Most invertebrate have an anterior ganglia or central nervous ring that are considered equivalent to the brain, but have typically less than half the neurons.

It's also the majority of animals because invertebrate species are much more numerous than vertebrate.

Cnidaria (Jellyfish, sea anemones, coral) and sponges have neither, so all their neurons are outside their non-existent brain.

The earliest evolutionary organism would have to be a single molecule (probably RNA) able to reproduce itself with potential mistakes in a very specific environment (probably rich in organic molecules) that happened to be common enough at the time this organism appeared.

Anything with multiple molecules would most likely be too complex to appear first without previous evolution to learn to make those molecules and a container.

Because we don't know what was this early environment (there's some hypothesis, but no clear answer), we can't test what was the smallest RNA possible.

Temperature-based determination existed before genetic one. Mammals, birds, and some other animals including many insects evolved genetic determination because the temperature of their egg was too stable to serve as a random way to assign sex. If the eggs have varying temperatures, temperature-based sex determination is the simplest way.

Hermaphrodism existed before non-hermaphrodite species. When sex was first evolved in the first eucharyote, they evolved into hermaphrodite species. Male and female sexes evolved later. Most likely because male animals were more successful at forcing their mate to do the female role which is more energy demanding, so they could breed more.

No, Australia was separated from Asia during the glaciations while the parts of Indonesia homo erectus went to were contiguous to Asia.

There's no evidence homo erectus ever learned to build boats to cross to islands like Australia.

If all the cancer cells and precancerous cells (cells with some of the mutations needed to be cancerous but not all) are dead, you can get a new cancer from new mutations, but it's not more likely than before you got cancer. It's not the cancer coming back, it's a new one. Killing the precancerous cells is easier than the cancerous cells because they are localized around the main tumor. They can't go through metastasis and move away. They are killed when the main tumor is removed or destroyed with radiation.

Often not all cancer cell are dead, that's why the cancer comes back. Then it's the same cancer. Even if it appears in a different location, it's still the same one, it just got to the new place through metastasis.

All inertial frames are correct in special relativity. Special relativity works well in this case.

Though we aren't perfectly inertial due to the acceleration of the sun and the galaxy, it's still close enough. Those accelerations are relatively small.

The expansion of the universe is proportional to t^(2/3) in a matter dominated universe and t^(1/2) in a radiation dominated universe. Both have power less than 1, so the universe is decelerating.

In a dark energy dominated universe, the expansion is proportional to e^t, so it's exponentially growing, and exponentially accelerating.

https://en.m.wikipedia.org/wiki/Friedmann_equations

In the current universe (which is mostly dark energy, but has still a lot of matter), it's slowly accelerating.

Those equations come from general relativity and are harder to understand and follow though.

To understand the principle, it's best to think of the universe from an observer point of view with newtonian gravity.

Yes, though the galaxies that are outside the local group have enough energy not to crash into us even if we don't consider dark energy which will push them away even faster. Without dark energy, they would decelerate relative to us, but still always going away.

The observed speed is always less than c.

The comoving speed is not limited. If you consider ont special relativity, it's equal to gamma*v so as v goes towards c, the comoving speed goes to infinity. Even with general relativity, it's still true that the comoving speed goes to infinity as the observed speed goes to c.

gamma is the Lorentz factor 1/sqrt(1-v2/c2)

The expansion of the universe is kinetic energy. The matter is going farther from you (the observer) at a given observed speed and you can compute an energy for that, that's an accurate measure of the kinetic energy. Father things go faster, so they have more energy. Also, the observed speed is always less than the speed of light, so everything has a finite energy.

All the mass between you and a far object cause a gravitational pull towards you which slows down objects. The mass distribution is approximately spherical, so all the mass that is farther than a object gets its gravitational pull on that object canceled.

Things get more complicated when you consider général relativity, and a constant energy that doesn't get diluted by the expansion (cosmological constant, dark energy or vacuum energy) accelerate the expansion of the universe rather than slowing down.

However, for the effect of ordinary matter, Newtonian gravity works fine to explain why it makes the expansion decelerate. General relativity agrees with it.

All observers see themselves in the center, and agree that galaxies decelerate (if only ordinary matter is involved) which correspond to the deceleration of the expansion. It doesn't need a center in the comoving coordinates (the coordinates in which there's no center and no specific observer) to get the same result.

It takes millions of years to change. The amount of O2 in the atmosphere is large compared to the amount of organic carbon in the biosphere and the available fossil fuels, so burning the biosphere (trees mostly) and fossil fuels don't change the amount of O2 that much.

Over millions of years, oxygen oxidize metals and carbons brought by volcanoes and then exposed through erosion, so oxygen level can go down. This is opposed by having living beings producing organic carbon-rich sediments that becomes rocks under water. Though a small percentage of those rocks are coal, most of it don't contain enough carbon to be fossil fuel or are too deep under ground.

Over millions of year the oxygen level change. It is believed it peaked at some 30% in earlier times. Also, it has been close to 0% for billion of years (it took a long time for oxygen produced by life to oxidize all the already available metals, mostly iron).

The amount of CO2 changes fast because there is very little CO2 naturally in the atmosphere. That's because CO2 is very soluble in water and also combine easily with ions such as calcium ions to make carbonated rocks. So over million of years, CO2 in the atmosphere doesn't change much even though O2 changes a lot. If you include the CO2 in the ocean and the carbonated rocks then it changes a lot. That's also why we say that the CO2 we put in the atmosphere will last about 100 years. If we were to stop putting more CO2 in the atmosphere, it would go down to its previous levels by the ocean absorbing the CO2 in about 100 years.

