Karthikeyan KC

Let’s get the basics straight and analyse stuff from there. Moon is a rock. A very big one indeed. For your story, you need that rock to fall on the Earth. Nice! I reckon that you want the moon to be in one piece too.

Moon is in a fairly circular orbit around the earth. It has an orbital velocity with a tangential and radial component. And To force the moon towards the earth you need to stop its linear momentum (p=mv — where m is the mass and v is the velocity). In other words, if you change the tangential velocity of the moon thereby changing the linear momentum, you can change its orbit.

Moon’s tangential velocity is roughly 3600 km/h. Mass is around 7.34×1022 kg. So if you apply a force over a time tangentially opposite, you can reduce the tangential velocity, thereby reducing the linear momentum.

And this force can be a small series of impacts applied for years—repeated asteroid, meteor, comet impacts. Or a quick one—a catastrophic impact from a huuuuge asteroid.

But impacts and collisions are tricky if you want the moon intact! The impact should have enough kinetic energy to reduce the momentum, but not too much to blast it into pieces—as an inelastic collision with kinetic energy higher than that of the moon’s gravitational binding energy will pulverize it.

So ideally the kinetic energy of the impactor should be below 3.6 x 1028 J. and should not exceed 1.2 x 1029 J (this is the gravitational binding energy of the moon). And you’d need a rock that’s equally big and dense as the moon—so you’d need an asteroid.

Similarly, if the impact was on the far side of the moon, it would increase the radial velocity component of the orbital velocity, which would then “shift” the orbit of the moon to an elliptic one—which would pass through the earth if the impact is large enough.

But the moon will probably be ripped off before it hits the earth anyway!

The physical effects after the impact

As you might know, a planet or a satellite in an elliptical orbit will have the fastest orbital speed at its perigee and the slowest at its apogee. This is due to conservation of angular momentum.

After the impact, when the moon’s orbit decays and it drifts inwards towards the earth, the physical effects of conservation of angular momentum becomes apparent. Contrary to your intuitive belief, the moon’s orbital speed would accelerate as a result of the smaller orbit and tidal forces imparted on it by the earth.

Oh, there’s more!

The moon is relatively tiny compared to earth. So when it’s close, the gravitational attraction of earth will impart even more brutal tidal forces on the moon, that when the moon gets around 9492 km (Roche limit), gravity will rip the moon into tiny chunks—causing an accretion disc around the earth. Now instead of one giant rock smashing your home, you’d be looking at millions of rock chunks smashing the earth.

But fear not! At this point, even before the moonlets hits the surface, the planet would suffer and die from other gravitational effects—tsunamis, earthquakes, volcanic activity—you get the gist!

You are right. When you put the pasta in water, the water molecules diffuse into pasta and expands it. The boiling medium is the hypotonic solution here; as the concentration of solutes is less in it compared to the cells of the pasta. Tonicity is a relative measure between two solutions, so any real world example would require two solutions with an osmotic gradient between them. In the pasta example, water is the hypotonic solution. And for the cells found in the fish gills, the salty seawater is a hypertonic solution.

I am oversimplifying this for the sake of explanation. According to relativity, any two observers in the universe who are in inertial frames must always agree about the speed of light. Always! Because it is proven to be constant in all conditions!

If you and your friend have two light clocks (A light clock measures time-based on the ticks of a light beam that’s bounced between two mirrors A and B) each and are on the ground, the time measured with those two clocks will be in sync. Of course! Because you both are in the same inertial frame and the time it takes for the light to bounced off the mirrors in your clocks will be the same.

But now let’s put you and your clock on a spaceship that can travel at half the speed of light. The spaceship now is travelling at 1/2 c and you are in it, watching the light beam bounce between A and B vertically. Everything is normal for you.

But when you fly past your friend, who is looking at you from the ground. He would see weird things happening in your clock. The light beams of your clock will not appear to travel vertically. He’d observe that the light beam in your clock takes a diagonal path (in the direction of the spaceship) as it bounces from B to A or A to B.

It is obvious that he observes it this way because the spaceship is moving too fast and the mirrors are moving along with the spaceship too. So the light’s path would be diagonal for ANY observer.

The light beam as it appears to take a diagonal path, it also appears that it has to take a longer distance to cover. Due to this longer distance, the light clock in motion now ticks slower. Therefore time in the spaceship appears to be slower for your friend. This is known as time dilation.

But for you, inside the spaceship, everything will be normal. And if you happen to observe your friend, it would appear that he is moving at 1/2 of c speed relative to you and you will observe his clock to be slower too.

Now let’s talk about ageing in the context of special relativity!

Say if you use that spaceship to travel to Proxima Centauri which is 4.2 light-years from Earth. You will be travelling at 1/2 the speed of light and it would take you 8.4 years to reach the star and another 8.4 years to come back to the Earth.

