how much change can happen. The biggest changes take a lot of time. Little changes you might not even notice could take so little time it’s hard to count that fast. There’s some things that can change more quickly or slowly than you predict; some trees grow fast and others grow slow. But some things always change at about the same rate, like sunup sundown, phases of the moon, and seasons. We looked into it and we all pretty much agree that days go by faster than seasons and so on. On the other hand some people feel like a day lasts so long it’s boring while to others they feel like a day is not much. That’s more of an opinion. But we can all agree on these things:
Very few people actually have a good understanding of time and even fewer are confident in that understanding.
This is not really much of 5 yo explanation, but it’s the most fundamental we know of so far: Time is the ordering of causes and effects in space.
Things are made of particles, the smaller pieces of matter, and their “livetimes” are defined as events where and when they interacted with some other particle. Those events are defined by 4 numbers (dimension), 3 of where, and 1 of when. They might not agree at exact values, only on the order of causality. If 2 events are not related to each other, then tho diffeerent particles moving in different direction at different places could not agree which happened before the other one (as relativity stretches those values to ensure everyone sees the highest allowed speed in universe, the speed of causality also known as speed of light, to be constant). But if one caused the other, then everyone will agree that the cause happened first. Time is this net of ordering of causes and effects.
Also when things are first at low entropy (concetrated in unlikely pattern), then random interactions mixing them up will exponentially likely lead to higher entropy, so some people might believe that entrope defines time, but i think that it’s just that the existence of low entropy big bang makes it that time only always has greater chances of increasing entropy. That these causes and effects will more likely blend things into high entropy states. Therefore time causes increase of entropy, if is was low at the beginning, which it was, not the other way around.
To an actual 5 year old (or even a 10 year old), the usual thing is to explain MEASURES of time. Not time itself.
And there are the usual things like, earth has day/night cycles. Noon is the point where the sun is the highest in the sky (ie shadows are the shortest – which is how we created the first time measures – the sundial). Seasons are caused by the earth orbit. We can tell the season by measuring that same shadow. (the shortest of the short shadows) etc.
Modern measures divide a day into 24 hours. etc.
Months are just a human construct but, historically, it was linked to the observation of the moon. From new moon to crescent moon to full moon.
A lot there to unpack for a young child. These are not definitions of time but explanations of how we measure time.
Time is an illusion, lunchtime doubly so
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This is one of the most difficult concepts to explain in physics I think.
Time is the measure of causality, and increase in entropy of a given system.
So what does that mean?
I struggle to explain this to grown intelligent adults never mind a 5 year old.
I understand it but can’t really explain it, so do I really understand it?
Time is the measure of events moving forward as we see it. It passes 1 second per second as we see it..
Time is different for different observers.
This depends on how fast you are moving, or your frame of reference. (Also affected by gravity.) The faster you go, the slower time passes.
Time is the measure of causality, how one event affectes another event, like if you sit a cup on the table, then push the cup off the table, then the cup falls to the floor, then it breaks Into pieces when it hits the floor.
Each of these events are all caused by the previous event. Causality is the measure of these events as we see them..
Does that make sense?
Now I actually had this conversation with 2 ten year olds explaining special relativity and all that, 5 years ago, and im going to ask them both when they are 20 to describe to me what time is.. see how much of that coversation they remember or understood.
In my opinion, the two mental concepts that relate to time are:
Continuity – the fact that everything changes (past, present, future)
Simultaneity – the fact that things can occur simultaneously (at the same TIME)
When we use time related language, it is usually to describe these ideas!