Science

Backdraft said:
I'd be interested to see some of the research/projects you guys are working on in your respective fields.
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Working on making editing/simulating/viewing graphical models easier, more efficient, more colorful, ... Stand back, I'm [doing] science!
 
Cowboy said:
You people are aguing about how to get people in different solar systhems.......sjees.

Howbout coming up with something to send all the damn hippies to the moon?
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Why would you come into a science thread and bitch about science being discussed?
 
I found you, Hawking Radiation!

http://www.technologyreview.com/blog/arxiv/25805/
For some time now, astronomers have been scanning the heavens looking for signs of Hawking radiation. So far, they've come up with zilch.

Today, it looks as if they've been beaten to the punch by a group of physicists who say they've created Hawking radiation in their lab. These guys reckon they can produce Hawking radiation in a repeatable unambiguous way, finally confirming Hawking's prediction. Here's how they did it.

Physicists have long realised that on the smallest scale, space is filled with a bubbling melee of particles leaping in and out of existence. These particles form as particle-antiparticle pairs and rapidly annihilate, returning their energy to the vacuum.

Hawking's prediction came from thinking about what might happen to particle pairs that form at the edge of a black hole. He realised that if one of the pair were to cross the event horizon, it could never return. But its partner on the other side would be free to go.

To an observer it would look as if the black hole were producing a constant stream of quantum particles, which became known as Hawking radiation.

Since then, other physicists have pointed out that black holes aren't the only place where event horizons can form. Any medium in which waves travel can support an event horizon and in theory, it should be possible to see Hawking radiation in these media too.

Today, Franco Belgiorno at the University of Milan and a few buddies say they've produced Hawking radiation by firing an intense laser pulse through a so-called nonlinear material, that is one in which the light itself changes the refractive index of the medium.

As the pulse moves through the material, so too does the change in refractive index, creating a kind of bow wave in which the refractive index is much higher than the surrounding material.

This increase in refractive index causes any light heading into it to slow down. "By choosing appropriate conditions, it is possible to bring the light waves to a standstill," say Belgiono and co. This creates a horizon beyond which light cannot penetrate, what physicists call a white hole event horizon, the inverse of a black hole.

White holes aren't so different to black holes (in fact Hawking argues that they are formally equivalent). And it's not hard to imagine what happens to particle pairs that form at this type of horizon. If one of the pair crosses the horizon, it can make no headway and so becomes trapped. The other is free to go. So the horizon ought to look as if it is generating quantum particles.

It is this radiation that Belgiorno and co say they've seen by watching from the side as a high power infrared laser pulse ploughs through a lump of fused silica. Their pulse has frequency of 1055nm but the light they see emitted at right angles has a wavelength of around 850nm.

Of course, the big question is whether the emitted light is generated by some other mechanism such Cerenkov radiation, scattering or, in particular, fluorescence which is the hardest to rule out.

However, Belgiorno and pals say they can rule out all these sources of light for the radiation they see. In particular, they that the fluorescent light is well characterised and that it differs in various significant ways from the emissions they see. Therefore, they must be seeing Hawking radiation, they conclude.

That's an astounding claim and one that many physicists will want to pour over before popping any champagne corks.

Why is it important? One reason is that Hawking radiation is the only known a way in which black holes can evaporate and so a proof of its existence will have profound effects for cosmology and the way the universe will end.

And now that it's been observed once, expect a rash of other announcemetns as researchers race to repeat the result.
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That's genuinely exciting. Go Italians!

In other news, fucking white holes, how do they work?
 
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^That's really cool.
 
Equal rights in science - first Black Holes, now White Holes... I wonder when we will see Women Holes... :p
 
narf said:
Equal rights in science - first Black Holes, now White Holes... I wonder when we will see Women Holes... :p
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I could post something in reply to that, but I think it would be considered NSFW :p
 
narf said:
Equal rights in science - first Black Holes, now White Holes... I wonder when we will see Women Holes... :p
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One that produces brown matter as opposed to dark matter, or the other that ....... nope, stopping there. Safest for all really.
 
