#### Dalisclock

##### Making lemons combustible again
Legacy
Escapist +
Do you play Kerbal Space Program or are you familiar with it? If so, do you feel it's reasonably accurate as far as flight physics are concerned?

On the other side of the coin, does the use of Quantum Physics and Time Travel as a substitute for magic in some sci-fi stories, such as Bioshock: Infinite, annoy you? Or in situations like that do you just roll with it and judge the work on it's other merits?

I worked with Nuclear Power for several years and got my degree in it, so some depictions of Nuclear Power/Reactors/Weapons annoy me and others I'll let slide depending on how much I like the work overall.

#### Lightknight

##### Mugwamp Supreme
Slenn said:
Lightknight said:
1. Durability:
From what I've been told, the forces that hold objects together would break down at light speed. I was wondering if the objects traveling at those speeds really experience those forces since the idea is that they'd be in a vacuum and that they would increase to that speed incrementally. So relative to us they'd be going the speed of light but relative the them we're just moving really slow. I would think that the objects traveling at that speed would be shielded from feeling the effects of that speed in the same way we are shielded when we are in a car from really feeling like we're going that fast.
I'm a little confused. Are we talking about a space ship that's in a vacuum in the first place? And what are you referring to by "increasing to that speed incrementally?" Are you assuming that the ship is increasing velocity at a constant rate?
A ship is certainly the easiest way to think of matter traveling at that speeds and increasing in velocity. Though the current arguments revolve around any matter as it reaches these speeds. All I really mean is that it isn't accelerating so rapidly as to be destroy itself by the rate of acceleration. In a frictionless vacuum the only forces one should really encounter is whatever the force accelerating them is as long as they don't encounter objects in said space (either directly or near enough as to constitute significant gravitational forces high enough to consider as a vector/vectors in the equation).

2. The interior of a vehicle traveling at near light speed:
If my question from number 1 is answered in the affirmative, then if you were inside of a vehicle traveling at light speed. What would happen if you shone a flashlight within the vehicle or tossed a ball. Would it reach the other wall? I know this is a question traditionally asked as though the flashlight were on the front of the vehicle so I thought I'd ask from the inside of the vehicle. Like how if I drop a ball inside a car it falls mostly straight down but outside the window it appears to fall behind the vehicle (I presume due to wind resistance). Or maybe within a closed system that has reached that momentum the distance from the light source to the other wall isn't seen as traveling faster than the speed of light whereas being outside of the environment would be. I'm just having a hard time considering the idea that I could technically toss a ball within a car traveling at 100 miles per hour and from the outside it look like I'm tossing the ball at 101+ miles per hour. It seems like relative speeds should still be relevant here.
Inside the vehicle, the bubble that allows for the ship to travel at the speed of light would probably mean that the beam of light inside the ship moves normally.
I'm challenging the notion of requiring a bubble for light speeds. So I'm inquiring of a scenario where a ship increases its velocity gradually enough up to the speed of light within a vacuum. I'm sure that inside a magical bubble everything would remain intact since the mythical nature of this idea would inherently mean that it's almost like the universe would be moving past the ship relative to the ship rather than the ship moving through the universe where forces enacted on it are concerned. Warp fields are fun to think about, especially with recent announcements regarding the EmDrive, but I really don't think they're as much as a given as we'd like to think they are.

Your analogy with the car needs a little more clarification. Are you suggesting that the scenario with the wind resistance is when the ball is tossed out of the window? Or are you referring to an observer watching someone drop a ball inside the car?
Keep in mind that I'm fully aware that the ball falls at the same rate either way just as a bullet if shot from the same point it would otherwise have been dropped ends up hitting the ground at the same time if unobstructed in its journey across a level plane. I'm also aware of the differences between the observer in motion compared to the stationary observer on the ball. Looking back on my quote I'm unsure what I was trying to say about wind resistance. I imagine that was an incomplete thought where I was trying to indicate that my own personal experiences have been watch the ball fall backwards rather than straight down due to air resistance that makes the reduction in momentum once unsupported/unpowered by the vehicle more noticeable. But that is my best guess as to what I meant there.

