Simple box to detect pressure, temperature, water flow, and electrical power changes

coniform · 2 days

You can buy multiple-channel process controllers. Things like this. I'm not saying that's perfect for your application, but it's close.

You hook up your transducers (for temperature, power, etc.), set limits, and then wire up a relay such that it trips off power when anything goes outside of the limits. You may or may not want it to latch when this happens.

For transducers, pressure and flow are easy. You can get voltage out or 4-20 mA out (which is better, generally). What you need depends on your controller. Omega sells a bunch, and there are other suppliers out there, too.

For electrical power, depending on your requirements, you may just want to use a wall-wart transformer to get a voltage in the range the controller will read. If you have strict requirements (like you want the line voltage to be within ±1 V of 120 V), you'll have to find one without a regulator built in. These are a little harder to find, but they still exist.

Temperature, you have RTDs, thermistors, and thermocouples. Again, ultimately it depends on what your controller will read. Thermocouples are really easy to work with, but RTDs and thermistors are more accurate.

thexfatality · 5 days

Fundamental particles? No. The only fundamental particle predicted by the standard model that hasn't been conclusively observed is the Higgs boson. And the LHC is the only operating accelerator capable of looking for it.

Composite particles? There are probably some obscure excited states of mesons that haven't yet been observed. I don't work in the field, but I suspect none are easy pickings.

Hypothetical particles? Maybe. For example, JLab is looking for a heavy photon, but it's still a very tricky experiment, and might see nothing.

spsheridan · 6 days

The basic idea is that if the neutrino is a majorana particle, then it can get its mass through the seesaw mechanism. If it does, then it means there's a 4th neutrino that's much, much heavier than the 3 neutrinos we know about.

Many of these heavy neutrinos would have been created soon after the big bang. And they would eventually decay because they're so heavy that there's plenty of energy to form other particles. We already know that there's some CP violation in weak interactions. It could be that these heavy neutrinos also show it. And so they would decay to matter more often than antimatter, leading to the universe we see.

That's a very basic summary. There are plenty of different models and theories that predict things close to what I've said, but slightly differently in the details, which will eventually be judged based on the results of experiments.

spsheridan · 6 days

No, we don't know it occurs. It's forbidden in the standard model.

If it does occur, the half lives for the neutrinoless modes are on the order of a minimum of something like 10²⁵ years according to current limits, and could be even longer. In very rough numbers, that means if you have 10²⁵ atoms (about 100 kg) of something, and wait a year, you'll expect to see something like 1 decay. So you have to have very small backgrounds to see it.

We assume neutrinos are dirac particles by analogy with their cousins, the electrons, which we know are dirac particles. Both are leptons, and so it made sense at the time. Also, for massless particles, there's no distinction between dirac and majorana, so it didn't matter until we discovered neutrinos had mass.

mushpuppy · 6 days

You mean "at will". "Right-to-work" refers to not forcing employees to be union members.

spsheridan · 6 days

EXO-200 (now running)

Kamland Zen (now running)

CUORE (under construction)

SNO+ (under construction)

SuperNEMO (in development)

NEXT (in development)

GraXe (proposed)

And probably more that I'm not remembering.

eddier1200 · 10 days

I could've sworn this was in the sidebar...

But looks like it got moved to the FAQ.

GreenPlasticJim · 11 days

Neither space, nor time are quantized to the best of our ability to measure. There's no evidence that they are quantized.

ranavalona · 12 days

Imagine you have a long wire with some current flowing through it. What's actually happening in that wire is that electrons are moving at a roughly-constant speed, while the positively charged nuclei of the metal are sitting still.

Now suppose you have a charged particle and you give it some velocity parallel to the wire, going in the same direction as the electrons (so opposite the current). For simplicity, lets say they have the same speed. So, to the particle, the electrons look like they do when there's no current and the particle is still. But, meanwhile, special relativity says that the distances parallel to that particle's motion get contracted. So to that particle, it looks like all the nuclei are contracted together.

So, in the reference frame moving with the particle, it looks like there's a higher positive charge density on the wire, and so the particle just gets pulled in or pushed out by electrostatics. But in a frame in which the particle is moving, it looks like a force is being applied perpendicular to the direction of motion.

Hopefully that helps.

thexavier · 12 days

Someone got fancy with the tube bender.

Shadow_Jack · 12 days

I wasn't that impressed.

They need a better science advisor. Time dilation doesn't work that way. Speeding up will make the ship's elapsed time less, but it won't increase the time elapsed on earth.

There's no gravity along the axis of an O'Neill Cylinder, which is where they entered it. So why did the platform they were on plummet down?

ThisGoatStarves · 20 days

He talks about having to carry his ATM card and bus money in his hands for 13.1 miles. Sounds like he did a half marathon.

Tee-Wrecks · 25 days

No.

First of all, neutrinos travel slower than the speed of light. We know they have mass, so they can't travel the speed of light.

