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mistermack last won the day on January 6

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  1. why do two objects fall same rate in a vacuum

    My own picture of this is pretty simple. So it may be wrong, but here goes. If you have two identical steel balls, and hold them a metre apart, and drop them from an upstairs window, you would expect them to land simultaneously. They are identical in weight and size, so of course they would. Do the same thing with them a half metre apart, and the same thing happens. Then 10 cm apart. Then 1 cm apart. They both still fall at the same speed. Even 1 mm apart, they both fall at the same speed. So why would you expect anything different if they were 0 mm apart? ie touching. Neither is going to fall faster or slower than the other, and hence affect the speed. If you glued them together, that's not going to change. So you've established that an object twice the size and weight of a single ball will fall at the same speed as a single ball.
  2. cleaning a spill

    I'm sure it's surface tension that keeps the water away from the fabric for a period. When you put a dry cloth into water, you can often see little bubbles of air shining on the surface of the cloth, showing that the water isn't in close contact to the cloth. You could test it, by comparing how pure water mops up, to how water with a bit of detergent mops up. I'm guessing the detergent solution would soak up much quicker.
  3. What has the Earth got to do with Electricity

    Very wise. It's hard to overstate just how lethal it can be if you get it wrong. When I was three, ( sixty odd years ago ) I was nearly killed by a basic single bar electric fire. I was holding the bar when my elder brother plugged it in. You simply can't let go. All the gripping muscles in your hand contract, so you can't release it. I remember it vividly to this day. I was jumping around like a fish, and every time I hit the floor I got a tremendous shock. Maybe a three year old heart is hard to stop, but I was badly burned. If I had got a full grip on the handle of the freezer that time, I would definitely have died.
  4. What has the Earth got to do with Electricity

    One practical point about the Earthing on electrical gadgets, is that it can be a killer, or a life saver, depending on whether it's properly fitted. I once touched the handle of a freezer with the tip of my little finger and got a huge shock of electricity, I was in bare feet on a stone floor. My friend had wired the plug carelessly, without securely pinching the cable with the gripping mechanism that's at the entrance to all plugs. Someone else had pulled on the plug to make it reach the power point. The earth wire had pulled out from it's terminal, and was just resting against the live wire. So, the whole chassis of the freezer was live, just waiting for someone to touch it. It was lucky my finger only just brushed the handle. If I had got a proper grip, I would have definitely been killed. That gripping mechanism in a plug is vital, but a lot of people don't give it much thought. On the subject of step potential, did you know that the safest thing to do, if lightning is about to strike, is to stand on one leg? People might laugh, but it's true. If your feet are wide apart, the charge can go up one leg and down the other. The further apart your feet are, the greater the voltage drop, and so the stronger the current. That's why cattle are more likely to die in a lightning strike than a human. The distance from the front feet to the back ones is so much more. A flamingo on one leg should be ok.
  5. Air humidifiers, what's the point?

    Well, assuming that it's winter, and you have to put some heat on, then a lit gas ring is more efficient. If you light a gas fire, or gas boiler, a lot of the heat and water vapour from the flame goes out through the chimney, or the vent in the wall. And you also suck in cold dryer air to replace the warm more humid air that's leaving, in many systems. My boiler is pretty new, and has a fan powered feed of outside air to the boiler to avoid that. So lighting a gas ring, even without the pan of water, is more efficient. So long as your house has a normal level of ventilation and you don't overdo it, it's safe, and it's going to cost less than lighting the boiler for the same benefit. Whether putting the pan of water on it is actually cost efficient would need a study to see what temperature people would choose as the optimum, at different levels of humidity. The simmering water would use some heat, but raise humidity. I'm simply guessing from my own experience that you would save. The other benefit in my case is that there is always an instant supply of nearly boiling water available in winter. If I set my gas boiler to the "comfort" setting, it keeps some water constantly hot, so that it can supply nearly instant hot water. That's actually quite a costly feature, as the boiler will keep cutting in and out to maintain the temperature of the reservoir 24/7. I have an instant supply nearly boiling, for washing up or cooking, which doesn't cost any extra. ( I've never liked dishwashers )
  6. Are Humans better Designers than Nature / Evolution !

    Well, the OP headline question is, are we better designers. So I'm entering into the spirit of the question. Even though I know perfectly well that evolution only give the impression of design. Well, I think it's evolved. Not in the strict biological sense obviously, but the word has a more general application. In any case, the similarities are strong. A phone needs to survive in the market place. Some fail, others succeed spectacularly. Some survive by occupying a niche. The surviving models get reproduced, with sometimes minor, sometimes major changes. The designs that fail usually go extinct. Most people would say that the phone is evolving. Even if it's not biological, and there is design involved. The design is evolving.
  7. Air humidifiers, what's the point?

