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#### The Scientist posted:

What would be the closest thing to an "ideal" reaction? Like, antimatter colliding with matter?

Yes, an anti-matter reaction is a pure matter-to-energy conversion, which is why they're so violent. Complete Annihilation of both substances mostly into, I believe, Gamma Waves.

E=mc^2

m= .5 gram of matter, .5 gram of antimatter

E= .001 * (299 792 458)^2

E= .001 * 8.98755179 × 10^16

E= 8.98755179 × 10^13 Joules = Asstons of energy

#### The Scientist posted:

So why are our mere earthly reactions and physics applications so inefficient? We are just losing energy when its converted to unusable forms? Like the heat in an internal combustion engine (that not only do we NOT use, we use up energy of the flywheel's momentum powering water pumps and radiator fans trying to GET RID of it)? Are man-made energy sources THAT lossy?

What would be the closest thing to an "ideal" reaction? Like, antimatter colliding with matter?

Because on a fundamental scale, our energy production methods aren't that much above burning stuff for heat.

The most ideal reaction would be mass -> energy. This is not going to happen any day soon so the closest to that would be 1 unit matter + 1 unit antimatter = 2 units energy. Of course the problem here is that the antimatter will have to actually be created first, which also costs energy. I suppose ideally maybe one day we can transform 1 unit energy -> 1 unit antimatter and let that react with matter (asteroids, moons, even slowly consuming entire planets or useless solar systems if the Human Empire becomes big enough) so you could theoretically have a system that has an input of 1 energy to give out 2 energy. Of course in practice that is 2 energy minus the loss of energy in the process and the energy lost to transport everything etc.

edit; this of course assumes a level of technology far, far beyond anything we have right now and maybe ever will have.

 _Dav Dec 24, 2008 These relativity posts are really blowing my mind, it's just so counter-intuitive to me. I still misunderstand the time standing still problem where you would need to switch off your device. So, at c time doesn't move for you (right?). Does that not mean that once you've reached it, you're stuck and you do not and cannot know it? # ? Nov 18, 2010 19:06
 Lockback Sep 2, 2006 Also? Amplitude. You can't accelerate to C. You can get close, but if you have mass you cannot reach C. That's why the thought-experiment falls apart. # ? Nov 18, 2010 19:07

#### Lockback posted:

You can't accelerate to C. You can get close, but if you have mass you cannot reach C. That's why the thought-experiment falls apart.

If you did, you'd be accelerated by an infinite force, and have infinite mass at that point. So, uh, I guess by that point your gravity itself would drag the entire universe in and you'd become the awesomest black hole ever.

VV possibly. So basically, accelerating to C is such an impossibility that doing so, as something with mass, would probably destroy the universe. Note that I have not sat down and calculated this, as there's literally no way this can be achieved in reality, and perhaps some more physics-minded people can explain what the implication of having something with infinite mass around would be.

Exercu fucked around with this message at Nov 18, 2010 around 19:19

#### Exercu posted:

If you did, you'd be accelerated by an infinite force, and have infinite mass at that point. So, uh, I guess by that point your gravity itself would drag the entire universe in and you'd become the awesomest black hole ever.

So, you'd destroy everything?

#### _Dav posted:

So, you'd destroy everything?

Yeah, but in order to do that everything would need to be propelling you, so it all deserved what it got at that point.

#### _Dav posted:

So, you'd destroy everything?

More or less. Gravity is the attraction between two masses. Any two (or more) masses. That means that the centre of our galaxy is exerting a gravitational force on you right now. Even the most distance stars and planets and possibly alien lifeforms pull on us with minute gravitational pull. Similarly, every atom of your existence exerts a force on every other atom in existence. Now there are some very, very massive things in the universe, but all does not even come close to infinity. If you have infinite mass, you subsequently exert an infinite amount of force of everything in the universe, brilliantly blinking everything out of existence instantly.