What I'm saying is that inside the car the ball is relatively unaffected by the speeds the vehicle is travelling. I can toss the ball up and it does not start to loose momentum in the same way that someone with dice on their rear view mirror do not witness it flying backwards as the car speeds forward unless an external force like wind acts on it.

So hypothetically when inside a vehicle traveling at the speed of light you should not feel as though you are moving at the speed of light just as we do not feel like the surface of the earth is moving at 1,000 miles per hour or that the earth itself is moving at 67,000 miles per hour. So at light speeds in a vacuum, what force is causing the traveler to then feel like they're going that fast if we do not experience that already? So you should be able to throw a ball and it get to the other side or shine a flashlight and illuminate the far side.

3. Faster than light travel.
When they say that if an object is traveling faster than the speed of light that it would actually be traveling backwards through time, doesn't that really only mean that the object would "appear" to be traveling back in time in relation to us but wouldn't literally be getting someplace before they left? For example, I see light as a sequence of photos stacked in an ordered pile. If you travel faster you just speed up the frames that they go past you (so if you approached a planet, it would appear to age faster as your speed increased but only because you are traveling faster and if you left the planet it would appear to be getting younger even though it only appears that way). The hypothesis here is that if you traveled faster than light and looked back that you would see yourself going backwards. But wouldn't this just be your appearance going backwards rather than you literally going back in time?
You have the right idea. You're only seeing your appearance twice, one going backwards, and the other going forwards.
The other one traveling forward being yourself in this instance, I assume.

I just don't get how we have a universe where instantaneous teleportation of information exists (quantum entanglement) but somehow traveling at an ultra fast rate of speed means that you're traveling more than instantaneously when light itself isn't anything close to instantaneous. I mean, the claim here would imply that if light traveled only 1 unit of distance faster per second that it would then be traveling backwards in time, right? Yet we measure distant objects in light years which should discredit the notion that they are on the cusp of reaching destinations before they were sent out. Right? There has to be a trick in what people mean by "time travel". Surely every object in space has its own relative "now" and no matter how fast we travel between them we can't change the object's "now" in relative to our "now". We can only make it appear like we're altering it when we aren't really. Also, at no point would we be able to look in any direction and see our future selves, only our past.
What do you mean by "ultra fast rate of speed"?
By "ultra fast rates of speed", I mean faster than light speeds. The time where science currently holds that if we could travel that fast we would be traveling through time.
I'm also not sure what you're talking about with the light year analogy. "they are on the cusp." Who's "they"? The light waves?
Yes, light waves are always on the cusp of traveling faster than light since it is itself traveling exactly the speed of light. 1 more inch per second and it should hypothetically be crossing the time travel threshold that science says we'd be crossing were we to do so.

So if it is that very close to going so fast that it could arrive at its destination before it leaves, why does it take so much time to get places even though I know those distances are vast. In fact, it is said that a photon does not experience any time at all. But it takes so long that we can even measure it on earth. Do we really hold that had light been even one iota faster in a vacuum that it would all be time traveling? Hmm... I wonder how that would look. Would we still have light or would everything be black due to light having arrived before it left ergo what we would be looking at would be a time before the light left, ergo darkness. Weird.

4. Permeation of light photons in space.
Should space be absolutely full of light photons? We can see stars from thousands of light years away from any point in space which should mean that photons are reaching our point of view. You'd think there'd be more detection of this or that they'd even interact with one another at such great numbers... right?
The thing is, space is big. Big. The distance from the Earth to the Sun is peanuts compared to the distance between the sun and the nearest star system, Alpha Centauri. And that distance reduces the power at which we receive light from them.
Sure, but for us to perceive them that means that photons from each and every one of those stars we see at night is hitting our eyes, right? If I move over four steps I presume that I am then being hit by different protons from the same stars and the longer I stand in one place I'm seeing however many subsequent photons hitting my eyes, right?