For you, the time passed is all normal – 8.4 back and forth, so 16.8 years of your life has passed. But on Earth, as time is relative, the people on Earth would’ve experienced a different time, that would have ticked faster than yours — and hence they would be a few years older than you.

To have a significant change in the time delta, you’d need to be travelling above 75% of the speed of light.

Yes, it can. They can homogeneously change between one phase to the other at a particular temperature and pressure or exist as a. Thermodynamically, this particular temperature and pressure, at which a matter occur at all the three phases (solid, liquid, and gas), is known as the triple point. The following is the phase diagram of the water showing the triple point of water 273.16 K.

So at 273.16 K and 611.65 Pa, water exists as a homogenous mixture of solid, liquid, and gaseous phases, where any minimal changes to the temperature or pressure of the system can force a rapid transition between these phases.

After experimenting with <code> and <pre>, I don’t think it’s easy to escape it. I settled with using the HTML entity for the ` grave accent. Here you go! sudo kill `cat /var/run/mysqld/mysqld.pid`. Use <code> tags to wrap it instead of ` `.

Your friend’s observation makes sense. Take a look at the absorption spectra of chlorophyll.

In the green range, the absorption rate is relatively low for the primary pigments chlorophyll b and chlorophyll a, which means the leaf reflects all the green light (the reason why plants appear green).

But in the violet and red ranges, the absorption peaks and chlorophyll benefit the most. And your 440 nm blue light happens to fall under that spectral range called the photosynthetically active radiation (400 to 500 nm and 600 to 700 nm – your optimal wavelength), which promotes photosynthesis in plants.

And to back your friend’s observation, here is a study on how the removal of green and near-UV radiation promotes plant and algae growth with visible improvements. Most of the plants have shown positive growth characteristics without the green light. For most of the plants, you could try it right from the germination phase.

But mind the fact that plants have other pigments that benefit from the green light too. Also, as the green light penetrates deep into the leaves than the red and the blue regions, it enables the chloroplasts that are away from the illuminated surface to promote photosynthesis. More on this, here and here.

To answer your first part of the question, the CO₂ barely rises in our atmosphere. The second part of the question, not likely.

To a certain extent in our atmosphere called the turbopause layer, all gases exist as a homogenous mix of gases due to factors like turbulence from winds, thermal convection, and molecular diffusion. This region (homosphere) extends up to 100kms in our atmosphere to the turbopause. And within this region, the turbulence of the air dominates any stratification of gases.

Take helium for example. It exists in our atmosphere in trace amounts–as a homogenous mix along with oxygen, nitrogen, argon, carbon dioxide, and other molecules in trace amounts in the homosphere. Whenever you introduce helium at the surface of the Earth (not as helium balloons) the molecules would tend to rise, but collisions with the other molecules, and stronger turbulent currents, convection, all work stronger to keep helium close to the Earth.

But beyond the turbopause, the gases actually stratify based on their density. Hydrogen and helium, being the lightest would rise up. And for a gas molecule to leave the Earth’s atmosphere, it should require high kinetic energy and a longer mean free path (a huge space with no collisions happening) to overcome the escape velocity of the Earth. With the energy from the thermosphere and a large mean free path in the upper regions of the atmosphere, helium sometimes escapes Earth’s atmosphere.

Now back to carbon dioxide (and methane – even more potent than CO₂). They are heavy. Compared to helium, a carbon dioxide molecule is approximately 14 times heavier than helium and methane 4 times.

As you see, methane would likely rise up than carbon dioxide. And when methane is oxidized in the troposphere, carbon dioxide is released along with water vapour. And for the CO₂ molecule to blast off into space, it would require 14 times the energy of helium. And if the CO₂ gains kinetic energy (14 times the energy required for helium), it would blast off into space. Or the solar storms would strip them away.

I don’t think you can just update the emoji set alone. It’s part of the feature updates.

You can do that with FTP or SMB. You’ll need to set up an FTP server or enable file sharing on your computer to the folders you would like to share. And then you can access it from your Android with any FTP/SMB clients available from the app store. I’ve used AndSMB client and it does the job! Here is an updated overview on this.

Hello Durran,

Interesting question.

The short answer for this is buoyancy.

Long answer:

When the flask and the balloon setup is placed, it is inside a fluid (air) medium. And as it occupies a certain volume, the setup would experience a buoyant force. (If the density of the whole setup is less (hypothetically) than that of the air, it will float way, of course. But in reality, the density is high, and so it sinks.) Now when the baking soda and vinegar in the flask reacts, the gas inflates the balloon. This increases the volume of the whole system, which makes it less dense compared to the previous state. As the density decreases, the buoyant force on it increases a bit, making it to weigh lighter than before.