Namarrgon fucked around with this message at Nov 18, 2010 around 19:22

 Doniazade Jul 13, 2006 Re: relativistic mass: Nuclear power does in fact convert some mass directly into energy. The reactions involved are fairly complicated, but the gist of it is this: You have a nice fissionable atom like uranium-235 or plutonium-239. A free neutron(produced by other nuclear reactions) hits it, causing it to become unstable and split into several fragments, usually two lighter nuclei and a few neutrons. However, a large amount of energy is also produced, mostly in the form of the kinetic energy of the products resulting from the fact that two positively charged nuclei end up very close to each other, causing them to rebound away from each other due to electrostatic repulsion. This means that the new nuclei will bounce around at a ridiculous speed until the collisions with nearby atoms convert their kinetic energy into macroscopic heat. This in turn heats the surrounding water of the reactor tank and boils it into high-pressure steam which then goes through a turbine that in turn drives an electrical generator, producing electrical power so that you can browse for cat pictures on the internet. The steam is then cooled(usually with seawater) and cycled back to the generator. In modern reactors, this process converts about 30-35% of the thermal energy put out by the reactor(depending on several factors like design and cooling water temperature) into useful electrical energy with the rest being lost in the form of waste heat(heating of the cooling water) for thermodynamical reasons. Anyway, the point was... You know the heat energy from the nuclear reaction? That poo poo actually causes the nuclear fuel to lose mass, because the fission products are lighter than what you put in. You can actually calculate how much thermal energy a nuclear reactor has put out by comparing the weight of the fuel to its weight when you started the reactor. Example: The Forsmark 3 nuclear reactor in central Sweden is rated at 3300MW thermal output. That means that in one year of continuous operation at maximum power, 1.041*10^17 J of heat energy is produced which is the mass-energy equivalent of about 1.2 kilograms=2.6 pounds. This means that even though no fuel is removed from the reactor during operation, the total mass of all the fuel used during the year has decreased by 1.2 kilograms. You can actually weigh the fuel and find that this is true. No fuel was removed, yet it is lighter. Here's the kicker: This also applies to "regular" fuels as well as everything else, not just nukes and antimatter. When you burn coal, the products are lighter than the reactants because the system lost energy. A battery loses mass during operation. Compressing a spring increases its mass. The earth is heavier because it spins(by about 2.4 billion tons). Hotter objects are heavier because they have more heat energy. E = mc^2, bitch. Science owns. Doniazade fucked around with this message at Nov 18, 2010 around 21:47 # ? Nov 18, 2010 19:26

Compressing a spring increases its mass.

Is this something you can measure with a letterweight or something? Because that would be totally to do.

Edit: Letterweight, not featherweight, is letterweight a word in English?

Black Griffon fucked around with this message at Nov 18, 2010 around 20:29

#### Black Griffon posted:

Is this something you can measure with a featherweight or something? Because that would be totally to do.
In practice - not really. A quick googling says high-performance springs can store about 0.5kJ in potential energy per kg of spring mass - let's be generous and call it 1.0kJ. This increase in potential energy is equivalent to 1.1*10^-14kg = 11 picograms, which is many orders of magnitude smaller than what can be measured with even the most precise balances.

So theoretically yeah, but in practice our instruments aren't good enough and even if they were there are severe practical problems because of the many, many factors which can disturb the reading.

Doniazade fucked around with this message at Nov 18, 2010 around 20:16

 MindlessHavok Jun 20, 2004 Please, Sammie. They had a fan base. ~Tito~ None of this is blowing my mind because I have no idea what any of you are talking about. Y'all smarter than me, yo. That said, with the whole matter/anti-matter thing and them going boom if they interact...How is there not a constant interaction at some point? At the edge of anti-matter, wouldn't there be matter? I probably am making no sense because I have no idea what I'm talking about. # ? Nov 18, 2010 21:14

#### MindlessHavok posted:

None of this is blowing my mind because I have no idea what any of you are talking about. Y'all smarter than me, yo.

That said, with the whole matter/anti-matter thing and them going boom if they interact...How is there not a constant interaction at some point? At the edge of anti-matter, wouldn't there be matter?

I probably am making no sense because I have no idea what I'm talking about.

You're asking how a universe that would logically contain 50% matter and 50% antimatter could still exist?

Excellent question, no one knows

#### MindlessHavok posted:

None of this is blowing my mind because I have no idea what any of you are talking about. Y'all smarter than me, yo.

That said, with the whole matter/anti-matter thing and them going boom if they interact...How is there not a constant interaction at some point? At the edge of anti-matter, wouldn't there be matter?

I probably am making no sense because I have no idea what I'm talking about.

At the beginning of time there was slightly more matter than antimatter. This tiny surplus is what makes up everything today. We don't know why this imbalance exists.

Nowadays antimatter is only produced in the most exotic of conditions (e.g. done by us when trying to) or randomly bleeps in and out of existence in even more miniscule amounts (ignore this one for now) and both produce only very very tiny amounts.

