Ask any question you want about Physics

a reply to: zatara

If you open the door of a space ship, it's a bit like opening a can of snakes, everything rushes out at once.

But our atmosphere gradually decreases in pressure out to over 6000 km. When molecules are so far apart that they no longer bounce around off each other, they are no longer pressurized.

a reply to: DanielKoenig
Coal, Oil and natural Gas non-renewable resources won't last forever, so we have to find alternatives. I think studies have shown that we actually use more energy to produce ethanol than the energy that's in the ethanol so while it may seem to be renewable it's really not and you have to ask why we would do that. The reasons must be political because they don't seem logical.

I think it makes sense to look at the total cost of technologies like wind and solar. They probably aren't yet that economical with respect to fossil fuels but to encourage their use some smart level of government subsidies probably makes sense. Eventually as fossil fuels become more scarce, prices will rise and the economics of "green" alternatives will become more favorable without government subsidies. I've thought about maybe adding solar panels to my roof but I'm not sure it makes economic sense yet but with improvements in solar cell efficiency and longevity eventually they will probably make a lot more sense. One big problem with renewables is lack of adequate energy storage methods but that doesn't mean we shouldn't use them, just that they are limited until better storage methods can be developed.

Coal is dirty, but in the US at least a lot has been done to clean up coal plant emissions. Other parts of the world might have more progress to make. Burning coal emits more radiation than nuclear plants, provided there are no accidents or disasters. One problem with nuclear power is the true cost is never calculated, so we don't know what it's really costing us, but it's probably a lot more than we think. The two biggest costs not included in current costing models for nuclear power are:

1. Cost of insurance of nuclear power plants to cover the disaster decontamination and clean-up which may not even be achievable in reasonable time-scales with Chernobyl and Fukushima. Governments have stepped in and disrupted nuclear power economics by providing very limited government insurance coverage since private insurers won't cover it, and in Fukushima the true cost of that disaster far outstrips the government plans for government insurance. So until the Fukushima disaster is cleaned up we can't even calculate the cost since we still don't know the cleanup cost, or worse, effective cleanup may not be possible. Some related issues with the Price-Anderson Act are discussed at that link. It didn't expire in 1967 like it should have:

In a 1957 report, the U.S. Senate wrote that Price-Anderson would only be needed for ten years because “…the problem of reactor safety will be to a great extent solved and the insurance people will have had an experience on which to base a sound program of their own.” But the historical record debunks this initial optimism.

Japan's law was different and supposedly the operator TEPCO was liable, but they only had about $1 billion in insurance which didn't even cover tsunamis, and they've already had to pay out over $50 billion in compensation which is money they didn't have so the government had to subsidize them, and costs are expected to reach up to $120 billion. Look at the UK where nuclear liability is capped at a tiny US$220m, and compare that to what TEPCO has had to pay so far.

2. Waste disposal. How can we be using nuclear power so long without knowing the cost of disposing of the waste, and not even have any plans for disposing of it? Only Sweden and Finland have such plans:

Nuclear industry reveals its unsolved problem: waste

If the true cost of nuclear power was calculated to include the true cost of insurance and waste disposal, I think the cost will be shocking.

Non-gas powered cars have had issues with economics. According to the following article electric cars might become economically competitive by 2026 but I don't know if that's true and apparently subsidies will expire long before then:

Will End of Subsidies ‘Kill’ Electric Vehicle Market?

For years, the federal government has subsidized the electric car revolution by giving $7,500 tax credits to vehicle buyers. But relatively soon the subsidies will be going away, and some think the result will be a disaster for electric vehicle makers.

Auto sales and information site Edmunds put out a paper last month that argues that the end of the subsidies will “kill” the U.S. electric vehicle market. Vehicle manufacturers each get credits for their first 200,000 customers. Tesla has sold almost 100,000 vehicles and is expected to run out of credits next year. It has more than 400,000 orders for its Model 3, so the company is in no immediate danger of running out of buyers.

