pavelcherepan

Yes, you can use something like PuTTY. It's multi-platform, do it should work on most systems.

https://en.wikipedia.org/wiki/PuTTY

12 hours ago, Itoero said:

There is no evidence for this, it's the idea from a smart man a long time ago.

Just about two years ago LIGO has detected gravitational waves from the merger of back holes that acted as black holes should in GR. And since then there were several more detections that match predictions very well. Seems like a good evidence that they exist and act as GR predicts.

12 hours ago, Itoero said:

Not everything in GR is correct.

And what would that be?

Simulations look great. I wonder why accretion disks end up being so very torus-like, rather than disks. I thought that due to conservation of momentum, they would flatten out. I need to read the study in detail.

On 1/11/2018 at 5:06 AM, Willshikabob said:

How much fuel would it take to sustain standard Earth-like gravity (excluding gradient and launch) for 1000 days in space

If you want to constantly accelerate in your direction of travel the fuel requirements will be immense, it's not plausible as it will require a significant portion of all matter in Solar System as fuel. On the other hand if you go for the spinning arrangement then in ideal case only energy you'd need to expend is the amount you need to start the spin. After that since you'd be travelling in vacuum, it should keep going for extremely long period of time, and by that I mean millennia.

10 hours ago, DrP said:

I think you need to look for materials with a high specific heat capacity.  

I'd like to amend this by adding that you need some material with high specific heat capacity and low heat conductivity, therefore it will be able to store a lot of heat energy, but will be reluctant to give it away.

Nice, I learned a new term here- thermal effusivity and looking at some numbers, DrP was right at recommending water or if you want something more solid things like PVC, wood, silicone or natural rubber can do the job. Neoprene is also good.

https://thermtest.com/materials-database

11 hours ago, Strange said:

Light can also be polarised by passing through certain types of crystals or other materials (e.g. a polarising filter as used in sunglasses).

Or even simply reflecting off of any reflective surface.

8 hours ago, Moontanman said:

Super habitable would mean a larger planet around smaller stars that the sun, vast oceans with huge shallow seas and land surface contained in large archipelagos, islands, and chains of islands. The atmosphere would be denser and possibly contain significantly larger amounts of Hydrogen Sulfide, Ammonia, CO2, CO, Methane and others due to larger numbers of life forms that produce them and volcanoes that also produce them.

The planet Pandora orbiting the gas giant Polyphemus would be an example of this in fiction. 

Why would a larger planet be better than Earth-sized or smaller for habitability? And why is denser atmosphere good?

Also a lot of what you described depends on plate tectonics, but as of now there's no consensus as to why or how plate tectonics started on Earth and why it didn't on Mars or Venus, for example. 

2 minutes ago, Raider5678 said:

I'm one of those people who doesn't think rocket science will ever become routine.

I certainly hope it does 

6 minutes ago, Raider5678 said:

So different rocket fuels only affect exhaust velocity, which then, in turn, affects the ISP of the rocket?

In a nutshell, yes. There are a lot of other considerations in play, such as TWR that's possible to reasonably achieve, resulting engine mass or how easy it is to store fuel/oxidant or whether or not fuel is extremely poisonous and/or radioactive. 

On 12/17/2017 at 9:34 PM, GeeKay said:

Yes, I understand now. In other words the only 'practical' way for an object to decelerate while passing through an intense gravitational field would depend on powered means, not inertial. Moreover, the fact that the incoming object is moving at 0.01c relative to a given mass would (I should imagine) rule out all variations of power assist - this insofar that the proper velocities of nearly all stars aren't remotely relativistic, that's to say within local frames.

Many thanks for clearing up this matter for me.

Not specifically. You can use gravity of one object to alter your velocity with respect to the third object. For example, you have a space ship coming back from Mars towards Earth. You can use lunar gravity assist to slow it down a little with respect to Earth rest frame. But in Moon FoR craft will have the same velocity at same distances as it approaches and recedes.

It's the same as you can use Jupiter gravity assist, this time to increase your velocity wrt Sun rest frame, but then again, velocity of your craft (unless powered assist is used) will be the same at same distances from Jupiter as you approach and leave.

12 minutes ago, Raider5678 said:

Wait, doesn't fuel efficiency play a role in it?

In rocketry Specific Impulse of an engine can be used as a proxy for "fuel efficiency", but it directly depends on the exhaust velocity. The higher the velocity of stuff that comes out of the back end, the less of it you need to use to achieve the same delta-v. And exhaust velocity is already there in the rocket equation.

On 12/29/2017 at 6:08 PM, Sensei said:

At lower pressure (or lack of it) water boils at lower (e.g. room) temperature.

Sure, definitely all the moisture on the surface layers of the skin will quickly boil off. This was in fact experienced by an unfortunate astronaut trainee, who got locked in a vacuum chamber and depressurized to almost the vacuum conditions. He distinctly recalled (before passing out) that saliva was boiling in his mouth.