    I think the way you do it makes a difference. I do what I described, I just put a pan of water on a gas ring at it's lowest setting. In a way, some of the humidity is free, it's a bye-product of burning the methane. None of the heat or water vapour generated is escaping up a chimney, or out through the boiler vent. And, if your windows do steam up, you're getting some energy back as heat. I'm sure the money involved is probably minimal. It doesn't cost much to run a gas ring on minimum. But I do prefer the feel of slightly raised humidity in winter.
  8. Air humidifiers, what's the point?

    No, that's purely my experience. I do it all the time in winter, and I can feel the difference in the room. Everyone knows that higher humidity in summer make you feel hotter than the same temperature in a dry climate. But it would be a subjective thing in winter, how much you could turn the thermostat down and feel the same comfort. Unless someone has done a study, which I'm guessing is unlikely. Obviously, you don't want humidity to be too high or you will get problems of condensation. About 55 percent RH is what commercial enterprises seem to aim at.
  9. Air humidifiers, what's the point?

    This is exactly right. The temperature at which people feel comfortable is lower, in more humid air. You might pay a bit to evaporate the water, but you save far more, by running your heating at a lower level and feeling just as comfortable. I do it all the time, just by having a pot of water just simmering on the ring of the cooker without a lid. If you close the door, it makes the room feel much warmer, even though the thermometer reads the same temperature as another room. Maybe it's because it slows the evaporation off your skin.
  10. What is a vacuum?

    Maybe you could define a vacuum as a volume of space through which light always travels in a straight line at c. Anything else is a partial vacuum. Except in a gravitational field, when it follows the curve of space time at c. Having said that, if you test it with a photon, it's no longer an absolute vacuum.
  11. Are Humans better Designers than Nature / Evolution !

    We are already beating evolution in many areas. The brain for instance. My brain is not below average, but I can't beat a computer chess machine set to a good level. And the computer can easily remember all of the moves perfectly, even ten years later. I couldn't manage that five minutes later. I don't think we will design a comparable robot, because there's not a strong market for one. (yet, anyway). But the bits of things that we design are generally better than nature. I can tell if it's hot or cold, but my car can tell the exact temperature, and convert it to other scales. So when we do design something, or some part of a thing, it's generally better. A whole human is asking a lot, but we are the freaks of the living world. In any case, it's not fair to evolution to compare in a lot of cases. What evolution has to do, is produce something that can survive and reproduce. We want something far more specific when we design something. So we don't have to design it so that it can defend itself, feed itself, fight off viruses and bacteria, successfully mate and rear it's young etc etc. We just want something that tells the time, or coverts radio waves to sound.
  12. Are Humans better Designers than Nature / Evolution !

    I think that humans are far better designers than evolution. Evolution works through failure. You produce many more young than you need, and the worst fail, and the better ones succeed. That really wouldn't do if you want to sell smart phones. In any case, the phone has gone from invention to the modern smart phone in less than 150 years. Evolution would have taken billions of years to do the same thing. Mind you, the phone has evolved, so you could say that human designers are using evolutionary principles.
  13. Is space itself conductive?

    I wouldn't think of space as a conductor. Not in the sense that copper wire is a conductor. In copper wire, the electrons don't have to physically travel from one end to the other for energy to be transmitted. The current can be transmitted by one particle pushing it's neighbour, which pushes it's neighbour, and so on, in a chain, so that energy is transmitted to the other end. In other words the copper is taking an active part in conducting the current. Whereas empty space just permits an electron to jump. It's a bit like air. I would say that air conducts sound, but I wouldn't say that air conducts a bullet. It just allows the bullet to pass, whereas it takes part in the passage of sound.
  14. Has time travel been discovered/harnessed yet?

    It wouldn't be the past, either. Right now, there is just me in this room. If I step into a time machine in an hours time and go back an hour, there will be two of us. That's obviously not THE past. It's something that looks similar but is different. Even if I replaced the version of me that was there an hour ago, it's still not the past. It's similar, but my brain and body is an hour older. I might have had a pee or poo, or a meal, so my weight wouldn't be the same. So the act of going into the past means it's NOT the past. I would say that it's not theoretically impossible to observe the past. That's what we do when we look through a telescope. Maybe it would be possible one day to look at reflections of the past on Earth, bouncing off far away bodies. Highly unlikely though. There's more chance of us being sent pictures or video of our past by aliens on far away planets. No sign of it yet though.
  15. It's not my argument against, it's one that has been put forward. I don't know enough to give an opinion on whether it's a valid point. My own feeling is that panspermia is a real and very possible candidate for the origin of life on Earth. The evidence is that life got going very quickly after the planet cooled sufficiently. If that means that life is highly likely to arise through abiogenesis, then you would expect most other world with liquid water to be harbouring some sort of life. But the same goes for panspermia. If there are seeds of life floating around in space, then other worlds should encounter them too. Either way, the odds are that life should be common in the Galaxy, given how quickly it arose on Earth. Maybe the Earth was special in some way that suited panspermia. Other planets might have too dense an atmosphere, causing everything to burn up on entry. Or too thin an atmosphere, causing everything to hit the surface at too high a speed. But anyway, if panspermia is the answer for Earth, it still needed abiogenesis to happen somewhere else.