But there’s obviously a big difference between paying $35,000 for a Model 3 and paying $27,500. And as Tesla tries to get more mass-market buyers, it will be competing with gasoline and hybrid cars that sell for closer to $20,000. Eventually, Bloomberg notes, electric car prices are expected to be lower than gas-powered vehicle prices because batteries are getting cheaper, but not until about 2026.

Ill be making a separate thread on climate change soon based on comments from a brilliant scientist who worked with Einstein at the Institute for Advanced study and has done some surprising research and has some interesting things to say which make a lot of sense to me. Some people won't like what he says though.

originally posted by: BASSPLYR
a reply to: BELIEVERpriest
Eros is a man you should pay attention to when he speaks

Crikey didn't know anyone payed that much attention to me haha, but posting a similar bit of background as Arbitrageur did my scientific background is basically:
Masters - Physics and Astronomy
PhD - Experimental Particle Physics - I worked on the T2K neutrino long-baseline experiment
Post-docs :
1) Dark matter experiment, - built one of the two largest running experiments to date
2) Neutrino Physics - building a TPC to what you might describe as a service measurement, in order to make neutrino beam simulations more accurate, which ultimately would improve uncertainties for T2K and the next gen

My skillset is mostly in hardware - which kinda means a career deadend in academia, but, gonna keep having fun while I can. So fair amount of knowledge in light detection, Nobel gas purification, building detectors and devices for high radio-purity and use in-vacuum. General electronics debugging... yeah... all over the place

Its why Ill often pop into the odd thread and rant away about something which results in an assay like post.

a reply to: Arbitrageur



If I put twenty five pounds of pressure in the four tyres on a truck. and then put them on a truck that weighs a ton. Isn't their now a quarter ton plus twenty five pounds of pressure in each tyre.?

a reply to: ErosA433
Your contributions are very much appreciated here, as are all those by people like you who know a lot about physics.

originally posted by: anonentity
a reply to: Arbitrageur
If I put twenty five pounds of pressure in the four tyres on a truck. and then put them on a truck that weighs a ton. Isn't their now a quarter ton plus twenty five pounds of pressure in each tyre.?

A typical truck tire has steel belts and they constrain the tire volume to a significant degree, so much that a mechanic has claimed even a tire gauge accurate to 0.1 psi can't reliably measure any difference:

Is tire pressure different if you measure with tire off the car?

Working in an automotive shop, to satisfy my own curiosity, I have measured this with a digital gauge within a tenth of a psi. For all practical purposes, there is no difference.

A tire is a very solid and sturdy structure and its interior dimensions aren't going to change just from the weight of the car. When the tire deforms at the contact patch, it deforms equally opposite to it. If the bottom of the tire is squashed, the top is a little bit bulged. So, if your mass of air is constant and the volume of space it occupies is constant, then the pressure will be constant, too.

Maybe with a more accurate gauge that could measure in 0.01 psi increments some difference could be established? But if that's what it takes to find it, the difference can't be very much.

Question.
Why does a pendulum slow down at the equator as compared to the poles?

originally posted by: anonentity
a reply to: Arbitrageur

If I put twenty five pounds of pressure in the four tyres on a truck. and then put them on a truck that weighs a ton. Isn't their now a quarter ton plus twenty five pounds of pressure in each tyre.?

