Relativity is insane. Einstein literally rewrote the formula for “add two velocities together”. You know, like 20 km/s + 20 km/s, WHICH YOU WOULD THINK just turns into 40km/s, but it’s actually ever so slightly less.
It goes really deep in terms of what it affects in physics.
On the contrary. The URL you post here has been submitted to HN several times (plus my attempt to make the title a little catchier as I linked to the GitHub issue #28, which I titled “Don’t add website DRM to Chrome” in a defensible attempt to expand the title the best I credibly could under HN rules - the issue title is just “Don’t.”)
These all died in obscurity. This blog post by contrast had a catchy title that HN actually engaged with, and as such is measurably superior.
Blame dang & co, for making forum software in which blogspam is the only way to add comment or meaningfully add context and editorialize. (Since blogspam is officially discouraged I’d say the software is not fit for purpose.)
> Why do some stores need a pin on my debit card, and some do not?
Oh that’s easy enough. If they need a PIN it’s actually being run as a debit card over the debit card network. Otherwise it’s being run as a “check card” over the credit card network (with higher fees and better consumer protections). It’s just backed with money instead of a line of credit.
> Why do online stores need my name and address, but IRL ones do not?
IRL stores have access to the actual card (with your name) and having this artifact present makes it much less likely that you are a fraudulent fraudster committing fraud, so the processors are willing to take it.
> How can restaurants swipe my card now and charge me later?
the good news is if the store ever defrauds you, everyone knows where to find the store! Unlike fraudsters making purchases.
> having 10 million single window units blasting walls of heat into a crowded city very quickly becomes an arms race where nobody wins (except perhaps the AC manufacturers).
Is this more or less energy than would be used for heating, in an equivalent city that seldom wants A/C? Remember, with the exception of heat pumps (hardly universal and less efficient at low temperatures) A/C is usually much more efficient at changing indoor temperatures, and also that 100F -> 72F is a smaller temperature difference than 32F -> 72F.
Idk, it seems reasonably obvious that there is activism and litigation and nonprofits and bureaucracies all studying environmental issues, and these are all operated by people, many of whom get more money and attention was a result of the concerns they raise. There is some opportunity for a conflict of interest.
One question, though, is whether they take that opportunity. Another more salient question is whether the Wall Street Journal, of all the possible papers, has fallen under the influence of such groups.
And it certainly seems as if they’ve found some people with elevated lead levels in blood, and ground and water samples that exceed EPA limits.
Note that the half-mile statistic is connected to underwater cables, not buried cables. It is certainly an overcount, but it is probably not trivial to assess the local hydrology and the extent to which children’s play areas might be exposed to such water.
This is part of a series that’s been running in the WSJ for a week now. There are still lead lined cables all over the country, with little awareness of the risks they pose; the first article in the series discussed cables going past playgrounds and daycare centers.
“Aerial lead cabling runs alongside more than 100 schools with about 48,000 students in total. More than 1,000 schools and child-care centers sit within half a mile of an underwater lead cable, according to a Journal analysis using data from research firm MCH Strategic Data.”
We took lead out of gas (except general aviation). Everyone who buys or rents an older home or even just buys paint at the hardware store is reminded of lead in paint. Most are aware of lead in pipes, especially where these pipes are present. Yet lead levels in children nationwide are still substantially higher than they should be given the mitigations that have already been done.
These cables are likely a huge portion of what’s left, and almost nobody has heard of them. Even when they’re right in front of your face hanging from a telephone pole.
If you need speed and money is of limited concern, consider fiber. There are some nearly invisible configurations that stick onto the walls, and baseboards or crown molding can be a channel as well. It’s possible you could sneak it under a door, or through a small gap in the frame behind the trim. You might even be able to smuggle it through electrical conduit for short distances, since it’s non conductive (but don’t trust me on the safety or compliance issues of that, I wouldn’t trust myself, though I’ve seen zanier from the previous homeowners here...)
The obvious downside being the extra expense of media conversion.
> Certainly I would have expected the orbit to go higher the faster the planets moved? Is that not the usual effect of increasing speed?
That rather depends on what you mean. The usual effect of increasing speed in a circular orbit at any given moment is to change it to an elliptical orbit, where the apoapsis is further away from the center of gravity and the object in question moves slower. And if you increase speed again at the apoapsis, you can make the orbit circular again, but the object will be moving much slower than it was to start. Thus two accelerations, both prograde, have the net effect of substantially reducing the prograde speed.
For any given circular orbit, though, lower means faster.
Oh, wait … you’re telling me they just phased that out? :(
But yeah, as it turns out energy prices matter; it’s not just corporate overlords of the fuel companies spreading astroturf when people point out the still-high costs of using renewables. It matters to homes and cars and industry too, and when energy costs more, the nation will have less.
As others have noted, the speed of light (in a vacuum) will always constant. To be nice and pedantic, you can always slow it down by making that light go through a medium, where it will go slower (e.g. any prism that makes a pretty rainbow). It’s a cheat of sorts, but the speed of light isn’t some special property of light: it’s a property of spacetime. There is a maximum speed of anything at all, and unimpeded light goes this speed. For most astrophysics purposes this doesn’t worry us much, as space is essentially empty.
You can also “slow light down” by just making it go further: a few clever mirrors will do this easily. This is even more of a cheat, as the light itself isn’t any slower, it just gets where it was going a little later because it went further.
In a sense that’s what’s happening here: the spacetime is being stretched on one axis and squeezed on another, as gravitational waves pass through it. It isn’t by much, which is why we need a whole galaxy to measure it.
This is literally within the boundaries of the city of San Francisco, where having a car is only a prerequisite for success if your job is “driving”.
If you’re going to lament the car-focused society we have created, I understand and sympathize emotionally — but you should really take care to relent in those places that are most like the world you would prefer.
It goes really deep in terms of what it affects in physics.