#### Asphalt Engine posted:

After long periods of Dance Dance Revolution play with friends, we had to take a break before driving home. "DDR eyes," we called it. Those drat arrow patterns...

#### Treebeh posted:

Same thing after long nights of drunken Rock Band. It's like your vision is constantly swimming upward. Although, that could just be the drunkenness.

Sorry to interrupt all the physics, but you two are talking about the Motion After-Effect! Basically, your brain is adapting your visual field to ignore the repetitive motion of the guitar path, so when you look at something static, it's compensating for movement that doesn't exist. Here's a really cool site where you can mess around with this effect.

Nothing blows my mind more than learning how our brains work!

Edit: for clarification.

plainswalker75 fucked around with this message at Nov 18, 2010 around 21:57

#### Black Griffon posted:

Is this something you can measure with a letterweight or something? Because that would be totally to do.

Edit: Letterweight, not featherweight, is letterweight a word in English?

Run faster. You are now (very slightly) more massive. Ta-da. (In practice you're exhaling or excreting more mass than you're gaining, but you get the picture)

Incidentally, antimatter is produced constantly, through such things as Beta decays and pair production, which happen all the time (including the decay of Carbon-14 in your body). Antimatter is neither exotic nor uncommon. Antimatter is flying through you and being produced in you as you read this sentence. We just never see whole anti-atoms in nature.

#### Chard posted:

Earlier in this thread someone posted something about how there may only be one electron in the universe and it 'magically' exists everywhere at once and interacts with itself across time. Is this idea in the same vein? I could reconcile those two concepts I think.

That was me. The electron business is purely a theory, but the maths and quantum theory don't contradict it.

The short version is, an electron travelling forwards in time is indistinguishable from a positron travelling backwards in time. Think about it - if I film a negatively charged electron flying towards a proton and a positively charged positron flying away from a proton, and play the second film backwards, you can't tell one from the other. The analogy extend to every observable quantum mechanical property of electrons like spin etc.

As others have said, the photon business is part of special relativity (although I don't think it's been proven either - but no-one disputes it)

Captain Postal fucked around with this message at Nov 18, 2010 around 23:03

 Factory Factory Mar 19, 2010 I can do sex. It's just alien sex. I remembered another fun relativity fact, but since I'm on a phone, I'm gonna leave the hardcore explanation to someone else. We've been over the Twin paradox and how acceleration can desynchronize "now" for multiple people when considering people coming face to face, i.e. one twin now older than the other. But distance plays a factor as much as velocity. Say there's an alien named Bob in a galaxy 10 billion or so light years away. Bob is walking down the street coincidentally exactly away from us on Earth. Our nows are in sync. He walks as you read this. Bob realizes he left his space oven on, so he turns around and starts walking in the other direction. Because of the distance, Bob's little change of direction has put his now 10,000 years into your future. (Again, got this from Brian Greene. I think he used Chewbacca, though) Factory Factory fucked around with this message at Nov 18, 2010 around 23:29 # ? Nov 18, 2010 23:22
 Mr. Sunshine May 15, 2008 Can anybody find me somebody to love rape and torture? Another nice little quirk of relativity. You know how we said you can't accelerate up to c? The theoretical framework for this is because you get a nice divide-by-zero in the mathematical formula. However, there's nothing in that formula preventing you from starting out already going faster than c. However, if you start out at superluminal speeds, deccelerating to c gives you the same divide-by-zero error. So you can go faster than light, provided that you never have and never will go slower. You'll also have a negative time dilation, which means that you experience time backwards. Which probably means that there is no way to tell if you travel at subluminal speed going forwards in time, or traveling at superluminal speed going backwards. Mr. Sunshine fucked around with this message at Nov 18, 2010 around 23:25 # ? Nov 18, 2010 23:23
 Vectorwulf May 5, 2010 To touch off on the energy generating awesomeness from the last few pages... Something that blows my mind is that in everything from Coal to the latest Nuclear Power plants, all these vastly different resources and methods of generating energy, do it all to simply generate steam. Amazes me that in light of all these tremendous advances, the end goal is still to use something as simple as heated H2O to spin some fans. # ? Nov 18, 2010 23:27
 NosmoKing Nov 12, 2004 I have a rifle and a frying pan and I know how to use them ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Edit: someone didn't watch ELECTRICITY! ELECTRICITY! from schoolhouse rock as a kid. "spin that generator by any means". ENOUGH WITH THE E=MC2 STUFF!!!! Sperm whales. Sperms whales are the largest toothed whales in the whole entire world. The survive on a diet that leans heavily towards squid, and even MORE heavily towards giant squid. Sperm whales eat giant squid, in huge numbers. Prior to hunting the poo poo out of sperm whales, the population was estimated at 1,100,000 sperm whales in the ocean. Think about how many giant squid would be required to support a population that uses this apex predator as a primary food source. Until 2004, there were no confirmed and documented sightings of this animal ALIVE in the wild. Until 2006, there were no videos of this animal alive in the wild. A gigantic animal that has a population that must number in the hundreds of millions to billions has successfully hid from humanity until 4 years ago. # ? Nov 18, 2010 23:30