The issue is your tire has 25 pounds per square inch, 25 not pounds, and there are a lot of square inches. There is an outer cylinder that touches the road, an inner cylinder that touches the wheel, and two side walls. With a radius of 10 inches and a width of 10 inches, the area of a cylinder is 2*pi*r*w ~ 600 square inches. With each cylinder roughly that, and with each of the side walls roughly half of that (for this quick estimate) you get a total of about 1800 square inches. And with four tires you have 7,200 square inches. With 25 pounds per square inch, the total outward force of the stored air is 180,000 pounds or about 90 tons. So if a ton is added on those tires, the pressure should go up by about 1%, or 0.25 psi, by this calculation. Here I use approximate numbers for a car tire, and just four tires. If the tires are bigger and there are more of them (perhaps six) then the percent increase will of course be less. Also, since this is just a forum post, I have not tried to be careful to get exact numbers, but I hope the physics behind the answer is clear.

a reply to: Arbitrageur

after reading alot of physics books and other books on the history of the world , I am starting to think that our reality is "mind over matter"

that consciousness manifests reality

I am not smart enough to understand the maths on this , Do you think that quantum physics is pointing to this as well ?

thanks

a reply to: BASSPLYR

Its an excellent thread. The guys in it are tip top with their knowledge of most things physics wise.

I couldn't agree more - I have waded through it, sometimes 20-30 pages at a time. Thanks to all who provide great knowledge.

originally posted by: Hyperboles
Question.
Why does a pendulum slow down at the equator as compared to the poles?

I think it would be difficult to measure with a pendulum so I have to ask, did someone measure this with a pendulum? We can calculate what the slowdown would be and that could definitely be measured using atomic clocks which can make much more accurate measurements than a pendulum. In fact NIST has measured a time difference between two very accurate clocks where one was moving only a few meters per second with respect to the other, and because of the Earth's rotation motion at the equator is in the ballpark of 1000 mph relative to the poles. It's a prediction of relativity that clocks will run slower when they are in motion relative to the observer, and this has been confirmed with atomic clocks.

originally posted by: delbertlarson

originally posted by: anonentity
a reply to: Arbitrageur

If I put twenty five pounds of pressure in the four tyres on a truck. and then put them on a truck that weighs a ton. Isn't their now a quarter ton plus twenty five pounds of pressure in each tyre.?

The issue is your tire has 25 pounds per square inch, 25 not pounds, and there are a lot of square inches. There is an outer cylinder that touches the road, an inner cylinder that touches the wheel, and two side walls. With a radius of 10 inches and a width of 10 inches, the area of a cylinder is 2*pi*r*w ~ 600 square inches. With each cylinder roughly that, and with each of the side walls roughly half of that (for this quick estimate) you get a total of about 1800 square inches. And with four tires you have 7,200 square inches. With 25 pounds per square inch, the total outward force of the stored air is 180,000 pounds or about 90 tons.

I see what you're saying up to this point.

So if a ton is added on those tires, the pressure should go up by about 1%, or 0.25 psi, by this calculation.

I would use a different calculation to analyze the tire pressure in this example, the ideal gas law, stated as pV=nRT, or restated as p=nRT/V where

p=pressure
V=Volume
n=number of moles, a value related to the amount of air in the tire, that will only change if air is added or let out
R=gas constant, which won't change because it's a constant.
T=Temperature

So, nR won't change the tire pressure unless we add or remove air, so we can consider that constant for our example.
Increased temperature will definitely increase tire pressure, all else being equal but we assume that's stable in this example.
The only thing that leaves is volume as potentially having an influence on pressure (assuming the ideal gas law is an adequate model in this case). So if you want to argue that adding the weight of the car is going to change the pressure, what you would really have to show is that it would change the volume somehow. The car does get a flat spot where the tires contact the ground, so if the rest of the tire geometry was unchanged you might try to argue that's a decrease in volume, and pressure would go up.

However going back to the mechanic's measurements, he's also aware of the ideal gas law and since he can't measure any change reliably to the nearest 0.1 psi, his hypothesis is that the volume of the tire isn't changing to an amount which results in a measurable change in his pressure gauge. That is to say the decrease of volume at the flat spot he feels is offset by an offsetting increase in bulging elsewhere, so based on his measurements he thinks the volume of the tire must be staying fairly constant when the weight of the car is added for him to not measure any pressure change. This is why I said there might be a small change, because I don't know if the volume of the tire is changing.