The law of conservation of mass is not violated here as the total mass remains the same, while the weight (mass × acceleration due to gravity) of the system is the one that changes.

Hope it helps! :)

Most games—the majority of free MMO games—are pay 2 win sadly. From the top of my mind, DOTA 2 is currently a free, play 2 win MMO that I played some time ago. You only need to pay for the cosmetic stuff. But then there is DOTA plus. But honestly, even the paid games are turning into pay 2 win these days with all that shortcut kits and other loot box craps. It’s a sad state of gaming today. So to answer your question, there are no online games these days that would qualify as a truly skill based play to win!

You’re right. A rocket with enough fuel in it would eventually leave the Earth’s gravitational field, even if the velocity is less than the escape velocity. This is because the rocket’s engine is propelling it constantly with enough thrust to counter the effects of the gravitational pull.

In the other hand, escape velocity is the initial minimum speed threshold required for an object thrown or launched upwards from the surface of the Earth so that the projectile would leave the gravitational field without the need for any propulsion or work. So if you were to launch a rocket at 11.2 km/s, it can theoretically leave the gravitational field of the Earth without any further thrust from the engine. The concept of escape velocity usually applies to projectiles (objects that are not powered).

Hello Javy,

Welcome to Geekswipe Curiosity. When NaCl dissolves in water to form Na⁺ and Cl^–, depending on the ions that are already in the water medium, there would be a lot of possibilities for the two ions to bond with other counterions to become neutral again. At room temperature and pressure, most of such reactions would be soluble in water for Na⁺ and Cl^–. However, Lead ion and chloride ion for example, would result in a partially soluble precipitate of lead chloride. And silver ion with chloride ion would result in an insoluble precipitate. You can refer this solubility chart for all possible reactions.

When light is incident on the photosystem II, the electrons in the chloroplast molecules are excited. And when this energy is transferred to the reaction centre (via resonant energy), the electron acceptors remove the excited electron from the (special pair) chlorophyll and initiates the electron transport chain process.

Also, due to photolysis, the water molecules are split into O2 atoms and H2+ ions. The electrons lost by the chlorophyll pigments in the photosystem II is replaced by these electrons lost (by the H2 atoms) in the splitting of the water. The H2+ ions then form the hydrogen ion gradient coupled with the electron chain, whereas the O2 atoms combine to form oxygen molecule that is released as a by-product.

Further down the electron transfer chain, the electrons from photosystem II reaches photosystem I and is accepted by the already electron deficit chlorophyll molecules (The photosystem I would also lose electrons the same was like photosystem II) in the reaction centre of photosystem I. The lost electrons from photosystem I will go into making NADPH, further leading to create ATP.

So to answer your question, the electrons come from a) excitation of electrons in the photosystem II reaction centre, b) splitting of water molecules due to photolysis, c) excitation of electrons in the photosystem I reaction centre.

Hi Mark,

When you have water at two different temperatures and mix them the heat would flow from higher temperature (hot water) to the lower temperature. So the basic equation here is, heat lost by hot water = heat gained by cold water as both reach a thermal equilibrium.

Heat transfer Q = mcΔT.

Where m is the mass of the water, c is the specific heat (4.1855 J/g°C) and ΔT is the change in temperature.

For your case, X litres at 5 degrees C and Y litres at 10 degrees C,

Cold 5——x——10 Hot

(X 10³)(4.186)(10 – x) = (Y 10³)(4.186)(x – 5)

Solving this, we get

X/Y = x – 5 / 10 – x

Now for your other cases, where you need to find the ratio of hot and cold water to mix and attain a specific temperature (x), all you need to do is substitute the equilibrium temperature value for x. X/Y is the ratio of the water you need to mix.

Hi Johnnie,

This is an interesting question! :)

When you press something indefinitely with the help indestructible stuff, you will eventually start the process of creating a singularity a.k.a the black hole. So to begin with, let’s consider you are compressing an object like an iron ball for example. When you increase the pressure in the container, the molecules in the ball start compressing and in the process the temperature rises (the molecular kinetic energy increases). The more you compress the more the heat is added (as work done + rise in the average kinetic energy of molecules). This will eventually lead to a change in the phase of the iron ball.

Take a look at Iron’s phase diagram below.

Let’s say you have reached a temperature of 3000 degree Celsius and pressure beyond 500 bar.

At this point, iron would only exist as a hot molten liquid. When you keep increasing the pressure with the ‘indestructible and non-reactive’ piston of yours, the molecules will soon rip itself apart and soon the electrons will rip itself from the atoms (as they will reach very high energy states), forming a very hot plasma.

You keep increasing the pressure, you would have added enough energy to overcome the repulsion between the electrons and nucleons (a countering pressure called degeneracy pressure). This is the point where you will cross the electron degeneracy pressure.