They have 3 vaginas, but the 3 vaginas are inside the cloaca, so there is only one external opening.

The penis is two-pronged to penetrate both lateral vaginas at the same time, though typically only one is fertile at a time. The penis is also inside the cloaca while not erect.

They also have 2 uteri.

The middle vagina is for the baby to leave any of the uteri, and then the baby leaves the body by the cloaca and then gets into the pouch.

https://trishansoz.com/trishansoz/animals/marsupial-reproduction.html

Only if the accelerating twin passes through regions of lower space-time curvature (lower gravitational field).

And unless he gets in a region of negative curvature (doesn't exist in our universe as far as we know) his speed must not be too fast.

There is no evidence that the ocean was ever filled with amino acid and nucleic acid. Also, there are a lot more possible amino acids and nucleic acids than the 20 amino acids and 5 nucleic acids we use. We would expect living beings coming from a different abiogenesis to use different ones.

It is possible.

We have not observed it. If it does happen, it happens in small scale and the new liveforms don't spread (possibly because they can't compete with established lifeforms and get eaten).

We have no idea what is the probability of abiogenesis for a given environment.

Gravitationally bound objects are elleptical if they have low friction (due to extremely low gas density between compact objects) like elliptic galaxies, oort clouds, and many other things, or are supported by pressure like stars, planets, and big satellites. They get more spherical if the angular momenta of each of their constituents are more equally distributed (only for low friction objects. High friction objects supported by pressure have an angular momentum in a specific direction) and if they are less disturbed by the gravitation of nearby objects.

They are flat disk if they have high friction (due to high gas density between compact objects) and are supported by angular momentum., like spiral galaxy, planet disks and accretion disks. They remain flat until perturbed by a collision even if the gas density went down enough that the friction is now low. That's the case of many planet disk and spiral galaxies. After a collision, they will get first irregular and then elliptical.

The accretion disk around the sun used to be a high density region while the gas was falling into the sun so it became a disk. Most of the gas and dust fell into the sun, but the remains are the planets and asteroids. The oort cloud is the part of the cloud that formed the sun that never got enough density to become a disk.

The one on Earth ages more.

For the person who moves, the circumference of the universe is smaller. So he sees his twin on Earth crossing the universe in a shorter time than his twin sees him crossing the universe in the spaceship. So at the end of the travel, the spaceship twin will say that the total time passed is less than what the Earth twin will say. Both will agree on the speed the other one was going. They disagree on the total distance and the time.

A spherical universe is one of the 3 solutions for a homogeneous and isotropic universe (flat and hyperbolic are the 2 other ones). There's no preferred frame in a spherical universe.

Still for the person who moves, the circumference of the universe is smaller. So he sees his twin on Earth crossing the universe in a shorter time than his twin sees him crossing the universe in the spaceship. So at the end of the travel, the spaceship twin will say that the total time passed is less than what the Earth twin will say.

If you average 5 years of 25x and 100 years of 1x, compared to 100 years of 1x (CO2), that's 2.25x in average.

The long term average will always be smaller than the short term one.

Yes, the photons are the sine wave component of the waveform. You can get the distribution of photon in function of frequency, wavelength, momentum or energy by taking the fourrier transform of the waveform.

The longest wavelength photons have less energy per photon. Radio signals have an extremely large number of photons, they are not large photons.

Any wave other than the sinusoidal wave is a combination of photons (unless they are bound, then the wavefunction of each photon is not a sinusoidal). We can do complicated waves in any wavelength we can produce large amount of photons on command, so from radio to X.

All photons combine their wave function to form a more complicated wave. They are still linearly independent and act as independent photons. The combination happens only if you check the wave which is the sum of the wave function of each photon.

They can. They do it during the supernovae. However, it consumes energy rather than producing it, so rather than generating more radiation pressure that stop gravitational collapse, it reduces the amount of radiation pressure and accelerate collapse. Therefore, the supernova happens very fast. Still, all elements heavier than iron also comes from nuclear fusion and nuclear breeding (neutrons being absorbed by nucleus) and there are a lot of them.

Because you don't live in a low altitude region most likely, which is normal since most people live a lot more than 1 meter above the sea level and we won't even get an increase of 1 meter by 2100 in most prediction (though we will get close).

Also, most low altitude regions have dikes to block the sea and river from flooding the land.

From an observer's point of view, the universe grows at the speed of light since the Big Bang if it's flat. It's always finite. The boundary doesn't age, so it's still at the Big Bang with an infinite density.

From a global point of view, a flat universe went from a volume of 0 to an infinite volume instantly at the Big Bang. The universe contains matter that goes from a speed of 0 to infinity, and it can go from a volume of 0 to infinity instantly. The speed between each piece of matter is proportional to its distance.

The speed in the global point of view is equal to gamma*the speed in the observer's point of view. So a speed of c for an observer is equal to a speed of infinity globally as gamma is infinite for v=c.

The CPU sends the meshes (set of vertices) and textures (non-uniform colors that go in the area between vertices) to the GPU when the software is loaded. Those are saved in the GPU memory. They can be updated from time to time, but they are changed as rarely as possible.

For each frame, the CPU sends commands to show those meshes by sending their position, axis, and scale, and those textures by sending in between which vertices it should appear. The GPU gets all those objects from memory, put them in the good position, axis, and scale in RGB arrays, and combines them. Combining them includes having only the ones in the front if they are opaque, and doing some addition if they have some transparency. The GPUs can also compute the effects of lights, in particular using ray tracing, to determine the brightness of each pixel.

Here is some extra information: https://computergraphics.stackexchange.com/questions/12110/what-data-is-passed-from-the-cpu-to-the-gpu-each-frame