Recent comments in /f/askscience

bgraham111 t1_j4lmegs wrote

Reply to comment by gh0stwriter88 in How do non electric heat operated fans work? by ranman12953

Wait? I wasn't aware that the Amish used sterling engines. I'd love to hear more. Do you have any info on these?

Did you mean steam engine? Sterling and steam are different...

Of course, steam engines are a solution that the Amish use... I've just never heard of the Amish using high tolerance machining to build a stirring engine.

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gh0stwriter88 t1_j4ll5do wrote

Reply to comment by bgraham111 in How do non electric heat operated fans work? by ranman12953

Actually there are probably a lot more of these with sterling engines than TECs... since that's the Amish solution. It acutally makes way more sense than running electric motors to move the heat too since you arent' wasting electricity to do something that the motion of heat can do for you.... and all the heat is going into the room anyway.

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nakrimu t1_j4ljh8v wrote

Reply to How do non electric heat operated fans work? by ranman12953

I built Eco-Fans for years. They use a thermoelectric module that creates a hot and cold side when in use. When your fan heats up with this module it causes what’s known as the Seebeck Effect which causes electrons to flow and power the fan.

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chechomsky t1_j4lhozv wrote

Reply to comment by IAmAPhysicsGuy in How do we know that we are in a certain place inside our galaxy? and how do we know how big it is just by looking at the cross section we are in? by friday_panda

Our galactic “year” (time it takes for the sun to revolve around the center of the galaxy) is 230 million earth years. Is there enough rotation (I assume about 50 years of data) for us to use parallax to get a sense of our location?

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filladelp t1_j4lf5ad wrote

Reply to How do we know that we are in a certain place inside our galaxy? and how do we know how big it is just by looking at the cross section we are in? by friday_panda

This article about a “break” in the Sagittarius arm gets into direct measurements of distances a bit. Basically we can’t measure everything, but given what we can see and the measurements we can make (especially with the Gaia mission), we can work out the spiral arm structure nearby and infer the larger structure based on what we see in other galaxies.

https://www.nasa.gov/feature/jpl/astronomers-find-a-break-in-one-of-the-milky-way-s-spiral-arms

In the 1950s, a team of astronomers made rough distance measurements to some of the stars in these nebulae and were able to infer the existence of the Sagittarius Arm. Their work provided some of the first evidence of our galaxy’s spiral structure.

“Distances are among the most difficult things to measure in astronomy,” said co-author Alberto Krone-Martins, an astrophysicist and lecturer in informatics at the University of California, Irvine and a member of the Gaia Data Processing and Analysis Consortium (DPAC). “It is only the recent, direct distance measurements from Gaia that make the geometry of this new structure so apparent.”

Also take a look at https://en.m.wikipedia.org/wiki/Stellar_kinematics

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Blrja6040 t1_j4lepeq wrote

Reply to comment by [deleted] in How do non electric heat operated fans work? by ranman12953

What you are describing (and what OP is asking about) is actually a Peltier element. Aka thermoelectric effect.

Piezo electric is different and uses a quartz crystal to generate a brief electric current from a physical impact. This is the mechanism of many igniters used in gas BBQ grills and heaters.

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