swansont

The emission is not preferential in that direction. The atom doesn’t “remember” the direction a photon came from. It’s simply in an excited state, and the subsequent emission probability is symmetric. It’s just as likely to emit in the direction the photon came from as in the opposite direction. How does an atom “know” the difference between these photons? We can measure how long it takes for light to pass through various materials. Polyethylene, for example, has an index of refraction of around 1.5 for infrared light. So light goes at around 2/3 c through it.

My PhD dissertation was based on laser cooling and trapping and I did projects based in it for 30 years. Your summary misses the point. Cooling happens on moving atoms (because the hot atoms are moving) but the photon absorption interaction is not dependent on that. “for me” isn’t how science works. If you don’t have experimental evidence for a notion, it’s worthless. Then derive this relationship. Physics is based on models.

No. Laser cooling (Nobel prize 1997) wouldn’t work if the photon was emitted in the same direction, since no net momentum would be imparted to the atom. But that’s not what happens. The emission is symmetric and not preferential, so momentum is imparted to the atom. (And depending on the specifics, could heat or cool the atoms. Cooling is usually more experimentally useful) The momentum would be imparted regardless of separation distance. This wouldn’t seem to explain the T vs T^4 difference we observe for conduction vs radiation.

They could have a next atom, but it would be some distance away. But the shouldn’t matter much to photons. And an atom doesn’t “know” where the photon it absorbs came from.

No, this is patently untrue. S-B gives the radiated power. It does not require thermal equilibrium. Once there’s a gap there is no conduction. It’s why a dewar flask works so well; radiative heat transfer is fairly small for low temperatures, but becomes important owing to the T^4 behavior Being unaware of facts does not make them untrue. It gets to be frustrating to be told that they aren’t simply because you don’t know much about physics.

And S-B says radiated power depends on T^4 It’s as I described. An object in vacuum can only cool via radiative heat transfer. But all that radiation must hit the matter that surrounds the vacuum.

But radiative heat transfer depends on the difference of T^4, while conductive heat transfer depends linearly on the temperature difference. A small vacuum gap between the solid and liquid has a huge change in behavior, but should make no difference if it’s radiation, since all of the photons would still be emitted from the solid.

Oh, good grief.

How do solids transfer heat if they are e.g. immersed in a fluid? There are many issue with this photon model, many of which I’ve brought up, but one would also need to reconcile radiative vs conductive heat transfer having different behaviors.

My experience with GoPro from a few years back is that the battery only lasts a few hours. You’d need an external power source, unless they’ve gotten a lot better.

I’m not sure deficiency is the right word. Ships were smaller when the Key bridge was built in 1977. https://commercial.allianz.com/news-and-insights/expert-risk-articles/shipping-safety-22-losses.html “Container-carrying capacity has increased by around 1,500% since 1968 and has almost doubled over the past decade [referenced to 2022]. Ever larger vessels are on order.” The Dali’s capacity is almost 10000 teu, almost triple the biggest ship when the bridge was designed.

Useful as an exercise, perhaps, but it’s not the universe we live in. Your opinions mean little; in science it’s the evidence you have to support a falsifiable idea Can we stick to the topic? You keep avoiding addressing the question of the connection of relativity to the expansion of the universe

But we (scientists) are aware of relativity, so there is no difference in understanding. It’s a given that the measurement was made with our clock. And this has no impact on expansion. You could make the same flawed argument about any measurement affected by relativity, and yet GPS (for example) still works. You are overstating the impact of relativity; it does not render things unknown. It merely makes measurements frame-dependent, but with a known transform between frames. It's like saying that the fact that things can be written in both English and German means language has no meaning, as if one can’t translate between the two.

Any time or length measurement will be the same, but there will be length contraction of the object, and it will experience time dilation. Two observers measuring the decay of muons, for example, will get the same answer for the half-life, but it won’t agree with the lab frame measurements. Without relativity you could not reconcile the discrepancy.

This is only one frame. They must be moving with respect to each other to be different frames.

I was reading that the protective mini-islands are called dolphins https://en.m.wikipedia.org/wiki/Dolphin_(structure)

Marilyn Lands’ victory in Alabama should also paint a picture. I expect the polling numbers to skew toward Biden once the campaign ramps up the ads showing TFG’s support for overturning Roe and the GOP’s plans make it national, and to get rid of IVF and contraception.

Kelvin Klein. For your absolute unit.

You do realize there are countries that are not friendly towards the US, right? So they might not be inclined to sell uranium to the US. Areas that were part of the USSR are currently big producers of uranium. Hard to cut off the supply to someone when it’s under their direct control How/why is that more ethical or acceptable? You failed to address this.

Or spying on the subsequent Soviet efforts, or them sharing information. Once reactors started being built, information was available that wasn’t there during the Manhattan project. Theory became more useful, and less experimentation would have been required. e.g. knowing reaction cross-sections means you can model things rather than doing empirical studies to determine critical mass. Is starving and burning the population somehow more acceptable than using the atomic bombs?

“This page displays the current 270toWin Polling Average for each state” Average does not imply all Several national polls have Biden ahead https://projects.fivethirtyeight.com/polls/president-general/2024/national/ Also: it’s March In March 2016 there were polls that had Clinton over Trump by 10 points or more And: polls are not votes.

We measure it with our clock, since we’re doing the measurement. Most clocks in galaxies run at about the same rate, unless you’re near a black hole or moving at a significant fraction of c. (it’s been estimated that the center of the earth is younger than the surface by ~2 years. A pittance compared to 4.5 billion years) So what? We know this. We’re not comparing notes with any observers in other reference frames. How, specifically, does this tie in with expansion? I don’t see how your conclusion follows.

Guille Yacante has bid us farewell. We’ve locked the door, just in case. We don’t need any more unsubstantiated claims posted in multiple threads on the same topic but placed in inappropriate sections.

Yeah, independent creation happens all the time*. Especially on a smaller scale than calculus. “you stole my idea” is pretty common, too *I’ve got a cartoon sketch about dinosaurs watching a triceratops and claiming to be tricurious, and Colbert made a similar joke on his show a few years later. Nobody stole the idea from me, and it’s a fairly obvious play on words. Not the only time something like this happened to me.

! Moderator Note One thread per topic, please.