#### Mr. Sunshine posted:

Another nice little quirk of relativity. You know how we said you can't accelerate up to c? The theoretical framework for this is because you get a nice divide-by-zero in the mathematical formula. However, there's nothing in that formula preventing you from starting out already going faster than c. However, if you start out at superluminal speeds, deccelerating to c gives you the same divide-by-zero error. So you can go faster than light, provided that you never have and never will go slower.

You'll also have a negative time dilation, which means that you experience time backwards. Which probably means that there is no way to tell if you travel at subluminal speed going forwards in time, or traveling at superluminal speed going backwards.

Tachyons.

Particles that can go faster than light because their existance begins faster than light. They cannot ever go... slower than light.

http://en.wikipedia.org/wiki/Tachyon

Edit: Sperm whales are also awesome. Tachyon Sperm Whale. There's a rock band name.

#### MindlessHavok posted:

None of this is blowing my mind because I have no idea what any of you are talking about.

Don't worry, neither do they.

#### Factory Factory posted:

I remembered another fun relativity fact, but since I'm on a phone, I'm gonna leave the hardcore explanation to someone else.

We've been over the Twin paradox and how acceleration can desynchronize "now" for multiple people when considering people coming face to face, i.e. one twin now older than the other. But distance plays a factor as much as velocity.

Say there's an alien named Bob in a galaxy 10 billion or so light years away. Bob is walking down the street coincidentally exactly away from us on Earth. Our nows are in sync. He walks as you read this.

Bob realizes he left his space oven on, so he turns around and starts walking in the other direction. Because of the distance, Bob's little change of direction has put his now 10,000 years into your future.

(Again, got this from Brian Greene. I think he used Chewbacca, though)

Can someone explain this if it's true?

It seems like since his planet would still be moving in a very similar reference frame to earth, this wouldn't be true.

 big business sloth Jun 7, 2007 hella greenbacks Before we stop derailing this with relativity talk, so what do observers see when you're in your spaceship going near-c around the earth once? Something going real fast for a long time? Or would they see you going through motions in your spaceship real, real slowly, since it's taking you say 10 years from their perspective and >1sec for you? # ? Nov 18, 2010 23:43

#### Lrrr posted:

I found this funny: "Einstein only called it "peculiar"". Makes you wonder what would blow his mind...
Trying to remember his own address.

#### Supreme Allah posted:

Tachyons.

Yes, but they're not real. Just theoretical.

#### Factory Factory posted:

A bit of fun with relativity:

The idea of travelling at c is blowing my mind a bit, because it introduces an interesting paradox. Say you used a machine strapped to your back to get you up to speed, and it travelled at c along with you. How would it ever stop you? Since time would "stop" and everything would be in a single instant for the machine's decision-making gear, how would it ever now to stop slowing you down? Or even if it could, how would it ever know do so after a fixed period of time?

I believe this part is conceptually inaccurate on your part.

As you (and your accelleration machine) are zipping around the universe at c, you still experience time normally in your own (and the machine's) frame of reference.

I think

#### Alpine Mustache posted:

I believe this part is conceptually inaccurate on your part.

As you (and your accelleration machine) are zipping around the universe at c, you still experience time normally in your own (and the machine's) frame of reference.

I think

No, look back over the past few pages with the discussion of time dilation & length contraction. It literally is incomprehensible and wouldn't make any sense. Going at c, everything in the universe has a distance of 0, so it is impossible to head out, travel around, or arrive anywhere.

