x
Click to expand

/science/ board

Comments(4685):

[ 4685 comments ]
What do you think? Give us your opinion. Anonymous comments allowed.
User avatar #4805 - theism (07/30/2015) [-]
Is it possible that light doesn't have the maximum velocity of anything but rather the maximum momentum?
User avatar #4813 to #4805 - subtard (15 hours ago) [-]
E^2 = (pc)^2 + (mc^2)^2
The (pc)^2 term only ever matters when approaching the speed of light, which is makes the rest boil down to E=mc^2 where m=mass at rest. However photons have no mass at rest which means E = pc. P comes from relativistic momentum which is equal to Planck's constant divided by the light's wavelength. The average visible light has somewhere around 10^-27 kg*m/s momentum from this.

Compare that to some example values from this site www.batesville.k12.in.us/physics/PhyNet/Mechanics/Relativity/relativistic_momentum.html to show that light really has negligible momentum.
#4808 to #4805 - anon (18 hours ago) [-]
Light has velocity because it is not a solid matter. Light is light, simply put, and it cannot gain or lose momentum. Indeed it has no momentum. The velocity at which rays of light move is affected only by the environment in which it moves. Although it can be manipulated to move slower or faster through certain factors and variables, light has no momentum.
User avatar #4809 to #4808 - theism (18 hours ago) [-]
Photons have both mass and velocity, therefore momentum.
#4811 to #4809 - anon (18 hours ago) [-]
Photons actually do not have mass.
User avatar #4803 - theism (07/28/2015) [-]
What environmental conditions would reduce the fire activity of a high oxygen atmosphere? The best I can think of is atmospheric moisture,
#4806 to #4803 - anon (18 hours ago) [-]
Atmospheric pressure.
User avatar #4807 to #4806 - theism (18 hours ago) [-]
High or low pressure?
#4810 to #4807 - anon (18 hours ago) [-]
Exactly. High pressure would cause a reaction to be more volatile in most scenarios. There's a few simple things that affect the behavior of a chemical reaction. 1. Agitation (e.g. in a liquid mixture, stirring it faster to help disolve/mix, or when you push around hot coals in a dying fire to start the flames again) 2. Pressure (as mentioned) and 3. Temperature.
User avatar #4800 - theism (07/25/2015) [-]
What does a t-rex even do with it's arms? They aren't much use for claws or manipulation so whats the point?
#4797 - anon (07/23/2015) [-]
So this is labeled as "Wavellite on matrix"
What does it mean when they say "on matrix"? I looked it up but it still didn't make sense to me. Can someone help?
User avatar #4794 - luigipimp (07/20/2015) [-]
i heard if time stopped, that you would be burned up by the friction of air molecules but wouldnt that mean you wouldnt be able to breathe since the air would stop flowing and not be able to move since the air molecules wouldnt move out of the way from displacement?
User avatar #4796 to #4794 - nought (07/23/2015) [-]
Time can't stop
If it could be stopped in an "instant" nothing would happen in the instant?
User avatar #4791 - ogcj (07/19/2015) [-]
Why climate change is a hoax
www.youtube.com/watch?v=7r8vZ0uxdGw
User avatar #4795 to #4791 - nought (07/23/2015) [-]
Not even worth opening the link
This is science not conspiracy
User avatar #4798 to #4795 - ogcj (07/23/2015) [-]
It's not science, Especially since they recently had to cancel an expedition in the antarctic that was going to study climate change because there was too much ice. One of the scientists on board said that he hasn't seen that many ice in over 20 years.
User avatar #4799 to #4798 - nought (07/23/2015) [-]
"wow there's so much ice here omg everyone look around it's all fake call if off boys" :^)
User avatar #4787 - ravenpt (07/18/2015) [-]
Hey. I need a little help with some hypothesis test that myself and a teacher of mine at uni disagree at. So here it goes:

A school director wants to start classes at saturday, but he will only do so if 80% of the students are willing to attend. With a degree of confidence of 95%, should the director start the classes at saturday?

Students that said they will attend: 288 of 400 (wich will make 0.72)

So I said that the director shouldn't start them because:

H0: p<=0.8 (The data indicates that there won't be enough students)
H1: p>0.8 (The data indicates that at least 80% of students will attend)

Since the outcome will be negative (0.72-0.8=-0.08) there is no chance the result can be positive, so H0 is accepted.

While she did the following:

H0: p=>0.8 (Students will attend the class)
H1: p < 0.8 (Students will not attend the class)

And in this one, H0 is also passed. But this last test only demonstrates that there isn't 95% of certainty that less than 80% will attend the class right? Am I going nuts?
#4792 to #4787 - smudgiemuffins (07/19/2015) [-]
Quick note, null hypotheses cannot be set up like x<=n. They must be in the form x=n. The only valid operator for a null hypothesis is an equal sign. Also, your alternative hypothesis should be testing for whether or not p is actually lower than 0.8.