Now the stars emitting these are shooting these photons out and way from themselves in literally all directions. As far as I know, this means that as long as nothing is between me and the source of light, then I can travel anywhere and still see it as long as light has had enough time to travel to that location. So the only inevitable conclusion is that there are photons packed in every square inch in all directions, right? How do these photons not interact with one another since I can therefore assume that there are photons from every other source of light. I mean, even stars that are too faint for our human eyes to make out are still hitting us with photons as evidenced by how many stars the hubble telescope can see that aren't detectible by the human eye from earth. So why isn't this more evidence?

Though, we don't actually see light unless a photon hits our eyes, so that's why the entirety of space isn't white. But in every square inch of space the number of present photons should be astounding, right? From what I've read even the dimmest star we can still see is packing 100,000 photons per in^2 per second. From something like the sun its 2 x 10^18 photons per in^2 per second. Are we unable to see distant stars during the day because the environment is so permeated by photons from the sun both directly from the source and also bounced off of so many things to our eyes? (Though astronauts can't see stars during the day either despite the surrounding area not being dark due to a lack of things for the sun's photons to bounce off of)

So there must be a maximum saturation point of photons that our sun is capable of meeting enough to prevent viewing lesser light sources... right? I wonder if the stars we can see are actually responsible for blotting out stars we can't see. Maybe the reduction of power actually is interaction between photons... maybe not.

#### Hypertion

##### New member
do you think any normal material, metal or otherwise can survive getting to 99.9999% of lightspeed? specifically, would in those situations, approaching the speed of light have a effect on matter similar to when objects get close to the speed of sound. IE effectively hitting a increasingly high energy wave in front of the object comprised of effectively compressed light.

#### Batou667

##### New member
Slenn said:
My guess is that only at some point in the middle of the path. He will have occupied the same point at the same time of day, but on two different days.
Are you sure? Is there any possibility he could "miss" himself? Remember his rates of ascent and descent are different, and although he sets off at the same time both days, his arrival times are different.

OK, here's another one which IIRC is an undergrad interview question. You have two identical spheres in front of you. They both have a diameter of six inches and each weigh two pounds exactly. You are told that one is solid and the other is hollow. Without breaking them open or resorting to similar "cheating" solutions like using an X-ray, how could you tell which is which?

#### Fieldy409_v1legacy

##### New member
How come a fly can buzz around in a moving car without being pushed to the back?

#### Pinkamena

##### Stuck in a vortex of sexy horses
Slenn said:
Hello there!
*snip*
I laugh at your puny 4 semesters. Glance upon my 8 semesters and despair.
Also, hi. Postgrad in particle physics here. Gonna hija- I mean help out here because I love answering physics questions.

Hypertion said:
do you think any normal material, metal or otherwise can survive getting to 99.9999% of lightspeed? specifically, would in those situations, approaching the speed of light have a effect on matter similar to when objects get close to the speed of sound. IE effectively hitting a increasingly high energy wave in front of the object comprised of effectively compressed light.
The reason for aircraft and other objects moving close, and above, the speed of sound hitting the sound barrier, is because the sounds can't "get away" so to speak. The sound waves will move away in all directions from the source of the sound, and if the source moves WITH the speed of sound, well then the pressure will just build in front of the source and you have a sound wall.

Light does not have this problem. If a source is moving at a speed incredibly close to the speed of light, and it turns on a lamp, the light emitted from this lamp will not move away from the source really slowly and build up a "light wave" as sound would build up a sound wave. Instead, it zips away from the source at the speed of light. Does this sound counterintuitive? That's because it's one of the effects of general relativity. Things get real strange when you approach the speed of light.

#### RedRockRun

##### sneaky sneaky
What's up with quarks and their "flavors". What is the difference between them, and do they have anything to do with their names?