By the way I've also tried to measure this but my tire gauge only had increments to the nearest 1 psi which wasn't accurate enough, which is why I'm interested in the gauge the mechanic used which measures to 0.1 psi and should have been able to measure the change if it was .25 psi.

originally posted by: sapien82
a reply to: Arbitrageur

after reading alot of physics books and other books on the history of the world , I am starting to think that our reality is "mind over matter"

that consciousness manifests reality

I am not smart enough to understand the maths on this , Do you think that quantum physics is pointing to this as well ?

People like hearing that their minds control the universe. I guess it makes them feel powerful. So if you write books and make videos telling people what they want to hear, you're probably going to sell a lot of books and videos.

Here's something you don't need much math to understand. We think the universe is over 13 billion years old and that earth is over 4 billion years old, so most of the time the universe existed, the Earth didn't even exist. And for most of the Earth's existence, humans didn't exist, so all evidence points to a reality which far predates humans and their consciousness, so it seems pretty obvious reality existed just fine without our consciousness.

However humans have an impressive ability to change their environment, sometimes for the better, sometimes not. It's indirectly related to our consciousness, but the pyramid didn't appear by some pharoah imaginging in his mind that he wanted the great pyramid to appear. That may be how it got started, but it took laborers (or aliens according to some here) to stack the stones and actually build the pyramid.

So did "consciousness manifest reality" in the pyramid example? It depends on exactly what you mean by that. That an idea was turned into an immense physical structure is obvious. But if the Pharoah asked this structure to be built and then many workers start building it because they see him as a god, exactly where is the need to invoke quantum mechanics for that to happen? I can just about guarantee you that anytime someone invokes quantum mechanics in this context, it is a form of quantum "woo". In fact this article explains how it usually seems to be abused:

Quantum woo

The reason for quantum woo is the almost mystical status of quantum mechanics in the collective imagination: almost nobody knows what it actually is, but it's definitely extremely hard science about very awesome stuff....all it takes to make something appear to be based on Hard Science™ is spouting a little bit of vague technobabble about quantum stuff. The logical process runs something like this:

I want magic to exist.
I don't understand quantum.
Therefore, quantum could mean magic exists.

a reply to: Arbitrageur


I agree with your analysis that there must be a volume reduction in this instance to get a pressure rise. But we do need to support the normal force due to the weight somehow. The sidewalls can help some, but when you have a flat they don't fully hold up the vehicle in my experience. So my conclusion is the complete answer probably involves both a pressure change (from a volume change) and some sidewall support of the normal force. That would reduce my back-of-the envelope calculation, but I don't know how much. I can certainly see how it might drop the .25 to under .1 if the side walls are stiff enough to be substantially load bearing.

My main point was to clarify the pounds per square inch vs pounds issue. I thought that might be helpful.

Also I think those cheap donut spares that are out there deform quite a bit more easily. I helped my son with a flat and I didn't know if that donut we put on would make it to the garage as it started deforming very badly. So I think they have minimal sidewall support. It might be interesting if your friend could check out the pressures on a really cheap donut. Maybe the gauge could see things change on one of them.

a reply to: Arbitrageur

thanks for the reply

I can see why there is much confusion.

You said about the age of the universe and the age of the earth and hence why consciousness didnt maniest the universe because humans didnt exist until well into the teenage years of the universe
but that is based on the assumption that consciousness is human alone
it seems more likley that its not human and that consciousness is the universe itself so looking for consciousness inside a human is like looking for the person inside a radio when it broadcasts.

I will contine to read more books and see what I find, the best physics books Ive read so far personally are , Quantum and Wholeness and the implicate order , both really good reads

a reply to: delbertlarson
Yes I agree there was some confusion in the original question about pounds versus pounds per square inch and your post was helpful in making that distinction, so thanks.

originally posted by: sapien82
it seems more likley that its not human and that consciousness is the universe itself so looking for consciousness inside a human is like looking for the person inside a radio when it broadcasts.