Your phrasing of the question was a tad ambiguous. Is the intent that the teacher has exactly 400 students, and 288 said they will definitely comes? That doesn't imply that the other 112 wont. Nor can we make a statement about them because the 288 who did answer do not in any way represent the 112 who didn't. If I were talking about this on a statistics test, I'd call it "response bias" to please the teacher and just say this is a bad survey.

Now, if the teacher has, say, ~4000 students and 400 random students responded. 288 said yes, 112 said no. Then it's quite easy. You've got a large, random sample thus the central limit theorem holds and z-procedures are valid. This yields a confidence interval of (.676, .764) at 95% confidence. Or in colloquial terms, we're pretty damn sure there are not a proportion of .8 students going to attend.

Or, what is in my opinion the better way to approach this test but less intuitive depending on what kind of stats class you're taking. A 95% percent confidence interval implies a level of significance at 5%. A 1-proportion z-test yields a p-value(not proportion, just to be clear) of 3.17*(10^-5). Meaning, by the level of significance and really any reasonable level of significance the H0 that p=0.8 should be rejected.
0
#4778 - mrskulldude has deleted their comment [-]
User avatar #4789 to #4778 - djequalizee (07/19/2015) [-]
Put the batteries in
User avatar #4782 to #4778 - nimba (07/17/2015) [-]
put it in the toaster
User avatar #4771 - aliennova (07/16/2015) [-]
I recently came up with a hypothesis about gravity. I have a lot of problems with our current theory on gravity as the only thing it explains is the more mass something has, the more gravity it has. Nothing else What if gravity is just another dimension? Of course I ran into the problem "Well, then what force pushes/pulls objects in that dimension if not gravity?"

This is really hard to explain so I'm going to start a comment chain. This is just something I thought of, and I do not believe it to be correct. I would love to hear all your hypothesis on what gravity exactly is!
#4793 to #4771 - smudgiemuffins (07/19/2015) [-]
I'm quite confused as to what you're trying to get at. Dimensions are useful mathematical objects meant to describe objects with a quality of, for lack of a better word, independence. Take the classical physics example. If you drop a ball and throw a ball sideways, they still and at the same time. The ball's x-component velocities have nothing to do with their y's. And this conflates dimensions as things they can only refer to space and time. Consider a function like f(x,y) = xy. X and Y can both be thought of as dimensions of function f.

I like the informal definition of dimensions wikipedia gives. It's the least number of coordinates to specify any point within it. Take the function f I said earlier, you require two numbers to specify any value f can take.

There is where it is useful to differentiate kinematics and dynamics. I'll loosely say discussion of dimension in this way is more in the realm of kinematics, which is the study of motion without consideration of the causes. I say this because the definition of a space within which there are dimensions simply defines a set which some function can take. Gravity, a consideration in dynamics, more describes the cause of force. It isn't itself a motion but rather a cause of motion.

I feel like I can be a bit more concise if you'll allow a more mathematical view. When we say dimensions(the spatial ones and time) we usually mean something like a function like f(x,y,z,t) where f defines some physical quantity with relationship the standard "motion dimensions." Either f or one of it's derivatives is what describes something like gravity, a cause or description of the cause of motion rather than a dimension of motion itself. Things like mass or charge often scale functions like f but can also be functions themselves.
User avatar #4779 to #4771 - nought (07/17/2015) [-]
string theory actually hypothesizes gravity as a result of strings in more dimensions, but not a dimension itself. Gravity is a consequence of the geometry of 4D spacetime. Unofrtunately, your hypothesis has no evidence, while there is evidence that gravity is the warping of spacetime
User avatar #4783 to #4779 - nimba (07/17/2015) [-]
>posting about string theory on a science board

shit's untestable dude, take that over to /religion/ where it belongs
User avatar #4788 to #4783 - nought (07/18/2015) [-]
lol
#4772 to #4771 - aliennova (07/16/2015) [-]
Okay so before I start, I should explain how I imagine extra dimensions.
You obviously can't imagine/perceive a spacial I say spacial because I have another personal hypothesis that time is something like another dimension, I might explain this one later. dimension. So Instead I imagine that the world is flat, 2 dimensional, but I'm still able to perceive the third dimension. Paint skills novice
#4773 to #4772 - aliennova (07/16/2015) [-]
If we were too view 2D Earth from space and only perceive in 2D it would look like this.

Note that you wouldn't even see a line. Just something blocking light from reaching your eyes.
#4774 to #4773 - aliennova (07/16/2015) [-]
So, lets re-ask the question. What exactly is gravity? Well in flat world, would the third dimension be gravity?
User avatar #4777 to #4774 - Zaxplab (07/16/2015) [-]
But... The first dimension is a point. Nothing else. Just an infinitely small, almost indefinable point. The second dimension consists of infinite points, formed together to create planes. The third dimension is infinite amounts of planes, which creates.... dimension.

