Recent comments in /f/askscience

the_geth t1_je6roq1 wrote

The long answer is long, but in short: No.
Google "carbon dioxide capture via air filters" for instance, and you will see that the problem lies in efficiency: You need a huge amount of energy to make a dent into what has been released already, and that energy is likely carbon intensive in the first place.

The scale is insane too: see here how they talk about a hypothetic future plant capturing 1 million ton of CO2 per year. It would still take 32 000 of those hypothetic plants to cancel out the world's CO2 emissions for 2021 (32 billion tons), not accounting for CO2 produced by the construction of those plants and most importantly not accounting for the CO2 produced by the energy needed to capture and store this CO2.
Also, those plants requires chemicals which may be a problem in itself.

It takes about 10Giga joules per ton of CO2 to treat and store the CO2.
So, based on the 32 billion tons of CO2 figure, it would take 320 billion gigajoules to treat all the CO2 emitted by other sources.
That's about ~89 000 terawatt-hours, which is about 3 to 4 times the total consumption of electricity of the entire world in a year.

So... nope.

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ronnyhugo t1_je6p4hn wrote

The eye actually evolved four separate occasions (at least). Because at every point in making an eye, you gain an advantage. And that is how the lens also evolves.

IIRC the book "Selfish Gene" goes into this. Great audio book that's worth listening to a few times.

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QuentaAman t1_je6oy0t wrote

You can shield against electric fields by using a faraday Cage. This is above highschool level but the wuick answer is that, using maxwells equations, you find the the electric potential inside such a cage is exactly 0 no matter what charges there may be outside the cage. And since the electric field is the gradient of the potential (again, sorry if that's too advanced for you) it is also 0.

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loki130 t1_je6ndgd wrote

The distortion of spacetime in the black hole is such that it’s geometrically possible to move outwards (or even remain still). It would be like trying to go north from the north pole.

Also the thing about not having to reach escape velocity is only sort of true. If you start near a planet and start moving at less than your current escape velocity, you could indeed escape the planet, but escape velocity drops as you get further from the planet, so you would have to cross that escape velocity at some point.

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the_geth t1_je6knrq wrote

About ultra-massive block holes like this one or TON 618 which is even bigger, at 66 billion solar masses:
Since there are so, so big and it would take ages to travel to their centers from the event horizon itself , would it be possible to be inside the event horizon in orbit?
For how long, in theory (I imagine that orbit wouldn't be stable)?
Last but not least, would you be able to see the singularity from there?

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katinla t1_je6jpna wrote

Considering the extreme temperatures, I'm having a hard time trying to conceive any way of getting even close to the Sun.

If the idea is mining helium from extraterrestrial sources, I'd rather point at the gas giants. You get manageable temperatures and much lower delta-vs (which translates directly into fuel requirements).

But still, this would be an extremely expensive (i.e. unrealistic) mission, not only in terms of money, but also in terms of resources such as materials and fuel. Consider that a round trip to an outer planet does not cost twice as much as sending a probe to stay there, it costs a lot more because fuel requirements grow exponentially with delta-v. This is in addition to the fuel required to lift off from a giant planet.

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someon332 t1_je6e7r8 wrote

Why can’t anything escape from inside a black hole? I hear that it’s because “escape velocity is equal to the speed of light” but an object dosent have to exceed the escape velocity to escape the objects gravitational pull. I’m wondering if it’s a physics problem (in that some physical law is stopping us) or an engineering problem (in that it’s just difficult to imagine a system that could output enough energy to counteract the pull).

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