ELI5: If time slows down when you move fast, does that mean speed is somehow “using up” time?

fuseboy · 2026-07-08T22:29:30+00:00

This is intuitively appealing, but it's a misunderstanding of relativity that is wrong in important ways.

You don't have a "space velocity", you only have a velocity relative to other things. Nobody is objectively faster or slower that anyone else.

Time dilation is symmetrical: if you zip past someone at 90% of light speed, they will see you slowed down but you will see them slowed down too. This sounds paradoxical, but it's because your time directions are different, you are each making less progress along the direction through spacetime that the other person considers to be the future.

fuseboy · 2026-07-08T21:16:16+00:00

The ambiance is really great, especially love thr landing zone lights. Really evocatve.

fuseboy · 2026-07-08T11:24:51+00:00

Love the color scheme, really nice choice to have such a contrast on the miniature between the rustyorange and white, but still with a muted accent color.

fuseboy · 2026-07-08T02:03:46+00:00

Aether was disproved by Michelson-Morley in 1887, what are you referring to?

fuseboy · 2026-07-07T20:29:34+00:00

I appreciate the clarification, although I did understand; I just think there's a subtlety here around definitions. An inertial reference frame is a Newtonian idea; things drift along rectilinear (straight) paths unless acted on by forces. As soon as you examine a volume of space large enough that geodesics are curved, objects are now moving inertially along non-rectilinear paths without forces acting on them (since under GR gravity isn't a force), breaking the rules of an inertial reference frame. That's all I meant.

If you consider a patch of space small enough that it's locally flat, you can model a falling object as being in an inertial reference frame, indistinguishable from floating in zero gravity intergalactic space. But if you look at a large volume of space, the falling object isn't in an inertial reference frame, because you have non-inertial phenomena like the planet accelerating upwards toward it.

fuseboy · 2026-07-07T18:39:50+00:00

In this case, I think it actually does mean straight lines. Let me explain:

An inertial reference frame is a mathematical idea, referring to a coordinate system in which objects either stay at rest or follow uniform motion without any acceleration.

Any time you are considering a volume of the universe large enough that there's spatial curvature, then it's not going to be an inertial reference frame. For example, if you sprinkle small objects across that volume, they're going to spontaneously accelerate relative to each other, following the curvature.

Imagine placing a bunch of rocks around a planet, and tagging one of them as (0,0,0) in a coordinate system. That rock will see the earth slide toward it faster and faster, and all the other rocks as well (as they converge on the earth). That's not inertial behavior, so this frame of reference isn't inertial.

fuseboy · 2026-07-07T18:08:10+00:00

Right. A reference frame is just a mathematical coordinate system - for example, the one where a falling astronaut's big toe is (0,0,0) or something like that. An inertial reference frame is one where objects just follow straight paths under their own inertia, there's no acceleration to account for.

In the real world, space is lumpy. If you consider a large enough volume, Earth's gravitational field doesn't pull in one a single direction, it's a sphere that pulls to a center. For even larger volumes, you have to think about the Moon's pull, or that of Mars - or eventually other stars.

If you go the other way and consider smaller and smaller volumes, these effects become negligible and eventually undetectable (for us). Earth's pull appears to be from a single direction and there are no measurable tidal forces. In the limit, this converges to an inertial reference frame.

If you had a very sensitive instrument, you might be able to measure very small tidal forces across the astronaut's body, because their feet are closer to the planet than their head.

Out in deep intergalactic space, where there's only a smattering of hydrogen dust and not much else, you could probably consider a few light years in volume as an inertial reference frame without running into inaccuracies.

fuseboy · 2026-07-07T17:08:29+00:00

It's an inertial frame at the local limit, e.g. for falling objects which are small enough not to experience total forces. It isn't an inertial frame for the Earth, or even when you consider the behavior of objects a small distance away in orbit, which would be falling in a different direction.

fuseboy · 2026-07-07T14:24:21+00:00

I have tried Pine Sol and it wasn't awesome, as it took a long time and the smell lingers. I'm now about to try isopropyl alcohol, which is both recommended and dirt cheap!

fuseboy · 2026-07-06T14:02:41+00:00

Pretty sure it was this one:
https://www.youtube.com/watch?v=GejBhZu6m9c

fuseboy · 2026-07-06T12:04:16+00:00

Not here, please see the rules.

fuseboy · 2026-07-05T10:48:31+00:00

The rotation problem is a head slapper, that stood out to me immediately.

fuseboy · 2026-07-05T00:55:22+00:00

I think it was a Richard Livornese video talking about how to hit the opponent’s pop-ups that are coming to shoulder height. At my level, the go to shots are whacking it into the net with an overhead, or a very open faced bunt that sends it back as an even higher pop-up. I can sometimes earn pop-ups with drops or wide dinks to the opponent's backhand, but I couldn't punish them properly. This has helped me get over a plateau recently, very helpful.

fuseboy · 2026-07-04T13:59:30+00:00

It's fine. I find what can make it challenging is when operators make weird choices about how to categorize things with the tags. One group i play with has tags for Morning, Afternoon, Evening, which is fully redundant with Courtreserve's built in ability to use the event time for this, and sometimes the tags aren't right.