 The Scientist Nov 6, 2009 Good news everybody! 1. A single strand of human hair has the same shear strength as an equivalent size copper strand. 2. A spider's silk has the same tensile strength as an equivalent size of a high tensile steel cable strand. They use their silk in some badass MacGyver-esque ways - one example being http://en.wikipedia.org/wiki/Ballooning_%28spider%29. Most only go the couple of meters they soar from the top of their tree. But some get caught in a jet stream. Sailors have reported having spiders riding kites caught in their sails. 1600 km from shore. Atmospheric data-collecting balloons have recorded them at altitudes just shy of 16000 ft. 3. The highest ever, regularly recorded bird is a type of bar-headed goose, which is sometimes seen flying higher than the peak of mount everest in the Himalayas, altitude ~29,000 ft. There are reports of a http://en.wikipedia.org/wiki/R%C3%BCppell%27s_Vulture being sucked into a jet engine off the Ivory Coast of Africa at 37,900 (!#%!) I'm also thinking of a couple other ones that I only have a vague recollection of: A wood-boring wasp, hornet or bee that has a stinger made of tungsten carbide (I think) and the fact that ever since a certain spacecraft with a nuclear decay thermocouple generator blew up in the atmosphere, every human on earth has a piece of decaying Cesium (?) in them that one can locate with a Geiger counter. Can anyone shed light on either of these two? edit:We have always been at war with misspelling of the word "off" # ? Nov 19, 2010 01:35

#### lapse posted:

Can someone explain this if it's true?

It seems like since his planet would still be moving in a very similar reference frame to earth, this wouldn't be true.

Okay, I'm back at a real computer, so let's see what I can do. The easiest way to visualize what's going on is with a Minkowski Diagram.

This is one for the Twin Paradox. As you go up, time relative to the twin on earth passes at a constant rate. As you go right, the distance from the twin on Earth increases. The blue lines and red lines represent simultaneous moments for the two twins, that is the twins would agree that two events on that line happened at the same time from both their perspectives. That is their common "now". (I may suck at understanding/explaining these correctly, so keep that in mind)

The kink in the moving twin's line (where it makes an angle) is where the twin accelerates to go back towards Earth. At that point, the acceleration shifts their lines of simultaneity. The blue lines represent simultaneous events before that acceleration, and the red lines represent those events afterwards. Now, we're just seeing a few of these lines - as the space twin accelerates, the simultaneous line sweeps very quickly over the Earth twin's timeline.

Now let's look at Bob's Minkowski diagram. He's very far away.

This is so not to scale, but it still gets the point across. The very very tiny change in the angle of the simultaneous line when Bob changes direction sweeps over a HUGE part of your timeline back on Earth.

Think of all the people in other galaxies we're completely missing every time we start walking.

I loving love cosmology. I wish I had enough time and money to get another bachelor's in physics.

Factory Factory fucked around with this message at Nov 19, 2010 around 01:50

#### The Scientist posted:

I'm also thinking of a couple other ones that I only have a vague recollection of: A wood-boring wasp, hornet or bee that has a stinger made of tungsten carbide (I think) and the fact that ever since a certain spacecraft with a nuclear decay thermocouple generator blew up in the atmosphere, every human on earth has a piece of decaying Cesium (?) in them that one can locate with a Geiger counter. Can anyone shed light on either of these two?

edit:We have always been at war with misspelling of the word "off"

I've heard about the satellite. I'm sure many, perhaps most, people have some atoms of that cesium somewhere in their bodies. But you definitely could not track it with a geiger counter. You've got more radioactive isotopes in your body from the vegetables you ate in the past few days than from one satellite.

You'll get more exposure from eating a bowl of spinach or standing in the sun for a few minutes than from satellites burning up in the atmosphere. There's just an inconceivable amount of atoms in one lump of metal (say, about 4.5x10^(21) atoms for a one kilogram lump of cesium, by my math), and some of that likely wound up in you.

Nibbles the Shark fucked around with this message at Nov 19, 2010 around 01:53

#### Nibbles the Shark posted:

I've heard about the satellite. I'm sure many, perhaps most, people have some atoms of that cesium somewhere in their bodies. But you definitely could not track it with a geiger counter. You've got more radioactive isotopes in your body from the vegetables you ate in the past few days than from one satellite.

You'll get more exposure from eating a bowl of spinach or standing in the sun for a few minutes than from satellites burning up in the atmosphere. There's just an inconceivable amount of atoms in one lump of metal (say, about 4.5x10^(21) atoms for a one kilogram lump of cesium, by my math), and some of that likely wound up in you.

I can vouch for the sun exposure part; I had melanoma at the age of 13. But does the sun emit radiation, like Alpha, Beta, or Neutron radiation? Or are we talking radiation like the way EM waves (Ultraviolet) radiate from their source?