I would say this is a severe case of dictionary abuse. I just referred to every definition I could find in the dictionary for consciousness, and I can see how all of them could apply to humans in one way or another, but I don't really see how any of them apply to the universe. Unless we can agree on what consciousness means, we will be unable to communicate about it in any meaningful way.

So how do you define consciousness, and does your definition match the dictionary? If it doesn't, we're done.
If your definition does match the dictionary definition, what characteristics of the universe have you observed which fit the dictionary definition of consciousness?

originally posted by: Arbitrageur

originally posted by: Hyperboles
Question.
Why does a pendulum slow down at the equator as compared to the poles?

I think it would be difficult to measure with a pendulum so I have to ask, did someone measure this with a pendulum? We can calculate what the slowdown would be and that could definitely be measured using atomic clocks which can make much more accurate measurements than a pendulum. In fact NIST has measured a time difference between two very accurate clocks where one was moving only a few meters per second with respect to the other, and because of the Earth's rotation motion at the equator is in the ballpark of 1000 mph relative to the poles. It's a prediction of relativity that clocks will run slower when they are in motion relative to the observer, and this has been confirmed with atomic clocks.

what i mean is ,both the observer and the pendulum is in the same reference plane at the 2 respective locations and the observer is measuring the period of the pendulum with a mechanical stop watch at both the locations

a reply to: Arbitrageur

the state of being aware and responsive to ones surroundings

I cant confirm awareness , but it is certainly responsive to itself , everything in it reacts to each other

I wanted to ask you this question because I've read this , this morning

qauntum teleportation

It gives a brief explanation of entanglement , but Im trying to understand how particles can become entangled , are they connected via a higher dimension that we simply cannot measure hence the instantaneous results between entangled parties ?

Like how does the phenomenon occur to begin with , or is that just simply not understood at this time.

I think I'll need to read those papers from 1935

I find it interesting that we had animism and idealism before we had the scientific method
why is it that humans sought the mind over matter world first before the matter over mind world

ahhh just a thought.

originally posted by: Hyperboles
Question.

First you ask this:

Why does a pendulum slow down at the equator as compared to the poles?

Then you say this:

originally posted by: Hyperboles
what i mean is ,both the observer and the pendulum is in the same reference plane at the 2 respective locations and the observer is measuring the period of the pendulum with a mechanical stop watch at both the locations

I don't know what you mean by "reference plane". The surface of the Earth is not a plane. Flat earthers may think so but we've taken pictures of the Earth from space and it looks like a big ball, with a curved surface. So a location at the equator is one reference frame and a location at the pole is another reference frame as reference frames are applied in the theory of relativity.

I tried to search for anybody measuring pendulums at the poles and I found this but they were just verifying the Earth rotated and at what rate it rotated. I didn't find where they compared the pendulum period to any others but if you can post a link about some research like that (what you're talking about) I'd find it interesting. As I said I expect the passage of time to be different in those different reference frames, but it would be far easier to measure that with atomic clocks than with a pendulum and a stop watch. The passage of time would be different due to both gravitational and velocity differences.

originally posted by: sapien82
a reply to: Arbitrageur

the state of being aware and responsive to ones surroundings

I cant confirm awareness , but it is certainly responsive to itself , everything in it reacts to each other

So you drop a bowling ball from the leaning tower of Pisa, and it makes a little dent in the grount where it strikes the Earth, thus using your definition the earth or universe is conscious because it reacted to the ball dropping by forming a crater?

Using that definition, if you have an unconscious man, and stab him in the chest and remove the knife, the blood spurting out of his chest shows he is responsive to his surroundings, therefore he's conscious, even though he's unconscious? Do you see the problem with this definition? Consciousness might be hard to define but I don't think you're trying very hard.