MadCat360 said:
I found you, Hawking Radiation!

http://www.technologyreview.com/blog/arxiv/25805/




That's genuinely exciting. Go Italians!

In other news, fucking white holes, how do they work?
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You have to be careful when reading those articles. A lot of times there filled with what's called "pop science"-which tends to oversimplify and candy coat what is being researched at hand. For instance, you will never be able to observe Hawking radiation emanating from a massive black hole until the surrounding black hole temperature drops to temperatures extremely close to 0 Kelvin (something 0.0000005K). Currently, the overall temperature of the universe is approximately 3 Kelvin. I'm assuming when the article mentions about astronomers trying to observe Hawking radiation, they are mentioning about strange applications to black holes called micro black holes. They have yet to be observed.

The experiment is otherwise facinating. If Hawking radiation is verified, and there is good reason it should exist, that indeed would be the greatest finds in science since Einstein's General Relativity and quantum theory. The cleverness of this experiment is beyond genius. If it works, Hawking will be awarded the Nobel Prize. This experiment is being highly talked about in scientific circles.

As far as white holes, Hawking even states in his books that white holes, if they did exist, would not be stable. White holes, just like black holes, have an accumalation of so much matter they would collapse almost immediately from formation. The white hole is, essentially, the opposite end of the black hole. If matter goes in the black hole, matter comes out the white hole. Thus, to observe one in space would be impossible (that's according to Hawking and the physics dealing with gravitational physics).
 
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Thanks czelaya.

I was reading a bit about neutrinos, and it said that a neutrino is about 45 Electron Volts, being a measurement of size (or energy?). I was wondering, what are some of the other particle sizes in eV?
 
MadCat360 said:
I was reading a bit about neutrinos, and it said that a neutrino is about 45 Electron Volts, being a measurement of size (or energy?). I was wondering, what are some of the other particle sizes in eV?
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eV is a unit of energy, essentially it's Joule on a different scale. 1 eV is about 1,602176487?10^?19 J, or almost nothing :lol:
Since we all know energy and mass are essentially equivalent (thanks, Einstein), you could also use a unit of energy to describe a mass.

If you're wondering about the energy of a particle just as a result of its mass withough being in motion, an electrons' mass results in an energy of 0.5MeV, for a proton it's 0.9GeV.
 
Wow, that's a rather gigantic difference in size. Quite staggering actually. Thanks.
 
Yeah. A Proton weighs nothing, an Electron weighs nothing divided by 2000, and a Neutrino weighs nothing divided by 2000 divided by 10000 (if your 45eV is correct). Expressed as mass that's 0.000000000000000000000000000000000080235kg for the Neutrino, 0.00000000000000000000000000008915kg for the Electron, and 0.0000000000000000000000000016047kg for the Proton.

:lmao:


PS: A quick googling/wikipediaing shows that 50/45eV is an old theoretical upper bound, if Neutrinos were any heavier the universe would collapse. Newer experiments suggest anything from under 2eV to under 0.28eV.
 
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Just an anal addition here:

The mass is written as MeV/c^2. Since the rest energy is E = mc^2, the mass is just E / c^2. E is energy measured in eV or joules.

So saying that something has a mass of 6 eV (for example) is not entirely correct, but I think if you said that to any physicist he'd/she'd understand.
 
:nod: I know, just trying to keep things simple. The c?? is just a constant anyways :lol: including its unit. Leaving off constants makes life much easier, see big-O complexity notations.
 
:D

Now here's a question for people: What minimum size (radius) would the Earth have to be compressed to in order to make it a black hole? The answer may astound you once you think about it. E-cookie for the person that gets the correct answer.

Bonus question: How much would you have to squeeze the sun down to to do the same?
 
Earth - 3 ft?
Sun - Earth size?

and yes I could've looked it up, but I wanna play the game.
 
Nope. You're sorta thinking right though with one of them.
 
Both should be smaller. Especially compressing the Sun to Earth's size is by far not enough. The required density is enormous.
 
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