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[wierd]

Anyone been keeping up on that whole EMdrive thing? Has it been debunked yet, or is it still going strong?

I want my reactionless drives~...

I wouldn't be too optimistic, since you know, any true reactionless drive kinda violates the law of the conservation of momentum.

A quick glance at the wikipedia page for it reveals that there has yet to be anything published in peer-reviewed journals, nor has anyone replicated the results under standards high enough for the scientific community or been willing to share their "results" in peer-reviewed stuff yet.

Theoretically, I dont see a compelling reason why the emdrive couldnt work, other than violating high level conceptual models.

This is because the method of operation relies on virtual particle interaction, rather than "Real" particle interaction.  Virtual particle interactions are already used quite successfully in commercial applications, such as Near Field Communication.  This is because the near field of EM emissions is dominated by virtual particles, while the far field is dominated by real particles. There is enough total particle flux in the near field for NFC to work, but past the near field, partice flux is just too low to overcome the noise floor.  Substantial amounts of energy can be communicated across the near field, which is how antenna coupling happens.

http://iopscience.iop.org/0295-5075/76/2/189

Since some virtual particles can have both charge like characteristics, and mass-like characteristics, then the emdrive could convey some limited change in vector by acceleration of such particles (say, virtual electrons) in the short space of the resonant cavity. Since the particles are not "real", they dont have any persistence. This means that they cant shed the energy imparted to them by the interaction, by interacting with the far wall of the cavity. They cease existing by then.

This change will be very tiny, and hard to measure. Higher frequency modes with greater attenuation over distance would probably be more efficient under this conceptual framework.

I would say that most reputable scientists are fearful of touching the emdrive with any seriousness, because it goes against conventional wisdom with such violence.  Scientists are very much in danger of losing funding sources for appearing to be disreputable. The "reputation" game is very toxic to actual science; which is the actual pursuit of empirical truths.  One needs look no further than the ruined careers of the people who looked at the theory behind cold fusion and lent support there, to see how toxic such efforts can be. More recent, and IMO, more telling, was the CERN "FTL Neutrino signal" a few years back.  The researchers wanted help finding their source of error-- Instead, they got black eyes from the popular press who misunderstood why they were reporting their findings, and what they were actually wanting from other scientists.

To me, a researcher that reports reactionless thrust is looking for others to reproduce the work, and find errors in the setup.  That's not how the rest of the world, and sadly, funding sources, view it however.  The more successful scientists are aware of this more worldly underside to science, and avoid dangerous subjects.  Reactionless thrust is a dangerous subject.  I would thus take the lack of peer reviewed study with a grain of salt.

[Eagleon]

EDIT: Lagslayer, if you're using your argument, literally nothing in physics is in a closed system.

It's a valid argument! Let's abandon entropy and create semioticcentropalpy.

[ShadowHammer]

I understand the heat death.
Is it perhaps possible for heat energy to convert into another type of energy.
Like a heat eating spacewhale?

Does time exsist? I understand it and can see a watches hand moving but is time an actual force?

Spoiler (click to show/hide)

Sorry people.
I lived on a farm until I was 12 and then left highschool at 15.
Im not terribly book smart. I feel like I cant comunicate properly, like I cant translate my thinking into readable words. It can drive me crazy.

To answer the first question here, yes, heat can and is often converted directly into other forms of energy. A thermocouple takes heat and converts it directly into electricity.
This leads me to a question: if a gas has more entropy than a liquid, and you use a thermocouple to cool a gas down to the condensation point, and then proceed to use the resultant electricity to charge a battery, haven't you just decreased total entropy?
Note: I may not (read: don't) really understand how entropy works.

Well, the thing is that it requires a heat difference. In other words, one part must be hotter than the other- as the energy moves from hot to cold, it produces an electric charge. However, the temperature is still equalizing- ergo, entropy is increasing.

EDIT: Lagslayer, if you're using your argument, literally nothing in physics is in a closed system.

Ah, I see. Makes sense.
New question: why don't refrigerators decrease entropy?

[Lagslayer]

EDIT: Lagslayer, if you're using your argument, literally nothing in physics is in a closed system.

It's a valid argument! Let's abandon entropy and create semioticcentropalpy.

If breaking the glass increases it's entropy, then putting it back together must lower it's entropy. But since the second law is being thrown around so much, according to it, the total entropy of the universe can only increase. Since the entropy of the glass alone can oscillate back and forth, talking about it in the context of this conversation is meaningless. It was a terrible example and should have never been introduced.

New question: why don't refrigerators decrease entropy?

