Interesting Science Stuff Thread

[Easy Bakes 253]

So the cat froze to death?

Anyway.

it still don't mean the kelvin scale is wrong. they just have not found the true temperature were 0K means there is no energy or its at its lowest energy state.

[astronelson 339]

Absolute zero may not be so absolute.

But the article's explanation of how that works doesn't really make sense...

The theory behind negative kelvin is well understood.

Basically...

Some systems have a maximum amount of energy they can hold. As you approach this maximum they actually start to become more ordered, rather than less - adding energy makes the entropy decrease. This is because the number of ways you can arrange the places energy isn't is very small.

For a system in which entropy (S) is dependent on energy (E), you can define temperature (T) through this: 1/T = dS/dE (the inverse of temperature is the rate of change of entropy with respect to energy). Since an increase in energy causes a decrease in entropy, dS/dE is negative, so 1/T is negative, so T must be negative.

What they have done here is create an arrangement that contains almost the maximum amount of energy it can hold, so it has a negative temperature.

[A Nonny Moose 8,261]

Sounds like conditions for a big bang.

[astronelson 339]

Quite the opposite - the arrangement is stable. There shall be no large explosions nor new universes spawned out of this.

The interesting thing about this is that it is stable for arbitrarily many atoms in the system, so it could theoretically be made quite large indeed.

[A Nonny Moose 8,261]

And what useful applications are there?

[Duke87 1,070]

Some systems have a maximum amount of energy they can hold. As you approach this maximum they actually start to become more ordered, rather than less - adding energy makes the entropy decrease. This is because the number of ways you can arrange the places energy isn't is very small.

For a system in which entropy (S) is dependent on energy (E), you can define temperature (T) through this: 1/T = dS/dE (the inverse of temperature is the rate of change of entropy with respect to energy). Since an increase in energy causes a decrease in entropy, dS/dE is negative, so 1/T is negative, so T must be negative.

What they have done here is create an arrangement that contains almost the maximum amount of energy it can hold, so it has a negative temperature.

So, you've created a negative temperature by adding energy. Huh.

But then, is it cold?

[astronelson 339]

And what useful applications are there?

Does it need any? At this point it is impossible to say what it will be used for, but someone will probably come up with something sometime. And two days later it will gain a military application.

So, you've created a negative temperature by adding energy. Huh.

But then, is it cold?

No - it's hotter than anything else in existence.

[A Nonny Moose 8,261]

Knowledge for its own sake is fine, but somehow all that research has to find a source of funds, so yes, everything needs an engineering effort to do something practical with new science sooner or later. I prefer sooner.

Now you've said cold really is hot if you look at it closely enough. What kind of binding force holds this together?

[Ocram's Razr 963]

This whole negative Kelvin stuff is confusing to me.

--Ocram

[astronelson 339]

Now you've said cold really is hot if you look at it closely enough. What kind of binding force holds this together?

No, I've said negative Kelvin is hot and not cold. Heat will flow out of it if brought into contact with something with a positive temperature.

You don't get to negative Kelvin through absolute zero - you get there through infinity Kelvin. The temperature increases as you add energy. At some point adding more energy does not change the entropy, dS/dE=0 so 1/T=0, so T=infinity. After this point adding energy decreases the entropy, so T starts off being very negative and approaches zero from the other side.

The binding force would be the electromagnetic force, since gravity is too weak and atoms are too big to interact through the nuclear forces. This can be verified by the fact that lasers and magnetic fields are electromagnetic phenomena, and that's what's being changed in the experiment.

[A Nonny Moose 8,261]

This is starting to sound like an exercise in conformal geometry where all circles are really straight lines though the point at infinity where you can invert one into a strait line and vice versa. We all know that dividing by zero or "infinity" breaks the arithmetic machine, so one wonders if this is meta-physics.

[Cobraroll 138]

More like an asymptote, like lim(X -> 0) Y = (1/X). For very small X above zero, Y is huge and positive. For very small X below zero, Y is huge and negative. It's just a matter of crossing the "zero line" in which Y is not defined.

[A Nonny Moose 8,261]

More like an asymptote, like lim(X -> 0) Y = (1/X). For very small X above zero, Y is huge and positive. For very small X below zero, Y is huge and negative. It's just a matter of crossing the "zero line" in which Y is not defined.

You might say that. It is mathematical fiction, as is all mathematics. We use it because it works.

On the other hand, consider the lowly tachyon. What is its mass when it is moving at 3 x 10¹⁰ + 0.00001 cm/sec? If relativity is correct, this little gem will be very heavy as it passes backwards through time.

[astronelson 339]

It's a lot simpler if you stop thinking about temperature as what you are familiar with, and start thinking about it as a convenient way to describe the relationship between entropy and energy.

Then you see that the figure of temperature is just a convenient way of writing your answer, and the actual important thing that you work with is the inverse of temperature, which is continuous over the range of energies you have, starts off very positive at low energies, and becomes very negative at high energies. In the middle range it passes through zero.

When you convert this to a temperature you hit a problem, because dividing by zero is not allowed mathematically, and you thus get a rapidly increasing temperature, "passing through infinity" and suddenly becoming a very negative number, still increasing.

But the inverse of temperature is just steadily decreasing, passing through zero, and continuing on its downward path. Nothing special happens at (aside from the fact that entropy in the system starts decreasing).

