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Physics, Astronomy & Cosmology / How do galaxies keep a stable size?

« on: 23/05/2019 11:35:49 »

Peter has this cosmic query:

How can each and every galaxy, given their multiplicity of sizes and shapes,exist in a finely-tuned dynamic equilibrium with the expansion of space such that no individual galaxy expands or contracts?

Can anyone expand on an answer?

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Chemistry / What makes that can-y taste in canned soup?

« on: 22/05/2019 12:09:20 »

Mike has this tasty question:

I'm originally from the Dominican Republic, but I emigrated to the US. When I came here, I tried my first canned soup ever. I immediately noticed that cann-y taste. Over the years I've kept wondering the reason for this. Recently, I tried to make soups that taste as close to a canned soup as possible. I canned 4 batches in mason jars, and to take into account for the can itself I made one can with no metal, I put a piece of steel  in one can, a piece of aluminium in another can, and two pieces of steel and aluminium in another can. While the cans don't taste great, they don't have that characteristic cann-y taste. Is there a reason for this? (Also, I took into account preservatives).

Can anyone help?

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The Environment / Do boat wakes cause erosion?

« on: 21/05/2019 10:06:39 »

Paul made waves in our inbox with this question:

The Chinese and others are talking about making use of a northern sea route to Europe. If this becomes very busy, will not the wakes of large vessels aggravate the erosion of the ice around the Arctic?

He also had some ideas about how we could modify boat wakes:

Would hovercraft would have a lesser effect, but then it would take massive power to elevate a supertanker or other fully laden vessel, so that is probably not a sensible question. If the vessels had sausage-like floats on either side of them which could deflect the wake back against the vessel, or would that just increase the friction of the vessel and necessitate stronger motors?

The other thing is that the wake would be generated by the propellors at the aft of the vessel, so that negates the suggestion of sausage like floats. How about having two main propellors aft which cause the wake to not spread outwards but be thrust together, out of phase so they neutralise the wake?

What are your thoughts?

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Physics, Astronomy & Cosmology / How would a supernova affect Earth?

« on: 21/05/2019 09:54:13 »

Jeff sent us this question:

How close to Earth would a supernova need to be in order to affect life here? What effects would a supernova have?

Can anyone shed some light on it for him?

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Physiology & Medicine / What is the ideal temperature to wash your hands?

« on: 25/04/2019 15:37:46 »

Rob has a curious question on his hands:

I was interested in what the ideal temperature was to wash your hands in. Assuming you washed your hands with soap, there are a couple of conflicting factors in my mind. We wash our hands to remove bugs essentially. Warm water feels nice and would help dissolve dirt/bugs and rinse them away and perhaps helps dries hands as well (evaporating the water, good to dry hands). Hot water would burn your hands, so that's no good. The main confliction I think is that warm water be a nicer temperature for bugs to grow on your hands. Colder water would discourage their growth. I think warmer water is the answer (as hot as you can handle). There are other factors like comfort, blood flow in your hands, health factors, that are also important apart from washing away bugs.

Can anyone clean this up for him?