And neutrinos can't just escape the universe. Just because neutrinos interact weakly, it doesn't mean they stop existing in our universe after they're emitted. If we could build a sensitive enough detector, we could measure neutrinos from the beginning of the universe, analogous to the cosmic microwave background of photons. Once they're emitted, neutrinos can still interact with matter, even if the probability is small. And they're still affected by gravity.

Ant_of_Colonies · 25 days

This sounds suspiciously like a homework problem...

BrawndoTTM · 25 days

The FTL neutrino claim didn't involve the LHC at all. And it's since been resolved as a combination of a loose cable and a drifting clock causing the time-of-flight measurement to be off.

Frijid · 25 days

Maybe try running without the music. This is my personal experience, but music makes me a lot more conscious of the passage of time, which leads to feeling bored. If I run without music, I'm able to get into a zone where I'm just not thinking about time, and the miles can fly by.

schar · 26 days

There's a nuclear reaction known as beta decay. If an atom with one more proton and one fewer neutron has less energy than a given atom, that atom can beta decay. In beta decay, one neutron turns into a proton and an electron. The proton remains in the nucleus, while the electron flies off, carrying away some of the energy freed up by the reaction.

When beta decay was first observed, the scientists studying it noticed that the electron never quite carried away all of the energy freed up, though. Sometimes it would come close, but other times it would only take away a small fraction. The thing is, they couldn't see any other particles coming off, so it looked like energy was just disappearing.

The solution to this is a particle called the neutrino. It has zero charge (since the neutron and electron+proton are both electrically neutral, and charge must be conserved), and barely interacts with anything (hence why it was very hard to observe escaping decaying atoms). It (well, technically the antineutrino) carries away some fraction of the energy in every beta decay.

It turns out there's one neutrino associated with the electron, and this is the one associated with beta decay. There are also neutrinos associated with the muon and tau, which are the electron's more massive cousins.

Also, for a long time scientists thought the neutrino was massless. If it had a large mass, some of the energy from the beta decay would go into the mass of the neutrino, and so an electron couldn't carry away all the energy of the decay. But to the best of our ability to detect (even today), we see (rarely) electrons escaping with energy indistinguishable from the total energy of the decay.

But it turns out neutrinos do have a very, very tiny mass. It's so tiny that we haven't been able to measure it (though some of us are trying very hard!). We know because we have observed that they can oscillate. That is, an electron neutrino can turn into a muon neutrino while it's flying through space. This can only happen if a neutrino has mass.

FFLaguna · 1 month

I've been told that some physics theories state that there might have only ever been one created in the whole universe, so if that's true we may never know about it.

In a system of an electric monopole and a magnetic monopole (no matter how far apart they are), the angular momentum in the resulting electromagnetic field is proportional to the electric charge times the magnetic charge. We observe that electric charge is quantized. And we observe that angular momentum is quantized. Notice that I mentioned it doesn't matter how far apart the monopoles are. If there's even one magnetic monopole, then it leads to angular momentum quantization.

Incidentally, Blas Cabrera found the monopole on Valentine's Day, 1982. (Disclaimer: I am being facetious.)

bobzmccormick · 1 month

Diet Coke is a different formula than regular coke. It was made to taste sweeter than Coca Cola to begin with. The comparison to make would be with New Coke, which was the same formula as Diet Coke, but with corn syrup instead of aspartame.

spazzhero · 1 month

You're not going to find a place to yourself for that much. A studio will run you at least $100 more. And a place that takes pets might cost more on top of that.

natty_dread · 1 month

The photon interacts with whatever particle is creating the coloumb potential and gives it some of its momentum.

natty_dread · 1 month

It's just math. If you consider a photon (with energy E_0 and momentum vector p_0 in some frame) going to an electron and positron (with energies E_1 and E_2 and momenta p_1 and p_2 in that same frame), there's no solution to E_0 = E_1 + E_2 and p_0 = p_1 + p_2, using the relationships between energy and momentum.

McDermot · 1 month

This is the type of thing you can look up in the particle data book.

Dry air has a radiation length of about 300 m at 1 atm. The density will be lower at higher altitudes, so the radiation length will be higher but let's just keep that in mind for now.

The mean free path for a high energy gamma ray to pair produce is 9/7 of a radiation length. So let's say 400 m. Now, you can go up about 5 km before the density of air is halved. So, since the thinner air means a longer radiation length, we've got roughly 10 mean free paths, just from the air closest to us.

That means something like 50 out of every million high energy gamma rays will make it through the atmosphere. The rest are going to pair produce and make EM showers.

squidonsteroids · 1 month

If you've only got those two pieces of equipment, there's pretty much only one way to set them up.

mcpingvin · 1 month

Your problems at low temperatures are probably due to the batteries, rather than the diode. It takes liquid nitrogen temperatures (77 K, or -196 C) to change a diode laser's wavelength even a few nm, which you'd have a hard time seeing.

SaberTail

TROPHY CASE

SaberTail

TROPHY CASE

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