Eventually the amount of energy in the system is very high, the entropy very low, and the rate of change of entropy with respect to energy very negative. So the inverse of temperature (the important thing) is very negative. So the temperature is negative and very close to zero kelvin.

[Easy Bakes 253]

Tomaoto genome sequenced

Tomato tomato

[A Nonny Moose 8,261]

Neat. So now we can look forward to gene-spliced fruit on the dinner table. Gregor Mendel would be blown away by this. See what happens when you play with your beans?

[A Nonny Moose 8,261]

Some scientists put some backbone into it.

The sum of man's knowledge is getting very much larger as we speak. Yesterday I watched the end of a program on galactic bubbles of dark matter, and today this little gem.

[A Nonny Moose 8,261]

Development of graphene.

Highlights western corporate failures to launch.

"Industry is more worried not about what can be done, but what competitors are doing - they're afraid of losing the race.

The National Graphene Institute is to be built in Manchester at a cost of £61m

"There is a huge gap between academia and industry and this gap has broadened during the last few decades after the end of Cold War, so I try as much as I can to reach to the industry.

"This is what has happened in last 30-40 years. We killed famous labs like Bell labs. Companies have slimmed down so they can no longer afford top research institutes. If something is happening in Korea it's because Samsung have an institute - there is nothing like that in this country.

"They can't see beyond a 10-year horizon and graphene is beyond this horizon."

[Haljackey 17,272]

After 23 Years Of Work Scientists Have Finally Obtained Liquid Water From An Ancient Antarctic Lake

http://www.businessinsider.com/lake-vostok-water-ice-obtained-2013-1

[A Nonny Moose 8,261]

^ This sample will be biologically interesting at the very least. Since it was a frozen core in the end, many life forms may not have survived.

[A Nonny Moose 8,261]

Mars.

Taking more baby steps. It wouldn't do to break the drill because the repair man is a long way away. They are finally getting down to so really interesting stuff in Areology (martian geology).

This is probably the greatest achievement of science in the current era. Pretty much the sum of our technology is riding in that rover.

[Zukunftstraume 220]

Usually just have this site (linked below) be my homepage and end up reading through the two or so posted articles daily.

The Daily Galaxy -- Great Discoveries Channel: Sci, Space, Tech

[blade2k5 1,523]

Usually just have this site (linked below) be my homepage and end up reading through the two or so posted articles daily.

The Daily Galaxy -- Great Discoveries Channel: Sci, Space, Tech

 

Interesting web site.  Thanks for the link.

[A Nonny Moose 8,261]

The first mammal?

 

Descended from apes?  Seems we are descended from rats.

[Cobraroll 138]

^That entirely depends on your time perspective. It would be just as valid to say that we descended from humans, from apes or from amoeba as to say we descend from rats.

[A Nonny Moose 8,261]

Yes, but not from yeasts, which are flora not fauna.

[Bdub01 201]

So I hear an asteroid is coming so close to earth it will be closer than some satellites. My question is if its that close how come the earths gravitational pull is not bringing it into the atmosphere to rain down death and destruction or at the very least pull it into our orbit and make it a really small moon?

[astronelson 339]

 

So I hear an asteroid is coming so close to earth it will be closer than some satellites. My question is if its that close how come the earths gravitational pull is not bringing it into the atmosphere to rain down death and destruction or at the very least pull it into our orbit and make it a really small moon?

 

 

It won't become a small moon or be pulled into the Earth because there's nothing to slow it down below escape velocity. Since it started outside the Earth's gravitational sphere of influence, it has to be travelling above escape velocity relative to Earth as it passes by.

 

The energy of an orbit is the sum of the orbiting object's kinetic energy and its gravitational potential energy. Gravitational potential energy is zero at an infinite distance away from what the object is orbiting and only decreases. A closed orbit happens when the energy of the orbit is negative.

 

Now, the least amount of kinetic energy an object can have is zero. If it's coming from interplanetary space, it effectively started "at infinity" relative to Earth. At best it had zero kinetic energy there, more likely it had a lot more. As it falls towards Earth the total energy stays constant, so the energy of the orbit must be at least zero, and is probably higher, so the orbit cannot be closed, so no capture can happen.

 

There is a way an asteroid could be captured by the Earth, though - if, when coming in, it was travelling slowly enough, passed sufficiently close to and in front of the Moon, it could transfer some of its energy (from our point of view) to the Moon, travel slower relative to us and enter a closed orbit. The Moon would gain some energy and be boosted into a slightly higher orbit. This wouldn't be stable, though. The asteroid would keep gravitationally interacting with the Moon and eventually either get kicked out again or crash into something.

[Bdub01 201]

Ok thx for the explanation. Cause I was wondering bout it since the Shoemaker-Levy comet was pulled apart by Jupiter's gravitational pull before its pieces slammed into the planet.

[Jim14409 448]

Thought we needed a place to discuss interesting science things.

Ill go 1st.

Taken by the Venus Express Spacecraft over the southern polar region of venus.The below image sequence taken in infrared light and digitally compressed, darker areas correspond to higher temperatures and hence lower regions of Venus' atmosphere. Looks very similar to the one that exists on Saturn.

 

Are you certain those are space shots? Except for the lack of color they look almost identical to the pictures from my colonoscopy a few years back. That was not close to Venus but was close to...

 

EDIT: I didn't look at the date on this post. Thought it was a new thread since I had not seen it before.

  Edited February 12, 2013 by Jim14409