#### Pyrian

##### Hat Man
Legacy
Batou667 said:
You have two identical spheres in front of you. They both have a diameter of six inches and each weigh two pounds exactly. You are told that one is solid and the other is hollow. Without breaking them open or resorting to similar "cheating" solutions like using an X-ray, how could you tell which is which?
You should be able to tell easily just by rotating them in your hands. They'll have different rotational inertias. The solid one will be easier to start and stop rotating, because the mass in the center is not experiencing as much linear acceleration as the mass in the shell.

On "real" (unbended space) FTL and time travel, also known as tachyons: What does that even mean?
So I'm on Earth and you're in your spaceship traveling away from Earth. As you go faster, time passes more slowly for you. If you (somehow, impossibly) are traveling at light speed, time is not passing for you at all; you reach your destination at the same time you left, as far as you're concerned. If you exceed c ("even more impossible"), time is passing in reverse for you. You arrive, then you travel, then you leave. By this method you could carry information from the future into the past. Even a simple tachyon beam would carry information from its destination to its source, rather than vice-versa. This leads to easy paradox creation.

#### Pinkamena

##### Stuck in a vortex of sexy horses
RedRockRun said:
What's up with quarks and their "flavors". What is the difference between them, and do they have anything to do with their names?
Their "flavors" are names that discern them. They are the same "species" of particles, but each are their own particle with their own flavor/name and details. Nothing special. The biggest difference between the 6 are their mass, with the heaviest (the "top" quark) being 35 000 times heavier than the lightest (the "up" quark). The 6 types of quarks (and their 6 antimatter equivalent) can combine in a host of different combinations to produce new particles. Most of these particles are very zhort-lived, and decays into lighter particles in nanoseconds or less. The well-known Proton and Neutron, which the atom nucleus consist of, are made of two different combinations of quarks. These two are the only stable combinations of quarks that exists. The names are historical, and don't relate to any detail or behaviour of the particle.

#### Slenn

##### Cosplaying Nuclear Physicist
retsupurae yahtsee said:
It said that the treatment was used on someone whose legs and brain were poorly connected.
Well, in terms of the dangers, it's pretty natural to be worried about such a thing. I'm not entirely sure how it works. But I can surmise it has to do with creating electronics that transmit signals at the same voltage and speed as a normal neuron. My guess is that it does make the head transplant easier.

Dalisclock said:
Do you play Kerbal Space Program or are you familiar with it? If so, do you feel it's reasonably accurate as far as flight physics are concerned?

On the other side of the coin, does the use of Quantum Physics and Time Travel as a substitute for magic in some sci-fi stories, such as Bioshock: Infinite, annoy you? Or in situations like that do you just roll with it and judge the work on it's other merits?

I worked with Nuclear Power for several years and got my degree in it, so some depictions of Nuclear Power/Reactors/Weapons annoy me and others I'll let slide depending on how much I like the work overall.
I do not play Kerbal Space Program. I'm somewhat familiar with it, but not enough to say anything about it in terms of its accuracy.

I suppose it's a little bothersome. This question has been asked in various ways throughout this thread. As long as the authors aren't spitting out science jargon to make the show/game/movie/book sound smarter, they're fine. Otherwise, it's best to not make a fool of yourself.

#### Slenn

##### Cosplaying Nuclear Physicist
Batou667 said:
Slenn said:
My guess is that only at some point in the middle of the path. He will have occupied the same point at the same time of day, but on two different days.
Are you sure? Is there any possibility he could "miss" himself? Remember his rates of ascent and descent are different, and although he sets off at the same time both days, his arrival times are different.

OK, here's another one which IIRC is an undergrad interview question. You have two identical spheres in front of you. They both have a diameter of six inches and each weigh two pounds exactly. You are told that one is solid and the other is hollow. Without breaking them open or resorting to similar "cheating" solutions like using an X-ray, how could you tell which is which?
Then I'm not understanding the riddle. Hint perhaps.