I think the third dimension would be Time to the second dimension, just as the fourth dimension is Time to us.
User avatar #4780 to #4777 - nought (07/17/2015) [-]
dimensions aren't ordered....3 space and 1 time dimensions are always linked together
User avatar #4775 to #4774 - aliennova (07/16/2015) [-]
Wrong. What would be pulling everything down in the zed axis if not gravity?

This is a very poorly explained version of my hypothesis, but I hope it struck the point I was trying to reach.
User avatar #4776 to #4775 - aliennova (07/16/2015) [-]
We experience gravity every single second of our lives. We think we know how it works, but we honestly don't have the slightest clue to what it actually is. Any one else have any hypothesis on gravity?
User avatar #4769 - luigipimp (07/15/2015) [-]
could walking around a lot all day from work make kind of a soft bump in between my big and second toe and be achey. looks kind of like a vein without the blue
User avatar #4781 to #4769 - nought (07/17/2015) [-]
if you have shit shoes maybe
User avatar #4762 - luigipimp (07/11/2015) [-]
how can primitive tools build all those ancient stone things if it would take a lot of time to build them with modern technology
User avatar #4766 to #4762 - rainbowrush ONLINE (07/13/2015) [-]
They brought the rocks using the river for fast transport then simply paid people to roll them up.

I am unsure how they lifted the rocks weighing more than a ton, though. I suspect they used sand or some sort of crane mechanic.
User avatar #4765 to #4762 - nought (07/13/2015) [-]
there are many publications and research papers on techniques for building structures like pyramids, large obelisks, etc. A google search for a specific "stone thing" will do well
#4761 - jettom ONLINE (07/11/2015) [-]
War is science!

I need more webms of war and missiles and explosions. Preferably by slavs.
User avatar #4744 - entarasu ONLINE (07/10/2015) [-]
you are my last hope guys pls can you help me with this shitty problem
Let A and B two components of a binary system whose neidealitate liquid phase is characterized by the equation
Scatchard Hildebrandt:
GE = KxAxB where K = 5820J / mol
It is a constant independent of temperature. An amount of 7 mol of component B is added slowly under continuous stirring, over 1 mol of component A, both at the temperature T0. Determine the minimum temperature value T0 which remains single-phase multi-system throughout the experiment. Heat capacity of componenμilor are
CP, CP A = B = 30J / mol K
And, under experimental conditions, heat exchanges between
system and the external environment can neglected
User avatar #4763 to #4744 - zonetransferrer (07/11/2015) [-]
write it down to paper and post a photo of it. it is easier to read and write than describing it in word processor.
User avatar #4745 to #4744 - nought (07/11/2015) [-]
ok I could probably help you if you clarified K (constant or Kelvin) and you didn't user german that's what it looks like
User avatar #4747 to #4745 - entarasu ONLINE (07/11/2015) [-]
kelvin
User avatar #4750 to #4747 - nought (07/11/2015) [-]
also idk what GE is
User avatar #4749 to #4747 - nought (07/11/2015) [-]
but you said K = 5820 J/mol...?
User avatar #4752 to #4749 - entarasu ONLINE (07/11/2015) [-]
sorry thats a constant and GE its short scatchart ecuation with something osculatory something
User avatar #4753 to #4752 - nought (07/11/2015) [-]
ok that did not help
if this is chemsitry the only thing I can say is q = m c delta T
User avatar #4756 to #4753 - entarasu ONLINE (07/11/2015) [-]
whats that with q and m and c?
User avatar #4757 to #4756 - nought (07/11/2015) [-]
i don't think that equation is right, but it is q = heat energy, m = mass, c = specific heat, delta t = temperature change

User avatar #4758 to #4757 - entarasu ONLINE (07/11/2015) [-]
the system is not ideal defined by that equation
that equation is deduced or something
User avatar #4759 to #4758 - nought (07/11/2015) [-]
ok I cannot help you then
User avatar #4760 to #4759 - entarasu ONLINE (07/11/2015) [-]
well he took 3 hours to solve a test that we should do in an hour so dont worry
User avatar #4755 to #4753 - entarasu ONLINE (07/11/2015) [-]
anyway its a shit problem made by a shit teacher
User avatar #4754 to #4753 - entarasu ONLINE (07/11/2015) [-]
its phyzics chemestry
User avatar #4743 - rainbowrush ONLINE (07/10/2015) [-]
If there are infinite realities, why haven't a different me found a way to cross from reality to reality to give me a pink yoyo?