After overcoming that, you will eventually overcome the proton degeneracy pressure. And as the energy of electrons and protons are now increased, electron capture begins and all the electrons and protons will form neutrons, leaving a soup of neutrons in your unbreakable container.

Now your unbreakable container is a neutron star!

When you increase the pressure, you will overcome the neutron degenerate matter and might create a quark star (where the neutrons will now only be existing as their constituent particles as the up and down quarks). Now, you will have to increase your pressure to overcome the pressure between these quarks (quark degeneracy pressure).

And when you overcome this, you will be able to confine all of the matter in that indestructible container into a point, creating the singularity.

Hey Jrad,

Appreciate your curiosity. There are few things I don’t get in your question.

You have mentioned Δ = 6.625*10^-34. I don’t get it. The value is Planck’s constant (h). It should be Δv.

As far as the answer goes, Δx (uncertainty in position) will be very very very very very :) little for macroscopic objects. And you should not use the uncertainty principle to macroscopic objects like football as you would not be able to observe the teeny tiny variation (a little greater than the extremely small 6.626 x 10^-34 Js).

Said that… The wave-particle duality cannot be observed (as it is too small) for macroscopic objects. But it does not mean that the uncertainty principle only applies to quantum mechanics.

If we consider the football to behave as a wave, the de Broglie wavelength λ can be found.

λ = h/p (where p is the momentum)

λ = h/p = 4.141 x 10^-35 m/s (This is a very small value!)

This is the reason why the football seems deterministic

If you were to apply HUP to the football, then the uncertainty in position and velocity will both be a minuscule non-zero number. I think your confusion arises from assuming the change in velocity too close to Planck’s constant for ease of calculation. It is evident that the Δx value had to go up to satisfy the relation. When you substitute realistic values (which will still be too small), you will get some agreeable results.

Right after reading this, I remembered the words of Carl Sagan, “We are made of star stuff.” I thought I could pen down my own version of this answer here.

Let’s make a quick microscopic picture so that we can ease into the macroscopic world.

All things are indeed created by molecules. To be precise, all things are made up of elementary particles like electrons, quarks, and constituent particles like protons and neutrons. The combination of these protons, neutrons and electrons in a stable configuration as an atom creates different elements and compounds. Atoms of these elements and compounds together make different molecules, existing in different phases, influencing and reacting with one another. A beautiful harmony the universe plays!

A human is made up of different kinds of molecules in humongous numbers, forming complex shapes, performing complex chemical reactions, carrying information, replicating, all inside a very sophisticated biological system, which is the result of billions of years of evolution.

A tree is similar to a human. It is equally sophisticated as a human system, and it has its own number of different molecules and compounds orchestrating a different kind of biochemical stuff. When you make a table out of the wood from the trees, you still retain the chemical composition of the wood, except without the ‘life’ part of it.

The chemicals that are so common in wood are carbon, oxygen, hydrogen, and nitrogen. A human body has a similar composition too. We are mostly made up of oxygen, carbon, hydrogen, and nitrogen as well.

Now if we look back the timeline of our solar system, we can understand the origin or source of all these elements around us. Some magnificently violent supernova had bestowed us all the elements necessary to create the sun and the planets and possibly life we know today.

The oxygen atom in our body comes from the atmosphere, which is actually produced by the trees by photosynthesis. The carbon in the trees comes from the environment as well. But we breath out that carbon into the atmosphere in the first place as carbon dioxide. In a grand scale, all these atoms had come from that solar nebula that formed Earth.

When your great grandmother was using the table, she was closer to the table. Not for a day, but for years, I assume. The atoms in her skin would have wanted to interact with the atoms in the table whenever she touched, but repelled quite enough by the electrostatic forces. Her DNA would have been all over the table once due to her presence. So would the table still carry her essence? Or technically, will she have affected the table in a way that would have changed the wooden table’s composition according to her comfort?

In a way, yes. She would have passively affected the chemical composition of the table but in subtle ways. The table might have unique marks made by her or might show some signs of wear and tear from her prolonged use.

To answer the final question – “Is my great grand-mother some-how connected to that table now?” – Yes, the table is connected to your great grandmother in the same way the table is connected to the universe. But as you are a descendant of her, sharing her genes, the table is connected to you and your great grandmother in a special way.

Hey @jarc! Welcome to Curiosity. The only way you can sink normal ice is by increasing its density by adding foreign materials like tiny iron pellets in it while freezing. Alternatively, you could try heating up the water enough to lower the density of it so that the ice sinks in it. In this case, you would need to superheat the water above its boiling point of 100 °C.

[su_note]Caution: Don’t try this! The superheated water will boil violently the moment you introduce ice into it. More on this here. [/su_note]