Science questions not worth a thread I: I'm a moron!

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I'm curious why there are 6 significant figures in this question :dubious:

Surely a rocky asteroid of that magnitude will not be spherical down to a meter in elevation!
Oops? :mischief:

Just take it as the maximum width of it, that is, the parts of the surface that are the absolute furthest from each other. ;)
 
Why are objects in mirror so much closer than they appear?

Oh, objects in mirrors exist?

Takes all his money and puts it in front of the mirror

I have no clue, they should seem [Distance from mirror to object] + [Distance from mirror to retina] away.
 
Why are objects in mirror so much closer than they appear?

For a flat mirror they are not. However, the side-view mirror on the passenger side of cars is usually curved to extend the field of view so that you can actually see anything useful with it. Extending the field of view obviously has to come at the price of demagnification: The more objects you want to fit on a given surface, the smaller the objects have to become. So the objects as seen in such a side-view mirror appear smaller than if they were seen in a flat mirror. The brain interprets that as the objects being further away than they actually are.
 
As in the passenger-size mirror? I believe it's slightly concave (as opposed to the driver's side which is flat) and as such, it makes objects appear smaller. So in your driver's-side mirror an object 25 feet away looks X size, but in the passenger-side mirror, the same object at the same distance looks smaller. Your brain interprets that as further distance.

Ahem.
 
Question about electromagnetic pulses. I was reading a book a while ago and it talked about an electromagnetic pulse being used to destroy electronics. I looked it up and apparently, an electromagnetic pulse is simply a burst of electromagnetic radiation. From what I understand, electromagnetic radiation is simply light (visible light, x-rays, gamma rays, microwaves, etc). So from what I understand, an electromagnetic pulse is kind of like the flash on a camera (except that it is probably a different wavelength than what a human can see and probably far more intense)? If so, how on earth does this wipe out electronic devices without also killing people or destroying non-electronic devices?
I understand that a solar flare or a nuclear bomb being detonated at high altitude can create an electromagnetic pulse (one knocked out a bunch of lights in Hawaii during the cold war back when the US tested a bomb a bit too close to the islands), and that modern electronic equipment would be much more vulnerable to an EMP than an older system, but how does an EMP destroy electronics in the first place? Thanks
 
Electromagnetic radiation is an oscillating electric and magnetic field. This field can induce a voltage in an electric circuit and if the field is strong enough the circuit will be damaged by overvoltage or overcurrent. This is especially bad if the resonance frequency of the circuit matches the frequency of the electromagnetic radiation. Most electric circuits will have such resonances and because an EMP is broadband, there will be frequency components of the pulse that match these resonances.

Modern electronics are usually designed to run at low voltages and low power and are densely packed. Therefore the breakdown voltages and currents are much lower, so they are more susceptible to an EMP.

Biological systems or mechanical devices are usually much more resistant to high voltages. If you wear the wrong shoes and walk on a carpet you can easily get charged to a level very dangerous to electronics without any danger to yourself (except for a small shock when you touch something conductive). Additionally, there are usually no good resonances, so there is no danger of a resonantly driven circuit.
 
I think he means that an EMP is going to go out across a broad area of frequencies. And so it will effect many different electronic circuits. Too many to have any reasonable hope that any given piece of equipment will avoid damage.
 
I figured that was what he meant, it's just that broadband is a horrible word to use to try and describe that.

Why? That is how one would express "covering a large range of the spectrum" in optics. I do not see why it should be a horrible word in this context.
 
Broadband works fine. I didn't trip over your usage of it.
 
What is the mechanism called? used in animals (term used loosely) that when they loose an a limb grow back. Could this be applied to humans(in the future)?

EMP, I know they are real, but how do you make one happen outside of nuclear weapons?
 
What is the mechanism called? used in animals (term used loosely) that when they loose an a limb grow back. Could this be applied to humans(in the future)?

EMP, I know they are real, but how do you make one happen outside of nuclear weapons?

EMP is just some kind of radiation. Technically you make one every time you flick on a wall switch, but it's not a significant vector to most of our macroscale activities. Electrical waves and magnetic waves are irrevocably linked by co propagation. Where one is, the other is.

Think of the EMP in the weapon form as a very big light bulb, or a temporary circuit discharge optimized for electromagnetic radiation. That it is very large and unexpected in the region is all that makes it any different than any other electronics or electromagnetic phenomena we have.

Probably some natural astronomical or geological "storm" could perform an EMP effect of some scale.
 
What is the mechanism called? used in animals (term used loosely) that when they loose an a limb grow back. Could this be applied to humans(in the future)?

Regeneration. I think it will eventually be possible in humans.
 
EMP, I know they are real, but how do you make one happen outside of nuclear weapons?

Apart from the methods GoodGame described, I believe solar wind and other solar phenomena produce what can be described as an EMP. A solar flare in the 19th century famously allowed telegraphs to be operated even though their power source had been shut down by that same flare.
 
How do I observe the Venus transit with my small refracting telescope? It's small, but the lid for the aperture has a smaller lid at the center that can be taken off. I don't have any filters, so the only thing I can do is use it to project the sunlight on a flat surface. Really, my concern is, will the sunlight damage the eyepiece? Or would it be better to remove the eyepiece for the projection method?
 
Sunlight has an intensity of about 0.1 W/cm^2, which is almost nothing in optics. Even at 100x magnification, this is not that much. So I wouldn't worry about damaging the eyepiece. But the magnification might be too large for a good projection, so it might work better without it.
 
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