I wanted to ask you this question because I've read this , this morning

qauntum teleportation

It gives a brief explanation of entanglement , but Im trying to understand how particles can become entangled , are they connected via a higher dimension that we simply cannot measure hence the instantaneous results between entangled parties ?

Like how does the phenomenon occur to begin with , or is that just simply not understood at this time.

I think I'll need to read those papers from 1935

Did you watch the video in the opening post by Sean Carroll? He gives a decent overview of the issues involved with the answer to that question. Our math works well making predictions, but there are several options for the reality underlying the math. His favorite interpretation is the Everett or "Many worlds" interpretation, which of course is not what we teach in school, which is the Copenhagen interpretation. There are several others, like deBroglie-Bohm which is fairly interesting.

originally posted by: sapien82
I find it interesting that we had animism and idealism before we had the scientific method
why is it that humans sought the mind over matter world first before the matter over mind world

ahhh just a thought.

Using the scientific method to understand the world, we suspect that the the rain that happened after the virgin that was sacrificed to appease the rain god many centuries ago probably would have happened even if the virgin hadn't been sacrified, so for virgins who don't want to die for no reason, the scientific method is a good thing. Our understanding of the world was much more limited before it and in some cases, it was wrong. We've also had some wrong ideas since the scientific method began but it was the scientific method which helped us discover those problems.

originally posted by: Arbitrageur

originally posted by: Hyperboles
Question.

Using that definition, if you have an unconscious man, and stab him in the chest and remove the knife, the blood spurting out of his chest shows he is responsive to his surroundings, therefore he's conscious, even though he's unconscious? Do you see the problem with this definition? Consciousness might be hard to define but I don't think you're trying very hard.

Well I suppose it just reinforces the idea that consciousness is not inside the human body when you get KO'd like someone pulling the plug to the wifi receiver .

Thanks for the reply on the quantum teleportation , I couldnt view the video at work , but I read the article , I'll check out the other theories and see whats what!

I like to make time to read things so this will be good reading , I even read the maths bits just in case one day it means something to me haha.

I have to say though , maybe the virgins wanted to be sacrificed to the rain god to stop or start the rain that came and went !

it is a mad world we live in , I mean many worlds theory how mad is that



Aww the best

originally posted by: sapien82

originally posted by: Arbitrageur

originally posted by: Hyperboles
Question.

Using that definition, if you have an unconscious man, and stab him in the chest and remove the knife, the blood spurting out of his chest shows he is responsive to his surroundings, therefore he's conscious, even though he's unconscious? Do you see the problem with this definition? Consciousness might be hard to define but I don't think you're trying very hard.

Well I suppose it just reinforces the idea that consciousness is not inside the human body when you get KO'd like someone pulling the plug to the wifi receiver .

I think the issue here is the definition of "human consciousness" as opposed to a person being conscious or unconscious (i.e., "awake" or "physically unresponsive").

A person could be unconscious -- say knocked out cold or in a comatose state -- but the brain (or "human consciousness, if you want) will still react to some forms of stimuli, such as getting stabbed, in a "human consciousness" sort of way. That is, the brain will still do much of what it does in reaction to its body getting stabbed, even when the person is in a coma.

...And that "human consciousness" could still all be contained within the brain and still only be a physical product of brain chemistry and brain cells.

originally posted by: sapien82
Well I suppose it just reinforces the idea that consciousness is not inside the human body when you get KO'd like someone pulling the plug to the wifi receiver .

The facts suggest just the opposite. Loss of consciousness can occur after injury to the brain, which points not only to correlation but also causation. A person with a healthy brain is more likely to be conscious than a person with a damaged brain, where unconsciousness can and sometimes does occur as a result of brain injury. So this points to not only consciousness having origins in the body, but also a specific part of the body...the brain.

Thanks for the reply on the quantum teleportation , I couldnt view the video at work , but I read the article , I'll check out the other theories and see whats what!

You're welcome. Maybe you can watch it at home.