RE: Next riddle. I would roll the spheres down a hill. A hollow sphere and a solid sphere of the same mass and radius will have different moments of inertia for rotation. The hollow sphere will have all its mass in a shell and will have a slower roll.

#### Slenn

##### Cosplaying Nuclear Physicist
RedRockRun said:
What's up with quarks and their "flavors". What is the difference between them, and do they have anything to do with their names?
Pinkamena said:
Their "flavors" are names that discern them. They are the same "species" of particles, but each are their own particle with their own flavor/name and details. Nothing special. The biggest difference between the 6 are their mass, with the heaviest (the "top" quark) being 35 000 times heavier than the lightest (the "up" quark). The 6 types of quarks (and their 6 antimatter equivalent) can combine in a host of different combinations to produce new particles. Most of these particles are very zhort-lived, and decays into lighter particles in nanoseconds or less. The well-known Proton and Neutron, which the atom nucleus consist of, are made of two different combinations of quarks. These two are the only stable combinations of quarks that exists. The names are historical, and don't relate to any detail or behaviour of the particle.
Yes and no.

Up and down quarks have +2/3 and -1/3 electron charge and some small mass. These are the only ones with no other particular qualities to them.

Strange quarks have a property called "strangeness". This property was first observed in Kaons, a particle with non-zero strangeness which made it have a peculiarly long decay time.

Charm quarks, Top quarks, and Bottom quarks are similar. And lots of baryons out there have properties called "charmness", "topness", and "bottomness". Not even kidding about that.

#### Slenn

##### Cosplaying Nuclear Physicist
Lightknight said:
A ship is certainly the easiest way to think of matter traveling at that speeds and increasing in velocity. Though the current arguments revolve around any matter as it reaches these speeds. All I really mean is that it isn't accelerating so rapidly as to be destroy itself by the rate of acceleration. In a frictionless vacuum the only forces one should really encounter is whatever the force accelerating them is as long as they don't encounter objects in said space (either directly or near enough as to constitute significant gravitational forces high enough to consider as a vector/vectors in the equation).
In that case, you can accelerate the ship at 1 g up to relativistic speeds, and it'll be fine. This would be nice for long term travel as well since the distances between stellar objects are quite large. Another thing, I know you mentioned something about "moving really slow." But we're not seeing objects move slower due to special relativity. What's happening is the time dilation. People on the ship will have their clocks tick normally, while the people on Earth appear to have theirs tick slowly. Strictly speaking, we like to refer to these things as events.

I'm challenging the notion of requiring a bubble for light speeds. So I'm inquiring of a scenario where a ship increases its velocity gradually enough up to the speed of light within a vacuum. I'm sure that inside a magical bubble everything would remain intact since the mythical nature of this idea would inherently mean that it's almost like the universe would be moving past the ship relative to the ship rather than the ship moving through the universe where forces enacted on it are concerned. Warp fields are fun to think about, especially with recent announcements regarding the EmDrive, but I really don't think they're as much as a given as we'd like to think they are.
Well, to be perfectly frank, I can't answer what will happen to the flashlight if I don't make any assumptions on the nature of the FTL drive. But I don't think there's be anything special that would happen to the beam of light. The flashlight is in the same frame of reference as the people in the ship. If people can move around normally, then I would assume that the light also moves normally.

Keep in mind that I'm fully aware that the ball falls at the same rate either way just as a bullet if shot from the same point it would otherwise have been dropped ends up hitting the ground at the same time if unobstructed in its journey across a level plane. I'm also aware of the differences between the observer in motion compared to the stationary observer on the ball. Looking back on my quote I'm unsure what I was trying to say about wind resistance. I imagine that was an incomplete thought where I was trying to indicate that my own personal experiences have been watch the ball fall backwards rather than straight down due to air resistance that makes the reduction in momentum once unsupported/unpowered by the vehicle more noticeable. But that is my best guess as to what I meant there.