It doesn't remove heat, it simple redistributes it. All that heat is re deposited outside the refrigerator. Combined with the less than 100% efficiency of the redistribution system, it creates more heat than there was to begin with.

[wierd]

Not closed. Electrical energy is supplied.  Energy is entering the system, and being used to transport heat energy into a lower entropy state.

2nd law applies to closed systems. The same reason why life is still able to flourish on earth-- The sun is providing energy.

The more curious thing to ask about, is the mysterious "thermal transistor" created a few years ago.
http://www.sciencedaily.com/releases/2011/04/110403141333.htm

[Eagleon]

It was a terrible example and should have never been introduced.

My bad.

[Angle]

To answer the first question here, yes, heat can and is often converted directly into other forms of energy. A thermocouple takes heat and converts it directly into electricity.
This leads me to a question: if a gas has more entropy than a liquid, and you use a thermocouple to cool a gas down to the condensation point, and then proceed to use the resultant electricity to charge a battery, haven't you just decreased total entropy?
Note: I may not (read: don't) really understand how entropy works.

Well, Sort of. Thermoucouples work based on heat differentials, which mean they're of no use combating entropy. You're still moving energy from higher concentrations to lower concentrations, you're just getting a little electricity out of it.

[i2amroy]

If breaking the glass increases it's entropy, then putting it back together must lower it's entropy. But since the second law is being thrown around so much, according to it, the total entropy of the universe can only increase. Since the entropy of the glass alone can oscillate back and forth, talking about it in the context of this conversation is meaningless. It was a terrible example and should have never been introduced.

The glass example works fine as long as you include the forces that act on it in your system. If you utilize a force to break the glass, some of that kinetic energy is converted to other less useful types of energy (like heat or sound). As such it's impossible to put the glass back together again with the same forces, since it would require you to convert those less useful types of energy like heat back into kinetic energy at 100% efficiency.

So yeah, if you are just looking at the glass pane then it's a bad example, but if you look at both the glass pane and the energy required to shatter it then it works just fine.

To answer the first question here, yes, heat can and is often converted directly into other forms of energy. A thermocouple takes heat and converts it directly into electricity.
This leads me to a question: if a gas has more entropy than a liquid, and you use a thermocouple to cool a gas down to the condensation point, and then proceed to use the resultant electricity to charge a battery, haven't you just decreased total entropy?
Note: I may not (read: don't) really understand how entropy works.

Well, Sort of. Thermoucouples work based on heat differentials, which mean they're of no use combating entropy. You're still moving energy from higher concentrations to lower concentrations, you're just getting a little electricity out of it.

Pretty much. While the total entropy in the (electricity + gas + liquid) < total entropy in the (gas+liquid), it would still be greater than the entropy of the (hot gas+cool liquid), since you can't get 100% efficiency out of the process.

[Descan]

... Wait, putting the glass back together requires energy, either machinery, or muscle power, and if you want to do it properly, you need to re-melt the glass.

All three require energy, and all three have waste heat. Friction, heating element heat, muscle heat.

The entropy embodied in the glass itself is lowered, sure. But it's not a closed system, it doesn't magically come together again, it needs external energy inputted, and the entropy of that whole interacting system rises because of it.

[i2amroy]

Yeah, the idea is that even if you could somehow capture 100% of the leftover energy after the glass is shattered it wouldn't be able to put the glass back together again, because you have to pay a toll for everything you do.

Of course for a lot of these discussions you really want to be talking in terms of enthalpy rather than entropy.

[ShadowHammer]

New question: why don't refrigerators decrease entropy?

It doesn't remove heat, it simple redistributes it. All that heat is re deposited outside the refrigerator. Combined with the less than 100% efficiency of the redistribution system, it creates more heat than there was to begin with.

I know that it doesn't remove heat, but it does (indirectly) move heat from a lower concentration to a higher. If entropy increases when heat differentials equalize, doesn't it decrease when the differential is increased?
I realize that at no point in a refrigerator's cycle does heat directly flow in the 'wrong' direction, but the end result is still an increased temperature difference between the inside of the fridge and the outside.

[Descan]

If you think entropy is decreasing in a system, then your system isn't big enough. You need to account for where ALL the heat and energy is going/coming, not just what interests you.

In this case, you need to account for the electricity/energy required to power the refrigerator.

[Angle]

Also, entropy isn't about heat, entropy is about energy. This includes the energy in electricity you spent to do all that moving.

[Descan]

Aye. I fixed my post to account for that, too.

[Cryxis, Prince of Doom]

Would there be any I'll effects on the sun if a ball of iron the size of Saturn crashed into it at relatively slow speed?