# Tag Info

110

The Higgs field (note it is the field that is important here, not the Higgs boson itself, which is just a ripple in the Higgs field) gives particles mass in the same sense that the strong force gives the proton mass (context: $99\%$ of the mass of the proton comes not from the mass of its constituent quarks, but from the fact that roughly speaking the quarks ...

71

Summary: I find a formula for the diameter of a bubble large enough to support one human and plug in known values to get $d=400\,{\rm m}$. I'll have a quantitative stab at the answer to the question of how large an air bubble has to be for the carbon dioxide concentration to be in a breathable steady state, whilst a human is continuously producing carbon ...

42

The problem was solved by a certain Albert Einstein, who is probably not unknown to users of this web site. Actually he also calculated the viscosity of particle dispersions (Einstein (1906). A. Ann. Phys. 19: 289, or section 2 in this PD). Presumably he only did special relativity after getting bored with fluid dynamics. Anyhow, it's because the motion of ...

41

From a purely temperature point of view, not human perceived level of hotness, it is better to point the fan outward. This is because the fan motor will dissipate some heat, and when the air is blown outwards, this heat goes outside. This is all assuming the room has enough ventillation cracks and the like that the pressure inside is still effectively the ...

39

It's easy to get mixed up between time and the flow of time, and I think you've done this in your question. Take time first: since 1905 we describe any event as a spacetime point and label it with four co-ordinates ($t$, $x$, $y$, $z$). Saying that time doesn't exist means we can ignore the time co-ordinate and label everything by just it's spatial co-...

37

Your understanding is correct. There cannot be a geostationary satellite at the poles, basically because it would have to be at rest, which cannot happen as it would get pulled by the earth's gravity and eventually crash to the surface. In fact, there cannot be a geostationary satellite anywhere else, except above the equator(in an equatorial orbit). ...

34

This was a reference to the apparent measurement that neutrinos travel faster than light. FTL travel can be used to travel back in time (though the procedure for doing so is somewhat involved). Sadly the apparent superluminal speed turned out to be due to experimental errors: a fibre optic cable attached improperly, which caused the apparently faster-than-...

32

The concept of blowing your own sail really does have to do with conservation of momentum. In that very episode of Mythbusters you speak of, the sail was removed, the fan was spun around and the ship/boat was propelled forward much faster than with the fan facing into the sail (i.e. figure (1) is much faster than figure (2)). The reason is really quite ...

31

If the question is interpreted as why don't atoms and other bound systems expand the answer is that the general expansion of space cannot do continuous work against the electromagnetic force that holds an atom together or any other force that holds a bound system together. However the accelerating expansion of the universe can exert a small "constant" ...

31

Maybe I should turn the comment to an answer. The physics of the situation is the same as when one can upturn a water glass with the water not falling out. The atmospheric pressure keeps it in. There exist the diving bells with open bottoms . As they are lowered the pressure in the air goes up to balance the water pressure, because the lower in the water ...

29

You can check this yourself using this very long link which will give you a list of Hawking's work that has been published in refereed journals, ordered by the number of times they have been cited in other papers (a measure of how influential they are on other scientists). This is a way of providing at least some non-opinion based answer to this question. ...

28

There is an additional loss of energy when driving through puddles on a wet road, because the tire treads have to exert work in order to eject water. One way to look at it is that the keeps trying to glide on top of the water, but is continuously sinking into it to meet the pavement, which is equivalent to driving slightly uphill.

25

The accepted answer by udiboy is completely right; however theoretically it is not only gravity that acts on a satellite, but also light pressure from the Sun and Earth. Given a sufficiently light and large solar sail (implausible at the current technological level), it is possible to counteract acceleration due to gravity and enter a totally non-Keplerian ...

25

The reason fluids flow off your hand while solids don't, is that fluids can change shape and solids can't. The molecules in a fluid want to stay together, but they don't care about the shape they're in, so gravity will cause them to spread out over your hand and flow off the sides. Solids can't change shape so they just stay on top off your hand, held in ...

25

Yes coherent light is required. The important thing to realize is that coherent light is not something that is magically created by lasers. Sunlight is somewhat coherent and it's easy to make it as coherent as you like. What do people mean when they say "coherent light"? Well, it can be a few different things, but the relevant criteria in this context are: ...

23

There are lots of questions here that I will try to answer, hopefully I'll get to them all... Creature Comforts It's hard to "just fly higher" when you consider passenger planes. Supersonic military aircraft like the SR-71 do fly ridiculously high. It's service ceiling is 85,000 feet! But, it has the advantage that it doesn't need to keep anybody but the ...

22

From Hacker News https://news.ycombinator.com/item?id=6253263 This is a far more interesting question than it might seem at first glance, and it deserves some attention because it tells us something fundamental and wonderful and just bloody awesome about the universe. But I don't know how to tell the story succinctly. So I'm going to do that thing I do. I ...

22

No, the water would not be sucked up. Even if you take a pipe with vacuum, closed the top and dipped the open end of that pipe in water then the water would only rise 10 meters. After that the 'pull' from your vacuum is in balance with the force of gravity acting on a 10 meter water column. Maybe needless to say: The top of the atmosphere is way higher ...

21

You would feel weightless if every part of your body of mass $m$ would be subject to an upward force equal to $m$ times the local gravitational acceleration $g$. Such an exact part-by-part cancellation is not going to happen via diamagnetic levitation as utilized on the frog in your example. Not only does this levitation couple according to magnetic ...

20

There's a very common misconception that the Big Bang happened at a point like a bomb going off. It doesn't help that almost ever TV documentary on the subject represents the Big Bang in this way. Explaining what actually happened is hard without going into the Maths, but here's an explanation I gave taken from (of all places) the Science Fiction Stack ...

19

This is to summarize some of the excellent comments made previously by participants of this discussion, and to emphasize a couple of important points. 1) The original question implied that gas exchange between the bubble and surrounding water may be enough to sustain indefinitely breathing organisms inside. However this does not seem to be possible ...

19

Albert Einstein is often credited (erroneously, it seems) with saying The only reason for time is so that everything doesn't happen at once. and John Wheeler added Space is what prevents everything from happening to me! Now, those quotes may sound silly and self-referential, but they are meant to draw you attention to something very, very basic. ...

19

Short answer: do not take it literally, without further context. In order to understand the Higgs boson's role in the Standard model, it is necessary to take a closer look at the framework in which we describe elementary particles: quantum field theory. In this approach, particles are described as excitations of fields that spans all spacetime. The ground ...

19

Method 1: Foucault Pendulum As user Rob asks, what is wrong with a short Foucault pendulum? There is a problem, but it can be overcome inexpensively, but with some DIY effort at home. The problem is that, by dint of imperfections in the suspending fibre and bob, no pendulum will swing in a plane even if the Earth were not rotating. Instead, the bob will make ...

18

As with many discussions about string theory, it is sometimes good to recall some reality: It was over 50 years ago that the Higgs mechanism was proposed. Compared to fully-fledged theories such as string theory, the Higgs mechanism is a tiny add-on to the observed standard model (as it was then). It took 50 years for experiment to get to the point of ...

17

Ask yourself this: why doesn't the vacuum of space just suck away our atmosphere? The reason is because of the earth's gravity, which pulls on the gas envelope around the planet to keep it in place. The phenomenon we call 'air pressure' is also the result of this. The tube will only fill until its contents are being pulled down by gravity with the same ...

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