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Show HN: What if the speed of light was 5 km/h?

rivendell.dmitrybrant.com

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Re: Show HN: What if the speed of light was 5 km/h?

#121

Some time ago I had the following shower thought: "the Speed of Light is pretty slow" How i got there: The closest major galaxy to the Milky Way is Andromeda, and is 2.5 million! light-years away. And this is the CLOSEST galaxy, the universe is extremely big. Of course that as you get closer to C, the traveling object will experience time dilation (relative to observer), so the time passed will be less. At 99.999% C,…

Not only that, from light's perspective, it takes no time at all. ;)

Re: Show HN: What if the speed of light was 5 km/h?

#122

Earlier quoted context omitted.

Yeah, it is and the math get's really counterintuitive to grasp since humans (at least me) have trouble thinking in exponential terms. If you accelerate at 1g constantly for 1y you travel 0.5 light years. You do that for 10.5 years and you reach the center of the milky way. You do that for another 4 (~14 total) years and you are in the Andromeda galaxy, and you do that for another 10 years (~24 years total) and you r…

> math get's really counterintuitive to grasp People always say that about speed of light stuff, but I don’t get it. Do you have any more examples of counterintuitive math? Because what you’re describing is basically the equivalent to compound interest in finance. (e.g. investing $100 at 10% interest over 10 years results in $260)

One million seconds is 11 days, a billion seconds is 31 years.

Re: Show HN: What if the speed of light was 5 km/h?

#123
post #99

Earlier quoted context omitted.

> At 99.999% C, the traveler would take ~11,000 years if we add more 9s, is it possible to reduce that number to within a human lifespan?

Yes. Time dilation (with respect of the stationary observed) is calculated using the Lorentz factor. At 99.999% of C, the Lorentz factor is ~223.6. It grows pretty quickly as you add more 9s to the fraction. Every two additional 9s multiply the Lorentz factor by ~10. So at 0.99999999999 c, it'd be ~223,607x. 2.5M years / 223,607 is: ~11 years Of course this is all highly theoretical. https://en.wikipedia.org/wiki/Lor…

The speeds are theoretical (unachievable), time dilation itself is robust and proved (gps wouldn't work as precisely without accounting for it)

Re: Show HN: What if the speed of light was 5 km/h?

#124
post #99

Earlier quoted context omitted.

> At 99.999% C, the traveler would take ~11,000 years if we add more 9s, is it possible to reduce that number to within a human lifespan?

Yeah, it is and the math get's really counterintuitive to grasp since humans (at least me) have trouble thinking in exponential terms. If you accelerate at 1g constantly for 1y you travel 0.5 light years. You do that for 10.5 years and you reach the center of the milky way. You do that for another 4 (~14 total) years and you are in the Andromeda galaxy, and you do that for another 10 years (~24 years total) and you r…

> If you accelerate at 1g constantly for 1y you travel 0.5 light years

Can't we accelerate past 1G constantly? Or do we expend so much energy doing it that we can't realistically do it with today's technology?

Re: Show HN: What if the speed of light was 5 km/h?

#125

What if the speed of light was 2c instead of c? Would that change anything for us?

Less latency in multiplayer games or Zoom calls. Because light can travel around the Earth 7 times in one second, that means one roundtrip to a server on the other side of the world must take ~140 ms (1/7th of a second) which is a timescale you are able to feel. That's lag in multiplayer games. I'm constantly amazed that the reason why multiplayer client-side prediction strategies like rollback netcode exist is becau…

[deleted]

Re: Show HN: What if the speed of light was 5 km/h?

#126
post #109

Light doesn't have a "speed" as in the usual meaning of the word "speed". Talking about speed requires defining spatial distances and time durations, which are in turn defined or created by the phenomenon of light. Light doesn't "travel". It's just an exchange of entangled photons creating the concept of time duration and distance.

So how do you explain that light can be slowed down?

The same way as we talk about it's speed and travel etc - using higher level human perceptions.

Re: Show HN: What if the speed of light was 5 km/h?

#127

Earlier quoted context omitted.

Yeah, it is and the math get's really counterintuitive to grasp since humans (at least me) have trouble thinking in exponential terms. If you accelerate at 1g constantly for 1y you travel 0.5 light years. You do that for 10.5 years and you reach the center of the milky way. You do that for another 4 (~14 total) years and you are in the Andromeda galaxy, and you do that for another 10 years (~24 years total) and you r…

> If you accelerate at 1g constantly for 1y you travel 0.5 light years Can't we accelerate past 1G constantly? Or do we expend so much energy doing it that we can't realistically do it with today's technology?

We can't necessarily survive that well when under acceleration greater than 9.81 metres per second per second for extended periods of time.

Re: Show HN: What if the speed of light was 5 km/h?

#128

Earlier quoted context omitted.

Yeah, it is and the math get's really counterintuitive to grasp since humans (at least me) have trouble thinking in exponential terms. If you accelerate at 1g constantly for 1y you travel 0.5 light years. You do that for 10.5 years and you reach the center of the milky way. You do that for another 4 (~14 total) years and you are in the Andromeda galaxy, and you do that for another 10 years (~24 years total) and you r…

> If you accelerate at 1g constantly for 1y you travel 0.5 light years Can't we accelerate past 1G constantly? Or do we expend so much energy doing it that we can't realistically do it with today's technology?

We can easily accelerate past 1g... 1g is just chosen for human comfort, but running any rocket engine continuously for a year requires an impossible amount of fuel.

Re: Show HN: What if the speed of light was 5 km/h?

#129

Earlier quoted context omitted.

> math get's really counterintuitive to grasp People always say that about speed of light stuff, but I don’t get it. Do you have any more examples of counterintuitive math? Because what you’re describing is basically the equivalent to compound interest in finance. (e.g. investing $100 at 10% interest over 10 years results in $260)

One million seconds is 11 days, a billion seconds is 31 years.

Thanks! But same here imho:

              1,000 seconds =          ~0.01 days (~17 min)
          1,000,000 seconds =         ~11.57 days (~12 days) 
      1,000,000,000 seconds =     ~11,574.07 days (~32 years)
  1,000,000,000,000 seconds = ~11,574,074.07 days (~32k years)
It all seems quite logical once you put everything into the same unit, I think.

Maybe it's just our human calendar/time unit rollercoaster (60*60*24*30*12) that's playing tricks on us here.

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