On the other hand, abdominal cavity and skull, for example, are very much air tight and could potentially maintain some pressure inside. 

P.S. Happy New Year everyone!

9 hours ago, mistermack said:

Then, the 100 watts radiative cooling figure climbs rapidly, and eventually reaches equality with the heating figure.

Yep, so what would that equilibrium point be? Intuition tells me it's higher than body temperature, but my intuition is too often wrong.

14 hours ago, MigL said:

Water readily 'boils' in a vacuum, so yes, the body's outer layers would freeze and start 'cracking', leading to more moisture loss, until the whole body would freeze/dehydrate.

Ok, but after that, will it remain frozen? Consider now negligible radiative heat loss, most of the water already gone, and the body spends slightly more than half the time in the sun.

So, suppose an unlucky astronaut went out of the airlock of ISS naked for whatever reason. Let's say it was because of "space dementia"

Obviously, they are going to pass out in a few seconds and die within a couple minutes, but what would happen with the body? It would spend slightly more than half of the time in light compared to the dark, because of Earth's atmosphere bending the light. Based on what I could find, black body radiation of human body would be around 100 W, whereas the solar radiation would give in excess of 1500 W. Only part of those 1500 W would be in IR, but still the amount of infrared should be sufficient to more than compensate for the radiative heat loss.

One thing I'm concerned is whether it would have enough time to freeze over while going through Earth shadow for ~40 minutes. 

https://en.wikipedia.org/wiki/Black-body_radiation#Human-body_emission

Couldn't find economics sub forum so I'll put it here instead. So, if you want to buy or sell a share on a share market you would normally have to pay a premium to a broker who would make the sale on your behalf. Is there any general rule as to how long it takes for the combined cost of premiums to exceed the price of the share itself? I guess, it's a bit vague since the price of the share is not constant, but so are the premiums...

Not considering derivatives like options and such for the sake of this question.

On 12/17/2017 at 4:34 PM, Abcdefghij said:

1)would more UVA penetrate into my apartment than if they faced the right way?

No.

On 12/17/2017 at 4:34 PM, Abcdefghij said:

2) IF UVA does penetrate, would it then bounce off the the walls and hit the blackout shades (which are facing the wrong way and which allowed UVA im) and then reflect back onto my skin again - so then my skin would be hit by twice as much UVA than it would if I had no blackout shades at all?

No again. UV would be absorbed by your walls and furniture and very little would bounce.

6 minutes ago, Butch said:

Saw that coming... I don't have a lot of faith in the strong and weak nuclear forces... I fear the momentum of qm has us jumping ahead of ourselves.

13 minutes ago, Sensei said:

Oh yeah, this is already Speculations. I guess, you're looking for "alternative science" explanations. How about elves?

4 hours ago, spientist said:

Is it possible to somehow lower the minimum temperature of an ordinary fridge to at least as low as the temperature of dry ice ?  If not without modifying it, might it be done by replacing the fridge's liquid from Freon to alcohol, or some other liquid or gas ?

Just as John said, depending on what you would consider acceptable modification. You can add some insulation, a second and maybe third refrigerant cycle in a cascade and change HFC-134a to some other refrigerant with lower boiling temperature.

6 minutes ago, Butch said:

What binds a neutral particle to a proton

Strong nuclear force.

To me the biggest cringe I get whenever I hear someone utter something along the lines of: "...an asteroid killed dinosaurs...". People just use it like a mantra, while there were a lot of different things at work in KT extinction, but everyone just talks about the damned asteroid.

40 minutes ago, Butch said:

Matter in a star is in the form of ionized gas. Nuclei can be fused but what is preventing the decay of the neutron in such an environment.

Ionised gas only means that electrons are stripped away from the nucleus. For as long as neutrons are bound to protons in a nucleus, they are very much stable.

9 hours ago, dimreepr said:

This thread suggests that it's more nuanced than an individual versus a group dynamic.

Which part are you referring to?

2 hours ago, interested said:

No politician does anything for nothing, there is always method in the madness. What does he hope to gain in destabilizing the region?

You put it as if the actual goal was to de-stabilise the region. And if it were the case, you'd be right. Trump has little to gain from such a stunt. On the other hand, it's more likely that it is just a collateral damage from an attempt to gain more approval back in the US.

1 hour ago, MigL said:

A boson is not necessarily an elementary particle.
It is a particle ( or compound particle ) which obeys Bose-Einstein statistics.

Thanks. I was not aware of this. Now it makes much more sense.

Below I've linked a video from PBS Space Time, which is a really nice science channel and usually presents very well researched and narrated videos. In this video, though, one thing got me confused - the video is about absolute zero and at one point when the presenter is talking about Bose-Einstein condensates he says this: "There's only one substance is known to produce superfluid for conditions possible in the lab. And that substance is helium. In particular, helium-4. Helium-4 has a total spin of 0 which makes it a boson...".

This is confusing to me. Can we really talk about an atom as if it were an elementary particle?

https://youtu.be/OvgZqGxF3eo?t=3m57s