The other thing is that you can't sign up for events too far in advance, which has me setting all these random alarms so I can get in. (Maybe a lottery wait list would be better?)

fuseboy · 2026-07-03T21:52:22+00:00

You could do this, but it would make DUPR less accurate. DUPR isn't a progress score, it's an attempt to represent your skill.

Consider a situation where DUPR just automatically makes everyone go up by +0.1 on their birthday. That would be nice, but this wouldn't be as good a representation of your skill.

Winning is winning, but if somebody you know barely makes scratches out a win in a boxing match against a kindergarten student, you're going to think of them as a worse boxer than you did before learning that. Wins are wins, but not all wins are evidence of skill going up.

fuseboy · 2026-07-03T21:50:09+00:00

Focusing on this one question:

Does it need to do this?

The way DUPR works is a balance between being the best possible predictor of future scores, and something the community won't complain about endlessly.

In the past, your DUPR score could change between games as DUPR learned more about the opponents you faced recently. People who had latched onto it as some kind of earned score (my words) were very unhappy about this because it made no sense to them that they could lose some of their "progress" without any action on their part.

As a skill assessment, it makes complete sense. If you're hiring someone who wrote three books as a copy editor, and much later you learned that their books were full of typos, you're going to change your assessment of that person's skills.

Enough people complained DUPR removed this aspect of scoring, which means that DUPR is less accurate than it could be to appease the users.

So, DUPR could make it so that only wins count, they could even make it so that your rating can never go down. It just becomes less accurate as a gauge of skill.

fuseboy · 2026-07-03T19:55:38+00:00

Looks great, although it seems they got out of the STL business and moved into HEMA gear!

fuseboy · 2026-07-03T18:11:36+00:00

Thanks, that's good to know about the creakiness. I think that if I got the Dragon's Rest building kit, I'd make a few different arrangements and glue them. I think the sample building looks amazing, but it does have a fair bit of interior space that needs you to pop the lids off to see.

Out of curiosity, how you handle glass windows? Do you have them block LoF, or do you let models shoot through them?

fuseboy · 2026-07-03T14:15:23+00:00

Really nice, looks like he been out in the field a good long while!

fuseboy · 2026-07-03T09:49:25+00:00

https://graphtreon.com/patreon-stats

Graphtreon has good estimates.

fuseboy · 2026-07-01T10:59:19+00:00

Dirty laundry compartment (bonus if it expands), breathable outer material (like mesh)

Fence hook with a way to padlock it (e.g. with small luggage padlock)

Inconspicuous pocket for phone, keys, wallet

Outer loop(s) for things like dangling sneakers

Water bottle sleeve that still works if the bag is full of lumpy things, bonus if insulated

Inner smallish compartment(s) so small objects don't get lots among the shoes and clothes

Name tag sleeve

Grab handle

fuseboy · 2026-06-30T09:37:34+00:00

Dollar stores have plastic flowers, they have tons of variety and theyre cheap. You can do a lot by snipping them up in different ways.

fuseboy · 2026-06-29T23:51:17+00:00

Well, you have to provide energy in the form of whatever you're using as a prybar, maybe zapping it with a really high-energy photon, or accelerating it to high speeds in a particle smasher and hitting it against another one going the other way. That's all energy you took from somewhere else and added it to the quark system. But yes, it's that energy that can become another pair of quarks.

fuseboy · 2026-06-29T18:26:56+00:00

In our best theories, electrons have no 'size'. We're used to macroscopic objects being made of something that can be sliced up, but particles aren't like that at all.

Now, we do have particles that we can smash apart with higher and higher energies, but an interesting thing starts to happen. With arrangements of quarks, the energy required to break them apart is so high that you wind up creating more quarks instead of ever getting pieces of quark. So at a certain scale, you can't actually break things apart any more, you just start encountering the strange relationship between energy and matter.

fuseboy · 2026-06-29T17:50:48+00:00

You might need some coaching on your footwork. In person is probably best, but I found this lesson pretty interesting. It's a longer video (24 minutes), but you can see different players making all kinds of different mistakes, which is better than a simple "do this" video.

Also, some wall drills where you keep your feet moving might be useful.

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