What I'm saying is that inside the car the ball is relatively unaffected by the speeds the vehicle is traveling. I can toss the ball up and it does not start to loose momentum in the same way that someone with dice on their rear view mirror do not witness it flying backwards as the car speeds forward unless an external force like wind acts on it.

So hypothetically when inside a vehicle traveling at the speed of light you should not feel as though you are moving at the speed of light just as we do not feel like the surface of the earth is moving at 1,000 miles per hour or that the earth itself is moving at 67,000 miles per hour. So at light speeds in a vacuum, what force is causing the traveler to then feel like they're going that fast if we do not experience that already? So you should be able to throw a ball and it get to the other side or shine a flashlight and illuminate the far side.
There is no force that gives us a feel of going fast once going at light speed. In the same way if you were on the highway at 75 mph but not accelerating.

I just don't get how we have a universe where instantaneous teleportation of information exists (quantum entanglement) but somehow traveling at an ultra fast rate of speed means that you're traveling more than instantaneously when light itself isn't anything close to instantaneous. I mean, the claim here would imply that if light traveled only 1 unit of distance faster per second that it would then be traveling backwards in time, right? Yet we measure distant objects in light years which should discredit the notion that they are on the cusp of reaching destinations before they were sent out. Right? There has to be a trick in what people mean by "time travel". Surely every object in space has its own relative "now" and no matter how fast we travel between them we can't change the object's "now" in relative to our "now". We can only make it appear like we're altering it when we aren't really. Also, at no point would we be able to look in any direction and see our future selves, only our past.
By "ultra fast rates of speed", I mean faster than light speeds. The time where science currently holds that if we could travel that fast we would be traveling through time.
Faster than light does not necessarily mean instantaneous then, if I understand your definition. But the term "more than instantaneously" is vague and confusing, which is why I don't understand your frustration.

But to answer your questions. I'm not entirely sure what would happen if I were to travel at superluminal speeds. But to observers it would be impossible to see that object coming in, because their own image would arrive after the object had past us.

Measuring distances in terms of lightyears doesn't mean anything in terms of something reaching a destination before it's sent out. What we're seeing from an object 10,000 lightyears away is the light from that object as it existed 10,000 years ago.

Yes, light waves are always on the cusp of traveling faster than light since it is itself traveling exactly the speed of light. 1 more inch per second and it should hypothetically be crossing the time travel threshold that science says we'd be crossing were we to do so.

So if it is that very close to going so fast that it could arrive at its destination before it leaves, why does it take so much time to get places even though I know those distances are vast. In fact, it is said that a photon does not experience any time at all. But it takes so long that we can even measure it on earth. Do we really hold that had light been even one iota faster in a vacuum that it would all be time traveling? Hmm... I wonder how that would look. Would we still have light or would everything be black due to light having arrived before it left ergo what we would be looking at would be a time before the light left, ergo darkness. Weird.
We don't know why the speed of light is objective. Our universe is huge, light has a finite speed.

But I think you're getting a little ahead of yourself. Any object that has mass cannot go faster than the speed of light. Any object that is massless can only go at the speed of light in every reference frame and no other speed. We don't know what are the requirements on what an object would need to have faster than light travel. Assuming that it's "close" to going faster than the speed of light may be a little bit of a stretch. I would have to say it would require something of non-zero but complex mass.

Sure, but for us to perceive them that means that photons from each and every one of those stars we see at night is hitting our eyes, right? If I move over four steps I presume that I am then being hit by different protons from the same stars and the longer I stand in one place I'm seeing however many subsequent photons hitting my eyes, right?