Does time exist other than a form of measurement; does the past and future exist other than words to describe what was and what will be?
User avatar #4790 to #4743 - djequalizee (07/19/2015) [-]
infinite realities =/= infinite different realities. They could all be the exact same
User avatar #4768 to #4743 - supahsayin (07/15/2015) [-]
If there are infinite realities, you just might be in one that ends up not having anyone cross dimensions while you're alive.
User avatar #4748 to #4743 - nought (07/11/2015) [-]
infinite realities is just a theory with no evidence.
according to some documentary I watched the past and future both exist in terms of physical equations. idk more than that though
User avatar #4740 - alltimetens (07/09/2015) [-]
I keep trying to explain to my friend that astral projections and the psychic staring effect are not real.

What can I do to convince her?
User avatar #4746 to #4740 - nought (07/11/2015) [-]
you can't convince some people
User avatar #4736 - mindlessdubs (07/07/2015) [-]
Teach me cool science shit, I want knowledge.
User avatar #4784 to #4736 - nimba (07/17/2015) [-]
There's a newly discovered type of chemical bonding that nobody wants to talk about because it's weird and confuses everybody
User avatar #4770 to #4736 - dotheherpaderp ONLINE (07/16/2015) [-]
Getting chickenpox as a child doesn't make you immune to it for life. In fact, it'll make you more susceptible to shingles in adulthood.

This is why doing those "chickenpox parties" to get one's kids deliberately infected has not been and is still not a good idea. A vaccine already exists.
#4737 to #4736 - raeptiemx (07/08/2015) [-]
so...what do you want to learn.
I got some science stuff real cheap kiddo.
I got chemistry for 20 bucks a pop and biochemistry for 15.
Genetics, Anatomy and Physiology are going to cost you extra
User avatar #4741 to #4739 - raeptiemx (07/09/2015) [-]
did you know that um if you don't get Vit K you can bleed to death?
That's because Vit K is responsible for adding glutamate to various clotting factors without which they'd suck dick and you'd die from any kind of cut(

Hand over 30 bucks now or I'll shoot you with some heparin and then stab you.
You'll bleed faster than my average sex time with my wife
User avatar #4732 - pokemonstheshiz (07/07/2015) [-]
Assuming multiple dimensions exist and it is possible to traverse between them, what methods would you first use to try and get there?
User avatar #4733 to #4732 - sugoi ONLINE (07/07/2015) [-]
Shooting a lot of anti-matter in the same spot or jumping in a black hole.
I will probably die with either methods but hey that's science for you.
User avatar #4734 to #4733 - pokemonstheshiz (07/07/2015) [-]
I think provided a wormhole can be traveled through, finding or creating an instance where two wormholes intersect might be a good bet
User avatar #4735 to #4734 - sugoi ONLINE (07/07/2015) [-]
Yeah that's what the anti-matter and black hole was for.
Anti-matter hopefully tears the universe apart making a worm hole or a black hole could potentially already be a worm hole.

Either way I am no science man and most likely a complete retard in regards to this subject.
#4728 - zonetransferrer (07/06/2015) [-]
can anyone help me with this?

From mountain lake, which surface lies 100m above hydroelectric plant, is going to have new metal pipeline 1900m in a way that overpressure at plant has to be atleast 0.588 MPa and volume of water flowing to be 4 m^3/min. What diameter should pipeline have, assuming that equivalent lenght of pipeline with local resistances is equal to 10% of real lenght of pipeline. T= 10°C. abrasiveness is 0.2mm

mostly i am interested in how unit conversion in step 1 worked to end up m^2/s^2
for step 4 i am going to add another comment
User avatar #4738 to #4728 - xsnowshark (07/09/2015) [-]
What class is this for? Fluid dynamics?
User avatar #4742 to #4738 - zonetransferrer (07/09/2015) [-]
process Engineering 1, part of it is about bilantion , fluid dynamics (more like fluid flow in pipelines), and another is about transferring heat.
#4729 to #4728 - zonetransferrer (07/06/2015) [-]
for step 4 i have used this diagram but i am not sure if i read it right

So the final question is, did i write it right and can diameter of that pipeline be 2.22 mm?
Sorry for bad translation and i later realised that you may use dot not comma for decimal position

User avatar #4727 - zonetransferrer (07/06/2015) [-]
hypotetical situation.

you are in a room with perfect blank white walls there is just you and you have 10g of maryjane. how would you got high from it? you have absolutely nothing but the grass, room is empty, there is light in the room but no light source,( just assume that there is light.)

I already tough of stuffing it up my ass and let colon to absorb it. any ideas?
User avatar #4802 to #4727 - theism (07/28/2015) [-]
If you could work out a way to get it to about three or four hundred degrees you'd decarb it and then you could eat it. Unfortunately I don't think the human body can generate that kind of heat.
User avatar #4730 to #4727 - fornowjr (07/06/2015) [-]
No possible way to get high without heating it. Absorbing it through your anus or eating will not get you high.
[ 4685 comments ]
Leave a comment
 Friends (0)