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

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

#141

Post by myrmidon »

ExoticPearTree wrote: post #124
marcyb5st wrote: post #106

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?

Sadly there is no realistic approach to get there (even assuming fantasy-levels of technology).

Chemical rockets are currently the only thing that allow sustaining such accelerations briefly for human-size payloads, but the low exhaust velocity and exponential reaction mass requirement make sustaining it for days/months/years completely impossible.

You'd have to supply the energy externally (i.e. some sort of beam propulsion), but getting any significant fraction of g out of such a system (with human-sized payloads) seems unlikely within the next centuries, especially as the distance increases.

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

#142

Post by TheOtherHobbes »

jjgreen wrote: post #130

What if the speed of light were 5 km/h?

Nothing would work, including us, because almost everything in physics and biochemistry works at higher speeds.

Whether or not the speeds at which things happen in physics, chemistry, etc are somehow absolute, or somehow inherently relative to c, and would speed up and slow down if c changed, is an interesting question.

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

#143

Post by rwoerz »

HDBaseT wrote: post #44
rootusrootus wrote: post #35

Whenever I think about light speed being fast, I imagine myself standing at the edge of the solar system and watching a hypothetical photon travel from the Sun to the Earth and taking 8 minutes. Suddenly it doesn't feel like light is really all that fast except at human scales. 5 km/h would be fascinating though.

The speed of light is unbelievably slow, not even as a cosmic scale, but on earth. We cannot play competitive multiplayer games globally, without 300ms ping. I dream of a world playing Black Ops 2 on a original PS3 in 2026 getting into a lobby because latency is low.

Ultimate counterevidence of an benevolent "intelligent designer"

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

#144

Post by rrr_oh_man »

MathMonkeyMan wrote: post #132
rrr_oh_man wrote: post #117

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)

The proper time (that is, the time the traveler measures on a clock) goes to zero very quickly towards the end. Even with both axes plotted logarithmically, it's just a sudden drop at the end towards light speed. - [pic]( https://home.davidgoffredo.com/hackernews/proper-time-one-li... ) - [plot]( https://home.davidgoffredo.com/hackernews/proper-time-one-li... )

Links seem to be broken?

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

#145

Post by consp »

myrmidon wrote: post #141
ExoticPearTree wrote: post #124

Earlier quoted context omitted.

> 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?

Sadly there is no realistic approach to get there (even assuming fantasy-levels of technology). Chemical rockets are currently the only thing that allow sustaining such accelerations briefly for human-size payloads, but the low exhaust velocity and exponential reaction mass requirement make sustaining it for days/months/years completely impossible. You'd have to supply the energy externally (i.e. some sort of beam pr…

> You'd have to supply the energy externally (i.e. some sort of beam propulsion), but getting any significant fraction of g out of such a system (with human-sized payloads) seems unlikely within the next centuries, especially as the distance increases.

Or some form of ram scope, plenty of H everywhere, but those also have the issue of you collecting things while going at relativistic speeds.

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

#146

Post by MathMonkeyMan »

rrr_oh_man wrote: post #144
MathMonkeyMan wrote: post #132

Earlier quoted context omitted.

The proper time (that is, the time the traveler measures on a clock) goes to zero very quickly towards the end. Even with both axes plotted logarithmically, it's just a sudden drop at the end towards light speed. - [pic]( https://home.davidgoffredo.com/hackernews/proper-time-one-li... ) - [plot]( https://home.davidgoffredo.com/hackernews/proper-time-one-li... )

Links seem to be broken?

No, but IPv6 only these days. I never set up dynamic DNS.

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

#148

Post by classified »

teekert wrote: post #74
classified wrote: post #72

Earlier quoted context omitted.

> my back arrow first slows me down That's exactly what would happen ins space.

On some more testing, I don't seem to alter direction, just suddenly start to accelerate again. Ah well, it worked mostly.

The part you're excluding with "mostly" is still just the laws of physics. And it works according to those.

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

#150

Post by rrr_oh_man »

lostlogin wrote: post #133
mjmas wrote: post #127

Earlier quoted context omitted.

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

Gravity on Earth varies about .7%. Increasing the acceleration a little bit more than that (eg to 1%) would make a difference. https://en.wikipedia.org/wiki/Gravity_of_Earth

> "Increasing the acceleration a little bit more than that (eg to 1%) would make a difference."

Wouldn't that be only a few months on a decades-long journey at 1.01G vs 1G??

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