I guess it makes sense if you were to picture cancer as a strain of cells' genomes being altered, resulting in a mutation in which the "off" switch is no longer functioning as needed (metastasizing). And we all know that, of course, Alpha (under perfect circumstances and prolonged exposure), Beta (again under pretty ideal circumstances) and Neutron radiation can cause cancer.

And I guess X-Ray's clearly can cause cancer, as well. I guess I just never made the connection between Ultraviolet Waves and "Radiation" (Alpha, Beta, whatever).

And so what exactly is the earth's magnetic flux deflecting? Ions? (I'm referring to what causes the phenomena, one visual representation of which is the Aurora Borealis)

edit: VVVVVV Hey! Look at that! I'm telling you, the repository of knowledge on SA is unequaled. Looks like the males, who don't have "stingers", have manganese and/or zinc in their mandibles

The Scientist fucked around with this message at Nov 19, 2010 around 02:25

#### The Scientist posted:

I'm also thinking of a couple other ones that I only have a vague recollection of: A wood-boring wasp, hornet or bee that has a stinger made of tungsten carbide (I think)

I believe these would be the ichneumon wasps whose ovipositors have been found to be metal-tipped to aid in drilling into wood when laying eggs on boring grubs.

#### The Scientist posted:

I can vouch for the sun exposure part; I had melanoma at the age of 13. But does the sun emit radiation, like Alpha, Beta, or Neutron radiation? Or are we talking radiation like the way EM waves (Ultraviolet) radiate from their source?

I guess it makes sense if you were to picture cancer as a strain of cells' genomes being altered, resulting in a mutation in which the "off" switch is no longer functioning as needed (metastasizing). And we all know that, of course, Alpha (under perfect circumstances and prolonged exposure), Beta (again under pretty ideal circumstances) and Neutron radiation can cause cancer.

And I guess X-Ray's clearly can cause cancer, as well. I guess I just never made the connection between Ultraviolet Waves and "Radiation" (Alpha, Beta, whatever).

And so what exactly is the earth's magnetic flux deflecting? Ions? (I'm referring to what causes the phenomena, one visual representation of which is the Aurora Borealis)

Yes, radiation refers to both fast-moving particles as well as light. The main culprit from the sun is ultraviolet radiation, which is energetic enough to ionize molecules in your body a.k.a. energetic enough to gently caress you up; the magnetic field deflects a lot of the charged particles which come out of it (which make the auroras) and ozone is a good absorber of UV light, so the majority of solar radiation doesn't reach your tender, vulnerable flesh and give you melanoma all the time.

UV is electromagnetic waves, rather than particles, but at shorter wavelengths, photons interact with atoms in quite violent ways.

Nibbles the Shark fucked around with this message at Nov 19, 2010 around 02:31

#### plainswalker75 posted:

Here's a really cool site where you can mess around with this effect

Just wanted to say thanks; this is a fantastic link!

Also, this is pretty drat cool--scientists are working on a camera that can take pictures around corners (i.e. of what can't be "seen"): http://www.bbc.co.uk/news/technology-11544037

 RevXwise Aug 14, 2010 There are 128 GB flash drives. You can plug in a flash drive that is multiple times larger than the entire hard drive on an older PC. RevXwise fucked around with this message at Nov 19, 2010 around 03:49 # ? Nov 19, 2010 03:44

speed of light. Let's say you're on a train, going 10 meters per second. You fire a gun from the roof in front of the train. The bullet goes 300 meters per second. So if you measure the bullet, how fast is it going relative to the ground? 310 meters per second, because it was already going 10 m/s before you fired the gun.

Actually, THIS was the only part of this post that I find hard to accept.

#### kjetting posted:

Actually, THIS was the only part of this post that I find hard to accept.

Why? If it didn't, then if you dropped something while in an airplane, it would, instead of falling roughly like on earth, SMASH AGAINST THE WALL BEHIND YOU AT THE SPEED YOU'RE FLYING. I have accidentally dropped pencils while in airplanes, and I can inform you that they, from my point of view, fall completely normally, vertically. Of course, some bystander standing by the side would, if he could only see the pencil, see it falling diagonally because it's already accelerated by the plane itself. If the bystander were to see the pencil fall vertically only, it would in relation to the airplane be moving at the airplane's speed...backwards. It's the same reason why it's better to run and throw a javelin than it is to stand still and throw one.