Now the stars emitting these are shooting these photons out and way from themselves in literally all directions. As far as I know, this means that as long as nothing is between me and the source of light, then I can travel anywhere and still see it as long as light has had enough time to travel to that location. So the only inevitable conclusion is that there are photons packed in every square inch in all directions, right? How do these photons not interact with one another since I can therefore assume that there are photons from every other source of light. I mean, even stars that are too faint for our human eyes to make out are still hitting us with photons as evidenced by how many stars the Hubble telescope can see that aren't detectible by the human eye from earth. So why isn't this more evidence?

Though, we don't actually see light unless a photon hits our eyes, so that's why the entirety of space isn't white. But in every square inch of space the number of present photons should be astounding, right? From what I've read even the dimmest star we can still see is packing 100,000 photons per in^2 per second. From something like the sun its 2 x 10^18 photons per in^2 per second. Are we unable to see distant stars during the day because the environment is so permeated by photons from the sun both directly from the source and also bounced off of so many things to our eyes? (Though astronauts can't see stars during the day either despite the surrounding area not being dark due to a lack of things for the sun's photons to bounce off of)

So there must be a maximum saturation point of photons that our sun is capable of meeting enough to prevent viewing lesser light sources... right? I wonder if the stars we can see are actually responsible for blotting out stars we can't see. Maybe the reduction of power actually is interaction between photons... maybe not.
Photons rarely ever do overlap. It takes a lot of precision for even in a lab setting to get two photons to collide and interact. The density of light in the void is much much much lower than the density of light that we see from the sun during the day. In a region of space, sure the amount of light created by the stars is a lot, and there's a lot of stars. But the intensity of light diminishes as the inverse square of the distance from the source. 100,000 photons per square inch is not a lot, despite the number sounding huge. That many photons yields something on the order of hundredth of a trillionth of a Joule of energy. And you've answered your own question. We can't see the stars in the night time because their intensity isn't anything close to the sun, and our atmosphere scatters light.

I hope this helps!

#### Slenn

##### Cosplaying Nuclear Physicist
Pinkamena said:
Slenn said:
Hello there!
*snip*
I laugh at your puny 4 semesters. Glance upon my 8 semesters and despair.
Also, hi. Postgrad in particle physics here. Gonna hija- I mean help out here because I love answering physics questions.
That's fine with me as long as I also get to answer. Because I like to explain things, and I want to get a shot at explaining things.

Hypertion said:
do you think any normal material, metal or otherwise can survive getting to 99.9999% of lightspeed? specifically, would in those situations, approaching the speed of light have a effect on matter similar to when objects get close to the speed of sound. IE effectively hitting a increasingly high energy wave in front of the object comprised of effectively compressed light.
There are hypothetical scenarios where a ship accelerates to 1 g to significant fractions of the speed of light. That would be ideal for space travel since the distances between objects are quite large.

As the pink one has pointed out, light has the same speed in every frame of reference. What might change is the frequency of the light, which is called the doppler shift. A ship approaching a light that's normally green, will view it as blue.

#### RedRockRun

##### sneaky sneaky
Slenn said:
Yes and no.

Up and down quarks have +2/3 and -1/3 electron charge and some small mass. These are the only ones with no other particular qualities to them.

Strange quarks have a property called "strangeness". This property was first observed in Kaons, a particle with non-zero strangeness which made it have a peculiarly long decay time.

Charm quarks, Top quarks, and Bottom quarks are similar. And lots of baryons out there have properties called "charmness", "topness", and "bottomness". Not even kidding about that.
I don't know much about physics, but quarks feel so odd by comparison. Is there any reason why the six different quarks are referred to as "Flavors"? So the only difference is their mass? When I first saw their names, I assumed it was based on the way they moved or interacted - almost like a throwback to Platonic elements.

What did you mean by, "+2/3 and -1/3 electron charge"?

Also, could you give a quick rundown of the important subatomic particles but especially the less-known elementary particles such as the Kaons you mentioned. Would Kaons be considered elementary since they're made up of quarks?

What are quarks made of as well?

Sorry for all the questions. I must sound like an annoying child!

