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Chemistry / Re: What is the difference between one mole of CH4 and one molecule of CH4?

« on: Today at 02:05:51 »

Just to add to Bored Chemists neat explanation, I suspect part of your confusion arose from the similarity of the two words:
mole and molecule

The reason for the similarity is that mole was derived from the German mol, itself an abbreviation for Molekulargewicht, molecular weight, in English.

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Plant Sciences, Zoology & Evolution / Re: Are there fossilised giraffes specimens?

« on: 09/02/2018 06:51:55 »

Wikipedia list twenty three giraffid genera, some of which contain multiple species. More than I expected, but that just reveals my ignorance about the state of Tertiary vertebrate palaeontology.

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Physics, Astronomy & Cosmology / Re: Is there a difference between spacetime and placetime?

« on: 09/02/2018 06:10:15 »

My original question sprang from a conversation I recently had with a friend.  I must admit to only being able to define placetime conceptually.  For that I am sorry.  Let me rephrase...

Can an object remain stationary in spacetime?  Is there such a thing as an absolute position in spacetime?

and

If it were possible to remain stationary, would you "see" time passing, and be unaffected by its passage?

There is no absolute position in spacetime, hence it is only possible to remain stationary relative to another object. That being the case your second question has no meaning.

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General Science / Re: Where is all the Oxygen hiding in the Solar System?

« on: 12/11/2017 21:01:07 »

Oxygen is the third most abundant element in the cosmos, after hydrogen and helium. So far I know you can't breath on Mars and the Moon. So where is all the oxygen hiding?

Given that it is the second most abundant element making up the Earth I don't think we should describe it as hiding. The bulk of the Earth's mass is present in the silicate mantle that, as pointed out by evan_au, contains abundant oxygen. It's almost as abundant, to a % or two, as iron.

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Geology, Palaeontology & Archaeology / Re: Could pyramids have been terraformed?

« on: 05/07/2016 07:54:37 »

Alex, you have an active imagination and that is commendable. Unrestrained active imaginations are of great value when creating works of fiction. However, when dealing with the non-fiction world, imagination must  be constrained by reality. Unfortunately your imaginative thoughts conflict with many facts established by tens of thousands of scientists over decades and centuries. I encourage you to do a little study of what is known and use your imagination to build on a solid foundation in future.

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Geology, Palaeontology & Archaeology / Re: Does this look like a meteor strike?

« on: 22/04/2016 10:59:23 »

Thank you. I was looking at the wrong thing. I shall try to take a closer look at this over the weekend. My suspicion is that this is just coincidental curved features. But then many of the now well established astroblemes were explained away in a similar manner.

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Technology / Re: Can information be obtained by brainwaves as an alternative to torture

« on: 03/04/2016 17:01:13 »

Given the ineffectiveness of torture for extracting reliable information, I can confidently state current technology to "read minds" can match it in every regard.

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Physics, Astronomy & Cosmology / Re: Why are the planets such different sizes - and in no particular size sequence?

« on: 08/03/2016 15:47:16 »

By what physics does the cloud collapse?

Gravity, though pressure waves from proximal, or embedded supernovae may trigger the collapse.

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Physics, Astronomy & Cosmology / Re: Why are the planets such different sizes - and in no particular size sequence?

« on: 08/03/2016 11:38:13 »

The answer is complex, but this is a simplified version.

Planets form from a collapsing cloud of gas and dust. They are almost incidental, since most of the mass goes into the proto-star. The rest of the dust and gas form a flat disc around the star in which particles condense and coalesce.

As the star warms up the temperature in the disc prohibits ices from forming in the inner part of the system, so that rocky planets are formed. Further out ices can condense and coat any rocky cores that are formed. Stellar activity also drives gas away from the inner part of the system (and eventually all of it), but the outer rocky cores can attract some of this gas.

Thus we end up with small rocky planets in the inner system and large gaseous and icy planets with rocky cores in the outer system. During this process planets can move around a lot as a consequence of interaction with the disc and mutual gravitational effects. Some are lost into the parent star, some are ejected from the system and some swap places.

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Physics, Astronomy & Cosmology / Re: Is there an answer in smoke and dust without there being a question?

« on: 31/12/2015 07:30:54 »

What are the effects of density, size, geometry and surface area on settling rates of small particles in a gaseous medium?