Recent comments in /f/askscience

Aarakocra t1_j69xwe4 wrote

Reply to In the absence of cosmic radiation, would an object placed in space eventually cool to absolute zero? by IHatrMakingUsernames

Yes-ish. The concept of the heat death of the universe is the end result of that idea. The stars cool off and we are left with bodies that slowly cool down until things reach absolute zero and the universe is “dead”.

But that plays out over a long time. The body loses heat through the standard mechanisms of radiation (excitement at the atomic level results in photons jumping off), convection (fluid passes over the body and takes heat as it leaves), and conduction (something is in contact with the body and heat transfers through it). We would only be talking about radiation here, because this object is alone. Radiation happens based on how much activity is happening down at the atomic level, so the rate of cooling is going to decrease as the temperature decreases. However the radiation will happen at some point, so the body will eventually drop to absolute zero. We have a nonzero loss of energy, so as long as we have zero gain in energy it has to eventually hit zero.

At least assuming it is a true absence of cosmic radiation. This only holds as long as there is no input energy transfer taking place. Even a star far away could produce enough energy to keep the body from reaching absolute zero. The assumption of zero gain in energy is hard to pull off.

Also fun fact, you couldn’t observe the object at absolute zero either! As far as I know, we can’t measure such an object without giving back some energy.

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ThriceFive t1_j69xgc0 wrote

Reply to can gemstones be melted into a gradient? by Acceptable_Shift_247

I just saw a YouTube video about lab made opals which would let you do two different colors of opal. Fusing two stones from a gem cutter might be your best result or create a stone w epoxy resin and powdered gemstones to whatever mix and ratio you want. I think your idea is romantic but don’t try for the impossible and miss the focus of the gift on pursuit of your quest

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Otherwise-Way-1176 t1_j69x7ta wrote

Reply to comment by [deleted] in why don’t dear, elk, moose, wolves, etc get frostbite in winter? by blind_ninja_guy

>This is partly due to their metabolic rate, which is much lower in cold temperatures than it is in higher temperatures.

Are you sure this is accurate?

A lower metabolic rate would mean that the animal is generating less heat. Which presumably would confer lower cold tolerance than a high metabolic rate.

Hibernating animals do have a lower metabolic rate. But they compensate with more insulating fur, and by selecting sheltered places to hibernate. The lowered metabolism doesn’t help avoid frostbite.

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QuantumCakeIsALie t1_j69wxbt wrote

Reply to comment by AssCakesMcGee in In the absence of cosmic radiation, would an object placed in space eventually cool to absolute zero? by IHatrMakingUsernames

It's a very conventional way to define temperature in thermodynamics/physics.

Fun fact, you could create infinite energy if you could create a Carnot thermodynamical cycle that crosses + and - temperatures. That was a big issue with the concept of negative temperatures, until someone proved that it's impossible to create such a cycle to begin with.

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team-tree-syndicate t1_j69wmmc wrote

Reply to Has a new animal species evolved since mankind’s existence? by coding_ac

Not sure if I would count this as an evolved species, but growing up in Alaska grasshoppers we're always green. When I moved to a different state and a big city, I noticed that there were tons of grasshoppers.

Big difference though, these one were grey or sand colored. They blended in perfectly with average concrete, asphalt, and sand. They blended in so well that it's almost impossible to spot them at work unless you see their shadow moving.

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FogeltheVogel t1_j69weaz wrote

Reply to comment by ManyThingsLittleTime in Is there an upper limit to structure size in a vacuum? Could a sufficiently advanced civilisation build a galaxy sized structure in space or would it become too massive and collapse in on itself? by CubanHermes

A few planets is a tiny fraction of the mass of a start system. How exactly is that an example of a galaxy sized structure needing multiple galaxies worth of material?

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