#### Slenn

##### Cosplaying Nuclear Physicist
RedRockRun said:
I don't know much about physics, but quarks feel so odd by comparison. Is there any reason why the six different quarks are referred to as "Flavors"? So the only difference is their mass? When I first saw their names, I assumed it was based on the way they moved or interacted - almost like a throwback to Platonic elements.

What did you mean by, "+2/3 and -1/3 electron charge"?

Also, could you give a quick rundown of the important subatomic particles but especially the less-known elementary particles such as the Kaons you mentioned. Would Kaons be considered elementary since they're made up of quarks?

What are quarks made of as well?

Sorry for all the questions. I must sound like an annoying child!
Your questions are fine! Don't sweat it.

The "flavors" of quarks come important when you get into the weak nuclear force. The weak nuclear force has the ability to change the flavor of quarks by using one of its intermediating particles. In some nuclear collisions, a neutron will convert into a proton because one of its down quarks got changed into an up quark. You are right, the name "flavor" is an abstract title that particle physicists use to describe the nature of the particle. Their names come from their discoverers, and were discovered at various points throughout the 20th century. Their masses are different, but remember what I said earlier: That they each have a peculiar quality to them that's found in composite particles like "strangeness" in Kaons.

The 2/3 and -1/3 electron charge refers to how much of a fraction of electric charge it has in comparison to the electron's charge.

Elementary means that the particle cannot be broken up any further. So a Kaon, since it's made up of more than one quark, isn't an elementary particle.
The elementary particles are categorized as such:
Quarks : Up, Down, Charm, Strange, Top, Bottom.
Leptons : Electron, Muon, Tau.
Neutrinos : Electron neutrino, Muon neutrino, Tau neutrino.
Bosons : Photon, W+, W-, Z0, Gluon, Higgs.

If you're interested, I'll be happy to go further into how they're categorized as such.

As for what quarks are made of, we don't know. All we know is that you can't find a quark by itself.

#### C_sector

##### New member
I know that it takes millions of light years for light to travel from other stars to our earth. So, does it mean that:

1)what we actually see in the night sky is actually millions of years old? and....

2)Is it possible that the stars that we are seeing may no longer be actually there?

3) Finally, is it possible that there are celestial bodies in space that can be seen under normal circumstances but we havn't yet because its light hasnt reached our planet yet?

4) In a way..... would you agree that what we see is like an old print or photo of the universe that happens to be several million years old?

#### HanFyren

##### New member
Two questions in the sci-fi realm:

1. Is it possible that dark matter is matter in parallel dimensions interacting with ours but only through gravity?

2. Could you theoretically make an handwavium generator that disrupts the Higgs-field disabling its ability to interact with your mass. In effect make an inertial dampener. And if so would the removal of internal gravity have any effect on your body even though gravity is so mindbogglingly weak?

#### RUINER ACTUAL

##### New member
I wounder if I can use you as a source...

How many cosmological decades have passed? and How many will the Universe when it 'dies'?

#### Slenn

##### Cosplaying Nuclear Physicist
C_sector said:
I know that it takes millions of light years for light to travel from other stars to our earth. So, does it mean that:

1)what we actually see in the night sky is actually millions of years old? and....

2)Is it possible that the stars that we are seeing may no longer be actually there?

3) Finally, is it possible that there are celestial bodies in space that can be seen under normal circumstances but we haven't yet because its light hasn't reached our planet yet?

4) In a way..... would you agree that what we see is like an old print or photo of the universe that happens to be several million years old?
1. Yes. The deeper into space we look, the deeper into the past we're viewing. It takes light one second to travel from the moon. So what we're seeing the moon as it was 1 second ago.

2. Yes but depends on what stars. Star lifetimes can be 800,000,000 years at the shortest. Any object on the order of 100's of millions of lightyears is pretty far away, but it's not an unreasonable distance.

3. Yes, most definitely.

4. In some sense, yes. Telescopes are "time machines".